The human basophil -a novel target of the neuropeptide alphamelanocyte-stimulating hormone There ... more The human basophil -a novel target of the neuropeptide alphamelanocyte-stimulating hormone There is increasing evidence that the basophil does not only play an important role in acute allergic reactions but also in the pathogenesis of chronic allergic disorders. Here we show that human basophils express melanocortin receptors (MC-Rs) and respond to alpha-melanocyte-stimulating hormone (alpha-MSH) with regulation of proallergic cytokine expression and modulation of basophil activation markers. Using primers against all known MC-R subtypes we demonstrate that the human basophil cell line KU812 expresses MC-1R. Expression of MC-1R on the surface of KU812 cells was confirmed by FACS analysis using an anti-MC-1R antibody. The MC-1R expressed by KU812 cells was functionally active as alpha-MSH induced intracellular cAMP in a dose-dependent manner. Moreover, alpha-MSH abrogated the effect of calcium ionophore A23187 on IL-4 mRNA expression in these cells. The relevance of the above findings was corroborated by showing that MC-1R surface expression is also detectable in basophils of leukocyte suspensions derived from whole human blood. Most interestingly, alpha-MSH was capable of suppressing the inductive effect of fMLP on surface expression of the basophil activation marker CD63 in leukocyte suspensions of atopic individuals. Likewise, alpha-MSH significantly blocked grass pollen-induced up-regulation of CD63 in leukocyte suspensions of patients with grass pollen allergy. Our findings highlight a novel functional dimension of alpha-MSH. In addition, MSH peptides may become a novel future therapeutic avenue in treating human allergic diseases.
We report here on the application of laser-based single molecule total internal reflection fluore... more We report here on the application of laser-based single molecule total internal reflection fluorescence microscopy (TIRFM) to study the penetration of molecules through the skin. Penetration of topically applied drug molecules is often observed to be limited by the size of the respective drug. However, the molecular mechanisms which govern the penetration of molecules through the outermost layer of the skin are still largely unknown. As a model compound we have chosen a larger amphiphilic molecule (fluorescent dye ATTO-Oxa12) with a molecular weight >700 Da that was applied to excised human skin. ATTO-Oxa12 penetrated through the stratum corneum (SC) into the viable epidermis as revealed by TIRFM of cryosections. Single particle tracking of ATTO-Oxa12 within SC sheets obtained by tape stripping allowed us to gain information on the localization as well as the lateral diffusion dynamics of these molecules. ATTO-Oxa12 appeared to be highly confined in the SC lipid region between (i...
Although conventional vaccines have generated major successes in the control of infectious diseas... more Although conventional vaccines have generated major successes in the control of infectious diseases, several obstacles remain in their development against chronic diseases (HIV, tuberculosis), against which no current candidate vaccines yet ensure protection. The transcutaneous route of vaccine administration appears to be a promising approach of targeting vaccines toward antigen-presenting cells (APCs) and thus improving immune responses. We investigated the suitability of nanoparticles in this approach. We found a high density of Langerhans cells (LCs) around hair follicles that, when sorted, readily internalized all size particles. However, flow cytometry after transcutaneous application of 40, 750, or 1,500 nm nanoparticles on human skin samples revealed that only 40 nm particles entered epidermal LC. Fluorescence and laser scan microscopies, which were carried out to identify the penetration pathway of transcutaneously applied nanoparticles, revealed that only 40 nm particles d...
The journal of investigative dermatology. Symposium proceedings / the Society for Investigative Dermatology, Inc. [and] European Society for Dermatological Research, 2005
The penetration of topically applied compounds varies considerably in the different regions of th... more The penetration of topically applied compounds varies considerably in the different regions of the human body. The presence of hair follicles significantly contributes to this effect by an increase in surface area and a disruption of the epidermal barrier towards the lower parts of the hair follicle. The human hair follicle, hereby, serves not only as a reservoir, but also as a major entry point for topically applied compounds. Topical delivery of active compounds to specific targets within the skin may help reduce side-effects caused by unspecific reactions, and may help develop new strategies in the prevention and treatment of skin diseases. Various drug carrier and drug delivery systems are currently being investigated. The aim of these investigational efforts is to direct topically applied compounds to the different types of hair follicles and, ideally, to specific compartments and cell populations within the hair follicles. Follicular targeting offers opportunities for new deve...
