Synthesis of stimuli sensitive hydrojels and investigation of drug release behaviors

In this study, temperature and pH sensitive poly(NIPA-co-VSA)-Alj IPN hydrogels were synthesized by free radical polymerization method in aqueous solution. In order to increase the sensitivity of macrostructured poly(NIPA-co-VSA)-Alj IPN hydrogels to temperature and pH, poly(NIPA-co-VSA) nanogels obtained by emulsion polymerization method were used as IPN agent in their structure. Na-Alginate natural polymer was used as a semi-IPN agent in the structure for the hydrogels to physically crosslink with multivalent cations. Poly(NIPA-co-VSA)-Alj IPN hydrogels were kept in CaCl2 solutions of different concentrations (0.010, 0.025, 0.050, 0.075 M) for 30 minutes to obtain their physically cross-linked series at different rates. The morphological, mechanical and drug release behaviors of these hydrogels were investigated. Structural and morphological characterizations of the synthesized hydrogels were performed by FT-IR and SEM analysis, respectively. As a result of the mechanical tests, it was determined that hydrogels without physical crosslinks were quite soft and ductile, but exhibited more brittle and rigid behavior with the increase of the physical crosslink concentration in the structure. As a result of the swelling tests of poly(NIPA-co-VSA)-Alj IPN hydrogels, it was found that the swelling capacity decreased with the increase of the physical crosslink concentration in the structure. In order to examine the potential of poly(NIPA-co-VSA)-Alj IPN hydrogel series as a stimulu-responsive drug delivery system in medicine, their DOX drug release behavior in solution at different temperatures and pHs were investigated. For this purpose, DOX drug was loaded in solution to hydrogels that did not contain physical crosslinks and were crosslinked at different concentrations by keeping them in 0,010, 0,025, 0,050, 0,075 M CaCl2 solutions for 30 minutes and their drug loading capacities were calculated as 161, 148, 139, 102 and 86 mg DOX/g polymer, respectively. As a result of the drug release studies, it was determined that each hydrogel type has different drug release behavior. These drug release behaviors, which are sensitive to physical crosslinking degree, temperature and pH, are modeled in MATLAB with high compatibility by using artificial neural networks (ANN) modelling technique. Keywords: N-isopropylacrylamide, Vinylsulfonic acid, IPN hydrogels, Drug release, Modelling, AN