Investigation Of Needle-free Injector In Vitro And In Vivo

Jet injection is a needle-free drug delivery system which employs a high-speed stream of fluid that impacts the skin and delivers drugs intradermally, subcutaneously, or intramuscularly without the use of a needle. Compared with the traditional medicine injection, it has represented its more attractive characteristics, such as painless injection, high medicine absorption rate, no cross infection and easy to operate etc. In the applications, it adapts especially to the patients who are afraid of injectors, who need to treat themselves for a long time. It is also applicable for preventing and treating the diseases occurring massively or in field. So a number of jet injection are available, especially for polypeptide and protein drugs, mass immunization and anesthetics delivery.A transdermal delivery gun was invented with the help of Machinery Institute in Huazhong University of Science and Technology. In this paper, a needle-free injector based on the power of high strength spring was proposed, and a prototype was developed to do some experiments in vitro and in vivo for further research.First, based on the testing system, the experiments of the trigger force and the characteristic of liquid jet on the Injex needle-free injector and self-designed needle-free injector were carried out. The experiments indicated that the trigger force ,jet impact force and jet velocity would increase with the increase of spring rigidity and would decrease with the increase of drug dose.Secondly, according to ISO 21649, the confidence level of dose was evaluated. The experiments indicated that the confidence level would decrease with the increase of spring rigidity of self-designed needle-free injector. However, there would be a 99.9% confidence of all three doses with Injex needle-free injector.Thirdly, Agarose gel, as a model, was developed to predict the hole depth as a function of jut and skin properties. Motion analysis of jet entry into Agarose gels revealed that jet penetration can be divided into three distinct events: erosion, stagnation, and dispersion. The hole depth and maximum dispersion width would increase with the increases of spring rigidity and jet volume.Last, porcine skin was used as a model with a high predictive value for the feasibility in humans because of its close similarity to human skin, in order to test the biological performance of needle-free injectors. The epidermeis was entirely intact and the subcutaneous fat tissue did not show any obvious lesions by the use of the Injex needle-free injector and self-designed needle-free injector with the spring stiffness coefficient 4500 N/m. However, there were obvious lesions in the muscle facia by the use of the self-designed needle-free injector with the spring stiffness coefficient 7200 N/m, and obvious lesions in the dermis by the use of needle.