Biosensor using evanescent wave cavity ring-down spectroscopy (EWCRDS)

Biosensor is a device that uses biochemical elements to detect a chemical compound or changes in the environment. It is comprised of a sensitive biological element and a physicochemical detector. This research demonstrated a proof-of-concept for detection of antigen-antibody interaction using evanescent-wave cavity ring down spectroscopy (EW-CRDS), with aminoparathion conjugated to BSA as the antigen and labeled anti-parathion antibody.;A large increase in extinction coefficient was observed when the labeled anti-parathion antibody binds to the parathion-BSA immobilized on the prism. The increase in extinction coefficient is due to (1) evanescent field disturbance causing radiation scattering although no net energy flow is observed; (2) absorbance or fluorescence of molecules entering the evanescent field causing a net flow of energy from the radiating surface to the molecule in order to maintain the evanescent energy. Reversible immobilization of protein on the glass slide has been demonstrated and will be tested on the prism in the future. Further studies are underway in developing the EW-CRDS technique in detecting antigen-antibody interaction.