Showing papers by "Joke A. Bouwstra published in 2007"

A novel ex vivo skin model to study the susceptibility of the dermatophyte Trichophyton rubrum to photodynamic treatment in different growth phases

Abstract: Background Dermatophytes are fungi that can cause infections of skin, hair and nails because of their ability to feed on keratin. Superficial mycoses are among the most prevalent infectious diseases worldwide. Two important restrictions of current therapeutic options are the recurrence of the infection and prolonged treatment. This is especially true for infections caused by Trichophyton rubrum, a widely distributed dermatophyte. The application of photosensitizers for treatment of fungal infections is, within the field of photodynamic treatment (PDT), relatively new. Recently, we demonstrated that the porphyrins 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) and deuteroporphyrin monomethylester (DP mme) were excellent photosensitizers towards T. rubrum when using red light. Objectives and methods To evaluate the photodynamic effectiveness of the porphyrins in a situation that mimics the clinical situation, we developed an ex vivo model using human stratum corneum. This model offers the possibility of applying PDT at different time points during the germination and subsequent development of T. rubrum microconidia. The model was used for two different incubation media, Dulbecco's modified Eagle medium (DMEM) and distilled water. Results and conclusions We demonstrated that the PDT susceptibility of T. rubrum depended on the time of PDT application after spore inoculation. A decrease in susceptibility was observed with increasing time of PDT application for both photosensitizers in DMEM. Changing the incubation medium to distilled water resulted in an increased fungicidal effect for Sylsens B and in a decreased effect for DP mme. We conclude that T. rubrum is susceptible to PDT in a situation that mimics the clinical situation. The fungicidal effect of PDT on fungal spores is of particular importance.

Preparation and characterization of structured hydrogel microparticles based on cross-linked hyperbranched polyglycerol.

Abstract: The aim of this work was to obtain well-defined HyPG-MA (methacrylated hyperbranched polyglycerol) microparticles with uniform sizes. Therefore, three different preparation methods were evaluated. First, we assessed a micromolding technique using rigid SU-8 (a photoresist based on epoxies) grids. Independent of the surface treatment of the SU-8 grid or the type of polymer used, approximately 50% of the microgels remained attached to the SU-8 grid or broke into smaller particles during the release process in which drying of the gels was followed by a sonication process. Although 90% methacrylate conversion could be obtained, this method has some additional drawbacks as the obtained dried microgels did not rehydrate completely after the drying step. Second, a soft micromolding technique was evaluated using elastomeric PDMS (poly(dimethyl siloxane)) grids. The use of these flexible grids resulted in a high yield (80−90% yield; >90% methacrylate conversion) of microgels with a well-defined size and shape (squ...

Lipophilic and hydrophilic moisturizers show different actions on human skin as revealed by cryo scanning electron microscopy

Abstract: To study the mode of action of moisturizers on human skin, hydrophilic moisturizers in water and neat lipophilic moisturizers were applied on excised skin for 24 h at 32°C. Samples of the treated skin were subsequently visualized in a cryoscanning electron microscope. The stratum corneum (SC) appeared as a region of swollen corneocytes (the swollen region) sandwiched between two layers of relatively dry corneocytes (the upper and lower non-swelling regions respectively). Lipophilic moisturizers increased the water content of the SC, whereas hydrophilic moisturizers can also reduce the water content of the SC. When focusing on the effect of the moisturizers on the three different regions, it was observed that cells in the swelling region are most sensitive to the application of the moisturizers and that the change in SC thickness is most influenced by the change in the thickness of the swelling region. Summarizing, SC cells are not equally sensitive to moisturizer application: centrally located corneocytes are more sensitive than corneocytes in the upper and the lowest regions of the SC.

Investigation of conditions involved in the susceptibility of the dermatophyte Trichophyton rubrum to photodynamic treatment

Abstract: Objectives and methods: The objective of this study was to investigate the key factors involved in PDT efficacy of both photosensitizers in an ex vivo situation during different fungal growth stages using a recently developed ex vivo model. The study focused on the influence of pH and ion strength of incubation media, photochemical properties of the photosensitizers (spectra and singlet oxygen production), and the effect of several scavengers of reactive oxygen species (sodium azide, histidine, mannitol) and phenylmethylsulphonylfluoride (keratinase inhibitor) on the PDT efficacy. Results and conclusions: The results show that an optimal pH and low concentrations of calcium are crucial for a selective binding of Sylsens B to the fungus, leading to an increased PDT efficacy. This selective binding to T. rubrum cannot be accomplished for DP mme. It can be concluded that the prerequisite for successful treatment is a use of a low molarity solution of pH 5, supplemented with a chelating agent and a keratinase activity-repressing agent. Under these conditions, PDT with Sylsens B inactivates, initially via singlet oxygen, effectively the fungus in different fungal growth stages.

Interaction of Lipophilic Moisturizers on Stratum Corneum Lipid Domains in vitro and in vivo

Abstract: Dry skin symptoms such as scaling and itching are often treated with lipophilic moisturizers. The aim of this study was to investigate the effect of lipophilic moisturizers on the stratum corneum (SC) ultra-structure and lipid organization. Lipophilic moisturizers were applied on the forearms of 4 healthy volunteers for 3 h. Subsequently, the application sites were tape stripped, and selected tape strips prepared for Freeze Fracture Electron Microscopy (FFEM), a method to visualize the SC intercellular lipid parallel to the skin surface. To investigate the effect of lipid moisturizers on the lipid lamellae, isolated SC was pretreated with the lipophilic moisturizers for 24 h prior to performing small angle X-ray diffraction (SAXD) measurements. Additionally, the lipid organization of mixtures prepared with ceramides, cholesterol, free fatty acids and lipophilic moisturizer in a 2:1:1:1 molar ratio were studied using SAXD. The FFEM data (in vivo) as well as the SAXD data (in vitro) show that the lipophilic moisturizers do not change the lipid lamellar organization in the SC. Addition of 20% m/m lipophilic moisturizer to the ceramide:cholesterol:free fatty acids mixture did not inhibit the formation of the long periodicity phase, the characteristic lamellar phase in the SC, even though there was clear evidence that two of the three moisturizers were at least partially incorporated in the long periodicity phase. Concluding, all findings suggest that the lipophilic moisturizers investigated in this study do not drastically change the lamellar organization of the SC intracellular lipid matrix, but that the moisturizers form separate domains in the SC, as was visualized by FFEM.

Skin Hydration - A Key Determinant in Topical Absorption

Abstract: BIOCHEMICAL ASPECTS ASSOCIATED WITH SKIN HYDRATION SC water content is dependent on four key processes: SC water binding, SC barrier properties, water gradient across the SC, and viable epidermal SC transporter function (Fig. 1). Products seeking to hydrate the SC on application to the skin generally seek to modify one of the first three processes.