The design of fluorescein-ferrocene derivatives as HOCl-triggered turn-on fluorescent probes and anticancer prodrugs

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 51; no. 4; pp. 1533 - 15338
• Main Authors: Wang, Rui-qi, Zhou, Tong, Li, Aimin, Qu, Jian, Zhang, Xin, Zhu, Xiang-feng, Jing, Su
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 18.10.2022
• Subjects: Anticancer properties; Biocompatibility; Cancer; Fluorescein; Fluorescent indicators; Imaging; Selectivity; Sensitivity; Toxicity
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d2dt02198f

Overexpressed HOCl in tumors can behave as an activator for imaging-guided precision therapy. Herein, a new kind of HOCl-activated molecular platform has been developed aiming at the integration of detection, imaging, and anticancer functions. The design strategy uses a five-membered heterocyclic ring to bridge the fluorescent fluorescein part ( FL ) and the anticancer ferrocene part ( Fc ). Three derivatives, namely FL-Fc , FL-NP-Fc and FL-TEG-Fc , were designed with different grafted chains on the fluorescein mother to modulate the hydrophilic and biocompatible capacity. In these molecular platforms, the ferrocene unit serves as the fluorescence emission quencher and masked prodrug. These three could respond to HOCl with good selectivity and sensitivity, showing a turn-on fluorescence signal and anticancer efficacy. FL-TEG-Fc with the highest sensitivity (6.5 × 10 −6 M) was successfully used for imaging endogenous HOCl in AGS cells, in which it presented strong toxicity IC 50 = 9.5 ± 0.3 μM. The mechanistic study revealed that the five-membered heterocyclic ring of FL-TEG-Fc was broken specifically and effectively by HOCl to release strongly fluorescent fluorescein and a bioactive ferrocene derivative; the obtained ferrocene derivative further generated cytotoxic &z.rad;OH through a Fenton-like reaction. This study provides a potential theranostic strategy against HOCl-overexpressing cancers. Fluorescein-ferrocene derivative FL-TEG-Fc designed as HOCl-activated theranostic probe with good selectivity and sensitivity, achieving bright FL imaging with strong cytotoxicity in AGS cells.