Jet injection through microneedles for large volume subcutaneous delivery

Subcutaneous (SC) drug delivery offers several advantages over intravenous (IV) delivery including: self-administration, improved patient experience, and reduced treatment costs. Unfortunately, each SC delivery is currently limited to ∼ 2.25 mL with IV administration required when the delivery volume exceeds this value. In this work, we explore a new technique for large volume subcutaneous drug delivery that uses microneedles to break through the epidermis then forms the liquid drug into many small jets that penetrate past the ends of the microneedles and into the subcutaneous (or muscle) tissue. By performing multiple simultaneous injections, this delivery approach avoids the volume limitations of SC delivery, and thus may be able to greatly increase the volume we can deliver to this space. Here, we present a novel multi-jet prototype that forms seven simultaneous jets through 30G needles that have been shortened to have an exposed length of just ∼ 1 mm. The jet speed, shape, and volume of jets formed through these microneedles are measured to assess the consistency of jet production through the microneedles. We then perform jet injections of volumes up to 3.9 mL into ex vivo porcine tissue. The results demonstrate the successful delivery (>95 %) of 3.9 mL in just 0.3 s using jet injection performed through microneedles. This volume is almost double the maximum volume of current autoinjectors and the perceived limit for subcutaneous injection (2.25 mL). We also find that jet speeds of 70 m/s and below do not achieve complete delivery of 3.9 mL with our prototype system, and that the addition of microneedles leads to more consistent large volume delivery than equivalent needle-free injections. These results demonstrate the promise of multi-jet injection through microneedles to accommodate volumes much greater than current autoinjectors, and thus potentially allow patient self-administration in many more delivery applications.