Incorporation of CdSe/ZnS semiconductor quantum dots (QDs) into viral particles provides a new paradigm for the design of intracellular microscopic probes and vectors. Several strategies for the incorporation of QDs into viral capsids were explored; those functionalized with poly(ethylene glycol) (PEG) can be self-assembled into viral particles with minimal release of photoreaction products and enhanced stability against prolonged irradiation.

Alphaviruses are animal viruses holding great promise for biomedical applications as drug delivery vectors, functional imaging probes, and nanoparticle delivery vesicles because of their efficient in vitro self-assembly properties. However, due to their complex structure, with a protein capsid encapsulating the genome and an outer membrane composed of lipids and glycoproteins, the in-vitro self-assembly of viruslike particles, which have the functional virus coat but carry an artificial cargo, can be challenging. Fabrication of such alphavirus-like particles is likely to require a two-step process: first, the assembly of a capsid structure around an artificial core, second the addition of the membrane layer. Here we report progress made on the first step: the efficient self-assembly of the alphavirus capsid around a functionalized nanoparticle core.

Viral nanoparticles used for biomedical applications must be able to discriminate between tumor or virus-infected host cells and healthy host cells. In addition, viral nanoparticles must have the flexibility to incorporate a wide range of cargo, from inorganic metals to mRNAs to small molecules. Alphaviruses are a family of enveloped viruses for which some species are intrinsically capable of systemic tumor targeting. Alphavirus virus-like particles, or viral nanoparticles, can be generated from in vitro self-assembled core-like particles using nonviral nucleic acid. In this work, we expand on the types of cargo that can be incorporated into alphavirus core-like particles and the molecular requirements for packaging this cargo. We demonstrate that different core-like particle templates can be further enveloped to form viral nanoparticles that are capable of cell entry. We propose that alphaviruses can be selectively modified to create viral nanoparticles for biomedical applications and basic research.

Size polydispersity of immature human immunodeficiency virus type 1 particles represents a challenge for traditional methods of biological ultra-structural analysis. An in vitro model for immature HIV-1 particles constructed from recombinant Gag proteins lacking residues 16–99 and the p6 domain assembled around spherical nanoparticles functionalized with DNA. This template-directed assembly approach led to a significant reduction in size polydispersity and revealed previously unknown structural features of immature-like HIV-1 particles. Electron microscopy and image reconstruction of these particles suggest that the Gag shell formed from different protein regions which are connected by a “scar” – an extended defect connecting the edges of two continuous, regularly packed protein layers. Thus, instead of a holey protein array, the experimental model presented here appears to consist of a continuous array of ~5000 proteins enveloping the core, in which regular regions are separated by extended areas of disorder.