The development of extensive and severe non-melanoma skin cancer is an extremely common complicat... more The development of extensive and severe non-melanoma skin cancer is an extremely common complication of organ transplantation and is assumed to be caused by long-term treatment with anti-rejection drugs (ARD). Despite this florid clinical problem, ARD treatments have been reported to affect experimental murine skin carcinogenesis only weakly. We report here that treatment of cesium-137-irradiated Ptch1+/- mice with immunosuppressive doses of cyclosporine A plus prednisolone for 4-1/2 mo increased basal cell carcinoma burden by 2.5-fold. Thus, these mice provide a good model for study of the effects of long-term administration of ARD on at least one type of non-melanoma skin cancer.
The Journal of experimental medicine, Jan 15, 2004
Basal cell carcinomas (BCCs) are driven by abnormal hedgehog signaling and highly overexpress sev... more Basal cell carcinomas (BCCs) are driven by abnormal hedgehog signaling and highly overexpress several hedgehog target genes. We report here our use of one of these target genes, hedgehog-interacting protein (Hip1), as a tumor-associated antigen for immunoprevention of BCCs in Ptch1+/- mice treated with ionizing radiation. Hip1 mRNA is expressed in adult mouse tissues at levels considerably lower than those in BCCs. Immunization with either of two large recombinant Hip1 polypeptides was well tolerated in Ptch1+/- mice, induced B and T cell responses detectable by enzyme-linked immunosorbent assay, Western blot, delayed type hypersensitivity, and enzyme-linked immunospot assay, and reduced the number of BCCs by 42% (P < 0.001) and 32% (P < 0.01), respectively. We conclude that immunization with proteins specifically up-regulated by hedgehog signaling may hold promise as a preventive option for patients such as those with the basal cell nevus syndrome who are destined to develop ...
Recent advances in molecular and cell biology have led to increased understanding of hair formati... more Recent advances in molecular and cell biology have led to increased understanding of hair formation, hair growth, and cycling. Follicular pigmentation processes, neuroendocrine regulation, immune status, and follicular stem cell research in addition to the development of techniques to specifically target the hair follicle will help advance new therapeutic approaches in the management of hair diseases. In this article we review general aspects of hair biology, recent developments regarding hormonal regulation and pigmentation, the possible roles of the follicular immune system, advances in follicular stem cell research, and follicular penetration in view of their clinical relevance.
We report a 5-year-old boy presenting with multiple elastic type nevi and osteopoikilosis who was... more We report a 5-year-old boy presenting with multiple elastic type nevi and osteopoikilosis who was diagnosed as having Buschke-Ollendorff syndrome at an early age. Connective tissue lesions may present as the main symptom of varying clinical entities with different outcomes. Differential diagnosis includes papular elastorrhexis, fibroelastolytic papules of the neck, papular acne scars, and late onset focal dermal elastosis. Rare genodermatoses, i.e. Buschke-Ollendorff syndrome, pseudoxanthoma elasticum, juvenile hyaline fibromatosis and familiar cutaneous collagenoma should be carefully evaluated to provide appropriate genetic counseling and to avoid unnecessary treatment procedures.
