Ultrasensitive Detection of Protein with Wide Linear Dynamic Range Based on Core-Shell SERS Nanotags and Photonic Crystal Beads

Detection of proteins in a wide concentration range from fg mL^-1 to sub mg mL^-1 is a challenge in the high throughput analysis of precision medicine. Herein, we proposed a biosensor consisting of core-shell surface-enhanced Raman scattering (SERS) nanotags as labels and photonic crystal beads (PCBs) as carriers for ultrasensitive detection of proteins. In practice, Raman dyes (RDs) were embedded in the interface of gold core and silver shell in the bimetal nanoparticles to form SERS nanotags. It was found that the sensitivity was significantly improved due to the enhanced Raman signal by the coupling of the core-shell structure and linear dynamic range (LDR) was extended owing to the high surface to volume ratio of PCBs as well. In addition, we also demonstrated that the biosensor exhibited fine stability and low background, which has great application potential in the detection of protein biomarkers.