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Smart bioactive surfaces that can modulate interactions with biological systems are of great interest. In this work, a surface with switchable bioactivity in response to sugars has been developed. It is based on dynamic covalent bonding between phenylboronic acid (PBA) and secondary hydroxyls on the "wide" rim of β-cyclodextrin (β-CD). The system reported consists of gold surface modified with PBA-containing polymer brushes and a series of functional β-CD derivatives conjugated to diverse bioactive ligands (CD-X). CD-X molecules are attached to the surface to give specified bioactivity such as capture of a specific protein or killing of attached bacteria. Subsequent treatment with cis-diol containing biomolecules having high affinity for PBA (e.g. fructose) leads to the release of CD-X together with the captured proteins, killed bacteria, and so forth from the surface. The surface bioactivity is thereby "turned off". Effectively, this constitutes an on-off bioactivity switch in a mild and noninvasive way, which has the potential in the design of dynamic bioactive surfaces for biomedical applications.

Development of a versatile strategy for antibacterial surfaces is of great scientific interest and practical significance. However, few methods can be used to fabricate antibacterial surfaces on substrates of different chemistries and structures. In addition, traditional antibacterial surfaces may suffer problems related to the attached dead bacteria. Herein, antibacterial surfaces with multifunctionality and regenerability are fabricated by a universal strategy. Various substrates are first deposited with multilayered films containing guest moieties, which can be further used to incorporate biocidal host molecules, β-cyclodextrin (β-CD) derivatives modified with quaternary ammonium salt groups (CD-QAS). The resulting surfaces exhibit strong biocidal activity to kill more than 95% of attached pathogenic bacteria. Notably, almost all the dead bacteria can be easily removed from the surfaces by simple immersion in sodium dodecyl sulfate, and the regenerated surfaces can be treated with new CD-QAS for continued use. Moreover, when another functional β-CD derivative molecule is co-incorporated together with CD-QAS, the surfaces exhibit both functions simultaneously, and neither specific biofunction and antibacterial activity is compromised by the presence of the other. These results thus present a promising way to fabricate multifunctional and regenerable antibacterial surfaces on diverse materials and devices in the biomedical fields.