Abstract
Transdermal delivery can be accomplished through various mechanisms including formulation optimization, epidermal stratum corneum barrier disruption, or directly by removing the stratum corneum layer. Microneedling, electroporation, a combination of both and also the intradermal injection known as mesotherapy have proved efficacy in epidermal-barrier disruption. Here we analyzed the effects of these methods of epidermal-barrier disruption in the structure of the skin and the absorption of four compounds with different characteristics and properties (ketoprofen, biotin, caffein, and procaine). Swine skin (Pietrain x Durox) was used as a human analogue, both having similar structure and pharmacological release. They were biopsied at different intervals, up to 2 weeks after application. High-pressure liquid chromatography and brightfield microscopy were performed, conducting a biometric analysis and measuring histological structure and vascular status. The performed experiments led to different results in the function of the studied molecules: ketoprofen and biotin had the best concentrations with intradermal injections, while delivery methods for obtaining procaine and caffein maximum concentrations changed on the basis of the lapsed time. The studied techniques did not produce significant histological alterations after their application, except for an observed increase in Langerhans cells and melanocytes after applying electroporation, and an epidermal thinning after using microneedles, with variable results regarding dermal thickness. Although all the studied barrier disruptors can accomplish transdermal delivery, the best disruptor is dependent on the particular molecule.
Highlights
The ease of use of topical presentations has made the skin target of different cosmetic and/or “therapeutic” methods from time immemorial [1]
All these functions require a formidable superficial barrier to be sustained against chemical and physical agents, behaving as an impediment for topical delivery of most substances, small-size lipophilic drugs may still reach therapeutic levels with topical administration, demonstrating that the barrier is selective [2]. It is in turn composed of various barriers working synergistically, including the stratum corneum, epidermal tight junctions, basement membrane, and blood vessel endothelia; these barriers can be found in the epidermis, and in skin adnexa [3]
This lipophilic property is associated with dehydration in the stratum corneum, where water constitutes approximately 15–20% of the total mass, whilst in other living epidermal layers it constitutes as much as 70% [7]
Summary
The ease of use of topical presentations has made the skin target of different cosmetic and/or “therapeutic” methods from time immemorial [1]. Skin represents the biggest organ of the human body, and has several functions regarding touch, defense, and hydration maintenance All these functions require a formidable superficial barrier to be sustained against chemical and physical agents, behaving as an impediment for topical delivery of most substances, small-size lipophilic drugs may still reach therapeutic levels with topical administration, demonstrating that the barrier is selective [2]. It is in turn composed of various barriers working synergistically, including the stratum corneum, epidermal tight junctions, basement membrane, and blood vessel endothelia; these barriers can be found in the epidermis, and in skin adnexa [3]. This lipophilic property is associated with dehydration in the stratum corneum, where water constitutes approximately 15–20% of the total mass, whilst in other living epidermal layers it constitutes as much as 70% [7]
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