Using Polymer Conformation to Control Architecture in Semiconducting Polymer/Viral Capsid Assemblies

Abstract

Cowpea Chlorotic Mottle Virus is a single-stranded RNA plant virus with a diameter of 28 nm. The proteins comprising the capsid of this virus can be purified and reassembled either by themselves to form hollow structures, or with polyanions like double-stranded DNA or single-stranded RNA. Depending on pH and ionic strength, a diverse range of structures and shapes can form. The work presented here focuses on using these proteins to encapsulate a fluorescent polyanionic semiconducting polymer, MPS-PPV (poly-2-methoxy-5-propyloxy sulfonate phenylene vinlyene), in order to obtain optically active virus-like particles. After encapsulation, fluorescence from MPS-PPV shows two distinct peaks, which suggests the polymer may be in two conformations. A combination of TEM, fluorescence anisotropy, and sucrose gradient separation indicate that the blue peak arises from polymer encapsulated into spherical particles, while the redder peak corresponds to polymers contained in rod-like cages. Ionic strength during assembly can be used to tune the propensity to form rods or spheres. The results illustrate the synergy of hybrid synthetic/biological system – polymer conformation drives the structure of this composite material, which in turn modifies the polymer optical properties. This synergy could be useful for the future development of synthetic/biological hybrid materials with designated functionality.

Cross-Linked Fluorescent Supramolecular Nanoparticles as Finite Tattoo Pigments with Controllable Intradermal Retention Times

“…Bare MPS-PPV chains coiled and formed face-to-face π -stacking among phenyl rings. 28 Therefore, the fluorescence is highly quenched. Once CD-PEI is introduced in the FSNPs, they form a complex with MPS-PPV polymer chains electrostatically, separating and uncoiling individual polymer chains.…”

Natural supramolecular building blocks: from virus coat proteins to viral nanoparticles

“…At a low ionic strength, the semi-rigid rod MPS-PPV exhibited a more extended conformation and the VCPs encapsulated the stretched polymer forming a rod-like structure. 79 Brasch and Cornelissen also showed that longer conjugated MPS-PPV chains could not be accommodated into a single VLP. As a result, a cluster of more than two T = 1 VLPs was formed.…”

“…For example, optically active semiconducting polymer poly-2-methoxy-5-propyloxy sulfonate phenylene vinylene (MPS-PPV) was encapsulated in order to obtain optically active VLPs. 79 This self-assembly route was particularly interesting because two distinct, optically active structures could be created depending on the ionic strength ( Fig. 4b and c).…”

Polymer Directed Protein Assemblies

“…By controlling the polymer conformation using different ionic strengths, going from low to high ionic strength, the morphology changed from rod-like to mixed rod-like/globular to finally completely globular. Additionally, the fluorescent properties also changed with the polymer conformation obtaining not only different overall particle morphologies, but also with different optical and electronic properties [39]. Future research will produce more of these biohybrid materials since new morphologies with new applications will emerge and the strength of combining electrostatic interactions with synthetic and biological structures is a straightforward and easy way of fabrication and allows also for large-scale fabrication under mild aqueous conditions.…”