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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 44 (1972), S. 2109-2111 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 13 (1996), S. 32-37 
    ISSN: 1573-904X
    Keywords: albumin ; nanospheres ; manufacturing ; glutaraldehyde ; cross-linking ; central composite design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to develop a new method to produce albumin particles in the sub-200-nanometer range with a narrow size distribution and in a controlled and reproducible manner. Methods. A new emulsion crosslinking method was developed using ultrasound and static mixing as homogenization steps and a central composite design was used to evaluate the influence of different process parameters on particle size, polydispersity and yield. Results. Response surface analysis allowed the location of the most important factors. Of all the factors investigated, only the albumin concentration and the aqueous phase volume showed a significant influence on response parameters. Albumin nanospheres with sizes below 200 nm in diameter and very narrow size distributions were obtained in high yields (〉80%). Conclusions. This study describes a new preparation method for albumin nanoparticles which are suitable for future drug targeting studies.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-904X
    Keywords: peptide transport ; permeation enhancers ; micellar systems ; cell monolayers ; cytotoxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The effects of five different permeation enhancer systems on the transport properties of a peptidomimetic thrombin inhibitor, CRC 220, were investigated in monolayers of a human intestinal cell line (Caco-2). Methods. The transepithelial transport rates and additionally the cytotoxic properties of these enhancers were characterized using the following tests: measurement of the transepithelial electrical resistance (TEER), the MTT-transformation, the protein content and the release of cytosolic lactate dehydrogenase (LDH), as well as FITC-phalloidin and propidium iodide staining. Results. All permeation enhancer systems showed concentration-dependent effects on cell permeability and toxicity. The most prominent effects on peptide transport were seen at the highest concentration (40 mM), yielding the rank order, NaTC 〉 NaTC/Cholesterol 〉 Solulan C24 〉 NaTC/Oleic acid 〉 NaTC/PC18. Using the TEER after 120 min exposure as the most sensitive parameter describing cytotoxicity, the following order was obtained: Solulan C24 〉 NaTC 〉 NaTC/ PC 18 = NaTC/Cholesterol 〉 NaTC/Oleic acid 〉 NaTC/PC. Generally, efficient enhancement of peptide transport was associated with a noticeable influence on cell viability under in-vitro conditions. Conclusions. Taking into account permeation and cytotoxicity as a function of concentration, both NaTC at 15 mM and the mixed micellar system NaTC/oleic acid at 0.75 mM offer interesting enhancement properties, showing an 18-fold increase in CRC 220 transport rates. The effects on cell viability and cytotoxicity were comparatively low and of reversible nature.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-904X
    Keywords: Caco-2 ; cell culture ; renin inhibitors ; permeability ; peptide transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 15 (1998), S. 1238-1243 
    ISSN: 1573-904X
    Keywords: estradiol ; ethanol ; transdermal delivery ; reservoir system ; ethylene vinyl acetate membrane ; rate control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The aim of our study was to clarify the kinetic performance of a membrane controlled reservoir system (MCRS) for β-estradiol (E2) under in vitroconditions by determination of the role of membrane and adhesive layer on E2flux control. Methods. E2and ethanol fluxes across EVA membrane or membrane coated with adhesive from saturated solutions in defined ethanol/PBS mixtures were measured in the symmetric and asymmetric configuration. Physicochemical parameters of the EVA membrane were determined. Results. The E2flux across the 9% EVA membrane steadily increased with increasing ethanol concentrations in both configurations, due to enhanced uptake of E2by the polymer and increasing membrane diffusivity. Permeation across the EVA membrane coated with an adhesive layer in the symmetric and asymmetric configuration increased up to maximum values of 0.80 ± 0.14 (μg × cm−2× h−1and 0.37 ± 0.02 μg × cm−2× h−1, respectively, at 62.5% (v/v) ethanol. The fluxes then decreased with further increase in the volume fraction of ethanol due to a dramatically reduced permeability of the adhesive layer. For the asymmetric case, a linear dependence of E2on ethanol fluxes was observed. Conclusions. The E2flux from MCRS is strictly dependent on reservoir ethanol concentrations, whereas the adhesive layer represents the rate controlling barrier at high ethanol levels (〉70% v/v).
