Cutaneous distribution and localization of dyes affected by vehicles all with different lipophilicity

Mechanisms of penetration and diffusion of drugs and cosmetic actives across the human Stratum corneum

Based on the structure of the Stratum corneum (SC) the potential penetration/diffusion pathways of drugs and cosmetic actives through the SC are presented and discussed. The well-known lipophilic pathway across the SC is presented and relevant examples are used to show that highly lipophilic molecules such as glucocorticoids, coenzyme Q10 etc. are accumulated in the SC and penetrate into the inner liquid like layer of the SC lipid bilayer by lateral diffusion. The diffusion into and across the SC of highly hydrophilic drugs and active substances such as urea, amino acids and peptides is still under discussion. Another diffusion pathway for the highly hydrophilic molecules via the corneocytes and the corneodesmosomes is presented and discussed, the corneocytary diffusion pathway.

Transfersomes improved delivery of ascorbic palmitate into the viable epidermis for enhanced treatment of melasma

Ascorbic palmitate (AP) is widely used in the topical pharmaceutical or cosmetic formulations for melasma treatment. However, the presence of the skin barriers makes it difficult for the highly lipophilic drug molecules to traverse the stratum corneum (SC) and diffuse into the viable epidermis (EP) to reach the melanocytes, thereby exerting suboptimal antimelasma effects. Herein, AP was encapsulated into the transfersomes (TFs), yielding AP-TFs. AP-TFs utilized the deformability of TFs to squeeze through the skin pores in the SC under the transepidermal hydration gradient forces, leading to 14.1-fold increase in AP accumulation to the EP. AP-TFs could slowly release the encapsulated AP, while whether the released AP or transfersomal AP showed comparable uptake into the melanocytes, thereby exerting similar inhibitory effects on tyrosinase activity and melanogenesis. Ultimately, in the rat melasma model, AP-TFs showed superior antimelasma efficacy to free AP, with effective relief of oxidative stress and inflammation in the skin. Moreover, AP-TFs did not induce skin irritation. Therefore, the study provides a safe and effective approach to elevating the delivery of highly lipophilic drugs to the EP for enhanced treatment of melasma.

Caffeine and Its Pharmacological Benefits in the Management of Androgenetic Alopecia: A Review

Caffeine, particularly after ingestion, is well known to exert various pharmacological effects. A growing body of evidence implicates the ingestion of caffeine with beneficial effects on several diseases. The easy penetration of caffeine across the skin barrier and into human skin makes caffeine an ideal compound for topical application. Hair loss is known to negatively affect the quality of life and predispose to depression and anxiety. Androgenetic alopecia (AGA) is the most common type of hair loss in both men and women. To date, only few approved drug-based treatments for AGA exist, and these are inevitably associated with side effects. Therefore, the development of topical treatments based on well-tolerated natural ingredients such as caffeine to alleviate hair loss may provide a much-needed alternative to drug-based approaches.

Salt water and skin interactions: new lines of evidence

In Health Resort Medicine, both balneotherapy and thalassotherapy, salt waters and their peloids, or mud products are mainly used to treat rheumatic and skin disorders. These therapeutic agents act jointly via numerous mechanical, thermal, and chemical mechanisms. In this review, we examine a new mechanism of action specific to saline waters. When topically administered, this water rich in sodium and chloride penetrates the skin where it is able to modify cellular osmotic pressure and stimulate nerve receptors in the skin via cell membrane ion channels known as "Piezo" proteins. We describe several models of cutaneous adsorption/desorption and penetration of dissolved ions in mineral waters through the skin (osmosis and cell volume mechanisms in keratinocytes) and examine the role of these resources in stimulating cutaneous nerve receptors. The actions of salt mineral waters are mediated by a mechanism conditioned by the concentration and quality of their salts involving cellular osmosis-mediated activation/inhibition of cell apoptotic or necrotic processes. In turn, this osmotic mechanism modulates the recently described mechanosensitive piezoelectric channels.