Die androgenetische Alopezie (AGA), eine der häufigsten Ursachen für Haarausfall, führt bei viele... more Die androgenetische Alopezie (AGA), eine der häufigsten Ursachen für Haarausfall, führt bei vielen Betroffenen unabhängig von Ausprägung, Alter oder Geschlecht zu einem enormen psychosozialen Leidensdruck und einer nachhaltigen Beeinflussung der Lebensqualität. Eine differenzierte und standardisierte Diagnostik der AGA stellt bei Frauen, Männern und Jugendlichen eine essenzielle Grundlage für die Entwicklung eines erfolgreichen therapeutischen Konzepts dar. Behandlungsoptionen reichen von topischen und systemischen Pharmazeutika über kosmetische Produkte, Nutrikosmetika, Haartransplantationen zu ästhetisch korrektiven Ansätzen. Es obliegt der gemeinsamen Entscheidung von Arzt und Patient, die beste individuell adaptierte Therapie nach Abwägung von zu erwartendem Ergebnis, Umsetzbarkeit und Compliance auszuwählen. Ein notwendiges interdisziplinäres Vorgehen erfolgt individuell, abhängig von weiteren Befunden genauso wie die Entwicklung von Coping-Strategien und die Entscheidung für p...
European Journal of Pharmaceutics and Biopharmaceutics, 2014
Bacterial infections decreased considerably after the discovery of antibiotics. Nevertheless, bec... more Bacterial infections decreased considerably after the discovery of antibiotics. Nevertheless, because of the rising rate of infections caused by antibiotic-resistant bacteria strains, the search for new bactericidal agents has again become a crucial topic in clinical medicine. Silver nanoparticles (AgNP) have a huge potential in dermatology and wound care management because of their ability to release silver ions (Ag(+) ions) in a prolonged and sustained way. However, negative effects of silver on the patient&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s cells should not be underestimated. Furthermore, it has been controversially discussed whether AgNP are responsible for nanoparticle-specific outcomes or not. In this study, we investigated the effects of AgNP on human skin keratinocytes (HaCaT) in order to better understand the mechanisms of cytotoxicity and to improve the use of this highly reactive biocide in wound healing. We found that most of the cells with internalized AgNP displayed the typical morphological signs of apoptosis. The cell viability assay (XTT) showed concentration-dependent toxic effects of the AgNP toward HaCaT cells. The generation of reactive oxygen species (ROS) induced by AgNP was investigated in cell suspensions by means of electron paramagnetic resonance (EPR) spectroscopy. In order to distinguish between the effects of Ag(+) ions released during AgNP storage and those of Ag(+) ions released after nanoparticle application, we compared AgNP stored under air (O2) with AgNP stored under argon (Ar). Dispersions of AgNP stored under Ar have a low content of Ag(+) ions because of the absence of oxygen which is needed for oxidative dissolution. The results show that Ag(+) ions released during particle storage are responsible for most of the ROS produced during 1h incubation with the cells. AgNP (Ar) also induced intracellular ROS but to a much smaller extent compared to AgNP (O2). These findings highlight the complexity of experiments to assess the toxicity of AgNP and suggest the possibility of reducing AgNP toxic effects by storing AgNP formulations and even silver-containing wound dressing under an inert gas atmosphere.
Purpose. The development of particle-based carriers for transepidermal drug delivery has become a... more Purpose. The development of particle-based carriers for transepidermal drug delivery has become a field of major interest in dermatology. In this study, we investigated the suitability of biodegradable poly-lactic acid (PLA) particles loaded with fluorescent dyes as carriers for transepidermal drug delivery. Methods. The penetration profiles of PLA particles (228 and 365 nm) and the release of dye from the particles were investigated in human skin explants using fluorescence microscopy, confocal laser scanning microscopy and flow cytometry. Results. PLA particles penetrated into 50% of the vellus hair follicles, reaching a maximal depth corresponding to the entry of the sebaceous gland in 12-15% of all observed follicles. The accumulation of particles in the follicular ducts was accompanied by the release of dye to the viable epidermis and its retention in the sebaceous glands for up to 24 h. Kinetic studies in vitro as well as in skin explants revealed, that, although stable in aqueous solution, destabilization of the particles and significant release of incorporated dye occurred upon contact with organic solvents and the skin surface. Conclusions. These results suggest that particles based on PLA polymers may be ideal carriers for hair follicle and sebaceous gland targeting.
