Bilewicz Renata, Rowiński Paweł, Rogalska Ewa
Department of Chemistry, University of Warsaw, Pasteura 1, Warsaw 02-093, Poland.
Bioelectrochemistry. 2005 Apr;66(1-2):3-8. doi: 10.1016/j.bioelechem.2004.02.005.
The lipidic cubic phase can be characterized as a curved bilayer forming a three-dimensional, crystallographical, well-ordered structure that is interwoven by aqueous channels. It provides a stable, well-organized environment in which diffusion of both water-soluble and lipid-soluble compounds can take place. Cubic phases based on monoacylglycerols form readily and attract our interest due to their ability to incorporate and stabilize proteins. Their lyotropic and thermotropic phase behaviour has been thoroughly investigated. At hydration over 20%, lipidic cubic phases Ia3d and Pn3m are formed. The latter is stable in the presence of excess water, which is important when the cubic phase is considered as an electrode-modifying material. Due to high viscosity, the cubic phases can be simply smeared over solid substrates such as electrodes and used to host enzymes and synthetic catalysts, leading to new types of catalytically active modified electrodes as shown for the determination of cholesterol, CO(2), or oxygen. The efficiency of transport of small hydrophilic molecules within the film can be determined by voltametry using two types of electrodes: a normal-size electrode working in the linear diffusion regime, and an ultramicroelectrode working under spherical diffusion conditions. This allows determining both the concentration and diffusion coefficient of the electrochemically active probe in the cubic phase. The monoolein-based cubic phase matrices are useful for immobilizing enzymes on the electrode surface (e.g., laccases from Trametes sp. and Rhus vernicifera were employed for monitoring dioxygen). The electronic contact between the electrode and the enzyme was maintained using suitable electroactive probes.
脂质立方相可被描述为一种弯曲的双层结构，形成三维晶体学有序结构，该结构由水通道交织而成。它提供了一个稳定、有序的环境，水溶性和脂溶性化合物均可在其中扩散。基于单酰甘油的立方相易于形成，因其能够结合并稳定蛋白质而引起我们的兴趣。它们的溶致和热致相行为已得到深入研究。当水合度超过20%时，会形成脂质立方相Ia3d和Pn3m。后者在过量水存在下是稳定的，当将立方相视为电极修饰材料时这一点很重要。由于高粘度，立方相可简单地涂抹在诸如电极等固体基质上，并用于容纳酶和合成催化剂，从而产生新型的催化活性修饰电极，如用于测定胆固醇、二氧化碳或氧气的电极。薄膜内小的亲水分子的传输效率可通过伏安法使用两种类型的电极来测定：一种是在线性扩散区域工作的常规尺寸电极，另一种是在球形扩散条件下工作的超微电极。这使得能够确定电化学活性探针在立方相中的浓度和扩散系数。基于单油酸甘油酯的立方相基质可用于将酶固定在电极表面（例如，来自栓菌属和漆树的漆酶被用于监测双氧）。使用合适的电活性探针维持电极与酶之间的电子接触。
