Nanoparticles and microparticles for skin drug delivery

The ‘acid mantle’ of the stratum corneum seems to be important for both permeability barrier formation and cutaneous antimicrobial defense. However, the origin of the acidic pH, measurable on the skin

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The pH of the skin surface and its impact on the barrier function.

Transdermal skin delivery: predictions for humans from in vivo, ex vivo and animal models.

The skin offers an accessible and convenient site for the administration of medications. To this end, the field of transdermal drug delivery, aimed at developing safe and efficacious means of delivering medications across the skin, has in the past and continues to garner much time and investment with the continuous advancement of new and innovative approaches. This review details the progress and current status of the transdermal drug delivery field and describes numerous pharmaceutical developments which have been employed to overcome limitations associated with skin delivery systems. Advantages and disadvantages of the various approaches are detailed, commercially marketed products are highlighted and particular attention is paid to the emerging field of microneedle technologies.

https://www.mdpi.com/1999-4923/7/4/438/pdf

Transdermal Drug Delivery: Innovative Pharmaceutical Developments Based on Disruption of the Barrier Properties of the Stratum Corneum

Lipid nanoparticles for improved topical application of drugs for skin diseases.

Background/purpose: Porcine ear skin is used in studies of percutaneous penetration as a substitute for human skin. The structure of this tissue, including hair follicles, was studied qualitatively and quantitatively in comparison with human skin.

Methods: Sections of shock-frozen biopsies, biopsies embedded in paraffin and cyanoacrylate skin surface biopsies were investigated using microscopy. The thickness of the different skin layers and the follicular characteristics were determined.

Results: The thickness of the stratum corneum was 17–28 μm, whereas the viable epidermis was 60–85 μm thick. On 1 cm2, 11–25 hairs were detected, showing a diameter of 58–97 μm and a maximal extension depth of 0.96–1.38 mm into the skin. The orifices of the porcine infundibula showed a diameter of approximately 200 μm.

Conclusions: The results obtained are similar to those of human skin, indicating the suitability of this porcine tissue as a model for human skin.

Porcine ear skin: an in vitro model for human skin

The tape stripping procedure--evaluation of some critical parameters.

https://www.jidonline.org/article/S0022-202X(15)32389-7/pdf

Differential stripping: determination of the amount of topically applied substances penetrated into the hair follicles.

Background/purpose Topography of the skin surface is a mirror of the functional skin status. Therefore, its evaluation is of great interest for dermatological research. In the present study, a new optical measuring system was applied to evaluate human skin surface topography in vivo and non-invasively, in order to determine elastotic and mimic wrinkles dependent on age, body site and therapy. Methods The measurements were performed on the back (n=5), the flexor forearm (n=14) of volunteers in different age groups and on the face of women (n=4) participating in an anti-wrinkle study. The evaluation of the three-dimensional-profiles was performed determining skin surface parameters (mean roughness (R(a)), mean depth of roughness (R(z)), maximum roughness (R(m)) and waviness (W(t))) and applying Fourier analysis. Results Significant increases in all surface parameters were obtained on the forearms with increasing age. Differences between the surface topographies of forearm and back were only expressed by the waviness and the Fourier analysis. The treatment with botulinum Toxin A led to a diminution of mimic wrinkles as reflected by the furrow profiles. Conclusions The results show a significant dependence of the skin surface topography on the age of the volunteer and the body site measured. Particularly the waviness, the Fourier analysis and the furrow profiles reflect such dependencies. The system used also fulfils the requirements for the testing of therapies, as was demonstrated by the reduction of mimic wrinkles after treatment with botulinum Toxin A.

Ute Jacobi

Papers

Porcine ear skin: an in vitro model for human skin

The tape stripping procedure--evaluation of some critical parameters.

Differential stripping: determination of the amount of topically applied substances penetrated into the hair follicles.

In vivo determination of skin surface topography using an optical 3D device.

Comparison of stratum corneum penetration and localization of a lipophilic model drug applied in an o/w microemulsion and an amphiphilic cream.