Dissertations / Theses on the topic 'Gold nanoparticles'

The amalgamation of nanotechnology and biology has led to the development ofnew types of hybrid materials that are expected to produce major advances in areas such as materials science, therapeutics and diagnostics. One of the most promising developments is the use ofnanoparticles (NPs) as labels for the detection of analytes in biological assays. The aim of this research project was to prepare gold nanoparticle (GNP) labels for use in such assays. In chapter 1, the optical properties and the use of GNPs in homogeneous and heterogeneous colorimetric assays are reviewed. In chapter 2 a simple conjugation method is introduced that not only allows almost any biological molecule or hapten to be attached to GNPs but also allows the user to control or vary the mean number of molecules per particle. In this method a high molecular weight aminodextran polymer is functionalized with the molecule of choice and chemical attachment groups that are used to covalently anchor the polymer to the GNPs. This method was used to conjugate biotin and 1125 functionalized dextrans to GNPs. These functionalized dextrans were then used to investigate the conjugation procedure in more_detail. Results from GNP titrations and microbead assays demonstrate that the minimum amount of functionalized dextran required to prevent salt-induced flocculation ofthe GNPs (equivalence point) is the amount required to coat all of the GNPs and at this point there is no free functionalized dextran in solution. In chapter 3 the described method was used to conjugate different numbers DNP haptens to GNPs and then these labels were used in non-traditional reagent-limited lateral flow immunoassays. The number of molecules per GNP is varied by simply adjusting the stoichiometry of reagents in the dextran functionalization reaction. Controlling the number of molecules per particle can have important consequences on the sensitivity of a biological assay. Results showed that when the number of DNP molecules per particle decreased, there was an increase in the sensitivity of the assay. Furthermore when the results from these immunoassays were compared to those obtained from traditional reagent-limited lateral flow immunoassays, the nontraditional format proved to be over 50 % more sensitive. In chapter 4 the conjugation method was used to attach oligonucleotides to GNPs for use in a nucleic acids lateral flow (NALF) device. Although NALF devices are available commercially, detection is usually achieved with the use of antibodies or haptens which can be both problematic and expensive. In addition, many of these devices have issues with sensitivity and are often interfaced with complicated target amplification / purification protocols. In chapter 4 an antibody / hapten independent NALF device is described that can be used to detect the un-purified products from a simple polymerase chain reaction (PCR) amplification protocol. Using the developed NALF device it was possible to detect specific amplification products corresponding to ~1 attomole oftemplate molecules with the unaided eye.

Nanoelectrochemistry explores the differences in chemical behaviour at the nanoscale as compared to the macro-scale. This thesis is concerned with nanoelectrochemistry and aims to develop and apply novel experiments for the unambiguous identification of changed electrode kinetics at the nanoscale. This is challenging since electrochemical responses are controlled by diverse factors like enhanced mass transport and adsorption as well as electron transfer kinetics. A joint computational and experimental strategy is employed. Chapter 1, 2 and 3 cover essential introductory material and basic experimental details relevant to all experiment. Fuller descriptions and details are given in the following chapters as and when needed. Chapter 4 reports the development of an electrochemical characterization method, to achieve a fast and simple quantification of the average particle size and the number of nanoparticles deposited on a glassy carbon electrode. The method consists of surface area characterization by underpotential deposition of lead particles and the determination of the amount of gold from anodic stripping in HCl. This method is also proven to be effective by comparing the results with SEM measurements. Next, in chapter 5, a generic strategy combining computation and experimental approach is developed in order to study the electron transfer kinetics of gold nanoparticles. The modelling part considers the kinetics of the electrochemical process on the bulk materials for different regions in the electrode, that is, the substrate (glassy carbon) and the nanoparticles (gold). Comparison of experimental and theoretical results enables the detection of changes in the electrode kinetics at the nanoscale. This approach is applied into the electro-oxidations of nitrite and L-ascorbic acid for gold nanoparticles from 20 - 90 nm. In the former, analysing the system shows that no change in electron transfer kinetics is involved in the process, even though a decrease of the over-potential and an increase in the peak current are observed. But these changes reflect mass transport effects, not electrocatalysis. A case where an authentic enhanced electron transfer kinetic change occurs is shown for the ascorbic acid system. Finally, in chapter 6 , the above strategy is exploited further to apply a quantitative study of electron transfer kinetics for various sizes of gold nanoparticles in the oxygen reduction reaction system in sulphuric acid at 298 K. The latter is at the heart of energy transformation techniques (fuel cells, battery and so on). Compared with the electron transfer kinetics on macro gold electrodes, there is no change at gold nanoparticles from size 5 nm to 40 nm. However, in the presence of Pb(II), a strong enhancement of electron transfer kinetics is observed on 5 nm citrate capped gold nanoparticles for ORR. On the other hand, a significant decrease of electron transfer kinetics has been found for gold nanoparticles of size 2 nm for ORR. The latter observation of strong negative electrocatalysis is also observed for the hydrogen evolution reaction (HER). This represents the first report of such effects with the HER system. Overall the thesis has established a rigurous, theoretical basis for evaluating electrocatalysis in nanoparticulate system.

and the placement of the material. Hence, 3D printing can be an advantageous new method of constructing supercapacitors.In this thesis, the aim was to investigate how the different parameters of Electrohydrodynamic printing (EHD printing) will affect the spread of gold nanoparticles. The electrohydrodynamic printing method is a printing method that utilizes an electric field to cause droplet ejection from the nozzle. When the electric field exerts a force on the solution containing nanoparticles, it stretches the meniscus to a point where it becomes unstable and forms a droplet. EHD printing utilizes an electric field which gives the method a high spatial accuracy while being able to print droplets with within a separation distance of tens of nanometers.Different parameters were evaluated to achieve desired distribution of gold nanoparticles across a silicon wafer substrate. This thesis focuses on print speed, frequency, heat treatment and voltage, and how printing parameters affect the results. The results revealed a variation, while the printing patterns follow a trend. The best results achieved in this work came from a low nozzle-substrate voltage, high frequency, and high printing speed. The varying results could be brought on by variation in ink composition, the nozzle diameter, and the metal coating of the capillary, to name a few possible causes.Handledare:

Thesis (M.S.)--West Virginia University, 2006.
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This thesis is focused on the synthesis of three different shapes of gold nanoparticles; the gold nanosphere, the gold nanorod and the gold nanocube. These will be synthesized using wet chemistry methods and characterized using UV-Vis- NIR spectroscopy and dynamic light scattering. The results will be used to draw some conclusions as to what factors influence the growth of gold nanoparticles.

This Thesis explores the properties and potential applications of 4-(dimethylamino)pyridine-capped gold (DMAP-Au) nanoparticles. The binding mode of the DMAP ligand to the gold surface was investigated in detail and the factors that make this substituted pyridine an effective protective ligand for gold nanoparticles were determined. DMAP-Au nanoparticle samples have a mean diameter between 5 and 6 nm and narrow size dispersity. DMAP is noncovalently bound to the nanoparticle surface via the endocyclic nitrogen. The positively charged nanoparticles are stable in aqueous solution over a wide pH range (5 to 12).
The interactions of DMAP-Au nanoparticles with the anionic polyelectrolytes poly(acrylate) and poly(styrene sulfonate) were investigated by following changes in the optical properties of the nanoparticles. The enhanced stability of the nanoparticles at low pH values observed in the presence of polyelectrolytes is attributed to the wrapping of the polyelectrolyte chains around the small nanoparticles. The study of the composition of the polyelectrolyte-coated nanoparticles reveals that the polyelectrolyte chains adsorb onto the DMAP protective monolayer rather than displace it at the nanoparticle surface.
The details of the interactions of the polyelectrolytes with a DMAP monolayer were further elucidated by using surface plasmon resonance (SPR) spectroscopy. This surface-sensitive technique allows the in situ study of the adsorption of the two polyelectrolytes on a 2D DMAP-modified gold surface and of their conformational changes as a function of pH. The results obtained correlate well with those of analogous 3D-systems. The polyelectrolyte chains are found to adsorb onto, and stabilize, the DMAP layer.
Finally, the use of DMAP-Au nanoparticles as a starting material in ligand exchange reactions was investigated. DMAP-Au nanoparticles prove to be excellent precursors to water- and organic-soluble nanoparticles. Relatively small amounts of incoming ligand are sufficient to fully replace the initial DMAP capping layer and the narrow size dispersity of the nanoparticles is maintained upon ligand exchange.

The kinetics and mechanism of the place exchange reaction(PER) of alkylthiols with alkylthiol-protected gold nanoparticles(AuNP) are investigated. Using chemically similar alkylthiols it was possible to study the reaction in the absence of perturbing factors, enabling detailed mechanistic and kinetic studies to be explored. It is found that the reactions are zero order in incoming ligand and overall follow a second order diffusion limited Langmuir rate law. In the case where there is little chemical distinction between the incoming and capping ligands, the reactions proceed to an endpoint consistent with a Keq=1. The rate of the reaction is dependent on the chain length of the capping ligand and the AuNP core size. The related dialkyldisulphide for-alkylthiol AuNP exchange reaction is consistent with the same rate law and also proceeds to a well-defined endpoint. However, the rate constant is 20-fold less than the alkylthiol case. These results lead to a convergent model of PERs where the rate limiting process involves both incoming and outgoing ligands, with diffusion of the incoming ligand to the AuNP surface as the major controlling factor of the reaction rate.

