  Mass-sensing biosensor arrays for protein detection require no fluorophores
or enzyme labels. However, few mass biosensor protein arrays have demonstrated
successful application in high background samples, such as serum. In this
paper, we test the BioCD as a mass biosensor based on optical interferometry of
antibodies covalently attached through Schiff-base reduction. We use the BioCD
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 full serum and have measured PSA concentrations in three
patient sera.
