Relevant bibliographies by topics / MODIFIED HYDROGELS

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  2. Dissertations / Theses
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Academic literature on the topic 'MODIFIED HYDROGELS'

Author: Grafiati
Published: 11 September 2023

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Journal articles on the topic "MODIFIED HYDROGELS"

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Tang, Yuanhan, Junjie Ding, Xun Zhou, Xintao Ma, Yi Zhao, Qiyu Mu, Zixu Huang, Qian Tao, Fangjie Liu, and Ling Wang. "Injectable hydrogels of enzyme-catalyzed cross-linked tyramine-modified gelatin for drug delivery." Australian Journal of Chemistry 76, no. 2 (February 28, 2023): 88–99. http://dx.doi.org/10.1071/ch22188.

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Enzymatically catalyzed cross-linking is a hydrogel fabrication method that generally is considered to have lower cytotoxicity than traditional chemical cross-linking methods. In order to optimize the properties of injectable hydrogels and expand their applications, an enzyme-catalyzed cross-linked injectable hydrogel was designed. The tyramine-modified gelatin (G-T) was formed into a stable injectable hydrogel by the combination of horseradish peroxidase (HRP) and hydrogen peroxide (H2O2) catalysis. 1H NMR spectroscopy was used to demonstrate the successful modification of gelatin by tyramine. The surface morphology of the prepared hydrogels was characterized jointly by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Rheological tests demonstrated the tunable mechanical strength, formation kinetics, shear thinning and good self-recovery properties of the hydrogels. In addition, the hydrogels can be formed into various shapes by injection. The hydrogel network structure is complex and interlaced, as such it is suitable to encapsulate drugs for controlled release. The drug release from the prepared hydrogels followed the Peppas–Sahlin model and belonged to Fickian diffusion. This study constructed injectable hydrogels through the enzyme-catalyzed cross-linking of modified gelatin and applied the hydrogels for drug release, which is expected to expand the application in biomedical fields.
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Huang, Anshan, Yehong Chen, and Chaojun Wu. "Wound Dressing Double-Crosslinked Quick Self-Healing Hydrogel Based on Carboxymethyl Chitosan and Modified Nanocellulose." Polymers 15, no. 16 (August 13, 2023): 3389. http://dx.doi.org/10.3390/polym15163389.

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The use of hydrogels in wound dressings, which is pivotal for effective wound treatment, has been widely applied to diverse medical wound conditions. However, formulating natural hydrogels that combine robust strength and self-healing capabilities is a significant challenge. To overcome this, we successfully designed a natural nanocellulose self-healing hydrogel that can quickly self-heal and restore the complete hydrogel structure after injury to fill the injured area and protect the wound from external damage. Our study utilized modified natural polymer carboxymethyl chitosan (CMC), hydrazide-modified carboxymethyl cellulose nanofibers (HCNF), and cellulose nanocrystals modified by dialdehyde (DACNC) to fabricate the hydrogel. The amides containing more amino groups and HCNF in CMC can be used as cross-linking nodes, and the high aspect ratio and specific surface area of DACNC are favorable for the connection of many active hydrogels. The hydrogel is crosslinked by the dynamic imide bond and hydrazone bond between the amino group of CMC, the amide of HCNF, and the aldehyde of DACNC and has a double network structure. These connections can be readily reassembled when disrupted, enabling fast self-healing of hydrogels within five minutes. Moreover, HCNF and DACNC were incorporated as nano-reinforced fillers to bolster the hydrogel’s strength while preserving its high liquid absorption capacity (381% equilibrium swelling rate).
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Han, Xiaoman, Guihua Meng, Qian Wang, Lin Cui, Hao Wang, Jianning Wu, Zhiyong Liu, and Xuhong Guo. "Mussel-inspired in situ forming adhesive hydrogels with anti-microbial and hemostatic capacities for wound healing." Journal of Biomaterials Applications 33, no. 7 (November 22, 2018): 915–23. http://dx.doi.org/10.1177/0885328218810552.

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All kinds of commercially available wound dressings are clinically used as fleshly obstacles and therapeutic materials in opposition to microbial incursion. Few researches focused on effective-bleeding and anti-bacteria at the same time. In order to better solve this problem, two hydrogels were synthetized in this study. One is phosphate buffer solution-activated dopamine-modified-γ-poly glutamic acid (PBS-PD) hydrogel, the other one is cirsium setosum extracts-activated dopamine-modified-γ-poly glutamic acid (CSE-PD) hydrogel. The two hydrogels are prepared by applying an enzyme-catalyzed crosslinking means in the presence of horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). The chemical structures were characterized through 1H-NMR and FT-IR. In conclusion, both PBS-PD and CSE-PD hydrogels exhibit superior tissue adhesion properties, and remarkable anti-infection quality. In addition, these two hydrogels manifest prominent hemostatic efficiency. The bio adhesion performance can achieve 30 kPa, meanwhile the CSE-PD hydrogels show good germicidal properties, and the antibacterial rate can reach 98%. The hydrogels could reduce blood loss without any obvious side effect, and present a new prospect in the field of hemostasis rapidly.
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Zhou, Jian, Fu Lu, and Zhengwei Wu. "Effects of a plasma jet on electrochemical properties of silk fibroin hydrogel doped with graphene oxide." Polymers and Polymer Composites 30 (January 2022): 096739112211465. http://dx.doi.org/10.1177/09673911221146599.

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This study modified hydrogels prepared from silk fibroinand graphene oxideby injecting plasma into the silk. The SF-GO hydrogels, modified by plasma jet with different discharge time (30, 90, and 150 s) and working gases (argon, air, helium), undergo electrochemical AC impedance spectrum tests. After hydrogel modification with the plasma of any working gas, the impedance in the very low frequency (10−2∼100 Hz) decreased with a longer plasma discharge time. In the very low frequency, the sequence of impedance change is Ar group <air group ≈ He group <empty. The electric capacity of the hydrogel showed an increasing trend with those modified by argon plasma and a decreasing trend for those hydrogels modified by air and helium plasma. The sequence of electric capacity change is Ar group >empty >air group >He group. Fourier transform infrared spectrum, and X-ray diffraction spectrum showed a reduction of β-fold structure and graphene oxide content in SF-GO hydrogels modified by plasma.
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Hejčl, Aleš, Jiří Růžička, Kristýna Kekulová, Barbora Svobodová, Vladimír Proks, Hana Macková, Kateřina Jiránková, et al. "Modified Methacrylate Hydrogels Improve Tissue Repair after Spinal Cord Injury." International Journal of Molecular Sciences 19, no. 9 (August 22, 2018): 2481. http://dx.doi.org/10.3390/ijms19092481.

