Buckyballs Meet Viral Nanoparticles: Candidates for Biomedicine

Abstract

Fullerenes such as C₆₀ show promise as functional components in several emerging technologies. For biomedical applications, C₆₀ has been used in gene- and drug-delivery vectors, as imaging agents, and as photosensitizers in cancer therapy. A major drawback of C₆₀ for bioapplications is its insolubility in water. To overcome this limitation, we covalently attached C₆₀ derivatives to Cowpea mosaic virus and bacteriophage Qβ virus-like particles, which are examples of naturally occurring viral nanoparticle (VNP) structures that have been shown to be promising candidates for biomedicine. Two different labeling strategies were employed, giving rise to water-soluble, stable VNP−C₆₀ and VNP−PEG-C₆₀ conjugates. Samples were characterized using a combination of transmission electron microscopy, scanning transmission electron microscopy (STEM), gel electrophoresis, size-exclusion chromatography, dynamic light scattering, and Western blotting. “Click” chemistry bioconjugation using a poly(ethylene glycol) (PEG)-modified propargyl-O-PEG-C₆₀ derivative gave rise to high loadings of fullerene on the VNP surface, as indicated by the imaging of individual C₆₀ units using STEM. The cellular uptake of dye-labeled VNP−PEG-C₆₀ complexes in a human cancer cell line was found by confocal microscopy to be robust, showing that cell internalization was not inhibited by the attached C₆₀ units. These results open the door for the development of novel therapeutic devices with potential applications in photoactivated tumor therapy.