Senior graduate researcher Sean Sullivan has studied the use of polymer microneedles as a delivery system in the Prausnitz lab for five years. “Really, there are three types of microneedles,” he says. “The most prominent is made of solid metal (titanium or stainless steel). One method to using this kind is to coat the needles with a drug, and the ingredients come off in the skin. The holes in your skin heal within an hour, but with this method, there’s a limited amount of a drug dosage that can be delivered, because the drug is actually on the microneedles. The second method is to puncture the skin with the microneedles, take them out and then place a patch with a cream [a protective dressing] containing a drug dosage over the holes to be absorbed by the skin. To close up, the holes need air, so the patch prevents this from occurring right away. This is probably the best option for skin care.”
Sullivan says the second type of microneedles, ones with hollow tubes, allow for controlled delivery of larger drug dosages, and the third type, polymer microneedles, (which Sullivan works on at Georgia Tech), encapsulate drug dosages within the polymers themselves, which dissolve once inside the skin to release the drug into the body. “I like to compare polymer microneedles to the process of making flavored ice cubes,” Sullivan says. “The water you pour into a tray that eventually freezes is like the polymer. The flavoring you pour into the water is like the drug. Eventually, the ice dissolves, delivering the flavor/ingredient.”
Currently, researchers including Sullivan’s instructor, Prausnitz, and Richard Compans, principal investigator for the newly founded Emory University/University of Georgia Influenza Pathogenesis & Immunology Research Center, are leading a U.S. team to find new ways to deliver the flu vaccine using microneedles. They received grants from the National Institutes of Health for millions of dollars to develop a transdermal patch of microneedles containing the vaccine. They hope to design patches that lower the cost of mass immunization, lessen discomfort and allow for long-term storage. European scientists have followed suit.
In February 2008, French company Sanofi Pasteur, the vaccines division of Sanofi-Aventis Group, submitted a proposal to the European Medicines Agency to deliver the first influenza vaccine using microneedles, developed by New Jersey’s Becton, Dickinson and Company. The technology is still under review.
In addition to delivering vaccines, some researchers have discussed using microneedles to deliver diabetes medication or help treat osteoporosis through hormone injections. If successful, this research may lead to innovations in the skin care industry, as well, via physicians’ delivery of antiaging actives, for instance, to patients using painless microneedles. “If you look at a nickel sideways, the needles are less than half the length of that,” says Sullivan. “I’ve inserted microneedles into myself and others. They give 10% of the overall sensation of our regular control needles, but they’re not painful. They don’t go deep enough into the skin to reach nerve endings.”
However, Sullivan and pharmacist-by-training Wiechers agree that marketers of such novel delivery systems should be required to change the term used to describe the technology. “At the beginning, researchers thought using the word ‘micro’ would be enough, because it’s the terminology we use in this industry, but when someone hears the word ‘needle,’ they jump back,” says Sullivan. “So what I think will happen is that people will use a different word like ‘microprojection,’ although, that doesn’t tell you directly what it is. It doesn’t say, ‘This is a delivery system.’ ”
Sullivan believes the skin care market will be ripe for such technology once it has been researched further, but currently, he notes that microdermabrasion treatments deliver just about the same treatment. “Microdermabrasion removes the top layer of skin and allows for a dose of active ingredients to be delivered, often in cream form,” he says. “That’s probably a better method for skin care delivery right now.”
However, microneedles for use in mass skin care applications may not be too far off in the future. The Tyndall National Institute already fabricates silicon and polymeric microneedles for use in biomedical applications. Similarly, Israel’s NanoPass produces MicroPyramid microneedles made of hollow silicone crystals for intradermal injections and cosmetic enhancement.
Horst Liebl has paved the way, as well, founding Dermaroller in 1999, a brand selling a roller made of microneedles for home-use on the face, neck and décolleté. According to the company’s Web site (www.dermaroller.de), the device consists of plastic discs of 192 stainless steel microneedles, placed in eight rows. A medical adhesive bonds the device together, and attached to a plastic handle, it looks like a lint roller brush with tiny needles meant to puncture the skin and allow for absorption of the company’s antiaging skin care products. However, Dermaroller is one of the first companies to have delved into microneedle usage for skin care delivery, so side effects and results of such technology have yet to be defined. Further investigation in this area of skin care is yet to be reported.