Judith Kuntsche

Skin penetration enhancement by a microneedle device (Dermaroller®) in vitro: Dependency on needle size and applied formulation

This study focused on the in vitro evaluation of skin perforation using a new microneedle device (Dermaroller) with different needle lengths (150, 500 and 1500 microm). The influence of the microneedle treatment on the morphology of the skin surface (studied by light and scanning electron microscopy), on the transepidermal water loss (TEWL) and on the penetration and permeation of hydrophilic model drugs was investigated using excised human full-thickness skin. Furthermore, invasomes - highly flexible phospholipid vesicles containing terpenes and ethanol as penetration enhancer - were compared with an aqueous solution. Elevated TEWL values were measured after Dermaroller treatment compared to untreated human skin with a gradual increase of the TEWL over the first hour whereas afterwards the TEWL values decreased probably caused by a reduction of the pore size with time. Skin perforation with the Dermarollers enhanced drug penetration and permeation for both formulations tested. Invasomes were more effective to deliver hydrophilic compounds into and through the skin compared to the aqueous drug solutions and the combination with skin perforation further enhanced drug penetration and permeation. In conclusion, Dermarollers being already commercially available for cosmetic purposes appear also promising for drug delivery purposes particularly those with medium (500 microm) and shorter (150 microm) needle lengths.

Cryogenic transmission electron microscopy (cryo-TEM) for studying the morphology of colloidal drug delivery systems.

Cryogenic transmission electron microscopy (cryo-TEM) has evolved into an indispensable tool for the characterization of colloidal drug delivery systems. It can be applied to study the size, shape and internal structure of nanoparticulate carrier systems as well as the overall colloidal composition of the corresponding dispersions. This review gives a short overview over the instrumentation used in cryo-TEM experiments and over the sample preparation procedure. Selected examples of cryo-TEM studies on colloidal drug carrier systems, including liposomes, colloidal lipid emulsions, solid lipid nanoparticles, thermotropic and lyotropic liquid crystalline nanoparticles, polymer-based colloids and delivery systems for nucleic acids, are presented in order to illustrate the wealth of information that can be obtained by this technique.

Tumor Accumulation of NIR Fluorescent PEG PLA Nanoparticles: Impact of Particle Size and Human Xenograft Tumor Model

Cancer therapies are often terminated due to serious side effects of the drugs. The cause is the nonspecific distribution of chemotherapeutic agents to both cancerous and normal cells. Therefore, drug carriers which deliver their toxic cargo specific to cancer cells are needed. Size is one key parameter for the nanoparticle accumulation in tumor tissues. In the present study the influence of the size of biodegradable nanoparticles was investigated in detail, combining in vivo and ex vivo analysis with comprehensive particle size characterizations. Polyethylene glycol-polyesters poly(lactide) block polymers were synthesized and used for the production of three defined, stable, and nontoxic near-infrared (NIR) dye-loaded nanoparticle batches. Size analysis based on asymmetrical field flow field fractionation coupled with multiangle laser light scattering and photon correlation spectroscopy (PCS) revealed narrow size distribution and permitted accurate size evaluations. Furthermore, this study demonstrates the constraints of particle size data only obtained by PCS. By the multispectral analysis of the Maestro in vivo imaging system the in vivo fate of the nanoparticles next to their accumulation in special red fluorescent DsRed2 expressing HT29 xenografts could be followed. This simultaneous imaging in addition to confocal microscopy studies revealed information about the accumulation characteristics of nanoparticles inside the tumor tissues. This knowledge was further combined with extended size-dependent fluorescence imaging studies at two different xenograft tumor types, the HT29 (colorectal carcinoma) and the A2780 (ovarian carcinoma) cell lines. The combination of two different size measurement methods allowed the characterization of the dependence of nanoparticle accumulation in the tumor on even rather small differences in the nanoparticle size. While two nanoparticle batches (111 and 141 nm in diameter) accumulated efficiently in the human xenograft tumor tissue, the slightly bigger nanoparticles (diameter 166 nm) were rapidly eliminated by the liver.