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Methacrylate hydrogels have been extensively used as bridging scaffolds in experimental spinal cord injury (SCI) research. As synthetic materials, they can be modified, which leads to improved bridging of the lesion. Fibronectin, a glycoprotein of the extracellular matrix produced by reactive astrocytes after SCI, is known to promote cell adhesion. We implanted 3 methacrylate hydrogels: a scaffold based on hydroxypropylmethacrylamid (HPMA), 2-hydroxyethylmethacrylate (HEMA) and a HEMA hydrogel with an attached fibronectin (HEMA-Fn) in an experimental model of acute SCI in rats. The animals underwent functional evaluation once a week and the spinal cords were histologically assessed 3 months after hydrogel implantation. We found that both the HPMA and the HEMA-Fn hydrogel scaffolds lead to partial sensory improvement compared to control animals and animals treated with plain HEMA scaffold. The HPMA scaffold showed an increased connective tissue infiltration compared to plain HEMA hydrogels. There was a tendency towards connective tissue infiltration and higher blood vessel ingrowth in the HEMA-Fn scaffold. HPMA hydrogels showed a significantly increased axonal ingrowth compared to HEMA-Fn and plain HEMA; while there were some neurofilaments in the peripheral as well as the central region of the HEMA-Fn scaffold, no neurofilaments were found in plain HEMA hydrogels. In conclusion, HPMA hydrogel as well as the HEMA-Fn scaffold showed better bridging qualities compared to the plain HEMA hydrogel, which resulted in very limited partial sensory improvement.
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Dinić, Ana, Vesna Nikolić, Ljubiša Nikolić, Snežana Ilić-Stojanović, Stevo Najman, Maja Urošević, and Ivana Gajić. "Modified Sulfanilamide Release from Intelligent Poly(N-isopropylacrylamide) Hydrogels." Pharmaceutics 15, no. 6 (June 16, 2023): 1749. http://dx.doi.org/10.3390/pharmaceutics15061749.

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The aim of this study was to examine homopolymeric poly(N-isopropylacrylamide), p(NIPAM), hydrogels cross-linked with ethylene glycol dimethacrylate as carriers for sulfanilamide. Using FTIR, XRD and SEM methods, structural characterization of synthesized hydrogels before and after sulfanilamide incorporation was performed. The residual reactants content was analyzed using the HPLC method. The swelling behavior of p(NIPAM) hydrogels of different crosslinking degrees was monitored in relation to the temperature and pH values of the surrounding medium. The effect of temperature, pH, and crosslinker content on the sulfanilamide release from hydrogels was also examined. The results of the FTIR, XRD, and SEM analysis showed that sulfanilamide is incorporated into the p(NIPAM) hydrogels. The swelling of p(NIPAM) hydrogels depended on the temperature and crosslinker content while pH had no significant effect. The sulfanilamide loading efficiency increased with increasing hydrogel crosslinking degree, ranging from 87.36% to 95.29%. The sulfanilamide release from hydrogels was consistent with the swelling results—the increase of crosslinker content reduced the amount of released sulfanilamide. After 24 h, 73.3–93.5% of incorporated sulfanilamide was released from the hydrogels. Considering the thermosensitivity of hydrogels, volume phase transition temperature close to the physiological temperature, and the satisfactory results achieved for sulfanilamide incorporation and release, it can be concluded that p(NIPAM) based hydrogels are promising carriers for sulfanilamide.
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Zielińska, Aleksandra, Piotr Eder, Lucas Rannier, Juliana C. Cardoso, Patrícia Severino, Amélia M. Silva, and Eliana B. Souto. "Hydrogels for Modified-release Drug Delivery Systems." Current Pharmaceutical Design 28, no. 8 (March 2022): 609–18. http://dx.doi.org/10.2174/1381612828666211230114755.

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Abstract: Hydrogels for the modified-release drug delivery systems are a continuously growing area of interest for the pharmaceutical industry. According to the global market, the profit resulting from the use of polymers in this area is projected to reach $31.4 million by 2027. This review discusses the recent advances in and perspectives of hydrogel in drug delivery systems for oral, parenteral, nasal, topical, and ophthalmic delivery. The search was conducted, in January 2021, in an extensive database to identify studies published from January 2010 to December 2020. We described the main characteristic of the polymers to obtain an ideal hydrogel for a specific route of administration and the formulations. It was concluded that the hydrogels are useful to decrease the number of doses and side effects, promote adhesion of patient, and enhance the bioavailability of the drugs, thus improving the safety and efficacy of the treatment.
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Sukhanova, T. V., A. A. Artyukhov, I. A. Prudchenko, A. C. Golunova, M. A. Semenikhina, M. I. Shtilman, and E. A. Markvicheva. "Delta-sleep inducing peptide entrapment and release from polymer hydrogels based on modified polyvinyl alcohol." Biomeditsinskaya Khimiya 59, no. 1 (January 2013): 65–75. http://dx.doi.org/10.18097/pbmc20135901065.

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The aim of the study was to entrap delta-sleep inducing peptide (DSIP) in cross-linked poly(vinyl alcohol)-based hydrogels of different structures and to evaluate peptide release kinetics from these hydrogels using an in vitro model. Isotropic and macroporous hydrogels on the basis of poly(vinyl alcohol) acrylic derivative (Acr-PVA) as well as macroporous hydogels containing epoxy groups which were synthesized by copolymerization of this monomer with glycidyl methacrylate. The isotropic hydrogels were fabricated at positive temperatures while the macroporous hydrogels (cryogels) were prepared at the temperatures below zero. The peptide was entrapped into macroporous modified PVA hydrogels by addition of a peptide solution on previously fabricated matrices, while into PVA-GMA hydrogels containing epoxy groups peptide immobilization was carried out by incubation of hydrogel matrices in the peptide solution. In the case of isotropic hydrogels the peptide was added into the polymer mixture at a hydrogel formation reaction. The peptide release kinetics was studied by incubation of hydrogels in PBS (pH 7.4), in physiological solution (0.9% NaCl) and in water. DSIP concentration in supernatants was determined by phase-reverse HPLC. DSIP release from the macroporous PVA hydrogel after 30 min incubation was 74, 70 и 64% in water, PBS and 0.9% NaCl, relatively, and it was completed in 3 hs. From the isotropic hydrogel the release neither peptide nor products of its degradation was not observed even after 48 hs of incubation. For freshly prepared hydrogel the release kinetics was as follows: 27 and 78% in 30 and 33 hs, relatively. In the case of the lyophilized hydrogel samples the peptide release was 63% in 30 min incubation while drying patterns at room temperature for 3 days resulted in significant peptide loss because its structure damage.
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Astudillo-Ortiz, Esteban, Pedro S. Babo, Rui L. Reis, and Manuela E. Gomes. "Evaluation of Injectable Hyaluronic Acid-Based Hydrogels for Endodontic Tissue Regeneration." Materials 14, no. 23 (November 30, 2021): 7325. http://dx.doi.org/10.3390/ma14237325.

