Search results for "Ph dependent"

Cyclodextrin‐Calixarene Nanosponges as Potential Platforms for pH‐Dependent Delivery of Tetracycline

2019

Four mixed cyclodextrin-calixarene nanosponges were tested as possible Drug Delivery Systems, using Tetracycline antibiotic as a suitable model drug. The selected nanosponges featured a different composition ratio between the two host co-monomer components, and the possible presence of ionisable amine or carboxyl groups deriving from chemical post-modification. The pH-dependent absorption and release abilities of the materials were verified; in particular release kinetics showed the occurrence of a simple first-order profile. The antibacterial activity of nanosponge-tetracycline composites suitably prepared under sterile conditions was assayed towards both Gram-positive and Gram-negative ty…

Wechselwirkungen zwischen Acetylsalicylsäure und Lysin in Lösung

1985

Der pH-abhangige Einflus von Lysin auf die Hydrolyse von Acetylsalicylsaure zu Salicylsaure und auf die Bildung von Lysinderivaten der Acetylsalicylsaure wurde durch HPLC-Untersuchungen geklart. Die Bildung von e-N-Acetyl-lysin, α-N-Acetyl-lysin und wenig Diacetyl-lysin erfolgt rasch bei pH-Werten der Losung von 6 und hoher, sehr langsam jedoch bei dem fur gebrauchliche Injektionslosungen eingestellten pH-Wert 5. Das Auftreten des postulierten Salicyloyllysins in Acetylsalicylsaure-Lysin-Losungen wurde durch Vergleich mit der unabhangig synthetisierten Verbindung ausgeschlossen. Interactions of Acetylsalicyclic Acid and Lysine in Solution The influence of lysine on the hydrolysis, and on th…

Preparation, characterization and hydrolytic degradation of PLA/PCL co-mingled nanofibrous mats prepared via dual-jet electrospinning

2017

Abstract PLA/PCL co-mingled nanofibrous mats were prepared via multi-jet electrospinning. The concentration of PLA and PCL in the co-mingled mats were controlled by changing the flow rate of the two polymer solutions. The amount of PLA and PCL in the co-mingled nanofibrous mats was monitored by UV–Vis measurements through a colored dye added to PLA and by FTIR-ATR analysis. Morphology and mechanical properties of the nanofibrous mats were respectively examined by scanning electron microscopy (SEM) and tensile tests. Water contact angles measurements were also carried out in order to investigate the wettability of the materials. Finally, the hydrolytic degradation of the mats in buffer solut…

Isolation of Four New CoII/CoIII and NiII Complexes with a Pentadentate Schiff Base Ligand: Syntheses, Structural Descriptions and Magnetic Studies

2011

In this paper we report the temperature and pH dependent syntheses and systematic characterization of four new Co(II)/Co(III) and Ni(II) complexes with a pentadentate Schiff base ligand H(3)L obtained by condensing 1,3,-diaminopropan-2-ol with 2-hydroxyacetophenone in 1:2 molar ratio. The room temperature syntheses involving Co(II) and Ni(II) nitrates and the ligand H(3)L lead to the isolation of the dinuclear species [Co(2)L(2)(H(2)O)] (1), and the mononuclear complex [Ni(LH)] (3), respectively, whereas refluxing at basic pH leads to the tetranuclear complexes, [Co(II)(2)Co(III)(2)L(2)(μ(3)-OMe)(2)(NO(3))(H(2)O)(2)]NO(3)·2(H(2)O) (2), and [Ni(4)L(2)(μ(3)-OMe)(2)(H(2)O)(2)]·2H(2)O (4). 1 is…

Synthesis of a New pH-Dependent Ligand: Conformational and Complexation Studies

2003

A new macrocyclic ligand, 3, which exhibits pH-induced conformational changes, has been prepared. This ligand consists of a crown ether derived from a trans-anti-trans 1,2,4,5-tetrasubstituted cyclohexane. Due to the stereochemistry of the substituents on the carbocyclic ring, two different low-energy conformations of the crown ether are possible. Ligand 3 has been studied in solution by 1H NMR spectroscopy at different values of pH and temperature, showing that the conformation of the crown ether, and thus its complexing ability, is strongly pH-dependent. The solid-state structure of the ligand has been determined by X-ray diffraction.

An On/Off Circular Dichroism Signal Reveals a pH Dependent Competition between a Cyclodextrin and a Polyelectrolyte for an Atropisomeric Aromatic Gue…

1997

pH-Dependent ligands as carriers in transport experiments

2004

Abstract Conformationally pH-regulated ligands have been used as carriers in transport experiments. The experiments were carried out through bulky membranes and the pH at the source phase and at the receiving phase were modified to study the ability of ligands to act as pH-regulated carriers. The influence of pH on transport efficiency seems to be related to its influence on conformational equilibrium. X-ray determination of one precursor compound has been useful for determining the stereochemistry of one of the carriers. To cite this article: A.M. Costero et al., C. R. Chimie 7 (2004).

Unpredictable Performance of pH-Dependent Coatings Accentuates the Need for Improved Predictive in Vitro Test Systems.

2017

First introduced in the second half of the 19th century, enteric coatings are commonly used to protect acid-labile drugs, reduce the risk of gastric side effects due to irritating drugs, or for local drug delivery to the lower gastrointestinal (GI) tract. The currently available enteric-coatings are based on pH-sensitive weakly acidic polymers. Despite the long history of their use, the causes behind their performance often being unpredictable have not been properly investigated with most of the attention being focused only on the gastric emptying. However, little attention has been given to the postgastric emptying disintegration and dissolution of these dosage forms. This lack of attentio…