Glucose-bridged silver nanoparticle assemblies for highly sensitive molecular recognition of sialic acid on cancer cells via surface-enhanced raman scattering spectroscopy

The expression levels of glycans on the surfaces of cancer and normal cells show different, however, this difference is not noticeable enough to distinguish them directly. So, herein, based on the targeted molecular recognition of the glycans on cell surfaces by 4-mercaptophenyl boronic acid (MPBA), a novel surface-enhanced Raman scattering (SERS) nanoprobe (glucose-MPBA@AgNPs) was prepared by inducing controllable assembly of MPBA decorated Ag nanoparticles (MPBA@AgNPs) in a certain level via the bridge of glucose to amplify such a limited difference in SERS measurements. On the basis of the aggregation-induced 3D SERS hot spot effect, this multi-particle nanoprobe possesses over 10 times stronger SERS enhancement ability than the individual MPBA@AgNPs. As the different sialic acid (SA) expression on the surfaces of cancer and normal cells led to the different accumulation of glucose-MPBA@AgNPs, the results we obtained (mean intensities recorded from five cells) indicate the SA amounts on two kinds of cells can provide 5-7 times signal contrast grade in SERS band intensities (P < 0.001). Compared with the monodispersed nanoprobe, our developed nanoprobe amplifies the SA expression difference on cell surfaces and supports high sensitivity for cancer cell recognition, which might be useful in providing highly effective recognition of the edges of tumor tissues in clinic field.