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Öğe Acrylamide-Sepiolite Based Composite Hydrogels for Immobilization of Invertase(Wiley, 2009) Oztop, H. Nursevin; Hepokur, Ceylan; Saraydin, DursunNovel composite hydrogels, poly(acrylamide)-sepiolite (PAS), poly(acrylamide/acrylic acid)-sepiolite (PAAS), and poly(acrylamide/itaconic acid)-sepiolite (PAIS) were prepared and used for the immobilization of invertase. The parameters of equilibrium swelling, diffusional exponent, and diffusion coefficient of these hydrogels were calculated from swelling experiments. Invertase was immobilized onto PAS, PAAS, and PAIS and immobilized invertases (PASI, PAASI, and PAISI) were prepared. Optimum pH values for free invertase, PASI, PAASI, and PAISI are found to be 5, 5.5, 4.5, and 6, respectively, and the optimum temperatures were 30, 50, 50, and 35 degrees C for free invertase PASI, PAASI, and PAISI. It was found that K-m values of free invertase, PASI, PAASI, and PAISI were 11.3, 41.0, 94.5, and 56.0 mM, respectively. V-max values were 2 mu mol/min for free invertase, 8.10 mu mol/min for PASI, 1.30 mu mol/min for PAASI, and 0.42 mu mol/min for PAISI, respectively. The invertase immobilized hydrogels showed excellent, temperature, storage, and operational stability.Öğe Environmentally Sensitive Hydrogels: N-isopropyl acrylamide/Acrylamide/Mono-, Di-, Tricarboxylic Acid Crosslinked Polymers(Wiley, 2015) Isikver, Yasemin; Saraydin, DursunEnvironmentally sensitive hydrogels responsive to various stimuli such as temperature, pH, ionic strength of the medium and the solvent were prepared by using N-isopropyl acrylamide (NIPAM), acrylamide (AAm) and monomers that have various number of carboxylic acid (XA) functionality using N,N-methylene bisacrylamide (Bis) as crosslinker. Hydrogels were prepared via free radical polymerization reaction in aqueous solution. P(NIPAAm-co-AAm) and p(NIPAAm-co-AAm)/XA hydrogels that contain monoprotic crotonic acid (CA) exhibit a lover critical solution temperature (LCST) at 28 degrees C, whereas p(NIPAAm-co-AAm)/IA (IA:itaconic acid), and P(NIPAAm-co-AAm)/ACA (ACA:acotonic acid) hydrogels exhibit a lover critical solution temperature at 30.7 degrees C and 34.4 degrees C, respectively. Spectroscopic and thermal analyses were performed for the structural and thermal characterizations of the prepared hydrogel. The swelling experiments as equilibrium swelling percentages by gravimetrically were carried out in different solvents, at different solutions temperature, pH, and ionic strengths to determine their effects on swelling characteristic of hydrogels. POLYM. ENG. SCI., 55:843-851, 2015. (c) 2014 Society of Plastics EngineersÖğe Interpenetrating polymeric network hydrogels for potential gastrointestinal drug release(John Wiley & Sons Ltd, 2007) Ekici, Sema; Saraydin, DursunNew interpenetrating polymeric network (IPN) hydrogels based on chitosan (C), poly(N-vinyl pyrrolidone) (PVP) and poly(acrylic acid) (PAAc), crosslinked with glutaraldchyde (G) and N,N'-methylenebisacrylamide (MBA), were prepared and investigated for potential gastrointestinal drug delivery vehicles utilizing a model drug, amoxicillin. IPN hydrogels were synthesized by simultaneous polymerization/crosslinking of acrylic acid monomer in the presence of another polymer (C) and crosslinker (G, MBA). Three different concentrations of glutaraldehyde were used (0.5, 1.0 and 2.0 w/w) to control the overall porosity of the hydrogels, named C-P-AAc/0.5, C-P-AAc/1.0 and C-P-AAc/2.0, respectively. Spectroscopic and thermal analyses such as Fourier transform infrared spectroscopy, thermogravimetric analysis and thermornechanical analysis were performed for IPN characterization. Equilibrium swelling studies were conducted for pH and temperature response behavior. Swelling studies were also carried out in simulated gastric fluid of pH = 1.1 and simulated intestinal fluid of pH = 7.4 to investigate possible site-specific drug delivery. It was found that the release behavior of the drug from these IPN hydrogels was dependent on the pH of the medium and the proportion of crosslinker in the IPN. It was observed that amoxicillin release at pH = 7.4 was higher than at pH = 1.1. The analysis of the drug release showed that amoxicillin was released from these hydrogels through a non-Fickian diffusion mechanism. (c) 2007 Society of Chemical Industry.