Naked eye detection of glutathione in living cells using rhodamine B-functionalized gold nanoparticles coupled with FRET

In this study, functionalized gold nanoparticles, in combination with fluorescence resonance energy transfer (FRET), was utilized to visually detect glutathione (GSH) in aqueous samples and then demonstrated its applicability by estimating GSH level in living cells. We first modified the Au NPs with rhodamine B (RB), ON state of FRET, using the electrostatic interaction. In the presence of GSH, the competitive reaction between RB-functionalized nanoprobes (RB-Au NPs) and GSH caused the release of RB molecules from Au NP surface, OFF state of FRET, which was monitored simply by the naked eye. Fluorescence spectra and UV–vis absorption spectra were employed to investigate the spectroscopic characteristics of nanoprobes. Furthermore, the assay conditions, such as nanoprobe concentration, reaction time and the influence of interferent, were investigated. The visible color change of RB-Au NPs solution from dark blue to red in the presence of GSH was observed when the GSH concentration exceeded 10 μM. This one-step naked eye detection depicted here successfully applied for the sensing of human hepatoma (HepG2) intracellular GSH level, showing the potential use in clinical nanodiagnosis. This method allows the rapid colorimetric detection of intracellular GSH without any preliminary treatment and specific instruments.

► A one-step glutathione naked eye detection method was developed using functionalized nanoprobes coupled with FRET. ► Fluorescent nanoprobes were fabricated by rhodamine B-functionalized gold nanoparticles. ► The visual detection limit of glutathione was around 10 μM. ► This method was applied to sense glutathione level in living cells.