Ultrasensitive glutathione detection via competitive binding with carbon dots and gold nanoparticles on SPR chips using fluorescence microscopy–surface plasmon resonance system

Biothiols, such as glutathione (GSH) play vital roles in various physiological processes in the human body, and their abnormal expression will cause serious implications for health. Therefore, the ultrasensitive detection of GSH is of great importance. In this study, we present a novel method for GSH detection using a fluorescence microscopy–surface plasmon resonance (FM-SPR) system, combined with a surface plasmon resonance (SPR) sensor chip functionalized with carbon dots and gold nanoparticles. The proposed method exhibited high sensitivity and specificity for GSH detection in a phosphate-buffered saline (PBS) and 2 % fetal bovine serum (FBS) environment, as low as 0.1 ng/mL GSH can be detected during the range of 0.1–100 ng/mL, with a correlation coefficient (RWu et al. (2004) [ 2 ]) of 0.988 and 0.986 respectively. Moreover, the number of green fluorescence points observed on the FM-SPR chip surface increased with the GSH concentration, correlating well with the corresponding SPR signal changes. To evaluate the performance in more complex solutions, we further validated the method in 2 % FBS. The results demonstrated successful detection of GSH in FBS, achieving a detection limit as low as 0.1 ng/mL and a linear range of 0.1–100 ng/mL with a linearity of 0.986. Notably, in both PBS and FBS, the method maintained excellent selectivity for GSH in the presence of ten potentially interfering amino acids. These findings highlight the potential of this FM-SPR-based biosensing platform for practical applications in the detection of disease-related biomarkers such as GSH.