NEAR-INFRARED HEPTAMETHINE CYANINE DYES - A NEW TRACER FOR SOLID-PHASE IMMUNOASSAYS

Near-infrared (near-IR) fluorescence has been used to develop a solid- phase immunoassay that detects trace amounts of human immunoglobulin ( HuIgG). Various concentrations of HuIgG bound to a nitrocellulose surf ace were determined from the fluorescence generated by near-IR labeled goat anti-human antibody (GAHG) bound to the HuIgG, The GAHG was labe led with a heptamethine cyanine fluorophore that has spectral properti es in the near-IR region (above 780 nm), These fluorophores are versat ile because they can be modified for several bioanalytical application s, Fluorescence was detected with a near-IR fluorescence instrument pr eviously developed in the laboratory, Two cyanine fluorophore labels w ere evaluated for the ability to selectively bind to GAHG on a nitroce llulose matrix with a minimal amount of background interference, After the most appropriate near-IF fluorophore was selected, the labeling o f GAHG was optimized under aqueous conditions, The most effective GAHG -dye conjugates were used to develop an immunoassay to detect various concentrations of HuIgG. The results are presented, here, Solutions of HuIgG with concentrations as low as 10(-10) molar have been detected with a minimum of interference.