Fluorescence biosensing system with a UV-LED excitation for l-leucine detection

A high-sensitive l-leucine biosensors consisting of l-leucine dehydrogenase (LeuDH) immobilized membrane on the edge of a fiber was developed and demonstrated using a high-intensity ultra violet light-emitting diodes (UV-LED) excitation system (λ = 340 nm), an optical fiber probe and a photomultiplier tube. The biosensors were fabricated by attaching l-leucine dehydrogenase immobilized polytetrafluoroethylene (PTFE) membrane with 2-methacryloyloxyethyl phosphorylcholine polymer (PMEH) polymer to the optical fiber. A l-leucine concentration in an aqueous solution was measured by immersing the sensor probes in the phosphate buffer which contained nicotinamide adenine dinucleotide (NAD+) solution. The fluorescent signals of nicotinamide adenine dinucleotide (NADH), produced by enzymatic reactions between NAD+ and an installation of l-leucine solution, were then guided to the photomultiplier tube and a signal detector. The fluorescent intensities were related linearly to the l-leucine concentration from 5 μM to 10 mM. The calibration ranges were acceptable for clinical applications of maple syrup urine disease (MSUD) determinations. High-sensitive and low power consumption of a UV-LED biosensing system allow to be contributed to their enhance quality of life for daily self-care of MSUD patients.