Enhanced NADH Oxidation Using Polytyramine/Carbon Nanotube Modified Electrodes for Ethanol Biosensing

Abstract

Polytyramine (PT) has been electro‐deposited onto multi‐walled carbon nanotube (MWCNT) modified glassy carbon (GC) electrodes via oxidation of tyramine in 0.1 M H3PO4 by cycling the potential over the range of −400 mV to 1300 mV (versus Ag/AgCl). The reactivity of the resulting chemically‐modified electrodes was characterized using cyclic voltammetry in the presence and absence of reduced nicotinamide adenine dinucleotide (NADH). The modified electrodes displayed electrochemical activity due to the formation of quinone species and were catalytically active towards NADH oxidation by lowering the oxidation peak potential by 170 mV compared to the value of the MWCNT modified electrode with a peak potential of 180±10 mV (versus Ag/AgCl). The MWCNT/PT surface was further characterized using SEM and XPS methods, which indicated that a thin polymeric film had been formed on the electrode surface. The present work demonstrates the advantage of using PT as a platform that combines both the immobilization of alcohol dehydrogenase (ADH) and the mediation of NADH oxidation at a low overpotential essential to the design of high performance ethanol biosensors, all within an easily electropolymerizable film. The resulting biosensor displayed an ethanol sensitivity of 4.28±0.06 μA mM−1 cm−2, a linear range between 0.1 mM and 0.5 mM and a detection limit of 10 μM.

Variation of Carbon Based Materials on the Electropolymerization of Tyramine

“…Upon electropolymerization of tyramine at both GC/GraphC and GC/CVD‐MWCNT electrodes, multiple processes emerge with repetitive cycling. These redox couples have been attributed to the formation of quinone functional groups . This survey of the voltammograms revealed that substantial variation in the nature of PT and quinone functional groups occurred upon electropolymerization.…”

“…We have recently reported polytyramine (PT) is a suitable candidate for use as a NADH oxidation mediator in biochemical applications . Tyramine oxidation in acidic media results in electropolymerization occurring through the ortho ‐position of the phenol moiety, leading to a polymer that carries free amino groups for potential enzyme immobilization .…”

“…In addition, quinone functional groups in PT can catalyze NADH oxidation. PT has an advantage over traditional mediators such as polyphenoazines and polyphenothiazines due to its ability to both facilitate NADH oxidation at a low over potential and provide anchoring sites for enzyme immobilization, all within the same compound .…”

Multi‐walled Carbon Nanotubes Non‐covalently Functionalized with Polyarginine: A New Alternative for the Construction of Reagentless NAD+/Dehydrogenase‐based Ethanol Biosensor

“…The great limitation of dehydrogenase‐based systems in general, and NAD + ‐dehydrogenase‐based systems, in particular, is that, in contrast to oxidases, which have redox cofactors tighly bound to the enzyme, the cofactors are not bound to the enzyme, and it is necessary to add them to perform each determination . In fact, most of dehydrogenase‐based biosensors involve the addition of NAD + cofactor to the supporting electrolyte , but it makes the determination time‐consuming and expensive. Therefore, new strategies are required for the construction of reagentless dehydrogenase‐based electrochemical biosensors in which both, the enzyme and NAD + , are effectively immobilized onto the electrode in such a way that the cofactor has easy acces to the enzyme.…”

Indirect Electrochemical Detection of NADH Through an Active Stainless Steel Fiber Felt (SSFF) Electrode Decorated With the Amino‐Graphene/Nafion Nano Composite Films

“…Tyramine is also a redox mediator containing quinone species which display catalytically active towards NADH oxidation. Wilson et al . electrochemically deposited a layer of Poly(tyramine) (PT) on a MWCNT‐covered GCE where NADH was oxidized around 0.2 V. Another redox mediator of quinone family, pyrroloquinoline quinone (PQQ), was ultra‐sonically mixed with graphene fragments and the composite materials were self‐assembled on the surface of a chitosan‐coasted GCE .…”