Label-free detection of viruses
In cooperation with Heraeus Quartz Glass, Harvard University in the USA and Leiden University in the Netherlands, scientists at the Leibniz Institute of Photonic Technologies (IPHT) have succeeded in the label-free detection of freely diffusing viruses measuring smaller than 20 nanometres. In light of the increase in viral diseases and their distribution, precise detection of viruses is becoming increasingly important.
The basis for the detection is a fibre with a core integrating a nano-hole with a diameter of 200 nanometres. Within this, there are test viruses swimming in water. When light is coupled with the fibre core, the size and movement of the viruses is determined via elastic light scattering. The fibres are special because the smaller refractive index of the water is bypassed by the surrounding fibre material with a higher refractive index, thereby preventing the coupled light from lateral escape, i.e. the light is held in the core by way of total internal reflection.
The fibres developed at IPHT and by Heraeus Quartz Glass can be integrated in standard microscopes, thereby expanding their detection range to nanoparticles. The applications range from medical diagnostics to drinking water analysis. Owing to their size, objects less than 100 nanometres often elude conventional characterisation methods. Therefore, viruses that are present in a high quantity are generally visualised by a fluorescent dye in the electron microscope after fixation and staining or through the binding of fluorescence-labelled antibodies.
The fibres and measurement techniques were developed in the IPHT research group with the Markus Schmidt group in cooperation with Heraeus Quartz Glass, Harvard University in the USA and Leiden University in the Netherlands.