Self-Assembled Lipid Tubules: Synthesis, Characterization, and Ordered Arrays
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0922-U05-02
Self-Assembled Lipid Tubules: Synthesis, Characterization, and Ordered Arrays Yue Zhao, Nidhi Mahajan, and Jiyu Fang Advanced Materials Processing and Analysis Center, Dept. of Mechanical, Materials, and Aerospace, Unviersity of Central Florida, Orlando, FL, 32816
ABSTRACT The rolling of lipid bilayer sheets into hollow cylindrical tubules have emerged as a group of interesting supramolecular nanostructures. Here, we image the self-assembled tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphochloline (DC8,9PC) with atomic force microscopy. Nanoscale ripple structures with a periodicity of ~ 200nm in the cylindrical lipid tubules are observed. We develop two simple methods based on microfluidic networks (µFN) and surface patterning to produce two dimensional ordered arrays of parallel aligned lipid tubules on substrates. INTRODUCTION The self-assembled lipid tubules represent interesting hollow, open ended cylindrical supramolecular structures 1-2. A number of synthetic lipids with modified head groups or acyl chains are able to self-assemble into tubule structures in solutions 3-7. The hollow cylindrical shape and the tunable size distribution make the tubules potentially valuable as a template for the directed-synthesis of one-dimensional hybrid materials with high aspect-ratio 8-11, a substrate for the helical crystallization of proteins 12-13, and an encapsulation for long-term release of chemical and biological agents in soft tissue regeneration and antifouling 14-15. In this paper, we report atomic force microscopy studies of nanoscale ripples in the hollow cylindrical tubules of 2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphochloline (DC8,9PC). We present two efficient methods to achieve the alignment and positioning of the lipid tubules on substrates. EXPERIMENT Lipid tubules used in our experiments were prepared by cooling a 5 mg/mL solution of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphochloline (DC8,9PC) (Avanti Polar Lipids, Alabaster, AL) in ethanol/water (70:30 v/v) from 60 °C to room temperature at a rate of ~ 0.5°C/min. The polymerization of the DC8,9PC tubule suspension was performed with the UV irradiation (254 nm) for 20 min at room temperature. In the µFN technique, an oxygen plasma treated PDMS stamp having parallel channels was carefully placed on a cleaned glass substrate to form rectangular capillaries (Figure 1a). The capillaries have a height of 800nm and widths of 1µm and 2 µm. They are separated by 2 and 4 µm, respectively. A droplet of tubule suspensions was pulled into the rectangular capillaries from one of the open ends by capillary action. The tubule solution-filled capillaries were dried in air at room temperature. After removal of the
PDMS stamp, the aligned lipid tubules were left on the glass substrate (Figure 1b). In the dip-coating technique, the patterned Au substrates were formed with microcontact printing (µCP) technique (Figure 1c). 1-Dodecanethiol (DDT) (Aldrich) (a) (b) was dissolved in ethanol with a PDMS stamp concentration of 1 mM. A
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