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Multilayer electrodes for highly enantioselective sugar conversion are obtained by using monoatomically high platinum islands as pattern for further electrode modification with pyranose-2-oxidase (P2Ox). We describe this kind of electrode for the glucose oxidation. The reaction is monitored via the H2O2 production by the enzyme as side product. As first layer, a self-assembled monolayer (SAM) is arranged on the Au(111) surface via dip coating in a solution of 4-mercaptopyridine. On top of the SAM, a controlled distribution of platinum islands is obtained by a combination of electroless and electrochemical deposition using a solution of K2PtCl4. The platinum islands have a diameter of about 6 nm. Thereon, poly(allylamine hydrochloride) (PAA) obtained by dip coating provides a linker for immobilization of the enzyme pyranose-2-oxidase. Our assumption is that only one enzyme molecule is bound to one platinum island. This well ordered surface structure is probably the reason for the very high conversion efficiency.

A supplemental cysteine-tag modification of the enzyme galactitol dehydrogenase (GatDH), expressed in Escherichia coli has enabled a directed and covalent immobilisation of the protein on gold surfaces without secondary linkers. The successful enzyme immobilisation was verified by SPR measurements, and the activity of the immobilized GatDH was demonstrated by cyclic voltammetry (CV) while NAD+ and the redox mediator 4-carboxy-2,5,7-trinitrofluorenyliden-malonnitrile (CTFM) were both kept in solution. The results represent a proof of concept for the development of electrochemical reactors for the generation of enantiopure fine chemicals as building blocks for pharmaceutical products.