Fabiana A. Gutierrez

Comparative study of the electrochemical behavior and analytical applications of (bio)sensing platforms based on the use of multi-walled carbon nanotubes dispersed in different polymers

This review present a critical comparison of the electrochemical behavior and analytical performance of glassy carbon electrodes (GCE) modified with carbon nanotubes (CNTs) dispersed in different polymers: polyethylenimine (PEI), PEI functionalized with dopamine (PEI-Do), polyhistidine (Polyhis), polylysine (Polylys), glucose oxidase (GOx) and double stranded calf-thymus DNA (dsDNA). The comparison is focused on the analysis of the influence of the sonication time, solvent, polymer/CNT ratio, and nature of the polymer on the efficiency of the dispersions and on the electrochemical behavior of the resulting modified electrodes. The results allow to conclude that an adequate selection of the polymers makes possible not only an efficient dispersion of CNTs but also, and even more important, the building of successful analytical platforms for the detection of different bioanalytes like NADH, glucose, DNA and dopamine.

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.

Characterization of a modified gold platform for the development of a label-free anti-thrombin aptasensor.

This work reports the characterization of a modified gold surface as a platform for the development of a label free aptasensor for thrombin detection. The biorecognition platform was obtained by the self-assembly of 4-mercaptobenzoic acid onto a gold surface, covalent attachment of streptavidin and further immobilization of the biotinylated anti-thrombin aptamer. The biosensing platform was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, surface plasmon resonance (SPR) and quartz crystal microbalance with dissipation monitoring. The biorecognition event aptamer-thrombin was detected from changes in the SPR angle produced as a consequence of the molecular interaction between the aptasensor and the target protein. The biosensing platform demonstrated to be highly selective for human thrombin even in the presence of large excess of bovine thrombin, bovine serum albumin, cytochrome C, lysozyme and myoglobin. The relationship between the changes in the SPR angle and thrombin concentration was linear up to 0.19 μmol L(-1) (R(2)=0.992) while the detection limit was of 12.0 nmol L(-1) (240 fmol in the sample). This new sensing approach represents an interesting and promising alternative for the SPR-based quantification of thrombin.

Electrochemical sensing of guanine, adenine and 8-hydroxy-2′-deoxyguanosine at glassy carbon modified with single-walled carbon nanotubes covalently functionalized with lysine

This work reports the synthesis and characterization of single-walled carbon nanotubes (SWCNT) covalently functionalized with L-lysine (Lys) and the analytical performance of glassy carbon electrodes (GCE) modified with a dispersion of SWCNT-Lys (GCE/SWCNT-Lys) for the highly sensitive quantification of guanine, adenine and 8-hydroxy-2′-deoxyguanosine. Detection limits of 75, 195 and 97 nM were obtained for guanine, adenine and 8-hydroxy-2′-deoxyguanosine, respectively by voltammetric adsorptive stripping with medium exchange. GCE/SWCNT-Lys was successfully used for the detection of adenine and guanine oxidation after adsorption of salmon sperm-double stranded DNA. A clear definition of 8-hydroxy-2′-deoxyguanosine oxidation signal is observed even in the presence of large excess of guanine, adenine or salmon sperm-double stranded DNA.

Peptide-based biomaterials. Linking L-tyrosine and poly L-tyrosine to graphene oxide nanoribbons

Peptide-based biomaterials are being studied actively in a variety of applications in materials science and biointerface engineering. Likewise, there has been ongoing exploration over the last few decades into the potential biological applications of carbon nanomaterials, motivated by their size, shape, structure and their unique physical and chemical properties. In recent years, the functionalization of carbon nanotubes and graphene has led to the preparation of bioactive carbon nanomaterials that are being used in biomedicine as structural elements and in gene therapy and biosensing. The present study proposes different strategies for the bonding of l-tyrosine and the homopolypeptide poly-l-tyrosine to graphene oxide nanoribbons (GONRs). The covalent attachment of l-tyrosine was undertaken by amidation of the α-amine group of tyrosine with the existing carboxylic groups in GONR and by means of esterification through phenol nucleophiles contained in their side chains. In both cases use was made of protective groups to address the functionalization with the desired reactive groups. The linking of GONRs to the PTyr was attempted according to two different strategies: either by ester bonding of commercial PTyr through its phenol side groups or by in situ ring-opening polymerization of an N-carboxyanhydride tyrosine derivative (NCA-Tyr) with Tyr-functionalized GONRs. These biofunctionalized nanomaterials were characterized by Raman and infrared spectroscopies, X-ray photoelectron spectroscopy, thermogravimetric analysis, transmission electron microscopy, fluorescence and electrochemical techniques. On the basis of their properties, prospects for the potential utilization of the prepared hybrid nanomaterials in different applications are also given.