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Micropore closure time is longer following microneedle application to skin of color
Abayomi T Ogunjimi1, Jamie Carr1, Christine Lawson1
1Division of Pharmaceutics and Translational Therapeutics, Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa College of Pharmacy, 180 South Grand Avenue, 552 CPB, Iowa City, IA, 52242-1112, USA.
Abstract:
Microneedles (MNs) allow transdermal delivery of skin-impermeable drugs by creating transient epidermal micropores, and micropore lifetime directly affects drug diffusion timeframes. Healthy subjects (n = 111) completed the study, self-identifying as Asian (n = 32), Bi-/multi-racial (n = 10), Black (n = 22), White (n = 23), Latino (n = 23), and Native American/Hawaiian (n = 1). L* was measured with tristimulus colorimetry to objectively describe skin lightness/darkness. MNs were applied to the upper arm; impedance and transepidermal water loss (TEWL) were measured at baseline and post-MN to confirm micropore formation. Impedance was repeated for 4 days to determine micropore lifetime. Post-MN changes in TEWL and impedance were significant in all groups (p < 0.05), confirming micropore formation regardless of skin type. Micropore lifetime was significantly longer in Blacks (66.5 ± 19.5 h) versus Asians (44.1 ± 14.0 h), Bi-/multi-racial (48.0 ± 16.0 h), and Whites (50.2 ± 2.6 h). Latinos (61.1 ± 16.1 h) had significantly longer micropore closure time versus Asians (44.1 ± 14.0 h). When categorizing data according to L*, micropore lifetime was significantly longer in darker skin. We report for the first time that micropore lifetime differences are present in human subjects of different ethnic/racial backgrounds, with longer micropore lifetime in skin of color. These results also suggest that objectively measured skin color is a better predictor of micropore lifetime than self-identified race/ethnicity.
Insights
Microneedle (MN) micropore lifetime, crucial for drug delivery, varies significantly across different skin types. Darker skin tones exhibit a longer micropore duration, suggesting personalized transdermal delivery strategies are needed.
Area of Science:
- Dermatology
- Pharmaceutics
- Biomedical Engineering
Background:
- Microneedles (MNs) facilitate transdermal drug delivery by creating temporary skin micropores.
- The duration these micropores remain open (micropore lifetime) directly impacts drug diffusion and delivery efficiency.
- Understanding factors influencing micropore lifetime is essential for optimizing MN-based therapies.
Purpose of the Study:
- To investigate the influence of ethnic and racial background on microneedle-induced epidermal micropore lifetime.
- To determine if objective measures of skin color correlate with variations in micropore closure time.
- To assess the implications of these findings for transdermal drug delivery efficacy across diverse populations.
Main Methods:
- 111 healthy subjects representing diverse ethnic/racial groups self-identified their background.
- Skin lightness (L*) was objectively measured using tristimulus colorimetry.
- Microneedles were applied to the upper arm, and skin impedance and transepidermal water loss (TEWL) were measured to confirm and track micropore formation and closure over 4 days.
Main Results:
- Micropore formation was confirmed across all skin types, indicated by significant changes in TEWL and impedance post-MN application (p < 0.05).
- Micropore lifetime was significantly longer in Black subjects (66.5 ± 19.5 h) compared to Asian (44.1 ± 14.0 h), Bi-/multi-racial (48.0 ± 16.0 h), and White subjects (50.2 ± 2.6 h).
- Latino subjects (61.1 ± 16.1 h) also showed a significantly longer micropore lifetime than Asian subjects.
- Objective skin color measurement (L*) revealed a significant correlation, with darker skin tones exhibiting longer micropore lifetimes.
Conclusions:
- Micropore lifetime varies significantly among individuals of different ethnic and racial backgrounds.
- Skin of color demonstrates a longer duration of microneedle-induced micropores compared to lighter skin tones.
- Objectively measured skin color is a more precise predictor of micropore lifetime than self-identified race/ethnicity, with implications for tailoring transdermal drug delivery systems.
