Search results for "kinetics"
showing 10 items of 2224 documents
Recovering ammonium by treated and untreated zeolitic mixtures: A comprehensive experimental and modelling study
2023
The recovery of ammonium (NH4+) from aqueous solutions by zeolite is attractive. In this study, the physicalchemistry of NH4+ adsorption process from aqueous solution by two zeolitic mixtures, either treated or not treated with NaCl, was assessed. Results suggested that the zeolitic mixture richer in mordenite and with high specific surface area adsorbed more NH4+ than the one richer in clinoptilolite and heulandite showing a lower specific surface area. NaCl treatment increased the amount of NH4+ adsorbed by the zeolitic mixtures. The higher amount of NH4+ adsorbed by the zeolitic mixtures treated with NaCl was explained by the low/high density water model accounting for cation exchange am…
Bioavailability in vivo of naltrexone following transbuccal administration by an electronically-controlled intraoral device: a trial on pigs.
2010
Naltrexone (NLX), an opioid antagonist, is widely used in the treatment of opiate addiction, alcoholism and smoking cessation. Its current peroral administration induces various adverse side effects and has limited efficacy since bioavailability and patient compliance are poor. The development of a long-acting drug delivery system of NLX may overcome the current drawbacks and help in the improvement of treatment of addiction. The primary endpoints of this study were: a) to compare the NLX bioavailability and pharmacokinetics after delivering a single transbuccal dose, released by a prototype of intraoral device, versus an intravenous (I.V.) bolus of the same drug dose; b) to verify the func…
Release of naltrexone on buccal mucosa: Permeation studies, histological aspects and matrix system design
2007
Transbuccal drug delivery has got several well-known advantages especially with respect to peroral way. Since a major limitation in buccal drug delivery could be the low permeability of the epithelium, the aptitude of NLX to penetrate the mucosal barrier was assessed. Ex vivo permeation across porcine buccal mucosa 800 microm thick was investigated using Franz type diffusion cells and compared with in vitro data previously obtained by reconstituted human oral epithelium 100 microm thick. Both fluxes (Js) and permeability coefficients (K(p)) are in accordance, using either buffer solution simulating saliva or natural human saliva. Permeation was evaluated also in presence of chemical enhance…
Mild Homogeneous Synthesis of Gold Nanoparticles through the Epoxide Route: Kinetics, Mechanisms, and Related One‐Pot Composites
2019
A new one-pot homogeneous methodology at room temperature to obtain Au nanoparticles (AuNP) on the basis of the epoxide route is presented. The proposed method takes advantage of the homogenous generation of OH- moieties driven by epoxide ring-opening, mediated by chloride nucleophilic attack. Once reached alkaline conditions, the reducing medium allows the quantitative formation of AuNP under well-defined kinetic control. A stabilizing agent, such as polyvinylpyrrolidone (PVP) or cetyltrimethylammonium chloride (CTAC), is required to maintain the AuNP stable. Meanwhile their presence dramatically affects the reduction kinetics and pathway, as demonstrated by the evolution of the UV/Vis spe…
Organophosphorus pesticides (chlorfenvinphos, phosmet and fenamiphos) photoelectrodegradation by using WO3 nanostructures as photoanode
2021
[EN] The photoelectrocatalytic (PEC) degradation of recalcitrant and toxic organophosphorus pesticides, fenamiphos, chlorfenvinphos and phosmet, has been performed by using an innovative WO3 nanostructure as photoanode. The nanostructure has been synthesized by anodization in acidic media in the presence of a very small amount (0.05 M) of H2O2, and its composition as well as its photoelectrochemical properties have been characterized using X-ray Photoelectron Spectroscopy and X-ray diffraction as composition technique and photoelectrochemical impedance spectroscopy as photoelectrochemical analysis. After 24 h of experiment, a degradation of 95% of chlorfenvinphos, 99.9% of phosmet and 100% …
Elimination of pesticide atrazine by photoelectrocatalysis using a photoanode based on WO3 nanosheets
2018
[EN] The photoelectrocatalytic (PEC) degradation of a persistent and toxic herbicide, atrazine, has been investigated by using a novel and high-performance WO3 nanostructure in the form of nanosheets/nanorods as photoanode. The nanostructure has been synthesized by anodization in acidic media in the presence of a very small amount (0.05 M) of H2O2, and its morphology, as well as its electrochemical and photoelectrochemical properties have been characterized. Atrazine was completely degraded after similar to 180 min of reaction following pseudo-first order kinetics, and 2-hydroxyatrazine was identified as the main intermediate species. Moreover, the s-triazine ring in cyanuric acid (the fina…
Molecular dynamics simulations of capillary rise experiments in nanotubes coated with polymer brushes.
2007
The capillary filling of a nanotube coated with a polymer brush is studied by molecular dynamics simulations of a coarse-grained model, assuming various conditions for the fluid-wall and fluid-brush interactions. Whereas the fluid is modeled by simple point particles interacting with Lennard-Jones forces, the (end-grafted, fully flexible) polymers that form the brush coating are described by a standard bead-spring model. Our experiments reveal that capillary filling is observed even for walls that would not be wetted by the fluid, provided the polymer brush coating itself wets. Generally, it is found that the capillary rise always proceeds through a t1/2 law with time t while the underlying…
Biowaiver Monograph for Immediate-Release Solid Oral Dosage Forms: Ondansetron.
2019
Literature data pertaining to the physicochemical, pharmaceutical, and pharmacokinetic properties of ondansetron hydrochloride dihydrate are reviewed to arrive at a decision on whether a marketing authorization of an immediate release (IR) solid oral dosage form can be approved based on a Biopharmaceutics Classification System (BCS)-based biowaiver. Ondansetron, a 5HT3 receptor antagonist, is used at doses ranging from 4 mg to 24 mg in the management of nausea and vomiting associated with chemotherapy, radiotherapy, and postoperative treatment. It is a weak base and thus exhibits pH-dependent solubility. However, it is able to meet the criteria of "high solubility" as well as "high permeabi…
Caki-1 cells as a model system for the interaction of renally secreted drugs with OCT3.
2008
<i>Background/Aims:</i> Organic cation transporters (OCT) in the proximal tubules (PTs) participate in the renal secretion of several therapeutic agents. The exact role of OCT3 in renal secretion remains undetermined, partially due to the lack of an appropriate in vitro model system. The current work introduces the PT representative cell line, Caki-1, as a model system for studying the involvement of OCT3 in renal secretion. <i>Methods:</i> Caki-1 cells were characterized for OCT3 expression via real-time RT-PCR and immunocytochemical staining techniques. Uptake kinetics of OCT3 in Caki-1 cells was determined using prototypical substrates and inhibitors. Inhibition o…
Oligosaccharide and Ganglioside Neuraminidase Activities of Mucolipidosis I (Sialidosis) and Mucolipidosis II (I-Cell Disease) Fibroblasts
1979
Fibroblasts cultured from the skin of patients with the genetic diseases mucolipidosis I and mucolipidosis II were found deficient in a neuraminidase specific for both an α23 and and α2 6 type of neuraminosyl linkage of sialyl oligosaccharides. Obligate heterozygotes (parents) showed an intermediate activity in mucolipidosis I, but a normal one in mucolipidosis II. The neuraminidase activity of mucolipidosis I fibroblasts towards gangliosides, measured at pH 4.5 in the presence of Triton X-100, was within the range of normal controls with gangliosides Gm3 and GD3, but somewhat diminished with a bovine brain ganglioside preparation. In mucolipidosis II, neuraminidase activity was markedly de…