Gold nanoparticles effects on neurite outgrowth were assessed by measurement of neurite outgrowth in differentiating mouse neuroblastoma cell line NB2a exposed to 5 nm, 10 nm and 15 nm conventional gold colloids and monolayer protected clusters. Neurite outgrowth enhancement was the predominant effect of most particles types. The thesis also investigated the uptake and intracellular fate of gold nanoparticle in the NB2a cell line in a serum free environment, employing a 2-D profile-based counting method. It was found that the monolayer clusters were taken up in significantly less amounts than their conventional counterparts following 24 hour exposure. No evidence for cellular accumulation was found after seven days as particle clearance was shown to be greater than 90 %. In addition, the thesis describes the development of functionalised monolayer protected gold clusters for application in bilirubin extraction. Bilirubin neurotoxicity was determined by measuring neurite outgrowth in NB2a cells and the application of the gold nanoparticle system in ameliorating this effect was attempted. No significant changes were observed. The presence of virus-like particles in the neuroblastoma cell line was investigated in the line of a potential confounding factor to the observed toxicity results. The thesis therefore also describes the morphology and genomic features of a virus-like particle. The morphological appearance describes intracisternal A-particles (IAP) but the nucleotide sequence revealed evidence of the B-tropism of mouse leukaemia viruses suggesting a rare form of an infectious IAP. The finding of an infectious IAP in mouse NB2a cell has implication for the continued use of this cell line.

Radiotherapy is currently used in around 50% of cancer treatments. Although highly effective it is also damaging to surrounding healthy tissues and needs to be improved by better targeting of cancer cells. Improved radiotherapy outcomes can be achieved by using nanoparticles, especially those with high atomic number (Z), that interact with ionising radiation to generate secondary electrons and reactive species that increase cellular damage. One of the most promising elements to use is gold, in the form of gold nanoparticles (AuNPs) because of its biocompatibility and amenability to surface modification. For example, surface modification of AuNPs with simple sugars can improve their solubility and cellular uptake. Furthermore, positively charged AuNPs are thought to have an improved cellular uptake because of their interactions with negatively charged cell membranes. This thesis is focussed on two research areas: (1) the development of dual action chemo-radiosensitising AuNPs and (2) the development of oligonucleotide-AuNPs for radiosensitisation. (1) It is shown that sugar-PEGamine coated AuNPs demonstrate selective uptake and toxicity toward skin cancer cells with an IC50 of 1 μg/ml [Au], without damaging normal skin cells at this concentration. Oxidative stress and caspase-dependent apoptosis both play a key role in the toxicity of these AuNPs. Moreover, AuNPs coated with sugar and PEGamine show a strong radiosensitisation effect in combination with kilovoltage X-rays and a smaller effect with megavoltage X-rays. (2) Oligonucleotide-phosphine-coated AuNPs are shown to demonstrate a limited uptake in the cellular cytoplasm compared to the previous AuNPs but increase AuNPs uptake into the cell nucleus. The limited uptake into the cells, as well as the DNA triplex forming oligonucleotides (TFOs) attached to the AuNPs, is still responsible for a radiosensitisation effect, although smaller than with sugar:PEGamine AuNPs. In the future, the uptake of the oligonucleotides AuNPs may possibly be improved by varying their size (from 3.5 to 2 nm) and/or adding a spacer between the NP and the TFO.

Gold nanoparticle (AuNP) is used for the detection of biomolecules and study of the interaction between bio-molecules with the aid of dark field microscopy (DFM). AuNP exhibits unique optical properties and ability to conjugate with different biomolecules either by covalent binding or physical absorption, which allow the AuNP possessing a variety of biological application. We reported a sensitive detection system for measuring DNA–protein interaction at single plasmonic metal nanoparticles level by Localized Scattering Plasmon Resonance (LSPR) spectroscopy. As a proof of concept, DNA molecules were conjugated to gold nanoparticles (AuNPs) through gold–thiol chemistry and the resulted complex was served as single-particle probes of human topoisomerase I (TOPO). By recording the changes in Rayleigh light scattering signal of the individual nanoparticles upon protein binding, DNA–protein interaction was monitored and measured. The .max shifts in LSPR spectrum of individual AuNP was found to be highly correlated with the amount of TOPO that bound onto. We presented an immunosensing platform to detect cancer biomarkers by collecting the LSPR signal of immune-target conjugated gold nanoparticle (AuNP). Prostate specific antigen (PSA), which is a FDA-approved biomarker for prostate cancer, was chosen as an example. Herein, the immunoreaction of PSA, capturing PSA antibody (CHYH1) (Ab1), and detecting PSA antibody (CHYH2) (Ab2) was studied with a spectrometer coupled-dark field microscope. LSPR of immunotarget conjugated AuNP was directly measured. In brief, Ab1 and Ab2 were covalently conjugated with AuNPs separately, followed by addition of PSA for the formation of sandwiched immuno-complex in PBS solution. Then, the complex was immobilized on surface of glass slide for capturing dark-field images and LSPR spectra. Besides, to study the ligand-receptor interaction, we prospect a detection system at single plasmonic metal nanoparticle level by LSPR spectroscopy. Glucocorticoid receptor protein (GR) was chosen as example with two ligands ginsenoside-Rg1 (Rg1) and dexamethasone (DEX). Herein, dsDNA molecules were covalently conjugated with AuNPs and the resulted complex was used as single particle probes of GR. The binding of GR to the dsDNA could be promoted by the agonistic ligands. DNA-GR interaction in the presence of ligands was monitored and measured by recording the changes of LSPR upon protein binding. This technique provides a sensitive and high-throughput platform to screen and monitor accurately the speci.c biomolecular interactions. It is capable of revealing information such as particle–particle variations that might be buried in conventional bulk measurement.

This thesis investigated the interaction between light and gold nanoparticles, for gold nanoparticles sitting on a variety of surfaces. The work was both experimental and theoretical in nature. Using a custom designed experimental set-up we were able to probe the interaction of light with individual nanoparticles. We were also able to predict the interaction of light with gold nanoparticles sitting on graphene substrates. The work presented lays the groundwork for more extensive investigation of surfaces enhanced by the addition of gold nanoparticles.

Noble metal nanoparticles have a great potential for biological study, especially the use of gold nanoparticles is very popular. In this work gold nanoparticles (GNPs), silver nanoparticles (SNPs) and goldsilver hybrid nanoparticles (HNPs) synthesized and used as a carrier for electrochemical investigation of redox protein. Optical characterization of these nanoparticles was performed by UV-Vis spectroscopy. The maximum of the plasmon band for GNPs, SNPs and HNPs (ratio of 1:1) are 524, 392 and 455 nm respectively. The optical absorption spectra of HNPs solution shows only one plasmon absorption, it is concluded that mixing of gold and silver leads to a homogeneous formation of alloy nanoparticles. LCR meter study shows the HNPs is best conductance in compare of GNPs and SNPs. Therefore, the electron transfer of the homogenous GOx, HRP and Hb was investigates by electrochemical method in presence of HNPs. They demonstrated quasi-reversible cyclic voltammograms with a formal potential of -479, -178 and -168 mV in 50 mM phosphate buffer solution at pH 7.4 respectively.

Gold Nanoparticle-Aided Radiation Therapy (GNRT) is a new paradigm in radiation therapy which seeks to make a tumor more susceptible to radiation damage by modifying its photon interaction properties with an infusion of a high-atomic-number substance. The purpose of this study was to quantify the energy deposition due to secondary electrons from gold nanoparticles on a micrometer scale and to calculate the corresponding microscopic dose enhancement factor during GNRT. The Monte Carlo code EGSnrc was modified to obtain the spectra of secondary electrons from atoms of gold and molecules of water under photon irradiation of a tumor infused with 0.7 wt. % gold. Six different photon sources were used: 125I, 103Pd, 169Yb, 192Ir, 50kVp, and 6MV x-rays. Treating the scored electron spectra as point sources within an infinite medium of water, the event-by-event Monte Carlo code NOREC was used to quantify the radial dose distribution, giving rise to gold and water electron dose point kernels. These kernels were applied to a scanning electron microscope (SEM) image of a gold nanoparticle distribution in tissue. The dose at each point was then calculated, enabling the determination of the microscopic dose enhancement at each point. For the lower energy sources 125I, 103Pd, 169Yb, and 50 kVp, the secondary electron fluence was increased by as much as two orders of magnitude, leading to a one-to-two order of magnitude increase in the electron dose point kernel over radial distances up to 50 um. The dose was enhanced by 100% within 5 um of the nanoparticles, and by 5% as far away as 30 um. This study demonstrates a remarkable microscopic dose enhancement due to gold nanoparticles and low energy photon sources. Given that the dose enhancement exceeds 100% within very short distances from the nanoparticles, the maximum radiobiological benefit may be derived from active targeting strategies that concentrate nanoparticles in close proximity to the cancer cell and/or its nucleus.

