Nets of biotin-derived gold nanoparticles as a label for the C-reactive protein immunoassay

This study presents a promising approach for the one-pot generation of the biotin-derived gold nanoparticles (GNPs@biotin). We report a direct method for the reduction of tetrachloroauric acid with biotin and generation of the labels due to nets formed via biotin-streptavidin interactions. The synthesized GNPs@biotin have a characteristic plasmon maximum, excellent colloidal stability, and streptavidin coupling efficiency. The size of the GNPs@biotin:streptavidin nets and the efficiency of interaction with specific antibodies can be easily customized by the component concentrations and time of their interaction. Moreover, the proposed labels require no additional reagents or manipulations for the synthesis, separation, or purification. The developed labels were applied for the detection of the model antigen of C-reactive protein (CRP) as a major inflammation biomarker. The assembling labels demonstrated a competitive advantage limit of CRP detection (LOD) of 1.2 ng/mL and a limit of quantification (LOQ) of 3.9 ng/mL in human plasma comparable to classical immunoassays. Moreover, the proposed approach is universal and can be potentially applied for the quantitative determination of other biomarkers in a variety of immunoassays in a combination with specific biotinylated antibodies.