Scientists assemble a complete viral coat around a gold nanoparticle

May 9 2006

Using a short piece of DNA as a template, a team of investigators at North Carolina State University has assembled a complete viral coat around a gold nanoparticle.

The resulting virus-nanoparticle hybrid could serve as a multifunctional nanoscale device capable of targeting tumors, imaging them, and killing them with potent anticancer drugs.

Writing in the Journal of the American Chemical Society, a team headed by Stefan Franzen, Ph.D., describes how it developed a straightforward method for assembling a virus coat around gold nanoparticles ranging from 5 to 15 nanometers in diameter. The investigators took their cue from work by other researchers showing that the red clover necrotic mosaic virus (RCNMV) assembles itself onto a large RNA molecule that binds to a piece of the protein that forms the virus's coat.

The investigators began by attaching a small number of pieces of single-stranded DNA to the surface of gold nanoparticles as small as 5 nanometers and as large as 25 nanometers. This piece of DNA is complementary in sequence to one stretch of the virus's RNA, providing a place for that RNA to attach to the gold nanoparticle. They next added the coat protein, which spontaneously assembles into an icosahedron surrounding a single gold nanoparticle. The protein only self-assembles around gold particles that are 15 nanometers or smaller. The resulting hybrids are separated easily by centrifugation.

The investigators note that the viral coat protein provides a well-characterized surface onto which it will be possible to attach a wide variety of targeting, imaging, and therapeutic molecules. They add that although other research teams have developed alternative methods of adding such molecules to "naked" gold nanoparticles, none produce particles that are as uniform in size and composition as that obtained with the viral coat protein.

This work is detailed in a paper titled, "Controlled encapsidation of gold nanoparticles by a viral protein shell." An abstract of this paper is available through PubMed. View abstract.

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