Facile Assembly of ZnO Nanoparticles Based on M13 Bacteriophage

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Facile Assembly of ZnO Nanoparticles Based on M13 Bacteriophage Chung Hee Moon1 and Elaine D. Haberer1,2 1 Materials Science and Engineering Program, University of California, Riverside, CA 92521, U.S.A. 2 Department of Electrical Engineering, University of California, Riverside, CA 92521, U.S.A. ABSTRACT A genetically modified M13 bacteriophage template was used to biomineralize ZnO. A peptide, EAHVMHKVAPRP [1], with a known affinity for ZnO was genetically displayed on each of five copies of the pIII protein located at one tip of the M13 virus. Site-directed assembly using this pIII peptide fusion was studied using a variety of precursor concentrations, incubation times, and phage concentrations. For comparision, free ZnO-binding peptides were also used to biomineralize ZnO. Isolated, polydisperse, spherical ZnO nanoparticles were formed at all mineralization conditions containing the ZnO-binding M13 bacteriophage, whereas free peptide mineralization resulted in smaller, more irregularly shaped particles which agglomerated at longer incubation times. These studies are preliminary experiments in the investigation of ZnO biomineralization on the various structural proteins of the M13 bacteriophage and cooperative effects which occur between neighboring peptides. INTRODUCTION ZnO is a direct, wide-bandgap (3.37eV) semiconductor which has proven useful for many electronic and optoelectronic applications in both bulk and nanocrystalline forms. It has been reported for applications in sensors, light emitting diodes, dye-sensitized solar cells, and photocatalytic devices [2, 3]. Bio-directed synthesis of ZnO is a promising technique capable of morphological control under generally mild, low temperature conditions. Several ZnO-binding peptides have been reported, and a few have been further investigated for biomineralization purposes [1, 4-6]. Such studies have either focused on free peptides or peptides arranged on a planar surface. Here we report the biomineralization of ZnO on a M13 bacteriophage template. A reported peptide sequence (EAHVMHKVAPRP) with a high affinity for ZnO was displayed on each of 5 copies of the pIII minor coat protein located at the proximal tip of the virus and used to form nanoparticles using a Zn(OH)2 precursor solution [1]. Cooperative effects among the highly localized ZnO-binding peptides modified nanoparticle size, shape, and the formation of hierarchical structures compared to free peptides under similar mineralization conditions. These studies are the first in a series of experiments aimed at exploring ZnO biomineralization on the various structural proteins of the M13 bacteriophage. EXPERIMENTAL DETAILS Zinc nitrate hexahydrate (Zn(NO3)2 Ÿ 6H2O) and potassium hydroxide (KOH) were purchased from Acros Organics (Fairlawn, NJ), and Fisher Scientific (Fairlawn, NJ),

respectively. Uranyl acetate and carbon-coated copper grids (200 mesh) were purchased from Ted Pella Inc. (Redding, CA). Oligonucleotide of ZnO-binding peptide with GGGSC linker was synthesized and purchased from Integrated D