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    Immobilization of Saccharomyces cerevisiae on to acrylamide-sodium acrylate hydrogels for production of ethyl alcohol
    (Elsevier Science Inc, 2003) Öztop, HN; Öztop, AY; Karadag, E; Isikver, Y; Saraydin, D
    Acrylamide/sodium acrylate (AAm/SA) copolymers, prepared by using various crosslinkers, were used in experiments on swelling, diffusion, immobilization of yeast cells (Saccharomyces cerevisiae) and production of ethyl alcohol. AAm/SA hydrogels were used for swelling and diffusion studies in the nutrient medium of the cells. The parameters of equilibrium swelling, maximum swelling, initial swelling rate, diffusional exponent, network constant and diffusion coefficient of the hydrogel/penetrant systems were calculated and evaluated. Yeast cells were immobilized onto the hydrogels by adsorption method during multiplication and ethyl alcohol production of the hydrogels was investigated. Swelling of AAm increased with the addition of SA and ethyl alcohol production increased with increasing SA in the hydrogels. The best system for immobilization is found to be AAm/SA hydrogels containing N,N'-methylenebisacrylamide as crosslinker. (C) 2002 Elsevier Science Inc. All rights reserved.
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    In vivo biocompatibility of radiation crosslinked acrylamide copolymers
    (Elsevier Science Bv, 2004) Saraydin, D; Ünver-Saraydin, S; Karadag, E; Koptagel, E; Güven, O
    In vitro swelling and in vivo biocompatibility of radiation crosslinked acrylamide copolymers such as acrylamide/crotonic acid (AAm/CA) and acrylamide/itaconic acid (AAm/IA) were studied. The swelling kinetics of acrylamide copolymers were performed in distilled water, human serum and some simulated physiological fluids such as phosphate buffer, pH 7.4, glycine-HCl buffer, pH 1.1, physiological saline solution, and some swelling and diffusion parameters have been calculated. AAm/CA and AAm/IA hydrogels were subcutaneously implanted in rats for up to 10 weeks and the immediate short- and long-term tissue response to these implants were investigated. Histological analysis indicated that tissue reaction at the implant site progressed from an initial acute inflammatory response. No necrosis, tumorigenesis or infection was observed at the implant site up to 10 weeks. The radiation crosslinked AAm/CA and AAm/IA copolymers were found well tolerated, non-toxic and highly biocompatible. However, AAm/IA copolymer was not found to be compatible biomaterials, because one of the AAm/IA samples was disintegrated into small pieces in the rat. (C) 2003 Elsevier B.V. All rights reserved.
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    Water uptake in chemically crosslinked poly(acrylamide-co-crotonic acid) hydrogels
    (Elsevier Sci Ltd, 2005) Karadag, E; Üzüm, ÖB; Saraydin, D
    The aim of this study was to investigate that swelling capability of acrylamide (AAm) hydrogels by adding hydrophilic co-monomer such as crotonic acid (CA). Superswelling poly(acrylamide/crotonic) acid, poly(AAm-co-CA) hydrogels were prepared by free radical polymerization in aqueous solution of AAm with CA. For each copolymerization, four different composition of CA and a concentration of multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA) and N,N ''-methylenebisacrylamide (NMBA) were used. Equilibrium swelling, some swelling kinetics parameters such as the initial swelling rate, swelling rate constant, theoretical equilibrium swelling and diffusional parameters such as swelling exponent, swelling constant and diffusion coefficients of hydrogels have been determined by swelling studies. At the end of dynamic swelling tests, relative content of CA on the swelling properties were examined. It has seen that, if CA contents were increased, equilibrium swelling of the hydrogels were higher than. Poly (AAm-co-CA) hydrogels were swollen in the range 1843-2577% in water, while poly(AAm) hydrogels swelled as 1729-1798%. Equilibrium water content of poly(AAm-co-CA) hydrogels were calculated in the range 0.9473-0.9626. Swelling exponents of poly (AAm-co-CA) hydrogels has calculated as 0.58-0.69. Water intake of hydrogels followed a non-Fickian type diffusion. (c) 2004 Elsevier Ltd. All rights reserved.