A highly sensitive Au@Pd NRs SERS microarray chip based on electrophoretic deposition for detection of GSH in the serum of colorectal cancer patients

In this study, a highly sensitive surface-enhanced Raman scattering (SERS) microarray chip was developed for the detection of reduced glutathione (GSH) in the serum of colorectal cancer (CRC) patients. Gold-palladium nanorods (Au@Pd NRs) with peroxidase-like activity were synthesized and assembled into holes on the polydimethylsiloxane (PDMS)-indium tin oxide (ITO) glass substrate via electrophoretic deposition (EPD). The Au@Pd NRs catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to oxidized TMB (oxTMB) in the presence of hydrogen peroxide (H 2 O 2 ), producing a characteristic SERS peak at 1605 cm −1 . Prior to detection, a thiolated GSH aptamer was immobilized on the microarray chip to specifically capture GSH, effectively avoiding interference from other reducing substances in the complex serum matrix. The captured GSH then reduces oxTMB back to TMB, causing signal attenuation proportional to GSH concentration. The limit of detection (LOD) reached 93 pmol L −1 , with a relative standard deviation (RSD) of 6.36% for reproducibility. Clinical serum analysis of 30 healthy individuals and 30 CRC patients demonstrated results consistent with the gold standard testing method of high-performance liquid chromatography (HPLC) (relative error < 8%), confirming the potential of this approach for the effective detection of GSH and early CRC diagnosis. In this study, a highly sensitive surface-enhanced Raman scattering (SERS) microarray chip was developed for the detection of reduced glutathione (GSH) in the serum of colorectal cancer (CRC) patients.