In Vivo Reflectance Confocal Microscopy Evaluation of Microneedle Patch Penetration Depth

Area of Science:

• Dermatology and Biomedical Engineering
• Drug Delivery Systems
• Skin Science

Background:

• Microneedle patches offer a promising avenue for transdermal drug delivery.
• Confirming stratum corneum (SC) penetration is crucial for microneedle efficacy.
• Investigating the depth of penetration is essential for optimizing drug delivery.

Purpose of the Study:

• To confirm stratum corneum (SC) penetration by commercial microneedle patches using reflectance confocal microscopy (RCM).
• To determine the maximum depth of skin penetration achieved by these microneedle patches.

Main Methods:

• Utilized reflectance confocal microscopy (RCM) to image skin layers before and after microneedle patch application.
• Examined four distinct skin layers: stratum corneum, stratum spinosum-granulosum, dermal-epidermal junction, and papillary dermis.
• Assessed three commercially available dissolving microneedle patches on participants' cheeks.

Main Results:

• Reflectance confocal microscopy (RCM) visualized distinct micropores post-microneedle application, confirming SC penetration.
• All tested microneedle patches created uniformly sized and shaped pores.
• Penetration was consistently observed down to the papillary dermis level for all three patch types.

Conclusions:

• Dissolving microneedle patches effectively penetrate the stratum corneum (SC) and reach the papillary dermis, as evidenced by RCM.
• RCM visualization confirms the potential of microneedle patches for medication transmission.
• While efficacy studies are pending, RCM confirmation of penetration is a vital initial step for microneedle technology validation.