Double cross-linked poly(vinyl alcohol) microcomposite hydrogels with high strength and cell compatibility

Polyvinyl alcohol (PVA) hydrogels, due to their excellent tissue viscoelasticity and biocompatibility, are widely used in biomedical fields e.g. tissue engineering. However, their poor mechanical properties greatly limit their applications, especially as load-bearing implants in the body. To address this issue, we first synthesize photocrosslinkable PVA-glycidyl methacrylate (PVAGMA) with the extremely low substitution degree (DS = 0.01) of methacryloyl groups, which can undergo chemical crosslinking to form a hydrogel network with good compression performance. Microcrystalline cellulose (MCC)/PVAGMA hydrogels are subsequently fabricated by photopolymerization approach followed by physical crosslinking with tannic acid (TA) as a cross-linking agent. By combing chemical and physical crosslinking, the double crosslinked PVA microcomposite hydrogels exhibit excellent tensile/compression strengths. Specifically, the hydrogels present 23-fold, 20-fold, and 25-fold increase in fracture stress, elastic modulus, and toughness respectively, compared to the pure PVAGMA hydrogels. Notably, a hydrogel with the optimum composition can lift a weight of 3.775 kg, which is about 2220 times of its own weight. Moreover, the hydrogels are cytocompatible at a relatively low extraction concentration, demonstrating their potential in biomaterials.