Interpenetrated Chitosan-Poly(Acrylic Acid-Co-Acrylamide) Hydrogels. Synthesis, Characterization and Sustained Protein Release Studies

Abstract

Interpenetrated polymer networks of chitosan (CHI), polyacrylic acid (PAA) and polyacrylamide (PAM) were prepared by free radical polymerization. These hydrogels were either washed with double distilled water (CHI/PAA/PAM) A or hydrolyzed with 1M sodium hydroxide (NaOH), (CHI/PAA/PAM) S. Both types of hydrogels were characterized by infrared spectroscopy, microstructural techniques and compressive mechanical testing. Finally, hydrogels were loaded with bovine serum albumin (BSA) and release followed at different pHs. Infrared spectra analysis showed correspondence between hydrogels and monomer feed compositions. Hydrolyzed hydrogels, had increased water content and pH swelling dependence. Compression modulus of swelled hydrolyzed hydrogels decreased with increasing equilibrium water content. Higher BSA loadings were achieved on hydrolyzed hydrogels due to their high water content and porosity. Protein release from hydrogels was low (≤ 20% after 10 hours) at pH 1.2, but sustained release was observed at pH 6.8 and 7.4. The integrity of the protein released at 6.8 and 7.4 by hydrolyzed hydrogels was unaffected. The hydrogles showed no cytotoxic effects on human skin dermal fibroblasts as determined by MTT assay except for two compositions of (CHI/PAA/PAM) A samples, which after seven days presented a viability lower than 80% respect to the control.