

Physicists and engineers at Case Western Reserve University have developed an optical sensor, based on nanostructured metamaterials, that's 1 million times more sensitive than the current best available—one capable of identifying a single lightweight molecule in a highly dilute solution. Their goal: to provide oncologists a way to detect a single molecule of an enzyme produced by circulating cancer cells. Such detection could allow doctors to diagnose patients with certain cancers far earlier than possible today, monitor treatment and resistance and more.

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Ref: Extreme sensitivity biosensing platform based on hyperbolic metamaterials. Nature Materials (28 March 2016) | DOI: 10.1038/nmat4609

ABSTRACT

Optical sensor technology offers significant opportunities in the field of medical research and clinical diagnostics, particularly for the detection of small numbers of molecules in highly diluted solutions. Several methods have been developed for this purpose, including label-free plasmonic biosensors based on metamaterials. However, the detection of lower-molecular-weight (<500 Da) biomolecules in highly diluted solutions is still a challenging issue owing to their lower polarizability. In this context, we have developed a miniaturized plasmonic biosensor platform based on a hyperbolic metamaterial that can support highly confined bulk plasmon guided modes over a broad wavelength range from visible to near infrared. By exciting these modes using a grating-coupling technique, we achieved different extreme sensitivity modes with a maximum of 30,000 nm per refractive index unit (RIU) and a record figure of merit (FOM) of 590. We report the ability of the metamaterial platform to detect ultralow-molecular-weight (244 Da) biomolecules at picomolar concentrations using a standard affinity model streptavidin–biotin.