Fabrication of Tough Composite Hydrogel Bioadhesives Using Poly(methoxyethyl Acrylate- <i>co</i> -acrylamidopropyl-trimethylammonium Chloride) Incorporating Core–Shell Structured Polydopamine-Doped Polypyrrole Nanoparticles

Tough hydrogel bioadhesives have attracted increasing attention in tissue engineering and biomedicine. Especially, the bioadhesives with conductivity, strong adhesive, antioxidant activity, and antibacterial abilities have exhibited great potential in biological medicine. In this work, the poly(EA-co-APTAC) copolymer hydrogels were fabricated via copolymerizing (3-acrylamidopropyl) trimethylammonium chloride (APTAC) and 2-methoxyethyl acrylate using N,N′-methylenebis(acrylamide) (MBA) as a cross-linker. The core–shell structured nanoparticles (PDA@PPy), with polydopamine as the core and polypyrrole as the shell, were incorporated, thereby imparting conductivity to the hydrogels and enhancing their thermal stability and interfacial adhesion. The formation and chemical structure of PDA@PPy nanoparticles were characterized using Fourier transform infrared analysis, scanning electron microscopy, and X-ray photoelectron spectrometer analysis. The fabricated poly(EA-co-APTAC) copolymer hydrogels demonstrated strong adhesion to surfaces of various materials, including rubber, metal, plastic, glass, wood, and polypropylene, and exhibited excellent adhesion to tissues such as heart, liver, spleen, kidney, and lung. In addition, after incorporating PDA@PPy nanoparticles, the composite hydrogels displayed improved adhesion strength to the surface of stainless steel and polytetrafluoroethylene compared to the hydrogels without nanoparticles. The poly(EA-co-APTAC) copolymer hydrogels with and without PDA@PPy nanoparticles performed with excellent tensile and compressive strengths. The increase of PDA@PPy nanoparticles could improve the conductivity and antioxidant ability of the composite hydrogels. The fabricated hydrogels also exhibited effective antibacterial activities against the typical Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus However, the composite hydrogels demonstrated unsatisfactory cytocompatibility and cell pro-migration abilities, and NIH 3T3 cell viability decreased to 50–70% after culturing with the composite hydrogels for 3 days. The obtained data confirmed the potential of composite hydrogels as bioadhesives in biomedical applications.