Enzymatic surface-initiated polymerization: A novel approach for the in situ solid-phase synthesis of biocompatible polymer poly(3-hydroxybutyrate)

A novel system for surface-initiated enzymatic polymerization of a film of polyhydroxyalkanoate (PHA) on solid surfaces has been developed and characterized. PHAs are aliphatic polyesters produced by a variety of microorganisms as a reserve of carbon and energy, and their properties range from elastomers to thermoplastics, depending on their monomeric composition. The PHA synthase from Ralstonia eutropha H16 was expressed as a poly-histidine fusion in Escherichia coli and immobilized onto several solid substrates through a transition-metal complex, Ni2+-nitrilotriacetic acid. The immobilized PHA synthase catalyzed the surface-initiated polymerization of 3-(R)-hydroxybutyryl-CoA, forming a polymer film with a uniform thickness on the surface. In this work, we describe the patterned immobilization of the intact enzyme on silicon and subsequent enzymatic polymerization. The immobilized enzyme had a lower specific activity and did not exhibit a lac, phase as compared to the soluble enzyme.