Community Research and Development Information Service - CORDIS

Final Report Summary - NANOCAGE (The Development of Protein Cage-Based Inorganic Nano-Materials (resubmission))

The overall goal of this research is to advance techniques and methodologies for the development of hybrid nano-structured materials with an inorganic component and a second, protein cage-based, component. The two main objectives can be summarized as 1) Facilitating the generation of nanoparticles inside protein cages and 2) Facilitating the assembly of protein cages into large hierarchical structures. These materials have multiple potential applications in biomedical and nano-materials science.

Description of Work Performed and Results
With respect to Objective 1, advances have been made in the production of gold core/silver shell nanoparticles . In short, this procedure involves first the generation of a gold nanocluster inside the protein cage using a fast reductant. This cluster can then act as a seed for the mineralization of silver ions using a slow reductant. The idea is that this silver layer will grow until it hits the inner wall of the protein which will stop growth thus generating a population of particles of uniform size, all encapsulated by protein which helps with solubility, prevents aggregation of the particles, and can be used to attach handles to either assemble or direct the resulting hybrid materials.
Through the course of optimizing methodology for nanoparticle generation inside protein cages, protein stability can be a challenge. An understanding of the fundamentals that control cage assembly could be useful for out materials generation in the long term. Crystallisation conditions were screened and determined the x-ray crystal structure. This structure demonstrated that the added domains are flipped to the outside of the cage and these may be potentially useful for applications similar to those proposed in Objective 2.
Computational approaches were also pursued. Technology has also been advanced to screen protein libraries in living cells and used to repack key protein-protein interfaces so as to recover protein cage assembly in an assembly-crippled mutant.
The original design of protein cage lattices as described in Objective 2 and Fig. 4 and Fig. 5 of the proposal used the HIV protein, GP41 as a linker between the protein cages. Ferritin fusions have been cloned to the full length N and C GP41 peptides and also the eight truncated linkers, however, of these, only four were expressed soluble enough to be purified: C21, C14, N14, and N7. Further optimisation strategies are being pursued. The designs not only have strong hydrophobic interactions but also layers of hydrophilic interactions to keep the proteins soluble and ensure specificity of topology.

Expected Final Results and Potential Impact
The project has made successful progress this far. An aim is to capitalise on the medium throughput screening strategy and ability to screen protein libraries to find more stable protein cages and conditions that preserve protein cage stability. This information will help toward the rapid generation of protein-encapsulated nanoparticles.
The work also generates insight into protein-protein interactions (an “up-and-coming” class of pharmaceutical targets) and protein self-assembly (a ubiquitous biological process that spans multiple cellular functions). Furthermore, the protein cages provide a size-constrained reaction vessel to generate nanoparticles of unprecedentedly narrow polydispersities, water solubility, protection from aggregation and handles to direct or assemble the nanoparticles. Assembling them in to larger structures fundamentally is key because nature generates mixed organic/inorganic minerals with tunable and amazing properties by controlling various levels of hierarchical structure. Taking lessons from nature may generate materials with enhanced or unique characteristics.

Reported by

United Kingdom


Life Sciences
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