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Dental pulp tissue engineering (TE) endeavors to regenerate dentin/pulp complex by combining a suitable supporting matrix, stem cells, and biochemical stimuli. Such procedures foresee a matrix that can be easily introduced into the root canal system (RCS) and tightly adhere to dentin walls to assure the dentin surface’s proper colonization with progenitor cells capable of restoring the dentin/pulp complex. Herein was investigated an injectable self-setting hyaluronic acid-based (HA) hydrogel system, formed by aldehyde-modified (a-HA) with hydrazide-modified (ADH), enriched with platelet lysate (PL), for endodontic regeneration. The hydrogels’ working (wT) and setting (sT) times, the adhesion to the dentine walls, the hydrogel’s microstructure, and the delivery of human dental pulp cells (DPCs) were studied in vitro. Hydrogels incorporating PL showed a suitable wT and sT and a porous microstructure. The tensile tests showed that the breaking point occurs after 4.3106 ± 1.8677 mm deformation, while in the indentation test after 1.4056 ± 0.3065 mm deformation. Both breaking points occur in the hydrogel extension. The HA/PL hydrogels exhibited supportive properties and promoted cell migration toward dentin surfaces in vitro. Overall, these results support using PL-laden HA injectable hydrogels (HA/PL) as a biomaterial for DPCs encapsulation, thereby displaying great clinical potential towards endodontic regenerative therapies.
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Vitale, Mattia, Cosimo Ligorio, Ian P. Smith, Stephen M. Richardson, Judith A. Hoyland, and Jordi Bella. "Incorporation of Natural and Recombinant Collagen Proteins within Fmoc-Based Self-Assembling Peptide Hydrogels." Gels 8, no. 5 (April 21, 2022): 254. http://dx.doi.org/10.3390/gels8050254.

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Hydrogel biomaterials mimic the natural extracellular matrix through their nanofibrous ultrastructure and composition and provide an appropriate environment for cell–matrix and cell–cell interactions within their polymeric network. Hydrogels can be modified with different proteins, cytokines, or cell-adhesion motifs to control cell behavior and cell differentiation. Collagens are desirable and versatile proteins for hydrogel modification due to their abundance in the vertebrate extracellular matrix and their interactions with cell-surface receptors. Here, we report a quick, inexpensive and effective protocol for incorporation of natural, synthetic and recombinant collagens into Fmoc-based self-assembling peptide hydrogels. The hydrogels are modified through a diffusion protocol in which collagen molecules of different molecular sizes are successfully incorporated and retained over time. Characterization studies show that these collagens interact with the hydrogel fibers without affecting the overall mechanical properties of the composite hydrogels. Furthermore, the collagen molecules incorporated into the hydrogels are still biologically active and provide sites for adhesion and spreading of human fibrosarcoma cells through interaction with the α2β1 integrin. Our protocol can be used to incorporate different types of collagen molecules into peptide-based hydrogels without any prior chemical modification. These modified hydrogels could be used in studies where collagen-based substrates are required to differentiate and control the cell behavior. Our protocol can be easily adapted to the incorporation of other bioactive proteins and peptides into peptide-based hydrogels to modulate their characteristics and their interaction with different cell types.
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Dissertations / Theses on the topic "MODIFIED HYDROGELS"

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Pinardag, Fatma Esra. "Modified Acrylic Hydrogels As Controlled Release Systems." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607362/index.pdf.

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In this study, pH-sensitive poly(acrylamide-co-acrylic acid) hydrogels were synthesized as controlled release systems in the presence of N,N-methylene bisacrylamide as crosslinker and ammonium persulfate as initiator. A set of hydrogels were used in the form they were prepared. One set of hydrogels were prepared as porous networks by incorporating sodium chloride into the reaction medium and then leaching of it after the completion of polymerization reaction. Two sets of hydrogels were modified by argon-plasma at different discharge powers. Hydrogels were characterized by 13C-NMR, XPS, SEM, ATR-FTIR, ESR as well as equilibrium degree of swelling (EDS) and contact angle measurements. Prepared hydrogels were loaded with a model antibiotic, ciprofloxacin-HCl (CPFX), and in-vitro release of CPFX from hydrogel matrices were examined in buffer solutions of varying pH values. There are two factors determining the release rates of CPFX
one is the pH-dependent solubility of CPFX and the other is EDS of the hydrogel samples. For porous samples drug loading and release rates were higher when compared to the control samples and CPFX solubility dominated over release kinetics. Plasma treatment resulted in prolonged release rates in acidic medium.
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Lu, Xing. "Controlled Release of Cyclosporine A from Hydrophobically-modified Hydrogels." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1386631060.

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Gustafsson, Carla Astrid. "Modified polyethylene glycol hydrogels for growth factor delivery and controlled tissue invasion." Master's thesis, Faculty of Health Sciences, 2019. http://hdl.handle.net/11427/31068.

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The prevalence of cardiovascular disease and myocardial infarction-induced heart failure has risen significantly over recent years, emphasising the need for new, effective therapeutic strategies. A promising alternative approach is the cardiac delivery of potentially cardioprotective and regenerative growth factors from biomaterial scaffolds. One hydrogel system that has promise in this area is an injectable enzymatically degradable polyethylene glycol (PEG) hydrogel. Two modifications aimed at further optimising this system as a regenerative medicine scaffold were explored. Firstly, the covalent addition of heparin into the PEG backbone was assessed for its ability to stimulate angiogenesis by assessing the controlled release of basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and placental growth factor 2 (PlGF-2), and also assaying endothelial cell sprouting in an in vitro 3D spheroid angiogenesis assay. The second modification involved overlaying an increasingly hydrolytic degradability on top of the enzymatically degradable background of the hydrogel. The potential of this modification to regulate the rate of hydrogel replacement by invading tissue was assessed in the 3D spheroid assay and a subcutaneous implant study in a rat model. The covalent coupling of heparin was found to substantially increase the rate of release of bFGF, VEGF and PlGF-2 over 20 days by 23%, 42% and 19%, respectively, relative to nonheparinised PEG hydrogels (p<0.01). A 3D spheroid-based angiogenesis assay was modified for use in quantifying endothelial cell sprouting in PEG hydrogels. bFGF and VEGF were shown to elicit a significant increase (2.3 – 2.4-fold increase) in average cumulative sprout lengths relative to that seen in the control spheroids (p<0.01). However, PlGF-2 did not stimulate a significant response (1.4-fold increase, p=NS). In follow up studies with heparinised hydrogels, it was found that the 3D angiogenesis was not rigorously established and ways forward are discussed. Enzymatically degradable PEG hydrogels that retained their enzymatic degradability with increasing levels of potential for hydrolysis were formed by increasing the proportion of PEGacrylate (PEG-Ac) and correspondingly decreasing the portion of PEG-vinyl sulfone (PEG-VS) monomers. PEG-Ac forms hydrolytically unstable bonds with the peptide crosslinker whilst 4 PEG-VS forms stable linkages. This approach was shown through swelling studies to be capable of generating a range of hydrolytic degradation rates. Sprouting of endothelial cells from PEG hydrogel embedded spheroids was shown to increase as the PEG-AC concentration increased. Importantly, the rate of tissue invasion in vivo was also shown to be positively correlated with the PEG-Ac concentration. The increased utility of these hydrogels to act as delivery vehicles for therapeutic agents, through covalent coupling of heparin, is promising for their use as regenerative medicine scaffolds. Additionally, so is the ability to finely tune tissue invasion by manipulating their hydrolytic degradability.
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Tuesca, Anthony D. Lowman Anthony M. "Synthesis, characterization, and application of polyethylene glycol modified insulin for oral delivery using complexation hydrogels /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2715.

