Albumin coated CuInS quantum dots as a near-infrared fluorescent probe for NADH, and their application to an assay for pyruvate.

Water-soluble CuInS quantum dots (QDs) stabilized with 3-mercaptopropionic acid were synthesized in aqueous solution and then coated with bovine serum albumin. The resulting particles display fluorescence with a peak at 680 nm that is effectively quenched by 1, 4-dihydro-nicotinamide adenine dinucleotide (NADH), but not by 1, 4-nicotinamide adenine dinucleotide (NAD). The enzyme lactate dehydrogenase catalyzes the reduction of pyruvate and dehydrogenation of lactic acid using NAD or NADH as a cosubstrate. The new QDs were applied to monitor the course of lactate dehydrogenase-catalyzed reaction of pyruvate by detecting NADH via its quenching effect. This resulted in a convenient and selective detection scheme for pyruvate. The detection limit is as low as 25 nM. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]