Metallic nanoparticles (NPs) with various elemental composition, size, shape and physical or chemical properties has become active field of research. Among all the metal NPs noble metal ones are receiving much attention due to their special optical properties which make them useful for different applications. Noble metal NPs have bright colors resulting from strong surface plasmon resonance absorption usually in the visible region. The colors are size and shape dependent and provide the tuning of optical properties. The optical properties of NPs are also strongly depending on the nature of the NPs surface which plays a crucial role on chemical sensing. Therefore, surface modification of NPs has become increasingly important. In this study, gold NPs were prepared in aqueous phase by seed-mediated growth method. To enhance the optical properties, surface functionalization was performed by coating NPs with silver. The coating process was achieved by chemical reduction of silver ions on NPs surface. Thickness of silver layer on the NPs were attempted to be controlled by the amount of silver salt added into NPs solution. Coating process of different types of gold NPs (rod, octahedral, star) was done by the same procedure. Moreover, this attempt yielded control over silver layer thickness on sphere, rod and octahedral shaped gold NPs, but not on branched NPs. The structure, composition and spectroscopic properties of Au-Ag core shell NPs were characterized by UV-Vis spectroscopy, Field Emission Transmission Electron Microscope (FE-TEM) and Energy-dispersive X-ray (EDX) studies, Scanning Electron Microscope (SEM), and X-Ray Photoelectron Spectroscopy (XPS). The analysis showed that all NPs studied were successfully coated with silver and promising for further explorations in sensing and imaging applications.

Detection strategies that allow for simple, rapid, cost efficient and sensitive monitoring of proteins and their interactions with biomolecules are of great importance in drug development and diagnostics. This thesis describes the development of bioanalytical applications based on the tunable self-assembly of gold nanoparticles functionalized with a de novo designed polypeptide. Strategies for protein affinity sensing and for detection of several fundamentally important biological processes have been investigated, including Zn2+-mediated coordination between polypeptides and low molecular weight chelants and protease and phosphatase activity. A Zn2+ responsive synthetic polypeptide designed to fold into a helix-loop-helix motif and dimerize into a four-helix bundle has been used to control the stability and self-assembly of gold nanoparticles. This polypeptide has a high negative net charge at neutral pH as a consequence of its many glutamic acid residues, efficiently preventing folding and dimerization due to charge repulsion. Zn2+ coordination provides a means to trigger folding and dimerization at neutral pH. The polypeptide can be readily attached to gold nanoparticles via a cysteine residue in the loop region, retaining its folding properties and responsiveness to Zn2+. The polypeptide functionalized gold nanoparticles display excellent colloidal stability but aggregate reversibly after addition of millimolar concentrations of Zn2+. Aggregates are dense with a defined interparticle distance corresponding to the size of the four-helix bundle, resulting in a distinct red shift of the localized surface plasmon resonance band. Three completely different strategies for colorimetric biosensing have been developed, all being based on the same responsive hybrid nanomaterial. In the first strategy a synthetic receptor was co-immobilized on the gold nanoparticles together with the Zn2+ responsive polypeptide. Protein analyte binding to the receptor could be detected as this interaction sterically prevented aggregation induced by Zn2+. In the second strategy the reduction in colloidal stability caused by specific proteolytic cleavage of the immobilized polypeptide was exploited to monitor the enzymatic activity. The third strategy utilized the sensitivity of the system to small variations in Zn2+ concentration. The presence of low molecular weight chelants was found to influence the mode of aggregation, both by sequestering Zn2+ and through the formation of ternary complexes involving the polypeptides, which prevented dimerization and thus aggregation. This approach was further developed into a generic concept for phosphatase detection exploiting the different affinity of enzyme substrates and reaction products for Zn2+. The flexibility of the different detection schemes enables detection of a large number of analytes by exploiting the tunable stability of the nanoparticles and the possibilities to effectively decouple the recognition event and the nanoparticle stability modulation.

Gold nanoparticles have attracted much attention in the field of biological research, especially in biological imaging and sensing due to their unique physical properties. Fluorescence is a highly-sensitive, non-invasive biological study method and has been widely used in a variety of research topics. The aim of this thesis is to study the unique optical properties of gold nanoparticles and demonstrate their application in biological imaging and sensing through fluorescence microscopic and spectroscopic techniques. An introduction of gold nanoparticles and fluorescence techniques used in this project is given in Chapter 1. In Chapter 2, the synthesis method of gold nanoparticles, dependence of optical properties on particle size and shape, the unique spectroscopic characterization and microscopic application of gold nanorods are discussed. Fluorescence lifetime imaging microscopy (FLIM) based on two-photon luminescence lifetime from gold nanorods in cell culture, and the advantag es of this method in biological imaging are demonstrated in Chapter 3. In Chapter 4, the energy transfer between a DNA dye, 4'-6-Diamidino-2-phenylindole (DAPI), and different types of gold nanoparticles in solution is demonstrated using FLIM. Biological imaging application based on energy transfer between gold particles and DAPI in cell culture is discussed as well in this chapter. A study on energy transfer process concerning different excitation conditions is reviewed in Chapter 5. Furthermore, application of fluorescence resonant energy transfer (FRET) based FLIM method in the research of intracellular pathway of gold nanoparticles in cells is demonstrated. Chapter 6 presents a systematic study on the cytotoxicity of gold nanorods in cell culture using MTT (3-(4, 5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. The effects of particle shape, surface conditions, dosage, incubation time on the cytotoxicity and the mechanism of cytotoxicity are discussed. In Chapte 7, a brief summary and outlook to future work are presented.

The assessment of nanoparticle penetration through skin is of increasing importance not only to evaluate the toxicity associated with occupational or environmental exposure to nanoparticles, but also to design rules for the fabrication of new types of transdermal drug delivery or diagnostics approaches. While these have been the subject of much research, the lack of a systematic approach in the penetration experiments has created controversial results regarding whether nanoparticles do or not penetrate the skin. The aim of the research presented in the thesis is to investigate the penetration of gold nanoparticles through human and mouse skin, focusing on the effect of surface charge, morphology and specific functionalisation. To study this, a penetration protocol using organ culture was designed and tested to assure the maintenance of the skin integrity in the course of our experiments. Skin samples incubated with gold nanoparticles were characterized for penetration by NPs using inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, energy-dispersive Xray spectroscopy and photoluminescence microscopy. Furthermore, epithelial cell monolayers were exposed to the gold nanoparticles to evaluate the transport through the cellular barrier. Transmission electron microscopy, light microscopy and trans epithelial electric resistance were used to characterise the cell monolayers exposed to gold nanoparticles. Results obtained are important to enhance our understanding of the interaction of gold nanoparticles with skin, providing valuable information for the design of new nanoparticle-based transdermal delivery systems.

Nanoscale materials have great applications in many areas. One of these applications is for manufacturing ultra-compact and efficient sensors for chemical and biological molecule detection. Noble metals, such as gold (Au) and silver (Ag), because of their distinguished optical property"localized surface plasmon resonances (LSPRs) that exhibit low loss, are ideal materials to fabricate these nanoscale plasmonic particles or structures. This work addresses the synthesis, characterization, and sensing applications of Au and Ag nanoparticles (NPs). The progress on certain subjects related to our work"NP synthesis, surface functionalization, Au sphere-film structure and two-photon fluorescence"are reviewed in Chapter 1. We also show the calculation results of LSPRs of Au nanosphere suspensions using Mie theory. The measured extinction spectra of Au nanosphere suspensions agree with the calculated results very well. Chapter 2 is a chapter describing the chemical synthesis of a variety of NPs, such as Ag prisms and cubes, Au spheres, rods, and bipyramids. These experiments involved different synthetic mechanisms and methods which enabled us to prepare NPs with desired shapes and optical properties. To put these NPs into application, it is desirable and sometimes necessary to functionalize their surfaces. In Chapter 3, we present the functionalization of Ag cubes with poly(allylamine hydrochloride) (PAH) and poly(allylamine hydrochloride)-dithiocarbamate (PAH-DTC), which follows our previous work on Au NPs. The purpose of studying Ag instead of Au is to use the stronger plasmonic enhancement in Ag when applied to two-photon imaging applications. However, we found that PAH-DTC shrank the Ag cubes. We also functionalized the cationic hexadecyltrimethylammonium bromide (CTAB)-stabilized Au NRs with anionic poly(sodium 4-styrenesulfonate) (PSS). Coated with the strong polyelectrolyte PSS, the NRs become more manageable and can be stable for over six months and are easily immobilized onto positively charged substrate. We put PSS-functionalized Au NPs into use and studied their adsorption process onto PAH-coated optical fiber tapers by monitoring the transmission light through the fiber. When the diameter of the fiber taper gets smaller, stronger coupling occurred between transmitted light inside the taper and the Au NPs on the taper surface (cylinder). This coupling resulted in a loss of the guided light at the plasmon resonance wavelength of the NPs. By monitoring this loss, we can study the adsorption rate of Au NPs onto the fiber. In Chapter 4, we used Au nanospheres to study the adsorption rate on substrates with different curvatures. We also established a theoretical model to explain this phenomenon for cylindrical surface as well as planar and spherical surfaces. Our results fit well with the theory, which predicts that particle adsorption rates depend strongly on surface geometry, and can exceed the planar surface deposition rate by over two orders of magnitude when the diffusion length of the particle is large compared to the surface curvature. In Chapter 5, we studied the optical properties of Au nanospheres separated from a thick Au film by a polyelectrolyte multilayer (PEM) film assembled from PAH and PSS under specific pH condition. The PEM film undergoes swelling and shrinking when the environmental pH is changed as a result of charging and discharging of the polyelectrolytes. Therefore, the PEM film provides an efficient means to tune the distance between Au spheres and Au film. The extinction peak blue-shifted as much as 100 nm when the pH of the water changed from pH 10 to pH 3 for 100 nm diameter Au spheres on a PEM film assembled at pH 9.5. Our preliminary estimates that the gap between sphere and surface can be as small as a few nm even though the film itself is tens of nm thick when it is not constrained by Au spheres. We studied two-photon excitation fluorescence (TPEF) from Ag triangles in Chapter 6. The triangles were fabricated by nanosphere lithography, which used convective self-assembly to make the nanosphere mask. The LSPRs of the nanotriangles were tuned to be in the 800--900 nm range to match with the Ti:Sapphire pulse laser at 880 nm. We found that certain spots on the fluorescence images gave rise to larger fluorescence intensity than rest of the area. SEM imaging reveals that the unusually bright spots seen on the surface were related to regions where the triangles transformed to spherical particles. The larger intensity is tentatively ascribed to the plasmon resonance of those spherical particles in ~400 nm range.
Ph. D.

