Using polymer conformation to control architecture in semiconducting polymer/viral capsid assemblies.

Area of Science:

• Biophysics
• Materials Science
• Nanotechnology

Background:

• Cowpea chlorotic mottle virus (CCMV) capsid proteins can self-assemble into virus-like particles (VLPs).
• These VLPs can encapsulate various polyanions, including nucleic acids and synthetic polymers.
• CCMV VLPs can form diverse structures (spheres, rods) dependent on environmental conditions like pH and ionic strength.

Purpose of the Study:

• To create optically active virus-like particles by encapsulating a fluorescent semiconducting polymer (MPS-PPV) within CCMV capsid proteins.
• To investigate how the encapsulation process and resulting VLP structure affect the optical properties of the polymer.
• To explore the potential of hybrid synthetic/biological systems for developing materials with tailored functionalities.

Main Methods:

• Purification and reassembly of CCMV capsid proteins.
• Encapsulation of the fluorescent polymer MPS-PPV within self-assembled VLPs.
• Characterization using Transmission Electron Microscopy (TEM), fluorescence anisotropy, and sucrose gradient separation.
• Analysis of polymer fluorescence spectra to determine conformation and location within VLPs.

Main Results:

• Encapsulation of MPS-PPV resulted in optically active VLPs with distinct fluorescence peaks.
• TEM and other analyses revealed two main VLP structures: spheres and rods.
• The blue fluorescence peak correlated with MPS-PPV in spherical particles, while the redder peak corresponded to polymers in rod-like particles.
• Ionic strength during assembly was identified as a key factor in controlling the ratio of spheres to rods.

Conclusions:

• The conformation of the encapsulated polymer influences the structure of the hybrid VLP.
• The structure of the hybrid VLP, in turn, modifies the optical properties of the polymer.
• This study demonstrates the synergistic interaction between biological scaffolds and synthetic materials, paving the way for novel functional hybrid materials.