(193f) Real-Time Detection of Lipid Bilayer Assembly and Detergent-Initiated Solubilization

The cellular membrane governs numerous fundamental biological processes, and therefore, developing a comprehensive understanding of its structure and function is critical.  However, because of its inherent complexity, this challenge is as yet unsolved.  In an attempt to develop a model, two different experimental approaches are being pursued in parallel: performing single cell experiments (top down) and using biomimetic structures (bottom up), such as lipid bilayers.  One challenge in many of these experiments is the reliance on fluorescent probes for detection.  In the present work, we have used a label-free detection method based on an evanescent optical sensor known as an optical resonant cavity.  In this approach, we are able to detect the self-assembly and solubilization of lipid bilayers in real-time.  Specifically, using these silica devices, there are two independent detection mechanisms which are able to confirm the formation and detergent assisted solubilization of the lipid bilayers: 1) a refractive index change and 2) a material loss change.  Both mechanisms can be monitored in parallel, on the same device, thus allowing for cross-confirmation of the results.  To verify the proposed method, we have detected the formation of self-assembled phosphatidylcholine lipid bilayers from small unilamellar vesicles (SUVs) on the device surface in real-time.  Subsequently, we exposed the bilayers to two different detergents (non-ionic Triton X-100 (TX-100) and anionic sodium dodecyl sulfate (SDS)) to initiate solubilization, and this process was also detected in real-time.  After solubilization, the device returned to its initial state, exhibiting minimal hysteresis.  The experimental wash-off was also collected and analyzed using dynamic light scattering (DLS).