Supercooled Smectic Nanoparticles: A Potential Novel Carrier System for Poorly Water Soluble Drugs

AbstractPurpose. The possibility of preparing nanoparticles in the supercooled thermotropic liquid crystalline state from cholesterol esters with saturated acyl chains as well as the incorporation of model drugs into the dispersions was investigated using cholesteryl myristate (CM) as a model cholesterol ester. Methods. Nanoparticles were prepared by high-pressure melt homogenization or solvent evaporation using phospholipids, phospholipid/bile salt, or polyvinyl alcohol as emulsifiers. The physicochemical state and phase behavior of the particles was characterized by particle size measurements (photon correlation spectroscopy, laser diffraction with polarization intensity differential scattering), differential scanning calorimetry, X-ray diffraction, and electron and polarizing light microscopy. The viscosity of the isotropic and liquid crystalline phases of CM in the bulk was investigated in dependence on temperature and shear rate by rotational viscometry. Results. CM nanoparticles can be obtained in the smectic phase and retained in this state for at least 12 months when stored at 23°C in optimized systems. The recrystallization tendency of CM in the dispersions strongly depends on the stabilizer system and the particle size. Stable drug-loaded smectic nanoparticles were obtained after incorporation of 10% (related to CM) ibuprofen, miconazole, etomidate, and 1% progesterone. Conclusions. Due to their liquid crystalline state, colloidal smectic nanoparticles offer interesting possibilities as carrier system for lipophilic drugs. CM nanoparticles are suitable model systems for studying the crystallization behavior and investigating the influence of various parameters for the development of smectic nanoparticles resistant against recrystallization upon storage.

How Stealthy are PEG-PLA Nanoparticles? An NIR In Vivo Study Combined with Detailed Size Measurements

ABSTRACTPurposeDetailed in vivo and ex vivo analysis of nanoparticle distribution, accumulation and elimination processes were combined with comprehensive particle size characterizations.MethodsThe in vivo fate of near infrared (NIR) nanoparticles in nude mice was carried out using the Maestro™ in vivo fluorescence imaging system. Asymmetrical field flow field fractionation (AF4) coupled with multi-angle laser light scattering (MALLS), photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM) were employed for detailed in vitro characterization.ResultsPEG-PLA block polymers were synthesized and used for the production of defined, stable, nontoxic nanoparticles. Nanoparticle analysis revealed narrow size distribution; AF4/MALLS permitted further accurate size evaluation. Multispectral fluorescence imaging made it possible to follow the in vivo fate non-invasively even in deep tissues over several days. Detailed fluorescence ex vivo imaging studies were performed and allowed to establish a calculation method to compare nanoparticle batches with varying fluorescence intensities.ConclusionWe combined narrow-size distributed nanoparticle batches with detailed in vitro characterization and the understanding of their in vivo fate using fluorescence imaging, confirming the wide possibilities of the non-invasive technique and presenting the basis to evaluate future size-dependent passive tumor accumulation studies.

Comparison of rat epidermal keratinocyte organotypic culture (ROC) with intact human skin: lipid composition and thermal phase behavior of the stratum corneum

The present report is a part of our continuing efforts to explore the utility of the rat epidermal keratinocyte organotypic culture (ROC) as an alternative model to human skin in transdermal drug delivery and skin irritation studies of new chemical entities and formulations. The aim of the present study was to compare the stratum corneum lipid content of ROC with the corresponding material from human skin. The lipid composition was determined by thin-layer chromatography (TLC) and mass-spectrometry, and the thermal phase transitions of stratum corneum were studied by differential scanning calorimetry (DSC). All major lipid classes of the stratum corneum were present in ROC in a similar ratio as found in human stratum corneum. Compared to human skin, the level of non-hydroxyacid-sphingosine ceramide (NS) was increased in ROC, while alpha-hydroxyacid-phytosphingosine ceramide (AP) and non-hydroxyacid-phytosphingosine ceramides (NP) were absent. Also some alterations in fatty acid profiles of ROC ceramides were noted, e.g., esterified omega-hydroxyacid-sphingosine contained increased levels of oleic acid instead of linoleic acid. The fraction of lipids covalently bound to corneocyte proteins was distinctly lower in ROC compared to human skin, in agreement with the results from DSC. ROC underwent a lipid lamellar order to disorder transition (T2) at a slightly lower temperature (68 degrees C) than human skin (74 degrees C). These differences in stratum corneum lipid composition and the thermal phase transitions may explain the minor differences previously observed in drug permeation between ROC and human skin.

