Surfactants membrane permeability

The ion pair extraction by flow injection analysis (FIA) has been used to analyze sodium dodecyl sulfate and sodium dodecyl ether (3 EO) sulfate among other anionic surfactants. The solvating agent was methanol and the phase-separating system was designed with a PTFE porous membrane permeable to chloroform but impermeable to the aqueous solution. The method is applicable to concentrations up to 1.25 mM with a detection limit of 15 pM [304]. 

An extraordinary way of stabilizing RUO2-coated CdS colloids for H2 generation was chosen by Fendler and co-workers The colloidal particles were generated in situ in surfactant vesicles of dioctadecyldimethylammonium chloride and dihexa-decyl phosphate. Thiophenol as a membrane permeable electron donor acted as a sacrificial additive. Later, a surface active re-usable electron donor (n-C,gH3,)2N — (CHj)—CH2—CHj—SH, Br was incorporated into the vesicles. Its R—SS—R oxidation product could be chemically reduced by NaBH to regenerate the active electron donor. The H2 yields in these systems were only 0.5 %. However, yields up to 10% were later reported for a system in which CdS was incorporated into a polymerizable styrene moiety, (n-C,jH3jC02(CH2)2) N (CH3) (CH2CgH4CH=CH2>, CP, and benzyl alcohol was used as the electron donor. 

Effects of Surfactant on High-phospholipid Membrane Permeability and Retention... 

Xia, W.J., and H. Onyuksel. 2000. Mechanistic studies on surfactant-induced membrane permeability enhancement. Pharm Res 17 612. 

Fatty acids [25], monoglycerides [25], fatty acid-bile salt micelles [26], and surfactants [27] have all been shown to increase epithelial membrane permeability by affecting the membrane proteins or lipids [28]. 

Photosynthesis Surfactants that alter membrane permeability are... 

The reported effects of surfactants on membrane permeability have been observed by other authors using a different approach. Rege et al. [32] studied the inhibition activity of non-ionic surfactants on P-glycoprotein (P-gp) efflux and the relationship between inhibition and membrane fluidity. Tween 80 and Cremophor inhibited P-gp. These inhibition effects could be related to their effects on membrane fluidity, as these surfactants fluidized cell lipid bilayers. This fluidification mechanism could be related to the increase in membrane polarity that we observed with synthetic surfactants in our experiments and it has been reported by other authors as a possible explanation for the inhibition effects of surfactants on P-gp efflux in the blood-brain barrier [33]. 

Penetration enhancers have been investigated for most mucosal and epithelial routes (see Sections 6.7.4, 8.5.3 and 9.7.1 for further details). The major challenge that remains is to find enhancers that will reversibly increase membrane permeability without causing toxicity during long-term use. Various surfactants and protease inhibitors have been reported to increase the pulmonary absorption of peptides and proteins on an experimental basis but their clinical use is not established and the current general consensus seems to be against their inclusion in pulmonary formulations. 

While the presence of surfactants is advantageous due to an increase in cellular membrane permeability, which facilitates drug absorption and bioavailability [218], caution needs to be taken in relation to the amount of surfactant incorporated, as high concentrations can lead to ocular toxicity. In general, nonionic surfactants are preferred over ionic ones, which are generally too toxic to be used in ophthalmic... 

In view of their solubilizing effects and also their potential to change membrane permeability, surfactants have been considered as absorption enhancers, again mostly in animals. Polyoxyethylene ethers have been shown to enhance gastric or rectal absorption of linco-mycin, penicillin, cephalosporins, and fosfomycin in rats and rabbits. In rats, colonic absorption of interferon-alpha is increased from 3 to 8% by polyoxyethylene esters of oleic acid and oleic acid glycerides. 

Surface activity is a phenomenon that has widespread consequences. Surface-active substances are those which adsorb at surfaces and lower surface tension these so-called surfactant materials have a wide applicability in pharmacy. In micellar form they can solubilise water-insoluble dmgs and many at low concentrations can increase membrane permeability and aid the transport of dmgs across biological barriers. Many dmgs have surface-active properties and this might have consequences for their activity and behaviour. The topic is summarised in a chapter on surface activity and surfactants. 

Large and small vesicles are more frequently studied as dispersed ensembles due to their ease of preparation and compatibility with solution phase analytical/physical methods. Lipid polymerization yields vesicles with enhanced stability to surfactants, organic solvents, dehydration, and heat [26]. Polymerization also alters membrane permeability to ions and molecules. These unique properties have spawned development of stable nanocapsules, bioreactors, and sensors. Many if not most of the liposomal architectures, methods to stabilize them, and technological applications discussed below have evolved from earlier pioneering work by many research groups. The reader is referred to previous key reviews [3,26,28]. 

Maintenance of UF membrane performance requires the cleaning of fouled membranes [23]. Standard procedures involve the circulation of acid, caustic, and surfactant solutions through the system in a cyclic fashion [24]. In this study, fouled membranes were at first treated with H2SO4 6.0 N. This procedure was not adequate as it caused a further decrease in the membrane permeability, likely related to protein precipitation on the membrane surface. A subsequent treatment with NaOH 0.5 N restored to some extent the initial permeability. In a new set of experiments, NaOH 0.5 N was solely used resulting on the... 

Since ILs with longer alkyl chains possess more lipophilic properties [16], these results are in accordance with toxicity studies with other chemicals (e.g., Ref [18]). In addition the structures of the compounds investigated show similarity to cationic surfactants, especially imidazolinium compounds. Cationic surfactants are known to increase membrane permeability and therefore cause narcotic effects with increasing chain length [19]. 

Surfactants reduce electron transfer resistance across cell membranes. On addition of surfactants, the membrane permeability of electroactive bacteria was significantly increased, which in turn accelerated the electron shuttle transport across the cell membrane. Moreover, the surfactant changed the cell roughness and increased the cell adhesion on the solid electrode, which resulted in higher biofilm loading. For example, chemically synthesized surfactants ethylenediamine tetraacetic acid (EDTA), polyethyleneimine... 

Chemical cleaning based on the use of adds, bases, oxidants and surfactants is also extensively used in MBR systems for recovering membrane permeability and redudng the frequency of recovery cleaning (Liao et al, 2004). The selection of a specific chemical agent depends on the nature of the foulants involved in the system. 

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