Department of Mechanical Engineering and Mechanics, Drexel University , Philadelphia, Pennsylvania 19104, United States.
ACS Appl Mater Interfaces. 2014 Aug 13;6(15):12618-28. doi: 10.1021/am502613x. Epub 2014 Jun 30.
The polar lipid fraction E (PLFE) isolated from the thermoacidophilic archaeon Sulfolobus acidocaldarius contains exclusively bipolar tetraether lipids, which are able to form extraordinarily stable vesicular membranes against a number of chemical, physical, and mechanical stressors. PLFE liposomes have thus been considered appealing biomaterials holding great promise for biotechnology applications such as drug delivery and biosensing. Here we demonstrated that PLFE can also form free-standing "planar" membranes on micropores (∼100 μm) of polydimethylsiloxane (PDMS) thin films embedded in printed circuit board (PCB)-based fluidics. To build this device, two novel approaches were employed: (i) an S1813 sacrificial layer was used to facilitate the fabrication of the PDMS thin film, and (ii) oxygen plasma treatment was utilized to conveniently bond the PDMS thin film to the PCB board and the PDMS fluidic chamber. Using electrochemical impedance spectroscopy, we found that the dielectric properties of PLFE planar membranes suspended on the PDMS films are distinctly different from those obtained from diester lipid and triblock copolymer membranes. In addition to resistance (R) and capacitance (C) that were commonly seen in all the membranes examined, PLFE planar membranes showed an inductance (L) component. Furthermore, PLFE planar membranes displayed a relatively large membrane resistance, suggesting that, among the membranes examined, PLFE planar membrane would be a better matrix for studying channel proteins and transmembrane events. PLFE planar membranes also exhibited a sharp decrease in phase angle with the frequency of the input AC signal at ∼1 MHz, which could be utilized to develop sensors for monitoring PLFE membrane integrity in fluidics. Since the stability of free-standing planar lipid membranes increases with increasing membrane packing tightness and PLFE lipid membranes are more tightly packed than those made of diester lipids, PLFE free-standing planar membranes are expected to be considerably stable. All these salient features make PLFE planar membranes particularly attractive for model studies of channel proteins and transmembrane events and for high-throughput drug screening and artificial photosynthesis. This work can be extended to nanopores of PDMS thin films in microfluidics and eventually aid in membrane-based new lab-on-a-chip applications.
从嗜热嗜酸古菌 Sulfolobus acidocaldarius 中分离出的极性脂类 E（PLFE）仅含有双极四醚脂类，这些脂类能够形成对许多化学、物理和机械胁迫具有极强稳定性的囊泡膜。因此，PLFE 脂质体已被认为是有吸引力的生物材料，在药物输送和生物传感等生物技术应用中具有很大的应用前景。在这里，我们证明 PLFE 还可以在嵌入印刷电路板（PCB）基微流控装置中的聚二甲基硅氧烷（PDMS）薄膜的微孔（约 100 μm）上形成独立的“平面”膜。为了构建该装置，我们采用了两种新方法：（i）采用 S1813 牺牲层来促进 PDMS 薄膜的制造，以及（ii）利用氧等离子体处理方便地将 PDMS 薄膜与 PCB 板和 PDMS 微流控室结合。通过电化学阻抗谱，我们发现悬浮在 PDMS 薄膜上的 PLFE 平面膜的介电特性明显不同于从二酯脂和三嵌段共聚物膜中获得的特性。除了所有测试的膜中常见的电阻（R）和电容（C）之外，PLFE 平面膜还显示出电感（L）成分。此外，PLFE 平面膜表现出相对较大的膜电阻，这表明在所测试的膜中，PLFE 平面膜将是研究通道蛋白和跨膜事件的更好基质。PLFE 平面膜的相位角也随着输入交流信号频率在约 1 MHz 处急剧下降，这可用于开发监测微流控中 PLFE 膜完整性的传感器。由于独立平面脂质膜的稳定性随膜包装紧密性的增加而增加，并且 PLFE 脂质膜比二酯脂制成的膜包装更紧密，因此预计 PLFE 独立平面膜将相当稳定。所有这些显著特征使 PLFE 平面膜特别适合于通道蛋白和跨膜事件的模型研究，以及高通量药物筛选和人工光合作用。这项工作可以扩展到微流控中 PDMS 薄膜的纳米孔，并最终有助于基于膜的新芯片实验室应用。
