A Cholesterol‐Based Tether for Creating Photopatterned Lipid Membrane Arrays on both a Silica and Gold Surface

Abstract

Surfing gold and silica! A new cholesterol-based tether was attached to both amine-functionalised silica and gold surfaces. The resultant self-assembled monolayers, which can be deep-UV-patterned, were used in attaching essentially equivalent patterned supported lipid bilayers both on silica for fluorescence studies (left figure) and on gold for impedance studies (right figure).We report a new cholesterol-based self-assembled monolayer (SAM) for use in attaching lipid membranes to both gold and silica surfaces that can be patterned by deep UV (254 nm) photolysis. It allows essentially equivalent patterned supported bilayers to be created both on gold for impedance studies and on silica for fluorescence studies. On either surface an amine-functionalised SAM is reacted with an N-hydroxysuccinimidylcarbonyl-functionalised EO3-cholesteryl derivative. The formation of the amine-functionalised SAM and its reaction with the EO3-cholesteryl derivative were followed by contact-angle measurements, ellipsometry and X-ray photoelectron spectroscopy. The resultant layer of cholesterol tethers was patterned by deep UV photolysis, which regenerates the original SiO(2) surface in exposed regions on a silica substrate and oxidises thiol groups on a gold substrate. This patterned surface containing hydrophilic SiO(2) (or -OH groups) and hydrophobic cholesterol tether regions can be converted to a surface patterned with supported lipid bi- and monolayers (respectively) by immersing in a solution of small unilamellar vesicles of egg yolk phosphatidycholine. The formation of the lipid bi- and monolayer regions on the silica surface was evidenced by fluorescence microscopy. Crucially the bilayer regions remain fully fluid yielding lipid mobilities comparable to those found in physisorbed bilayers. Furthermore charged fluorescent lipids are shown to migrate in an applied field thus providing a platform for the studying the electrophoresis (potentially) for a wide range of charged membrane components, such as membrane proteins. The formation of the patterned lipid membrane on the gold surface was confirmed by electrochemical impedance measurements.

Epigenetic Reprogramming in Cancer

“…For instance, loss of TET2 activity is frequently observed in myeloid malignancies resulting from the 4q24 deletion (Viguie et al 2005) or loss-of-function mutations (Abdel-Wahab et al 2009;Han et al 2009;Jankowska et al 2009;Langemeijer et al 2009;Tefferi et al 2009a, b, c). In contrast, mutations in TET1 and TET3 have not been identified in cancer.…”

Nanofabrication for the Analysis and Manipulation of Membranes

“…63,68 Surface-immobilized monolayers of n-octadecylsiloxanes 37 and chlorotrimethylsilanes 31 have provided a means of patterning just the bottom bilayer leaflet. With electron beam lithography, nanoscale membrane patterns have been created with silanes conjugated to amphiphilic lipid molecules 45 or cholesterol derivatives 30 through immobilization to nanoscale patterned noble metals. Sub-diffraction-limited, near-field illumination may provide a means of selectively polymerizing membrane components with nanoscale resolution on living samples.…”

Fluorescence modulation sensing of positively and negatively charged proteins on lipid bilayers

“…This makes the ability to effectively monitor such systems key for therapeutics and drug discovery. Consequently, much work has been done to produce supported lipid bilayers that mimic the cell surface with various supports [17][18][19][20] and tethers [21][22][23][24][25][26]. By embedding these bilayers into microfluidic devices, [27] one can probe binding ligands rapidly while utilizing only small amounts of analyte.…”