Smart Biointerface with Photoswitched Functions between Bactericidal Activity and Bacteria-Releasing Ability

Smart biointerfaces with capability to regulate cell–surface interactions in response to external stimuli are of great interest for both fundamental research and practical applications. Smart surfaces with "ON/OFF" switchability for a single function such as cell attachment/detachment are well-known and useful, but the ability to switch between two different functions may be seen as the next level of "smart". In this work reported, a smart supramolecular surface capable of switching functions reversibly between bactericidal activity and bacteria-releasing ability in response to UV–visible light is developed. This platform is composed of surface-containing azobenzene (Azo) groups and a biocidal β-cyclodextrin derivative conjugated with seven quaternary ammonium salt groups (CD-QAS). The surface-immobilized Azo groups in trans form can specially incorporate CD-QAS to achieve a strongly bactericidal surface that kill more than 90% attached bacteria. On irradiation with UV light, the Azo groups switch to cis form, resulting in the dissociation of the Azo/CD-QAS inclusion complex and release of dead bacteria from the surface. After the kill-and-release cycle, the surface can be easily regenerated for reuse by irradiation with visible light and reincorporation of fresh CD-QAS. The use of supramolecular chemistry represents a promising approach to the realization of smart, multifunctional surfaces, and has the potential to be applied to diverse materials and devices in the biomedical field.