An approach to biomolecular electronics and bioengineering based on coenzymes chained to solid supports

Abstract

The possibility of attaching coenzymes to graphite surfaces through molecular wires in a manner such that an efficient electron transport chain is established between the bioactive molecule and the solid support has been considered. The covalent link used in these studies prevents the active molecules from diffusing away in the aqueous environment and improves their stablity and efficiency. This opens the way to employing the molecules gainfully in biomolecular electronics and bioengineering. Through the use of Molecular Orbital methods, the optimum designs for immobilisation of NAD, FAD and Cyt-c have been considered, with a view to achieving efficient electron transport. These coenzymes span the complete range of energy-transduction processes in living cells. Each of these molecules exists in two states, a reduced and an oxidised state, which can be monitored by simple spectroscopic methods. Based on the predictions of the Molecular Orbital approach, the coenzymes have been attached to graphite surfaces through polyacetylene chains. In two cases, FAD and Cyt-c, the immobilised coenzyme retained both its electrochemical and biological activity. In the case of NAD, the preparation of active surfaces with covalently attached coenzyme has so far failed. Potential applications of the chained coenzyme systems could arise in the field of biosensors, biobatteries, synthesis of value-added compounds and biomolecular electronics.