Bionanofabrication polyhydroxyalkanoates (PHAS) micro-/nano-structures on solid surfaces and its applications in nanobiotechnology

Abstract

Summary form only given. Bionanofabrication is a novel fabrication process that takes advantage of the specificity and catalytic efficiency of biological systems to create novel nanoscale structures. Polyhydroxyalkanoates (PHAs) are a family of aliphatic polyesters produced by a variety of microorganisms as a reserve of carbon and energy. PHAs can be combined from more than 100 different monomers to give materials with widely different physical properties. PHAs are biocompatible, biodegradable and demonstrate piezo electric and non-linear optical properties making them potential useful for tissue engineering, drug delivery, degradable packaging and smart materials. The enzymes involved in the synthesis of PHAs have been harnessed in our laboratory to produce novel polymers in vitro both in bulk and on solid surfaces. Site-specific attachment of the key catalytic enzyme, PHA synthase, on nanofabricated surfaces and subsequent addition of 3-(R)-hydroxybutyryl-CoA substrates (HB-CoA), allows us to create spatially ordered polyhydroxybutyrate (PHB) polymeric structures via in situ enzymatic surface-initiated polymerization (ESIP). By varying the reaction conditions we have optimized the PHB polymer growth at the interface and the resulting material characterized by fluorescence microscopy and atomic force microscopy. In the absence of additives such as bovine serum albumin, the PHB polymer synthesized on the surfaces formed very distinct and uniform granular structures on Au patterned surfaces. The average size of PHB granules was measured to be approximately 0.5 to 1 mum in diameter and 100 nm in height from the Au surfaces. In the presence of bovine serum albumin, the average size of PHB granules and PHB film thickness significantly increased to be approximately 1 to 5 mum in diameter and 500 nm to 1 mum in height, respectively, uniformly covering patterned surfaces. We believe that the use of this novel enzymatic approach offers many practical applications in different areas. For example, it can be employed to generate biocompatible PHAs coated solid surfaces for tissue engineering, promoting cell attachment and growth. As a result, one of our goals is to employ ESIP for in situ solid-phase synthesis of novel functionalized PHAs micro-/nano- structures with a wide range of mechanical, thermal, and biocompatible properties. In addition to biocompatible surface coatings, we envision that the novel polymeric micro-/nano-structures can be built in spaces that cannot be accessed by convention lithographic tools or other fabrication process. For example, PHB structures can be formed in situ inside microfluidic channels to produce rapid microfluidic mixing. Currently, we are investigating the use of in situ synthesized PHB polymer on specific Au patterned surfaces such as straight ridges and staggered herringbone patterns to act as passive micromixers inside microfluidic channels