Redox phospholipid polymer microparticles as doubly functional polymer support for immobilization of enzyme oxidase

We prepared redox phospholipid polymer microparticles for immobilizing an enzyme in order to maintain activity for a long time and obtain highly effective electron transfer to a gold substrate as an electrode. To achieve these double functions, an amphiphilic redox phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate-co-p-nitrophenyloxycarbonyl oligo(ethylene glycol) methacrylate (MEONP)-co-vinylferrocene (VFc)) (PMBNF) was synthesized. The polystyrene (PS) microparticles were modified by employing a simple solution dip-coating technique to form the PMBNF layer on the surface. As one of the model enzyme oxidases, a glucose oxidase (GOx) was immobilized on the PMBNF/PS microparticles by the reaction between the MEONP units in the PMBNF layer and the amino group in the GOx. The activity of immobilized GOx is maintained well; for example, activity of more than 80% of the initial activity was observed even after storage at both 4 °C and 25 °C (ionic strength: 0.10 mol/L, phosphate buffer solution, pH 7.0) for at least one month. The GOx/PMBNF/PS microparticles were arrayed on a gold substrate in a monolayer, and then, crosslinked to each other with a polymeric diamine compound. The PMBNF/PS microparticles demonstrated an efficient electron transfer from immobilized GOx to the gold surface. From these results, we concluded that the PMBNF layer on the PS microparticles possessed double functions such as stable enzyme immobilization ability and efficient electron transfer ability.