Benefiting from their inherent localized and controlled release properties, hydrogels are ideal delivery systems for therapeutic drugs or nanoparticles. In particular, applications of hydrogels for the delivery and release of photoresponsive drugs or nanoparticles are receiving increasing attention. However, the effect of the hydrogel matrix on the fluorescence emission and singlet oxygen generation efficiency of the embedded photosensitizers (PSs) has not been clarified. Herein, meso-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP) as a water-soluble PS was encapsulated into an injectable hydrogel formed by glycol chitosan and dibenzaldehyde-terminated telechelic poly(ethylene glycol). Compared to free TMPyP solution, the TMPyP encapsulated in the hydrogel exhibits three distinct advantages: (1) more singlet oxygen was generated under the same laser irradiation condition; (2) much longer tumor retention was observed due to the low fluidity of the hydrogel; and (3) the fluorescence intensity of TMPyP was significantly enhanced in the hydrogel due to its decreased self-quenching effect. These excellent characteristics lead to remarkable anticancer efficacy and superior fluorescence emission property of the TMPyP–hydrogel system, promoting the development of imaging-guided photodynamic therapy.

中文翻译：

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用于成像引导光动力癌症治疗的可注射水凝胶中嵌入的光敏剂的增强的荧光发射和单线态氧的产生

得益于其固有的局部和控制释放特性，水凝胶是治疗药物或纳米颗粒的理想输送系统。特别地，水凝胶在光反应性药物或纳米颗粒的递送和释放中的应用正受到越来越多的关注。但是，水凝胶基质对嵌入式光敏剂（PSs）的荧光发射和单线态氧产生效率的影响尚不清楚。在此，将作为水溶性PS的中四（1-甲基吡啶-4-基）卟啉（TMPyP）封装到由乙二醇壳聚糖和二苯甲醛封端的远螯聚（乙二醇）形成的可注射水凝胶中。与游离TMPyP溶液相比，包裹在水凝胶中的TMPyP具有三个明显的优势：（1）在相同的激光辐照条件下产生了更多的单线态氧；（2）由于水凝胶的低流动性，观察到更长的肿瘤保留时间；（3）TMPyP的荧光强度由于其自猝灭作用的降低而显着增强。这些优异的特性导致TMPyP-水凝胶系统具有卓越的抗癌功效和出色的荧光发射特性，从而促进了影像引导光动力疗法的发展。