pH-responsive linkages-enabled layer-by-layer assembled antibacterial and antiadhesive multilayer films with polyelectrolyte nanocapsules as biocide delivery vehicles

Application of the polymer capsules as vehicles for antibacterial surface against bacterial infections is restricted by spontaneous leakage and specifically responsive release of antibacterial agents. Herein, we present the integration of pH-responsive nanocapsules as delivery tools for hydrophobic biocide within layer-by-layer (LbL) films utilizing alternating imine linkages as the driving force for assembly, thus enabling the introduction of drug and controlled release. The novel capsules are fabricated by means of electrostatic LbL assembly, namely, tannin acid/chitosan nanocapsules embedded with triclosan@cetyltrimethylammonium bromide micelles (TCS@CTAB/TA/CH). The nanocapsules achieve an excellent pH-responsive activity that the release efficiency of antibacterial agent triclosan (TCS) increases by nearly 61.8% from pH 8 to 4. Subsequently, the smart nanocapsules are alternatively incorporated via imine linkage into the dextran aldehyde (DA) polyelectrolyte multilayers in LbL deposition (denoted as (DA-TCS@CTAB/TA/CH)(n) films). The as-prepared samples are characterized by FTIR, FESEM, TEM, DLS and AFM. Noticeably, the (DA-TCS @CTAB/TA/CH)(20.5) film exhibites optimal pH-responsive activity with release concentration of TCS up to 4.01 mg/L at pH 6. The bacteriostatic percentages of (DA-TCS@CTAB/TA/CH)(20.5) against E. coll. and P. aeruginosa are respectively 99.62% and 97.35% after 24-h incubation at pH 6. Besides, the multilayers are capable of supplying a long-term (30 days) antibacterial property. The self-polishing mechanism of (DA-TCS@CTAB/TA/CH)(n) films is proposed to illuminate the enhanced antibacterial and antiadhesive performances. It seems that the films present a promising way to incorporate biocide to resist bacterial infections and prolong the antimicrobial activity of antibacterial surface.