A novel peptide/Fe 3 O 4 @SiO 2 -Au nanocomposite-based fluorescence biosensor for the highly selective and sensitive detection of prostate-specific antigen.

Highly selective and sensitive detection methods are very important for the early diagnosis of prostate-specific antigen (PSA). Here, we present a novel peptide/Fe3 O4 @SiO2 -Au nanocomposite-based fluorescence biosensor for highly selective and sensitive detection of PSA. The biosensor was made by self-organizing 5-FAM labeled peptides onto the surface of magnetic Fe3 O4 @SiO2 -Au nanocomposites (MNCPs), resulting in efficient quenching of the FAM fluorescence. The PSA specifically recognized and cleaved the 5-FAM-labeled peptides, leading to the fluorescence recovery. This is the first report of the MNCPs by in situ growth of Au nanoparticles (AuNPs) on the SiO2 encapsulated single Fe3 O4 nanocubes. The MNCPs feature robust salt stability, and allow for effective fluorescence quenching and easy magnetic separation, which greatly decrease the background fluorescence. The peptide/MNCPs-based fluorescence biosensor measure a wide range of concentrations of PSA, from 1.0 × 10-12 to 1.0 × 10-9 g/mL, with a limit of detection (LOD) of 3.0 × 10-13 g/mL in both standard solutions and serum samples, demonstrating the great potential of this biosensor platform for use in clinical and biological assays.