Galactosylated silver nanoparticles as a biocompatible intrinsic SERS probe for bladder cancer imaging and ex vivo tumor detection.

The biological application of silver nanoparticles (Ag NPs), which are commonly used as SERS substrates, is often limited by issues related to uncontrolled Ag ion release, resulting in instability and cytotoxicity. In this study, we developed galactosylated Ag@PGlyco-PSMA NPs, a novel biocompatible and bio-SERS platform for sensing small molecules at nanomolar concentration levels, achieving an analytical enhancement factor of 1.71 × 10⁴ alongside intrinsic imaging and labeling capabilities for bladder cancer cells. These Ag NPs were co-synthesized during the polymerization of o-nitrophenyl-β-D-galactopyranoside to form an Ag@polyaniline-based glycopolymer (PGlyco) nanostructure, which was subsequently reacted with poly(styrene-alt-maleic acid) (PSMA). This process stabilized the particle dispersion while generating robust SERS signals due to PGlyco immobilization. By controlling the formation kinetics through the addition of the PSMA polymer at 30 seconds after the reaction of Ag@PGlyco NPs, we observed the formation of aggregate-induced hot spots to evolve PGlyco-related SERS signals arising from interparticle interactions. Our results demonstrated that Ag@PGlyco-PSMA NPs exhibit minimal Ag ion release, resulting in over 80% cell viability across T24, MB49, VERO, and SV-HUC-1 cell lines. Among these cells, Ag@PGlyco-PSMA nanoparticles demonstrated remarkable capability for enhancing cellular uptake, effectively distinguishing bladder cancer cells from normal cells with over 2.6 folds of the signal difference in SERS imaging. The galactose moieties in the PGlyco coating around the Ag@PGlyco-PSMA nanoparticles served as a SERS probe for multivalent binding to bladder cancer cells, enabling cancer imaging diagnosis and tumor-specific detection in accordance with tumor volume growth. Our findings indicated that Ag@PGlyco-PSMA nanoparticles offered intrinsic SERS capability for galactose-mediated bio-interaction and minimal Ag ion release, showing an ideal diagnostic optical platform for in vitro cancer cell imaging and ex vivo tumor progression tracking through bladder SERS detection.