Gold-Nanostar-Based Surface-Enhanced Raman Scattering Substrates for Gastric Carcinoma Detection

As a marker of cellular senescence and abnormal apoptosis, overexpression of β-galactosidase (SA-β-gal) is currently associated with many cancers, Alzheimer’s disease, cataracts, osteoporosis, and other diseases related to cellular senescence. SA-β-gal detection using surface-enhanced Raman scattering (SERS) is increasingly in the spotlight because of its acuteness and efficiency. This study aims to construct a sandwich-structure SERS substrate that can detect SA-β-gal in a sensitive, accurate, and cost-effective way, with a limit of detection of 4.79 × 10^–5 U·mL^–1. First, gold nanostars (Au NSs) were self-assembled on glass sheets, forming a monolayer gold surface, and the resulting substrate was defined as a gold nanoflake (Au-NF). Then 4-mercaptophenylboronic acid (PMBA) molecules were assembled on it. Lactose molecules served as a bridge between the substrate and SERS tags and were formed by Au NSs modified by PMBA and 4-aminothiophenol (PATP). When SA-β-gal came in contact with the functionalized Au-NF, with the SERS intensity at 1437 cm^–1, the characteristic peak of 4,4′-dimercaptoazobenzene (DMAB) formed by PATP through laser irradiation decreased, indicating SA-β-gal activity. This structure allows the use of highly SERS-enhanced Au NSs while creating more hot spots between the SERS tags and substrate and improving the signal intensity without losing reproducibility and has potential in serum testing in the future.