Synthesis and characterization of reporter molecules embedded core-shell nanoparticles as SERS nanotags

Abstract

Surface-enhanced Raman scattering (SERS) spectroscopy is presented as a sensitive and specific molecular tool for clinical diagnosis and prognosis monitoring of various diseases including cancer. In order for clinical application of SERS technique, an ideal method of bulk synthesis of SERS nanoparticles is necessary to obtain sensitive, stable and highly reproducible Raman signals. In this contribution, we determined the ideal conditions for bulk synthesis of Raman reporter (Ra) molecules embedded silver-gold core-shell nanoparticles (Au@Ra@ AgNPs) using hydroquinone as reducing agent of silver nitrate. By using UV-Vis spectroscopy, Raman spectroscopy and transmission electron microscopy (TEM), we found that a 2:1 ratio of silver nitrate to hydroquinone is ideal for a uniform silver coating with a strong and stable Raman signal. Through stability testing of the optimized Au@Ra@AgNPs over a two-week period, these SERS nanotags were found to be stable with minimal signal change occurred. The stability of antibody linked SERS nanotags is also crucial for cancer and disease diagnosis, thus, we further conjugated the as-prepared SERS nanotags with anti-EpCAM antibody, in which the stability of bioconjugated SERS nanotags was tested over eight days. Both UV-Vis and SERS spectroscopy showed stable absorption and Raman signals on the anti-EpCAM conjugated SERS nanotags, indicating the great potential of the synthesized SERS nanotags for future applications which require large, reproducible and uniform quantities in order for cancer biomarker diagnosis and monitoring.