Micropore closure time is longer following microneedle application to skin of color

Abayomi T Ogunjimi,Jamie Carr,Christine Lawson,Nkanyezi Ferguson,Nicole K Brogden

doi:10.1038/s41598-020-75246-8

Abayomi T Ogunjimi, Jamie Carr + Show 3 more

Open Access

https://doi.org/10.1038/s41598-020-75246-8

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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.

Highlights

Microneedles (MNs) allow transdermal delivery of skin-impermeable drugs by creating transient epidermal micropores, and micropore lifetime directly affects drug diffusion timeframes
The idea that differing skin properties may affect micropore closure timeframes is supported by previous studies that demonstrated slower micropore closure times in elderly vs. young healthy subjects, which could be a result of the decreased elasticity and stratum corneum hydration typically found in aging s kin[15]
It is clear that emerging MN therapeutics need to be suitable and safe for broad populations of patients, which makes it critical that we understand how different ethnic/racial skin types respond to MN treatment

Summary

Introduction

Microneedles (MNs) allow transdermal delivery of skin-impermeable drugs by creating transient epidermal micropores, and micropore lifetime directly affects drug diffusion timeframes. Differences in barrier and structural skin properties have been reported amongst human subjects of different ethnic/racial backgrounds, including stratum corneum cohesion and strength, transepidermal water loss (TEWL), skin elasticity, epidermal and dermal thickness, and ceramide c ontent[1,2,3,4]. The effect of these properties on the extent and variability of dermal absorption remains under debate with conflicting results reported in the literature, and this is an area in need of more study. Tailored drug formulations and application schedules may be necessary for successful therapeutic outcomes with MN-assisted drug delivery in diverse patient populations, and this could have significant implications in guiding product development strategies

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