Racial/Ethnic Differences in Microneedle Response

Transdermal drug delivery (by way of patches that adhere to the skin and deliver drug in a time-dependent fashion) allows for systemic drug delivery through the skin, while avoiding many of the side effects and challenges associated with oral or intravenous drug delivery. One significant challenge limiting the number of drug compounds that can be transdermally delivered is the hydrophobic nature of the skin, which provides a highly efficient barrier against the absorption of drug molecules. Microneedles are a minimally invasive means of allowing drug molecules to cross the skin by creating micron-sized channels (also called micropores) in the skin, thereby increasing its permeability. Microneedles have been safely used in hundreds of patients for administration of drugs and vaccines through the skin. Studies have demonstrated that microneedle treatment is relatively painless and well-tolerated by most patients.

Following microneedle treatment, the skin must heal the micropores in order to restore barrier function. In young healthy individuals this process takes approximately 48 to 72 hours when the skin is covered by an occlusive patch. The timeframe for micropore closure is longer in elderly individuals (>65 years of age), taking several days longer to restore the skin barrier. As evidenced by the differences in micropore closure rate observed with advancing age, biological variation can have a significant effect on the skin's healing properties. There are almost no data available regarding how race and ethnicity affect skin response to microneedle insertion. It is crucial to better understand how the rates of micropore closure vary in different racial/ethnic populations because the potential for variability in drug delivery is high if the recovery timeframes are poorly understood.

In this study we will measure hydration and color to characterize the epidermal properties of individuals of different self-identified race and ethnicity. Measurements of trans-epidermal water loss and electrical impedance will be used to evaluate the formation of micropores in the skin; the electrical impedance measurements will be used to calculate the rate of micropore closure. All of these skin characteristics can be measured using noninvasive methods that are quick and painless.

Inclusion criteria

• Subjects will be healthy men and women between 18 - 50 years of age who identify as African American or Black, Asian, Hispanic or Latino, American Indian/Alaska Native, Native Hawaiian/Other Pacific Islander, Caucasian/White, bi-/multiracial.

Exclusion criteria

• Unable to give consent
• Severe general allergies requiring chronic treatment with steroids or antihistamines
• Previous adverse reaction to microneedle insertion
• Known allergy or adverse reaction to medical tape, adhesive, or aloe vera
• Anyone with inflammatory diseases of the skin or diseases that alter immune function
• Anyone taking any medications that impair the immune system will be excluded (contraceptives, vitamins, and topical products on the face will be allowed)
• Anyone with current malignancy or history of malignancy present at the treatment site (upper arm)
• Anyone with any of the following present at the treatment site (upper arm): eczema or scaling, inflammation, erythema, edema, blisters
• Anyone with uncontrolled mental illness that would, in the opinion of the physician, affect their ability to understand or reliably participate in the study
• Anyone taking medications in the following therapeutic classes will be excluded: HMGCoA reductase inhibitors ("statins"), oral or topical steroids, oral antibiotics, topical antibiotics at the local treatment site, topical antihistamines at the local treatment site, beta-blockers, and systemic or topical NSAIDS/analgesics
• Anyone who is pregnant or nursing
• Anyone with any condition that would, in the opinion of the PI or physician, place the subject at an unacceptable risk of injury or render the subject unable to meet the requirements of the protocol