The colloidal self-assembly of plasmonic gold nanoparticles (AuNPs) is of interest to utilize the plasmonic coupling effects that arise between nanoparticles. The enhanced properties of anisotropic AuNPs make them particularly attractive in self-assemblies. Herein, a literature study into the different strategies used to obtain self-assemblies of AuNPs using molecular linkers is presented. The use of nanospheres (AuNS) and nanorods (AuNRs) were mainly reviewed. Thereafter, two different nanobipyramids (AuBPs) were investigated for use in self-assemblies. The concentration of cetyltrimethylammonium bromide (CTAB), which coats the AuNP surface, was manipulated to study the stability of the AuNPs. A stable, meta-stable and non-stable region were identified for the nanoparticles. At low CTAB levels, the AuNPs preferentially assemble end-to-end. The addition of L-cysteine to stable AuNP dispersion induced end-to-end assembly, showing promise as a molecular linker for AuBPs. The addition of excess CTAB stabilized the assemblies over time. The kinetic behaviour of the two AuBPs differed, suggesting the effect of the AuNP shape on the self-assembly kinetics. This study provides a starting point for the development of a robust self-assembly strategy for anisotropic AuNPs by using L-cysteine as a molecular linker.
Den kolloidala självsammansättningen av ytplasmoniska guld nanopartiklar (AuNPs) är av intresse för att utnyttja de plasmoniska kopplingseffekterna som uppstår mellan nanopartiklar. De fördelaktiga egenskaperna hos anisotropa AuNP gör dem särskilt intressanta för självsammansättningar. En litteraturstudie har gjorts på de olika strategier som används för att erhålla självsammansättningar av AuNPs med hjälp av molekylära länkar. Användningen av nanosfärer (AuNS) och nanostavar (AuNRs) i självsammansättningar undesöktes huvudsakligen. Därefter undersöktes två olika nanobipyramider (AuBPs) för användning i självsammansättningar. Koncentrationen av cetyltrimetylammonium bromid (CTAB), som täcker AuNP-ytan, manipulerades för att undersöka AuNPs stabilitet. En stabil, meta-stabil och instabil region identifierades för nanopartiklarna. Vid låga CTAB-nivåer sammansätts AuNPs ände-mot-ände. Tillsatsen av L-cystein till stabila AuNP dispersioner inducerade sammansättningar ände-mot-ände, vilket visar L-cysteins potential som en molekylär länk för AuBPs. Tillsatsen av en stor mängd CTAB stabiliserade självsammansättningarna för en längre tid. Det kinetiska beteendet hos de två AuBPs skilde sig, vilket tyder på effekten av AuNP-formen på den självsammansättningskinetiken. Denna studie erbjuder en startpunkt för utvecklingen av en robust självsammansättningstrategi för anisotropa AuNPs genom att använda L-cystein som en molekylär länk.

An estimated 12 million people worldwide are diagnosed with cancer every year, with around 17 million cancer-related deaths per year predicted by 2030 (Thun et al. 2010). Contemporary clinical treatments include surgery, chemotherapy and radiotherapy, however all vary in success and exhibit unpleasant side effects. Localised tumour hyperthermia is a moderately new cancer treatment envisaged by researchers, which exploits exclusive tumour vulnerabilities to specific temperature profiles (42-45°C) leading to cancer cell apoptosis, whilst normal tissue cells are relatively unaffected. Hyperthermia is therefore proposed as an alternative potential therapy for cancer, by delivering localised treatment to cancer cells, without the severe side effects associated with traditional therapies. This project aimed to investigate potential hyperthermic treatment of cancer cells in vitro by adopting nanomedicine principles. Inorganic nanoparticles, such as gold or iron oxide, are both capable of generating heat when appropriately stimulated, therefore both have been suggested as candidates for inducing localised tumour heating following their internalisation into cells. In this project, both gold (GNPs) and magnetic (mNPs) were individually assessed for their potential to deliver toxic thermal energy to bone cancer cells (MG63) and breast cancer cells (MCF-7). Studies were carried out both in standard 2D monolayer and in 3D tumour spheroids. When considering use in vivo, it is essential that both GNPs and mNPs are biocompatible, therefore initial studies characterised the cell viability and metabolic activity following incubation with the NPs. The NP internalisation was subsequently verified, prior to hyperthermic studies. Following hyperthermic treatment, both GNPs and mNPs were confirmed as inducing cancer cell death. Further studies were carried out using the GNPs, to identify the cell death pathways activated, where mitochondrial stress was evident following 2D culture tests. Gene and protein expression analysis indicated that cell death occurred predominantly via several apoptotic pathways, through increased fold expression changes in apoptotic markers. Interestingly, cell protective mechanisms were simultaneously switched on, as cells were also observed to exhibit thermotolerance with a number of heat shock proteins (Hsps) being substantially increased during hyperthermic treatments.

The research work described in this thesis concerns the synthesis, characterisation and study of the catalytic activity of supported gold nanoparticles (AuNPs) immobilised on various oxide supports, i.e. silica (SiO2), alumina (Al2O3), titania (TiO2) and magnetite (Fe3O4), previously functionalised with [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS). The alkynyl-carbamate moieties anchored on the support were capable of straightforwardly reducing the gold precursor chloroauric acid (HAuCl4) to afford Au/OS@Yne (OS = Oxide Support, Yne = organic functionalisation), without the need of additional reducing or stabilising agents. The resulting materials were characterised by means of several complementary techniques, such as thermogravimetric analysis (TGA), atomic absorption spectroscopy (AAS), transmission electron microscopy (TEM), solid state NMR spectroscopy (SS NMR) and x-rays photoelectron spectroscopy (XPS), in order to investigate their structural and chemical properties. Furthermore, the catalytic activity of the obtained Au/OS@Yne was evaluated first in the oxidation of alcohols and then in the hydroamination of alkynes. Finally, during a six months stay at the Karl-Franzens University of Graz, a second research work was carried out, concerning the study of metal organic frameworks biocomposites.

The objectives of the present work are to investigate the influence of stabilizers in colloidal methods (sol-immobilization method) for the synthesis of preformed Au colloidal nanoparticles and the immobilization of the synthesized Au colloidal nanoparticles on supports, like activated carbon. By varying the nature of stabilizer (PVP, PEG, and PVA) and the weight ratio of stabilizer to metal, a number of Au based catalysts were prepared and the catalytic performance of the synthesized catalysts was tested for a range of model reactions. To determine the morphology of the unsupported and supported metal nanoparticles, several characterization techniques were used (UV-Vis, XRD, TEM, and XPS) to determine the mean particle and crystallite size of Au, the particle size distribution, the oxidation state of the Au, and the surface coverage of Au onto the support. From TEM analysis, it can be shown that in the absence of the polymer that acts as stabilizing agent gives worst dispersion of the Au nanoparticles on the support, affects thermal stability of the supported Au nanoparticles, enhance the agglomeration of the Au nanoparticles for reactions at high reaction temperature and decrease the number of active sites. However, from XPS analysis it was observed that at high polymer:Au weight ratio (more than 1.2) may increase the coverage of the gold nanoparticles on the surface, causing a decrease in the value of Au available on the catalyst surface. A series of catalysts were synthesized and the catalytic performance was investigated for each reaction: Glucose oxidation to glucaric acid, HMF oxidation to 2,5-furandicarboxylic acid, oxidation of 1,6 Hexanediol to Adipic acid, furfural oxidative condensation and oxidative esterification, 4-Nitrophenol reduction to 4-aminophenol. The optimum polymer:Au weight ratio in terms of catalytic performance for each reaction is not the same and an explanation could be attributed to the different reaction conditions used.

2014 - 2015
Gold Nanoparticles are nanomaterials whose properties are completely different from the ones of the bulk material. Nowadays many chemists have been using them as catalysts which work under mild conditions and respect the principles green and sustainable chemistry. The increasing need for new heterogeneous catalysts to be applied in industrial processes encourages the finding of efficient and selective catalytic systems. The aim of the current PhD project is the synthesis of gold nanoparticles (AuNPs) supported onto a porous polymer matrix, consisting of syndiotactic polystyrene-co-cis-1,4-polybutadiene (sPSB) and the use of this hybrid material in redox reactions. Aerobic oxidative esterification of cinnamyl alcohol and nitroarenes reduction to amines were chosen as benchmark reactions to assess the activity and selectivity of the AuNPs-sPSB catalyst. In cinnamyl alcohol oxidation and esterification, a large number of products can be obtained, coming from oxidation, dehydrogenation or reduction pathways, but the catalytic system here presented resulted highly selective towards cinnamaldehyde and alkyl cinnamates. The synthetic protocol was successfully extended to p-substituted cinnamyl alcohols, and information about the effects of Electron Withdrawing or Electron Donating Groups on the esterification of cinnamyl alcohol were achieved. Nitroarenes reduction to aniline derivatives is a complex multistep reaction, since the main intermediates are azoxybenzene and azobenzene. Once again, the AuNPs-sPSB catalyst was selective in the aniline formation. Different reaction pathways have been proposed for this reaction; under the reaction conditions here used the condensation route proposed by Haber was detected. The access of reagents to the catalytic active site is facilitated by the presence of nanoporous polymeric matrix, whose role is to determine which species are able to permeate the polymeric matrix in order to reach the AuNPs. Different kinetic studies confirmed this initial hypothesis. In addition to the AuNPs-sPSB catalyst, gold colloids were immobilized on a polymeric support in order to investigate a different synthetic approach for the achievement of gold nanoparticles. Different supports have been tested, e.g. polyvinyl alcohol, polyvinylpyrrolidone, cetrimonium bromide and P123 (a poloxamer triblock co-polymer). The removal of the colloid stabilizer was evaluated through catalytic tests. [edited by author]
XIV n.s.

