Arrangement of ceramide [EOS] in a stratum corneum lipid model matrix: new aspects revealed by neutron diffraction studies.

The lipid matrix in stratum corneum (SC) plays a key role in the barrier function of the mammalian skin. The major lipids are ceramides (CER), cholesterol (CHOL) and free fatty acids (FFA). Especially the unique-structured omega-acylceramide CER[EOS] is regarded to be essential for skin barrier properties by inducing the formation of a long-periodicity phase of 130 angstroms (LPP).

Localisation of partially deuterated cholesterol in quaternary SC lipid model membranes: a neutron diffraction study.

This letter presents our first results in using the benefit of selective deuteration in neutron diffraction studies on stratum corneum (SC) lipid model systems. The SC represents the outermost layer of the mammalian skin and exhibits the main skin barrier. It is essential for studying drug penetration through the SC to know the internal structure and hydration behaviour on the molecular level.

Properties of ceramides and their impact on the stratum corneum structure. Part 2: stratum corneum lipid model systems.

The stratum corneum (SC) represents the outermost layer of the mammalian skin, exhibits the main skin barrier and plays an important role in the water penetration pathway through the SC. Knowing the structure and properties of the SC at the molecular level is essential for studying drug penetration through the SC and for the development of new dermal drug delivery systems. Therefore, research interest is focused on the SC lipid matrix and on water diffusion through it.

Properties of ceramides and their impact on the stratum corneum structure: a review. Part 1: ceramides.

The lipid matrix of the stratum corneum (SC) is the major diffusion-rate-limiting pathway by which most drugs intracellularly pass the SC. The major lipid classes extracted from the SC are ceramides, cholesterol and free fatty acids. Ceramides that comprise nine subclasses play a crucial role in maintaining the barrier function of the skin.

Sublimation of antimycotic agents as proved by various analytical methods.

Qualitative and quantitative results demonstrate that the pure substances amorolfine base, amorolfine hydrochloride, two selected morpholine derivatives and terbinafine hydrochloride are clearly able to sublimate. As amorolfine hydrochloride is also capable to sublimate from galencial forms laquer and cream in this experimental setup, a clinical relevance of sublimation phenomenon at least for topical treatment of onychomycosis has to be considered. This phenomenon could be one reason for advantageous clinical and mycological cure rates of amorolfine nail laquer to comparable topical products reported in the literature.

Different physicochemical properties of antimycotic agents are relevant for penetration into and through human nails.

This article reports the characterization of the physicochemical properties of two important antifungal topical drugs, amorolfine and ciclopirox. Furthermore, the release of the drugs from commercial lacquer formulations for treatment of onychomycosis was studied using the online FTIR-ATR technique. Based on the physicochemical background of these two drugs and their release from commercial lacquer formulations for treatment of onychomycosis, the suitability of these drugs for optimized local antifungal therapy to human nails is discussed.

Normal mode analysis of gamma form of oleic acid.

Oleic acid is one of the major components of a variety of oils and its spectra are very complex due to the presence of a large number of conformational states (alpha, beta, gamma). In the present communication, an attempt has been made to unravel the complex spectra by calculating the normal modes and examining the spectral features such as line position, line width, band intensity, group frequency concept and spectral relationship between the finite and infinite systems.

Influence of phytosphingosine-type ceramides on the structure of DMPC membrane.

The present paper describes the influence of the ceramides with phytosphingosine base, N-stearoylphytosphingosine (Cer[NP]) and alpha-hydroxy-N-stearoylphytosphingosine (Cer[AP]), on the structure and properties of multilamellar (MLVs) and unilamellar vesicles (ULVs) of dimyristoylphosphatidylcholine (DMPC). The lamellar repeat distance, D, has been measured at various temperatures using small angle X-ray diffraction. The incorporation of ceramides into the DMPC membrane causes larger D compared to pure DMPC membrane.

Studies of the retrogradation process for various starch gels using Raman spectroscopy.

The retrogradation of untreated wild-type starches (potato, maize, and wheat), waxy maize starches, and one pregelatinized, modified amylose-rich starch was investigated continuously using Raman spectroscopy. The method detects conformational changes due to the multi-stage retrogradation, the rate of which differs between the starches. The pregelatinized, modified amylose-rich starch shows all stages of retrogradation in the course of its Raman spectra.

