A feasible and fast method for glucose oxidase (GOx) study was developed by covalent attachment of GOx to gold-coated magnetic iron oxide nanoparticles (Fe@Au).GOx molecules were oxidized with metaperiodate to form aldehyde group. The prepared Fe@Au composite nanoparticles with 60 nm diameter were used as a carrier for the immobilization of GOx. Fe@Au nanoparticles were modified by cysteamine to produce amine groups at the surface. The GOx was covalently attached to the amine-modified Fe@Au nanoparticles through its aldehyde groups. The direct electrochemistry of GOx showed a quasi-reversible cyclic voltammogram corresponding to the flavin adenine dinucleotide (FAD/FADH2) redox couple with a formal potential of–270 mV in 0.1 M phosphate buffer. The apparent charge transfer rate constant (ks) and transfer coefficient for electron transfer between the electrode surface and enzyme were calculated as 2.23 s–1 and 0.45, respectively. The linear concentration range of the biosensor is 2.4–54 mM with detection limit of 0.51 mM at S/N = 3. The apparent Michaelis-Menten constant was measured to be 8.59 mM, indicating that the immobilized GOx on Fe@Au preserved its native activity. The life time of biosensor is more than 2 weeks.
- direct electrochemistry
- glucose oxidase
- gold-coated iron oxide nanoparticles
ASJC Scopus subject areas
- Analytical Chemistry