Evaluations of poly(vinyl alcohol) hydrogels cross-linked under γ-ray irradiation

Cross-linked poly(vinyl alcohol) (PVA) hydrogels were prepared under Cobalt gamma ray (Co gamma-ray) irradiation. The physical properties of these hydrogels, including their gelation, water absorptivity, and gel strength, were examined to evaluate the applicability of these hydrogels for use as a synthetic extracellular matrix (ECM). The gamma-ray-irradiated hydrogels showed improved mechanical properties when compared to glutaraldehyde (GA)-treated hydrogels. The swelling degree was inversely proportional to the gel content and gel strength. The biocompatibility profiles of these hydrogels, for use as tissue engineering scaffolds, have been evaluated (i) in vitro in cultures of mouse fibroblasts and (ii) in vivo by subcutaneous implantation studies in rats. A cytotoxicity assay revealed that the gamma-ray-treated hydrogel was approximately half as toxic as the GA-treated PVA hydrogel. Subcutaneous implantation studies in rats showed that GA-treated PVA hydrogels created harsh environments to their surrounding tissue components. However, no severe acute foreign body reactions were found around the gamma-ray-treated implants, and these reactions decreased upon increasing the implantation time. These results suggest that Co gamma-ray-treated PVA hydrogels are promising materials for the design of matrices for cell growth and proliferation.