Delivering drugs directly to the skin has long been a goal of dermatology, but the stratum corneum — the skin's outermost layer — acts as a stubborn barrier that blocks most topically applied medications. Patients with conditions like psoriasis, eczema, and vitiligo that spread over large skin areas are often forced to take drugs orally or by injection, exposing the entire body to side effects.
Researchers at the Georgia Institute of Technology, led by Mark Prausnitz, have now developed biodegradable STAR particles that overcome this barrier. STAR stands for "skin-targeting abrasive rosette" — microscopic star-shaped polymer particles with sharp microneedle tips that painlessly puncture the skin when rubbed on as a gel or cream.
How STAR Particles Work
The team fabricated STAR particles from three biodegradable polymers: water-soluble poly(vinyl alcohol) (PVA), enzyme-degradable cellulose acetate (CA), and hydrolysable polylactic acid (PLA). Using femtosecond laser micromachining, they carved star-shaped structures with tapered profiles and well-defined microneedle tips.
When rubbed onto pig skin samples for just 10 to 30 seconds, the particles created micropores in the stratum corneum, dramatically increasing drug absorption:
- Tacrolimus (for inflammatory skin conditions): delivery increased 1.7× after 10 seconds and 3.2× after 30 seconds using PVA particles. - Methotrexate (for psoriasis, normally undeliverable topically): delivery jumped 5.4× after 10 seconds and 25.2× after 30 seconds using CA particles. - Copper tripeptide-1 (anti-aging and wound healing): delivery soared 12.1× after 10 seconds and 37× after 30 seconds using PLA particles.
From Lab to Clinic
The biodegradable design addresses environmental and safety concerns raised by the team's earlier work with ceramic titania STAR particles. PVA particles dissolve on contact with wet tissues, eliminating any risk of microneedles entering the bloodstream. CA and PLA particles eventually degrade through enzymatic action or hydrolysis.
Prausnitz says the technology has been licensed to a company preparing for clinical trials next year, using STAR particles to deliver siRNA as a novel eczema treatment. "Very few drugs can be absorbed effectively into the skin," he explains. "STAR particles painlessly make micropores in the skin that allow drug to be absorbed exactly where it is needed."
The research, published in Advanced Healthcare Materials, was supported by the National Science Foundation. Georgia Tech is focused on advanced materials, manufacturing, and formulations for the next generation of STAR particles.
