Improving Complex Coacervate Tissue Adhesive Performance Using Bridging Polymer Chains

Complex coacervates have emerged as promising tissue adhesives due to their excellent wet adhesion and tunable properties. However, maintaining stable adhesion on soft, dynamic tissues remains challenging. In this study, the use of a bridging polymer was investigated to enhance the adhesive properties of a complex coacervate adhesive (CCA) composed of poly­(allylamine hydrochloride) (pAH) and polysulfopropyl methacrylate (pSPMA). The CCA undergoes solidification as a result of a change in salt concentration, forming a robust adhesive under physiological conditions. Pretreatment with pAH, but not pSPMA, significantly improved adhesion energy on both model hydrogels and biological tissues by forming a polymer-rich bridging layer at the interface. The beneficial effect was driven by accumulation of pAH in superficial layers of both the CCA and the substrates. This enabled the CCA to withstand higher deformation before adhesive failure. These findings underscore the potential of bridging polymers to improve CCAs and other tissue adhesives for biomedical applications.