Prostate specific antigen detection in patient sera by fluorescence-free BioCD protein array

Fluorescence-free biosensor arrays for protein detection directly measure the protein surface density, and do not require a fluorophore or enzyme label, and provide quantitative and consistent signals. However, few fluorescence-free biosensor protein arrays have demonstrated successful application in high-background samples, such as serum, due to non-specific binding. We tested the BioCD as a fluorescence-free biosensor based on optical interferometry, and used it to detect prostate specific antigen (PSA, a biomarker of prostate cancer) in patient sera in a 96-well anti-PSA microarray. We have attained a 4 ng/ml detection limit in serum and have measured PSA concentrations in patient sera. The measured concentrations correlated well with enzyme-linked immunosorbent assay (ELISA) results. The measurement of PSA concentrations in high-level protein backgrounds suggests that the BioCD has a potential for clinical applications by removing the restriction of fluorescence-free biosensors from high-background applications.