The overall objectives of this project involve the development of methods where liquid crystals (LC) are used to detect nucleic acid hybridization. Also, to obtain an improved understanding of the fundamental molecular-level mechanisms by which the interfacial interactions of nucleic acids affect LC orientation. The ultimate long-term goal of this research is to enable LC-based detection in medical diagnostic applications, e.g. multiplexed methods (i.e. DNA microarrays) based on the orientational response of LCs to DNA hybridization, that use the transmission of polarized light to detect the LC response. Intellectual Merit Two distinct approaches will be developed, and so the specific aims and research strategies of this project fall into two groups. The first approach involves a dynamic change of the LC polar tilt angle at the LC/aqueous interface in the presence of a monolayer of cationic surfactant, and the specific aims associated with this approach include the development of a multiplexed platform, quantitative studies of sensitivity and target generality, the development of fluorescence microscopy methods that can be used to study the LC/aqueous interface, and the application of these methods to understand the molecular mechanisms of LC response to DNA hybridization. Finally, this method will be directly validated by experiments that will discriminate between closely-related bacterial pathogens. The second approach involves a characteristic chiral rotation of the azimuthal orientation of planar-anchored LC when the LC is in contact with extended dsDNA. The associated specific aims include quantitative studies of the macroscopic optical response, extension of the method to the detection of single hybridized molecules, development of methods that enable multiplexed detection using covalently immobilized probes, and mechanistic studies aimed at understanding the distinctive LC response to ssDNA and dsDNA. Similar validation experiments (i.e. discrimination between related bacteria) will be pursued for this method as for the first method. Broader Impact The methods developed here have the long-term potential to be used in new medical diagnostic technologies that are appropriate for point-of-use applications including those in low resource environments. Furthermore, the fundamental understandings obtained about LC-biomolecule interactions will be broadly useful for researchers pursuing LC-based biosensing approaches. More broadly, the optical characterization methods developed will be of use for studies of the LC-liquid interface and for other liquid-liquid interfaces. The researchers involved in this project will gain expertise in multidisciplinary areas projected to be at the forefront of science and technology in the coming decades, including liquid crystal devices, biodetection, single-molecule microscopy, and self-assembled molecular systems. Also, through their participation in a variety of educational and outreach programs (e.g. REU, RET, GAANN, CU-Discovery Learning Center, Materials Science from CU K-12 outreach, Colorado High School Honors Institute), the researchers will continue to share this project with students, teachers, and other community members. As summarized in the proposal the PI and previous students and post-docs involved in this project have demonstrated a sincere and continuing commitment to the creative use of their research in the pursuit of education and outreach; the integration of basic discovery and cutting-edge microscopy methods in this project will provide an ideal platform from which to communicate the excitement of research to the general public.