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Davila, Ramos Johanna. "Syntheses and uses of modified polyelectrolytes for therapeutic hydrogels and films with controlled and selective protein adsorption." Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAF005/document.

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La première partie de cette thèse est dédiée à la modification de polyélectrolytes pour former des films de multicouche de polyélectrolytes (PEM) ayant des propriétés d’adhésion de protéine et de cellules bien contrôlées et modifiables par étirement. L’acide polyacrylique a été modifié avec des groupes latéraux phosphorylcholine (PC) à des taux de 25 % (PAA-PC) ou avec des chaînes oligo(éthylène oxyde) terminées par la biotine : (EO)nBiotine (n = 0, 3, 9 et 18) avec de taux de modification de 1, 5, 10 ou 25 %. Des PEM incorporant ces polymères lient spécifiquement la streptavidine et repoussent tout autre protéine. Les propriétés d’adsorption et la sélectivité de ces PEM ont été mesurées par microbalance à quartz. Sur un substrat de PDMS étirables, on a construit des PEM terminés par un PAA portant des RGD recouvert par deux couches contenant PAA-PC. Au repos, seuls les PC sont exposés et inhibent l’adhésion cellulaire ; sous étirement, les groupes RGD sous-jacents sont exposés et déclenchent l’adhésion de fibroblastes.La deuxième partie est consacrée à l‘étude d’acide polyméthacrylique modifié hydrophobiquement avec des chaînes alkyle liées par des esters à la chaîne principale. 3 chaînes différentes ont été greffées : -C12H25 ; -C18H35 et C4H8-OOC- C11H23 avec des taux de 1, 5 and 10 %. Ces polymères sont associatifs et forment des hydrogels dans des tampons physiologiques pour des taux de modifications de 5% et des concentrations supérieures à 4% en poids. Ces gels ont été caractérisés par des mesures rhéologiques. Leur incubation avec des lipases provoque une baisse de leur viscosité, interprétable par une coupure des esters. Quand les gels faits à partir du PAA-C12 sont incubés avec une culture de Pseudomonas aeruginosa, la viscosité baisse également, ce qui montre que les chaînes sont également coupées in vivo
The first part of this thesis is dedicated to the modification of polyelectrolytes to form polyelectrolyte films with controlled and stretch responsive cell and protein adsorption properties. Poly(acrylic acid) (PAA) was modified with side phosphorylcholine groups (PC) at rates of 25 % or with oligo(ethylene oxide) chains ended by biotin ((EO)nBiotin, (n =0, 3, 9 and 18) at 1, 5, 10 and 25 % modification rates. Polyelectrolytes multilayer films (PEM) containing these polyelectrolytes bind selectively streptavidin but repel all other proteins. The adsorption properties and selectivity were measured by quartz crystal microbalance. On a stretchable PDMS substrate, we have built PEM ended by PAA bearing RGD, covered by two PAA-PC layers on the top. Under rest, only the PC groups are exposed and prevent cell adhesion; when the film is stretched, the underlying RGD groups are exposed, and trigger adhesion of fibroblasts.The second part was consecrated to the study of poly(methacrylic acid) hydrophobically modified with alkyl chains connected through an ester moiety to the main chain. Three different chains were grafted -C12H25; -C18H35 and -C4H8- OOC-C11H23 with a rate of 1, 5 and 10 %. These polymers associate in water and form hydrogels in physiological buffer, for modification rates higher than 5 % and polymer concentrations higher than 4 wt. %. The gels were characterized by rheology. Their incubation with lipases resulted in a decrease of their viscosity, which could be interpreted by the cleavage of the hydrophobic side chains, by rheological tests. When the gels with PAA-C12 were incubated with a culture of Pseudomonas aeruginosa, their viscosity decreased, which shows that alkyle chains are also cleaved in vivo
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Huang, Henry. "Exploring New Therapeutic Strategies for Osteoarthritis: From Genetic Manipulation of Skeletal Tissues to Chemically-modified Synthetic Hydrogels." eScholarship@UMMS, 2017. https://escholarship.umassmed.edu/gsbs_diss/919.

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Osteoarthritis (OA), a degenerative disease of articular joints, is the leading cause of chronic disability in the US and affects more than a third of adults over 65 years old. Due to the obesity epidemic and an aging population, the prevalence of OA is expected to rise in both young and old adults. There are no disease modifying OA drugs. Therefore, providing any treatment options that delay the onset or progression of OA is highly desirable. The scope of this dissertation examines two different strategies to promote translational therapies for OA. The first approach investigated whether Smad ubiquitin regulatory factor 2 (Smurf2), an E3 ubiquitin ligase, could be a potential therapeutic target for OA. The second approach examined the incorporation of small chemical residues to enhance the physical and bioactivity of a bioinert scaffold for cartilage tissue repair. Overexpression of Smurf2 in chondrocytes was shown to accelerate spontaneous OA development in mice. We hypothesized that reduced Smurf2 expression could slow the progression of OA and enhance the performance of cells for cartilage repair. By performing surgical destabilization of the medial meniscus (DMM) on Smurf2-deficient mice, loss of Smurf2 was shown to mitigate OA changes in young mice but this protection diminished in older mice. Assessment of Smurf2-deficient chondrocytes in vitro revealed an upregulation of chondrogenic genes compared to wild-type; however, these differences were not seen at the protein level, deterring its potential use for cell-based therapies. During the course of this study, new insights about how age and sex affects different joint compartments in response to DMM surgery were also uncovered. These results broadened existing understanding of DMM-induced OA in mice but also questioned the validity of such a model to identify disease modifying targets that are translatable to OA in humans with advanced age. Due to a lack of innate repair mechanisms in cartilage, damage to cartilage increases the risk of developing OA early. Tissue engineering provides a unique strategy for repairing damaged cartilage by delivering cells in a well-controlled environment that can promote the formation of neotissue. We hypothesized that synthetic chemical residues could enhance the mechanical properties of a bioinert scaffold and promote matrix production of encapsulated chondrocytes. Covalent incorporation of small anionic or zwitterionic chemical residues in a polyethylene glycol-based hydrogel improved its stiffness and resistance to fluid flow, however, the resulting physical environment can also exert a dominant negative effect on matrix production of encapsulated chondrocytes. These results suggest that modulating the biosynthesis of chondrocytes with biochemical signals requires a concurrent reduction in any conflicting mechanotransduction signaling, emphasizing the importance of a degradable system to promote new cartilage formation. In summary, this dissertation establishes Smurf2 as a modulator of OA progression but implies that other factors such as age or protein(s) with redundant Smurf2 functions may play a role in limiting its effect as a therapeutic target. This work also reveals fundamental biology about how chondrocytes behave in response to physical and chemical cues in their microenvironment, which will aid in the design of better scaffolds for cartilage tissue engineering.
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Desprez, Valérie. "Caractérisations, applications et modélisation d'électrodes modifiées par des hydrogels : laponite-oligosilsesquioxanes(-enzyme)." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10108.

