Plant Virus Particles Adapted to Carry Anticancer Drugs

Resembling microscopic balloons, empty Cowpea mosaic virus (CPMV) particles can be modified to entrap drugs or other molecules while the outside surface can be coated with peptides that direct the particles to a specific class of target cells.

CPMV is a plant virus of the Comovirus group. Its genome consists of two molecules of positive-sense RNA, which are separately encapsulated. The virus particles are 28 nm in diameter and contain 60 copies each of a Large (L) and Small (S) coat protein. The structure is well characterized to atomic resolution, and the viral particles are thermostable. CPMV displays a number of features that can be exploited for nanoscale biomaterial fabrication. Its genetic, biological, and physical properties are well characterized, and it can be isolated readily from plants. There are many stable mutants already prepared that allow specific modification of the capsid surface. It is possible to attach a number of different chemicals to the virus surface and to construct multilayer arrays of such nanoparticles on solid surfaces. This gives the natural or genetically engineered nanoparticles a range of properties, which could be useful in nano-technological applications such as biosensors, catalysis and nanoelectronic devices.

Investigators at the John Innes Center (Norwich, United Kingdom) have established a facility for the production of empty (RNA removed) CPMV particles and are in the process of obtaining a patent for their use. In a study published in the March 8, 2010, online edition of the journal Small, they described a model system where CPMV particles were loaded with cobalt or iron oxide. The positive results obtained suggest that the metal molecules could be replaced with specific anticancer drugs.

"The potential for developing Cowpea mosaic virus as a targeted delivery agent of therapeutics is now a reality,” said senior author Dr. David Evans, professor of biological chemistry at the Johns Innes Centre. "But now we can load them too, creating fancy chemical containers.”

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