Hydrogel-based ultra-moisturizing cream formulation for skin hydration and enhanced dermal drug delivery

To develop an external vehicle for skin hydration and enhanced dermal drug delivery, a hydrogel-based ultra-moisturizing cream (HUMC) was successfully formulated with carbopol 934P, urea, Tinocare GL, grape seed oil, and other excipients. The HUMC showed plastic flow behavior due to a gel structure with a cream base. Different types of drug-free vehicles such as a hydrogel, conventional cream (CC), and three HUMCs were prepared and subjected to an in vivo skin hydration test on a hairless mouse using a corneometer. Hydration effect (∆AU) was in the order of HUMC2>HUMC1 ≥ CC>HUMC3>hydrogel. Using nile red (NR) and 5-carboxyfluorescein (5-CF) as lipophilic and hydrophilic fluorescent probes, respectively, in vitro skin permeation and accumulation studies were conducted using Franz diffusion cells. The values of steady-state flux (Jss, ng/h/cm(2)) were obtained: 74.8 (CC), 145.6 (HUMC1), and 161.9 (HUMC2) for NR delivery; 6.8 (CC), 8.3 (HUMC1), and 10.9 (HUMC2) for 5-CF delivery. The amounts retained in the skin at 12 h (Qr, ng/cm(2)) were determined: 86.4 (CC) and 102.0 (HUMC2) for NR; and 70.1 (CC) and 195.6 (HUMC2) for 5-CF. Confocal microscopy was used to visualize the distribution of the fluorescent probes. NR tended to be localized into the deeper part of the skin with adipose tissue whereas 5-CF localized in the upper layer of the skin. Thus we propose that HUMC2 is an efficacious vehicle for skin hydration and enhances dermal delivery of lipophilic and hydrophilic drugs.

Recent advances in predicting skin permeability of hydrophilic solutes

Understanding the permeation of hydrophilic molecules is of relevance to many applications including transdermal drug delivery, skin care as well as risk assessment of occupational, environmental, or consumer exposure. This paper reviews recent advances in modeling skin permeability of hydrophilic solutes, including quantitative structure-permeability relationships (QSPR) and mechanistic models. A dataset of measured human skin permeability of hydrophilic and low hydrophobic solutes has been compiled. Generally statistically derived QSPR models under-estimate skin permeability of hydrophilic solutes. On the other hand, including additional aqueous pathway is necessary for mechanistic models to improve the prediction of skin permeability of hydrophilic solutes, especially for highly hydrophilic solutes. A consensus yet has to be reached as to how the aqueous pathway should be modeled. Nevertheless it is shown that the contribution of aqueous pathway can constitute to more than 95% of the overall skin permeability. Finally, future prospects and needs in improving the prediction of skin permeability of hydrophilic solutes are discussed.

Fluorescence induction of protoporphyrin IX by a new 5-aminolevulinic acid nanoemulsion used for photodynamic therapy in a full-thickness ex vivo skin model

An ex vivo porcine skin model was utilized to analyse the penetration of 5-aminolevulinic acid (5-ALA) contained in a nanoemulsion-based formulation BF-200 ALA (10% 5-ALA-hydrochloride) versus 16% aminolevulinate methyl ester-hydrochloride in a commercially cream (MAL cream) by fluorescence microscopy of their common metabolite protoporphyrin IX (PpIX) after 3, 5, 8 and 12 h. Fluorescence signals of PpIX in pig skin treated with BF-200 ALA were stronger than those for MAL cream. At 8 and 12 h, the PpIX fluorescence signals were 4.8- and 5.0-fold higher than those measured after MAL cream application. Fluorescence signals of PpIX after application of BF-200 ALA were detected in deeper tissue layers of the epidermis than after application of MAL cream (97.2 +/- 5.7 microm for BF-200 ALA vs 42.0 +/- 4.2 microm for MAL cream). These data implicate that BF-200 ALA in photodynamic therapy might lead to a superior therapeutically effect of intraepidermal (in situ) squamous cell carcinomas.

