Lightguiding nanowires as a platform for sensitive detection of fluorescent biomolecules in non-transparent media, including whole human blood

Sensitive detection of biomolecules in complex, non-transparent biological media is highly desirable for diagnostics and food safety. Semiconductor nanowires strongly amplify fluorescence signals, however their application has been largely limited to transparent media due to the scattering and absorption arising in turbid sample matrices. We present a detection platform based on polymer-supported semiconductor nanowires that enables highly sensitive fluorescent detection in turbid media using a model biotin–streptavidin system. By anchoring the nanowires vertically in an optically transparent polymer, both excitation and emission are directed through the nanowires rather than through the sample, thereby decoupling the optical path from the turbid medium and reducing scattering- and absorption-related light attenuation. This enables sensitive detection of fluorescent signals from nanowire-bound molecules in highly scattering fluids using standard epi-fluorescence microscopy. We demonstrate detection of fluorescently labelled streptavidin at 1 nM in reconstituted powdered milk and 100 pM in whole human blood and lipid emulsion. This method enables spatially resolved, highly sensitive measurements with minimal sample preprocessing and without relying on specialized techniques, such as TIRF.