Methacrylate Polymer Scaffolding Enhances the Stability of Suspended Lipid Bilayers for Ion Channel Recordings and Biosensor Development

Abstract

Black lipid membranes (BLMs) provide a synthetic environment that facilitates measurement of ion channel activity in diverse analytical platforms. The limited electrical, mechanical and temporal stabilities of BLMs pose a significant challenge to development of highly stable measurement platforms. Here, ethylene glycol dimethacrylate (EGDMA) and butyl methacrylate (BMA) were partitioned into BLMs and photopolymerized to create a cross-linked polymer scaffold in the bilayer lamella that dramatically improved BLM stability. The commercially available methacrylate monomers provide a simple, low cost, and broadly accessible approach for preparing highly stabilized BLMs useful for ion channel analytical platforms. When prepared on silane-modified glass microapertures, the resulting polymer scaffold-stabilized (PSS)-BLMs exhibited significantly improved lifetimes of 23 ± 9 to 40 ± 14 h and > 10-fold increase in mechanical stability, with breakdown potentials > 2000 mV attainable, depending on surface modification and polymer cross-link density. Additionally, the polymer scaffold exerted minimal perturbations to membrane electrical integrity as indicated by mean conductance measurements. When gramicidin A and α-hemolysin were reconstituted into PSS-BLMs, the ion channels retained function comparable to conventional BLMs. This approach is a key advance in the formation of stabilized BLMs and should be amenable to a wide range of receptor and ion channel functionalized platforms.

Enhanced Fluorescent Protein Activity in Polymer Scaffold-Stabilized Phospholipid Nanoshells Using Neutral Redox Initiator Polymerization Conditions

“…The formation of polymer scaffolds and the arrangement inside the bilayer lamella enhance the nanoshell rigidity. 48 Interestingly, a larger increase in the size of phospholipid nanoshells was observed with neutral redox initiator- and thermal initiator-induced polymerization compared to photoinitiator-induced polymerization. The average diameter of unstabilized phospholipid nanoshells was ∼143 ± 3 nm [polydispersity index (PDI) = 0.11], whereas the average diameter of PSS-phospholipid nanoshells was ∼300 ± 15 nm (PDI = 0.25), ∼480 ± 11 nm (PDI = 0.20), and ∼340 ± 12 nm (PDI = 0.15) for photoinitiator-, neutral redox initiator-, and thermal initiator-induced polymerization, respectively.…”

Parallel Recordings of Transmembrane hERG Channel Currents Based on Solvent-Free Lipid Bilayer Microarray

“…This voltage magnitude was significantly higher than that of the breakdown voltage (0.2–0.6 V) reported for BLMs suspended in plastic and Si 3 N 4 septa [ 23 , 46 , 47 ]. In addition, the breakdown voltage of BLMs formed in CPDS-modified glass nano- and micro-pores has been reported to be 0.4–0.8 V [ 20 , 21 , 22 ]. Considering that the surface of the present Si chips was also modified with CPDS, the improved stability to high voltages was probably due to the tapered-edge shape of the micro-aperture.…”

“…In BLM reconstitution systems, free-standing BLMs are commonly suspended in micro-apertures fabricated in plastic films [ 17 , 18 , 19 ], glass pipettes [ 20 , 21 , 22 ], and microstructured silicon nitride (Si 3 N 4 )/silicon (Si) septa [ 15 , 23 , 24 ]. Although decreasing the size of the aperture significantly improves the stability of BLMs, incorporating ion channels into smaller BLMs becomes more difficult [ 18 , 25 ].…”

“…Non-volatile organic solvents have been frequently used to stabilize BLMs [ 1 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. The solvent seals the gap between the nanometer-thick BLMs and aperture walls, and it allows lipid molecules to align in an appropriate orientation.…”

Bioinspired assemblies and plasmonic interfaces for electrochemical biosensing

“…Each of the photopolymerized membranes exhibited significantly higher stability after UV exposure compared to diphytanoyl phosphocholine (DPhPC), extending the lifetime of these structures from hours to days. Methacrylate polymer precursors may be partitioned into DPhPC BLMs to create polymer scaffolds that enhance the stability in a more cost effective and accessible manner [81]. Surface energy of the hydrophobic support also has an impact on the electrical, mechanical, and stability properties, and can be altered through use of different hydrophobic monolayer coatings [82].…”