Analysis of the morphometric parameters of pig ear hair follicles

Background: Porcine ear skin is used in studies of percutaneous penetration as a substitute for human skin. The objective of the present study was to determine the structure of the hair follicles on the dorsal area of porcine ear skin and make a morphometric comparison with the hair follicles of human skin. Materials and methods: Sections of frozen biopsies were cut vertically to the skin surface in longitudinal sections using a cryotome and were investigated using microscopy. For each hair follicle, various parameters were determined. Results: The follicular density in porcine ear skin varies according to the area studied, and the length of most of the follicles was approximately 1458 ± 286 μm. The size of the follicular orifice was also determined in a total of 305 follicles. It showed a diameter of roughly 113 ± 43 μm. Conclusion: The results showed a very good similarity between human and pig hair follicles. Therefore, porcine ear skin can be considered as a very suitable model of human skin in dermal and especially follicular penetration studies

Ratchet effect for nanoparticle transport in hair follicles

The motion of a single rigid nanoparticle inside a hair follicle is investigated by means of Brownian dynamics simulations. The cuticular hair structure is modeled as a periodic asymmetric ratchet-shaped surface. Induced by oscillating radial hair motion we find directed nanoparticle transport into the hair follicle with maximal velocity at a specific optimal frequency and an optimal particle size. We observe flow reversal when switching from radial to axial oscillatory hair motion. We also study the diffusion behavior and find strongly enhanced diffusion for axial motion with a diffusivity significantly larger than for free diffusion

Laser Scanning Microscopic Investigations of the Decontamination of Soot Nanoparticles from the Skin

Background/Aims: Airborne pollutants, such as nano-sized soot particles, are increasingly being released into the environment as a result of growing population densities and industrialization. They can absorb organic and metal compounds with potential biological activity, such as polycyclic aromatic hydrocarbons and airborne pollen allergens. Local and systemic toxicities may be induced in the skin if the particulates release their harmful components upon dermal contact. Methods: In the present study, skin pretreatments with serum and/or shield as barrier formulations prior to exposure and washing with a cleanser subsequent to exposure were evaluated as a protection and decontamination strategy using laser scanning microscopy. Results: The results indicate that while the application of serum and a cleanser was insufficient for decontamination, the pretreatment with shield prior to nanoparticle exposure followed by washing led to the removal of a considerable amount of the carbon black particles. The combined application of serum and shield before the administration of carbon black particles and subsequent washing led to their elimination from the skin samples. Conclusion: The application of barrier-enhancing formulations in combination with a cleanser may reduce the penetration of harmful airborne particulates by preventing their adhesion to the skin and facilitating their removal by subsequent washing with the cleanser

Application of parelectric spectroscopy to detect skin cancer—A pilot study

Background: The early detection of skin cancer is still challenging and calls for objective, fast diagnostic, and ideally non-invasive methods in order to leave the potentially malignant tumor cells unaltered. In this paper, the parelectric spectroscopy was applied to evaluate the potential of a non-invasive detection of basal cell carcinoma (BCC) and malignant melanoma. Materials and methods: A prototype of parelectric spectroscopy was used to investigate non-invasively dipole density and mobility of suspicious skin lesions. The differences in investigated tissue were analyzed compared to pathohistological findings in a clinical study on 51 patients with suspected BCC and malignant melanoma. Results: The non-invasive parelectric spectroscopy could differentiate between normal skin, BCC, and melanoma but failed to distinguish between different types of skin cancer. The data were normalized to unsuspected nearby skin because the different skin locations influence dipole density and mobility. Conclusion: The results of the pilot study indicate that the parelectric spectroscopy might be an additional, useful non-invasive diagnostic procedure to distinguish between normal skin and skin cancer

Laser scanning microscopy for control of skin decontamination efficacy from airborne particulates using highly absorbent textile nanofiber material in combination with PEG‐12 dimethicone

