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Use of the interior cavity of the P22 capsid for site-specific initiation of atom-transfer radical polymerization with high-density cargo loading

Nature Chemistry volume 4, pages 781–788 (2012)Cite this article

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Abstract

Virus-like particles (VLPs) have emerged as important and versatile architectures for chemical manipulation in the development of functional hybrid nanostructures. Here we demonstrate a successful site-selective initiation of atom-transfer radical polymerization reactions to form an addressable polymer constrained within the interior cavity of a VLP. Potentially, this protein–polymer hybrid of P22 and cross-linked poly(2-aminoethyl methacrylate) could be useful as a new high-density delivery vehicle for the encapsulation and delivery of small-molecule cargos. In particular, the encapsulated polymer can act as a scaffold for the attachment of small functional molecules, such as fluorescein dye or the magnetic resonance imaging (MRI) contrast agent Gd-diethylenetriaminepentacetate, through reactions with its pendant primary amine groups. Using this approach, a significant increase in the labelling density of the VLP, compared to that of previous modifications of VLPs, can be achieved. These results highlight the use of multimeric protein–polymer conjugates for their potential utility in the development of VLP-based MRI contrast agents with the possibility of loading other cargos.

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Figure 1: Schematic of the internally initiated ATRP polymerization within the P22 VLP.
Figure 2: Structural model of the expanded morphology of the P22 capsid that shows the location of the S39C mutation.
Figure 3: Characterization of the P22S39C mutant to verify morphological transformation.
Figure 4: Size and morphological characterization of the P22S39C-xAEMA composite and P22S39C-int.
Figure 5: Molecular weight increase as a result of polymerization, monitored by MALS.
Figure 6: Polymer formation and covalent modification with FITC was verified by native agarose gel electrophoresis.
Figure 7: Analysis of sample population homogeneity by analytical ultracentrifugation.

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Acknowledgements

This research was supported in part by grants from the National Institutes of Health (R01-EB012027), the National Science Foundation (CBET-0709358) and a National Science Foundation Graduate Research Fellowship (J.L.). P.E.P. and G.J.B. were supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering (DE-FG02-08ER46537).

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Authors and Affiliations

  1. Chemistry and Biochemistry Department, Montana State University, Bozeman, 59717, Montana, USA

    Janice Lucon, Shefah Qazi, Masaki Uchida, Ben LaFrance & Trevor Douglas

  2. Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, 59717, Montana, USA

    Janice Lucon, Shefah Qazi, Masaki Uchida, Ben LaFrance & Trevor Douglas

  3. Department of Microbiology, University of Alabama at Birmingham, Birmingham, 35294, Alabama, USA

    Gregory J. Bedwell & Peter E. Prevelige Jr

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  1. Janice Lucon
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Contributions

J.L. designed and carried out the experiments. S.Q. characterized the samples by NMR and analysed the relaxivity data. M.U. and B.L.F. assisted in the initial characterization of the S39C mutant. G.J.B. characterized the samples by analytical ultracentrifugation. M.U. and T.D. assisted in the experimental design. J.L. and T.D. co-wrote the manuscript. P.E.P. and T.D. coordinated the project. All authors discussed the results.

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Correspondence to Trevor Douglas.

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Lucon, J., Qazi, S., Uchida, M. et al. Use of the interior cavity of the P22 capsid for site-specific initiation of atom-transfer radical polymerization with high-density cargo loading. Nature Chem 4, 781–788 (2012). https://doi.org/10.1038/nchem.1442

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