Micropatterned Thermoresponsive Nanocomposite Hydrogel Surfaces with Self-Cleaning Behavior

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。0854462 GrunlanINTELLECTUAL MERIT该项目研究了微纳米结构纳米复合水凝胶材料的温度控制活化，以产生温度控制的自清洁表面。温度的周期性变化将通过将这些纳米复合材料水凝胶微柱从水溶胀状态来回切换到去溶胀状态来激活它们。该活化过程将导致表面性质的显著且快速的变化，最终允许表面自身去除粘附的生物污染物质，例如细胞。所提出的微结构化纳米复合水凝胶可特别用于设计自清洁植入式生物传感器膜或其性能受到生物污垢损害的其它表面。增强温度激活自清洁将通过利用材料设计和微图案化设计组件的双管齐下的方法来实现。研究人员将制备由聚（N-异丙基丙烯酰胺）（PNIPAAm）水凝胶基质和不同水平的胶体聚硅氧烷纳米颗粒组成的新型纳米复合水凝胶。已知PNIPAAm水凝胶在高于约35 °C的体积相变温度（VPTT）的温度下从水溶胀可逆地转换到收缩（去溶胀）状态时变得更加疏水。这种温度激活的表面亲水性/疏水性的变化已经显示出破坏吸附的细胞和蛋白质的粘附。在初步研究中，可变的聚硅氧烷纳米颗粒水平用于定制PNIPAAm水凝胶的温度依赖性表面性质。与纯PNIPAAm水凝胶相比，这些纳米复合材料水凝胶表现出上级机械强度，但不改变VPTT（方便地接近体温）。对于每种独特的组合物，将制备纳米复合水凝胶微结构（例如微柱），并且由于其尺寸大小，应产生快速切换表面，其中亲水性/疏水性的变化与其平面（即非微图案化）类似物相比非常明显。调整纳米复合水凝胶组合物和微结构形貌将最终导致表面可以快速和剧烈地响应温度变化，因此经历温度控制的自清洁。更广泛的改进该项目设计的强大的自清洁表面，打击生物污垢有可能提高许多商业设备的性能寿命。具体而言，本研究中设计的表面有可能使长期植入的生物传感器（例如，用于葡萄糖监测）成为临床现实。本研究还将揭示聚硅氧烷纳米颗粒和微柱形貌在定制PNIPAAm水凝胶自清洁性能中的作用。除了研究的进步，这项工作将有效地培养本科生和研究生在一个广泛的，多学科的研究计划，包括材料设计表征，软纳米复合材料的微细加工，及其直接应用于自清洁。这项研究的多学科性质将提供一个独特的培训环境，研究生和本科生从生物医学工程，电气工程和化学工程部门在得克萨斯州A M大学。Melissa Grunlan博士（PI;部门生物医学工程）将指导设计和合成平面纳米复合水凝胶的工作，并表征其材料特性。Dr. Arum Han（Co-PI;部门电气工程的），在生物应用纳米微制造的专家，将专注于通过各种光聚合和压印方法使用在Grunlans博士实验室开发的材料的微图案表面的制备。Dr. Mariah Han（Co-PI;部门将提供细胞释放研究方面的专业知识。在整个过程中，将通过每周小组会议提供反馈，以探索最佳材料表面形貌组合，以实现最佳温度激活自清洁行为和高效微加工。这项研究将加强三个部门之间现有的伙伴关系，并有效地利用PI，Co-PI和大学中心的资源。我们将积极招募博士前候选人从代表性不足的群体，他们在夏季德州农工大学赞助的计划和整个学年的指导研究的参与。拟议工作的各个方面将被教授给就读于PI和Co-PI教授的课程的本科生和研究生。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). 0854462GrunlanINTELLECTUAL MERIT The project investigates temperature controlled activation of micro nano structured nanocomposite hydrogel materials to produce temperature controlled self cleaning surfaces. Cyclical changes in temperature will activate these nanocomposite hydrogel micropillars by switching them back and forth from a water swollen to deswollen state. This activation process will lead to pronounced and rapid changes in surface properties ultimately allowing surfaces to rid themselves of adherent biofouling species such as cells. The proposed microstructured nanocomposite hydrogels may be particularly useful to design self cleaning implanted biosensor membranes or other surfaces whose performance is compromised by biofouling. Enhancing temperature activated self cleaning will be accomplished by a two pronged approach utilizing both material design and micropatterning design components. The investigators will prepare novel nanocomposite hydrogels consisting of poly (N-isopropylacrylamide) (PNIPAAm) hydrogel matrices and variable levels of colloidal polysiloxane nanoparticles. PNIPAAm hydrogels are known to become more hydrophobic when they reversibly switch from a water swollen to a shrunken (deswollen) state at temperatures above the volume phase transition temperature (VPTT) of ~35 °C. Such temperature activated changes in surface hydrophilicity/hydrophobicity have been shown to disrupt the adhesion of adsorbed cells and proteins. In preliminary studies, variable polysiloxane nanoparticle levels were used to tailor the temperature dependent surface properties of PNIPAAm hydrogels. These nanocomposite hydrogels demonstrated superior mechanical strength but did not alter the VPTT (conveniently near body temperature) compared to pure PNIPAAm hydrogels. For each unique composition, nanocomposite hydrogel microstructures (e.g. micropillars) will be prepared and, as a result of their size scale, should produce fast switching surfaces in which changes in hydrophilicity/hydrophobicity are very pronounced compared to their planar (i.e. non micropatterned) analogues. Tailoring nanocomposite hydrogel composition and microstructure topography will ultimately result in surfaces which could quickly and drastically respond to changes in temperature and hence undergo temperature controlled self cleaning. BROADER IMPACTS The project on design of robust self cleaning surfaces which combat biofouling has the potential to enhance the performance life time of many commercial devices equipment. Specifically, surfaces designed in this study have the potential to make long term implanted biosensors (e.g. for glucose monitoring) a clinical reality. This research will also reveal the role of polysiloxane nanoparticles and micropillar topography in tailoring the self cleaning properties of PNIPAAm hydrogels. Beyond the advancements in research, this work will effectively train undergraduate and graduate students in a broad, multi disciplinary research program consisting of materials design characterization, microfabrication of soft nanocomposite materials, and its direct application to self cleaning. The multidisciplinary nature of this research will provide a unique training environment for both graduate and undergraduate students from biomedical engineering, electrical engineering, and chemical engineering departments at Texas A&M University. Dr. Melissa Grunlan (PI; Dept. of Biomedical Engineering) will guide the efforts to design and synthesize planar nanocomposite hydrogels and characterize their material properties. Dr. Arum Han (Co-PI; Dept. of Electrical Engineering), an expert in nano microfabrication for bio applications, will focus on the preparation of micropatterned surfaces via various photopolymerization and imprint methods using the materials developed in Dr. Grunlans lab. Dr. Mariah Han (Co-PI; Dept. of Chemical Engineering) will provide expertise in cell release studies. Throughout the duration, feedback will be provided by combined weekly group meetings to explore the best material surface topography combinations for optimal temperature activated self cleaning behavior and efficient microfabrication. This research will strengthen the existing partnership between three departments and effectively utilize resources of the PI, Co-PIs, and university centers. We will actively recruit pre doctoral candidates from under represented groups by their participation in summer Texas A&M University sponsored programs and directed studies throughout the school year. Various aspects of the proposed work will be taught to undergraduate and graduate students enrolled in courses taught by the PI and Co-PI.