Surface charged temoporfin-loaded flexible vesicles: in vitro skin penetration studies and stability

In order to increase topical delivery of temoporfin (mTHPC), a highly hydrophobic photosensitizer with low percutaneous penetration, neutral, anionic and cationic flexible liposomes (i.e. flexosomes) were prepared and investigated for their penetration enhancing ability. The in vitro skin penetration study was performed using human abdominal skin mounted in Franz diffusion cells. Besides the effect of surface charge of flexosomes on skin penetration of mTHPC, also its effect on physical properties (particle size, polydispersity index, lamellarity) and physicochemical stability of vesicles was investigated. Photon-correlation spectroscopy revealed that vesicles had after preparation a small particle size and low polydispersity index, while cryo-electron microscopy confirmed that these vesicles were mostly unilamellar and of a spherical shape. Regarding stability, contrasting to anionic flexosomes showing lack of long-term stability, neutral and cationic flexosomes were stable during 9 months storage at 4 degrees C. As to the penetration enhancing ability, cationic flexosomes possessed the highest, i.e. they delivered the highest mTHPC-amount to stratum corneum and deeper skin layers compared to conventional liposomes, neutral and anionic flexosomes. In conclusion, mTHPC-loaded cationic flexosomes could be a promising tool for delivering mTHPC to the skin, which would be beneficial for the photodynamic therapy of cutaneous malignant or non-malignant diseases.

Pig skin structure and transdermal delivery of liposomes: a two photon microscopy study

In this work we have characterized the architecture and physical properties of pig skin epidermis including its permeability to different liposome formulations. Autofluorescence images show that cells in the epidermis, from the basal layer to the stratum corneum, are organized in clusters that are in turn separated by particular structures we named "canyons". These canyons start in the surface as a wrinkle, eventually closing and going all the way inside the epidermis as a distinct structure that reaches the stratum basale. This structure, described previously in the epidermis of mouse skin as "intercluster pathway", was suggested to be filled with an unknown material and offer low resistance to vesicle penetration. Analysis of LAURDAN Generalized Polarization images of pig skin show that the canyons are filled with a non-polar poorly hydrated material, similar to that observed in pig skin stratum corneum. These results together with the data obtained from skin autofluorescence images suggest that these canyons are invaginations/extension of SC material. Fluorescently labeled lipids incorporated into very flexible liposomes are able to penetrate into the skin, eventually reaching the basal layer and the dermis plane. The presence of charged lipids in the liposomes enhances size stability and thus the efficiency of penetration.

Laparoscopic visualization and dissection of retroperitoneal lymph nodes after patent blue dye injection: a pilot study

PURPOSE

Retroperitoneal lymph node dissection (RPLND) for testicular cancer is an important treatment modality for patients with stage I or IIA disease. Several urologists have previously reported the feasibility and usefulness of laparoscopic RPLND for such patients. The aim of this experimental pilot-feasibility study was to investigate whether visualization of retroperitoneal lymph nodes with patent blue violet (PBV) dye application is a feasible and an effective method during laparoscopic RPLND in a pig model.

MATERIALS AND METHODS

Four 12-month-old white male pigs were included in the study. After PBV dye injection into the spermatic funicular and intratesticular parenchyma, the color changes in the retroperitoneal region were examined during transperitoneal laparoscopic visualization of the retroperitoneum. The time interval between the injection and the staining of lymphatic structures was measured for each intervention. Blue-stained retroperitoneal nodal tissues were dissected and removed by the laparoscopic approach and histologic examination was performed.

RESULTS

After PBV dye injection, intense staining of the ipsilateral retroperitoneal lymphatic vessels and nodes was seen. Distribution of the PBV and the color changes of the retroperitoneal lymphatic structures were examined under laparoscopic vision in all pigs. All blue-stained retroperitoneal nodular tissues were removed laparoscopically and examined histologically. Histopathologic examination noted all specimens as lymph nodes with no toxic effects of PBV dye.

CONCLUSION

We demonstrated that spermatic funicular injection of PVB dye is an effective and accurate method for retroperitoneal lymph node visualization in pigs. The use of this technique in combination with a laparoscopic approach makes RPLND easier and more effective.

In-silico model of skin penetration based on experimentally determined input parameters. Part II: Mathematical modelling of in-vitro diffusion experiments. Identification of critical input parameters