Carbohydrate recognition plays an important role in many biological processes such as cell-cell recognition or bacterial infection. It is important to develop methodologies for carbohydrate recognition to expand the knowledge about the recognition process, but also for applications in diagnostic and medical fields. However, carbohydrate recognition in aqueous media is a difficult task. Carbohydrates are highly hydrophilic species with an impressive line-up of hydroxyl groups blending easily into a background of water molecules. In addition, the structural differences between many carbohydrates are often very subtle. This makes the development of synthetic receptors for carbohydrate recognition in water highly challenging. AuNPs present very interesting features which can be exploited for the design of novel chemical and biological sensors. In the Prins’ group AuNP 1, which are gold nanoparticles (d= 1.8 ± 0.4 nm) covered with hydrophobic C9-thiols terminating with a 1,4,7-triazacyclonone (TACN)·Zn2+, have been extensively used for application in sensing, catalysis and system chemistry. In this thesis AuNP 1 have been used for the study of carbohydrate recognition. The studies aim at providing the initial bases for the development of innovative synthetic carbohydrate receptors that bind carbohydrates in water using non-covalent interactions.
Il riconoscimento dei carboidrati svolge un ruolo importante in molti processi biologici come il riconoscimento delle cellule o l'infezione batterica. È importante sviluppare metodologie per il riconoscimento dei carboidrati per ampliare le conoscenze sul processo di riconoscimento, ma anche per applicazioni in campo diagnostico e medico. Tuttavia, il riconoscimento di carboidrati in mezzi acquosi è un compito difficile. I carboidrati sono specie altamente idrofile con un impressionante allineamento di gruppi ossidrile che si fondono facilmente in uno sfondo di molecole d'acqua. Inoltre, le differenze strutturali tra molti carboidrati sono spesso molto sottili. Questo rende lo sviluppo di recettori sintetici per il riconoscimento di carboidrati in acqua molto impegnativo. Gli AuNP presentano caratteristiche molto interessanti che possono essere sfruttate per la progettazione di nuovi sensori chimici e biologici. Nel gruppo Prins, l'AuNP 1, che sono nanoparticelle d'oro (d = 1,8 ± 0,4 nm) ricoperte di C9-tioli idrofobi terminanti con un 1,4,7-triazaciclonone (TACN) · Zn2 +, sono state ampiamente utilizzate per l'applicazione nel sensing , catalisi e chimica del sistema. In questa tesi l'AuNP 1 è stato utilizzato per lo studio del riconoscimento dei carboidrati. Gli studi mirano a fornire le basi iniziali per lo sviluppo di innovativi recettori sintetici dei carboidrati che legano i carboidrati in acqua usando interazioni non covalenti.

Specific and reliable protein sensing and detection is a challenge of increasing interest due to their role as biomarkers in many diseases. Classical proteomics require time-consuming separation techniques and lacks the capability to assess protein activity variations uncorrelated to expression levels. Activity-based protein profiling (ABPP) is a strategy in which chemical probes (irreversible protein inhibitors) are covalently bound to target proteins with a shared activity and some signal arising from the probe is quantified, being sensitive to protein activity due to the binding step. Nonetheless, protein separation is still expensive in terms of time or requires the use of high-cost instrumentation. Our proposal was to employ gold nanoparticles as a tool for covalently capturing proteins of interest and separating them with ease from the remaining proteome by size-differentiation. Mixed monolayer nanoparticles have been obtained by two different methods, by direct substitution on an homogeneous monolayer or by supramolecular click-coupling reactions onto azido-functionalized derivatives. The two strategies were shown to be complementary; thiol exchange is simpler but substitution yields are difficult to predict when new thiols are tested whereas reliable click-coupling onto pre-substituted azido-nanoparticles requires the use of dibenzocyclooctyne derivatives to obtain high yields. We have developed and fully characterized supramolecular conjugates of gold nanoparticles with a thiol-based mixed-monolayer that endow the nanoparticles with high water solubility but also the capability to expose the targeting moiety on their surface. Avidin-biotin interaction has been chosen as model system to prove the capability of functionalized nanoparticles to effectively reach protein active sites and displace small molecules from their binding site in competition assays. On the other hand, supramolecular architectures based on chain-like arrays of nanoparticles have been prepared and shown to fuse in water to form nanorods or nanowires by treatment with glucosamine phosphate. Addition of thiol during the incubation stop nanoparticle fusion, opening the possibilities for a potential synthetic method to obtain anisotropic systems for NIR sensing.
Rilevare e riconoscere proteine in modo specifico ed affidabile costituisce una sfida di crescente interesse a causa del ruolo che esse hanno come marcatori in molte malattie. La proteomica classica richiede tecniche di separazione assai dispendiose in termini di tempo e manca della capacità di correlare le variazioni di attività delle proteine che non siano legate ai loro livelli di espressione. L’identificazione di proteine sulla base della loro attività (activity-based protein profiling, ABPP) è una strategia in cui una specifica molecola (tipicamente un inibitore irreversibile della proteina) viene coniugata mediante un legame covalente alle proteine bersaglio caratterizzate da attività simile. Mediante un ‘reporter’, quale ad esempio un gruppo fluorescente, è possibile seguire il processo di coniugazione e rilevare la presenza delle proteine . Tuttavia, la separazione delle proteine coniugate dal resto del proteoma è ancora costosa sia in termini di che strumentali. La mia proposta era di impiegare nanoparticelle di oro come strumenti per catturare in modo covalente proteine di interesse separandole poi con facilità dal proteoma in ragione della loro diversa dimensione. Ho ottenuto nanoparticelle di oro passivate da un monostrato a composizione mista mediante due approcci sintetici diversi, rispettivamente mediante sostituzione diretta su un monostrato omogeneo o mediante reazioni di coniugazione utilizzando cicloaddizioni tipo’click’ sul sistema supramolecolare sfruttando derivati azido-funzionalizzati. Le due strategie hanno dimostrato di essere complementari. Lo scambio di tioli è più semplice, ma il grado di scambio è difficile da prevedere quando si usano nuovi tioli. Al contrario le reazioni di cicloaddizione ‘tipo click’ sono affidabili quando si usano derivati del dibenzocicloottino, ma richiedono una pre-funzionalizzazione del monostarto della nanoparticella. Ho sintetizzato e completamente caratterizzato sistemi supramolecolari costituiti da nanoparticelle di oro con monostrato misto ancorato sulla superficie dell’oro mediante un gruppo tiolico e dotate non solo di elevata solubilità in acqua, ma anche della capacità di esporre la porzione di targeting sulla loro superficie. Ho scelto l’interazione avidina-biotina come sistema modello per verificare la capacità delle nanoparticelle funzionalizzate di raggiungere in modo efficace il sito attivo di una proteina e di spostare eventuali substrati presenti nel loro sito di riconoscimento. In fine, ho realizzato architetture supramolecolari basate su array concatenati di nanoparticelle e ho dimostrato che essi sono in grado di fondersi tra di loro in acqua per formare nanotubi o nanofili in seguito al trattamento con glucosamina fosfato. L'aggiunta di tiolo, stabilizzando la struttura che si è formata durante la fusione delle nanoparticelle, previene l’ulteriore crescita, aprendo la possibilità ottenere sistemi anisotropi con caratteristiche spettroscopiche molto interessanti e potenzialmente sfruttabili per ‘sensing’ nel vicino IR (NIR).

