Fig. 7.

Eudragit E-doped particles show release of stable IPV at 2–3 weeks. By incorporating the basic, acid-soluble EPO into the PLGA-based particles, IPV could be protected from accumulating acid and be released in stable form. Decreasing the EPO concentration from 7.5% (A–C) to 5% (D–F) to 3% (G–I) allowed the kinetics of the second burst to be tuned. Adjusting the pH by adding arginine (J–L) also slowed the second burst of release.