Synthesis and characterization of positively charged interpenetrating double-network hydrogel matrices for biomedical applications

In this study, positively charged interpenetrating double-network (DN) hydrogels of polyvinyl alcohol/polyacrylamide (PVA/PAm) were prepared using bifunctional cationic salt as a crosslinker. The cationic salts were synthesized by the Michael-addition of piperazine (PZ) with butanediol diacrylate (BDDA)/hexanediol diacrylate (HDDA) separately followed by the methylation of the products. The chemical characterization of the quaternary salts was performed using ATR-FTIR and NMR (1H, 13C, DEPT) spectroscopy. The zeta potential of the cationic salts was found to be in the range of 17.6 ± 8.03-20.3 ± 10.1 mV for various monomers. Chemical crosslinking (free radical polymerization) and physical crosslinking (freeze-thaw) techniques were employed to crosslink PAm and PVA, respectively. The quaternized salt of BDDA and PZ was used to crosslink the PAm hydrogel network. The thermal stability and the compression modulus of the hydrogel increased, while the displacement value and the water absorption capacity decreased when crosslinker concentration was increased from 1.0 to 4.0 mol%. The excellent cell viability (⩾94%) and gel content (⩾92%) suggest that these matrices can be utilized as future biomaterials for biomedical applications.