Forum 10/07/2004

“Virus Empty Capsids for Drug Delivery”

Wendy Ochoa, Ph.D. –  Johnson Lab, The Scripps Research Institute, La Jolla, CA

Natural or engineered protein assemblies are capturing the interest of different fields in nanotechnology research. In this respect, viral particles deserve special attention given their relatively simple composition, their ability to self assemble, symmetrical surface display, and the robust and stable nature of their capsids.
Of these kind of versatile viruses Cowpea mosaic virus, CPMV, a nonenveloped, icosahedral plant virus serves as a prototype example.
Previous works describing the ability for site-directed mutagenesis, genetically and chemical modification of CPMV have been carried out using the nucleoprotein components that constitute almost 95% of the capsids naturally produced on a plant infection. However a new approach is being addressed in order to use CPMV hollow capsids shells as scaffolds for nanoscale materials using the interior surface for attachment of drug cargo, site-isolate catalysis and nucleation sites for metal deposition or crystal growth.
In an attempt to get a reasonable amount of CPMV empty capsids RNA genome was removed by exposing middle and bottom components to alkaline conditions assuming a phosphate hydrolysis with a subsequent RNA degradation.
Cryo electron-microscopy analysis has been carry out in order to compare the 3D structures of the CPMV natural components and the artificial empty capsids. A description and direct 3D structural comparisons of the capsids suggest that the filled and the natural empty capsids are structurally similar. Density maps of the artificial empty capsids show structures markedly similar as well.

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