Combating Pseudomonas aeruginosa Biofilms by a Chitosan-PEG-Peptide Conjugate via Changes in Assembled Structure

Pseudomonas aeruginosa (P. aeruginosa) biofilms are associated with a wide range of infections, from chronic tissue diseases to implanted medical devices. In a biofilm, the extracellular polymeric substance (EPS) causes an inhibited penetration of antibacterial agents, leading to a 100-1000 times tolerance of the bacteria. In view of the water-filled channels in biofilms and the highly negative charge of EPS, we design a chitosan-polyethylene glycol-peptide conjugate (CS-PEG-LK₁₃) in this study. The CS-PEG-LK₁₃ prefers a neutrally charged assembly at a size of ∼100 nm in aqueous environment, while undergoes disassembly to expose the α-helical peptide at the bacterial cell membrane. This behavior provides CS-PEG-LK₁₃ superiorities in both penetrating the biofilms and inactivating the bacteria. At a concentration of 8 times the minimum inhibitory concentration, CS-PEG-LK₁₃ has a much higher antibacterial efficiency (72.70%) than LK₁₃ peptide (15.24%) and tobramycin (33.57%) in an in vitro P. aeruginosa biofilm. Moreover, CS-PEG-LK₁₃ behaves comparable capability of combating an implanted P. aeruginosa biofilm to highly excess tobramycin. This work has implications for the design of new antibacterial agents in biofilm combating.