Key Words:PHOTOTHERMAL ABLATION; CHARGE RECOMBINATION; INDOCYANINE GREEN; STATE FORMATION; EFFICIENCY; MOLECULES; BODIPY; DESIGN

Abstract:Single -molecule -based synergistic phototherapy holds great potential for antimicrobial treatment. Herein, we report an orthogonal molecular cationization strategy to improve the reactive oxygen species (ROS) and hyperthermia generation of heptamethine cyanine (Cy7) for photodynamic and photothermal treatments of bacterial infections. Cationic pyridine (Py) is introduced at the meso-position of the asymmetric Cy7 with intramolecular charge transfer (ICT) to construct an atypical electron -transfer triad, which reduces A E S1-S0 , circumvents rapid charge recombination, and simultaneously enhances intersystem crossing (ISC) based on spin -orbit charge -transfer ISC (SOCT-ISC) mechanism. This unique molecular construction produces anti -Stokes luminescence (ASL) because the rotatable C-N bond enriched in high vibrational -rotational energy levels improves hot -band absorption (HBA) efficiency. The obtained triad exhibits higher singlet oxygen quantum yield and photothermal conversion efficiency compared to indocyanine green (ICG) under irradiation above 800 nm. Cationization with Py enables the triad to target bacteria via intense electrostatic attractions, as well as biocidal property against a broad spectrum of bacteria in the dark. Moreover, the triad under irradiation can enhance biofilm eradication performance in vitro and statistically improve healing efficacy of MRSA-infected wound in mice. Thus, this work provides a simple but effective strategy to design small -molecule photosensitizers for synergistic phototherapy of bacterial infections. Statement of Significance We developed an orthogonal molecular cationization strategy to enhance the reactive oxygen species and thermal effects of heptamethine cyanine (Cy7) for photodynamic and photothermal treatments of bacterial infections. Specifically, cationic pyridine (Py) was introduced at the meso -position of the asymmetric Cy7 to construct an atypical electron -transfer triad, which reduced A E S1-S0 , circumvented rapid charge recombination, and simultaneously enhanced intersystem crossing (ISC). This triad, with a rotatable C-N bond, produced anti -Stokes luminescence due to hot -band absorption. The triad enhanced antimicrobial performance and statistically improved the healing efficacy of MRSA-infected wounds in mice. This sitespecific cationization strategy may provide insights into the design of small molecule -based photosensitizers for synergistic phototherapy of bacterial infections. (c) 2024 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Volume:178

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Translation or Not:no