Credit: © 2006 ACS

Labelling a virus particle with a fluorescent quantum dot (QD) may allow for the continuous tracking of a viral infection. However, the point of attachment of such a probe must be selected carefully, otherwise the normal course of infection may be altered. Researchers in the USA have tackled this problem by thinking inside-the-box and have incorporated QDs inside a viral capsid — the protein shell that encloses the genetic payload of a virus.

Bogdan Dragnea and colleagues1 from Indiana University, Texas A&M University and the University of Massachusetts at Amherst investigated the formation of brome mosaic virus (BMV) capsids around CdSe/ZnS nanocrystals. QDs coated with poly(ethylene glycol) were shown to be the most stable to prolonged light irradiation, and were also the best at promoting assembly of the viral cage around them. As the ratio of QDs to virus components increases, not only are fewer empty capsids observed, but many of them encapsulate multiple QDs. Image reconstructions from transmission electron microscopy studies showed that the capsid structure of the QD–virus particle hybrids is the same as that found in one naturally occurring form of the BMV virus.

Earlier work from Dragnea's laboratory had shown how gold nanoparticles could be encapsulated inside virus particles and the current study confirms that this strategy is a general one. The promise of incorporating designer nanocrystals into biologically based carriers may offer significant opportunities for biosensing applications.