Watch a short animation that illustrates the molecular basis of the change in appearence of the liquid crystals.
Liquid crystals (LCs) could provide a cheap, portable and power-free readout for a variety of biosensing applications. Inspired by the work of Abbott and co-workers at the University of Wisconsin-Madison, a joint project on LCD-based biosensing was initiated with Prof. Rein Ulijn. We recently created LCD biosensors for proteases (a class of enzyme). These sensors have a solid-phase synthesis surface bearing an enzyme-sensitive substrate placed over an LC display constrained within a transmission electron microscopy (TEM) grid. The liquid crystals are initially aligned parallel to the overlying aqueous interface and appear bright when viewed through crossed polarisers. However the addition of protease cleaves the substrate, generating a surfactant that self-assembles at the LC/aqueous interface. This causes the LC to realign perpendicular to the overlying aqueous interface, changing the optical properties of the liquid crystal and giving a light to dark optical signal in the LC display.
A new development in this device uses self-assembled molecular hydrogels to provide faster response times and more robust sensors. These gels are enzyme-responsive, leading to the generation of surfactants that realign the LC display. By selecting the appropriate hydrogel, different enzymes can be detected with excellent sensitivity and selectivity.
A combined SPS-LCD sensor for screening protease specificity.
Chemical Communications, (25): 2861-2863 2008.