Stable and sensitive SERS-based immunoassay enabled by core-shell immunoprobe and paper-based immunosubstrate

Aiming to augment the reliability and efficiency of surface enhanced Raman scattering (SERS)-active immunoprobe, sophisticated strategies that are able to avoid the dissociation of Raman molecules and noble metal nanoparticles (NPs) in practice have drawn a considerable attention. This study confirmed that Ag@polystyrene-block-poly(acrylic acid)@Ag core-shell nanostructures possessed superior stability compared with bare Ag NPs in phosphate buffer saline solution and human serum. Combined with a unique paper-based immunosubstrate with a satisfying enhancement factor of 9.71 × 10 5 , a robust sandwich immunostructure was constructed and conducted to monitor carbohydrate antigen 19-9 (CA19-9), presenting a low limit of detection of about 10 −4 U/mL. With these exceptional features, such a proposed protocol was finally utilized to detect CA19-9 in several clinical human sera, which shown much higher sensitivity than the traditional chemiluminescence analysis.