Cell membranes are a complex mosaic of different lipids, with cholesterol, sphingolipids and membrane proteins forming nanoscale domains called lipid rafts. Lipid rafts transiently compartmentalize membrane constituents, which in turn mediate cellular functions in space and time. In order to quantitatively investigate the formation, morphology and signal transduction mechanisms mediated by lipid rafts and proteins integrated therein, they must be probed in artificial nano-environments that closely resemble real cell membranes. Analytical instruments that integrate lipid membranes with engineered solid-state sensors that can better mimic natural cellular environments will therefore offer deeper insights into important in vivo reactions and processes. The proposed platform will integrate soft lipid matter with the native sensing capability of nanoporous metallic films. Namely, surface plasmon resonance (SPR) and electrochemical sensing will be used to probe the biological processes mediated by lipid rafts and membrane proteins. However, noble metals such as gold or silver required for SPR have typically not been amenable to large-area, low-cost patterning at nanometer-scale resolution. To overcome this challenge, template-stripping methods will be used for reproducible high-throughput fabrication of ultrasmooth nanoporous metallic films that will be used as a multi-functional platform combining nanofluidics, optical detection, spectroscopy, and electrochemical sensing. The development of a membrane biosensing platform capable of molecular binding and transport assays will provide new tools to probe the dynamic heterogeneity of cellular membranes and the fundamental life processes they enable. Overall, disseminating these instruments will enable biologists to control, image, and quantitatively analyze lipid membranes and their constituents, potentially down to the single-molecule level, using precisely engineered biomimetic nano-environments. For broader outreach, the PI will organize "Sit with a Scientist" sessions and build an interactive Activity Station at the Science Museum of Minnesota during the one week-long NanoDays event in April of each year. The PI's exhibition booth at the museum will feature the theme of "Macro- to Microfluidics", with on-site demos of microfluidic devices for K-12 students. Graduate and undergraduate students associated with the project will gain interdisciplinary training ranging from nanofabrication and optics to chemistry and cellular membranes. Women and underrepresented minorities will be given opportunities to experience nanofabrication through NSF REU programs. The PI's new graduate course on biological instrumentation will integrate his research and education through theoretical lectures and weekly hands-on lab sessions to teach the construction and operation of membrane biosensors. New instruments and technology will be disseminated to the research community through an already active biannual, two-day bioMEMs short course. The process of making smooth patterned gold films, integration with microfluidics, lipid membrane formation, followed by SPR and electrochemical sensing will be demonstrated, allowing other researchers to duplicate the chip fabrication and instrument buildup.
