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

Abstract

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.

Porous Microstructured Surfaces with pH‐Triggered Antibacterial Properties

“…The block copolymer polystyrene-b-poly(4-(1-(2-(4-methylthiazol-5-yl)ethyl)-1H-1,2,3-triazol-4-yl)butyl methacrylate) (PS 54 -b-PTTBM 23 , M n = 13 600 g mol −1 , M w /M n = 1.74) was synthesized via atom transfer radical copolymerization (ATRP) as previously described. [10,38] The 1 H NMR spectrum and gel permeation chromatography (GPC) curve are displayed in Figures S1 and S2, Supporting Information.…”

“…Porous films functionalized with the antimicrobial copoly mer PS 54 -b-PTTBM 23 were prepared by the breath figures approach using chloroform as the solvent. In previous works, cationic copolymers with permanent positive charges, such as polymers with quaternary ammonium groups, have been employed to incorporate antimicrobial properties into breath figure films.…”

“…[39,40] However, polar solvents such as THF, which produce poorly ordered structures, and/or polymers with low charge density are required in most cases in order to solubilize the cationic polymers. In the current work, we prepared films from a neutrally charged polymer, PS 54 -b-PTTBM 23 ; thus, typical organic solvents used in the breath figures approach can be employed. This block copolymer is composed of a PTTBM block with two groups per monomeric unit (thiazole and triazole groups) susceptible of quaternization or protonation at acidic pH values (see Scheme 1), which would lead to the breath figures films having highly charged surfaces.…”

“…Accordingly, an ideal antimicrobial surface should prevent bacterial adhesion, kill adhered bacteria in case of contamination and, afterward, clean the surface of dead bacteria (i.e., demonstrate a self‐cleaning capacity). Such smart surfaces should be capable of reversibly varying their surface properties in response to changes in the environment, such as local acidity, the presence of enzymes, temperature, light, or the presence of counterions, among others. Thus, by simple changes in the external conditions, the surfaces can kill adhered bacteria and, subsequently, shed dead bacteria from the surface, cleaning the surface and maintaining long‐term antimicrobial activity.…”

Dynamic substrates for cell biology

“…[35•] With the azobenzenes, the group can either be used as a linker terminated in RGD[36] or as a terminal group itself for host-guest interactions with functionalized cyclodextrins. [37–40] In the former case, Selhuber-Unkel and co-workers altered the photophysical properties of the azobenzene via “push-pull” substitution with an electron-withdrawing and electron-donating group. [41•] The generated species displayed a rapid cis - trans back-reaction (10 2 –10 5 Hz) that enabled studies of integrin-mediated cellular responses to oscillatory “tickling” forces at previously inaccessible time scales, though the incomplete photoisomerization of the azobenzene chromophore is a limitation.…”