Snake fang–inspired stamping patch for transdermal delivery of liquid formulations

A microneedle patch that uses snake fang–inspired multiple open grooves can rapidly deliver liquid-phase drugs and vaccines under capillary action. Bioinspired drug delivery Topical formulations, transdermal patches, and microneedles can be used for drug delivery, avoiding the pain associated with hypodermic needle injections. Bae et al. developed flexible patches using microneedles to rapidly deliver liquid formulations through the skin. Inspired by rear-fanged snakes, the authors fabricated microneedles with open grooves that transdermally delivered dye-labeled proteinaceous solutions, liquid anesthetic, and a vaccine to guinea pigs and mice. Mice showed similar protection against influenza when immunized by microneedle patch or intramuscular injection. This flexible patch platform offers a versatile method of liquid drug delivery. A flexible microneedle patch that can transdermally deliver liquid-phase therapeutics would enable direct use of existing, approved drugs and vaccines, which are mostly in liquid form, without the need for additional drug solidification, efficacy verification, and subsequent approval. Specialized dissolving or coated microneedle patches that deliver reformulated, solidified therapeutics have made considerable advances; however, microneedles that can deliver liquid drugs and vaccines still remain elusive because of technical limitations. Here, we present a snake fang–inspired microneedle patch that can administer existing liquid formulations to patients in an ultrafast manner (<15 s). Rear-fanged snakes have an intriguing molar with a groove on the surface, which enables rapid and efficient infusion of venom or saliva into prey. Liquid delivery is based on surface tension and capillary action. The microneedle patch uses multiple open groove architectures that emulate the grooved fangs of rear-fanged snakes: Similar to snake fangs, the microneedles can rapidly and efficiently deliver diverse liquid-phase drugs and vaccines in seconds under capillary action with only gentle thumb pressure, without requiring a complex pumping system. Hydrodynamic simulations show that the snake fang–inspired open groove architectures enable rapid capillary force–driven delivery of liquid formulations with varied surface tensions and viscosities. We demonstrate that administration of ovalbumin and influenza virus with the snake fang–inspired microneedle patch induces robust antibody production and protective immune response in guinea pigs and mice.