Study of the inactivation process of the tetanus toxoid in contact with poly(lactic glycolic acid) degrading microspheres

This paper investigates the major causes of inactivation of tetanus toroid in the presence of poly:(lactic/glycolic acid) degrading microspheres, and shows strategies for overcoming this inactivation process. The stability of the tetanus toroid in contact with poly(lactic/glycolic acid)polymers was evaluated by incubating the vaccine in a suspension of blank microspheres m ade of various types of poly(lactic/glycolic acid) copolymers at 37 degrees C. Results indicated that the inactivation of the toxoid was due in part t o its interaction with poly (lactic/glycolic acid) and its degradation prod ucts. It was also found that the toroid precipitated because of the decreas e in the pH as a consequence of polymer degradation. The extent of the inac tivation process was dependent opt both the molecular weight and hydrophili city of the polymer. Finally, the evaluation of the effect of several stabi lizing agents which were incorporated into the incubation medium demonstrat ed their ability to block the interaction between tetanus toxoid and poly(l actic/glycolic acid) polymers. Among the stabilizing agents, gelatin A show ed excellent properties to stabilize tetanus vaccine.