Biocompatible autonomous self-healing PVA-CS/TA hydrogels based on hydrogen bonding and electrostatic interaction.

The biocompatible autonomous self-healing hydrogels have great potential in biomedical applications. However, the fairly weak tensile strength of the hydrogels seriously hinders their application. Here, we introduced chitosan (CS) into the polyvinyl alcohol (PVA)-tannic acid (TA) hydrogel and investigated the effects of the CS content, as CS can not only form reversible H bonds with PVA and TA but also form reversible electrostatic interactions with TA. Since the bond energy of electrostatic interaction is much stronger than that of the H bond, the tensile strength and self-healing properties of PVA-TA hydrogel can potentially be improved by adding the CS. The results suggested that when the PVA content and the total content of CS and TA were fixed (PVA: 30 wt.%; CS + TA: 3 wt.%) and the CS content was increased to 1 wt.%, the tensile strength of the PVA-CS/TA hydrogel could be up to 447 kPa, and the self-healing efficiency remained at 84% in 2 h. Compared with the reported self-healing hydrogels with similar biocompatibility and self-healing properties, whose tensile strength is usually less than 300 kPa, the PVA-CS/TA hydrogel prepared here shows a significant improvement in the tensile strength.