Cooperative Self-Assembly of Nanoparticle-Encapsulating Hybrid Protein Cages

Area of Science:

• Biomaterials Science
• Nanotechnology
• Protein Engineering

Background:

• Protein cages (PCs) are biocompatible protein shells used for encapsulating various nanoparticle cargos.
• Existing methods offer limited control over nanoparticle density and PC formation.
• Developing hybrid materials with integrated protein biofunctionality and nanoparticle properties is a key challenge.

Purpose of the Study:

• To investigate a self-assembly system for forming protein cages that simultaneously encapsulate nanoparticles at high density.
• To create pomegranate-like protein-nanoparticle hybrid materials with tunable functionalities.
• To explore the potential of this platform for developing advanced hybrid materials with enhanced biofunctionality.

Main Methods:

• Utilized amphiphilic recombinant fusion proteins (elastin-like polypeptides, leucine zippers, fluorescent proteins) as building blocks.
• Employed temperature-triggered liquid-liquid phase separation in the presence of fluorescent polystyrene nanoparticles for PC assembly.
• Analyzed nanoparticle encapsulation density and PC size using kinetic studies to elucidate the formation pathway.

Main Results:

• Successfully formed pomegranate-like protein-nanoparticle hybrid materials with high nanoparticle density.
• Identified potential cooperative interactions between protein building blocks and nanoparticles, leading to coacervate intermediates.
• Demonstrated enhanced calcium-sensing capability in hybrid PCs incorporating a fluorescent calcium sensor protein and titanium oxide nanoparticles.

Conclusions:

• The developed self-assembly system enables the creation of core-shell hybrid protein cages with encapsulated nanoparticles.
• This platform offers a broadly applicable strategy for integrating protein biofunctionality with diverse nanoparticle properties.
• The resulting hybrid materials show promise for applications requiring enhanced sensing capabilities and advanced material properties.