A facile immobilization of polyphenol oxidase enzyme on graphene oxide and reduced graphene oxide thin films: An insight into in-vitro activity measurements and characterization

Abstract

Graphene oxide (GO) and reduced graphene oxide (rGO) Langmuir-Blodgett (LB) films with specific surface properties and functional groups were prepared as negative ideal substrates. Immobilization of the polyphenol oxidase (PPO) enzyme on these films was easily accomplished by electrostatic interaction without the need for any chemical bonding or surface modification. The PPO binding regions to GO and rGO surfaces were shown by an electrostatic surface potential map for pH: 5.0 value. The catalytic performances of the enzyme immobilized on GO and rGO substrates were found to be higher in GO-PPO LB films compared to RGO-PPO LB films in-vitro media. The reason why in-vitro enzyme activity is higher in GO-PPO LB films than in rGO-PPO LB films was also proved by SEM studies. The immobilization onto both the GO and rGO thin films as the GO-PPO and rGO-PPO complexes were further demonstrated by FT-IR measurement. This study revealed that the immobilized PPO enzyme on biodegradable GO is superior to the inorganic materials in terms of its use in biological systems. In addition, the fact that regular film structures with a single molecule thickness were prepared by LB film technique, contributed to the stability and recycling of immobilization of PPO enzyme on GO and rGO. In this respect, the in-vitro storage stability of immobilization on both film structures was determined to be one month at +4 °C.