[Follicular penetration of nanocarriers is an important penetration pathway for topically applied drugs]. / Bedeutung des follikulären Penetrationswegs für den Wirkstofftransport mittels Nanocarriern.

BACKGROUND: The hair follicle represents a significant penetration route for topically applied substances. ISSUE: The percutaneous absorption of substances can be significantly increased and accelerated by the involvement of hair follicles. In addition, nanoparticles have the characteristic to penetrate deeply and effectively into the hair follicles. MATERIALS AND METHODS: An optimization of drug delivery for topically applied substances is possible if the nanoparticles act solely as a carrier to transport active ingredients into the hair follicle. Once the nanocarrier has penetrated into the hair follicle, the active substance must be released there. This can be triggered by various mechanisms. RESULTS: The released drug can thus pass into the living tissue surrounding the hair follicle independently. With the help of this innovative strategy, the bioavailability of topically applied substances can be significantly improved. CONCLUSION: The transport of active ingredients into the hair follicles with the help of particles and the release of active substances there is a very effective new method for transporting active substances through the skin barrier.

Prevention of palmoplantar erythrodysesthesia in patients treated with pegylated liposomal doxorubicin (Caelyx®).

PURPOSE: Palmoplantar erythrodysesthesia (PPE) is one of the most frequent side effects during systemic treatment with pegylated liposomal doxorubicin (PLD, Caelyx®). PPE lesions show a range of symptoms, from numbness to painful erosions, and can have a major impact on the quality of life in affected patients. Previously, a possible pathomechanism of PPE was found in doxorubicin-treated patients based on radical formation in the skin. Here, a preventive strategy using a topically applied ointment with a high radical protection factor was investigated. METHODS: In this randomized placebo-controlled double-blind study the antioxidant-containing ointment was compared with a placebo ointment regarding PPE grade III occurrence, overall PPE grade I-III occurrence and PPE severity in PLD patients. The verum or placebo cream was topically applied for a period of 16 weeks, starting 3 days prior to the first cycle of chemotherapy. Clinical evaluations were carried out by a dermatologist prior to the first cycle of chemotherapy and every 4 weeks for the duration of 16 weeks. RESULTS: Thirty-two patients were enrolled in total, of which 17 (66%) completed the study. No PPE grade III was found in the verum group, while five out of seven patients (71%) had to be unblinded in the placebo arm due to PPE grade III (p = 0.003). General PPE occurrence of all grades was 60% under verum and 86% under placebo treatment. CONCLUSIONS: The preventive application of an antioxidant-containing ointment was shown to be significantly more effective in the prevention of PPE grade III compared to placebo treatment.

Clinical use of cold atmospheric pressure argon plasma in chronic leg ulcers: A pilot study.

OBJECTIVE: In the age of multiresistant microbes and the increasing lack of efficient antibiotics, conventional antiseptics play a critical role in the prevention and therapy of wound infections. Recent studies have demonstrated the antiseptic effects of cold atmospheric pressure plasma (APP). In this pilot, study we investigate the overall suitability of one of the first APP sources for wound treatment focusing on its potential antimicrobial effects. METHOD: The wound closure rate and the bacterial colonisation of the wounds were investigated. Patients suffering from chronic leg ulcers were treated in a clinical controlled monocentric trial with either APP or octenidine (OCT). In patients who presented with more than one ulceration in different locations, one was treated with APP and the other one with OCT. Each group was treated three times a week over a period of two weeks. The antimicrobial efficacy was evaluated immediately after and following two weeks of treatment. RESULTS: Wounds treated with OCT showed a significantly higher microbial reduction (64%) compared to wounds treated with APP (47%) immediately after the treatment. Over two weeks of antiseptic treatment the bacterial density was reduced within the OCT group (-35%) compared to a slight increase in bacterial density in the APP-treated group (+12%). Clinically, there were no signs of delayed wound healing observed in either group and both treatments were well tolerated. CONCLUSION: The immediate antimicrobial effects of the APP prototype source were almost comparable to OCT without any signs of cytotoxicity. This pilot study is limited by current configurations of the plasma source, where the narrow plasma beam made it difficult to cover larger wound surface areas and in order to avoid untreated areas of the wound bed, smaller wounds were assigned to the APP-treatment group. This limits the significance of AAP-related effects on the wound healing dynamics, as smaller wounds tend to heal faster than larger wounds. However, clinical wound healing studies on a larger scale now seem justifiable. A more advanced plasma source prototype allowing the treatment of larger wounds will address APP's influence on healing dynamics, synergetic treatment with current antiseptics and effects on multiresistant bacteria.

