An Electrochemical Biosensor with Nano-Interface for Lactate Detection Based on Lactate Dehydrogenase Immobilized on Iron Oxide Nanoparticles

An abrupt change in the concentration of lactate in children below the age of three has been related to hepatic immaturity. An electrochemical lactate biosensor was developed by successfully binding lactate dehyrogenase (LDH) onto Fe3O4 nanoparticles via nafion. Towards this design, Fe3O4 nanoparticles were synthesized by thermal co-precipitation method of ferric and ferrous chlorides. The structural and morphological properties of iron oxide (Fe3O4) nanoparticles were characterized using X-ray Diffractometer (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM) respectively. Polycrystalline nature of Fe3O4 nanoparticles was confirmed from the XRD data. The size of the spherical shaped Fe3O4 nanoparticles was found to be 24.97 +/- 4.98 nm. Fourier Transform Infrared Spectroscopy (FT-IR) was used to confirm the binding of LDH to Fe3O4 nanoparticles. A lactate detecting electrochemical biosensor was developed by fabricating a gold electrode modified with Fe3O4 nanoparticles for LDH immobilization (Au/NanoFe(3)O(4)/LDH). Amperometric and cyclic voltammetric current of lactate biosensor were used as an analytical signal to study the detection mechanism of lactate. An appreciable linear response to lactate at concentrations ranging from 0.02 to 0.14 mu mol L-1 was observed with the response time of < 1 s, detection limit of 1.28 nmol L-1, quantification limit of 4.22 nmol L-1 and sensitivity of 320 nA nM(-1) cm(-2). The apparent Michaelis-Menten constant (K-M(app)) and maximum change in current (I-max) values measured of the immobilized LDH were 0.024 +/- 1.3 x 10(-2) mu mol L-1 and 0.98 mu A respectively. The developed bio-electrode with nano-interface showed high stability and very good reproducibility.