This work describes a framework for in-silico modelling of in-vitro diffusion experiments illustrated in an accompanying paper [S. Hansen, A. Henning, A. Naegel, M. Heisig, G. Wittum, D. Neumann, K.-H. Kostka, J. Zbytovska, C.M. Lehr, U.F. Schaefer, In-silico model of skin penetration based on experimentally determined input parameters. Part I: experimental determination of partition and diffusion coefficients, Eur. J. Pharm. Biopharm. 68 (2008) 352-367 [corrected] A mathematical model of drug permeation through stratum corneum (SC) and viable epidermis/dermis is presented. The underlying geometry for the SC is of brick-and-mortar character, meaning that the corneocytes are completely embedded in the lipid phase. The geometry is extended by an additional compartment for the deeper skin layers (DSL). All phases are modelled with homogeneous diffusivity. Lipid-donor and SC-DSL partition coefficients are determined experimentally, while corneocyte-lipid and DSL-lipid partition coefficients are derived consistently with the model. Together with experimentally determined apparent lipid- and DSL-diffusion coefficients, these data serve as direct input for computational modelling of drug transport through the skin. The apparent corneocyte diffusivity is estimated based on an approximation, which uses the apparent SC- and lipid-diffusion coefficients as well as corneocyte-lipid partition coefficients. The quality of the model is evaluated by a comparison of concentration-SC-depth-profiles of the experiment with those of the simulation. Good agreements are obtained, and by an analysis of the underlying model, critical parameters of the models can be identified more easily.

CELL GROWTH REGULATION

Curcumin, the active ingredient of turmeric (Curcuma longa) used in culinary and medical practices in Asia, has immense potential for being used in cancer chemotherapy because of its control over the cell growth regulatory mechanisms. The present chapter throws light on the role of curcumin in modulating the various phases of the cell cycle and its apoptosis-inducing effects. This is followed by a discussion on the implications of these effects of curcumin for its use as a chemotherapeutic agent in cancer. Curcumin affects various cell cycle proteins and checkpoints involving downregulation of some of the cyclins and cyclin-dependent kinases, upregulation of cdk inhibitors, and inhibition of DNA synthesis. In addition, curcumin also exerts indirect control over cell division such as inhibition of telomerase activity. Remarkably, some studies point toward a selective growth-inhibitory effect of curcumin on transformed cell lines compared to nontransformed cell lines. Curcumin has also been demonstrated to have proapoptotic effects in several in vitro studies, mostly through the mitochondria-mediated pathway of apoptosis. Curcumin-mediated regulation of apoptosis involves caspases, Bcl2 family members, inhibitors of apoptosis proteins, and heat shock proteins. The accumulating data on the in vitro and in vivo actions of curcumin together with the ongoing human clinical trials will provide a better understanding of curcumin-mediated cell growth regulation, ultimately catering to the needs of human welfare.

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

Vehicle dependent effects on the penetration behavior of drugs following topical application are well known from the literature. In this context, many reports concerning the enhancing activities for hydrophilic as well as lipophilic substances by colloidal drug carrier systems, particularly microemulsions, are available. However, there is little knowledge about the localization of the drugs within the skin and the stratum corneum, respectively. In the present study, the lipophilic dye curcumin incorporated in an oil-in-water microemulsion and in an amphiphilic cream was applied onto the skin of human volunteers. Using the method of tape stripping to remove the stratum corneum (SC), the depth profiles of the dye within the horny layer were compared. Applying the microemulsion, a deeper part of the SC was accessible by a number of 20 tapes removed and significantly smaller amounts of curcumin were found on the skin surface. Also differences in the distribution and localization of the dye within the stratum corneum were observed by laser scanning microscopy. Furthermore, curcumin was detected in hair follicles. It was obvious that the microemulsion led to a penetration into the complete follicular infundibula, whereas, following application of the cream, a fluorescence signal was only received from the follicular orifices.

Follicular penetration of topically applied caffeine via a shampoo formulation

AIMS

Follicular drug delivery is the prerequisite for an effective treatment of androgenetic alopecia or other reasons of premature hair loss.

METHODS

The follicular penetration of caffeine, applied topically in a shampoo formulation for 2 min, was measured with highly sensitive surface ionization in combination with mass spectroscopy, a selective method for the detection of very small quantities of transcutaneously absorbed substances in the blood. An experimental protocol, developed to selectively block the follicular pathway within the test area, was used. Based on this principle, a clear distinction between interfollicular and follicular penetration of topically applied caffeine was feasible.

RESULTS

After 2 min, caffeine penetrated via the hair follicles and stratum corneum.

CONCLUSION

It was found that the penetration via hair follicles was faster and higher compared with the interfollicular route and that hair follicles are the only pathway for fast caffeine absorption during the first 20 min after application.