İNŞaat mühendiSLİĞİ anabiLİm dali

The Synthesis and Characterization of Stimuli Responsive Biopolymer Gels and The Investigation of Their Usages in Drug Release
In this study, CS:AAm, CS:AAm:HMA, and CS:HMA semi-IPN hydrogels have been synthesized from chitosan (CS) natural polymer, acrylamide (AAm) and N-hydroxymethyl acrylamide (HMA) monomers by varying the monomer contents. The polymerization reactions have been performed in the solutions of 1 w/v % or 2 w/v % chitosan in aqueous acetic acid (2 v/v %) by keeping the total initial monomer concentration at 0.5 M and using ammonium persulfate (APS) and N,N,N’,N’-tetramethylethylenediamine (TEMED) as initiator and accelerator, respectively, at 40^oC for 24 hours. While APS was used in the amounts of 1 mol % of monomer content in the feed, TEMED was used in the equal weight of APS. N,N’-methylenebisacrylamide (NMBA) was used in the amount of 1 mol % of monomer content in feed as the crosslinker only in the preparation of the gels which was prepared from AAm monomer. For comparison purpose, AAm and HMA homopolymer and AAm-HMA copolymer gels without CS were also prepared. Another group of polymer synthesized in this work was CS gels (CS:GA) which were prepared by the crosslinking of CS with glutaraldehyde (GA). Drug loaded hydrogels have been obtained by the addition of model drug 5-FU to the feed before the polymerization.
The structural and thermal characterization of drug-loaded or -unloaded hydrogels have been performed by FTIR, XRD and DSC/TGA analysis, and their properties were compared with each other. The swelling kinetics of drug-loaded gels with or without CS in both distilled water and buffer solutions with pH of 2.1 or 7.4 at 37^oC were determined, and the application potential of these gels in the release of 5-FU was investigated. In addition, the compression elastic moduli of these gels were also determined.
The characterization studies indicated that the drug was dispersed homogeneously in the semi-IPN gels. It has been determined that the equilibrium swelling values of CS-containing semi-IPN hydrogels (CS:AAm, CS:AAm:HMA and CS:HMA) in acidic medium (pH=2.1) were higher than those at pH 7.4 due to the protonation of amino groups of CS. In addition, it was also determined that the equilibrium swelling values increased with the increase in AAm content of the gel which has high hydrophilicity. The diffusion of water into the gels was compatible with non-Fickian diffusion behaviors. The amount of drug loading increased with the increase in AAm and CS content of gels. The crosslinking density of gels increased with HMA content of gel due to its methylol groups and it led to decrease in the functional groups which may interact with drug. The release of the drug was quite fast and high amount for CS:AAm gels with low crosslinking density. In addition, the compression elastic moduli of gels increased with their HMA content because of the additional crosslinking. It was also observed that the compression elastic moduli of gels increased with the increase in their CS content.