Raman imaging analysis of intracellular biothiols independent of the aggregation of sensing substrates

The content of biothiols in cells is highly associated with the occurrence and development of several diseases. However, due to their active chemical properties, thiol-contained molecules are normally volatile during the detection process, rendering precise analysis of intracellular biothiols challenging. In this study, 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) is covalently modified on the surface of gold nanorods (AuNRs), constructing sensing substrates for in situ Raman imaging analysis of biothiols in cells. AuNRs are able to serve as ideal surface-enhanced Raman scattering substrates, and thus Raman signals of DTNB are greatly amplified by AuNRs. Meanwhile, the disulfide bond of DTNB can be broken by thiols, thereby releasing part of DTNB from the surface of AuNRs. As a result, three kinds of main biothiols are sensitively quantified with DTNB-modified AuNRs according to the variation of Raman signals, and DTNB-modified AuNRs exhibit far better analytical performance than a commercial probe. In addition, the sensing substrates can be readily delivered to cytoplasm with the transmembrane of AuNRs, and are capable of responding to biothiols in cells. Notably, the Raman approach is established by the breaking of chemical bonds rather than the aggregation of substrates, which is more inclined to analyze intracellular biothiols with a desirable spatial resolution. Therefore, fluctuation of biothiols in glioma cells is evidently observed via Raman imaging. Overall, this work provides an alternative strategy for designing Raman sensors to visualize active molecules in cells.[Figure not available: see fulltext.].