Thesis (M.S.)--University of Maryland, College Park, 2004.
Thesis research directed by: Dept. of Chemistry and Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Polyelectrolytes coated on high surface curvature nanoparticles (NPs) have been prepared and characterized by a variety of solid-state nuclear magnetic resonance (NMR) experiments in order to examine surface interactions, polymer-water association and polymer dynamic properties of layer components. Gold nanoparticles of four nanometers in diameter pre-stabilized by 4-dimethylaminopyridine (DMAP), and silica and neodymium NPs were chosen as substrates for these studies. The high surface to volume ratio provided by such nanoparticles is advantageous for NMR analysis, which requires a high material content for adequate sensitivity. Firstly, poly(styrene sulfonate) was deposited on gold NPs by electrostatic self-assembly where charged polyelectrolytes adsorb onto an oppositely charged substrate. Surface charges on gold NPs were provided by the ligand DMAP that induces a positive charge at the NP surface that is otherwise neutral. Nanoparticle encapsulation by PSS was monitored by the gold surface plasmon absorption band (SPB) which revealed a good stability under assembly conditions where the pH was maintained above the DMAPsoln pKa and for a polymer radius of gyration comparable to the particle radius. An electrostatic association between DMAPbound and PSS, rather than a ligand substitution, was detected by solid state 13C NMR. When a subsequent layer composed of a weak or a strong polycation was added, the stability of the bilayer was found to be dictated by the nature of the multiple, weak interactions of the polymer functional groups (SO3, NH2, N(CH 3)2+Cl-, NH3 +) with the gold surface relative to that of DMAPbound which in turn is influenced by the assembly pH.
A detailed study of the interactions between the polyelectrolytes, stabilizers and substrates was also extended to polyelectrolyte multilayers coated on gold NPs of different dimensions. Limitations in the application of the layer-by-layer self-assembly technique to very small NPs were investigated and strategies to optimize the method were proposed. 1H NMR analysis in the solid state and 2H NMR analysis in solution revealed that water association and film dynamics were closely related to the identity of the capping layer and independent of even/odd layer effects. These results were compared to those obtained for larger NP substrates which revealed many similarities between the two systems.
A study of the parameters that affect the fabrication of Poly(L-lysine) and DNA polyelectrolyte multilayer films was also conducted for both flat and highly curved surfaces. Such polyelectrolyte films coated on nanopartic1es can be considered as potential vectors for gene therapy. Control over DNA loading into films was performed by varying the ionic strength and pH of polyelectrolyte assembly solutions. DNA density, film degradability and transfection efficiency were examined to determine optimal conditions for vector preparation in gene therapy. Finally, the acid-base properties of lanthanide-based nanoparticles of 10 nm of diameter were explored under a wide range of pH conditions. The interactions of the neodymium oxide nanoparticles with the cationic poly(allylamine hydrochloride) and the anionic poly(styrene sulfonate) polymers were investigated by following spectroscopically optical changes in suspension absorbance and visual changes in NP dimensions. Transparancy and efficiency of stabilization were the evaluated criteria for polymers to be considered as potential stabilizing agents for neodymium oxide NPs used in neutrino detection experiments.

[ES] La presente tesis doctoral titulada "Reconocimiento de neurotransmisores basado en nanopartículas de oro y de sílice mesoporosa para aplicaciones de detección y liberación controlada" es una tesis realizada por compendio de artículos la cual se centra en el diseño, preparación, caracterización y evaluación de distintos nanodispositivos para la detección colorimétrica de neurotransmisores y sistemas de liberación controlada que responden a neurotransmisores basados en nanopartículas de oro y nanopartículas de sílice mesoporosa, equipadas con ligandos orgánicos, efectores enzimáticos, puertas moleculares y especies cromofluorogénicas o medicamentos. En el primer capítulo se introduce una visión general de lo que son los neurotransmisores, sus principales características y el importante papel que éstos desempeñan en el funcionamiento de nuestro organismo. Además, se presenta una descripción general de las propiedades y potenciales aplicaciones de las nanopartículas de oro funcionalizadas con ligandos orgánicos como sistemas de detección y las nanopartículas mesoporosas de sílice funcionalizadas con puertas moleculares como sistemas de liberación controlada. A continuación, en el segundo capítulo se presentan los objetivos generales que son abordados en los siguientes capítulos experimentales. En el tercer capítulo, se presentan tres sistemas de detección colorimétrica de neurotransmisores basados en la agregación de nanopartículas de oro doblemente funcionalizadas con ligandos orgánicos. El primer sistema es un sensor capaz de detectar de forma selectiva el neurotransmisor serotonina, utilizando nanopartículas de oro funcionalizadas con ditio-bis(propionato de succinimidilo) y N-Acetil-L-Cisteína. El segundo sistema consiste en un sensor para la detección selectiva del neurotransmisor norepinefrina diseñado a partir de nanopartículas de oro funcionalizadas con 4-(liponiloxi)benzaldehído y ácido 4-mercato fenilborónico. El tercer sistema está compuesto por nanopartículas de oro funcionalizadas con 4-(liponiloxi)benzaldehído y N-Acetil-L-Cisteína, para la detección de normetanefrina, un importante biomarcador del tumor feocromocitoma. Todos estos sistemas se evalúan en medios competitivos como suero sanguíneo u orina. En el cuarto capítulo se muestran dos sistemas de liberación controlados enzimáticamente basados en la apertura de puertas moleculares. El primer sistema de liberación controlada responde a la presencia del neurotransmisor acetilcolina. En concreto, se utilizan nanopartículas de sílice mesoporosa funcionalizadas en su superficie con grupos de ácido fenilborónico y tapadas con la enzima acetilcolinesterasa mediante la formación de ésteres cíclicos de ácido fenilborónico entre las cadenas de oligosacáridos de la enzima y los grupos fenilborónicos de la superficie de las nanopartículas. En este caso la reacción enzimática produce ácido acético que da lugar a la hidrolisis de los ésteres borónicos, destapando los poros y liberando la carga contenida en el interior. Además, se evalúa la capacidad del dispositivo diseñado para liberar el citotóxico doxorubicina en células cancerosas en presencia de acetiltiocolina. El segundo sistema consiste en un nanodispositivo para la liberación controlada en respuesta al neurotransmisor L-glutamato. Para esto se utilizan nanopartículas tipo Janus de oro-sílice mesoporosa funcionalizadas con la enzima L-glutamato oxidasa en la parte del oro y con una puerta molecular autoinmolante de arilboronato en la superficie de la sílice. La liberación controlada se basa en el reconocimiento del L-glutamato por la enzima L-glutamato oxidasa y la posterior formación de peróxido de hidrogeno, que es la especie que induce la escisión de la puerta autoinmolante y la subsecuente apertura de los poros. Finalment es mostra que el sistema dissenyat és capaç d'alliberar un fàrmac citotòxic en cèl·lules de càncer de cervell després de detectar la presència de L-glutamat.
[CA] La present tesi doctoral titulada "Reconeixement de neurotransmissors basat en nanopartícules d'or i de sílice mesoporosa per a aplicacions de detecció i alliberació controlada" és una tesi realitzada per compendi d'articles la qual se centra en el disseny, preparació, caracterització i avaluació de diferents nanodispositius per a la detecció colorimètrica de neurotransmissors i sistemes d'alliberació controlada que responen a neurotransmissors basats en nanopartícules d'or i nanopartícules de sílice mesoporosa equipades amb lligands orgànics, efectors enzimàtics, portes moleculars i espècies cromofluorogénicos o medicaments. En el primer capítol s'introdueix una visió general del que són els neurotransmissors, les seves principals característiques i l'important paper que aquests tenen en el funcionament del nostre organisme. A més es presenta una descripció general de les propietats i potencials aplicacions de les nanopartícules d'or funcionalitzades amb lligands orgànics com a sistemes de detecció, i de les nanopartícules mesoporoses de sílice funcionalitzades amb portes moleculars com a sistemes d'alliberament controlat. A continuació, en el segon capítol es presenten els objectius generals que són abordats en els següents capítols experimentals. En el tercer capítol, es presenten tres sistemes de detecció colorimètrica de neurotransmissors basats en l'agregació de nanopartícules d'or doblement funcionalitzades amb lligands orgànics. El primer sistema és un sensor capaç de detectar de forma selectiva el neurotransmissor serotonina, utilitzant nanopartícules d'or funcionalitzades amb ditiobis (propionat de succinimidilo) i N acetil-L-cisteïna. El segon sistema consisteix en un sensor per a la detecció selectiva de neurotransmissor norepinefrina dissenyat a partir de nanopartícules d'or funcionalitzades amb 4- (liponiloxi) benzaldehid i Àcid 4-mercatofenilborònic. El tercer sistema està compost per nanopartícules d'or funcionalitzades amb 4- (liponiloxi) benzaldehid i N acetil-L-cisteïna, per a la detecció de normatanefrina un important biomarcador del tumor feocromocitoma. Tots aquests sistemes s'avaluen en mitjans competitius com sèrum sanguini u orina. En el quart capítol es mostren dos sistemes d'alliberament controlats enzimàticament basats en l'obertura de portes moleculars. El primer sistema d'alliberament controlat respon a la presència del neurotransmissor acetilcolina. En concret, s'utilitzen nanopartícules de sílice mesoporosa funcionalitzades en la seva superfície amb grups d'àcid fenilborònic i tapades amb l'enzim acetilcolina esterasa mitjançant la formació d'èsters cíclics d'àcid fenilborònic entre les cadenes d'oligosacàrids de l'enzim i els grups fenilborónicos de la superfície de les nanopartícules. En aquest cas, la reacció enzimàtica produeix àcid acètic que dóna lloc a la hidròlisi dels èsters borònics, destapant els porus i alliberant la càrrega continguda a l'interior. A més, s'avalua la capacitat del dispositiu dissenyat per alliberar el citotòxic doxorubicina en cèl·lules canceroses en presència d'acetiltiocolina. El segon sistema consisteix en un nanodispositiu per alliberació controlada en resposta al neurotransmissor L-glutamat, per al que s'utilitzen nanopartícules tipus Janus d'or-sílice mesoporosa funcionalitzades amb l'enzim L-glutamat oxidasa en la part de l'or i amb una porta molecular autoimmolant d'arilboronat a la superfície de la sílice. La alliberació controlada es basa en el reconeixement de L-glutamat per l'enzim L-glutamat oxidasa i la posterior formació de peròxid d'hidrogen, que és l'espècie que indueix l'escissió de la porta autoimmolant i la subseqüent obertura dels porus. Finalment es mostra que el sistema dissenyat és capaç d'alliberar un fàrmac citotòxic en cèl·lules de càncer de cervell després de detectar la presència de L-glutamat.
[EN] This doctoral thesis entitled "Neurotransmitters recognition based on gold and mesoporous silica nanoparticles for sensing and controlled release applications" it is a thesis carried out by compendium of articles, which is focused on the design, preparation, characterization and evaluation of nanodevices for the colorimetric sensing of neurotransmitters and controlled delivery systems responsive to neurotransmitters, based on gold nanoparticles and mesoporous silica nanoparticles equipped with organic ligands, enzymatic effectors, molecular gates and chromo-fluorogenic species or drugs. The first chapter introduces an overview about what neurotransmitters are, their main characteristics and the important role they play in the functioning of our body. In addition, a general description of the properties and potential applications of gold nanoparticles functionalized with organic ligands as detection systems and mesoporous silica nanoparticles functionalized with molecular gates as controlled delivery systems is presented. In the second chapter, the general objectives that are addressed in the following experimental chapters are presented. In the third chapter, three colorimetric detection systems of neurotransmitters based on the aggregation of gold nanoparticles doubly functionalized with organic ligands are presented. The first system is a sensor capable of selectively detecting the neurotransmitter serotonin, using gold nanoparticles functionalized with dithio-bis(succinimidyl propionate) and N acetyl-L-cysteine. The second system consists of a sensor for the selective detection of the neurotransmitter norepinephrine designed from gold nanoparticles functionalized with 4- (liponyloxy)benzaldehyde and 4-mercaptophenylboronic acid. The third system is composed of gold nanoparticles functionalized with 4-(liponyloxy)benzaldehyde and N-Acetyl-L-Cysteine, for the detection of normetanephrine, an important biomarker of the pheochromocytoma tumor. All these systems are evaluated in competitive media such as blood serum or urine. In the fourth chapter, two enzymatic controlled delivery systems based on the opening of molecular gates are developed. The first controlled delivery system responds to the presence of the neurotransmitter acetylcholine. Specifically, it consists of mesoporous silica nanoparticles functionalized on their surface with phenylboronic acid groups and capped with the enzyme acetylcholinesterase, via the formation of cyclic phenylboronic acid esters between the oligosaccharide chains of the enzyme and the phenylboronic groups on the nanoparticles surface. In this case, the enzymatic reaction produces acetic acid that induces the hydrolysis of the boronic esters, uncapping the pores and releasing the entrapped payload. In addition, the ability of the nanodevice to release the cytotoxic doxorubicin in cancer cells in the presence of acetylthiocholine is evaluated. The second delivery system consists of a nanodevice responsive to the neurotransmitter L-glutamate. It is based on Janus gold-silica mesoporous nanoparticles functionalized with the enzyme L-glutamate oxidase in the gold part and with a self-immolative arylboronate molecular gate on the surface of the silica. Controlled delivery is based on the recognition of L-glutamate by the enzyme L-glutamate oxidase and the subsequent formation of hydrogen peroxide, which results in the cleavage of the self-immolative gate and the uncapping of the pores. Finally, it is shown that the designed system is capable of releasing a cytotoxic drug in brain cancer cells after detecting the presence of L-glutamate.
The authors acknowledge financial support from the Spanish Government (Projects MAT2015-64139-C4-1-R, MAT2015-64139-C4-4-R (MINECO/FEDER) and Project AGL2015-70235-C2-2-R) and the Generalitat Valenciana (Projects PROMETEOII/2014/047 and PROMETEO/2018/024). T. Godoy-Reyes is grateful to Generalitat Valenciana for her Santiago Grisolía fellowship. A. García-Fernández is grateful to the Spanish Government for her FPU fellowship. A. Llopis-Lorente thanks “La Caixa” Foundation for his PhD grant. SCSIE (Universitat de València) is gratefully acknowledged for all the equipment employed.
Godoy Reyes, TM. (2020). Neurotransmitters recognition based on gold nanoparticles and mesoporous silica nanoparticles for sensing and controlled release applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/158420
TESIS

