DETECTION AND IDENTIFICATION OF INDIVIDUAL ANTIGEN MOLECULES IN HUMANSERUM WITH PULSED SEMICONDUCTOR-LASERS

The fluorescence bursts of individual antibody molecules BM-7 (IgG1) l abeled with single dye molecules were detected and identified by the c haracteristic fluorescence lifetimes of the dyes Cy5 (1.5 ns) and JA16 9 (2.7 ns) directly in neat human serum. Fluorescence excitation was p erformed by a short-pulse (FWHM < 400 ps, 50 MHz) semiconductor diode laser. The tumor marker mucine (MUC1) was detected in neat human serum by single-molecule events containing both fluorescence lifetimes indi cating specific binding of both antibody molecules (Cy5-BM-7 and JA169 -BM-7). The sensitivity achieved allows the detection of antigens at c oncentrations below 10(-11) M without separation steps.