Swelling properties of semi-IPN type hydrogels containing acrylic acid- acrylamide- poly(vinyl alcohol) and lipase release behaviors

In the presented study, semi-IPN hydrogels containing differentcompositions of acrylamide (AAm), acrylic acid (AA) and poly(vinylalcohol) (PVA) were synthesized by free radical polymerization usingammonium persulphate/sodium methabisulphite [(NH4)2S2O8/Na2S2O5] asa chemical initiator pair and ethylene glycol dimethacrylate (EGDMA) asa crosslinker. The swelling behaviors of the produced hydrogels wereinvestigated as a function of time. The percentage swelling (% S) of allhydrogels were increased with time and after 24 hours constantpercentage swelling was observed. It was found that the swellingvalues of hydrogels that contain AA were higher than the swelling ofother hydrogels. The presence of PVA in gel matrix decreased theswelling percentages. PAA was determined as the most swollenhydrogel at pH=7,4 and 37,0 ºC. The swelling behaviors of hydrogelswere also investigated by changing the temperature. The swellingvalues increased with temperature and maximum swelling percentagewere observed around 40,0 ºC for all the hydrogels. The effect oftemperature on swelling of PAA/PVA hydrogel was found to be higherthan the other hydrogels. % S of PAA/PVA hydrogel had reached about% 1700 at 40,0 ºC. The swelling studying of hydrogels by changing pHwere investigated. It was found that in spite of the swelling values ofPAA/PVA and P(AA-co-AAm) hydrogels were rather affected by pHchange, the PAAm/PVA hydrogel didn?t affected. Lipase immobilizationwas made via adsorbation, covalent binding to point activated by 1-cyclohexyl-3-(2-morpholino-ethyl) carbodiimide (CDI) and entrapmentmethods into P(AA-co-AAm)/PVA hydrogel geting the optimumconditions in semi-IPN type hydrogels. Hydrogels immobilized andentrapped lipase enzyme releasing has been followed by UVspectroscopy. All of the release studies were carried out at pH=7,4 and37,0 ºC. When the release study was investigated, it has been seen thatlipase releasing of adsorbed hydrogel is too more than activated with(CDI) of immobilized hydrogel. When the release values wereinvestigated, it has been seen that releasing of enzyme is around 100%.The release of entrapped lipase kinetic data has found by make usingfrom Fick law than k, n parameter were calculated 6,5x10-4 and 1,1772respectively. Olive oil studies have been made for determination ofactivity of lipase entrapped P(AA-co-AAm)/PVA hydogel.