Nanoparticle-based assay for detection of S100P mRNA using surface-enhanced Raman spectroscopy.

The focus of this work is toward the development of a point-of-care (POC) handheld technology for the noninvasive early detection of salivary biomarkers. The initial of focus was the detection and quantification of S100 calcium-binding protein P (S100P) mRNA found in whole saliva for use as a potential biomarker for oral cancer. Specifically, a surface-enhanced Raman spectroscopy (SERS)-based approach and assay were designed, developed, and tested for sensitive and rapid detection of S100P mRNA. Gold nanoparticles (AuNPs) were conjugated with oligonucleotides and malachite green isothiocyanate was then used as a Raman reporter molecule. The hybridization of S100P target to DNA-conjugated AuNPs in sandwich assay format in both free solution and a vertical flow chip (VFC) was confirmed using a handheld SERS system. The detection limit of the SERS-based assay in free solution was determined to be 1.1 nM, whereas on the VFC the detection limit was observed to be 10 nM. SERS-based VFCs were also used to quantify the S100P mRNA from saliva samples of oral cancer patients and a healthy group. The result indicated that the amount of S100P mRNA detected for the oral cancer patients is three times higher than that of a healthy group.