MOLECULAR MODELING STUDIES FOR DEVELOPMENT OF SENSORS FOR ORGANOPHOSPHATES

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。目前的研究涉及使用基于纳米技术进步的传感器和使用液晶来感知杀虫剂的存在。目前正在研究仿真方法以改进传感器的设计。正如若干纳米技术应用的发展一样，不同的问题可以在不同的长度和时间尺度上进行模拟研究。例如，我们有兴趣提高传感器的特异性（区分类似分析物的能力）以及灵敏度（检测低浓度分析物的能力）。分子尺度模拟更适合理解与特异性相关的问题，而连续尺度模拟更适合估计敏感性。而在本研究的早期努力集中在分子尺度的模拟，在后期更多的重点放在连续尺度模型的使用。与使用商业软件的涉及分子尺度模拟的研究不同，连续尺度建模的努力需要开发执行模拟的软件。该模型的开发结合了三维非结构化网格的使用来模拟复杂的几何形状，并在并行环境中解决问题，从而受益于使用大型计算机集群来解决实际问题配置。已经进行了测试案例，以获得在分析物分子存在下液晶的取向。分析物分子目前已被建模为球体，未来将涉及更现实的几何形状。通过不同浓度的模拟，研究了分析物浓度对液晶介质显示的光学图形的影响。这样的研究可以估计分析物的最低浓度（传感器的灵敏度），可以通过液晶介质的光学模式的变化来检测。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The present study involves the use of a sensor based on advances in nanotechnology and the use of liquid crystals to sense the presence of pesticides. Simulation approaches are being studied to improve the design of the sensor. As is the case with development of several nanotechnology applications, different problems are amenable to simulation studies performed at different length and time scales. For example, we are interested in improving the specificity of the sensor (ability to distinguish between similar analytes) as well as its sensitivity (ability to detect low concentrations of analyte). Molecular scale simulations are more suitable for understanding issues related to specificity and continuum scale simulations are more appropriate for estimating sensitivity. Whereas the earlier efforts in this investigation focused on molecular scale simulations, in the later stage more emphasis has been placed on use of continuum scale models. Unlike the studies involving molecular scale simulations for which commercial software was used, the effort in continuum scale modeling requires development of the software for performing the simulations. This model development incorporates the use of three-dimensional unstructured grids to model complex geometry, and, problem solving in a parallel environment to benefit from the use of large computer clusters for solving practical problem configurations. Test cases have been performed to obtain the orientation of the liquid crystal in the presence of analyte molecules. The analyte molecules have been modeled as spheres at present and will involve more realistic geometries in the future. The effect of concentration of the analyte on the optical pattern displayed by the liquid crystal medium has been studied by performing simulations at different concentrations. Such studies enable estimation of the minimum concentration of the analyte (the sensitivity of the sensor) that can be detected through changes caused in the optical pattern of the liquid crystal medium.