Superchiral near fields detect virus structure

Abstract

Optical spectroscopy can be used to quickly characterise the structural properties of individual molecules. However, it cannot be applied to biological assemblies because light is generally blind to the spatial distribution of the component molecules. This insensitivity arises from the mismatch in length scales between the assemblies (a few tens of nm) and the wavelength of light required to excite chromophores (≥150 nm). Consequently, with conventional spectroscopy, ordered assemblies, such as the icosahedral capsids of viruses, appear to be indistinguishable isotropic spherical objects. This limits potential routes to rapid high-throughput portable detection appropriate for point-of-care diagnostics. Here, we demonstrate that chiral electromagnetic (EM) near fields, which have both enhanced chiral asymmetry (referred to as superchirality) and subwavelength spatial localisation (∼10 nm), can detect the icosahedral structure of virus capsids. Thus, they can detect both the presence and relative orientation of a bound virus capsid. To illustrate the potential uses of the exquisite structural sensitivity of subwavelength superchiral fields, we have used them to successfully detect virus particles in the complex milieu of blood serum.

Nanophotonic Approaches for Chirality Sensing

“…The different phases indicate that protein orientation is distinguishable using this polarimetry technique. More recently, Kadodwala and co-workers used the same optical approach to probe the structural order of protein monolayers, specificity of antibody–antigen systems, protein charge distributions, and virus capsids …”

“…More recently, Kadodwala and co-workers used the same optical approach to probe the structural order of protein monolayers, 188 specificity of antibody−antigen systems, 189 protein charge distributions, 190 and virus capsids. 191 Achiral Plasmonic Substrates. Achiral plasmonic nanoantennas can be used to generate superchiral near-fields, despite often lacking significant magnetic field enhancement.…”

Chiral Plasmonic Nanowaves by Tilted Assembly of Unidirectionally Aligned Block Copolymers with Buckling-Induced Microwrinkles

“…Recent advances in the field of chiral nanomaterials have drawn great attention because of the distinctive chiroptical properties of such nanomaterials , and their potential applications in advanced optical and biomedical devices, such as metamaterials, , holographic displays, chiroptical field separations, , and biosensor platforms. , Nanostructured materials with chiral geometries can preferentially interact with circularly polarized light in specific wavelength ranges that are mainly attributed to the electronic transitions, charge transfer, and plasmonic absorptions of the constituent materials. The three-dimensional shapes of chiral structures significantly affect the appearance and magnitude of chiroptical responses.…”

Detecting Antibody–Antigen Interactions with Chiral Plasmons: Factors Influencing Chiral Plasmonic Sensing

“…This phenomenon offers an appealing route to novel ultrasensitive biosensing technologies with ≤pg detection limits. [8,[14][15][16][17][18][19][20][21] For this phenomenon to be exploited effectively requires an understanding of chiral light-matter interactions. The crucial issues to be addressed are: how the introduction of chiral media into the near field region of nanostructures leads to a significant asymmetry in a far-field chiroptical response; and is the detection phenomena generic or are there constraints placed on the nature of the types of chiral media that can be detected?…”