Direct electrochemistry and electrocatalysis of cytochrome P450s immobilized on gold/graphene-based nanocomposites

In the present work, gold nanoparticles coated chitosan/reduced graphene oxide (Au-CS-RG) was prepared for cytochrome P450 2D6 (CYP2D6) and cytochrome P450 1A1 (CYP1A1) immobilization, investigation of the direct electrochemistry and electrochemically-driven drug metabolism. The immobilized CYP2D6 and CYP1A1 displayed respectively a pair of redox peaks with a formal potential of −   492   ±   4 and −   504   ±   6   mV. The response showed a surface-controlled electrode process with an average electron transfer rate constant of 5.19   ±   0.3   s −   1 for CYP2D6 and 3.24   ±   0.4   s −   1 for CYP1A1 determined in the scan rate of 100   mV/s. When the Au-CS-RG was treated with polyacrylic acid (PAA), the resulting nanocomposites (PAA-Au-CS-RG) changed the surface charge of Au-CS-RG from positive to negative and increased the size of the coated gold nanoparticles from ~   15 to ~   25   nm. This led to negative-shift of the formal potential to −   513   ±   6   mV for CYP2D6 and −   509   ±   5   mV for CYP1A1, while the electron transfer rate constant decreased to 4.10   ±   0.3   s −   1 for CYP2D6 and 2.78   ±   0.2   s −   1 for CYP1A1, respectively. The immobilized CYP2D6 and CYP1A1 in both cases showed excellent electrochemically-driven drug metabolism. The LC-MS analysis demonstrated the bioconversion from tramadol or benzo[ a ]pyrene to o -demethyl-tramadol or 7.8-diol benzo[ a ]pyrene by the electrochemically-driven way, respectively. The metabolic inhibition of the quinidine and alpha-naphthoflavone to the enzymatic activity of CYP2D6 and CYP1A1 were also evaluated.