Autoclaving pHEMA-Based Hydrogels Immersed in Deionized Water has No Effect on Physicochemical Properties and Cell Behaviors

Abstract

Hydrogels based on poly-(2-hydroxyethyl methacrylate) (pHEMA) have been widely used as biomaterials in tissue engineering due to their biocompatibility, hydrophilicity, and low friction coefficient. The terminal sterilization of hydrogels is a critical step in clinical applications. However, regulations and standardization for the sterilization of hydrogels based on pHEMA are still lacking. In this study, we explored six sterilization methods on pHEMA-based materials (A1: pHEMA, A2: pHEMA copolymerizes with acrylic acid, and A3: pHEMA copolymerizes with acrylic acid and further coordinated with iron ions), such as gamma irradiation, 75% ethanol, ultraviolet (UV), ethylene oxide (EtO), and autoclaving with or without deionized water (autoclaving-H2O or autoclaving-dry). Combining results from the multifaceted approaches with assessment, pHEMA-based hydrogels can be completely sterilized via the autoclaving-H2O method analyzed by sterilized testing. The physicochemical properties and cell behavior of sterilized hydrogels were not influenced by this sterilization approach, validated by Fourier transform infrared (FT-IR) spectroscopy and tensile tests. The pHEMA-based hydrogel sterilized by the autoclaving-H2O method also had no effect on the cell behavior evaluated by in vitro cytotoxicity experiments and caused no evident inflammatory reaction in tissue in vivo implantation experiments. However, it was also found that there were still some defects in the A2 and A3 groups as biomaterials possibly because of an inappropriate proportion of formulations or raw material used in exploring sterilization methods. These findings have implications for the improvement and clinical application of pHEMA-based hydrogels.