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Molecular interferometric imaging (MI2) is a common-path interferometric imaging technique for detecting protein binding to surfaces. The experimental metrology limit is 10 pm/pixel longitudinal resolution at 0.4-mum diffraction-limited lateral resolution, corresponding to 1.7 attogram of protein, which is only 8 antibody molecules per pixel, near to single-molecule detection. The scaling mass sensitivity at the metrology limit is 5 fg/mm. We demonstrate a protein microarray application in a 128-multiplex immunoassay. Assay applications include prostate specific antigen (PSA) at a detection limit of 60 pg/mL and the cytokine interleukin-5 (IL-5) at a detection limit of 50 pg/mL. Realtime binding assays using MI2 enable the study of reaction kinetics of antibodies exposed to antigen, and the binding of antibody Fc regions to protein G.
Selected Topics in Quantum Electronics, IEEE Journal of (Volume:13 , Issue: 6 )
Date of Publication: Nov.-dec. 2007