Supramolecular Porphyrin Photosensitizers - ACS Publications

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Supramolecular Porphyrin Photosensitizers: Controllable Disguise and Photoinduced Activation of Antibacterial Behavior Linghui Chen,† Haotian Bai,‡ Jiang-Fei Xu,*,† Shu Wang,‡ and Xi Zhang*,† †

Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China ‡ Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China S Supporting Information *

ABSTRACT: A series of supramolecular photosensitizers were fabricated from porphyrin derivatives (Por) containing quaternary ammonium groups with cucurbit[7]uril (CB[7]) based on host−guest interactions. The antibacterial activity of Por in the dark could be turned off upon binding with CB[7], whereas the antibacterial activity under white-light illumination could be turned on. In addition, its antibacterial efficiency could be greatly enhanced by introducing metal ions. When Pd(II) was introduced into porphyrin, its antibacterial efficiency was enhanced from 40 to 100%. It should be noted that these small molecules showed little to no cytotoxicity toward mammalian cells even at concentrations higher than those under the antibacterial condition studied. This line of research will provide a strategy for germicides consisting of quaternary ammonium groups to fight against bacterial accumulation in the long term and holds huge potential for application in the real world. KEYWORDS: supramolecular materials, photodynamic therapy, host−guest interactions, cucurbituril chemistry, antibacterial control

1. INTRODUCTION Quaternary ammonium compounds, as a kind of efficient antibacterial agent, have been widely used to kill various bacteria in clinical therapy, agricultural utilization, and sewage treatment.1−5 However, active quaternary ammonium compounds nonselectively kill both beneficial microbes and pathogens when exposed and accumulated in nonclinical habitats and the environment.6−11 Therefore, regulating the activity of the bactericides in demand has drawn increasing attention. Several treatment strategies have been reported to solve the problem of accumulation of active germicides. Zhang and co-workers fabricated polypseudorotaxanes with controlled antibacterial activity by tuning the ratio of cucurbit[7]uril (CB[7]) bound to cationic polymers.12 Wang and co-workers reported a supramolecular conjugated polymer as an antibiotic switch to reversibly regulate antibacterial activity on the basis of demand by assembly and disassembly processes.13 These above strategies and methods relied on host−guest interactions to prevent the accumulation of active germicides, but their antibacterial activities needed to be turned on by additional guest molecules. In this work, we introduced photodynamic therapy (PDT) as an alternative treatment for clinical application. PDT, as a Food and Drug Administration-approved therapeutic modality, has been widely used in clinical therapy.14−20 Photosensitizers can sensitize the surrounding oxygen to produce reactive oxygen species (ROS) under light irradiation, which exhibit high antibacterial activity.21−23 However, ROS exhibit an instanta© XXXX American Chemical Society

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