Comparison of two encapsulated curcumin particular systems contained in different formulations with regard to in vitro skin penetration.

BACKGROUND: Curcumin is known for its anti-inflammatory, antioxidative, and anticarcinogenic properties. However, the strong lipophilic compound is not easily applicable, neither in water, nor directly in o/w formulations. So far, loading of nano or micro scaled carriers has enabled only an uptake up to 30% of curcumin. METHOD: In the present article, curcumin was successfully encapsulated into two different safe and inexpensive polymers, ethyl cellulose and methyl cellulose blended ethyl cellulose with a loading capacity of ~ 46-48%. In addition, the in vitro skin penetration of the two curcumin encapsulated particular systems, which were applied each in three different formulations, an o/w, w/o lotion, and water suspension, was investigated on porcine ear skin using Laser scanning microscopy. RESULTS: It was found that in comparison to water suspensions, o/w and w/o lotions enhanced, especially the follicular penetration of the encapsulated curcumin particles into porcine skin, whereas the w/o enhanced the penetration better than the o/w lotion. Furthermore, the application of ethyl cellulose blended with methyl cellulose improved the penetration of curcumin in all formulations. CONCLUSION: High loaded encapsulated curcumin systems, prepared from a simple and highly efficient encapsulation system can be used to transport curcumin effectively into the skin.

Alcohol consumption decreases the protection efficiency of the antioxidant network and increases the risk of sunburn in human skin.

In recent years, epidemiological data has demonstrated that alcohol consumption is a risk factor for sunburn, melanoma and nonmelanoma skin cancer. We hypothesized that if the concentration of the antioxidants in the skin has already decreased due to alcohol consumption, then an adequate neutralization of the free radicals induced by ultraviolet light cannot be performed. Based on this hypothesis, we determined the carotenoid concentration in the skin and the minimal erythema dose (MED) of 6 male human volunteers before and after consumption of alcohol or alcohol and orange juice combined. The results showed a significant decrease in the carotenoid concentration in the skin and the MED after alcohol consumption, but no significant decrease after a combined intake of alcohol and orange juice.

Methods for the evaluation of the protective efficacy of sunscreen products.

The objective of the present investigation was to examine the utilization of optical and spectroscopic methods for the noninvasive characterization of Anthelios XL Fluide Extreme (SPF 50+), an exemplary sunscreen, concerning its homogeneity of distribution on the skin, its spectroscopic properties and its overall protective efficacy. The homogeneity of the distribution of the sunscreen on the skin was investigated with a multiphoton tomography microscope. Additionally, the sum transmission spectrum was determined using tape stripping and spectroscopic measurements. The results revealed a very homogeneous distribution of the sunscreen on the skin surface and also in the deep furrows. The sum transmission spectrum reflects a high protective efficacy of the sunscreen in both the UVA and UVB ranges. The sunscreen Anthelios XL Fluide Extreme (SPF 50+) generates a comfortable feeling on the skin and can be easily distributed. The presented optical methods have been shown to be suitable to investigate the overall protective efficacy of sunscreen products objectively, noninvasively and quickly.

Drug delivery with topically applied nanoparticles: science fiction or reality.

The efficacy of topically applied drugs is determined by their action mechanism and their potential capacity of passing the skin barrier. Nanoparticles are assumed to be efficient carrier systems for drug delivery through the skin barrier. For flexible nanoparticles like liposomes, this effect has been well demonstrated. The penetration properties of solid nanoparticles are currently under intensive investigation. The crucial advantage of nanoparticles over non-particulate substances is their capability to penetrate deeply into the hair follicles where they can be stored for several days. There is no evidence, yet, that solid particles ≥40 nm are capable of passing through the healthy skin barrier. Therefore and in spite of the long-standing research efforts in this field, commercially available solid nanoparticle-based products for drug delivery through the healthy skin are still missing. Nevertheless, the prospects for the clinical use of nanoparticles in drug delivery are tremendous. They can be designed as transport systems delivering drugs efficiently into the hair follicles in the vicinity of specific target structures. Once deposited at these structures, specific signals might trigger the release of the drugs and exert their effects on the target cells. In this article, examples of such triggered drug release are presented.

In vivo investigations on the penetration of various oils and their influence on the skin barrier.

