The preparation and characterization of biomimetic hydrogel tissue adhesives for articular cartilage injuries

Articular cartilage is a specialized tissue with limited regenerative capacity due to its reliance on synovial fluid for nutrition. Consequently, blood-derived growth factors cannot reach this tissue, and healing occurs only within the cartilage itself. Clinical research on cartilage repair typically focuses on using (i) cells, (ii) scaffolds, or (iii) signaling molecules individually or in combination—a strategy defined as tissue engineering. Articular cartilage injuries pose a significant challenge in musculoskeletal medicine because of the tissue's restricted regeneration capability. The aim of this study is to develop bioadhesive hydrogels that enhance both adhesive and cohesive forces for cartilage injury repair, and to evaluate their adhesive properties in vitro and ex vivo. In this context, injectable and in situ dual-crosslinkable bioadhesive hydrogels based on polyethylene glycol diacrylate (PEGDA) were prepared, and their adhesive strengths were assessed. PEGDA was synthesized by the diacrylation of polyethylene glycol (PEG), while methacrylated alginate (AlgMA) was formed through methacrylation of alginate. PEG was modified to improve mechanical strength and adhesive properties, and PEGDA was combined with AlgMA to enhance cohesive strength. Chemical bonds (such as amide bonds and thioesters) formed between the cartilage tissue and the PEGDA/AlgMA structure via amine-thiol groups, thus increasing adhesive strength. This bioadhesive system, which can be applied by injection and crosslinked in situ with visible light and Ca²⁺ ions, demonstrated strong adhesion properties (Shear Strength 384 kPa). In burst pressure tests, ex vivo results were approximately 4–5 times higher than in vitro results, reaching up to 200 kPa; similarly, in shear strength tests, ex vivo values reached up to 400 kPa. Findings indicate that the developed hydrogels have promising potential to mimic the mechanical and biological properties of native cartilage tissue.