Teaching a fluorophore new tricks: Exploiting the light-driven organic oxidase nanozyme properties of thiazolothiazole for highly sensitive biomedical detection

The development of light-driven organic nanozymes possessing photoactivity is of great significance in biomedical research and biosensing given that they exhibit prominent absorption and fascinating photocontrollability in the visible range. However, the number and availability of such nanozymes is quite low. In this work, N-arylpyridinium thiazolothiazole (N, N '-dichlorophenzyled dipyridinium thiazolo[5,4-d]thiazole difluoride, TTz-Cl2+), which exhibits inherent light-driven oxidase-mimicking activity, was synthesized and it was found that 3,3 ',5,5 '-tetramethylbenzidine (TMB) could be oxidized under visible light, and also underwent corresponding changes in color and absorption. Moreover, the enzymatic activity of TTz-Cl2+ could be modulated precisely by switching the visible light on and off. Glutathione (GSH), an important biological antioxidation regulator, was shown to be capable of successfully impeding the catalytic functions of TTz-Cl2+. Thus, it proved possible to fabricate a facile photo-triggered colorimetric sensing system for detection of GSH based on the use of the TTz-Cl2+ and TMB system. The sensor exhibited satisfactory analytical performance with a linear range of 1-17 mu M and a detection limit of 0.47 mu M and may be used to determine GSH in HeLa cell lysates with good selectivity and high sensitivity. This work not only extends the availability of organic nanozymes but also broadens the applications base of thiazolothiazole derivatives in biomedical analysis.