Using a variety of techniques including femtosecond transient absorption spectroscopy, optical absorption, atomic force microscopy, the hot electron cooling dynamics of lithographically prepared gold nanoarrays, the effect of the surrounding environment, and the phonon oscillations of gold and silver nano-arrays were investigated. The cooling dynamics of gold nanoarrays on a glass substrate were found to be different from those of either colloidal nanodots in colloidal solution or films on glass substrate. The electron-phonon component of the electronic relaxation in the arrays was found to be longer than that in the dots or the films. The spatially isolated nanoarray particles experience a significantly different environment than the gold nanodots in solution, thus the long phonon-phonon component resulting from the coupling of particles to the medium, is not observed. The catalytic effectiveness of platinum nanoparticles for the hydrogenation of propene was investigated. The system with platinum particles was found to have a slightly lower activation energy than other systems in the literature. The effect of encapsulating the platinum particles in alumina was also investigated and it was found that the activation energy for the reaction was even lower. The effect of adding platinum, palladium, and rhodium particles to the proton exchange membrane of polymer electrolyte fuel cells, on the output power of the cells was also investigated. The effects of pH and precursor salt concentration, and particle composition were also investigated.

L’objectiu d’aquesta tesi és la preparació, la caracterització I l’aplicació de nous materials fotoactius basats en nanopartícules d’or (Au NPs). Degut a les seves interessants propietats òptiques, les potencials aplicacions d’ aquests nanomaterials estant sent intensament explorades en diversos camps d’estudi com la ciencia de materials, la nanomedicina I la nanotecnologia. En moltes d’aquestes aplicacions es crucial la interaccio del nanomaterial amb d’altres molècules, i per això es necessari induir l’apropament entre aquestes estructures i d’altres especies químiques. En aquesta tesi, s’ha explorat la utilització de la química supramolecular com a estratègia per afavorir aquesta aproximació i intentar millorar les aplicacions d’aquestes nanoestructures. Per dur a terme aquesta estrategia, s’han preparat derivats tiolats de ciclodextrines (CD) que s’han incorporat a la superfície de les Au NPs per tal de: i) millorar l’activitat fotocatalítica de les Au NPs en front de reaccions químiques ii) induir l’agregació i desagregació de Au NPs de forma controlada amb llum. En el primer cas, es va poder fotocatalitzar la reacció unimolecular d’isomerització de Z-estilbens amb Au NPs funcionalitzades amb B-CD de forma més eficient que amb Au NPs no funcionalitzades, però quan es van intentar aplicar aquests resultats a processos bimoleculars, Au NPs funcionalitzades amb y-CD no van proporcionar cap tipus de conversió en la reacció de dimerització d’antracens assajada. Pel que fa als estudis d’agregació, els nostres resultats posen de relleu la importància de tenir en compte les interaccions inespecífiques quan s’intenta desenvolupar nous sistemes a través d’associació supramolecular del tipus amfitrió-hoste. En conclusió, en la present tesi doctoral, s’ha demostrat el gran potencial que té la combinació de nanoestructures plasmòniques amb la química supramolecular per al desenvolupament de nous materials fotoactius amb propietats millorades, contribuint així al creixent coneixement en el camp de la nanociència.
The present thesis aimed at the preparation, characterization and application of new photoactive materials based on gold nanoparticles (Au NPs). Due to their interesting optical properties, the potential applications of these nanomaterials are being intensively explored in diverse fields of research like medicine, meterials science and technology. In many of these applications it is crucial the interaction between the nanomaterial and other molecules, and therefore it is necessary to induce the approximation between the nanomaterial and other chemical species. In this thesis we explored the utilization of supramolecular chemistry as an strategy to favor such approximation and try to enhance the potential applications of such nanostructures. For that, proper thiolated derivatives of the cyclodextrin (CD) family of supramolecular hosts have been prepared and subsequently incorporated onto the surface of Au NPs to: i) enhance the photocatalytic activity of Au NPs towards chemical reactions, ii) to induce the aggregation and disaggregation of Au NPs controlled with light. In the former case, B-CD-functionalized Au NPs were able to photocatalyze the isomerization of Z-stilbenes more efficiently than non-functionalized particles, but when trying to expand these results to bimolecular processes, y-CD-functionalized particles did not provide any conversion towards the selected reaction. Regarding the assembly studies, our results highlighted the importance of considering unspecific interactions when trying to develop new systems via specific host-guest association. In conclusion, in the present thesis we have demonstrated the great potential of combining plasmonic nanostructures with supramolecular chemistry to develop new photoactive materials with improved properties, contributing with our work to the increasing knowledge in the expanding field of the nanosicience.

Correct diagnosis of disease is essential in the effort to save and improve lives. Point of care (POC) diagnostics are in-vitro tests that assist in patient diagnosis and can be used at the location of patient care. POC diagnostics are easy to use and provide near-instant readouts allowing medical providers and patients to make rapid decisions about treatment. Increased access to POC testing is especially beneficial to low-income and low resource areas that cannot afford expensive lab testing. The World Health Organization (WHO) has outlined at least 113 diseases for which POC diagnostics are needed. Because of this, developing effective, efficient, and economical methods for creating new POC tests is essential. Work in section one of this thesis describes strategies by which new POC bio-diagnostics can be created. The use of oxidized cellulose as a vector for antibody immobilization was explored in several cellulose-based materials to provide quick, economical tests while still obtaining effective limits of detection when used to detect the pregnancy hormone Human Chorionic Gonadotropin (HCG) in a proof of concept study. The majority of these tests could detect as low as 100 ng/mL of HCG well below the clinical level necessary for detection at 2400 ng/mL. The use of a hand-powered syringe-based POC named the fast flow immunoassay (FFI) was tested for its ability to increase observable signal in a sandwich immunoassay by passing the sample through the test filter multiple times. 10 passes through the filter resulted in a signal approximately 17x more intense than a 1-hour dot-blot sandwich immunoassay. Both oxidized cotton and FFI systems can be used to develop new POC assays quickly and economically. Future use of these POC systems could help expand the availability of diagnostic testing to disadvantaged areas. Gold-based drugs have been used and investigated as medications multiple times throughout history to treat various diseases such as Rheumatoid arthritis, parasitic infections, and cancer. In the last few decades, gold nanoparticles have been used as drug delivery agents and catalysts for various reactions. Recently catalytic gold nanocrystals have been characterized for their ability to treat neurodegenerative diseases. Although these results were promising, much is still unknown about their mechanism of action. Section two of this thesis investigates potential molecular pathways that gold nanocrystals could be affecting, specifically the IL-6/Jak/STAT3 inflammation pathway and the Nrf2 antioxidant pathway. The gold nanocrystals we tested did not affect these pathways at physiologically obtainable concentrations. Additional work was done to characterize protein interactome or protein corona of gold nanocrystals. Preliminary proteomic characterization of this protein corona in fetal bovine serum (FBS) identified 118 potential interactors and classified those based on function and structure. Future work will need to be done to follow up on these identifications and to determine what mechanistic implications they may have.

