Membrane barrier test

In Vitro Membrane Barrier Test Method for Skin Corrosion, Draft New Guideline (May 2004)... 

In vitro membrane barrier test method for skin corrosion (Draft)... 

The OECD and EU have developed specific test guidelines for in vitro/ex vivo testing of skin corrosion, the Transcutaneous Electrical Tesistance (TER) Test and the Human Skin Model Test (see Table 4.7). In fact, the EU Annex V, B.40 test guideline includes the two adopted OECD in vitro tests for skin corrosion (TG 430 and 431). OECD has also developed a third test guideline for skin corrosion, the In Vitro Membrane Barrier Test this test guideline has not yet been adopted. 

The membrane barrier test is composed of two components, a synthetic macromolecular bio-barrier and a chemical detecting system (CDS). The basis of the test method is that it detects membrane barrier damage caused by corrosive test substances after the application of the test substance to the surface of the artificial membrane barrier presumably by the same mechanism(s)... 

Polymeric membranes for separation of hydrogen and oxygen isotopes were studied at INCT, Warsaw [92-95,140-141]. Both hydrophUic barriers, such as regenerated cellulose and hydrophobic PTFE membranes, were tested. The regenerated cellulose appeared to be a very good system to get high separation factors and to consider membrane permeation as possible and competitive method for enrichment deuterium and 0 in natural water. 

Selective separation and concentration of both cations and anions using water-soluble polymer solutions LM as carriers and hoUow-fiber units (artificial kidneys) as membrane barrier were tested. The authors termed the process as affinity dialysis [74]. Hollow fiber units of Spectrum Medical Industries, Inc. with fibers of 5000 molecular weight cutoff and 150 cm surface area from Spectrapor were used in the experiments. 

The thin film composite membrane exhibited superior overall rejection performance in these tests, with ammonia and nitrate rejection showing an outstanding improvement. It has also been reported that silica rejection by the thin film composite membranes is superior to that of cellulose acetate. While the above data indicates a marginal improvement in the rejection of chemical oxygen demand (COD), which is an indication of organic content, other tests conducted by membrane manufacturers show that the polyurea and polyamide membrane barrier layers exhibit an organic rejection that is clearly superior to that of cellulose acetate. Reverse osmosis element manufacturers should be contacted for rejection data on specific organic compounds. ... 

The equation in this form cannot be used directly since we do not have experimental values for the partition coefficient of the permeability barrier within the membrane. What we do have for each permeant are values of partition coefficients for various model organic solvents which we want to test as descriptors of the cell membrane barrier, and hence as possible estimates of the K values. In order to test the reasonableness of a particular choice of organic solvent we transform Eqn. 8 into the generalised form... 

The pinhole samples demonstrated leak failures in 29 of the 30 samples leak failures were expected in all 30 pinhole samples. After investigation, it was discovered that a hole was not induced in the membrane barrier for the sample that passed the test. Of the 30 pinhole samples subjected to the aerosol challenge test, four samples failed, as they demonstrated growth of the indicator organism. It was expected that all 30 pinhole samples would fail the aerosol challenge test. 

Another three-layer system was fabricated and extensively investigated by Si et al. [27]. The middle, barrier layer was solution cast from a mixture of Nafion and poly(vinylidene fluoride) and the outer layers were formed by spraying a commercial Nafion solution followed by solvent evaporation. A 50- om thick membrane comprising a 10-pm barrier layer (55% PVDF loading) had the same thickness as Nafion 112 membrane, but its methanol crossover was 36% that of Nafion 112. The membrane was tested in a DMFC at 60°C with IM methanol and ambient pressure air. Its performance (maximum power density of 80 mW cm ) was significantly better than that with Nafion 112, but only slightly better than an MEA with a Nafion 117 membrane. 

Membrane Barrier Corrosivity Test Method (Corrositex ) In vitro... 

Polyethylene-based membranes are manufactured for use in hazardous waste landfills, lagoons, and similar applications. Two of these products have been tested to determine their effectiveness as barriers against radon diffusion. (In most cases, diffusive flow is considered of little or no significance as a mechanism of radon entry compared with convective flow). A 20-mil high-density polyethylene tested 99.9% effective in blocking radon diffusion under neutral pressure conditions. A 30-mil low-density polyethylene tested 98% effective in blocking radon diffusion under neutral pressure conditions. 

Another available product has two faces of aluminum foil over a core of glass scrim webbing it is coated with asphalt. The membrane is 0.012 in. thick. This material has not been tested as a barrier against diffusive flow of radon, but its performance should be similar to that of other foil-faced products. Seams are sealed with aluminum tape. 

To reach such a site, a molecule must permeate through many road blocks formed by cell membranes. These are composed of phospholipid bilayers - oily barriers that greatly attenuate the passage of charged or highly polar molecules. Often, cultured cells, such as Caco-2 or Madin-Darby canine kidney (MDCK) cells [1-4], are used for this purpose, but the tests are costly. Other types of permeability measurements based on artificial membranes have been considered, the aim being to improve efficiency and lowering costs. One such approach, PAMPA, has been described by Kansy et al. [5],... 

Recently in our group, model membrane permeation barriers have been constructed with concentrated phospholipid solutions, 10-74% wt/vol soy lecithin (approximate %w/w lipid composition 24% PC, 18% PE, 12% PI cf. Table 3.1) in dodecane, supported on high-porosity, hydrophobic microfilters. This newly formulated lipid has a net negative charge at pH 7.4, which further increases above pH 8, as the ethanolamine groups deionize. Also tested were 10% wt/vol egg lecithin lipid solutions in dodecane (approximate composition 73% PC, 11% PE,... 

This refers to the transport across the epithelial cells, which can occur by passive diffusion, carrier-mediated transport, and/or endocytic processes (e.g., transcytosis). Traditionally, the transcellular route of nasal mucosa has been simply viewed as primarily crossing the lipoidal barrier, in which the absorption of a drug is determined by the magnitude of its partition coefficient and molecular size. However, several investigators have reported the lack of linear correlation between penetrant lipophilicity and permeability [9], which implies that cell membranes of nasal epithelium cannot be regarded as a simple lipoidal barrier. Recently, compounds whose transport could not be fully explained by passive simple diffusion have been investigated to test if they could be utilized as specific substrates for various transporters which have been identified in the... 

In another approach, Parnigotto and coworkers reconstructed corneal structures in vitro by using corneal stroma containing keratocytes to which corneal epithelial cells from bovine primary cultures were overlaid [73], However, this particular corneal model did not contain an endothelial layer. This model was histochemically characterized and the toxicity of different surfactants was tested using MTT methods. This stroma-epithelium model has been reported to show a cornea-like morphology, where a multilayered epithelial barrier composed of basal cells (of a cuboidal shape) and superficial cells (of a flattened shape) is noted. Furthermore, the formation of a basement membrane equivalent and expression of the 64-kDa keratin were reported, indicating the presence of differentiated epithelial cells. The toxicity data for various surfactants obtained with this model correlate well with those seen by the Draize test [73], However, this corneal equivalent was not further validated or used as a model for permeation studies. 

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