Detecting DNA Hybridization with Liquid Crystals

Kevin Daly1, Stephanie Malone2, and Daniel K. Schwartz2. (1) Chemical and Biomolecular Engineering, Rice University, 9 Sunset Blvd., Houston, TX 77005, (2) Chemical and Biological Engineering, University of Colorado at Boulder, ECCH 111, CB 424, Boulder, CO 80303

Nematic liquid crystals may prove to be a low-cost detection scheme for hybridization of DNA in a microarray if they can be demonstrated to align differently based on whether they are in the vicinity of single-stranded or double-stranded DNA. We deposited double-stranded DNA molecules on a functionalized glass surface, using the molecular combing technique to extend them in a controlled direction in the plane of the surface. We then incorporated the surface into a hybrid aligned nematic cell and observed that liquid crystals in the cell align at an azimuthal angle of 45 degrees to the direction of combing, an alignment that also happens to be consistent with hydrophobic attraction we would expect between non-polar tails of the liquid crystal molecules and grooves in the double helix of DNA. This alignment demonstrates that liquid crystals are highly sensitive to the molecular structure of DNA, and suggests that they may be similarly sensitive to single-stranded DNA, aligning at an angle distinct from the angle for double-stranded DNA.