Öğe Moxifloxacin-Impregnated Contact Lenses for Treatment of Keratitis in Rabbit Eyes(Wiley, 2025) Erdogan, Hakika; Gungor, Buket; Suner, Selin S.; Silan, Coskun; Saraydin, Serpil U.; Saraydin, Dursun; Ayyala, Ramesh S.Moxifloxacin (MOX) was loaded into commercial contact lenses (CLs) via supercritical carbon dioxide (ScCO2) to attain MOX-impregnated CL for keratitis treatment. This study aimed to investigate Pseudomonas keratitis treatment with MOX-impregnated CL compared to the traditional eyedrop administration. MOX impregnation was accomplished employing optimum parameters of 2.5 h drug exposure time, 25 MPa pressure, and 313 K for ScCO2 conditions using ethanol co-solvent rendering sustainable delivery, up to 7 days at effective dosage formulation. The MOX-impregnated CL was found to be safe with no significant toxicity on fibroblast cells after 5 days of contact time. Bacterial viability in vivo keratitis treatment in rabbit eyes was significantly decreased to 10(2) from 10(9) CFU/cornea for MOX-impregnated CL treatment, almost similar to exhaustive conventional 0.5% MOX eye drop treatments. The MOX-impregnated CL treatment revealed no conjunctival hyperemia, edema, or secretion for all eyes in the relevant group, and transparent cornea with no keratitis focus was obtained for two of the eyes (n = 6). The normal histological structure was seen with MOX-impregnated CL treatment on healthy eyes. Moreover, polymorphonuclear cell infiltration observed in keratitis eyes without any treatment was significantly decreased to a few polymorphonuclear cells in the groups treated with MOX eyedrops and MOX-impregnated CL.Öğe Poly(acrylamide-sepiolite) composite hydrogels: Preparation, swelling and dye adsorption properties(Springer, 2006) Ekici, Sema; Isikver, Yasemin; Saraydin, DursunPolymer-clay hydrogel composite was prepared on the basis of polyacrylamide (PAAm) gel containing the clay mineral sepiolite. The properties of swelling and dye adsorption of poly(acrylamide-sepiolite) (AAm/Sep) composite hydrogel were investigated. The parameters of swelling and diffusion in water and dye solutions were calculated for the AAm and AAm/Sep hydrogels. It was found that the equilibrium swelling degree of obtained composite higher than that of AAm gel. Spectroscopic analysis of composite and composite-dye systems was done with FT-IR method. Adsorption of monovalent cationic dyes such as Basic Blue 12 (BB-12) Basic Blue 9 (BB-9), and Basic Violet 1 (BV-1), was studied on the composite. In the adsorption experiments, S (Sigmoidal) type for composite gel adsorption isotherms in the Giles classification system was found. Adsorption studies indicated that the amounts of adsorbed dyes on the AAm/Sep composite hydrogel were increased with following order; BB-12 > BB-9 > BV-1. The composite hydrogel may be considered as good candidate for environmental application to retain more water and dyes.Öğe Poly(acrylamide/maleic acid)-sepiolite composite hydrogels for immobilization of invertase(Springer, 2010) Oztop, H. Nursevin; Hepokur, Ceylan; Saraydin, DursunPoly(acrylamide/maleic acid) and sepiolite (PAMS) composite hydrogel was prepared and used for the immobilization of invertase. In FTIR analysis, the characteristic bands of composite such as -OH, -COOH, Si-OH show the evidence of sepiolite and maleic acid. In TGA analysis, water loss, decomposition of amide side groups and breakdown of main chain regions of the composite were found. The parameters of equilibrium swelling, initial swelling rate, diffusional exponent, and diffusion coefficient were calculated and evaluated from swelling experiments in distilled water. Invertase was immobilized onto PAMS by adsorption and poly(acrylamide/maleic acid)-sepiolite-invertase (PAMSI) was prepared. Optimum pH, optimum temperature values for free invertase and PAMSI were found. It was found that K (m) values of free invertase and PAMSI were 11.3 and 34.1 mM, respectively. V (max) value was found that 2.0 mu mol min(-1) for free invertase and 13.9 mu mol min(-1) for PAMSI, respectively. PAMSI showed excellent temperature, operational and storage stability.Öğe The Removal of Textile Dyes with Cross-Linked Chitosan-Poly(acrylamide) Adsorbent Hydrogels(Taylor & Francis Inc, 2011) Ekici, Sema; Guntekin, Gamze; Saraydin, DursunThis study examined the behaviors and mechanisms of chitosan (CS)-poly(acrylamide) (PAAM) full interpenetrating polymeric network (IPN) hydrogels as an adsorbent to remove EY-4GL and S-Blue textile dyes from an aqueous solution. CS-PAAM IPN hydrogels were prepared by acrylamide monomer polymerization in the presence of a natural polymer, e. g., chitosan. N,N'-methylenebisacrylamide (MBAM) and glutaraldehyde (GLA) were selected to cross-link PAAM and CS chains and a full-IPN structure formed simultaneously. Kinetic swelling studies of CS-PAAM IPNs were carried out with deionized water and aqueous dye solutions. The experimental data clearly suggested that the swelling process obeys second-order kinetics. Network and diffusion parameters for CS-PAAM and PAAM hydrogels were calculated and it was observed that these IPN hydrogels have high cross-linking efficiencies in comparison to PAAM hydrogels. Adsorption of textile dyes onto hydrogels was studied by a batch adsorption technique at 23 degrees C and 40 degrees C, and it was seen that the higher temperature increased the dye adsorption onto the hydrogels. L type (Lan gmuir) adsorption isotherms, according to Giles classification system, were established at the end of adsorption experiments. The prepared IPN hydrogels show good ability to uptake textile dyes from wastewater.
