Smart bactericidal surfaces with thermoresponsive switchability and pH controlled regenerability

We developed smart bactericidal surfaces with thermoresponsive switchability and pH-controlled regenerability, which was prepared by the reversible formation of dynamic Schiff base bonds between amino-functionalized surfaces (surfaces modified by polydopamine, Sub-PDA) and aldehyde-terminated polymers consist of thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) and bactericidal quaternized poly(dimethylaminoethylmethacrylate) (QPDMAEMA). At room temperature below the lower critical solution temperature (LCST), the PNIPAM chains were stretchable, leading to the burial of the bactericidal QPDMAEMA chains and the loss of bactericidatity. At physiological temperature above the LCST, the PNIPAM chains collapsed, leading to the exposure of the bactericidal QPDMAEMA chains and facilitating the contact killing of bacteria. The dead bacteria could be detached by the extended PNIPAM chains when the temperature returned to the room temperature below the LCST. Meanwhile, the long-lasting and regenerable bactericidal surfaces could be achieved by the reversible destruction at pH 2 and formation at pH 8.5 of Schiff base bonds between amino-functionalized surfaces and aldehyde-terminated polymers. The study thus presents a promising approach to the realization of smart, multifunctional bactericidal surfaces, and may find applications in diverse biomedical materials and devices.