Cosmetics & Toiletries

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Electrifying Skin Delivery

By: Katie Schaefer, Cosmetics & Toiletries
Posted: November 1, 2010, from the November 2010 issue of Cosmetics & Toiletries.

Iontophoresis is a well-known, noninvasive method that uses a small electric charge to deliver chemicals through the skin. However, according to Gregory Schultz, PhD, and Daniel Gibson, a professor and doctoral candidate, respectively, at the University of Florida, this method of delivery can have its drawbacks. Together with co-inventor, Sonal Sanjeev Tuli, MD, the team developed a method to iontophorese macromolecules into tissue such as the skin without causing damage; however, initial research focused on the eye.

Optimizing Delivery

Initial iontophoresis research began with the eye for a number of reasons. “We studied this delivery method on the cornea because not only is it a significant barrier, but also because the techniques used to deliver drugs into the skin, such as creams, penetrants and dimethyl sulfoxide, are toxic to the cornea,” noted Gibson.

The team began with the delivery of oligonucleotide-based drugs such as antisense oligonucleotides (ASOs) into the cornea. These DNA/RNA-based drugs serve as biomolecules to drive therapeutics in a targeted approach. “While we initially started with topical delivery, we found it was not getting into the cornea at all,” said Gibson.

Schultz agreed, “The passive diffusion methods for delivering these larger molecules was not delivering therapeutic amounts of the drugs.” Gibson likened the delivery of these macromolecules (1,000 g/mole) into the cornea to passing a tennis ball through a chain-link fence covered in Velcroa; the size is too large and the molecules adhere to the matrix or cells through normal biological reactions.

Schultz added that the affinity of macromolecules to water or lipids affects delivery. “Molecules that are applied topically and penetrate the skin well have a large hydrophobic component; but many drugs are hydrophilic, so they do not get across the lipid barrier of the stratum corneum,” he said.

Buffering Delivery