Academic literature on the topic 'Halloysite nanoparticle'

The polymer nanocomposites of PEO-LiCF3SO3 based solid polymer electrolyte were prepared using two kinds of natural clays, which are halloysite nanotube (HNT) and montmorillonite (MMT) nanoparticle. Different contents (0, 1, 5 and 10wt %) of halloysite nanotube (HNT) and montmorillonite (MMT) nanoparticle were explored. Solid polymer electrolyte nanocomposite film was prepared by solution casting method. The ionic conductivity, crystallinity and thermal properties of solid polymer electrolyte membranes were studied by impedance spectroscopy, X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. It was found that HNT provided higher ionic conductivity for solid polymer electrolyte nanocomposite than what MMT did. The highest ionic conductivity at room temperature was found at 5% HNT as 2.068 x 10-5 S.cm-1. The ion-polymer interactions between PEO-LiCF3SO3 and natural clay nanoparticle were investigated by using Fourier transform infrared (FTIR) spectra. The PEO-LiCF3SO3-5%HNT showed good oxidative stability than PEO-LiCF3SO3 composite.

Copper nanoparticle supported halloysite nanotubes with a 15 nm lumen and 30 nm external diameterviasurface initiation reverse atom transfer radical polymerization were fabricated and showed good antibacterial activity againstEscherichia coli(E. coli).

Three different types of nanoparticles, 1D Cloisite 30B clay nanoplatelets, 2D halloysite nanotubes (HNTs), and 3D nanobamboo charcoals (NBCs) were employed to investigate the impact of nanoparticle shapes and structures on the material performance of polyvinyl alcohol (PVA) bionanocomposite films in terms of their mechanical and thermal properties, morphological structures, and nanomechanical behaviour. The overall results revealed the superior reinforcement efficiency of NBCs to Cloisite 30B clays and HNTs, owing to their typical porous structures to actively interact with PVA matrices in the combined formation of strong mechanical and hydrogen bondings. Three-dimensional NBCs also achieved better nanoparticle dispersibility when compared with 1D Cloisite 30B clays and 2D HNTs along with higher thermal stability, which was attributed to their larger interfacial regions when characterised for the nanomechanical behaviour of corresponding bionanocomposite films. Our study offers an insightful guidance to the appropriate selection of nanoparticles as effective reinforcements and the further sophisticated design of bionanocomposite materials.

In the nanocomposite, the dispersion and bonding properties of the nanoparticles at the interfaces were major factors that were related to the physical properties of the final product. Nanoparticle aggregation mainly occurs in the dispersion process between nanoparticles and a polymer. In addition, re-aggregation phenomenon generates by large amounts of pores during curing process. In this case, it was necessary to break the physical bonds, such as the attraction between the initial nanoparticles, and achieve a smooth chemical bonding with the polymer. In this study, the effect of halloysite nanotube (HNT) dispersion on the interfacial bonding was compared and analyzed in [Formula: see text] high temperature water environment over 30 days by adding 0.5 wt.% HNT to glass fiber reinforced plastic (GFRP) and basalt fiber reinforced plastic (BFRP). As a result, the HNT contributed to disturbing the moisture absorption rate. It has great effect on thinner lamination part. Moreover, the thicker the lamination, the less the HNT re-aggregation occurred on the curing process. This phenomenon showed a uniform dispersion in the entire laminate area. The weight recovery rate by moisture absorption was high in the HNT-glass fiber (GF), because structural relationship between HNT and GF are larger than in epoxy resin.

The surface of halloysite nanotubes (HNTs) was bifunctionalized with two ligands—folic acid and a fluorochrome. In tandem, this combination should selectively target cancer cells and provide a means for imaging the nanoparticle. Modified bi-functionalized HNTs (bi-HNTs) were then doped with the anti-cancer drug methotrexate. bi-HNTs were characterized and subjected to in vitro tests to assess cellular growth and changes in cellular behavior in three cell lines—colon cancer, osteosarcoma, and a pre-osteoblast cell line (MC3T3-E1). Cell viability, proliferation, and cell uptake efficiency were assessed. The bi-HNTs showed cytocompatibility at a wide range of concentrations. Compared with regular-sized HNTs, reduced HNTs (~6 microns) were taken up by cells in more significant amounts, but increased cytotoxicity lead to apoptosis. Multi-photon images confirmed the intracellular location of bi-HNTs, and the method of cell entry was mainly through caveolae-mediated endocytosis. The bi-HNTs showed a high drug loading efficiency with methotrexate and a prolonged period of release. Most importantly, bi-HNTs were designed as a drug carrier to target cancer cells specifically, and imaging data shows that non-cancerous cells were unaffected after exposure to MTX-doped bi-HNTs. All data provide support for our nanoparticle design as a mechanism to selectively target cancer cells and significantly reduce the side-effects caused by off-targeting of anti-cancer drugs.

