Microfabricated needles for transdermal delivery of macromolecules and nanoparticles: Fabrication methods and transport studies

TLDR

Arrays of micrometer‑scale needles can deliver drugs, proteins, and particles across skin in a minimally invasive manner. The study aims to develop microfabrication techniques for silicon, metal, and biodegradable polymer microneedle arrays with solid and hollow bores, tapered and beveled tips, and feature sizes from 1 to 1,000 µm. The authors fabricated these arrays using microfabrication methods tailored to each material, producing solid and hollow structures with precise tip geometries. Solid microneedles increased skin permeability in vitro by orders of magnitude for macromolecules and particles up to 50 nm radius, enabled efficient intracellular delivery into viable cells, and hollow microneedles allowed microliter injections in vivo, such as insulin microinjection that lowered blood glucose in diabetic rats.

Abstract

Arrays of micrometer-scale needles could be used to deliver drugs, proteins, and particles across skin in a minimally invasive manner. We therefore developed microfabrication techniques for silicon, metal, and biodegradable polymer microneedle arrays having solid and hollow bores with tapered and beveled tips and feature sizes from 1 to 1,000 μm. When solid microneedles were used, skin permeability was increased in vitro by orders of magnitude for macromolecules and particles up to 50 nm in radius. Intracellular delivery of molecules into viable cells was also achieved with high efficiency. Hollow microneedles permitted flow of microliter quantities into skin in vivo , including microinjection of insulin to reduce blood glucose levels in diabetic rats.