Metamaterial optical elements self-assembled on protein scaffolds
Inventors
Ratna, Banahalli R. • Soto, Carissa M. • Rendell, Ronald W. • Fontana, Jake • Deschamps, Jeffrey R.
Assignees
Publication Number
US-9751913-B2
Publication Date
2017-09-05
Expiration Date
2032-01-12
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Abstract
A genetically modified cowpea mosaic virus (CPMV) protein capsid serves as a scaffold for metal nanoparticles, preferably gold nanospheres, of 15 nm to 35 nm, creating plasmonic nanoclusters. The self-assembled nanoclusters gave rise to a 10-fold surface-averaged enhancement of the local electromagnetic field. Other viral capsids or virus-like proteins may also serve as such scaffolds.
Core Innovation
The invention describes a nanocluster consisting of a cowpea mosaic virus (CPMV) protein capsid genetically modified to incorporate multiple cysteine residues that provide thiol groups on the exterior surface. Metal nanoparticles, preferably gold nanospheres sized between 15 nm and 35 nm, bind to these thiol groups to create plasmonic nanoclusters. This self-assembly of nanoclusters results in a significant surface-averaged enhancement of the local electromagnetic field, approximately tenfold.
A broader challenge addressed by the invention lies in producing materials that have negative electric permittivity and magnetic permeability at optical or near infrared frequencies, facilitating negative index materials (NIMs) with applications such as superlenses surpassing diffraction limits. Creating such optical metamaterials requires nanoscale structures with precise spatial control. Traditional nano-lithographic techniques are time-consuming, expensive, and limited in registration over extended scales, especially for structures sized 10s of nanometers, making fabrication of high-resolution nanoscale metamaterial structures difficult.
The invention solves this problem by employing genetically engineered viral capsids, such as CPMV capsids, as protein scaffolds for the self-assembly of metal nanoparticles. This method enables the formation of plasmonic nanoclusters with consistent inter-particle spacing and symmetry derived from the virus's icosahedral structure. The protein capsid scaffold is pre-fabricated, stable, and supports spatially organized metallic nanoparticles, facilitating the production of metamaterial optical elements effective in the visible spectrum. Additionally, the invention contemplates methods for synthesizing and purifying these nanoclusters, optimizing reaction conditions, and creating complex coupled plasmonic ring resonator structures.
Claims Coverage
The patent includes two independent claims describing nanoclusters based on viral protein capsids and metal nanoparticles, with emphasis on genetically modified capsids possessing thiol groups for nanoparticle binding, and metal nanoparticles of specific size ranges.
Nanocluster comprising a genetically modified CPMV capsid with metal nanoparticles
A nanocluster comprising a cowpea mosaic virus (CPMV) protein capsid genetically modified to incorporate multiple cysteine residues that provide thiol groups on the exterior surface, with a plurality of metal nanoparticles sized between 15 nm and 35 nm bound to these thiol groups.
Nanocluster comprising a viral protein capsid with thiol groups bound to metal nanoparticles
A nanocluster comprising a viral protein capsid containing thiol groups suitable for binding metallic nanoparticles, where the metal nanoparticles are sized between 15 nm and 35 nm and are bound to those thiol groups; the capsid may be genetically engineered to incorporate these cysteine residues.
The independent claims cover self-assembled nanoclusters formed by binding metal nanoparticles within a defined size range to thiol groups on genetically modified viral protein capsid scaffolds, particularly with CPMV, establishing the core inventive feature of a biomolecular scaffold-directed assembly of nanoscale plasmonic clusters.
Stated Advantages
Provides a stable, genetically encoded scaffold that enables precise and symmetric organization of metal nanoparticles at nanoscale dimensions, overcoming limitations of nano-lithography for producing high-resolution metamaterial structures.
Enables fabrication of plasmonic nanoclusters and optical metamaterials operating in the visible and near infrared spectrum, which had been difficult due to challenges in producing nanoscale resonators at optical wavelengths.
Allows production of large quantities of uniform nanoclusters through biological self-assembly with scalability, low cost, and reproducibility, leveraging virus particle stability and protein manufacturing by E. coli.
Supports three-dimensional optical elements functional in any orientation and improved stability over flat structures such as TMV disks, due to the icosahedral symmetry and robustness of CPMV capsids.
Documented Applications
Fabrication of negative index materials (NIMs) for superlenses capable of overcoming diffraction limits by enhancing and recovering evanescent waves for improved optical resolution.
Construction of nanoscale plasmonic ring resonators and coupled plasmonic ring resonator assemblies functioning as components of nanostructured circuit elements (NSEs) with optical or near infrared frequency resonance.
Creation of optically active metamaterials with tunable electromagnetic responses by incorporating semiconductor nanoparticles and fluorophores to switch or tune optical properties and introduce optical gain.
Potential use in devices excited by various sources including natural light, laser light, or electric fields, relevant for photonics and plasmonic applications.
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