Innovative Applications of Plant Viruses in Drug Targeting and Molecular Imaging- A Review

BACKGROUND

Nature had already engineered various types of nanoparticles (NPs), especially viruses, which can deliver their cargo to the host/targeted cells. The ability to selectively target specific cells offers a significant advantage over the conventional approach. Numerous organic NPs, including native protein cages, virus-like particles, polymeric saccharides, and liposomes, have been used for the preparation of nanoparticles. Such nanomaterials have demonstrated better performance as well as improved biocompatibility, devoid of side effects, and stable without any deterioration.

OBJECTIVE

This review discusses current clinical and scientific research on naturally occurring nanomaterials. It also illustrates and updates the tailor-made approaches for selective delivery and targeted medications that require a high-affinity interconnection to the targeted cells.

METHODS

A comprehensive search was performed using keywords for viral nanoparticles, viral particles for drug delivery, viral nanoparticles for molecular imaging, theranostics applications of viral nanoparticles and plant viruses in nanomedicine. We searched on Google Scholar, PubMed, Springer, Medline, and Elsevier from 2000 till date and by the bibliographic review of all identified articles.

RESULTS

The findings demonstrated that structures dependent on nanomaterials might have potential applications in diagnostics, cell marking, comparing agents (computed tomography and magnetic resonance imaging), and antimicrobial drugs, as well as drug delivery structures. However, measures should be taken in order to prevent or mitigate, in pharmaceutical or medical applications, the toxic impact or incompatibility of nanoparticle-based structures with biological systems.

CONCLUSION

The review provided an overview of the latest advances in nanotechnology, outlining the difficulties and the advantages of in vivo and in vitro structures that are focused on a specific subset of the natural nanomaterials.

Virus-Derived Nanoparticles

Capsid-based virus particles are widely engineered as viral nanoparticles and virus-like nanoparticles. The highly organized and uniform capsid structures make them ideal candidates for both in vitro and in vivo applications such as therapeutic delivery vehicles or enzymatic nanoreactors. Viruses have adapted to naturally infect a wide variety of organisms making their production achievable in various expression systems from bacterial to plants. Viral capsids can be modified externally and internally to suit the final application. The wide range of possible applications, ease of production in the system of choice, and customizable modification of viral capsids makes them an attractive choice in the field of nanotechnology. In this chapter we aim to provide a generic protocol for the purification and characterization of virus-derived nanoparticles and methodology for chemically labelling them to monitor their uptake in mammalian cells.

Infusion of imaging and therapeutic molecules into the plant virus-based carrier cowpea mosaic virus: cargo-loading and delivery

This work is focused on the development of a plant virus-based carrier system for cargo delivery, specifically 30nm-sized cowpea mosaic virus (CPMV). Whereas previous reports described the engineering of CPMV through genetic or chemical modification, we report a non-covalent infusion technique that facilitates efficient cargo loading. Infusion and retention of 130-155 fluorescent dye molecules per CPMV using DAPI (4',6-diamidino-2-phenylindole dihydrochloride), propidium iodide (3,8-diamino-5-[3-(diethylmethylammonio)propyl]-6-phenylphenanthridinium diiodide), and acridine orange (3,6-bis(dimethylamino)acridinium chloride), as well as 140 copies of therapeutic payload proflavine (PF, acridine-3,6-diamine hydrochloride), is reported. Loading is achieved through interaction of the cargo with the CPMV's encapsidated RNA molecules. The loading mechanism is specific; empty RNA-free eCPMV nanoparticles could not be loaded. Cargo-infused CPMV nanoparticles remain chemically active, and surface lysine residues were covalent modified with dyes leading to the development of dual-functional CPMV carrier systems. We demonstrate cargo-delivery to a panel of cancer cells (cervical, breast, and colon): CPMV nanoparticles enter cells via the surface marker vimentin, the nanoparticles target the endolysosome, where the carrier is degraded and the cargo is released allowing imaging and/or cell killing. In conclusion, we demonstrate cargo-infusion and delivery to cells; the methods discussed provide a useful means for functionalization of CPMV toward its application as drug and/or contrast agent delivery vehicle.

Biodistribution, pharmacokinetics, and blood compatibility of native and PEGylated tobacco mosaic virus nano-rods and -spheres in mice

Understanding the pharmacokinetics, blood compatibility, biodistribution and clearance properties of nanoparticles is of great importance to their translation to clinical application. In this paper we report the biodistribution and pharmacokinetic properties of tobacco mosaic virus (TMV) in the forms of 300×18nm(2) rods and 54nm-sized spheres. The availability of rods and spheres made of the same protein provides a unique scaffold to study the effect of nanoparticle shape on in vivo fate. For enhanced biocompatibility, we also considered a PEGylated formulation. Overall, the versions of nanoparticles exhibited comparable in vivo profiles; a few differences were noted: data indicate that rods circulate longer than spheres, illustrating the effect that shape plays on circulation. Also, PEGylation increased circulation times. We found that macrophages in the liver and spleen cleared the TMV rods and spheres from circulation. In the spleen, the viral nanoparticles trafficked through the marginal zone before eventually co-localizing in B-cell follicles. TMV rods and spheres were cleared from the liver and spleen within days with no apparent changes in histology, it was noted that spheres are more rapidly cleared from tissues compared to rods. Further, blood biocompatibility was supported, as none of the formulations induced clotting or hemolysis. This work lays the foundation for further application and tailoring of TMV for biomedical applications.