Assessment of the biological performance of the needle-free injector INJEX using the isolated porcine forelimb

Summary Background The development and utilization of novel needle‐free injection devices in order to minimize needle stick injuries make increasing demands for suitable assay systems, which reflect the physiological situation in humans as close as possible. Objectives It was therefore the goal of the present study to test the biological performance of a needle‐free injector (INJEX) by the use of porcine skin as a model with a high predictive value for the feasibility in humans because of its close similarity to human skin. Methods In order to use porcine skin in the context of the underlying tissues, the isolated porcine forelimb was chosen as an assay model for use with the INJEX injector. Ink or the fluorescent dye fluorescein‐isothiocyanate was injected and the penetration depth was determined metrically and dye distribution histologically. To assess the resorption of heparin, needle injection was compared with needle‐free injection in a perfused limb model. Results Increasing amounts of ink increasingly penetrated into subcutaneous tissue layers in a cone‐shaped manner mainly following lead structures. Penetration was hampered by skin thickness and by the deep muscle fascia, which served as a penetration barrier. Resorption of heparin was similar irrespective of injection by the use of a needle or the INJEX device. Conclusions The isolated porcine forelimb serves as a versatile tool for the assessment of the biological performance of needle‐free injection devices such as INJEX. Further studies are necessary to correlate the model for drug delivery in humans.