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.