Micro-BLMs on Highly Ordered Porous Silicon Substrates:  Rupture Process and Lateral Mobility

Abstract

In a recent paper, we hypothesized that the continuous increase in membrane conductance observed for nano-BLMs is the result of an independent rupturing of single membranes or membrane patches covering the pores of the porous material. To prove this hypothesis, we prepared micro-BLMs on porous silicon substrates with a pore size of 7 mum. The upper surface of the silicon substrate was coated with a gold layer, followed by the chemisorption of 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE) and subsequent addition of a droplet of 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) dissolved in n-decane. The lipid membranes were fluorescently labeled and investigated by means of fluorescence microscopy and impedance spectroscopy. Impedance spectroscopy revealed the formation of pore-suspending bilayers with high membrane resistance. Increases in membrane capacitance and membrane conductance were observed. This increase in membrane conductance could be unambiguously related to the individual rupturing of membranes suspending the pores of the porous material as visualized by means of fluorescence microscopy. Moreover, by fluorescence recovery after photobleaching experiments, we investigated the lateral mobility of the lipids within the micro-BLMs leading to a mean effective diffusion coefficient of Deff = (14 +/- 1) microm2/s.

Ultrathin and nanostructured ZnO-based films for fluorescence biosensing applications

“…These findings indicate that, apart from the obvious enhanced friction suffered by the molecules moving inside the pore rims of the patterned ZnO-2 film in comparison with the unpatterned sample (i.e., topographic effect), the presence of SiO 2 areas confined by the ZnO is relevant to trigger the protein mobility at the biointerface (i.e., chemical effect). Similar results, pointing to a friction-reduced lateral diffusion on pore rims compared with that of the area within the pore, have been reported for lipid membranes on ordered porous silicon substrates [42]. In our case, the protein diffusion rate on the hybrid ZnO-SiO 2 surface is likely be affected not only by the topography by also by the surface chemistry and charge.…”

Creating and Modulating Microdomains in Pore‐Spanning Membranes

“…In our case, the situation is even more complicated as the lipids on the CPEO3-monolayer experience larger friction due to a strong coupling compared to those in the freestanding region, which is expected to slow down the lateral lipid diffusion. [18] From the low immobile fraction of (11 AE 6) % it can be concluded that the CPEO3 monolayer is incomplete and contains non-immobilized lipids after formation of the pore-spanning membrane. If the CPEO3-monolayer completely prevented the bottom lipid monolayer to diffuse, an immobile fraction of about 50 % would be expected.…”

Lipid-nanostructure hybrids and their applications in nanobiotechnology

“…The mechanical decoupling between neighboring holes via the chemically immobilized lower leaflet of the bilayer on the rim of a hole causes the individual rupturing of the suspended bilayer, providing a longer lifetime for the devices than the classical black lipid membrane, which loses its entire function in a single rupture event. 54 As the need for the development of more sophisticated ionchannel-based biosensing and high-throughput drug screening systems increases, a number of efforts have been aimed at achieving a GO seal between two aqueous compartments separated by lipid bilayers and improving their lifetimes to several days. The high membrane resistance required for a single ion channel measurement was attained by the formation of a lipid bilayer on a gold-coated porous alumina substrate with a surface was functionalized with 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol.…”