Structural Insights into Magnetic Clusters Grown Inside Virus Capsids

Abstract

Magnetic nanoparticles have multiple applications in materials science. In particular, virus capsids have been suggested as promising templates for building up nanometric-sized magnetic clusters by taking advantage of their inner cavity as a nanoreactor. In this study we investigate the magnetization of individual cobalt-filled cowpea mosaic virus empty virus-like particles using atomic force microscopy. We also combine the analysis of the effects of dehydration on the structure of virus particles with a comparison of their magnetic signal to that provided by commercially available magnetic nanoparticles of similar size. These two approaches allow the evaluation of the structure of the metallic cluster grown inside the virus capsid. We conclude that, rather than forming solid clusters, cobalt inside viruses forms a discontinuous structure that does not completely fill the virus cavity and reaches about 10% of its volume.

A virus-based nanoplasmonic structure as a surface-enhanced Raman biosensor

“…1B and C). These suggest some distortion of the NCs, but not total collapse of the protein capsids during immobilization and drying, consistent with recent observations noted for the VLP capsid in the absence of attached Au NPs (Jaafar et al 2014). The similarity in shape and size of the VLP-NCs and BC-NCs further indicates that the absence of RNA in the VLP capsids does not materially affect the formation and stability of the VLP-NCs, permitting use of the simpler fabrication protocols associated with VLP-NC assembly for future work.…”

“…Our calculations (Section 2.7) show that the electric field around an isolated Au NP is highest at the widest part of the NP, in agreement with previous computer simulations (Jaafar et al 2014). For example, a 3-fold field enhancement is predicted for a single 30 nm diameter Au NP (Fig.…”

“…The VLP capsid resembles the wild type (WT) CPMV (Lin et al 1999) but it lacks the genetic material (RNA) inside the capsid. We selected the VLP as an alternative scaffold based on its similarity to WT-CPMV (available reactive residues on the exterior capsid), its successful utilization in materials applications, (Jaafar et al 2014); (Aljabali et al 2010) and lack of nucleic acids that makes it an ideal platform for sensing DNA.…”

Magnetic Force Microscopy in Liquids

“…There are animals, such as the rainbow trout, where a magnetic sense is related to the presence of magnetic nanocrystals for magnetoreception . The encapsulation of magnetic particles in different biological entities is attracting many studies as well: magnetic bacteria to be used as magnetic markers for biosensing, or virus‐like cages, which are promising templates for building up nanometric‐sized magnetic clusters by taking advantage of their inner cavity as a nanoreactor . Nano‐magnetic catalysts are also focusing a lot of attention because they generally avoid loss of catalyst increasing their reusability …”

Quantum dot encapsulation in virus-like particles with tuneable structural properties and low toxicity

“…A number of studies have explored the formation of VLP/ inorganic nanoparticle assemblies via either assembly of the cage proteins around the inorganic cores, 7,10,11,[13][14][15][16] or in situ formation of inorganic nanoparticles within the assembled capsids. 12,17,18 In the former case, the guest molecules are entrapped within the cage during capsid assembly via complementary electrostatic interactions, whereas in the latter, the precursor molecules diffuse into the pre-formed cage to form nanocrystals. VLP self-assembly around inorganic 'guests' has been explored for gold nanoparticles, 7,19-22 magnetic cores, [23][24][25][26] and QDs 10,14,16,[27][28][29] among others, which have been discussed in recent reviews.…”