Background The decontamination of the skin is indispensable if airborne particulate contaminants deposit on the skin surface. Skin washing can have adverse effects as by skin rubbing the particles can be transferred deeply into the hair follicles, where they can be entrapped for a period of more than 10 days. Thus, alternative skin decontamination strategies are necessary. Materials and Methods For imaging the contaminants in the skin, sodium fluorescein-labeled soot particles of submicron size (approximate to 600 nm) were visualized using laser scanning microscopy. Results In the present ex vivo pilot study on porcine ear skin, it was shown that sodium fluorescein-labeled soot particles of submicron size (approximate to 600 nm) could be efficiently removed from the skin with highly absorbent textile nanofiber material, whose efficacy could be further increased by spraying the contaminated skin area with the viscous fluid PEG-12 dimethicone before textile application. Conclusion In case of skin contamination with particulates, the contact washing should be avoided due to rubbing particles deeply into the hair follicles, where they can accumulate for a long time and induce negative consequences. Efficient skin decontamination could include pretreatment of skin surface with the viscous fluid PEG-12 dimethicone and subsequent application of highly absorbent textile nanofiber material

Follicular and transfollicular penetration

Die Haut ist das größte und eines der lebenswichtigen Organe des Menschen. Ohne die Schutz- und Barrierefunktionen der Haut könnte ein Organismus nicht überleben. Dennoch ist es möglich, dass topisch applizierte Substanzen und Wirkstoffe die Hautbarriere überwinden können. Die Optimierung des topischen Applikationsweges ist Gegenstand intensiver aktueller Forschung. Prinzipiell sind drei Penetrationswege (interzellulär, follikulär und transzellulär) in und durch die Haut bekannt, wobei der follikuläre Weg immer mehr an Bedeutung gewinnt und auch Thema der vorliegenden Arbeit ist. Die konkrete Zielstellung der Arbeit war neben der Entwicklung von in vivo und ex vivo Methoden zur Untersuchung des follikulären Penetrationsprozesses auch die Identifizierung von geeigneten ex vivo Hautmodellen sowie die Aufklärung des Mechanismus der follikulären Penetration und die Entwicklung von neuen Ansätzen zum follikulären Wirkstofftransport. Im Rahmen der Arbeit konnten zwei Methoden zur Untersuchung der follikulären und transfollikulären Penetration etabliert werden. Mit Hilfe der Methode des selektiven Follikelverschlusses ist es nun möglich, den follikulären Anteil am Penetrationsprozess zu quantifizieren. Das ebenfalls etablierte Verfahren des differentiellen Strippings dagegen ermöglicht die selektive Quantifizierung des follikulären und interzellulären Reservoirs. In weiteren Arbeiten konnte das Schweineohrhautmodell klar als geeignetes ex vivo Hautmodell für Untersuchungen zur follikulären Penetration identifiziert werden, während die Anwendung von ex vivo Humanhaut als ungeeignet für entsprechende Untersuchungen eingestuft werden musste. Weiterführende Studien konnten zur Aufklärung des Mechanismus der follikulären Penetration beitragen. Es konnte klar belegt werden, dass Nanocarrier besonders effektiv in den Haarfollikel hinein penetrieren können und dass hier eine eindeutige Größenabhängigkeit besteht. Nanocarrier der Größe um 600 nm zeigten dabei die tiefste follikuläre Penetration. Anschließende Untersuchungen haben ergeben, dass diese Größenabhängigkeit im Zusammenhang mit der Struktur des Haares steht, und dass hier ein sogenannter Ratscheneffekt zwischen der Schuppenstruktur der Haares und der Nanocarrier die tiefe Penetration bewirkt. Auf Grundlage der Ergebnisse, dass partikuläre Substanzen besonders tief und effektiv in den Haarfollikel hinein penetrieren können, aufgrund ihrer Größe jedoch nicht transfollikulär in das den Haarfollikel umgebende Gewebe translozieren können, wurden neue Ansätze entwickelt, um die positiven Eigenschaften von Nanocarriersystemen trotzdem für den Wirkstofftransport nutzen zu können. Die grundsätzliche Idee besteht darin, die Nanocarrier nur für den Transport in den Haarfollikel zu nutzen, wo es dann ausgelöst durch ein Triggersignal zu einer Wirkstofffreisetzung aus den Nanocarriern kommt. Dieser kann dann unabhängig transfollikulär diffundieren. Als entsprechende Triggersignale wurden eine enzymatische Freisetzung und eine Infrarot-A-getriggerte Freisetzung erfolgreich getestet. Damit konnten in der vorliegenden Arbeit einige wichtige Aspekte der follikulären und transfollikulären Penetration näher herausgearbeitet werden und erste Untersuchungen zur getriggerten Freisetzung von Wirkstoffen im Haarfollikel erfolgreich realisiert werden. Dies ist ein vielversprechender Ansatz, der in den nächsten Jahren weiter verfolgt werden wird.The skin is the biggest and one of the vital organs of the human body. Without the protective and barrier functions of the skin, the body could not survive. However, it is possible for topically applied drugs to overcome the cutaneous barrier. Currently, the optimization of the topical application pathway is a subject of intense research. The intercellular, follicular and transcellular routes are the three known penetration pathways into and through the skin, with the follicular route becoming more and more important. This follicular pathway is addressed in this habilitation thesis. The specific objective of this thesis was not only the development of in vivo and ex vivo methods suited to investigate the follicular penetration process but also the identification of suitable ex vivo skin models, the revelation of the follicular penetration mechanism and the development of new approaches towards the follicular drug transport. As a result of the habilitation studies, two methods for investigating the follicular and transfollicular penetration could be established. One of these methods, the selective follicle occlusion, now permits to quantify the follicular proportion in the penetration process. The differential stripping procedure, in turn, permits the follicular and intercellular reservoirs to be selectively quantified. In further experiments, the porcine ear skin model could be definitely identified as a well-suited ex vivo skin model for follicular penetration studies, whereas ex vivo human skin proved to be unsuitable for such investigations. Further studies contributed to reveal the follicular penetration mechanism. It could be clearly demonstrated that nanocarriers can penetrate very efficiently into the hair follicle and that this penetration efficiency definitely depends on the carrier size. Nanocarriers of about 600 nm in size penetrated deepest into the hair follicle. Subsequent experiments showed that this size dependency is due to the hair structure; a so-called ratchet effect between the cuticula structure of the hair and the nanocarrier causing the deep penetration. Based on the findings that particulate substances can penetrate very deeply and efficiently into the hair follicle, whereas their size keeps them from translocating into the tissue surrounding the hair follicle, new approaches were developed in order to utilise the positive properties of nanocarrier systems nevertheless for drug delivery. The basic idea is to use the nanocarriers exclusively for the transport into the hair follicle. Once there, the carrier releases its drug load via a trigger signal. The drug so released can then transfollicularly diffuse without assistance. An enzymatic release and an infrared A-triggered release were successfully tested as trigger signals. Thus, the present thesis could reveal some important aspects of follicular and transfollicular penetration. Moreover, initial experiments with the triggered release of drugs into the hair follicles could be completed successfully. This is a very promising approach which will be followed up in the years to come

