The influence of ligand charge and length on the assembly of Brome mosaic virus derived virus-like particles with magnetic core

Adam A Mieloch,Marek Figlerowicz,Jakub D Rybka,Bohdan Skalski,Monika Kręcisz,Michał Krupiński,Michael Giersig,Maciej Kozak,Anna Urbanowicz,Aleksander Strugała

doi:10.1063/1.5011138

Abstract

Virus-like particles (VLPs) have sparked a great interest in the field of nanobiotechnology and nanomedicine. The introduction of superparamagnetic nanoparticles (SPIONs) as a core, provides potential use of VLPs in the hyperthermia therapy, MRI contrast agents and magnetically-powered delivery agents. Magnetite NPs also provide a significant improvement in terms of VLPs stability. Moreover employing viral structural proteins as self-assembling units has opened a new paths for targeted therapy, drug delivery systems, vaccines design, and many more. In many cases, the self-assembly of a virus strongly depends on electrostatic interactions between positively charged groups of the capsid proteins and negatively charged nucleic acid. This phenomenon imposes the negative net charge as a key requirement for the core nanoparticle. In our experiments, Brome mosaic virus (BMV) capsid proteins isolated from infected plants Hordeum vulgare were used. Superparamagnetic iron oxide nanoparticles (Fe3O4) with 15 nm in diameter were synthesized by thermal decomposition and functionalized with COOH-PEG-PL polymer or dihexadecylphosphate (DHP) in order to provide water solubility and negative charge required for the assembly. Nanoparticles were characterized by Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), Zeta Potential, Fourier Transformed Infrared Spectroscopy (FTIR) and Superconducting Quantum Interference Device (SQUID) magnetometry. TEM and DLS study were conducted to verify VLPs creation. This study demonstrates that the increase of negative surface charge is not a sufficient factor determining successful assembly. Additional steric interactions provided by longer ligands are crucial for the assembly of BMV SPION VLPs and may enhance the colloidal stability.

Highlights

The definition of virus-like particles (VLPs) includes a plethora of biological structures related to viruses in terms of morphology, structure and self-assembly
SPIONs were synthesized via modified route of iron (III) acetylacetonate thermal decomposition in 1-octadecene with oleic acid as surfactant (NP OA).[20]
Blocking temperature obtained from zero field cooling and field cooling (ZFC-FC) measurement is 139 K (Figure 2a)

Summary

Introduction

The definition of virus-like particles (VLPs) includes a plethora of biological structures related to viruses in terms of morphology, structure and self-assembly. The most prominent characteristic of VLPs is their relative ease of creation through self-assembly of viral proteins. The capsid forms a T=3 lattice and consists of 180 identical proteins. The mechanism of self-assembly is mainly driven by electrostatic interactions between positively charged arginine-rich motifs (ARMs) of the coat protein and negatively charged phosphate groups of the RNA.[7,8] The BMV capsid remains stable in buffers with pH below 5.0 and moderate ionic strength. Decrease of the pH and ionic strength back to previous values initiates reassembly of the capsid.[9] This approach has been utilized in creation of BMV VLPs containing various cores e.g. gold nanoparticles, quantum dots, magnetite nanoparticles.[9,10,11]

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Conclusion