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Ce memoire est consacre a la caracterisation, aux applications et a la modelisation cinetique d'electrodes modifiees par des hydrogels de laponite expansee par des oligosilsesquioxanes et fonctionnalisee par des especes electrocatalytiques (microparticules de metaux nobles, mediateurs redox, enzymes). Les etudes physico-chimiques et electrochimiques de ce nouveau materiau hybride d'electrode ont mis en evidence l'intercalation des oligosilsesquioxanes et l'existence d'une micro-porosite induite susceptible d'etre conservee en milieu organique. La stabilite des films obtenus ainsi que leur propriete d'echange d'ions offrent de larges potentialites d'application qui ont ete demontrees par plusieurs exemples en electrocatalyse (hydrogenation electrocatalytique) et en electroanalyse (biocapteurs amperometriques). En particulier, l'immobilisation de la polyphenol oxydase (ppox) permet l'elaboration d'un capteur sensible aux composes phenoliques aussi bien en milieux aqueux qu'en milieu organique. Les performances analytiques de ce capteur, tant en sensibilite, temps de reponse qu'en seuil de detection, comptent parmi les meilleures jusqu'ici decrites pour de tels systemes. Enfin, la modelisation cinetique du systeme electroenzymatique catechol/ppox qui met en jeu dans son fonctionnement une regeneration electrochimique du substrat de l'enzyme, a permis de rationaliser le processus d'amplification electroenzymatique responsable des limites de detection extremement basses de ce type de capteur. L'ensemble de ces etudes nous a ainsi permis de proposer une structure mesoporeuse de l'hydrogel enzyme-laponite expansee et de quantifier les modes de transport et d'amplification electroenzymatique.
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Kazan, Samar [Verfasser]. "Enzymatic Bioelectrodes Based on Carbon Nanotubes Modified Redox Hydrogels for Enhanced Output Current and Long Term Stability of Enzymatic Biofuel Cells / Samar Kazan." München : Verlag Dr. Hut, 2017. http://d-nb.info/1126295779/34.

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Ahmad, Hajira Fatima. "Cryopreservation effects on a pancreatic substitute comprised of beta cells or recombinant myoblasts encapsulated in non-adhesive and adhesive alginate hydrogels." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/48968.

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For clinical translation of a pancreatic substitute, long-term storage is essential, and cryopreservation is a promising means to achieve this goal. The two main cryopreservation methods are conventional freezing and vitrification, or ice-free cryopreservation. However, as both methods have their potential drawbacks for cryopreservation of a pancreatic substitute, they must be systematically evaluated in order to determine the appropriate method of cryopreservation. Furthermore, previous studies have indicated benefits to encapsulation in 3-D adhesive environments for pancreatic substitutes and that adhesion affects cell response to cryopreservation. Thus, the overall goal of this thesis was to investigate cryopreservation effects on model pancreatic substitutes consisting of cells encapsulated in non-adhesive and adhesive 3-D alginate hydrogels. Murine insulinoma betaTC-tet cells encapsulated in unmodified alginate hydrogels were chosen as the model pancreatic substitute in a non-adhesive 3-D environment. Murine myoblast C2C12 cells, stably transfected to secrete insulin, encapsulated in partially oxidized, RGD-modified alginate hydrogels were chosen as the model pancreatic substitute in a 3-D adhesive environment. With respect to cryopreservation effects on intermediary metabolism of betaTC-tet cells encapsulated in unmodified alginate, results indicate that relative carbon flow through the tricarboxylic acid cycle pathways examined is unaffected by cryopreservation. Additionally, insulin secretory function is maintained in Frozen constructs. However, vitrification by a cryopreservation cocktail referred to as DPS causes impairment in insulin secretion from encapsulated betaTC-tet cells, possibly due to a defect in late-stage insulin secretion. Results from Stable C2C12 cells encapsulated in RGD vs. RGE-alginate indicate that up to one day post-warming, cell-matrix interactions do not affect cellular response to cryopreservation after vitrification or freezing. Although there are differences in metabolic activity and insulin secretion immediately post-warming for DPS-vitrified RGD-encapsulated Stable C2C12 cells relative to Fresh controls, metabolic activity and insulin secretion are maintained at all time points assayed for Frozen constructs. Overall, due to results comparable to Fresh controls and simplicity of procedure, conventional freezing is appropriate for cryopreservation of betaTC-tet cells encapsulated in unmodified alginate or Stable C2C12 cells encapsulated in partially oxidized, RGD-modified alginate.
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Gruberová, Eliška. "Gelace hydrofobizovaného hyaluronanu." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-449414.

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This diploma thesis deals with hyaluronan modified by palmitoyl and its gelation. Gels were created from palmitoyl hyaluronan with molecular weight 216 kDa and degree of substitution 11 % in concentrations 15 and 20 g dm-3 in water and concentrations 10, 15, 20 g dm-3 in NaCl and TSB. Also gel from palmitoyl hyaluronan with molecular weight 35 kDa and degree of substitution 10 % in concentrations 20, 30 g dm-3 in NaCl was created. Gels were investigated concerning medical applications. Gels were rigid and had very good properties, which was confirmed by rheology. The physical properties (pH, water content) of gels and stability were investigated. On the grounds of the MTT test, three methods of cell incorporation were suggested. Gels are nontoxic, biocompatible, and biodegradable with nontoxic degradation products and that is why they are excellent aspirants for use in biomedicine.
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Books on the topic "MODIFIED HYDROGELS"

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Davies, Megan Louise. Modified hydrogel matrices in fibre optic sensors. Birmingham: Aston University. Department of Chemical Engineering and Applied Chemistry, 1989.

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Striegler, Karl. Modified Graphitic Carbon Nitrides for Photocatalytic Hydrogen Evolution from Water. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-09740-0.

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Lee, Nim. Characteristics of a modified flotation cell in the removal of hydrogen sulfide. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1992.

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Willey, David Benjamin. The investigation of the hydrogen storage properties of metal hydride electrode alloy surface modified with platinum group metals. Birmingham: University of Birmingham, 1999.

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T.W.R.* Giles. Hydrodynamic and kinetic studies of modified flotation cell hydrogen sulphide scrubbing technology. 1988.

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Striegler, Karl. Modified Graphitic Carbon Nitrides for Photocatalytic Hydrogen Evolution from Water: Copolymers, Sensitizers and Nanoparticles. Springer Vieweg. in Springer Fachmedien Wiesbaden GmbH, 2015.

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Modified Graphitic Carbon Nitrides for Photocatalytic Hydrogen Evolution from Water: Copolymers, Sensitizers and Nanoparticles. Spektrum Akademischer Verlag GmbH, 2015.

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Book chapters on the topic "MODIFIED HYDROGELS"

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Walter, Johanna-Gabriela. "Aptamer-Modified Hydrogels." In Advances in Biochemical Engineering/Biotechnology, 147–68. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/10_2021_166.

