DNA and graphene as a new efficient platform for entrapment of methylene blue (MB): Studies of the electrocatalytic oxidation of β-nicotinamide adenine dinucleotide

CVD graphene as an electrochemical sensing platform for simultaneous detection of biomolecules

The development of electrochemical biosensors for the simultaneous detection of ascorbic acid (AA), dopamine (DA), uric acid (UA), tryptophan (Trp), and nitrite ([Formula: see text]) in human serum is reported in this work. Free-standing graphene nanosheets were fabricated on Ta wire using the chemical vapor deposition (CVD) method. CVD graphene, which here served as a sensing platform, provided a highly sensitive and selective option, with detection limits of AA, DA, UA, Trp, and [Formula: see text] of 1.58, 0.06, 0.09, 0.10, and 6.45 μM (S/N = 3), respectively. The high selectivity of the electrode is here explained by a relationship between the bandgap energy of analyte and the Fermi level of graphene. The high sensitivity in the oxidation current was determined by analyzing the influence of the high surface area and chemical structure of free-standing graphene nanosheets on analyte adsorption capacity. This finding strongly indicates that the CVD graphene electrode can be used as a biosensor to detect five analytes in human serum.

Single-walled carbon nanotubes covalently functionalized with polytyrosine: A new material for the development of NADH-based biosensors

We report for the first time the use of single-walled carbon nanotubes (SWCNT) covalently functionalized with polytyrosine (Polytyr) (SWCNT-Polytyr) as a new electrode material for the development of nicotinamide adenine dinucleotide (NADH)-based biosensors. The oxidation of glassy carbon electrodes (GCE) modified with SWCNT-Polytyr at potentials high enough to oxidize the tyrosine residues have allowed the electrooxidation of NADH at low potentials due to the catalytic activity of the quinones generated from the primary oxidation of tyrosine without any additional redox mediator. The amperometric detection of NADH at 0.200V showed a sensitivity of (217±3)µAmM(-1)cm(-2) and a detection limit of 7.9nM. The excellent electrocatalytic activity of SWCNT-Polytyr towards NADH oxidation has also made possible the development of a sensitive ethanol biosensor through the immobilization of alcohol dehydrogenase (ADH) via Nafion entrapment, with excellent analytical characteristics (sensitivity of (5.8±0.1)µAmM(-1)cm(-2), detection limit of 0.67µM) and very successful application for the quantification of ethanol in different commercial beverages.