Properties of Cell-Compatible Poly(vinyl alcohol) Hydrogels Cross-Linked with Hydrophobic Luteolin

Biological applications of poly(vinyl alcohol) hydrogels (PVA) are limited because the pure polymer has low hardness and poor mechanical properties. The quality of most PVA hydrogels can be enhanced by addition of molecules that form strong covalent or noncovalent cross-links between the PVA chains. Natural materials as cross-linking agents are attracting interest because of their degradability, cell compatibility, and environmental friendliness. Herein, we report the use of hydrophobic luteolin (LUT) in the facile fabrication of a type of hybrid PVA hydrogel. Even at low LUT concentration (0.04 wt %), the strong hydrogen bonding formed between PVA and LUT caused gelation at 25 °C after the reagents were mixed at high temperature. The effects of LUT concentration, freezing and thawing, and pH on hydrogels mechanics were evaluated, and a possible mechanism of hydrogel formation was deduced. Notably, after freezing and thawing, the elongation (600%) and tensile strength (0.812 MPa) of the PVA/LUT hydrogels were superior to those of common PVA hydrogels. Our study reveals a hydrophobic biocrosslinker for PVA hydrogels that has potential applications in medicine. We expect that this contribution will promote screening of other biocrosslinkers for PVA hydrogels.