14 Single- and multi-​walled carbon nanotubes from different sources were characterized in detail, and the characteristics obtained were carefully analyzed. The carbon material with the highest capacitance, and also other superior properties ("Taunit-​M" from "NanoTechCenter", Russia)​, was chosen for further modification and fabrication of buckypaper based electrodes. These electrodes were biomodified with plant and fungal laccases, as well as fungal bilirubin oxidase. The designed biocathodes were studied in simple buffers and also in a complex physiol. fluid (human serum)​. Biocathodes based on immobilized fungal laccase were bioelectrocatalytically inactive in chloride contg. media at neutral pH. In spite of the quite high current densities realized using biodevices based on plant laccase and fungal bilirubin oxidase, the limited thermal stability of the enzymes renders the biocathodes inadequate for practical applications in implanted situations.