Investigation of swelling, activity and relese behaviours of lipase immobilized polyacrylamide hydrogels

In the thesis that is presented, acrylamide-based hydrogels were synthesized with free radical polymerization using ammonium persulphate(APS)/sodium methabisulphite(SMBS) as initiators and N, N' methylenebisacrylamide (MBAAm) as crosslinker. In the first stage, polyacrylamide hydrogels, which are synthesized drying with different drying methods, were examined surface morphology, dynamic and kinetic swelling behaviors. The effects of the drying methods on water absorbing capacity of hydrogels, the best drying method was selected for the second stage. In the second stage, in order to increase water absorbing capacity of hydrogels, lipase was immobilized in polyacrylamide hydrogels by the entrapment method. For these hydrogels; thermal, structural and surface morphology, activity and release behavior, dynamic swelling behavior were investigated. TGA, XRD and SEM were used for determination of thermal, structural and surface properties. The result of these examinations, the amount of immobilized lipase was optimized. A variety of hydrogel swelling kinetics modeling techniques were applied on the dynamic swelling rates of non-modified and the optimum amount of lipase immobilized hydrogels. For all the hydrogels; the diffusion coefficient of kinetic parameters such as diffusion mechanism, initial and equilibrium swelling ratio, the penetration rate of the solvent, diffusion coefficient were determined. When analyzing the impact of drying methods on hydrogels, compared to dried PAAm hydrogels by the poor solvent method, it was found that the amount and size of the pores of dried PAAm hydrogels by freeze dryer method were more. Thus, it was identified that dried PAAm hydrogel by freeze dryer method superior to other method with regard to surface properties, the dynamic swelling rate and kinetic swelling parameters. So; in the second stage of the thesis, modified hydrogels were dried by freeze dry method. It was determined that high thermal stability, crystalline and / or three-dimensional complex structure, increase of the amount and size of the pores were at the optimum amount of lipase immobilized PAAm hydrogels by the method of entrapment. At the same time, it was spesified that the equilibrium swelling ratio of the hydrogels increased ≈ 1181% and water adsorption capacity of hydrogels increased. Therefore, it was inferred that all characterized properties of modified hydrogels evolved. This development shows that a good modification process was carried out.