New electrochemical (bio)sensing strategies based on the use of dispersed carbon nanotubes

GUSTAVO A. RIVAS; NANCY F. FERREYRA; MARCELA CECILIA RODRÍGUEZ; MARÍA D. RUBIANES; MARÍA L. PEDANO; GUILLERMINA L. LUQUE; FABIANA A. GUTIERREZ; PABLO R. DALMASSO; AURELIÉN GASSNIER; EMILIANO N. PRIMO; YAMILE JALIT; FAUSTO N. COMBA; MARÍA V. BRACAMONTE

Nuremberg

Congreso; 14th International Meeting on Chemical Sensors; 2012

International Society of Chemical Sensors

Multi-walled carbon nanotubes (MWCNT) dispersed in different polyelectrolytes were used to develop electrochemical (bio)sensors by drop-coating of glassy carbon electrodes (GCE). MWCNT dispersed in polyhistidine were used as platform to build glucose biosensors by self-assembling of glucose oxidase (GOx). The strong interaction of dsDNA with the walls of bamboo-MWCNT allowed us to obtain stable dispersions for sensing promethazine and dopamine. The usefulness of an enzyme to disperse MWCNTS was also demonstrated, GOx not only dispersed MWCNT in a very efficient way, but also gave to them excellent biorecognition properties. MWCNTs dispersed in polyethylenimine allowed the development of stable and robust electrochemical sensors for phenols without passivation of the surface, dopamine in complex mixtures, and dsDNA through the complex formation. Carbon nanotubes (CNTs) have been largely used for electrochemical (bio)sensing due to their outstanding properties [1-3]. However, despite these unique properties, CNTs tend to aggregate in aqueous solutions due to strong -interactions between their aromatic rings, making difficult their dispersion. Here, we discuss the advantages of electrochemical (bio)sensors obtained by modification of glassy carbon electrodes (GCE) with multiwalled carbon nanotubes (MWCNT) dispersed in polyhistidine (Polyhis), glucose oxidase (GOx), calf-thymus double stranded DNA (dsDNA) and polyethylenimine (PEI) (Fig. 1 shows an scheme of the modified electrode, a microscopic image of the surface and the transduction signal). The dispersions were obtained by mixing the MWCNT with the given polymer (prepared in 50% ethanol solution), followed by sonication for a given time. In all cases, the ratio between the amount of dispersing agent and MWCNT demonstrated to be a critical aspect. The sensors were obtained by drop-coating of polished GCE and further evaporation of the solvent at room temperature. The GCE modified with Polyhis was used as platform for building supramolecular multistructures by self-assembling of GOx on MWCNT-Polyhis dispersion, without oxidation of CNTs or covalent attachment of functional groups The sensor was used for the highly sensitive and selective glucose quantification. Fig. 2 shows the amperometric recording obtained using an architecture integrated by five bilayers MWCNT-Polyhis/GOx and one anti-interferents layer of Nafion, as well as the corresponding calibration plot. We also report for the first time the use of an enzyme to disperse MWCNT. In this case GOx not only dispersed MWCNT in a very efficient way, but also gave to the MWCNT, excellent biorecognition properties even after the sonication in the ethanolic medium. The effectiveness of the dispersion of bamboo type MWCNT in dsDNA was promoted by the interaction between the DNA bases and the walls of CNT and partial excision of the strands due the sonication in ethanol. The GCE modified with this dispersion demonstrated to have excellent properties for the detection of the neurotransmitter dopamine (Do). GCE modified with MWCNTs dispersed in PEI (Fig. 3) is another interesting strategy since the electrocatalytic activity of CNT largely decreases the overvoltage for the oxidation of ascorbic acid, allowing the simultaneous quantification of Do in the presence of ascorbic acid and serotonin (Fig. 4), as well as the quantification of phenols without passivation of the surface, and dsDNA due to the formation of the complex on the surface of the electrode. In summary, the analytical performance of the biosensors obtained by modification with CNT dispersions would be the result of the combination of the efficiency in the dispersion of MWCNTs and the properties (charge, biorecognition) of the dispersing agent.