Enzyme and pH dual-responsive CAP@CS@PLGA microcapsules for controlled release antibacterial application

In order to overcome the problem of fast release of antifouling agent capsaicin, enzymatic and pH double response poly(lactic-co-glycolic acid) @ chitosan @ capsaicin (CAP@CS@PLGA) dual-core shell microcapsules were prepared by composite emulsion method to achieve controlled release and the long-lasting antibacterial. In the first stage, due to the excellent biodegradability PLGA shell quickly decomposes and ruptures, releasing the internal CAP and CAP@CS to achieve the intelligent controlled release of enzymatic response. Rapid response within 12 h and achieves over 90% bacterial inhibition. The antibacterial rate at pH 4 is about five times more than that at pH 8. With the decrease of pH value caused by bacterial reproduction, the protonation effect of CS is triggered to release internal CAP, realizing controlled release sterilization of pH response in the second stage, the bacterial inhibition rate remains stable at over 90%. On the 7th day of the long-lasting inhibition experiment, a small increase in the number of colonies could be observed, but it was soon inhibited again to low-level state. This is the feature of the dual enzymatic and pH response. The bacterial inhibition rate was stable at about 90% for 24 days, which proves that compared with the single response nanocapsules, the prepared microcapsules have more stable and durable phased release antibacterial property.