Visual fluorescence detection of H sub(2)O sub(2) and glucose based on "molecular beacon"-hosted Hoechst dyes

• Published in: Analyst (London) 2015-05, Vol.140 (10), p.3642-3647
• Main Authors: Lu, Ling-Fei, Li, Yan-Yun, Zhang, Min, Shi, Guoyue
• Format: Article
• Language: English
• Subjects: Biosensors; Cysteine; Dyes; Fluorescence; Glucose; Grabs; Marking; Saliva
• ISSN: 0003-2654; 1364-5528
• DOI: 10.1039/c5an00499c

In this work, a label-free molecular beacon (MB)-like biosensor is designed for the determination of H sub(2)O sub(2) and glucose based on the fluorescence regulation of Hoechst dyes hosted by the designed AT-rich single-stranded DNA (ssDNA), in which Hg super(2+) and cysteine (Cys) act as activators. The designed AT-rich ssDNA (ATprobe) can be directed to form a hairpin with an Hg super(2+)-induced T-Hg super(2+)-T complex, which provides a medium for enhancing the fluorescence of Hoechst dyes significantly. On the other hand, Cys can effectively grab Hg super(2+) from the T-Hg super(2+)-T complex by thiol-Hg super(2+) interactions, destructing the hairpin and then switching the Hoechst dyes to the fluorescence "off" state. Combined with these properties, we have demonstrated its application for label-free fluorescence "turn on" detection of H sub(2)O sub(2). The sensing mechanism is based on the specific reaction between H sub(2)O sub(2) and Cys catalyzed by I super(-), the resulting disulfide reverses the Cys-mediated fluorescence decrease of the MB-hosted Hoechst dyes. The approach achieves a low detection limit of 0.1 mu M for H sub(2)O sub(2). Moreover, this method is further applied to the noninvasive detection of glucose in artificial saliva and urine samples, combining with glucose oxidase (GOx) for the oxidation of glucose and formation of H sub(2)O sub(2). Compared to traditional methods, the proposed design is cost-effective, simple to prepare and manipulate without fluorescence labeling or chemical modification.