Amperometric sensing of NADH and ethanol using a hybrid film electrode modified with electrochemically fabricated zirconia nanotubes and poly (acid fuchsin)

Porous PtAg nanoshells/reduced graphene oxide based biosensors for low-potential detection of NADH

A superior NADH sensing platform was constructed based on porous PtAg nanoshells supported on reduced graphene oxide (PtAg/rGO) in the absence of any enzymes and redox mediators. The PtAg/rGO composite was prepared via one-step reduction combined with galvanic replacement reaction. The as-made PtAg/rGO assembles multiple structural advantages of coherent conductive matrix, rich electroactive sites, and high specific surface area, accompanied by the unique alloying effect. The PtAg/rGO possesses adequate active reaction sites and fluent electron transport pathway towards the electrocatalytic NADH oxidation, thus presenting significantly increased oxidation current and negative shift of 330 mV in applied potential relative to the bare GCE. By virtues of the outstanding electrocatalytic activity, PtAg/rGO exhibits effective amperometric detection of NADH at 0.15 V within a wide linear concentration range of 2-2378 μM, a high sensitivity of 92.62 μA mM^-1 cm^-2, low detection limit of 0.2 μM, and long-term detection over 2500 s. Moreover, the as-constructed biosensors can achieve accurate NADH detection in human serum samples, indicating its promising application feasibility in fundamental and clinic research. Graphical Abstract Porous PtAg alloy nanoshells supported on reduced graphene oxide (PtAg/rGO) was prepared via a facile one-step reduction and spontaneous replacement reaction strategy. A sensitive and highly stable electrochemical biosensor based on PtAg/rGO is constructed for the quantitative detection of NADH at low applied potential.

A sensitive H2O2 biosensor based on carbon nanotubes/tetrathiafulvalene and its application in detecting NADH

Reduced nicotinamide adenine dinucleotide (NADH) plays a pivotal role in the electron-transfer chain of biological system. Analysis of many biological markers is based on the detection of the enzymatically generated NADH. In this paper, a sensitive hydrogen peroxide (H₂O₂) biosensor, fabricated by carbon nanotubes (CNTs)/tetrathiafulvalene (TTF)/horseradish peroxidase (HRP), was applied for detecting the NADH in a buffer containing methylene blue (MB) at low operating potential of - 0.3 V (vs. Ag/AgCl). Since the NADH could be oxidized by MB to release H₂O₂, the electrochemical biosensor enables to detect the NADH in the MB buffer. And the low working potential made the biosensor avoid the interference from other electroactive substances. Linear response ranges from 10 μM to 790 μM, with a sensitivity of 4.76 μA mM^-1 and a detection limit of 1.53 μM were obtained under the optimum conditions. The proposed sensor provided a promising approach for sensitively detecting the NADH.