Strukturspezifisches Sorptions- und Freigabeverhalten poröser Kieselgele gegenüber Arzneistoffen

Zusammenfassung Poröse Kieselgele mit unterschiedlicher Herkunft — Korngröße, Gestalt der Teilchen und Hohlraumstruktur — werden auf ihr Reaktionsverhalten gegenüber verschiedenen Arneistoffen (Codein, Na-Dodecylbenzolsulfonat, Tetradecylpyridiniumchlorid) untersucht. Unter Berücksichtigung verschiedener Strukturparameter der porösen Teilchen — mittlerer Porendurchmesser, Porenvolumenverteilung, spezifisches Porenvolumen, spezifische Oberfläche, Korngröße - können Schlußfolgerungen bezüglich der Arzneistoffaufnahme in das Porengerüst und der Wirkstoff liberation gezogen werden. Der Verlauf der Wirkstoff-liberation gibt Hinweise auf die Transportmechanismen in den Trägerpartikeln und auf den spezifischen Aufbau der Kieselgelhohlraumstruktur. Bei der Diskussion der Austauschprozesse finden die von den verschiedenen Milieubedingungen abhängigen Grenzflächenreaktionen der Arzneistoffe an den funktionellen Gruppen der Kieselsäureoberfläche Beröksichtigung.Anisometrische über Sol-Gel-Zustand erhaltene Teilchen besitzen danach eine gleichmäßige Verteilung der verschiedenen Porengrößen über das gesamte Kornvolumen, während das Reaktionsverhalten von kugelförmigen Kieselgelen aus Polyäthoxysiloxan von bestimmten Poren an der Kugeloberfläche geprägt wird.Dieser unterschiedliche Aufbau erklärt die erheblichen Differenzen im zeitlichen Verlauf der Arzneistoffliberation und dem Ausmaß der Arzneistoff-bindung zwischen anisometrischen und kugelförmigen Teilchen bei ähnlichen Strukturparametern. Hieraus ergeben sich Konsequenzen für den Einsatz solcher Trägermaterialien zur Steuerung der Wirkstoffliberation.

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Summary Spherical and irregularly shaped silica particles with graduated particle sizes and pore structure parameters were tested as supports for drugs s. a. codeine, sodium dodecylbenzenesulfonate, and tetradecylpyridiniumchloride.The sorption and deliberation behavior of the drugs is a function of the mean particle diameter, the specific surface area, and the mean pore diameter of the particles. Furthermore, these processes are strongly influenced by the nature of the solvent, the pH value and the salt concentration, which determine the type and the strength of the surface interaction between the solutes and the silica surface.A distinct difference in the sorption behavior and in the kinetics of drug released was observed between the spherical and the irregularly shaped particles. This effect can be explained by a different pore size arrangement within and at the surface of the porous particles. The use of these silica supports offers the possibility of a controlled drug release.

     

Depth distributions of implanted atoms under the influence of surface erosion and diffusion

Shallow range distributions are altered significantly by diffusion and surface erosion. It will be shown here that the simultaneous processes of implantation, diffusion, and surface erosion can be described by a second order differential equation which is mathematically tractable and yields general results in terms of analytical functions. The resulting depth distributions depend on one parameter only which is a combination of the mean particle range, the diffusion coefficient, and the velocity of surface erosion (e.g. sputtering). The theory is applied to practical cases, e.g. implantation of plasma particles in the wall of fusion reactors, or solar wind ions in the surface of meteorite materials.     

Range distributions for 25–200 keV 14N+ ions

Many features involved in the problem of heat flow through a semifinite metal sample irradiated with nanosecond laser pulses are discussed with reference both to the underlying physics and to the numerical solution of the heat diffusion equation.

Analytical expressions for several quantities, such as average velocities for the liquid-solid interface motion, maximum melted depth, and maximum surface temperature are presented. Experimental impurity profiles detected in Al samples after laser irradiation are analyzed on the basis of a diffusion-segregation hypothesis. The effects of ruby laser irradiation on virgin and ion-implanted Al single crystals, studied by using Rutherford backscattering and channelling are discussed in terms of epitaxial lattice regrowth, defect formation and metastable solid solutions.     

Reflection approach for the analytical description of light ion implantation into bilayer structures

Abstract

One of the main problems while developing analytical multilayer models for ion implantation is how to make them ‘physical'. Satisfactory agreement between results obtained with existing multilayer models and the Monte Carlo prediction cannot always be expected, since mostly none of the important physical effects is accounted for. Extensive Monte Carlo study has been performed in order to extract some guiding principles for the construction of a more physically based multilayer model. Ion reflection accross the interfaces has a very strong impact on the final shape of a multilayer profile. First attempts to include this phenomenon in a multilayer model have been made. In this paper, a simple approach for light ion reflection at an interface is presented and the incorporation into a multilayer model is discussed.     

Ferrocene‐substituted 3,3′‐diindolylmethanes with improved anticancer activity

A series of ferrocene‐substituted derivatives ( 2a , 2b , 2c , 2d , 2e , 2f , 2g ) of the known drug 3,3′‐diindolylmethane ( DIM ) were prepared and tested for their in vitro antitumor activity. The derivatives 2a (featuring indole moiety), 2b (featuring 2‐methylindole moiety) and 2f (featuring 5‐nitroindole moiety) were growth‐inhibiting in vitro at lower concentrations than DIM in various tumor cells including pancreas cancer (BcPC‐3), three DIM‐resistant cancer cell lines (518 A2, KB‐V1/Vbl, HT‐29), triple‐negative breast cancer (MDA‐MB‐231) and prostate cancer (PC‐3). Derivatives 2a , 2b and 2f were the most active compounds of this series, qualifying as drug candidates for various cancer diseases. Copyright © 2016 John Wiley & Sons, Ltd.