In Vivo Reflectance Confocal Microscopy Evaluation of Microneedle Patch Penetration Depth

Firstly, confirm penetration of the skin's most exclusive layer, the stratum corneum (SC), by commercially available microneedle patches using reflectance confocal microscopy (RCM). Secondly, determine the deepest layer of the skin penetrated by the microneedle patches.

In this proof-of-concept study, 3 commercially available dissolving microneedle patches with different active ingredients were included in this study. RCM images of the cheek were taken prior to patch application at 4 different layers of the skin: stratum corneum, stratum spinosum-granulosum, dermal-epidermal junction, and papillary dermis. Patches were then applied to the cheeks of participants according to manufacturer guidelines. Immediately after removal, the same area and layers were imaged using RCM and assessed for features of penetration.

Micropores were visualized in RCM images of skin layers post-application of all patches when compared with imaging before application. Characteristics of penetration included uniformly sized, shaped, and spaced well-defined circular areas, which are the created micropores. All 3 patches penetrated the SC to the level of the papillary dermis.

This study confirms that the dissolving microneedle patches penetrate the most exclusive layer of the skin, the SC, down to the level of the papillary dermis as visualized through RCM. Confirming penetration with RCM shows the potential of these patches to be used for medication transmission. While future studies are needed to assess the efficacy of microneedle patches applied for their advertised skin conditions, confirming the penetration of the microneedle technology through RCM is a significant first step in this process. J Drugs Dermatol. 2023;22(11):1107-1110     doi:10.36849/JDD.6994.