A Novel Immobilization Enzyme Lactate Fluorescence Capillary Biosensor

Lactate dehydrogenase (LDH) was immobilized in inner surface of a medical capillary (45 mm × 0.9 mm i.d.), and an immobilization enzyme lactate fluorescence capillary biosensor (IE-LFCBS) was made. Rapid microanalysis for lactate was realized using it. When the IE-LFCBS sucked the mixture solution of coenzyme I (NAD+) and lactate in it, under catalysis of immobilized lactate dehydrogenase, NAD+ reacted with lactate and formed reduced nicotinamide adenine dinucleotide (NADH), and then fluorescence intensity of NADH in the IE-LFCBS was determined at 353 nm of excitation and 466 nm of emission waves to quantify lactate. Optimized experimental conditions suitable for the biosensor are as follows: the reaction time is 15 min, the test temperature is 38°C, the concentrations of tris buffer (pH 8.8) and NAD+ are 0.1 M and 4.0 M, respectively; the concentration of LDH for immobilization is 60 kU l−1. The range of determination is from 1.0 to 5.0 mM, the detection limit is 0.45 mM, and the recovery is 95%–98% as well as RSD ≤ 1.5% (n = 11). The biosensor has a good reproducibility, long-term stability, and it can be used repeatedly. It can be applied for rapid determination of lactate in ferment foodstuff, leechdom, blood samples, and so on.