Figure 4From: Reproducible and label-free biosensor for the selective extraction and rapid detection of proteins in biological fluids a SERS spectra of pAu/AuNS/Apt/rHuEPO with decreasing concentration of rHuEPO: 10 nM (black), 1 nM (red), 100 pM (green), and 10 pM (blue). b Plot demonstrating the linear relationship between log concentration of rHuEPO and SERS intensity at 1,676 cm−1.Back to article page