This communication presents the advantagesof electrochemical (bio)sensors obtained by modification of glassy carbonelectrodes (GCE) with multiwalled carbon nanotubes (MWCNTs) non-covalentlyfunctionalized with avidin (Av) and concanavalin A (ConA) as site-specificrecognition platforms for the immobilization of selected biomolecules thatallow the development of biosensors.  

The dispersions were obtained by sonicatingMWCNTs with the corresponding protein solution for a given time. The sensorswere prepared by dropping the MWCNTs-protein dispersion at GCE, followed by theevaporation of the solvent at room temperature. In all cases, the ratio betweenthe amount of dispersing agent/MWCNTs and the sonication time demonstrated tobe critical aspects. The different systems were studied using spectroscopic andelectrochemical techniques and scanning electron microscopy.

The sensing platforms were obtained bymodifying the GCE with I)MWCNTs dispersed in avidin (GCE/MWCNTs-Av) andII)MWCNTs dispersed in concanavalin A (GCE/MWCNTs-ConA). The analyticalusefulness of the novel platforms was evaluated by specific anchoring of thecorresponding enzymes at GCE/MWCNTs-protein. GCE/MWCNTs-Av was modified with biotinylatedhorseradish peroxidase (biot-HRP) to develop a hydrogen peroxide biosensor (GCE/MWCNTs-Av/biot-HRP)or biotinylated glucose oxidase with further electrodeposition of Runanoparticles to obtain a glucose biosensor (GCE/MWCNTs-Av/RuNPs/biot-GOx).GCE/MWCNTs-ConA was used to build monoenzymatic (GCE/MWCNTs-ConA/GOx) andbienzymatic (GCE/MWCNTs-ConA/HRP-GOx) glucose biosensors through thesite-specific anchoring of the glycoenzymes glucose oxidase and horseradishperoxidase. The sensors allowed the sensitive and selective detection ofhydrogen peroxide at nanomolar levels with real application for thequantification of hydrogen peroxide in mouthwash, serum and milk; and glucoseat submicromolar concentrations with practical applications for its quantificationin a pharmaceutical product, milk and blood human serum.

The results demonstrated once more that acritical selection of the functionalizing agent of carbon nanotubes (CNTs) is acrucial aspect when developing CNTs-based electrochemical (bio)sensors. Theproposed MWCNTs-proteins dispersion represents an interesting and innovative alternativefor building nanoarquitectures with high potential for the development ofdifferent biosensors just by changing the biotinylated biomolecule in the caseof GCE/MWCNTs-Av or the glycobiomolecule anchored at GCE/MWCNTs-ConA.