Polyethylene Glycol Repairs Damaged Membrane; Biophysical Application of Artificial Planar Bilayer to Mimic Biological Membrane

Polyethylene glycol (PEG) is a hydrophilic polymer, known to be capable to fuse numerous single cells in vitro, to join the membranes of adjacent neurons and giant invertebrate axons, and to seal damaged neural membranes. The molecular mechanism of the action of PEG is still unknown. It is believed that PEG dehydrates membranes and enables their structural components to resolve and rearrange in a lamellar configurationfollowing rehydration. In this study, the effects of different sized PEGs (400, 1000, and 2000Da) at 10–30% w/w on different physical properties of intact and damaged artificial bilayers, including membrane conductivity (G_m), capacitance (C_m), and breakdown voltage (V_b), were studied by voltage clamp technique to address itsresealing capability at the molecular level. The unilamellar artificial planar bilayer was formed from soybean lecithin, based on the Montal and Mueller procedure. Our results show that in disrupted membrane, PEG2000 increased G_m and C_m significantly and decreased V_b. Furthermore, PEG1000 at 30% w/w significantly increased G_m and decreased V_b, but had no effect on C_m. PEG400 had no significant effect on G_m, V_b, or C_m. In addition, at the applied concentrations and molecular weights, the PEGs showed no effects on the stability, conductivity, or breakdown voltage of the intact bilayer. We conclude that PEGs repair membrane in concentration- and size-dependent manner; small PEG (400Da) is capable of repairing membrane and re-stabilizing its integrity at certain concentrations, while larger ones, such as PEG2000, destabilize the membrane and fail to re-establish its integrity. The results of this study might shed light on understanding the mechanism (s) by which PEGs repair damaged membranes of neural fibers, and might be considered in clinical treatment of brain and spinal cord injury in the near future.