“…The ability to co-immobilize more than one biologically active component is desirable in some cases. Conducting polymers Singh et al, 2004a;Ruiz et al, 2004), carbon nanotubes (CNTs) (Guo et al, 2004;Yang et al, 2006b;Li et al, 2005), nanoparticles (NPs) Besombes et al, 1995Besombes et al, , 1997Kouassi et al, 2005), sol-gel/hydro-gels (Kumar et al, 2000;Qiaocui et al, 2005;Tan et al, 2005) and self-assembled monolayer (SAM) (Song et al, 2007;Shen and Liu, 2007;Chou and Liu, 2005) modified metals and carbon surfaces are commonly used to prepare solid electrode systems and supporting substrates. For electrochemical determination, electrodes such as platinum (Pt), gold (Au) and carbon-based materials such as graphite, carbon black and carbon fiber are preferred due to their excellent electrical and mechanical properties.…”