The increasing interest and recent developments in nanotechnology pose previously unparalleled ch... more The increasing interest and recent developments in nanotechnology pose previously unparalleled challenges in understanding the effects of nanoparticles on living tissues. Despite significant progress in in vitro cell and tissue culture technologies, observations on particle distribution and tissue responses in whole organisms are still indispensable. In addition to a thorough understanding of complex tissue responses which is the domain of expert pathologists, the localization of particles at their sites of interaction with living structures is essential to complete the picture. In this review we will describe and compare different imaging techniques for localizing inorganic as well as organic nanoparticles in tissues, cells and subcellular compartments. The visualization techniques include well-established methods, such as standard light, fluorescence, transmission electron and scanning electron microscopy as well as more recent developments, such as light and electron microscopic autoradiography, fluorescence lifetime imaging, spectral imaging and linear unmixing, superresolution structured illumination, Raman microspectroscopy and X-ray microscopy. Importantly, all methodologies described allow for the simultaneous visualization of nanoparticles and evaluation of cell and tissue changes that are of prime interest for toxicopathologic studies. However, the different approaches vary in terms of applicability for specific particles, sensitivity, optical resolution, technical requirements and thus availability, and effects of labeling on particle properties. Specific bottle necks of each technology are discussed in detail. Interpretation of particle localization data from any of these techniques should therefore respect their specific merits and limitations as no single approach combines all desired properties.
In the past, it was assumed that the intercellular route was the only relevant penetration pathwa... more In the past, it was assumed that the intercellular route was the only relevant penetration pathway for topically applied substances. Recent results on follicular penetration obtained at the Center for Experimental and Applied Cutaneous Phys- iology, Charité - Universitätsmedizin Berlin, Germany, em- phasize that the hair follicles represent a highly relevant and efficient penetration pathway and reservoir for topically ap-
The investigation of nanoparticle interactions with tissues is complex. High levels of standardiz... more The investigation of nanoparticle interactions with tissues is complex. High levels of standardization, ideally testing of different material types in the same biological model, and combinations of sensitive imaging and detection methods are required. Here, we present our studies on nanoparticle interactions with skin, skin cells, and biological media. Silica, titanium dioxide and silver particles were chosen as representative examples for different types of skin exposure to nanomaterials, e.g., unintended environmental exposure (silica) versus intended exposure through application of sunscreen (titanium dioxide) or antiseptics (silver). Because each particle type exhibits specific physicochemical properties, we were able to apply different combinations of methods to examine skin penetration and cellular uptake, including optical microscopy, electron microscopy, X-ray microscopy on cells and tissue sections, flow cytometry of isolated skin cells as well as Raman microscopy on whole tissue blocks. In order to assess the biological relevance of such findings, cell viability and free radical production were monitored on cells and in whole tissue samples. The combination of technologies and the joint discussion of results enabled us to look at nanoparticle-skin interactions and the biological relevance of our findings from different angles.
Transcutaneous immunization (TCI) requires targeting of a maximum number of skin antigen-presenti... more Transcutaneous immunization (TCI) requires targeting of a maximum number of skin antigen-presenting cells as non-invasive as possible on small skin areas. In two clinical trials, we introduced cyanoacrylate skin surface stripping (CSSS) as a safe method for TCI. Here, using ex vivo human skin, we demonstrate that one CSSS procedure removed only 30% of stratum corneum, but significantly increased the penetration of 200 nm polystyrene particles deep into vellus and intermediate hair follicles from where they could not been retrieved by conventional tape stripping. Two subsequent CSSS had no striking additional effect. CSSS increased particle penetration in superficial stratum corneum and induced Langerhans cell activation. Formulation in amphiphilic ointment or massage did not substantially influences the interfollicular penetration profiles. Hair follicle (HF) targeting by CSSS could become a highly effective tool for TCI when combined with carrier-based delivery and is gaining new a...
