Self-assembled CNTs/CdS/dehydrogenase hybrid-based amperometric biosensor triggered by photovoltaic effect

A novel multi-components hybrid material, self-assembled quantum dots (CdS) and glutamate dehydrogenase (GDH) onto multiwall carbon nanotubes (CNTs), was designed for amperometric biosensing system. The ζ-potential and transmission electron microscopy (TEM) analyses confirmed the uniform growth of the CdS/GDH onto carboxyl-functionalized CNTs. Compared with the single CdS, the resulting hybrid material showed more efficient generation of photocurrent upon illumination. The incident light excites CdS and generates charge carriers, and then CNTs facilitates the charge transfer. For dehydrogenase-based biosensor, normally, the cofactor of β-nicotinamide adenine dinucleotide (NAD+) or β-nicotinamide adenine dinucleotide phosphate (NADP+) is necessary. Furthermore, we found the photovoltaic effect of CNTs/CdS/GDH can trigger the dehydrogenase enzymatic reaction in the absence of the NAD+ or NADP+ cofactors. The electrochemical experiment results also demonstrate that the cofactor-independent dehydrogenase biosensing system had series attractive characteristics, such as a good sensitivity (11.9 nA/μM), lower detection limit (up to 50 nM), an acceptable reproducibility and stability. These studies aid in understanding the combination of the semiconductor nanohybrids (CNTs/QDs, etc.) and biomolecules (enzymes, etc.), which has potential for the applications in biosensor, biofuel cell, biomedical and other bioelectronics field.