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Akiyama, Yoshikatsu, and Teruo Okano. "On-Off Switching Properties of ultra thin Intelligent Temperature-Responsive Polymer Modified Surface." In Hydrogels, 179–97. Milano: Springer Milan, 2009. http://dx.doi.org/10.1007/978-88-470-1104-5_14.

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Feng, J., and S. Qian. "Nanosilica-Modified Hydrogels Encapsulating Bacterial Spores for Self-healing Concrete." In Lecture Notes in Civil Engineering, 67–73. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-3330-3_9.

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AbstractMicrobially induced calcium carbonate precipitation is effective in achieving self-healing of concrete cracks when the bacteria are well protected in concrete with a high pH and dense microstructure. Calcium alginate hydrogels are appropriate for encapsulating bacteria in concrete due to the mild environment with rich moisture in the hydrogels. Nevertheless, the low alkaline tolerance and breakage ratios of the hydrogels after concrete cracking restrict their applications in concrete. To address these problems, nanosilica was doped into calcium alginate hydrogels with encapsulated bacterial spores to react with the Ca(OH)2 surrounding hydrogels in concrete. Due to the modification by nanosilica, the bond of the hydrogels with cement matrix was enhanced as needle-like C–S–H was generated at the interface after hydration for 7 days. Moreover, the urease activity of the encapsulated spores in the modified hydrogels was higher than that in plain hydrogels after submersion in saturated Ca(OH)2 solution or simulated concrete solution for 7 days. Therefore, it can be concluded that nanosilica holds promise for modifying hydrogels to improve the effectiveness of encapsulated bacterial spores for self-healing of concrete.
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Lindblad, Margaretha Söderqvist, Olof Dahlman, John Sjöberg, and Ann-Christine Albertsson. "Modified Galactoglucomannans from Forestry Waste-water for Films and Hydrogels." In Polysaccharide Materials: Performance by Design, 185–98. Washington DC: American Chemical Society, 2009. http://dx.doi.org/10.1021/bk-2009-1017.ch010.

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Simionescu, Cristofor I., Monica Leanca, and Ioan I. Negulescu. "Surface Heparinization of Poly(ethylene terephthalate) Films Modified with Acrylic Hydrogels." In ACS Symposium Series, 229–37. Washington, DC: American Chemical Society, 1988. http://dx.doi.org/10.1021/bk-1988-0364.ch017.

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Kumar, Sushant. "Modified Coal Gasification Process for Hydrogen Production." In Clean Hydrogen Production Methods, 55–66. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-14087-2_4.

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Kumar, Sushant. "Modified Steam Methane Reformation Methods for Hydrogen Production." In Clean Hydrogen Production Methods, 31–54. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-14087-2_3.

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Elias, Liju, and Sheik Muhammadhu Aboobakar Shibli. "Surface-Modified Carbon Nanotubes for Hydrogen Storage." In ACS Symposium Series, 151–73. Washington, DC: American Chemical Society, 2022. http://dx.doi.org/10.1021/bk-2022-1425.ch007.

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Alexeeva, O. K., S. Yu Alexeev, B. L. Shapir, and M. N. Tulskii. "Modified Tubular Catalytic Membrane Reactor for Hydrogen Production from Hydrocarbons." In Hydrogen Materials Science and Chemistry of Metal Hydrides, 339–47. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0558-6_32.

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Striegler, Karl. "Introduction and Objective." In Modified Graphitic Carbon Nitrides for Photocatalytic Hydrogen Evolution from Water, 1–2. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-09740-0_1.

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Conference papers on the topic "MODIFIED HYDROGELS"

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Cram, Sandra, Hugh Brown, Geoffrey M. Spinks, Dominique Hourdet, and Costantino Creton. "Hydrophobically modified acrylamide-based hydrogels." In Smart Materials, Nano-, and Micro-Smart Systems, edited by Alan R. Wilson. SPIE, 2004. http://dx.doi.org/10.1117/12.582229.

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Bignotti, Fabio, Luciana Sartore, and Gloria Spagnoli. "A versatile method for obtaining hydrophobically modified hydrogels." In 9TH INTERNATIONAL CONFERENCE ON “TIMES OF POLYMERS AND COMPOSITES”: From Aerospace to Nanotechnology. Author(s), 2018. http://dx.doi.org/10.1063/1.5045961.

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Fu, Guoguang, and Winston Soboyejo. "Modified Poly (N-Isopropylacrylamide) Hydrogels for Drug Delivery." In ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19491.

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Thermo-responsive hydrogel can change their swelling behavior and drug release characteristics in response to environmental temperature [1–5]. Poly(N-isopropylacrylamide) (PNIPA) hydrogel undergoes a phase transition when the temperatue is lower than a lower critical solution temperature (LCST) of ∼32°C in aqueous solution [8], and drug release profiles in PNIPA hydrogel can be controlled by the alternation of their solution temperatures.
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Usta, Aybala, and Ramazan Asmatulu. "Synthesis and Analysis of Electrically Sensitive Hydrogels for Advanced Drug Delivery Systems." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51120.

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Electrically sensitive polyvinyl alcohol (PVA) hydrogels loaded with methotrexate (MTX) were prepared via a solution casting process, and characterized by attenuated total reflectance (ATR) spectrometry. In order to determine if the hydrogels were electro-sensitive or not, bending tests were conducted on the sulfoacetic acid modified hydrogels. It was observed that the prepared samples into strip forms started bending towards the cathode, and this bending was reversible when the polarity of the applied voltage was changed. The drug release study was performed on the MTX-loaded hydrogel strips placed in a sodium chloride (NaCl) solution under three different voltages (e.g., 0V, 5V, 10V, and 20V). Subsequently, the solutions were collected every five minutes in order to determine the drug release behaviors of the hydrogels using an ultraviolet-visible (UV-Vis) spectrophotometer. The test results showed that sulfoacetic acid (SA)-modified PVA hydrogels possess electrical sensitive behavior and kept their electric sensitivity for a long period of time. Also, the results confirmed that the control drug release could be achieved under different electrical voltages.
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Erikson, Isaac E., Cindy Chung, Jason A. Burdick, and Robert L. Mauck. "Hyaluronic Acid Macromer Concentration Influences Functional MSC Chondrogenesis in Photocrosslinked MSC-Laden Hydrogels." In ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-193096.

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Intrinsic repair of articular cartilage is poor, and so numerous tissue engineering strategies have been developed for producing functional cartilage replacements. Photopolymerizable methacrylated hyaluronic acid (MeHA) hydrogels have been developed as a potential hydrogel that possesses the distinct advantage of being biologically relevant as well as easily modified to generate a range of hydrogel properties [1]. To date, optimization of this hydrogel has been carried out by adjusting macromer molecular weight, concentration, and extent of methacrylation. Recent studies using MeHA hydrogels with auricular chondrocytes have shown that adjustments in these parameters can have significant impact on cell viability and construct maturation. [1, 2].
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Vicente, Adam, Zachary McCreery, and Karen Chang Yan. "Printability of Hydrogels for Hydrogel Molding Based Microfluidic Device Fabrication." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-11545.

