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.

光谱学可用于快速表征单个分子的结构特性。然而，由于光通常对组分分子的空间分布是看不见的，因此不能应用于生物组装。这种不灵敏性是由于组件之间的长度比例（几十纳米）和激发发色团所需的光波长（≥150nm）不匹配造成的。因此，利用常规的光谱学，有序的组件，例如病毒的二十面体衣壳，似乎是无法区分的各向同性球形物体。这将潜在的途径限制为适用于即时诊断的快速高通量便携式检测。在这里，我们证明了近场的手性电磁（EM）约10 nm），可以检测病毒衣壳的二十面体结构。因此，他们可以检测结合的病毒衣壳的存在和相对方向。为了说明亚波长超手征场的精细结构敏感性的潜在用途，我们已使用它们成功地检测了复杂血清环境中的病毒颗粒。