Solvent Effects on Skin Penetration and Spatial Distribution of the Hydrophilic Nitroxide Spin Probe PCA Investigated by EPR

Oxidative stress occurs in extrinsic skin aging processes and diseases when the enhanced production of free radicals exceeds the homeostatic antioxidant capacity of the skin. The spin probe, 3-(carboxy)-2,2,5,5-tetramethylpyrrolidin-1-oxyl (PCA), is frequently used to study the cutaneous radical production by electron paramagnetic resonance (EPR) spectroscopy. This approach requires delivering PCA into the skin, yet solvent effects on the skin penetration and spatial distribution of PCA have not been thoroughly investigated. Three solvents of ethanol, phosphate-buffered saline (PBS) and ethanol-PBS (1:1) were studied. For both human and porcine skin ex vivo, the amount of PCA in the stratum corneum (SC) was the lowest when using ethanol and very similar for PBS and ethanol-PBS. The highest amount of PCA in the viable skin layers was detected for ethanol-PBS, yet it only took up less than 5% of the total amount. The majority of PCA was localized in the SC, among which PCA with high mobility was predominantly distributed in the hydrophilic microenvironment of corneocytes and PCA with lower mobility was mainly in the less hydrophilic microenvironment of intercellular skin lipids. A higher ethanol concentration in the solvent could improve the distribution of PCA in the hydrophilic microenvironments of the SC. The results suggest that ethanol-PBS (1:1) is best-suited for delivering most PCA deep into the skin. This work enhances the understanding of solvent effects on the skin penetration and distribution of PCA and supports the utilization of PCA in studying cutaneous radical production