The human basophil -a novel target of the neuropeptide alphamelanocyte-stimulating hormone There ... more The human basophil -a novel target of the neuropeptide alphamelanocyte-stimulating hormone There is increasing evidence that the basophil does not only play an important role in acute allergic reactions but also in the pathogenesis of chronic allergic disorders. Here we show that human basophils express melanocortin receptors (MC-Rs) and respond to alpha-melanocyte-stimulating hormone (alpha-MSH) with regulation of proallergic cytokine expression and modulation of basophil activation markers. Using primers against all known MC-R subtypes we demonstrate that the human basophil cell line KU812 expresses MC-1R. Expression of MC-1R on the surface of KU812 cells was confirmed by FACS analysis using an anti-MC-1R antibody. The MC-1R expressed by KU812 cells was functionally active as alpha-MSH induced intracellular cAMP in a dose-dependent manner. Moreover, alpha-MSH abrogated the effect of calcium ionophore A23187 on IL-4 mRNA expression in these cells. The relevance of the above findings was corroborated by showing that MC-1R surface expression is also detectable in basophils of leukocyte suspensions derived from whole human blood. Most interestingly, alpha-MSH was capable of suppressing the inductive effect of fMLP on surface expression of the basophil activation marker CD63 in leukocyte suspensions of atopic individuals. Likewise, alpha-MSH significantly blocked grass pollen-induced up-regulation of CD63 in leukocyte suspensions of patients with grass pollen allergy. Our findings highlight a novel functional dimension of alpha-MSH. In addition, MSH peptides may become a novel future therapeutic avenue in treating human allergic diseases.
We report here on the application of laser-based single molecule total internal reflection fluore... more We report here on the application of laser-based single molecule total internal reflection fluorescence microscopy (TIRFM) to study the penetration of molecules through the skin. Penetration of topically applied drug molecules is often observed to be limited by the size of the respective drug. However, the molecular mechanisms which govern the penetration of molecules through the outermost layer of the skin are still largely unknown. As a model compound we have chosen a larger amphiphilic molecule (fluorescent dye ATTO-Oxa12) with a molecular weight >700 Da that was applied to excised human skin. ATTO-Oxa12 penetrated through the stratum corneum (SC) into the viable epidermis as revealed by TIRFM of cryosections. Single particle tracking of ATTO-Oxa12 within SC sheets obtained by tape stripping allowed us to gain information on the localization as well as the lateral diffusion dynamics of these molecules. ATTO-Oxa12 appeared to be highly confined in the SC lipid region between (i...
Although conventional vaccines have generated major successes in the control of infectious diseas... more Although conventional vaccines have generated major successes in the control of infectious diseases, several obstacles remain in their development against chronic diseases (HIV, tuberculosis), against which no current candidate vaccines yet ensure protection. The transcutaneous route of vaccine administration appears to be a promising approach of targeting vaccines toward antigen-presenting cells (APCs) and thus improving immune responses. We investigated the suitability of nanoparticles in this approach. We found a high density of Langerhans cells (LCs) around hair follicles that, when sorted, readily internalized all size particles. However, flow cytometry after transcutaneous application of 40, 750, or 1,500 nm nanoparticles on human skin samples revealed that only 40 nm particles entered epidermal LC. Fluorescence and laser scan microscopies, which were carried out to identify the penetration pathway of transcutaneously applied nanoparticles, revealed that only 40 nm particles d...
The journal of investigative dermatology. Symposium proceedings / the Society for Investigative Dermatology, Inc. [and] European Society for Dermatological Research, 2005
The penetration of topically applied compounds varies considerably in the different regions of th... more The penetration of topically applied compounds varies considerably in the different regions of the human body. The presence of hair follicles significantly contributes to this effect by an increase in surface area and a disruption of the epidermal barrier towards the lower parts of the hair follicle. The human hair follicle, hereby, serves not only as a reservoir, but also as a major entry point for topically applied compounds. Topical delivery of active compounds to specific targets within the skin may help reduce side-effects caused by unspecific reactions, and may help develop new strategies in the prevention and treatment of skin diseases. Various drug carrier and drug delivery systems are currently being investigated. The aim of these investigational efforts is to direct topically applied compounds to the different types of hair follicles and, ideally, to specific compartments and cell populations within the hair follicles. Follicular targeting offers opportunities for new deve...
