The effect of gamma irradiation on PLGA/PEG microspheres containing ovalbumin

Poly(ethylene glycol) (PEG) and sodium chloride (NaCl) are excipients used in PLGA microsphere preparation to stabilize
proteins and reduce their burst release. No information is till now available in the literature on the effect due to the use of such
excipients on the biopharmaceutical performance of g-irradiated microparticulate systems. On this purpose, different batches of
microspheres containing ovalbumin (OVA) were prepared by using a PLGA 50:50 (average Mr: 13000), different amounts of
PEG (Mr: 400 or 4000) and/or sodium chloride. The non-irradiated and irradiated microspheres were characterized in terms of
morphology (SEM, particle size distribution), OVA and PEG content and in vitro OVA release. Radiolysis mechanisms of OVA
and OVA loaded microspheres were investigated by EPR analysis.
Gamma irradiation affects either microsphere morphology or the release of OVA as a function of the amount of PEG, and the
use of NaCl. Irradiation significantly reduces release rate of protein from the microspheres containing 15% and 30% of PEG and
from controls (microspheres without additives), while no significative effect on protein release rate is highlighted on microspheres
containing lower amounts of PEG. EPR investigation shows that increasing amounts of PEG up to 30% have a
perturbation effect on OVA radiolysis path.