Protein-Functionalized Gold Nanoparticles for Antibody Detection Using the Darkfield Microscopic Observation of Nanoparticle Aggregation.

Gold nanoparticles (AuNPs) are commonly used in biosensing applications. In this study, AuNPs were synthesized by using reduced bovine serum albumin (rBSA) as the reducing agent. The rBSA conjugated with AuNPs via Au-Sulfur interactions to form rBSA-functionalized AuNPs (rBSA-AuNPs). The interaction of the rBSA moieties on the rBSA-AuNP surface with an anti-BSA antibody (anti-BSA) led to AuNP aggregation, which enabled the successful detection of anti-BSA at a concentration as low as 20 nM through darkfield microscopy (DFM). This study demonstrates the potential applications of protein-functionalized AuNPs in the bioanalysis of substances through DFM.