BACKGROUND: The skin represents a potent barrier to the environment, which can be enhanced by the topical application of skin care products, such as oil and oil-based formulations by moisturizing the skin. METHODS: The aim of this study was the investigation of the penetration behaviour of four vegetable oils and of paraffin oil into the stratum corneum by laser scanning microscopy. In addition, the occlusion capacity of these substances was assessed by transepidermal water loss (TEWL) measurements. Petrolatum served as a positive control for skin occlusion. The study was conducted in vivo and included six healthy volunteers. RESULTS: Paraffin oil, as well as the vegetable oils, penetrated only into the first upper layers of the stratum corneum. TEWL measurements indicated that the application of the vegetable oils (except jojoba oil) as well as paraffin oil, led to a similar occlusion of the skin surface. The most effective occlusion was found for petrolatum. CONCLUSION: For the investigated oils, a deeper penetration than into the first upper layers of the stratum corneum could be excluded. The decreased TEWL values indicate that the application of the oils leads to a semi-occlusion of the skin surface as it is intended by the use of oils to retain moisture in skin.

The influence of endurance exercise on the antioxidative status of human skin.

Oxidative stress is supposed to be responsible for a diversity of diseases. For protection purposes, the human organism exhibits a line-up of antioxidant substances functioning as radical catchers. As a result of neutralization of free radicals, antioxidants are destroyed. Therefore, the degradation of the antioxidants can be utilized as an indirect parameter for the measurement of free radical formation. As physical exercise may also induce oxidative stress, the aim of the present study was to determine the antioxidant substances, and more precisely, the carotenoid concentration in the skin of male volunteers during different sportive exposures (cycling and running with two different exercise intensities) with resonance Raman spectroscopic measurements. The results revealed that moderate and high intensity cycling and running decrease the carotenoid concentration of the skin, whereas both sport disciplines and both exercise intensities revealed similar results. It can be concluded that above a certain threshold, physical exercise leads to oxidative stress also in the skin associated with the decrease in the antioxidant concentration. This gives rise to the impairment of the first defence line of the skin and means an increase in the risk of sun exposure-induced damage, e.g., when exercise training is performed outside. Nevertheless, it has to be emphasized that sport in general applied at moderate loads has predominantly positive effects on the health of humans especially concerning cardiovascular and metabolic diseases.

Kinetics of physiological skin flora in a suction blister wound model on healthy subjects after treatment with water-filtered infrared-A radiation.

The effect of water-filtered infrared-A radiation (wIRA) on normal skin flora was investigated by generating experimental wounds on the forearms of volunteers utilizing the suction blister technique. Over 7 days, recolonization was monitored parallel to wound healing. Four groups of treatment were compared: no therapy (A), dexpanthenol cream once daily (B), 20 min wIRA irradiation at 30 cm distance (C), and wIRA irradiation for 30 min once daily together with dexpanthenol cream once daily (D). All treatments strongly inhibited the recolonization of the wounds. Whereas dexpanthenol completely suppressed recolonization over the test period, recolonization after wIRA without (C) and in combination with dexpanthenol (D) was suppressed, but started on day 5 with considerably higher amounts after the combination treatment (D). Whereas the consequence without treatment (A) was an increasing amount of physiological skin flora including coagulase-negative staphylococci, all treatments (B-D) led to a reduction in physiological skin flora, including coagulase-negative staphylococci. In healthy volunteers, wIRA alone and in combination with dexpanthenol strongly inhibited bacterial recolonization with physiological skin flora after artificial wound setting using a suction-blister wound model. This could support the beneficial effects of wIRA in the promotion of wound healing.

Ethnic differences in skin physiology, hair follicle morphology and follicular penetration.

BACKGROUND/AIMS: Inconsistent evidence is available that different ethnic groups exhibit differences in skin physiological parameters. Recently, variations in hair follicle morphology have been described, although the influence of such variations on the follicular penetration process has not been investigated until now. METHODS: The aim of the present study was thus to investigate skin physiological parameters, follicle morphology and the penetration process in different ethnic groups. RESULTS AND CONCLUSION: Whereas no significant differences with regard to skin physiological parameters could be observed, morphological analysis of the hair follicles revealed, inter alia, that Caucasians had significantly larger terminal hair follicles than Asians and Africans. The surface of the hair follicle infundibulum was shown to be 3% in Caucasians, 2.6% in Africans and 2.4% in Asians. The investigations into penetration revealed no significant differences after a 30-min penetration time, whereas after 24 h, the Asian volunteers presented significantly larger amounts of sodium fluorescein in the hair follicles and the stratum corneum, which may be explained by cultural habits.

