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Analytical Methodology Based on Soft Material Interfaces for Biomolecular Sensing

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Analytical Methodology Based on Soft Material Interfaces for Biomolecular Sensing
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<strong>School of Physical Sciences Jawaharlal Nehru University, New Delhi</strong> <strong>Analytical Methodology Based on Soft Material Interfaces for Biomolecular Sensing</strong> <strong>Dr. Abhijit Dan</strong> Institute of Advanced Study in Science and Technology – Guwahati <strong>Date: June 22, 2016 </strong> <strong>Abstract:</strong> This work focuses on recent advances in the design of soft materials that are based on confinement of low molecular weight liquid crystals (LCs) within micrometer-sized droplets. We report a methodology for rapid detection of bacterial lipopolysaccharide endotoxins based on measurement of light scattered by water-dispersed microdroplets of thermotropic liquid crystal (LC) as they are passed through a flow focusing device. The endotoxin triggers a transformation in the internal ordering of the LC within the droplets (ordering transition) from a bipolar to a radial configuration [1,2] which results in a change in the light scattered by the droplets at low angles (&lt; 15° away from incidence; FSC). The flow focusing device used in our study, which was part of a flow cytometer, permitted analysis LC droplets at rates of up to 10,000 droplets per second, and thus provides the basis of a more rapid and statistically robust method of analysis of endotoxin than can be achieved by methods such as optical microscopy. The methodology is used to demonstrate quantification of endotoxin in solution in the picogram per milliliter (pg/mL) range in the presence of protein that was selected for the anticipated interaction with the endotoxin in solution or with the surface of the LC droplets. Through such measurements of the effects of the protein on the endotoxin-induced configurational transition, we provide insight into the mechanism by which endotoxin triggers the configurational transitions. In addition, the measurements reveal the extent to which we identify the potential reason for interference of protein on endotoxintriggered changes in the configuration of the LC droplets, thereby providing a rigorous technical foundation for future optimization of the method. We describe a simple method which neutralizes the interfering effect of proteins and results in an improved detection of endotoxin. This approach opens up new opportunities for the design of soft responsive materials based on surface-induced ordering transitions. Overall, these results advance our understanding of ordering transitions triggered by the interactions of analytes with LC droplets and, more broadly, provide guidance to the design of LC droplet systems as the basis of stimuli-responsive soft materials. 1) H. Lin, D. S. Miller, P. J. Bertics, C. J. Murphy, J. J. de Pablo and N. L. Abbott, Science, 2011, 332, 1297-1300. 2) D. S. Miller and N. L. Abbott, Soft Matter, 2013, 9, 374-382.