Development and assessment of mini projectiles as drug carriers

This paper describes a novel technology for the delivery of drugs into the subcutaneous and intramuscular tissue of farmed animals. The technology comprises small, hollow mini projectiles into which drug formulations can be loaded and administered using compressed air from an administration device which is held a few millimeters (3-10 mm) from the surface of the animals' skin. The design of the mini projectiles and administration procedure allows administration without contacting the skin, thereby avoiding cross-contamination between handlings and ensuring safe injection practice in livestock. In vitro experiments are described which investigate the parameters that affect mini projectile penetration into excised porcine and bovine skin. These include shape and weight of the mini projectiles and species type and injection site of the animal. An in vitro skin model for assessing mini projectile administration is described which permits visualization of the penetration of the mini projectiles through excised bovine or porcine skin into an underlying tissue simulant made from gelatin. The quantities of energy necessary to inject mini projectiles through excised porcine and bovine skin into the tissue simulant of the in vitro skin model were determined. The paper also describes the processes that occur during the administration of mini projectiles. The results suggest that tissue damage caused during administration of mini projectiles is comparable to the tissue damage caused by conventional syringe-needle injections. Finally, three different formulations of the model vaccine BSA, without adjuvant, are loaded into mini projectiles and administered to pigs. A seroconversion was shown for all three formulations, thus demonstrating proof of concept for the miniprojectiles.