Solid lipid nanoparticles (SLN) and oil-loaded SLN studied by spectrofluorometry and Raman spectroscopy.

Purpose: Recently, colloidal dispersions made of mixtures from solid and liquid lipids have been described to overcome the poor drug loading capacity of solid lipid nanoparticles (SLN). It has been proposed that these nanostructured lipid carriers (NLC) are composed of oily droplets, which are embedded in a solid lipid matrix. High loading capacities and controlled release characteristics have been claimed.

New insights into the structure and hydration of a stratum corneum lipid model membrane by neutron diffraction.

The structure and hydration of a stratum corneum (SC) lipid model membrane composed of N-(alpha-hydroxyoctadecanoyl)-phytosphingosine (CER6)/cholesterol (Ch)/palmitic acid (PA)/cholesterol sulfate (ChS) were characterized by neutron diffraction. The neutron scattering length density across the SC lipid model membrane was calculated from measured diffraction peak intensities. The internal membrane structure and water distribution function across the bilayer were determined.

Interaction of water with different cellulose ethers: a Raman spectroscopy and environmental scanning electron microscopy study.

Different non-ionic cellulose ethers like methyl cellulose (MC), hydroxypropyl cellulose (HPC) and hydroxypropylmethyl cellulose (HPMC) were investigated. The characterization of the cellulose ethers was carried out by thermogravimetry and sorption/desorption isotherms. Differences in the properties of the cellulose ether films were described by time-dependent contact angle measurements.

Hydration properties of N-(alpha-hydroxyacyl)-sphingosine: X-ray powder diffraction and FT-Raman spectroscopic studies.

The thermotropic properties of N-(alpha-hydroxyacyl)-sphingosine (CER[AS]) in dry and hydrated state were studied by means of X-ray powder diffraction and FT-Raman spectroscopy. The polymorphic states of the CER[AS]/water mixture (lamellar crystalline, lamellar hexagonal gel, liquid crystalline) depend on the thermal pre-treatment of the sample. Only by heating the CER[AS]/water mixture above the melting chain transition can the system be hydrated.

Pharmaceutical applications of Mid-IR and Raman spectroscopy.

Mid-IR and Raman spectroscopy are versatile tools in pharmaceutics and biopharmaceutics, with a wide field of applications ranging from characterization of drug formulations to elucidation of kinetic processes in drug delivery. After an introduction to the basic principles of IR and Raman spectroscopy, new developments in applications of these methods for studying drug delivery systems, in particular topical drug delivery, will be reviewed. FTIR-ATR is a well-established standard method used to study drug release in semisolid formulations, drug penetration, and influence of penetration modifiers; it is also capable of in vivo studies.

Polymorphism of ceramide 6: a vibrational spectroscopic and X-ray powder diffraction investigation of the diastereomers of N-(alpha-hydroxyoctadecanoyl)-phytosphingosine.

A preparative chromatographic method was developed for the quantitative isolation of the diastereomers of synthetic N-(alpha-hydroxyoctadecanoyl)-phytosphingosine (DL-CER6). The L- and the D-compound were studied each by means X-ray powder diffraction, FT-Raman and FT-IR spectroscopy. The diastereomers exhibit different thermotropic polymorphism.

A new FTIR-ATR cell for drug diffusion studies.

The drug diffusion of most compounds, particularly hydrophilic molecules through the skin is limited by the permeation of the outermost cell layers of the epidermis, the stratum corneum(SC). For this reason it is of interest to characterize drug diffusion processes through this skin layer. A new FTIR-ATR cell was developed for non-invasive real time measurements of drug diffusion.

Properties of microcrystalline cellulose and powder cellulose after extrusion/spheronization as studied by fourier transform Raman spectroscopy and environmental scanning electron microscopy.

In this study, the effect of powder cellulose (PC) and 2 types of microcrystalline cellulose (MCC 101 and MCC 301) on pellet properties produced by an extrusion/spheronization process was investigated. The different investigated types of cellulose displayed different behavior during the extrusion/spheronization process. Pure PC was unsuitable for extrusion, because too much water was required and the added water was partly squeezed during the extrusion process.

Phase behaviour of transkarbam 12.