The development of extensive and severe non-melanoma skin cancer is an extremely common complicat... more The development of extensive and severe non-melanoma skin cancer is an extremely common complication of organ transplantation and is assumed to be caused by long-term treatment with anti-rejection drugs (ARD). Despite this florid clinical problem, ARD treatments have been reported to affect experimental murine skin carcinogenesis only weakly. We report here that treatment of cesium-137-irradiated Ptch1+/- mice with immunosuppressive doses of cyclosporine A plus prednisolone for 4-1/2 mo increased basal cell carcinoma burden by 2.5-fold. Thus, these mice provide a good model for study of the effects of long-term administration of ARD on at least one type of non-melanoma skin cancer.
The Journal of experimental medicine, Jan 15, 2004
Basal cell carcinomas (BCCs) are driven by abnormal hedgehog signaling and highly overexpress sev... more Basal cell carcinomas (BCCs) are driven by abnormal hedgehog signaling and highly overexpress several hedgehog target genes. We report here our use of one of these target genes, hedgehog-interacting protein (Hip1), as a tumor-associated antigen for immunoprevention of BCCs in Ptch1+/- mice treated with ionizing radiation. Hip1 mRNA is expressed in adult mouse tissues at levels considerably lower than those in BCCs. Immunization with either of two large recombinant Hip1 polypeptides was well tolerated in Ptch1+/- mice, induced B and T cell responses detectable by enzyme-linked immunosorbent assay, Western blot, delayed type hypersensitivity, and enzyme-linked immunospot assay, and reduced the number of BCCs by 42% (P < 0.001) and 32% (P < 0.01), respectively. We conclude that immunization with proteins specifically up-regulated by hedgehog signaling may hold promise as a preventive option for patients such as those with the basal cell nevus syndrome who are destined to develop ...
Recent advances in molecular and cell biology have led to increased understanding of hair formati... more Recent advances in molecular and cell biology have led to increased understanding of hair formation, hair growth, and cycling. Follicular pigmentation processes, neuroendocrine regulation, immune status, and follicular stem cell research in addition to the development of techniques to specifically target the hair follicle will help advance new therapeutic approaches in the management of hair diseases. In this article we review general aspects of hair biology, recent developments regarding hormonal regulation and pigmentation, the possible roles of the follicular immune system, advances in follicular stem cell research, and follicular penetration in view of their clinical relevance.
We report a 5-year-old boy presenting with multiple elastic type nevi and osteopoikilosis who was... more We report a 5-year-old boy presenting with multiple elastic type nevi and osteopoikilosis who was diagnosed as having Buschke-Ollendorff syndrome at an early age. Connective tissue lesions may present as the main symptom of varying clinical entities with different outcomes. Differential diagnosis includes papular elastorrhexis, fibroelastolytic papules of the neck, papular acne scars, and late onset focal dermal elastosis. Rare genodermatoses, i.e. Buschke-Ollendorff syndrome, pseudoxanthoma elasticum, juvenile hyaline fibromatosis and familiar cutaneous collagenoma should be carefully evaluated to provide appropriate genetic counseling and to avoid unnecessary treatment procedures.
