Label-Free and Rapid Detection of Anthrax Protective Antigen by Surface-Enhanced Raman Scattering on Au Nanorods

Aiming at the requirement of ultra-sensitive on-site rapid detection of anthrax protective antigens (PA), we proposed a label-free detection scheme based on surface-enhanced Raman Scattering (SERS) on Au nanorods (AuNRs) substrate that we fabricated. The Raman spectrum of anthrax protective antigen was reported for the first time. The limit of detection (LOD) of PA on the AuNRs was characterized to be 100 pg/mL. To simulate the actual detection of PA in human serum albumin (HSA), the label-free detection of HSA based on the AuNRs SERS substrate was studied in this paper. The characteristic peaks of the obtained HSA spectrum are consistent with the previously reported literature. The SERS label-free detection of PA in HSA solution has also been achieved. The limit of detection of the PA in HSA solution can also reach 100 pg/mL, which is much lower than the PA concentration of 100 μg/mL in human serum after anthrax infection. A good linear relationship between the peak intensity of the mixture spectrum and the logarithm of the concentration of PA was obtained with the correlation coefficient to be 0.9769. Using Principal Component Analysis (PCA) method, the SERS data of PA, HSA and the mixture can be classified into three completely separated areas without overlap. The entire testing process will cost only about eight minutes, which is much faster than the mature technology, such as Enzyme-linked Immunosorbent Assay (ELISA).