Present PhD thesis aimed to investigate relatively unknown properties of halloysite nanoparticles, as well as to further examine HNTs as potential drug nanocarriers. NPs loading and release characteristics were studied using model active molecules: magnesium monoperoxyphthalate (MMPP), aspirin and epirubicin. The research was fulfilled with formation of complex multi-functional nanoarchitectures, which apart from ability to deliver incorporated drugs, showed the potential of controlled and sustain release of therapeutics, biocompatible and bioresorbable characteristics as well as potential targeting abilities. Great attention was dedicated to characterization of formed halloysite-based nanoarchitectures in qualitative as well as quantitative manner. Investigations performed in this thesis also faced the problem of exceeding dimensions of halloysite units, nanoparticles aggregation, poor loading capability and dose dumping effect. Subsequently, studies for trying to find a solution to these obstacles were undertaken. Fully characterized halloysite nanoconstructs were further examined in biological field, employing different cancer cell lines. Studies on pristine halloysite nanotubes: Physico-chemical and biological properties of halloysite nanoparticles were evaluated using microscopic techniques, spectroscopic analysis, surface studies regarding charge, porosity and wettability. The thermal and time-based examination of pristine halloysite was performed as well, showing stability of HNTs alumino-silicate skeletons up to ~400 ℃ and over a long period of time (2 years) at room temperature, however with a variable amount of incorporated water molecules. Biological performance of HNTs was determined in vitro in multiple cellular systems by toxicity, cellular uptake, colocalization and accumulation studies using [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] tetrazolium reduction (MTT) assay and set of microscopic techniques. Aiming to deeply characterize halloysite nanoparticles, the study proceeded with employment of non-standard techniques, as multiphoton microscopy that drove to discovery of novel NPs promising capabilities. It was revealed that halloysite is able to convert light to its second harmonic, at twice of the frequency (and therefore half of the wavelength) while using high intensity femtosecond pulsed laser. Halloysite Second Harmonic Generation (SHG) signal was detected over a broad wavelength range, showed stability over a long period of time, polarization properties and quadratic dependence on the intensity of incident light. The analysis also pointed out characteristic structure properties of the nanoparticle that is lack of the center of symmetry and the high crystalline structure organization. Among a wide spectrum of domains where discovered HNTs characteristics can be utilized (e.g. optoelectronics, biosensors), we have explored its application in alternative label-free bioimaging. The proposed multiphoton method of analysis showed advantages over the standard confocal microscopy, since e.g. nanoparticles did not have to be stained prior the analysis, thus no possible alterations of HNTs including size, surface chemistry and consequent cellular uptake were induced. Therefore, for the first time, halloysite nanotubes were exploited as imaging agents, taking advantage of their endogenous properties. Along the research it was revealed that the length of pristine HNTs and the strong aggregation limit their ability to pass intracellular membranes and thus minimize their effectiveness as drug nanocarriers. Therefore, efforts were devoted to the development of facile methodology to efficiently disperse and shorten HNTs units. Set of characterizations techniques, such as Scanning Electron Microscopy (SEM) analysis with size distribution profile and nitrogen adsorption Brunauer–Emmett–Teller (BET) method revealed that the applied ultrasonication procedure resulted with longest tubes breaking and favored obtaining HNTs below 300 nm in length (39.1 % to 76 % of the batch). The number of voids among the pristine nanoparticles when packing together (123–43 nm) greatly increased (total pore volume from 0.23 cm^3/g to 0.30 cm^3/g), meaning that the nanomaterial was efficiently disaggregated as well. In vitro internalization and colocalization studies by Scanning Electron and Multiphoton Microscopy demonstrated that the sonicated halloysite were preferentially internalized via macropinocytosis within 60 min and accumulated in the perinuclear region within 24 h. Halloysite application in nanomedicine: To study halloysite potential as a carrier for drugs, we set up the preparation and characterization of hybrid nanoconstructs with model molecules such as magnesium monoperoxyphthalate hexahydrate (MMPP), a negatively charged oxidizing agent, aspirin, an anti-inflammatory drug and epirubicin, a chemotherapeutic. Chosen molecules were incorporated with 3.5 %wt, 1.1 %wt and 5.1 %wt capacity, respectively for MMPP, aspirin and epirubicin. Loading efficiency (LE) improvement was achieved through the choice of the right solvent (1), enhancement of electrostatic forces between nanoparticle and the drug, via functionalization of HNT surfaces with an active linker (2), as well as NPs structure modification leading to increase of inner lumen volume (3). Specifically, the use of water: EtOH (7:3 v/v) as a solvent instead of water, increased MMPP loading capacity up to 6.1 %wt. Poor incorporation of aspirin was improved by enhancing electrostatic forces between deprotonated aspirin molecules and modified HNTs inner walls with amine-rich organosilane. It was also demonstrated that by enlarging volume of the NPs cavities, more molecules could be loaded. To do that, pristine HNTs were treated with 0.1M aqueous solution of NaOH, which resulted in an exfoliation of bilayers located inside the lumen. At the same time, outer surface of the halloysite tubules was preserved. As a consequence of the base treatment, halloysite cylinders gained more volume in the inner cavity as concluded from Transmission Electron Microscopy (TEM) and nitrogen adsorption BET analysis. The actual test on loading capacity using model MMPP molecule revealed increased MMPP incorporation from 6.1 % wt to 11.7 %wt. To evaluate if the activity of MMPP as an oxidizing agent remained unchanged upon incorporation and release from halloysite, and therefore to demonstrate the inactivity of the inorganic skeleton towards carried molecule, we tested HNT-MMPP nanoconstruct with selective fluorescent 1,3-diphenylisobenzofuran (DPBF) probe. Among available modifications of halloysite nanoparticles via covalent bond, the surface silanization is commonly recognized as one of the most efficient and widespread reaction while HNT manipulation. Up to date, the halloysite nanotubes functionalized with silanes have been used as a support for versatile