Die androgenetische Alopezie (AGA), eine der häufigsten Ursachen für Haarausfall, führt bei viele... more Die androgenetische Alopezie (AGA), eine der häufigsten Ursachen für Haarausfall, führt bei vielen Betroffenen unabhängig von Ausprägung, Alter oder Geschlecht zu einem enormen psychosozialen Leidensdruck und einer nachhaltigen Beeinflussung der Lebensqualität. Eine differenzierte und standardisierte Diagnostik der AGA stellt bei Frauen, Männern und Jugendlichen eine essenzielle Grundlage für die Entwicklung eines erfolgreichen therapeutischen Konzepts dar. Behandlungsoptionen reichen von topischen und systemischen Pharmazeutika über kosmetische Produkte, Nutrikosmetika, Haartransplantationen zu ästhetisch korrektiven Ansätzen. Es obliegt der gemeinsamen Entscheidung von Arzt und Patient, die beste individuell adaptierte Therapie nach Abwägung von zu erwartendem Ergebnis, Umsetzbarkeit und Compliance auszuwählen. Ein notwendiges interdisziplinäres Vorgehen erfolgt individuell, abhängig von weiteren Befunden genauso wie die Entwicklung von Coping-Strategien und die Entscheidung für p...
European Journal of Pharmaceutics and Biopharmaceutics, 2014
Bacterial infections decreased considerably after the discovery of antibiotics. Nevertheless, bec... more Bacterial infections decreased considerably after the discovery of antibiotics. Nevertheless, because of the rising rate of infections caused by antibiotic-resistant bacteria strains, the search for new bactericidal agents has again become a crucial topic in clinical medicine. Silver nanoparticles (AgNP) have a huge potential in dermatology and wound care management because of their ability to release silver ions (Ag(+) ions) in a prolonged and sustained way. However, negative effects of silver on the patient&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s cells should not be underestimated. Furthermore, it has been controversially discussed whether AgNP are responsible for nanoparticle-specific outcomes or not. In this study, we investigated the effects of AgNP on human skin keratinocytes (HaCaT) in order to better understand the mechanisms of cytotoxicity and to improve the use of this highly reactive biocide in wound healing. We found that most of the cells with internalized AgNP displayed the typical morphological signs of apoptosis. The cell viability assay (XTT) showed concentration-dependent toxic effects of the AgNP toward HaCaT cells. The generation of reactive oxygen species (ROS) induced by AgNP was investigated in cell suspensions by means of electron paramagnetic resonance (EPR) spectroscopy. In order to distinguish between the effects of Ag(+) ions released during AgNP storage and those of Ag(+) ions released after nanoparticle application, we compared AgNP stored under air (O2) with AgNP stored under argon (Ar). Dispersions of AgNP stored under Ar have a low content of Ag(+) ions because of the absence of oxygen which is needed for oxidative dissolution. The results show that Ag(+) ions released during particle storage are responsible for most of the ROS produced during 1h incubation with the cells. AgNP (Ar) also induced intracellular ROS but to a much smaller extent compared to AgNP (O2). These findings highlight the complexity of experiments to assess the toxicity of AgNP and suggest the possibility of reducing AgNP toxic effects by storing AgNP formulations and even silver-containing wound dressing under an inert gas atmosphere.
Purpose. The development of particle-based carriers for transepidermal drug delivery has become a... more Purpose. The development of particle-based carriers for transepidermal drug delivery has become a field of major interest in dermatology. In this study, we investigated the suitability of biodegradable poly-lactic acid (PLA) particles loaded with fluorescent dyes as carriers for transepidermal drug delivery. Methods. The penetration profiles of PLA particles (228 and 365 nm) and the release of dye from the particles were investigated in human skin explants using fluorescence microscopy, confocal laser scanning microscopy and flow cytometry. Results. PLA particles penetrated into 50% of the vellus hair follicles, reaching a maximal depth corresponding to the entry of the sebaceous gland in 12-15% of all observed follicles. The accumulation of particles in the follicular ducts was accompanied by the release of dye to the viable epidermis and its retention in the sebaceous glands for up to 24 h. Kinetic studies in vitro as well as in skin explants revealed, that, although stable in aqueous solution, destabilization of the particles and significant release of incorporated dye occurred upon contact with organic solvents and the skin surface. Conclusions. These results suggest that particles based on PLA polymers may be ideal carriers for hair follicle and sebaceous gland targeting.
