Photo-Cross-Linkable, Injectable, and Highly Adhesive GelMA-Glycol Chitosan Hydrogels for Cartilage Repair.

Hydrogels provide a promising platform for cartilage repair and regeneration. Although hydrogels have shown some efficacy, they still have shortcomings including poor mechanical properties and suboptimal integration with surrounding cartilage. Herein, we develop hydrogels that are injectable, cytocompatible, mechanically robust, and highly adhesive to cartilage. Our approach uses GelMA-glycol chitosan (GelMA-GC) that is crosslinkable with visible light and photo-initiators (lithium acylphosphinate (LAP) and tris (2,2'-bipyridyl) dichlororuthenium (II) hexahydrate ([RuII(bpy) ] and sodium persulfate (Ru/SPS)). Ru/SPS-cross-linked hydrogels have higher compressive and tensile modulus, and most prominently higher adhesive strength with cartilage, which also depends on inclusion of GC. Tensile and push-out tests of the Ru/SPS-cross-linked GelMA-GC hydrogels demonstrate adhesive strength of approximately 100 kPa and 46 kPa, respectively. Hydrogel precursor solutions behave in a Newtonian manner and are injectable. After injection in focal bovine cartilage defects and in situ cross-linking, this hydrogel system remains intact and integrated with cartilage following joint manipulation ex vivo. Cells remain viable (> 85%) in the hydrogel system, and further show tissue regeneration potential after three weeks of in vitro culture. These preliminary results provide further motivation for future research on bioadhesive hydrogels for cartilage repair and regeneration. This article is protected by copyright. All rights reserved.