Fabrication of a Novel Phenolic Compound Biosensor Using Laccase Enzyme and Metal-organic Coordination Polymers

Hydroquinone (HQ) sensitive electrochemical biosensing was performed using new nanocomposites of carboxylated graphene (GrCOOH) embedded in metal-organic coordination polymers (MOCPs) as efficient matrices for laccase (Lac) immobilization. GrCOOH nanosheets were used to pre-adsorb of HAuCl4 and act as anchor sites; they help to form MOCPs and more coordinate between gold ions and 4-aminothiophenol (4-ATP) ligand. According to the Tafel plot the mechanism was diffusion for HQ redox reactions on the proposed modified electrode surface and an electron process was in the rate-determining stage. It was concluded that this redox reaction was involved the same number of protons and electrons. The construction of GrCOOH-MOCPs one-pot entrapped Lac exhibited enhanced redox currents over MOCPs for HQ electrochemical oxidation and reduction and enhanced sensitivity and low detection limit (1.70 µM), being superior to other Lac biosensors. Furthermore, this biosensor was tested in real samples and demonstrated acceptable recoveries in real water samples and had good stability for one week.