Transkarbam 12 (T12), the carbamic acid salt of omega-aminocaproic acid dodecyl ester, is a recently synthesized substance, whose high permeation enhancing activity through the human skin was found for certain drugs. In this work, the thermotropic phase behaviour of T12 has been studied by means of various techniques, namely, DSC, FTIR and FT-Raman spectroscopy, X-ray powder diffraction, and DRS. The temperature development of the X-ray reflections as well as of the conformationally sensitive Raman bands and the IR bands have been observed.

Potential of carrageenans to protect drugs from polymorphic transformation.

Carrageenans were analysed in mixture with polymorphic drugs to test their potential for minimising polymorphic or pseudopolymorphic transitions, which are induced by the tableting process. The kappa-carrageenans Gelcarin GP-812 NF and Gelcarin GP-911 NF and the iota-carrageenan Gelcarin GP-379 NF were tested in comparison to the well-known tableting excipients microcrystalline cellulose (MCC), hydroxypropyl methylcellulose (HPMC), and dicalcium phosphate dihydrate (DCPD). Amorphous indomethacin was chosen as model drug since its well-known recrystallisation behaviour can be mechanically stimulated.

Polymorphism of ceramide 3. Part 2: a vibrational spectroscopic and X-ray powder diffraction investigation of N-octadecanoyl phytosphingosine and the analogous specifically deuterated d(35) derivative.

In order to characterize the arrangements of the hydrocarbon chains of ceramide 3, the thermotropic phase behaviour of the ceramides N-octadecanoylphytosphingosine (CER3) and its chain deuterated derivative N-(d(35)-octadecanoyl)phytosphingosine (d(35)CER3) was studied by means of X-ray powder diffraction, FT-IR and Raman spectroscopy. CER3 and d(35)CER3 exhibit an identical thermotropic polymorphism involving three different crystalline phases. The selective deuteration of the fatty acid chain enables to distinguish the sphingoid part from the fatty acid part by means of FT-IR and Raman spectroscopy.

Physicochemical characterization of silicon-containing glycolipids by DSC, FT-Raman spectroscopy and X-ray diffraction.

Derivatives of dimethylalkylchlorosilanes are novel substances which may be used in formulations for drug targeting. In order to design their properties it is essential to perform physicochemical characterization. For this purpose, a combination of differential scanning calorimetry (DSC), FT-Raman spectroscopy and X-ray diffraction is well suited.

Does sucrose influence the properties of DMPC vesicles?

Small-angle neutron and X-ray scattering, dynamic light scattering, X-ray diffraction coupled with differential scanning calorimetry, and Raman spectroscopy were applied to investigate unilamellar (ULVs) and multilamellar (MLVs) dimyristoylphosphatidylcholine (DMPC) vesicles in aqueous sucrose solutions with sucrose concentrations from 0 to 60% w/w. In case of ULVs, the addition of sucrose decreases the polydispersity of vesicle population. A minimum value of polydispersity was found at 20% sucrose.

Polymorphism of ceramide 3. Part 1: an investigation focused on the head group of N-octadecanoylphytosphingosine.

The thermotropic phase behaviour of the ceramide N-octadecanoylphytosphingosine (CER3) was investigated using differential scanning calorimetry, X-ray powder diffraction and FT-IR spectroscopy. CER3 was shown to be a polymorphic substance depending on the crystallisation conditions. Three different solid states were found.

The effects of hyaluronan and its fragments on lipid models exposed to UV irradiation.

The effects of hyaluronan and its degradation products on irradiation-induced lipid peroxidation were investigated. Liposomal skin lipid models with increasing complexity were used. Hyaluronan and its fragments were able to reduce the amount of lipid peroxidation secondary products quantified by the thiobarbituric acid (TBA) assay.

Characterization of enzymatically digested hyaluronic acid using NMR, Raman, IR, and UV-Vis spectroscopies.

Hyaluronic acid (HA) is a linear polysaccharide formed from disaccharide units containing N-acetylglucosamine and glucuronic acid. When HA was digested with the enzyme hyaluronidase, a double bond is formed. It is known that this double bond forms a complex (radical scavenger) with the radicals (ROO, HO) during UV irradiation, and reduced the toxicity of the radicals before they are absorbed in the human skin.