Polarization Used to Identify Pathogens, Clinically Relevant Compounds

At ETH Zurich researchers are relying on detecting the polarization of light as it passes through a substance as a potential diagnostic tool for spotting a variety of biomarkers. In initial tests of the technology, the team was able to identify malaria infection (by detecting of hemozoin crystallites), but also HIV and Ebola, as well as glucose and cholesterol.

The technique relies on birefringence, the polarization effect that many crystals (and liquids) create when light passes through them. Specifically the investigators are using lyotropic liquid crystals based on lipids that are safe for biological use.

Some details about the workings of the technology according to ETH Zurich:

Lyotropic liquid crystals organise themselves into special networks with unique symmetry, which means that their basic motif repeats itself periodically. In the case of liquid crystal cubic phases, the channels are made of lipid bilayer membranes in water and have a diameter of just a few nanometres, so only few free water molecules are available in the liquid crystal, whereas the majority is bound to the channel walls. These liquid crystal cubic phases are isotropic, or so to say, do not have any birefringent properties, which means that if a slide with a layer of lyotropic liquid crystal films is placed under a light source that allows polarised light to pass through, it appears black when observed through another polarizer tilted at 90°.

To achieve birefringence and thus receive a signal, the researchers reached again into their bag of tricks: they added certain enzymes to the liquid crystal to allow a chemical reaction to take place in the nanotubes. Since only a small amount of water is freely available in the nanotubes, the products of the reactions precipitated together to form crystals, which are themselves birefringent. A closer look at the sample through a second polarisation filter placed above it and perpendicular to the first shows a light pattern in instances where the enzyme has reacted with the substance tested.

Study in Advanced Functional Materials: Lipidic Cubic Phases as a Versatile Platform for the Rapid Detection of Biomarkers, Viruses, Bacteria, and Parasites…

Source: ETH Zurich…