Label-free detection of prostate-specific antigen with FBAR-based sensor with oriented antibody immobilization

This paper reports a real-time, label-free detection of prostate-specific-antigen (PSA) through mass sensing with film bulk acoustic resonator (FBAR) coated with an oriented antibody layer. The oriented antibody layer is produced with protein A forming a polarized bond between antibody, at the Fc (fragment crystallizable) region of an IgG (immunoglobulin G), and a gold layer. The first prototype sensor is capable of detecting PSA concentration in hundreds of nanogram per milliliter range, and can be regenerated with 0.1 M glycine pH 2.5 that strips off only the antibody-antigen complex. Also, preliminary testing shows the absence of cross-reaction with bovine serum albumin (BSA). An improved version of the sensor utilizing DTSSP (3,3′-Dithiobis[sulfosuccinimidylpropionate]) crosslinker shows a better response, and increases the sensitivity to a level where PSA detection down to nanograms per milliliter range is possible.