Comparison of the antiseptic efficacy of tissue-tolerable plasma and an octenidine hydrochloride-based wound antiseptic on human skin.

Colonization and infection of wounds represent a major reason for the impairment of tissue repair. Recently, it has been reported that tissue-tolerable plasma (TTP) is highly efficient in the reduction of the bacterial load of the skin. In the present study, the antiseptic efficacy of TTP was compared to that of octenidine hydrochloride with 2-phenoxyethanol. Both antiseptic methods proved to be highly efficient. Cutaneous treatment of the skin with octenidine hydrochloride and 2-phenoxyethanol leads to a 99% elimination of the bacteria, and 74% elimination is achieved by TTP treatment. Technical challenges with an early prototype TTP device could be held responsible for the slightly reduced antiseptic properties of TTP, compared to a standard antiseptic solution, since the manual treatment of the skin surface with a small beam of the TTP device might have led to an incomplete coverage of the treated area.

Safety assessment by multiphoton fluorescence/second harmonic generation/hyper-Rayleigh scattering tomography of ZnO nanoparticles used in cosmetic products.

Zinc oxide nanoparticles (ZnO NPs) are commonly used as UV filters in commercial sunscreen products. Their penetration into the skin is intensively discussed in the literature. In the present in vivo study, penetration of ZnO NPs (30 nm in size) into human skin was investigated by multiphoton tomography. Based on the non-linear effects of a second harmonic generation and hyper-Rayleigh scattering, the distribution of ZnO NPs in the horny layers of the epidermis, as well as the furrows, wrinkles and orifice of the hair follicles was analyzed. This method permitted distinguishing between the particulate and dissolved forms of Zn. A detection limit of 0.08 fg/µm(3) was estimated. Taking advantage of this sensitivity, it was clearly shown that ZnO NPs penetrate only into the outermost layers of stratum corneum, furrows and into the orifices of the hair follicles and do not reach the viable epidermis.

In vivo methods for the analysis of the penetration of topically applied substances in and through the skin barrier.

The efficacy of a drug is characterized by its action mechanism and its ability to pass the skin barrier. In this article, different methods are discussed, which permit this penetration process to be analysed non-invasively. Providing qualitative and quantitative information, tape stripping is one of the oldest procedures for penetration studies. Although single cell layers of corneocytes are removed from the skin surface, this procedure is considered as non-invasive and is applicable exclusively to the stratum corneum. Recently, optical and spectroscopic methods have been used to investigate the penetration process. Fluorescence-labelled drugs can be easily detected in the skin by laser scanning microscopy. This method has the disadvantage that the dye labelling changes the molecular structures of the drug and consequently might influence the penetration properties. The penetration process of non-fluorescent substances can be analysed by Raman spectroscopy, electron paramagnetic resonance, CARS and multiphoton microscopic measurements. Using these methods, the concentration of the topically applied formulations in different depths of the stratum corneum can be detected by moving the laser focus from the skin surface deeper into the stratum corneum. The advantages and disadvantages of these methods will be discussed in this article.

Pathways of lateral spreading.

In the case of topically applied substances, usually both lateral spreading and competitive penetration into the skin occur in parallel. In the present study, the pathways of lateral spreading were studied quantitatively and visually. The local distribution and lateral spreading of the UV filter substance butyl methoxydibenzoylmethane applied in an o/w emulsion was studied on the forearm and the back. The tape stripping procedure was used to determine the recovery rates inside and outside the area of application. The skin characteristics of transepidermal water loss, pH value, hydration of the stratum corneum and sebum rate were determined at both anatomic sites. Photography and laser scanning microscopy were used to visually investigate the lateral spreading of topically applied dyes. On the back, a preferred direction of lateral spreading parallel to the body axis was observed. This result was caused by differences in the network of furrows. The furrows functioned as a pathway for lateral spreading, whereas the follicles formed a reservoir for the topically applied substance.

Skin disinfection by plasma-tissue interaction: comparison of the effectivity of tissue-tolerable plasma and a standard antiseptic.

