Monoclonal antibody-gold biosensor chips for detection of depurinating carcinogen-DNA adducts by fluorescence line-narrowing spectroscopy

A new direct readout methodology for detection and quantitation of fluoresc ent carcinogen-DNA adducts is described. It combines the binding specificit y of an immobilized monoclonal antibody (MAb) with high-resolution, low-tem perature fluorescence spectroscopy. The MAb, which is covalently bound to a gold surface via a chemisorbed disulfide coupling agent, binds the adduct of interest in an aqueous sample. Laser-induced fluorescence under nonline narrowing (FNLN) and Line-narrowing (FLN) conditions was used to detect (be nzo[a]pyren-6-yl)guanine (BP-6-N7Gua) bound to immobilized MAb. At room tem perature, the BP-6-N7Gua fluorescence was not detected, most likely because of quenching by the gold surface and/or efficient dynamical quenching. How ever, fluorescence was observed at room temperature when the surface was co vered with a thin layer of glycerol, and possible reasons for the fluoresce nce enhancement are considered. Lowering of the temperature to 77 K led to nearly an order of magnitude increase in fluorescence intensity. Highly str uctured FLN spectra obtained at 4.2 K allowed for definitive adduct identif ication. The potential of this methodology for risk assessments of individu als exposed to polycyclic aromatic hydrocarbons is discussed.