A cholesterol biosensor based on cholesterol oxidase-poly(diallyldimethylammonium chloride)-carbon nanotubes-nickel ferrite nanoparticles (ChOx-PDDA-CNTs-NiFe2O4NPs) solution is easily fabricated by using a single dropping step on glassy carbon electrode (GCE) surface. This technique is an alternative way to reduce complexity, cost and time to produce the biosensor. The uniformly dispersed materials on the electrode surface enhance the catalytic reaction of cholesterol oxidase and electron transfer from the oxidation of hydrogen peroxide in the system. The nickel ferrite nanoparticles synthesized by co-precipitation and calcination at various temperatures was studied by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and X-ray diffraction (XRD). The synthesized material calcined at 700 degree Celsius was well defined and presented the octahedral metal stretching with cubic NiFe2O4NPs phase. In cyclic voltammetric study, the ChOx-PDDA-CNTs-NiFe2O4NPs/GCE showed 0.43 s-1 charge transfer rate constant (Ks), 7.79 x 10-6 cm2 s-1 diffusion coefficient value (D), 0.13 mm2 electroactive surface area (Ae) and 3.58 x 10-8 mol cm-2 surface concentration (γ). This modified electrode exhibits stability (%RSD = 0.62%, n = 10), reproducibility (%RSD = 0.81, n = 10), high sensitivity (25.76 nA per mg L-1 cm-2), linearity from 1 to 5,000 mg L-1 (R2 = 0.998) with a low detection limit (0.50 mg L-1), Michaelis-Menten constant (Km) of 0.14 mM with 0.92 µA maximum current (Imax) and good selectivity without the effects of electroactive species such as ascorbic acid, glucose and uric acid. The cholesterol biosensor was successfully applied to determine cholesterol levels in human blood samples, showing promise due to its simplicity and availability.

Single drop fabrication of the cholesterol biosensor based on synthesized NiFe2O4NPs dispersed on PDDA–CNTs

2019 Fall National Meeting

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