Boron Cluster Renders Organic Radicals Water-Stable for Photothermal Anti-Infections.

Water-stable organic radicals are promising photothermal conversion candidates for photothermal therapy (PTT). However, organic radicals are usually unstable in biological environments, which greatly hinders their wide application. Here, we have developed a chaotropic effect-based and photoinduced water-stable supramolecular radical (MB12-2) for efficient antibacterial PTT. The supramolecular radical precursor MB12-1 was constructed by the chaotropic effect between closo-dodecaborate cluster (B12H122-) and N,N'-dimethylated dipyridinium thiazolo [5,4-d] thiazole (MPT2+). Subsequently, with triethanolamine (TEOA) serving as an electron donor, MB12-1 could transform to its radical form MB12-2 through photoinduced electron transfer (PET) under 435-nm laser irradiation. The N2 adsorption-desorption analysis confirmed that MB12-2 was tightly packed through the introduction of B12H122-, which effectively enhanced its stability via a spatial site-blocked effect. Moreover, the half-life of MB12-2 in water was calculated through ultraviolet-visible light (UV-vis) absorption spectra results for periods as long as 20 days. In addition, in the skin infection model, MB12-2, as a wound dressing, showed remarkable photothermal antibacterial activity (>97%) under 660-nm laser irradiation and promoted wound healing. This study presents a simple method for designing long-term water-stable supramolecular radicals, offering a novel avenue for noncontact treatments for bacterial infections.

Supramolecularly assisted chlorhexidine-bacterial membrane interaction with enhanced antibacterial activity and reduced side effects.

Bacterial infection has emerged as a grievous threat to public health, and lots of antibacterial agents were developed to solve this issue. However, enhancing the antibacterial activity of antibacterial agents while reducing their side effects remains a challenge. Herein, a supramolecular antibacterial agent based on the host-guest interaction between cucurbit[7]uril (CB[7]) and chlorhexidine (CHX) was designed. CHX can be encapsulated in the cavity of CB[7] to form a 1:3 host-guest complex (CHX-3CB[7]). It was amazingly found that this supramolecular complex could display higher antibacterial activity than CHX alone. Electrospray mass spectrometry and UV-vis spectra revealed that the introduction of CB[7] promoted the protonation of N-atoms on CHX, resulting in stronger ion interaction with phospholipids and thus enhancing the destruction of the bacterial membrane. Scanning electron microscopy (SEM), surface ζ-potentials and outer/inner membrane integrity assays also reveal that the introduction of CB[7] aggravates the rupture of membrane. What is more, the cytotoxicity and irritation of CHX were decreased by forming the host-guest complex with CB[7]. This work provides a paradigm for enhancing antibacterial activity and reducing side effects of drugs through supramolecular chemistry.