Nanochemistry and biotechnology

A New Sensor Platform for Specific Monitoring of Dehydrogenase Activity.
Biloivan O. 1, Boichuk Yu. 1, Sorokin O.1 Istrate O.-M. 2, Rotariu L.2, Bala C.3, Singh B.3, Dempsey E. 3., Brett С.4, Barsan M.4, Korpan Ya1.

1Laboratory of Biomolecular Electronics, Institute of Molecular Biology and Genetics, Natl. Acad. of Sci. of Ukraine. Zabolotnogo street, 150, Kiev-03680, Ukraine. E-mail: o.a.biloivan@edu.imbg.org.ua
2Department of Analytical Chemistry, University of Bucharest, Romaniya.
3Centre for Research in Electroanalytical Technologies (CREATE), Centre of Applied Science for Health (CASH), Institute of Technology Tallaght, Dublin 24, Ireland.
4Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, 3004-535 Coimbra, Portugal

Specific dehydrogenase activity in serum can serve as a diagnostic tool for a number of diseases, including oncological. Electrochemical analysis of dehydrogenase activity can be provided by detection of nicotinamide adenine dinucleotide reduced (NADH) as product of the dehydrogenase-dependent conversion of specific substrate. This study involved design of a high performance nanocomposite sensor for NADH monitoring using screen-printed carbon electrode (SPCE) in response to specific dehydrogenase activity. The surfaces of working carbon electrodes were modified with Nitrogen-doped graphene (NG), detonational nanodiamonds (dNDs) and nanocomposite films with polymers. The effects of various modifications of SPCEs on their electrochemical properties in terms of NADH oxidation were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy EIS and amperometry. 
The optimized electrode (GN/chitosan/SPCE) was used to determine specific activities of lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) in 50 µl probe. The assay employed CV (0.3V, 75mV/s) in 0.1 M phosphate buffer, pH 7.5 with 10 mM NAD+ and 80 mM L-lactate and 5 min sample pre-incubation at 370C for LDH and with 10 mM NAD+ and 60 mM L-malate and 5 min sample pre-incubation at 250C for MDH. The possibility of determining of the LDH or MDH specific activity was demonstrated and reproducibility of the measurement results was verified. The interfering effects of ascorbic acid and NAD+ oxidation on the sensor signal value were investigated.