Chaotropic Effect-Induced Sol–Gel Transition and Radical Stabilization for Bacterially Sensitive Near-Infrared Photothermal Therapy

Deep-seated bacterial infections (DBIs) are stubborn
and deeply
penetrate tissues. Eliminating deep-seated bacteria and promoting
tissue regeneration remain great challenges. Here, a novel radical-containing
hydrogel (SFT-B Gel) cross-linked by a chaotropic effect was designed
for the sensing of DBIs and near-infrared photothermal therapy (NIR-II
PTT). A silk fibroin solution stained with 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tris(1-methylpyridin-1-ium)
(TPT3+) was employed as the backbone, which could be cross-linked
by a closo-dodecaborate cluster (B12H122–) through a chaotropic effect to form
the SFT-B Gel. More interestingly, the SFT-B Gel exhibited the ability
to sense DBIs, which could generate a TPT2+• radical
with obvious color changes in the presence of bacteria. The radical-containing
SFT-B Gel (SFT-B★ Gel) possessed strong NIR-II absorption and
a remarkable photothermal effect, thus demonstrating excellent NIR-II
PTT antibacterial activity for the treatment of DBIs. This work provides
a new approach for the construction of intelligent hydrogels with
unique properties using a chaotropic effect.

深部细菌感染（DBIs）根深蒂固，对组织造成深刻渗透。根除深部细菌及促进组织再生构成了巨大的挑战。本研究中，一种新型的含自由基的水凝胶（SFT-B Gel）通过盐析效应进行交联，被设计用于深部细菌感染的传感及近红外光热疗法（NIR-II PTT）。采用4,4′,4″-(1,3,5-三嗪-2,4,6-三基)-三(1-甲基吡啶-1-ium)（TPT3+）染色的丝素蛋白溶液作为骨架，能够通过盐析效应与环十二硼烷簇（B12H122–）交联形成SFT-B Gel。更有趣的是，SFT-B Gel展现了传感深部细菌感染的能力，在细菌存在的情况下，能够产生明显的颜色变化的TPT2+•自由基。含自由基的SFT-B Gel（SFT-B★ Gel）具备优异的NIR-II吸收性和显著的光热效应，从而展现出卓越的NIR-II PTT抗菌活性，用于治疗深部细菌感染。本研究为利用盐析效应构建具有独特性质智能水凝胶的新方法提供了新思路。