M13 bacteriophage spheroids as scaffolds for directed synthesis of spiky gold nanostructures

Abstract

The spherical form (s-form) of a genetically-modified gold-binding M13 bacteriophage was investigated as a scaffold for gold synthesis. Repeated mixing of the phage with chloroform caused a 15-fold contraction from a nearly one micron long filament to an approximately 60 nm diameter spheroid. The geometry of the viral template and the helicity of its major coat protein were monitored throughout the transformation process using electron microscopy and circular dichroism spectroscopy, respectively. The transformed virus, which retained both its gold-binding and mineralization properties, was used to assemble gold colloid clusters and synthesize gold nanostructures. Spheroid-templated gold synthesis products differed in morphology from filament-templated ones. Spike-like structures protruded from the spherical template while isotropic particles developed on the filamentous template. Using inductively coupled plasma-mass spectroscopy (ICP-MS), gold ion adsorption was found to be comparatively high for the gold-binding M13 spheroid, and likely contributed to the dissimilar gold morphology. Template contraction was believed to modify the density, as well as the avidity of gold-binding peptides on the scaffold surface. The use of the s-form of the M13 bacteriophage significantly expands the templating capabilities of this viral platform and introduces the potential for further morphological control of a variety of inorganic material systems.

Gold-Decorated M13 I-Forms and S-Forms for Targeted Photothermal Lysis of Bacteria

“…An M13 bacteriophage with a gold-binding peptide, VSGSSPDS, displayed on each of approximately 2700 copies of the pVIII major coat protein found along the viral length was selected and studied as a scaffold for photothermal antibacterial agents. The gold-binding phage was transformed from its filamentous form to its spheroidal polymorph as previously described . Briefly, the phage was dispersed in 100 μL of tris-buffered saline (TBS, 50 mM Tris-HCl, 150 mM NaCl, pH 7.5) at a concentration of 10 8 pfu/μL and vortexed with an equal volume of chloroform (99.8%, ACROS Organics) for 5 vortex/rest (2 s/13 s) cycles at room temperature.…”

“…A segmented line function was used to measure the length and width of the templates. Structures with an aspect ratio between 3 and 25 with lengths between 80 and 300 nm were defined as i-forms, while geometries with aspect ratios <3 were denoted as spheroids …”

Structurally Modified Plant Viruses and Bacteriophages with Helical Structure. Properties and Applications

“…The work described above, as well as a number of publications on TMV SPs and demonstration of their biotechnological potential, arouse interest in SPs based on fi lamentous bacteriophages [1,2,10,58]. A group of scientists from the University of California has published a number of papers on the production and application of M13 SPs, with affi nity to gold [6,55,59]. The intermediate forms and the M13 SPs themselves were covered with gold, and in both cases ability of the particles to act as a photothermally-induced antibacterial agent was shown using the example of Escherichia coli cells.…”

Bioreduction of Gold Ions under Greener Conditions by the Thiol-Modified M13 Bacteriophage and with Hydroxylamine as the Autocatalytic Reducing Agent

“… 24 , 25 If such a procedure was followed, gold products should have a linear structure consisting of aggregated gold particles along the rod-like virus. 17 , 18 , 20 However, the gold products in these works were often presented as plate-like or spherical nanoscale particles. 24 , 25 It was proposed that the virus might attach to the surface of the particulate gold particles to stabilize them, whereas Wang’s group observed that discrete gold nanoparticles stood side-by-side with intact filamentous viruses.…”

“…Instead of the nonspecific electrostatic interactions of the ionic metal precursors with the virus surface, genetic manipulations of M13 have been explored to fuse the N-terminus of the p8 coat protein with the gold-affinity peptide fragments, which can promote highly efficient bioadsorption of gold ions onto the virus surface. 15 − 18 Laborious biopanning to screen gold-affinity mutants and constrained accessibility of the genetic techniques and so forth have limited the applications of such genetically engineered viruses. In contrast, chemical modification is a much versatile way to functionalize the M13 virus, thanks to the rich surface chemical groups of the solvent-exposed amino acid residuals of the p8 coat proteins.…”