pH responsive antifouling and antibacterial multilayer films with Self-healing performance

The settlement and growth of marine organism increased sharply with the ships in a static environment, although the release rate of antibacterial agent decreased smoothly. Besides of a rapid release rate of the antibacterial agents, a destruction of films by sand and rocks restricted the long-term antibacterial efficiency of antifouling films on voyage. In this work, intelligent bacterial-triggered multilayer films are prepared via adding pH responsive nanocapsules to control releasing of antifouling agents during bacterial growth. Chitosan (CS) has a capability to change the swelling of capsules by amino protonation and deprotonation upon the change of the environmental pH. It is combined with capsaicin (CAP) to form nanocapsules for accomplishing a pH responsive behavior. The intelligent CAP@CS nanocapsules are added in polydopamine/sodium alginate (PDA/Alg)m PEM multilayer films to enable the (PDA/Alg-CAP@CS-n)m films with a pH-triggered antifouling agents (CAP) releasing performance. The results demonstrate that there are outstanding pH-triggered activities for the (PDA/Alg-CAP@CS-8)20 multilayer films. The released CAP concentration decreased by nearly 42% from pH 4 to pH 8.5. The bacteriostatic percentages of (PDA/Alg-CAP@CS-n)m against S. aureus and P. aeruginosa are 79% and 74%, respectively, after 60 days of immersion in pH 8.5 PBS buffer solutions. The amino deprotonation of CS in alkaline condition prevents the CAP release, resulting in an extended antibacterial performance. The electrostatic interaction between Alg and PDA in solutions leads to (PDA/Alg-CAP@CS-n)m films to exhibit the self-healing behaviors since the ions penetrate and free chins transfer in artificial seawater solutions after mechanical scratching.