Cell membrane-targeted surface enhanced Raman scattering nanoprobes for the monitoring of hydrogen sulfide secreted from living cells

Hydrogen sulfide (H₂S), an important gas signal molecule, participates in intercellular signal transmission and plays a considerable role in physiology and pathology. However, in-situ monitoring of H₂S level during the processes of material transport between cells remains considerably challenging. Herein, a cell membrane-targeted surface-enhanced Raman scattering (SERS) nanoprobe was designed to quantitatively detect H₂S secreted from living cells. The nanoprobes were fabricated by assembling cholesterol-functionalized DNA strands and dithiobis(phenylazide) (DTBPA) molecules on core-shell gold nanostars embedded with 4-mercaptoacetonitrile (4-MBN) (AuNPs@4-MBN@Au). Thus, three functions including cell-membrane targeted via cholesterol, internal standard calibration, and responsiveness to H₂S through reduction of azide group in DTBPA molecules were integrated into the nanoprobes. In addition, the nanoprobes can quickly respond to H₂S within 90 s and sensitively, selectively, and reliably detect H₂S with a limit of detection as low as 37 nM due to internal standard-assisted calibration and reaction specificity. Moreover, the nanoprobes can effectively target on cell membrane and realize SERS visualization of dynamic H₂S released from HeLa cells. By employing the proposed approach, an intriguing phenomenon was observed: the other two major endogenous gas transmitters, carbon monoxide (CO) and nitric oxide (NO), exhibited opposite effect on H₂S production in living cells stimulated by related gas release molecules. In particular, the introduction of CO inhibited the generation of H₂S in HeLa cells, while NO promoted its output. Thus, the nanoprobes can provide a robust method for investigating H₂S-related extracellular metabolism and intercellular signaling transmission.