Selective choline biosensors based on choline oxidase co-immobilized into self-assembled monolayers on micro-chips at low potential

Abstract

We fabricate a choline-biosensor that exhibits excellent specific and selective recognition for selected biological molecules coexisting with other analytes in a buffer system at low potential. This novel sensor is a well-organized design with the enzyme choline oxidase (ChOx) immobilized onto a micro-chip for selective choline (Ch) detection. This reusable and sensitive Ch biosensor is developed based on mediator-free ChOx self-assembled monolayers (SAM) on a micro-chip. Cyclic voltammetry (CV) technique was employed with the enzyme fabricated chips in phosphate buffer solution (PBS, 0.1 M) under room conditions. The analytical parameters of ChOx fabricated electrode displayed a lower detection limit (DL, 0.012 ± 0.005 nM), a wide linear dynamic range (LDR, 0.05 nM to 10.0 μM), good linearity (R = 0.9938), and higher sensitivity (3.5 μA μM⁻¹ cm⁻²), where only a small sample volume (50.0 μL) was analyzed. The micro-chip system exhibits a simple and efficient approach to immobilize oxidative enzymes onto thioglycolic acid (TGA) SAM modified surfaces, which could improve the biosensor detection of a large group of biomolecules for a broad range of biomedical applications in health care. This integrated micro-chip provides a promising low-cost platform for the sensitive and rapid detection of biomolecules using small samples.