Self-reinforceable poly(lipoic acid)-based tough underwater tissue bioadhesive

Strong and durable adhesion of bioadhesives on wet/underwater tissues is still challenging because of the hindrance of the hydration layer and swelling of the adhesive. Here a water-induced self-hardening bioadhesive (p(LA-ABO)) composed of poly(lipoic acid) (PolyLA) capped with 4-allyl-1,2-benzenediol (ABO), is prepared through a solvent evaporation-induced self-polymerization method. During underwater curing, the water-induced aggregation of the hydrophobic PolyLA chain of the bioadhesive leads to a soft-to-hard transition, therefore enhancing its cohesion and wet/underwater tissue adhesion. Its tensile strength and adhesion strength on wet porcine skin respectively increased from 57.77 kPa to 93.87 kPa and from 50.48 kPa to 80.59 kPa in 6 h wet adhesion. Moreover, it can still maintain robust adhesion without weakening (∼85.09 kPa) after 6 h of underwater adhesion. Additionally, the adhesive exhibits a very low swelling (∼1.1%) after 12 h of water immersion. It also shows on-demand detachment, good biocompatibility, and biodegradability. By sandwiching a conductive fabric between two bioadhesives, a strain sensor with a high conductivity is created for sensing body motion signals. This integration of water-induced self-hardening wet adhesion with sensing performance may open a new avenue in the design of biosensors for wet/underwater applications. STATEMENT OF SIGNIFICANCE: Bioadhesives have gained growing attention owing to their wide industrial and biomedical applications. However, despite significant efforts, it remains challenging to achieve strong, stable, and durable wet/underwater adhesion in a simple and effective manner due to an interfacial water barrier. To address this issue, we engineer a water-induced self-hardening PolyLA-based bioadhesive with durable and robust wet/underwater adhesion. Furthermore, by integrating this bioadhesive with conductive cotton fabrics, a highly sensitive and rapidly response to body motion signals strain sensor was created, expanding its application range in wet environments. Therefore, this research offers a new methodology for developing wet/underwater biosensors.