In the last four years, the proposed hierarchical carbon nanotubes (hCNT) composite material [1] grown onto ordinary graphite rod electrode demonstrated remarkable properties for supporting extensive loading with biological components and still facilitating excellent properties for efficient direct electron transfer (DET). In addition, this material shows high conductivity within the entire CNT network, as well as free access for the enzyme substrate towards the site with catalytic activity. In fact, the bioelectrochemical investigations of several redox enzymes was suggesting that the current density is dependent on the actual penetration length (or life span) of the substrate within CNT network.

Apart from the recently published example of HRP/hCNT biocathode [2], several other examples of enzymatic biocathodes constructed based on this hCNT material were investigated, such as: i) the co-immobilization of HRP/GOx for providing the first biocathode operating at +600 mV vs Ag/AgCl and relying on components compatible with physiological conditions and on in-vivo available substrates (glucose and oxygen); ii) the promoted adsorption of laccase using specific pyrene derivatives (see Figure 1); or iii) covalent linkage of bilirubin oxidase via its crosslinking with glutaraldehyde to the activated surface of the electrode.

Figure 1. Cyclic voltammograme showing bioelectrocatalytic currents recorded at hCNT modified with a pyrene derivative and laccase. Insert- SEM image of hCNT composite material grown onto graphite rod.

The above examples and potential perspectives for further exploitation of this material will be presented.

[1]   [1] Wenzhi Jia, Stefanie Schwamborn, Chen Jin, Wei Xia, Martin Muhler, Wolfgang Schuhmann and Leonard Stoica, Phys. Chem. Chem. Phys. (2010), 12(34)

[2] Nan Li, Xingxing Chen, Leonard Stoica, Wei Xia, Jun Qian, Jens Aßmann, Wolfgang Schuhmann, Martin Muhler, Advanced Materials (2007) 19 (19) 2957

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