We plan to form and characterize surface-attached catenane gold nanoparticles. The proposed catenane self-assembles when a pi-electron-rich bis(thiol)hydroquinone derivative (hereby referred to as the dithiol) threads through a pi-electron-deficient inorganic molecular square forming a charge-transfer complex in solution and then attaches itself to a particle via two gold-sulfur covalent bonds.In preparation of this goal, an inorganic molecular square had to be synthesized. We synthesized, recrystallized, and characterized a cationic, tetranuclear, Pd(II)-based macrocyclic square according to the procedures published by Stang2.Then various methods of synthesis and derivatization of gold nanoparticles were investigated. Using a two-phase method published in the literature, dodecanethiolderivatized nanoparticles were synthesized,8 and attachment of the dodecanethiol was confirmed by NMR, IR, and UV/Vis spectroscopy. After the confirmation of the model compound, the reaction scheme was scaled-down for the derivatization of the nanoparticle with the dithiol alone which will be one of the components that will form the proposed catenane.Upon the derivatization of the nanoparticle with the dithiol, there was great difficulty in dissolving the nanoparticles in any polar or non-polar solvent. This led us to believe that nanoparticles are cross-linking with each other and therefore not dissolving. However, the attachment of the dithiol to the nanoparticle was confirmed by infrared spectroscopy. To solve the cross-linking problem an exchange reaction was conducted between the dodecanethiol-derivatized gold nanoparticles and the dithiol in a modified procedure from the literature.18 Although a successful exchange was confirmed by infrared spectroscopy, the dithiol-derivatized gold nanoparticles were still not soluble in any suitable solvent.
Department of Chemistry

La synthèse de nanoparticules (NPs) d’or fonctionnalisées en phase aqueuse est encore aujourd’hui un enjeu majeur de la recherche dans le domaine des nanomatériaux. Depuis les travaux de J. Turkevich de 1951, la synthèse utilisant le citrate comme ligand et agent réducteur est la méthode de choix pour obtenir des NPs d'or. Cependant cette synthèse nécessite une étape supplémentaire de modification de surface par échange de ligand, pour pouvoir accrocher des molécules d’intérêt. Afin de simplifier la procédure, notre projet propose de synthétiser en une seule étape des NPs qui possèdent un groupement permettant une post-fonctionnalisation. La nouvelle voie de synthèse fait intervenir des composés bifonctionnels de la famille des 1-hydroxy-1,1-méthylène bisphosphonates (HMBP). Ainsi la base conjuguée de l'acide (1-hydroxy-1-phosphonopent-4-ènyl) phosphonique (HMBPène), qui possède une fonction éthylénique terminale nous a permis d'obtenir des dispersions de nanosphères de tailles contrôlées et nous avons pu rationaliser le mécanisme de synthèse utilisant ce type de molécules. Nous avons ensuite évalué plusieurs modalités de post-fonctionnalisation de notre nanoplateforme et validé une approche par chimie « Click » la via cycloaddition de composés tétrazine. En utilisant une nouvelle classe de HMBP couplés à une chaine polyéthylène glycol, des NPs stables en milieu physiologique ont pu être synthétisées selon le même modèle. Elles offrent également des possibilités de post-fonctionnalisation par couplage carbodiimide, que nous avons illustré par le couplage d'un fluorophore. Nous développons en dernière partie les résultats préliminaires sur deux types NPs d'or synthétisées à l'aide des HMBP pour des applications thérapeutiques
In the ever growing fields of nanoscience the control of the synthesis of gold nanoparticles (GNPs) owing to their large variety of applications has emerged as an important domain. Among all methodologies Turkevich-Frens synthesis using citrates that act as ligand and reducing agent remains a method of choice for the obtaining of water soluble GNPs. Nevertheless, in post-synthesis, citrates are often exchanged with other ligands to enhanced stabilization and allow further functionalisation. In our work we present a new class of bi-functional molecules (1-hydroxy-1,1-methylene bisphosphonates HMBP) that can both reduce Au(III) and act as an efficient stabilizer of the formed GNPs in water. The first size controlled GNPs “one pot” synthesis was achieved by using an alkene conjugated HMBP, the (1-hydroxy-1-phosphonopent-4-enyl)phosphonic acid (HMBPene). We moreover, rationalized the mechanism of the GNPs synthesis using this type of molecule. We then, evaluated several methodologies for the post-functionalization of our nanoplateform and developed a « Click » chemistry approach to nanoparticle coating by tetrazine cycloaddition. Other nanoplatforms were synthesized using pegylated hydroxyl methylene bisphosphonates. This new class of bisphosphonate coated GNPs showed an improved stability in biological media and brought reactive groups available for post-functionalization as well, illustrated by the coupling of a fluorescent dye. The last part of this was dedicated to our latest results on GNPs synthesis for biomedical applications with HMBP compounds

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2008.
Christoph J. Fahrni, Committee Member ; Mostapha A. El-Sayed, Committee Member ; Christopher W. Jones, Committee Member ; Marcus Weck, Committee Chair ; E. Kent Barefield, Committee Member.

Prostate cancer is the most common cancer in men. Many existing treatments for prostate cancer are often not completely effective and/or are invasive. Multimodal or combination therapy represents a promising new method to fight disease. Therefore, a combination of different therapeutic strategies may be the best alternative to improve treatment outcomes for prostate cancer. Photothermal therapy combined with gene and chemotherapy was proposed as a novel approach to treatment. In this work, photothermal therapy with gold nanoparticles and near infrared laser (NIR) irradiation, and gene therapy targeting heat shock protein 27 using antisense oligonucleotides (ASO), was investigated. Four types of small (<100nm), NIR absorbing gold nanoparticles (nanoshells, nanorods, core-corona and hollow nanoshells) were synthesized using wet chemical methods and characterized by transmission electron microscopy, dynamic light scattering and UV-vis spectroscopy. Their synthesis and properties were evaluated, to determine their feasibility as a photothermal agent for clinical applications. In vitro cellular uptake studies of the nanoparticles into prostate cancer cell lines, LNCaP and PC3, were measured using light scattering microscopy. The effect of ASO on hyperthermia of cancer cells was investigated using cell viability assays to determine if heat sensitization was possible. Photothermal treatment of the cancer cell lines using synthesized gold nanoparticles was evaluated and compared with commercially available Auroshell® particles. The effect of photothermal treatment and ASO in vitro was determined by measuring cell viability. A preliminary in vivo model study was performed to examine treatment conditions and heat generation. Small gold nanoshells (40nm) had good photothermal properties and the greatest cellular uptake, and were used in photothermal studies. Under 4W laser irradiation, an increase in temperature of 12°C and decrease in cell viability of up to 70% were obtained. Comparative work suggests that the 40nm gold nanoshells have a higher therapeutic efficiency than the larger Auroshell® particles. It is uncertain from the present study, if the addition of ASO can sensitize prostate cancer cells to hyperthermia. However, ASO treatment had a concentration dependent effect on cell viability, which could be useful to treatment goals. In vivo, localized high temperatures were generated with gold nanoparticles at low laser powers.

Thiolated ligands are known to form self-assembled monolayers on gold nanoparticles, and the self-organisation of these ligands provides a route towards nanoparticles with programmable and complex molecular structures. This body of work investigates the structures and chemical properties of ligand monolayers based on peptides and alkanethiol derivatives. We evaluate a series of published articles reporting the peculiar self-organisation of ligands into striated domains on the surface of nanoparticles, which was shown by scanning tunnelling microscopy (STM). Image analysis of the STM micrographs shows the stripe-like domains to be scanning artefacts, and our attempts to reproduce data on nanoparticle stability and cell entry give results conflicting with those published. Self-assembled monolayers made from peptides allow the use of peptide motifs to drive self-organisation. We investigate the effects of using an amyloidogenic sequence, CFGAILSS, in a monolayer. FTIR, 2DIR and solid state NMR reveal the presence of inter-peptide hydrogen bonding consistent with a parallel β-sheet structure, which is not seen in a monolayer made from the CALNN peptide. Fluorescently labelled peptide-capped gold nanoparticles were irradiated by a femtosecond laser pulse. The timings of the reaction dynamics of this ligand release were measured by splitting the laser beam and introducing a variable delay. These measurements show that this process is a hot electron mediated process. We suggest that such laser induced release measurements can provide some insights into the intermolecular interactions within the monolayer