POROUS POLYMER MEMBRANES AS SUPPORTING SCAFFOLDS FOR BILAYER UPID MEMBRANES (BLM)
The outer limiting boundary of a cell, the cell membrane, is a bilayered lipid membrane and it gives the cell control over its internal environment. A realistic in vitro model of the cell membrane can help gain invaluable information about fundamental life processes. A self-assembled bilayer lipid membrane (BLM) made from phospholipids resembles the cell membrane in structure and function and can be used as a model. However, the mechanical and electrical instability of the BLM poses a major problem to its wide experimental study. The purpose of this work was to study and develop flexible and porous polymer membranes to act as supporting scaffolds for bilayer lipid membranes (BLM). Commercially available polycarbonate filters and laboratory synthesized porous poly (l-lactic acid) (PLLA) membranes were examined for the application. Lipid structure and BLM stability was determined by ion flow measurements. Ion flow measurements showed that deposition of phospholipids on a porous membrane resulted in a 3 orders of magnitude increase in its ion flow resistance. This increase in ion flow resistance indicated formation of dense ion impermeable structures in the pores of the membranes. On addition of Gramicidin- D, which is an ion channel forming molecule, to the above system, a drastic decrease in ion flow resistance was observed. This suggested formation of Gramicidin-D ion channels within the ion impermeable phospholipid structures. Gramicidin- D can form ion channels only across unit bilayer lipids. Thus, the decreased ion flow resistance pointed towards a stable bilayer structure within the membrane pores. Thus, stabilized BLM’s were formed in the membrane pores with the polymer membrane providing it mechanical stability. In a preliminary study utilizing another kind of an ion channel, Kv1.5 potassium ion channels were successfully reconstituted within BLM’s supported by PLLA membranes. These studies have led to the conclusion that membranes with pore sizes of 3-10µ with an aspect ratio nearing 3 are good scaffolds for BLM stabilization. Also, better pore structure uniformity aids BLM formation and stabilization.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:bilayer lipid membranes polymers poly l lactic acid
Date of Publication:01/01/2005