Interaction of dispersed cubic phases with blood components

The interaction of aqueous nanoparticle dispersions, e.g. based on monoolein/poloxamer 407, with blood components is an important topic concerning especially the parenteral way of administration. Therefore, the influence of human and porcine plasma on dispersed cubic phases was investigated. Particle size measurements of mixtures with plasma indicated a decrease in particle size. In cryo-transmission electron micrographs, different structures could be found, which arose from the dispersed cubic phases under plasma contact. Non-cubic structures on the particle surface were decomposed first. Several phase transitions with the formation of smaller and sometimes larger particle fractions were observed beside remaining cubic structures. A very low but detectable hemolytic activity was found for the dispersed cubic phases based on monoolein and poloxamer 407, when compared to the hemolytic activity of cubic phases based on monoolein and poloxamer 188, on soy phosphatidylcholine, glycerol dioleate and polysorbate 80 or the parenteral fat emulsion Lipofundin MCT 20%.

Poly(glycerol adipate)-fatty acid esters as versatile nanocarriers: From nanocubes over ellipsoids to nanospheres

Poly(glycerol adipate) (PGA) is a biodegradable polymer with promising features for nanoparticulate drug carrier systems. By acylation of PGA with fatty acids, composite systems with amphiphilic properties can be obtained. Variation of the fatty acid (laurate, stearate and behenate) and their substitution degrees lead to a wide range of different polymer structures. This strongly influences the aggregation of the polymer and thus the nature of the resulting colloidal system. Based on the modification of the interfacial deposition method, various self-stabilizing nanoparticles with defined sizes and narrow size distributions could be prepared. Non-spherical shapes (squares, pentagons) with an internal lamellar-like structure were observed for low substituted PGA-stearates. Higher substitution degrees lead to ellipsoidal or spherical particles. The size, charge, fluidity and polarity of the nanoparticles have been studied comprehensively by PCS, AF4, zeta potential measurements, DSC, NMR, TEM and fluorescence spectroscopy. The chain lengths of the attached fatty acids as well as their substitution degree substantially influence the physicochemical properties of the bulk polymers and the nanoparticles. With their diverse particle shapes and internal structures as well as their different thermal behavior, aggregate states and polarities, the systems offer promising possibilities as delivery systems for lipophilic, amphiphilic and water soluble drugs.

β-Cyclodextrin-dextran polymers for the solubilization of poorly soluble drugs

The aim of this study was to assess the potential of novel β-cyclodextrin (βCD)-dextran polymers for drug delivery. The size distribution of βCD-dextrans (for eventual parenteral administration), the influence of the dextran backbones on the stability of the βCD/drug complex, the solubilization efficiency of poorly soluble drugs and drug release properties were investigated. Size analysis of different βCD-dextrans was measured by size exclusion chromatography (SEC) and asymmetrical flow field-flow fractionation (AF4). Stability of drug/βCD-dextrans was assessed by isothermal titration calorimetry (ITC) and molar enthalpies of complexation and equilibrium constants compared to some commercially available βCD derivatives. For evaluation of the solubilization efficiency, phase-solubility diagrams were made employing hydrocortisone (HC) as a model of poorly soluble drugs, whereas reverse dialysis was used to detect potential drug supersaturation (increased molecularly dissolved drug concentration) as well as controlled release effects. Results indicate that all investigated βCD-polymers are of appropriate sizes for parenteral administration. Thermodynamic results demonstrate that the presence of the dextran backbone structure does not affect the stability of the βCD/drug complex, compared to native βCD and commercially available derivatives. Solubility studies evidence higher solubilizing abilities of these new polymers in comparison to commercially available βCDs, but no supersaturation states were induced. Moreover, drug release studies evidenced that diffusion of HC was influenced by the solubilization induced by the βCD-derivatives.

Lipophilic Drug Transfer Between Liposomal and Biological Membranes: What Does It Mean for Parenteral and Oral Drug Delivery?

This review presents the current knowledge on the interaction of lipophilic, poorly water soluble drugs with liposomal and biological membranes. The center of attention will be on drugs having the potential to dissolve in a lipid membrane without perturbing them too much. The degree of interaction is described as solubility of a drug in phospholipid membranes and the kinetics of transfer of a lipophilic drug between membranes. Finally, the consequences of these two factors on the design of lipid-based carriers for oral, as well as parenteral use, for lipophilic drugs and lead selection of oral lipophilic drugs is described. Since liposomes serve as model-membranes for natural membranes, the assessment of lipid solubility and transfer kinetics of lipophilic drug using liposome formulations may additionally have predictive value for bioavailability and biodistribution and the pharmacokinetics of lipophilic drugs after parenteral as well as oral administration.