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-904X
    Keywords: nasal cell culture models ; differentiation ; histochemical characterization ; lectin binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To evaluate different in-vitro cell culture models for their suitability to study drug transport through cell monolayers. Methods. Bovine turbinate cells (BT; ATCC CRL 1390), human nasal septum tumor cells (RPMI, 2650; ATCC CCL 30), and primary cell cultures of human nasal epithelium were characterized morphologically and histochemically by their lectin binding properties. The development of tight junctions in culture was monitored by actin staining and transepithelial electrical resistance measurements. Results. The binding pattern of thin-sections of excised human nasal respiratory epithelium was characterized using a pannel of fluorescently-labelled lectins. Mucus in goblet cells was stained by PNA, WGA and SBA, demonstrating the presence of terminal N-acetylglucosamine, N-acetylgalactosamine and galactose residues respectively in the mucus of human nasal cells. Ciliated cells revealed binding sites for N-acetylglucosamine, stained by WGA, whereas Con A, characteristic for mannose moieties, labelled the apical cytoplasm of epithelial cells. Binding sites for DBA were not present in this tissue. Comparing three different cell culture models: BT, RPMI 2650, and human nasal cells in primary culture using three lectins (PNA, WGA, Con A) as well as intracellular actin staining and transepithelial electrical resistance measurements we found, that only human nasal epithelial cells in primary culture showed differentiated epithelial cells, ciliated nasal cells and mucus producing goblet cells, which developed confluent cell monolayers with tight junctions. Conclusions. Of the in-vitro cell culture models studied, only human nasal cells in primary culture appears to be suitable for drug transport studies.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-904X
    Keywords: gene transfer ; cytotoxicity ; polyethylenimine ; polyfection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Low molecular weight branched polyethylenimine (LMW-PEI) was synthesized and studied as a DNA carrier for gene delivery with regard to physico-chemical properties, cytotoxicity, and transfection efficiency. Methods. The architecture of LMW-PEI, synthesized by acid catalyzed ring-opening polymerization of aziridine was characterized by size exclusion chromatography in combination with laser light scattering and 13C-NMR-spectroscopy. In vitro cytotoxic effects were quantified by LDH and MTT assay and visualized by transmission electron microscopy. The potential for transgene expression was monitored in ECV304 cells using luciferase driven by a SV40 promoter as reporter gene system. Results. LMW-PEI (Mw 11′900 D) with a low degree of branching was synthesized as a DNA carrier for gene delivery. In contrast to high molecular weight polyethylenimines (HMW-PEI; Mw l′616′OOO D), the polymer described here showed a different degree of branching and was less cytotoxic in a broad range of concentrations. As demonstrated by transmission electron microscopy the LMW-PEI formed only small aggregates which were efficiently taken up by different cells in the presence of serum, most likely by an endocytic pathway. LMW-PEI yielded transfection efficiencies measured via expression of the reporter gene luciferase which were up to two orders of magnitude higher than those obtained with HMW-PEI. The reporter gene expression was concentration dependent, but in contrast to lipofection independent of serum addition. Conclusions. The LMW-PEI described here is a new, highly efficient, and non-cytotoxic vector with a favorable efficiency/toxicity profile for gene therapeutic applications.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-904X
    Keywords: thyrotropin-release hormone (TRH) ; cell-culture ; Caco-2 ; metabolism ; passive diffusion ; carrier-mediated transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cell culture models for gastrointestinal transport and metabolism are important mechanistic tools. Our studies of Caco-2 monolayers demonstrate heterogeneity in transport characteristics depending on passage number and origin of the cells. In accordance with data obtained in animals and humans, TRH shows a carrier-mediated, saturable transport component, which operates parallel to a passive pathway in Caco-2 cells at passage number 89-99. At low TRH concentrations (〈3 mM) active transport becomes prominent, as demonstrated by the temperature dependence of TRH transport and inhibition experiments. The Michaelis-Menten parameters of the active, saturable transport component are: Km = 1.59 mM and Vmax = 1.84 µM/min. The pH optimum was determined to be at pH 6.0. On the other hand an exclusively paracellular passive route was found with Caco-2 cells at passage number 30-34. These results are also in agreement with observations made by others in cell culture experiments. The aspect of rigorously characterizing the specific Caco-2 clone under investigation is emphasized, especially when active transport mechanisms are suspected.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-904X
    Keywords: cell culture ; keratinocytes ; estradiol ; ethanol ; metabolism ; transdermal delivery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The aim of our study was to investigate the kinetics of β-estradiol (E2) metabolism in the human keratinocyte cell line HaCaT and to estimate the effect of the potential inhibitor ethanol on the biotransformation reaction. Methods. The formation rates of estrone (E1) in dependence on substrate concentrations were determined in HaCaT cells using tritium labelled E2. Experiments were conducted with and without addition of dehydroepiandrosterone (DHEA) and ethanol. Possible toxic effects on the cells due to ethanol were investigated by cytotoxicity tests. Results. The metabolism of E2 in HaCaT cells exhibited Michaelis-Menten kinetics with Km and Vmax values of 3.5 μM and 216 pmol × mg−1 protein × h−1, respectively. The reaction was inhibited by DHEA and ethanol. The alcohol showed a reversible competitive inhibition mechanism for concentrations of 4 to 8% (v/v). Lower ethanol concentrations had no effect, whereas levels ≥10% significantly decreased cell viability leading to a different inhibition mechanism. Conclusions. The HaCaT cell line seems to be a suitable model for studying enzyme kinetics equivalent to the human skin. The concentration dependent inhibitory effect of ethanol observed in this cell line may be relevant for the transdermal E2 application in patients.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-904X
    Keywords: cell culture ; Caco-2 ; thrombin inhibitors ; passive diffusion ; in vitro/in vivo correlation ; carrier-mediated transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Peptidomimetic thrombin inhibitors (TI), derived from L-Asp-D-Phe were examined in confluent monolayers of a human colon carcinoma cell line (Caco-2) to elucidate their transepithelial transport properties. Effect availabilities, based on activated partial thromboplastin time (aPTT) measurements in rats, after peroral administration of five TI correlated reasonably well with permeability coefficients obtained from in vitro transport studies in Caco-2 monolayers, whereas physicochemical properties, such as molecular mass, solubilities, pKa and octanol-buffer partition coefficients failed to yield meaningful relationships. Substitution of the β-carboxylic group of L-Asp leads to analogues which are mainly transported by passive diffusion, while an unsubstituted carboxylic group favours carrier-mediated active transport. The effects of concentration, temperature, competitive inhibitors and direction dependence on in vitro transport were investigated. The results obtained are compatible with a saturable carrier-mediated transport, operating parallel to a passive paracellular route. The Michaelis-Menten parameters for the active transport component (Km = 1.67 mM, Vmax = 26.5 pmol min−1 mg protein−1) indicate an involvement of the intestinal di/-tripeptide transport system for one of the TI. The Caco-2 transport model may be helpful for the design of perorally active peptidomimetics.
    Type of Medium: Electronic Resource
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