applications in diverse scientific domains, including enzymes immobilization and biosensing. Willing to explore the halloysite functionalization with those active linkers, we have performed grafting reactions with representative organosilanes carrying the same backbone, while varying in the content of terminal groups, namely (3-aminopropyl)triethoxysilane (APTES), 3-(2-aminoethylamino)propyldimethoxymethylsilane (AEAPS), (3-mercaptopropyl)trimethoxysilane (MPS). Successful HNTs surfaces functionalization with organosilanes was demonstrated by means of quantitative thermogravimetric analysis (TGA) that allowed to estimate the loading capacity of organosilanes to be of 5.7 %wt for APTES, 7.4 %wt for AEAPS and 0.7 %wt for MPS. In addition, particular attention was dedicated to further quantify incorporated organosilane (APTES), since only one method has been so far reported, that is the destructive thermogravimetric analysis (TGA). For this reason, we set up and optimized a Fmoc based method by performing the following three reactions: (i) synthesis of “APTES-Fmoc” molecule; (ii) halloysite functionalization with “APTES-Fmoc”; and (iii) time-dependent Fmoc deprotection reaction in piperidine: EtOH (20 %) solution, resulting in dibenzofulvenepiperidine adduct (DBF-pip) formation. The UV-visible spectroscopic analysis of supernatant solutions demonstrated that the DBF-pip deprotection from halloysite support needs 5 h to be completed. Therefore, it was evidenced that HNT Fmoc-method showed strong coherence with already existing TGA method (± 2 % measurement error) and stood out as a valuable complementary technique for quantification of silane grafting on HNTs surface with additional low-cost and nondestructive advantages. The possibility of using halloysite nanotubes as a non-viral gene delivery nanosystem for therapeutic treatments was studied as well. Aiming to immobilize plasmid DNA (pDNA) based on the Green Fluorescent Protein (GFP) on HNTs support, the layer-by-layer (LbL) adsorption technique was applied. Obtained multi-component assembly was characterized qualitatively by monitoring variation in nanoparticle physico-chemical properties including surface charge, mass weight, presence of functional groups at each step of hybrid formation, which confirmed the successful nanoarchitecture formation. In order to additionally demonstrate the presence of GFP encoding plasmid (pGFP) on HNTs, the nanoarchitecture was treated with the bovine pancreatic deoxyribonuclease (DNase) enzyme, which induced the pGFP degradation through hydrolytic cleavage of phosphodiester linkages in DNA backbone. Thus, as expected, such nanoform with deposed genetic material varied in physico-chemical properties, expressing similar ones of the nanoconstruct without pGFP plasmid attached. The biological efficiency of HNTs-pGFP nanosystem was checked by means of Multiphoton microscopy. Successful pGFP plasmid transportation into cells was verified by detection of GFP expression, which yielded fluorescence emission. The interesting and innovative aspect of this case study was the simultaneous observation of GFP expression via fluorescence detection, and colocalization of halloysite nanoparticles by their SHG signal. This study proved that halloysite can act as an efficient carrier of genetic material, since free pGFP cannot be internalized by same cells, due to its large size and significant charge. Drug-loaded halloysite nanoconstructs (HNT-MMPP, HNT-APTES-aspirin) were also examined on the drug release kinetics, demonstrating long-term MMPP leakage taking 18 days and aspirin over 60 min. However, great drug liberation into the solvent of release was observed in the first minutes, followed by desired sustained drug release. The initial molecule liberation (dose dumping effect) is known to entail local toxicity. Herein, trying to find a solution to this problem, the coating of HNTs with the natural collagen polymer was investigated. Two strategies for the loading with this biopolymer were studied: (i) formation of a covalent bond between collagen and APTES-modified HNTs using glutaraldehyde cross-linker or (ii) noncovalent adsorption of collagen into pores of NPs. Immobilization of collagen on the surface of HNTs was estimated to be 3.7 %wt (i) and 1.8 %wt (ii). Other supplementary characterization techniques, such as water contact angle, ζ–potential analysis, Kaiser test, ultraviolet and visible (UV-vis) spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR) were in accordance and proved nanoarchitectures formation. For the visualization purpose of HNTs encapsulated in collagen shell, the innovative characterization technique was implemented, namely 3D Multiphoton microscopy. It revealed that the biopolymer coating blocked the entrances of the hollow tubes thus, entrapping the drug in NPs. Mimicking tumor microenvironment (TME), the pH and/or enzyme triggered release was performed. LC-Mass analysis revealed that the collagen coating slowed down the release of aspirin from HNTs. Studies on cells showed that the collagen coating on HNTs is biocompatible and cell viability assay performed on 5637 urinary bladder and HeLa cervical cancer cell lines demonstrated the sustained release of the entrapped epirubicin chemotherapeutic agent in the biological context. Industrial application of halloysite: During a stage in BASF SE (USA), validation and properties enhancement of halloysite-based products potentially manufacturable in the company on an industrial scale were studied. In particular, the research was dedicated to aspects such as the pH-dependent dispersion behavior of halloysite nanotubes and iron coarse impurities removal from bulk samples. Applied methodologies and set of physico-chemical characterization techniques generated and revealed decreased percentage of present aggregates, maintained low shear viscosity under the threshold value and increased solids loading capacity in final halloysite-based products. Conclusions: In conclusion, PhD studies here reported contributed to the exploration of halloysite nanotubes for their application in the nanomedical and industrial fields. The investigations suggest a facile manipulation and functionalization of HNTs, useful for properties modification and improved NPs performance. Specifically, the study was directed toward formation of multi-functional nanocarriers with controlled drug delivery and release properties, together with targeting and imaging abilities. Moreover, the research was completed with halloysite-related technology transfer to the BASF SE, for the purpose of knowledge increase in the halloysite-field and bringing forward placement of halloysite-based products on the market. The systematic study on HNTs characterization and application performed in this PhD thesis will contribute to the development of HNTs as a high performance structural and functional material.

