Direct Determination of Redox Statuses in Biological Thiols and Disulfides with Noncovalent Interactions of...

The three most important redox couples, including cysteine (Cys)/cystine (Cyss), homocysteine (Hcys)/homocystine (Hcyss), and reduced glutathione (GSH)/glutathione disulfide (GSSG), are closely associated with human aging and many diseases. Thus, it is highly important to determine their redox statuses at the following two levels: (i) the redox identity in different thiols/disulfides and (ii) the redox ratio in a mixture of a specific couple. Herein, by using one single AIE-doped (AIE, aggregation-induced emission) photonic-structured poly(ionic liquid) (PIL) sphere as a virtual sensor array, we realize a direct determination of the redox status without a reducing pretreatment of disulfides, which will greatly promote the development of high-throughput and simple procedures. The pattern-recognition method uses the multiple noncovalent interactions of imidazolium-based PILs with these redox species to produce differential responses in both the photonic crystal and fluorescence dual channels. On the one hand, a single sphere enables the direct and simultaneous discrimination of the redox identities of Cys, Cyss, Hcys, Hcyss, GSH, and GSSG under the interference of other five commonly occurring thiols. On the other hand, this sphere also allows for not only a direct quantification of the GSH/GSSG ratios without previously determining the individual concentrations of GSH and GSSG but also the accurate prediction of the ratios in unknown redox samples. To further demonstrate applications of this method, redox mixtures in a biological sample are differentiated. Additionally, quantum calculations further support our assignments for interactions between the imidazolium-based PILs and these redox species.