pH-responsive Capsaicin@chitosan nanocapsules for antibiofouling in marine applications

Capsaicin@chitosan nanocapsules (CAP@CS) were prepared by micro-emulsion method in this work. Through transition between protonation and deprotonation of pH sensitive amino groups in chitosan, capsaicin can be triggered for self-releasing by pH changes resulted from bacterial reproduction. The total amount of released CAP@CS at pH 4 is five times more than that at pH 8.5. The CAP@CS is able to maintain the pH responsive property after 15 cycles of dialysis at pH ranging from 4 to 8.5, indicating a good cycling stability of CAP@CS nanocapsules. The bacteriostasis efficiency of CAP@CS is still up to 82.23%, 81.13% and 80.43% against adhesion of Escherichia coli (E.coli), Staphylococcus aureus (S.aureus) and Pseudomons aeruginosa (P. aeruginosa), respectively, which is caused by the repeated protonation and deprotonation of amino groups in chitosan. The prepared CAP@CS nanocapsules enable a bio-driven, intelligent and pH responsive performance for antifouling in marine applications.