My Ph.D. dealt mainly with the study of halloysite nanotubes (HNT), and their interaction with molecules and nanoparticles as potential for potential applications either in biomedicine or in catalysis. A minor part of my Ph.D work was dedicated to the preparation and characterization of Ceria nanoparticles stabilized with polymers of different charge, to investigate, in collaboration with the group of prof Della Torre and Binelli, their effect on various animal and bacterial models relative to their possible toxic effects especially in the aquatic environment. I started the first part of my thesis by introducing the clay material HNT. HNT is a unique natural nanomaterial composed of double-layered aluminosilicate with a hollow tubular structure in the micro range. A preliminary literature survey revealed that HNT, due to their physical and chemical features, could be suitable for many application fields like medicine and catalysis (Chapter 1). We started our aim by synthesizing some HNT adducts possibly suitable for hyperthermia applications by selectively load superparamagnetic iron oxides (SPIONs) into the inner lumen of HNT. The magnetic properties of the loaded SPIONs did not change after their trapping inside the HNT lumen. The SPION-in-HNT nanocomposite was synthesized through the pre-modification of the HNT inner lumen such that it becomes suitable to be suitable to load the apolar SPION as synthesized by thermal decomposition method without a further step of ligand exchange (Chapter 2). To extend the loading to another kind of NP for hyperthermia applications, we tried to load gold nanoparticles. The gold NPs can be synthesized in various shapes; we synthesized spherical and star shapes of gold for our purpose. Gold can be loaded inside the inner lumen in the studied shapes, but the low concentration of gold suspension hampered a massive loading into the HNT lumen. (Chapter 3). The second part of the work with Halloysites was devoted to the preparation and characterization of HNT adducts with luminescent molecules able to act as photosensitizers for photodynamic therapy (PDT). For this purpose, we were interested in loading perfluorinated porphyrin, in their non-coordinated- and Zn-coordinated form, inside the lumen of HNT. The release of the photosensitizer by the inner lumen was slowed down compared to the release of the perfluorinated drugs adsorbed in the outer surface of HNT. (Chapter 4). To use HNT as a dual vector for drug delivery, we synthesized HNT-Ru photosensitizer. The photosensitizer was covalently bonded to the silica part of the outer surface of HNT, leaving the inner lumen free for potentially an extra loading with another drug. The photophysical properties of synthesized nanocomposite were then tested (Chapter 5). Finally, concerning HNT, we aimed to synthesize a new synthetic Au-Pt nanoparticle supported over HNT with different Au-to-Pt molar ratios via a sol immobilization method for catalytic purposes. The synthesized catalyst showed that the activity toward hydrogenation of C=O of cinnamaldehyde increased with increasing the molar ratio of Au/Pt (Chapter 6). Unfortunately, the product potentially useful for biomedical purposes were not tested at least at cellular level, and this lack to the work was essentially due to the COVID-19 pandemic situation that slowed down a lot of collaboration especially with biologist collaborators. The last part of my thesis was devoted to synthesizing nanoceria and covering it with natural polymer available in the aquatic system as alginate and chitosan. Ceria NPs surrounded by both Alginate and Chitosan showed no acute toxicity effects at the average environmental concentration level of the two tested natural macromolecules (Chapter 7).

