Physicochemical Study of Viral Nanoparticles at the Air/Water Interface

Abstract

The assembly of most single-stranded RNA (ssRNA) viruses into icosahedral nucleocapsids is a spontaneous process driven by protein-protein and RNA-protein interactions. The precise nature of these interactions results in the assembly of extremely monodisperse and structurally indistinguishable nucleocapsids. In this work, by using a ssRNA plant virus (cowpea chlorotic mottle virus [CCMV]) as a charged nanoparticle we show that the diffusion of these nanoparticles from the bulk solution to the air/water interface is an irreversible adsorption process. By using the Langmuir technique, we measured the diffusion and adsorption of viral nucleocapsids at the air/water interface at different pH conditions. The pH changes, and therefore in the net surface charge of the virions, have a great influence in the diffusion rate from the bulk solution to the air/water interface. Moreover, assembly of mesoscopic and microscopic viral aggregates at this interface depends on the net surface charge of the virions and the surface pressure. By using Brewster's angle microscopy we characterized these structures at the interface. Most common structures observed were clusters of virions and soap-frothlike micron-size structures. Furthermore, the CCMV films were compressed to form monolayers and multilayers from moderate to high surface pressures, respectively. After transferring the films from the air/water interface onto mica by using the Langmuir-Blodgett technique, their morphology was characterized by atomic force microscopy. These viral monolayers showed closed-packing nano- and microscopic arrangements.

Soft matter science and the COVID-19 pandemic

“…Importantly, this process still occurs in unilamellar vesicles that include membrane proteins. 113 The possibility that an enveloped virus may similarly disrupt spontaneously on contact with an air-water interface is intriguing and deserves further investigation, e.g., by studying virions in a Langmuir trough, which has been done for a nonenveloped virus 114 but not, as far as we know, for enveloped viruses. In this context, as well as more generally, we should also mention that nanoparticles covered by unilamellar lipid bilayers 115 may be useful model systems for aspects of the biophysics of enveloped viruses.…”

Plant molecular farming of virus‐like nanoparticles as vaccines and reagents

“…By the 1990s, in vitro assembly of CP expressed in Escherichia coli and viral RNAs transcribed from cDNA had been shown (Zhao, Fox, Olson, Baker, & Young, 1995), as well as the apparent structural identity of artificial and natural virions (Fox et al, 1998). By the 2000s, yeast-made Gd 3+ -infused CCMV VNPs were being investigated as magnetic resonance contrast agents (Allen et al, 2005), and interest in both virions and VNPs has continued (Comellas-Aragones et al, 2011;Lavelle, Michel, & Gingery, 2007;Schoonen, Maas, Nolte, & van Hest, 2017;Suci, Klem, Arce, Douglas, & Young, 2006;Torres-Salgado et al, 2016). Interestingly, while it is assumed that the surface structure of CCMV and other generic bromovirus capsids is essentially identical to the native virions, a serological study in 1983 showed quantifiable antigenic differences by means of enzyme-linked immunosorbent assay between brome mosaic bromovirus virions and empty capsids (Rybicki & Coyne, 1983).…”

Relative humidity in droplet and airborne transmission of disease

“…Both high ionic strength and large surface hydrophobicity create a high affinity for virus adsorption to the AWI [157,199]. Torres et al [206] have measured the diffusion and adsorption of cowpea chlorotic mottle virus at different pH conditions, and found that the diffusion of the virus from the bulk solution to the AWI is an irreversible adsorption process that changes with pH (and therefore with the net surface charge of the virus [207,208]). Recent experimental and computational methods have shown that viruses differ among themselves with respect to their surface hydrophobicity [209,210], providing another possible clue into the different survival responses to RH in different viruses.…”