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Abstract Microfabrication-free methods have been developed in recent years for fabricating microfluidic devices to enable the applications of microfluidic devices to a broader range. Our group has been working on developing a process for fabricating electrospun fiber embedded microfluidic devices by integrating hydrogel molding (HGM) and electrospinning (ES), and the feasibility of this integrated method has been demonstrated through our initial study. Recently, we have modified an extrusion based 3D printer kit to deposit hydrogels and form microchannels. Agarose has been used for our previous studies owning to its temperature dependent gelation. In this study, we examined the feasibility of using gelatin gel as an alternative material for hydrogel molding. Gel materials with various concentrations were examined via printability assessments; and optimal gel materials were identified. Upon completion of pattern printing, the samples were then encapsulated in polydimethylsiloxane (PDMS) and cured; formed microchannels were then characterized via micrographic image analysis. The results show that three gels, 2% w/v agarose gel, 7.5% w/v gelatin gel, and a mixture of 2% w/v agarose gel and 7.5% w/v gelatin gel (1:1 ratio), yield consistent printed patterns and form consistent microchannels subsequently.
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Guterl, Clare Canal, Tyler Kim, Steven B. Nicoll, and James C. Iatridis. "Genipin-Crosslinked Fibrin Hydrogels Modified With Collagen or Fibronectin as an Annulus Fibrosus Sealant." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80913.

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Low back pain (LBP) affects 80% of all adults at some point in their lives [1], and is often associated with intervertebral disc (IVD) degeneration, therefore, restorative solutions are of high importance. The IVD is composed of an outer ring of annulus fibrosus (AF) containing the pressurized nucleus pulposus (NP) center. NP replacement approaches and IVD procedures such as discectomy or discography involve rupture of the AF tissue for diagnosis or repair purposes. Even small defects to the outer AF can accelerate IVD degeneration [2]. Current closure techniques are limited to sutures and offer little in the way of tissue replacement or mechanical restoration of the AF [3]. A genipin crosslinked fibrin hydrogel offers some promise as an adhesive AF sealant [4]. Fibrin is FDA approved and genipin is a plant based chemical crosslinker with low cytotoxicity used with a variety of materials including fibrin for articular cartilage engineering [5]. Genipin crosslinked fibrin is a tunable material with comparable mechanical properties to native AF tissue and although cells remained viable on the gel, the relatively slow proliferation and presence of abnormal cells with rounded morphology motivated further optimization. To improve cytomorphology, key extracellular matrix proteins, collagen and fibronectin, were added to the formulation. It was hypothesized that the addition of these proteins would maintain the mechanical properties of this gel while improving cell morphology and viability. Several additional analyses were included to further characterize this gel including push-out strength, degradation and contraction tests.
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Markovic, Maja, Vesna Panic, Julijana Tadic, and Rada Pjanovic. "EFFECT OF CROSSLINKER AMOUNT ON HYBRID HYDROGELS SWELLING AND DRUG RELEASE." In 1st INTERNATIONAL Conference on Chemo and BioInformatics. Institute for Information Technologies, University of Kragujevac, 2021. http://dx.doi.org/10.46793/iccbi21.125m.

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Targeted drug delivery is powerful tool which researchers use to achieve safer and more efficient therapy of many diseases, including various types of cancer. Many chemotherapeutics are poorly water- soluble, so their encapsulation and targeted delivery remain quite challenge. Hydrogels based on poly(methacrylic acid) (PMAA) are widely investigated for targeted drug delivery due to their pH sensitivity, non-toxicity and biocompatibility. Still, due to the PMAA highly hydrophilic nature, PMAA can only be used for encapsulation and targeted delivery of water-soluble drugs. Our previous research was directed towards overcoming this limitation: PMAA was modified with amphiphilic protein – casein and poorly-water soluble model drug – caffeine – was encapsulated (PMAC). Present study is focused on investigation how variation of amount of one of the most important hydrogels network parameter such as crosslinker affect PMAC swelling properties and caffeine release. The group of hybrid hydrogels – PMAC – was synthesized with various amount of crosslinker: 0.4mol%, 0.8mol%, 1.6mol% and 3.2mol% with respect to methacrylic acid. Swelling behavior of hybrid hydrogels and caffeine release was investigated in two environments which simulated human stomach and intestines. Obtained results showed that targeted delivery of poorly water-soluble model drug was achieved and that its release can be prolonged up to 24h. Also, kinetic of poorly water-soluble drug release can be easily modified only by changing crosslinker amount. PMAC hybrid hydrogels have huge potential for targeted delivery of poorly water-soluble active substances.
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Kim, Minwook, Isaac E. Erickson, Jason A. Burdick, George R. Dodge, and Robert L. Mauck. "Differential Chondrogenic Potential of Human and Bovine Mesenchymal Stem Cells in Agarose and Photocrosslinked Hyaluronic Acid Hydrogels." In ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19461.

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Articular cartilage has a limited regenerative capacity, and there exist no methodologies to restore structure and function after damage or degeneration. This has focused intense work on cell-based therapies for cartilage repair, with considerable literature demonstrating that chondrocytes in vitro and in vivo can generate cartilage-like tissue replacements. However, use of primary cells is limited by the amount and quality of autologous donor cells and tissue. Multipotential mesenchymal stem cells (MSCs) derived from bone marrow offer an alternative cell source for cartilage tissue engineering. MSCs are easily accessible and expandable in culture, and differentiate towards a chondrocyte-like phenotype with exposure to TGF-β [1]. For example, we have shown that bovine MSCs undergo chondrogenic differentiation and mechanical maturation in agarose, self-assembling peptide, and photocrosslinkable hyaluronic acid (HA) hydrogels [2]. HA hydrogels are particularly advantageous as they are biologically relevant and easily modified to generate a range of hydrogel properties [3]. Indeed, bovine MSCs show a strong dependence of functional outcomes on the macromer density of the HA gel [4]. To further the clinical application of this material, the purpose of this study was to investigate functional chondrogenesis of human MSCs in HA compared to agarose hydrogels. To carry out this study, juvenile bovine and human MSCs were encapsulated and cultured in vitro in HA and agarose hydrogels, and cell viability, biochemical, biomechanical, and histological properties were evaluated over 4 weeks of culture.
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Najafi Moghadam, Peyman, Hanieh Rezazadeh, and Kamran Kazemi. "Synthesis and Characterization of Melamine-modified Hydrogels: The Study of Dye Removal from Aqueous Solutions." In The 21st International Electronic Conference on Synthetic Organic Chemistry. Basel, Switzerland: MDPI, 2017. http://dx.doi.org/10.3390/ecsoc-21-04721.

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Reports on the topic "MODIFIED HYDROGELS"

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Dr. Ahn. Hydrogen Storage in metal-modified single-walled carbon nanotubes. Office of Scientific and Technical Information (OSTI), April 2004. http://dx.doi.org/10.2172/828225.

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Hosokawa, Ketia. Hydrogen Storage Properties of Lithium Aluminohydride Modified by Dopants and Mechanochemistry. Office of Scientific and Technical Information (OSTI), January 2002. http://dx.doi.org/10.2172/804166.

