Tough Bioactive Composite Hydrogel of Gelatin Methacrylate and Bacterial Cellulose Prepared by Combined Freeze-Thaw and Photocrosslinking Processes

Despite the excellent structural stability and mechanical properties of bacterial cellulose (BC) hydrogels, BC hydrogels do not have sufficient bioactivity to support the growth and proliferation of tissue cells. Gelatin methacrylate (GelMA) is a good choice to compensate for the bioactivity of BC hydrogel. However, GelMA itself does not provide sufficient mechanical properties for the structure, and it is also difficult to use as an ink for printing at low concentrations. The increase in GelMA concentration can enhance its mechanical properties, but the biocompatibility decreases due to the increased hydrogel density. Here, we prepared a tough and biocompatible composite hydrogel using BC incorporated with GelMA. A freeze-thaw process was introduced in the fabrication of the BC/GelMA composite hydrogel to improve its mechanical properties. The GelMA interpenetrated in the BC structure was freeze-thawed and photo-crosslinked to enhance mechanical properties. Such a process provided double networks within the highly networked structure of BC. Moreover, the order of freeze-thaw and photo-crosslinking created a significantly different reinforcing effect with the BC/GelMA composite hydrogel.