Strong SERS signal enhancement in living cells

Gold nanoflowers can increase the signal in SERS by as much as 100 million-fold and have been used as tags for imaging studies of living cells. These remarkable improvements were illustrated by Chinese scientists from Peking University and the Institute of Physics in Beijing in Small.

Using 4-mercaptopyridine as a probe molecule, the nanoflowers were deposited individually on a silicon wafer without aggregation and the SERS enhancement factor was found to be 4.5 x 10⁸, independent of the polarisation angle of the spectra.

For studies on living cells, the gold nanoflowers were capped with 4-mercaptopyridine and pegylated before conjugation with folic acid and incubation with human hepatocellular carcinoma cells, which are known to express the folic acid receptor. High-quality SERS images were obtained and the shapes of the cells could be observed.

The nanoflowers "have great potential advantages as highly sensitive SERS imaging nanoprobes for targeting and imaging specific biomarkers distributed on the cell membrane" and could be improved further by the incorporation of probes with larger Raman cross sections.