Wound healing disorders frequently occur due to biofilm formation on wound surfaces requiring conscientious wound hygiene. Often, the application of conventional liquid antiseptics is not sufficient and sustainable as (1) the borders and the surrounding of chronic wounds frequently consist of sclerotic skin, impeding an effectual penetration of these products, and (2) the hair follicles representing the reservoir for bacterial recolonization of skin surfaces are not affected. Recently, it has been reported that tissue-tolerable plasma (TTP), which is used at a temperature range between 35 and 45°C, likewise has disinfecting properties. In the present study, the effectivity of TTP and a standard liquid antiseptic was compared in vitro on porcine skin. The results revealed that TTP was able to reduce the bacterial load by 94%, although the application of the liquid antiseptic remained superior as it reduced the bacteria by almost 99%. For in vivo application, however, TTP offers several advantages. On the one hand, TTP enables the treatment of sclerotic skin as well, and on the other hand, a sustainable disinfection can be realized as, obviously, also the follicular reservoir is affected by TTP.

Uptake of antioxidants by natural nutrition and supplementation: pros and cons from the dermatological point of view.

The pros and cons of the systemic and topical application of antioxidant substances are a subject of intense discussion among experts, with resulting confusion for consumers and producers. The objective of the present article is to clarify the various uncertainties relating to the use of antioxidant substances in dermatology. Whereas inappropriate application of antioxidant substances (concerning their concentration and composition) might induce harmful effects, the consumer will definitively benefit from physiological concentrations and compositions of antioxidants. The most suitable method is the consumption of natural antioxidants in the form of fruit and vegetables, for example. In addition, the skin, which also accumulates antioxidant substances, may profit from a sufficient antioxidative level, as damage induced by sun radiation in addition to skin aging is reduced.

Distribution of bacteria in the epidermal layers and hair follicles of the human skin.

Previous studies over recent years have revealed the presence of a resident bacterial population in the human skin throughout the entire body. However, the localization and composition of the bacteria within the epidermis and the skin appendages have not been fully investigated. Using differential tape stripping, cyanoacrylate skin surface biopsies and mapping of hair follicles, bacteria on the forearms of study participants were isolated, mapped, cultured and identified with respect to their origin within the epidermis and the hair follicles. Our studies showed that 85% of the bacteria were found within the first 6 corneocyte layers and roughly 25% of the cutaneous bacterial population were localized within the hair follicles. The microbial flora of the skin between individuals is subject to considerable fluctuations. Micrococcaceae represent the biggest fraction of hair-follicle-associated bacteria. The techniques developed for this study allowed us to selectively investigate the bacterial population within the hair follicles. Our results point out the role of skin appendages as potential microbial reservoirs and the need to develop new antiseptic formulations that sufficiently penetrate into the hair follicles.

Decontamination of the skin with absorbing materials.

Stimulation of the penetration of topically applied substances into the skin is a topic of intensive dermatological and pharmacological research. Next to intercellular penetration, i.e. a penetration inside the lipid layers around the corneocytes, follicular penetration also represents an efficient penetration pathway. The hair follicles act as a long-term reservoir for topically applied substances. They are surrounded by or contain several important target structures, such as blood capillaries, stem cells and dendritic cells. Therefore, the hair follicles have to be well protected from hazardous substances coming into contact with the skin. The traditional method of decontamination of the skin involves an intensive washing procedure. However, this process represents a massage, which pushes the hazardous substances even deeper into the hair follicles. In the present study, the application of absorbing materials for decontamination of the skin was investigated after the application of a model substance utilizing the tape-stripping procedure. It was found that absorbing materials are better suited than the washing process for decontamination of the skin.

Prevention of follicular penetration: barrier-enhancing formulations against the penetration of pollen allergens into hair follicles.

The hair follicles could be a reservoir for topically applied substances. They are not only surrounded by a close network of blood capillaries, which makes them interesting for drug delivery, but they are also the host of dendritic cells, which are important for immunomodulation. Previously, pollen allergens were shown to penetrate into the hair follicles. The application of barrier-enhancing formulations might represent an effective strategy to prevent pollen protein penetration into the hair follicle. In the present study, porcine skin areas were pretreated with 4 barrier-enhancing emulsions. One skin area served as control and remained without pretreatment. Afterwards, fluorescein-isothiocyanate-labeled grass pollen proteins were applied to the porcine skin samples, and their penetration was investigated via fluorescent laser scanning microscopy. It was shown that the barrier-enhancing formulations were able to significantly reduce the penetration of exogenous proteins into the hair follicles, the extent of such reduction depending on the formulation.