Bioactivity of electric field‐pulsed human recombinant interleukin‐2 and its encapsulation into erythrocyte carriers

Abstract

The molecular integrity of human recombinant interleukin‐2 (rIL‐2), as measured by size exclusion chromatography, was not altered when exposed to high electrical field intensities. In addition, the biological activity was unaffected, as evidenced by the ability of the rIL‐2 to stimulate the proliferation (by cell growth assays and tritiated thymidine uptake) and differentiation (by cytotoxicity assay) of human lymphocytes into killer cells. Electroporation conditions chosen for the loading of rIL‐2, based upon those which provided for good recovery of carriers and minimal hemoglobin release, involved a lower field intensity (i.e., 6 kV/cm instead of 7 or 8 kV/cm) and multiple pulses (eight pulses, 5 microseconds) rather than a single pulse (40 microseconds). Human erythrocyte carriers consistently encapsulated 5–7.5% of the rIL‐2 by electroporation (6 kV/cm, eight pulses, 5 microseconds duration). A rIL‐2 concentration of 600,000 U/ml surrounding the erythrocytes during loading resulted in ca. 245,000 U/ml carriers, which represents a therapeutically significant quantity. Thus, rIL‐2 shows potential as an encapsulated agent for slow release in the erythrocyte carrier system.