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Calef, D. F. Molecular models for the intercalation of hydrogen molecules into modified graphites. Office of Scientific and Technical Information (OSTI), December 1995. http://dx.doi.org/10.2172/212469.

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Hosokawa, Keita. Hydrogen Storage Properties of Lithium Aluminohydride modified by dopants and mechanochemistry. Office of Scientific and Technical Information (OSTI), January 2002. http://dx.doi.org/10.2172/795180.

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Hosokawa, Keita. Hydrogen Storage Properties of Lithium Aluminohydride Modified by Dopants and Mechanochemistry. Office of Scientific and Technical Information (OSTI), January 2002. http://dx.doi.org/10.2172/798523.

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Graville. L51764 Hydrogen Cracking in the Heat-Affected Zone of High-Strength Steels-Year 2. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), March 1997. http://dx.doi.org/10.55274/r0010170.

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During year 1 of this project a test to evaluate the sensitivity of the heat affected zone (HAZ) to hydrogen cracking was developed. This was in response to a need for a test which provided unambiguous results in contrast to existing test methods which often led to difficulties in interpretation. For example, WIC tests usually cracked in the weld metal rather than the HAZ and therefore did not produce a clear indication of the sensistivity of the HAZ. The new test involves a machined notch which can be placed in the HAZ thus forcing crack initiation to occur in the desired region. A further advantage of the new test is that it is quantitative with each test specimen providing a measure of the sensitivity of the HAZ in that test. Existing tests are usually of the crack/no-crack type requiring a series of tests at different preheats to be carried out in order to establish a critical value. This is an expensive, time-consuming approach. The new test measures the deflection to first load drop (normally the onset of significant cracking) when the welded specimen is loaded in bending. It was also shown during the first year of the project that the simple geometry of the test lends itself to easy analysis enabling the stress/strain distribution to be calculated by finite element analysis. The quantitative measurement of susceptibility in the test enabled the cracking of more complex welds to be predicted on the basis of a local critical hydrogen model. The objective of the work was to extend the notched bend test to the evaluation of weld metal sensitivity to hydrogen cracking. The experiments were designed to determine whether the test could discriminate between two different weld metals and to study the effects of reducing hydrogen content. In addition, finite element analysis of the weld metal test was carried out and finite difference analysis used to predict the local hydrogen concentration. This work modifies the notched bend test, developed for evaluating the sensitivity of the heat affected zone (HAZ), to allow the evaluation of weld metal. The results showed that weld metal could readily be evaluated, with the test discriminating among weld metals of different composition and hydrogen contact. Finite element analysis was undertaken and showed that for the two weld metals tested, cracking occurred at the same local stress when the hydrogen content was the same, despite differences in strength. A finite model was used to calculate the distribution of hydrogen as a function of aging time. Although the general trends were confirmed by the experimental measurements of hydrogen content, there was considerable scatter attributed to the small hydrogen volumes measured.
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Patil, Bhimanagouda S., Ron Porat, G. K. Jayaprakasha, and K. N. C. Murthy. Optimization of Postharvest Storage Conditions to Maintain Fruit Quality and Health Maintaining Properties of Grapefruit. United States Department of Agriculture, January 2010. http://dx.doi.org/10.32747/2010.7613879.bard.

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Antioxidant activity of fruits is gaining wide interest among consumers due to its importance in counteracting oxidative stress, free radicals and preventing DNA damage. Oxygen radical absorbance capacity (ORAC) assay is one of the commonly used assays to measure the antioxidant activity, which is based on hydrogen atom transfer mechanism. Furocoumarins present in grapefruit are reported to have antiproliferative activity, induce GST activity, inhibit biofilm formation and increase bioavailability of drugs. In the present project ORAC values were measured of Star Ruby grapefruit undergone ethylene degreening treatment, cold storage and temperature conditioning treatment, and modified atmosphere packaging which were stored at different temperatures for prolonged period. In addition, furocoumarins were quantified in Star Ruby grapefruits from cold storage and conditioning experiment conducted in Israel. Conditioning treatment is practiced prior cold storage to reduce chilling injury in grapefruits during cold storage for prolonged period. Levels of 6,7-dihyrdoxy bergamottin decreased during storage period in all three treatments.
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Bauza, Rodrigo, and Daniel Olsen. PR-179-20200-R01 Improved Catalyst Regeneration Process to Increase Poison Removal. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), June 2021. http://dx.doi.org/10.55274/r0012106.

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In this work, the details of catalyst poison deposition are studied, and new catalyst restoration methods are explored. Lubrication oil makes its way through the combustion chamber and into the exhaust system, depositing poisons onto the catalyst and degrading catalyst performance. To estimate the degradation rate of the units and to find the best restoration method, two identical alumina-platinum oxidation catalysts were used in a dual setting, combining a field degradation engine and a laboratory testing engine. In order to find the best restoration process, the combination of both baking and washing is tested with poison deposition and performance analysis, and a hydrogen reduction is tested for the restoration of the platinum crystallites. The units were aged, then restored with the industry-standard washing procedure, then aged again until reaching non-compliance with emissions standards, and then restored a second time with a modified version of the industry-standard washing process that combines baking and washing. There is a related webinar.
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Bruce and Yushanov. L52056 Enhancement of PRCI Thermal Analysis Model for Assessment of Attachments. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 2004. http://dx.doi.org/10.55274/r0010436.

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Welds made onto in-service pipelines tend to cool at an accelerated rate as the result of the flowing content"s ability to remove heat from the pipe wall. These welds are therefore likely to have high heat-affected zone (HAZ) hardness values and to be susceptible to hydrogen cracking. The use of thermal analysis modeling allows welding parameters (i.e., required heat input levels) to be selected based on anticipated weld cooling rates. Both the Battelle model and the recently developed PRCI Thermal Analysis Model for Hot Tap Welding assume that the pipe material is the most susceptible material being welded. Some attachments (e.g., hot formed fittings, etc.) have a significantly less favorable chemical composition (i.e., higher carbon equivalent level) than the pipe material. As a result, for some in-service welding applications, the attachment material may be more susceptible to cracking than the pipe material. Modifications were made to the finite-element solver of the PRCI model to enable hardness prediction in both the pipe and attachment material. The source code for the modified finite-element solver was provided to Technical Toolboxes - PRCI"s commercial partner for software marketing and distribution. The required modifications to the user interface were also developed. In addition, user interface modifications required to rectify a number of faults that were identified and to improve the user interface were also developed. The incorporation of these enhancements and improvements, which are described herein, will require modification by Technical Toolboxes of the Visual Basic-based version of the software that is currently being marketed (V4.2.1). Following the incorporation of these enhancements and improvements, validation trials should be carried out.
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[Studies of hydrogen-hydrogen and carbon-sulfur bond cleavage; Lewis acid modified molybdenum sulfide complexes; and Syntheses and reactions of pyrrole complexes]. Final report. Office of Scientific and Technical Information (OSTI), January 1998. http://dx.doi.org/10.2172/650154.

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