The formation processes of epoxy nanocomposites with carbon (nanotubes, graphene, and graphite), metal-containing, and aluminosilicate (montmorillonite and halloysite tubes) fillers are considered. A high reactivity of epoxy groups and a thermodynamic miscibility of epoxy oligomers with many substances make it possible to use diverse curing agents and to accomplish curing reactions under various technological conditions. Epoxy nanocomposites are designed to realize to the same extent the unique functional properties of nanoparticles: electric, magnetic, optical, chemical, and biological. The mutual effect of both a matrix and nanoparticles on the composite formation is discussed.

The formation processes of epoxy nanocomposites with carbon (nanotubes, graphene, and graphite), metal-containing, and aluminosilicate (montmorillonite and halloysite tubes) fillers are considered. A high reactivity of epoxy groups and a thermodynamic miscibility of epoxy oligomers with many substances make it possible to use diverse curing agents and to accomplish curing reactions under various technological conditions. Epoxy nanocomposites are designed to realize to the same extent the unique functional properties of nanoparticles: electric, magnetic, optical, chemical, and biological. The mutual effect of both a matrix and nanoparticles on the composite formation is discussed.

In this work, we report a simple fabrication method for metal nanoparticles and nanorods on halloysite supports. Silver nanorods of 15 nm diameter were synthesized by thermal decomposition of silver acetate within halloysite lumen. Nanorods had crystalline nature with [111] axis oriented ∼ 68° from the halloysite tubule main axis. Linear arrays from gold, iron, cobalt and palladium nanoparticles on halloysite external surface were also synthesized by chemical and thermal reduction method. Samples were analyzed by high-resolution transmission electron microscopy and field-emission scanning electron microscopy. These in situ syntheses offer a simple method for large scale fabrication of metallic nanorods and core-shell ceramic nanocomposites, which can be used as antimicrobial additives in plastic composites, nanoelectronic and optical materials with biocompatibility and environmentally friendly. Antimicrobial thin films were prepared based on halloysite-silver nanocomposites and tested on E. Coli and S Aureus bacterial culture. Antibacterial performance of the nanocomposite material was superior to the other conventional antimicrobial additives (silver doped bioactive glasses and carbon nanotubes). Radiation protection coatings based on fabricated nanocomposite materials is under development.