1.D.128. The Pore-supported Lipid Membrane (PsLM) Family
Several artificial porous membrane supports have been described. One of these involves lipid bilayers supported on teflon filters which provide a functional environment for protein ion channels (Phung et al. 2011). Many ion channel proteins have binding sites for toxins and pharmaceutical drugs and therefore have much promise as the sensing entity in high throughput technologies and biosensor devices., yet measurement of ionic conductance changes through ion channels requires a robust biological membrane with sufficient longevity for practical applications. The conventional planar BLM is 100-300 μm in diameter and typically contains fewer than a dozen channels whereas pharmaceutical screening methods in cells use current recordings for many ion channels. Phung et al. 2011 presented a method for the fabrication of a disposable porous-supported bilayer lipid membrane (BLM) ion channel biosensor using hydrated Teflon (polytetrafluoroethylene, PTFE) filter material (pore size 5 μm, filter diameter=1 mm). The lipid layer is monitored for its thickness and mechanical stability by electrical impedance spectroscopy. The results showed membrane capacitances of 1.8±0.2 nF and membrane resistances of 25.9±4.1 GΩ, indicating the formation of lipid bilayers. The current level increased upon addition of the pore-forming peptide gramicidin. Following addition of liposomes containing voltage-gated sodium channels, small macroscopic sodium currents (1-80 pA) could be recorded. By preloading the porous Teflon with sodium channel proteoliposomes, prior to BLM formation, currents of 1-10 nA could be recorded in the presence of the activator veratridine that increased with time, and were inhibited by tetrodotoxin. A lack of rectification suggests that the channels incorporated in both orientations. This work demonstrates that PTFE filters can support BLMs that provide an environment in which ion channels can maintain their functional activity relevant for applications in drug discovery, toxin detection, and odour sensing (Phung et al. 2011). hERG channel pharmacology was studied using such a system (Zhang et al. 2012).
Porous-supported lipid membranes (pSLM) provide flexible platforms for studying the surface chemistry of the cell due to their high stability and fluidity, and their ability to study the transmembrane process of the molecules. Sun et al. 2020 reviewed PsLMs and divided them into three types according to the way of the porous materials support the lipid membrane,. These types (1) contain the lipid membrane on the pores of the porous materials, (2) have the lipid membrane on both sides of the porous material, and (3) have the lipid membrane in the pores of the porous materials. All of these pSLMs were reviewed and systematically elaborated from several aspects, including the substrates, formation, and characterization. Meanwhile, the advantages and disadvantages of each model membranes were summarized. Finally, suggestions for selecting appropriate pSLM and future directions in this area are discussed (Sun et al. 2020).