EVALUATION OF PLASMA RESISTANT COATINGS FOR HOLLOW FIBER MEMBRANES

Abstract

Artificial lungs use porous hollow fiber membranes (HIM) to oxygenate blood and remove carbon dioxide. In blood, HFMs undergo plasma wetting or leakage, whereby plasma enters the fiber pores and reduces gas exchange. This is a critical concern for implantable artificial lungs. We are currently evaluating several HFM coatings for improving fiber plasma resistance, while maintaining acceptable gas transmission levels for oxygen and carbon dioxide. Candidate coated HFMs are evaluated for gas permeance and plasma resistance. Gas permeance is assessed in a gas-gas test in which fibers are externally pressurized with test gas (O2, and CO2) and the rate of gas permeation through the pores into the fiber lumen is measured. Plasma resistance is assessed using a surfactant/dye solution of isopropyl alcohol and DI water (1:1). The solution is run on the outside of the HFMs and the rate of dye bleed through the pores of the fiber membrane is monitored. Scanning electron microscopy (SEMI is used to visualize and compare the coated fiber surfaces. Preliminary results for a siloxane-based plasma polymerized coating showed CO2 gas permeances of 4.8e−4to 1.3e−3ml/s/cm2/cmHg and O2 permeances of 1.2e−4to 5.9e−4. Dye bleed through (5e-3g/L/m2dye) in plasma resistance tests for these fibers were 3 orders of magnitude less than positive control fibers (5 g/L/m2dye). The development of an effective plasma resistant coating involves balancing adequate plasma resistance against gas permeance and may be facilitated with better assays of plasma resistance.