Sterilization of therapeutic immunoadsorbents with aqueous propylene oxide solution

Propylene oxide (PO), in the form of its aqueous solution, was evaluated as a chemical sterilant for therapeutic immunoadsorbent to be used in on-line plasmapheresis. Generally, PO is characterized as less toxic and less antimicrobial than ethylene oxide. PO was significant sporicidal to B. subtilis at 25 degrees C and 10(6) spores/ml were killed with 1% (V/V) PO solution after storage for 3 weeks when 75% to 80% of PO decomposed; the death-rate conformed to the kinetics of a first-order reaction although PO decomposed rapidly. Thus an apparent D values were estimated to be 13 to 16 days with 0.5% PO solution and 5 to 7 days with 1% PO. An immunoadsorbent consisting of Sepharose 4B immobilizing anti-human IgE antibody was used to study the effect of PO on adsorption characteristics. PO affected the IgE removal of the immunoadsorbents depending on its concentration ranging from 0% to 4%. The IgE-adsorptions were lowered by only 17% and 30% of the intact and glutaraldehyde-treated immunoadsorbents respectively after storage for 3 months in the 2% PO solution at 25 degrees C, and these numbers are considered to be acceptable for a clinical use. A 2% PO solution was chosen based on the results of the shelf life test of immunoadsorbents and the sporicidal test of PO.