The increasing interest and recent developments in nanotechnology pose previously unparalleled ch... more The increasing interest and recent developments in nanotechnology pose previously unparalleled challenges in understanding the effects of nanoparticles on living tissues. Despite significant progress in in vitro cell and tissue culture technologies, observations on particle distribution and tissue responses in whole organisms are still indispensable. In addition to a thorough understanding of complex tissue responses which is the domain of expert pathologists, the localization of particles at their sites of interaction with living structures is essential to complete the picture. In this review we will describe and compare different imaging techniques for localizing inorganic as well as organic nanoparticles in tissues, cells and subcellular compartments. The visualization techniques include well-established methods, such as standard light, fluorescence, transmission electron and scanning electron microscopy as well as more recent developments, such as light and electron microscopic autoradiography, fluorescence lifetime imaging, spectral imaging and linear unmixing, superresolution structured illumination, Raman microspectroscopy and X-ray microscopy. Importantly, all methodologies described allow for the simultaneous visualization of nanoparticles and evaluation of cell and tissue changes that are of prime interest for toxicopathologic studies. However, the different approaches vary in terms of applicability for specific particles, sensitivity, optical resolution, technical requirements and thus availability, and effects of labeling on particle properties. Specific bottle necks of each technology are discussed in detail. Interpretation of particle localization data from any of these techniques should therefore respect their specific merits and limitations as no single approach combines all desired properties.
In the past, it was assumed that the intercellular route was the only relevant penetration pathwa... more In the past, it was assumed that the intercellular route was the only relevant penetration pathway for topically applied substances. Recent results on follicular penetration obtained at the Center for Experimental and Applied Cutaneous Phys- iology, Charité - Universitätsmedizin Berlin, Germany, em- phasize that the hair follicles represent a highly relevant and efficient penetration pathway and reservoir for topically ap-
The investigation of nanoparticle interactions with tissues is complex. High levels of standardiz... more The investigation of nanoparticle interactions with tissues is complex. High levels of standardization, ideally testing of different material types in the same biological model, and combinations of sensitive imaging and detection methods are required. Here, we present our studies on nanoparticle interactions with skin, skin cells, and biological media. Silica, titanium dioxide and silver particles were chosen as representative examples for different types of skin exposure to nanomaterials, e.g., unintended environmental exposure (silica) versus intended exposure through application of sunscreen (titanium dioxide) or antiseptics (silver). Because each particle type exhibits specific physicochemical properties, we were able to apply different combinations of methods to examine skin penetration and cellular uptake, including optical microscopy, electron microscopy, X-ray microscopy on cells and tissue sections, flow cytometry of isolated skin cells as well as Raman microscopy on whole tissue blocks. In order to assess the biological relevance of such findings, cell viability and free radical production were monitored on cells and in whole tissue samples. The combination of technologies and the joint discussion of results enabled us to look at nanoparticle-skin interactions and the biological relevance of our findings from different angles.
Transcutaneous immunization (TCI) requires targeting of a maximum number of skin antigen-presenti... more Transcutaneous immunization (TCI) requires targeting of a maximum number of skin antigen-presenting cells as non-invasive as possible on small skin areas. In two clinical trials, we introduced cyanoacrylate skin surface stripping (CSSS) as a safe method for TCI. Here, using ex vivo human skin, we demonstrate that one CSSS procedure removed only 30% of stratum corneum, but significantly increased the penetration of 200 nm polystyrene particles deep into vellus and intermediate hair follicles from where they could not been retrieved by conventional tape stripping. Two subsequent CSSS had no striking additional effect. CSSS increased particle penetration in superficial stratum corneum and induced Langerhans cell activation. Formulation in amphiphilic ointment or massage did not substantially influences the interfollicular penetration profiles. Hair follicle (HF) targeting by CSSS could become a highly effective tool for TCI when combined with carrier-based delivery and is gaining new a...
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Papers by Annika Vogt