Biological activity surfactant effects

Within a series with a fixed hydrophilic head group, detergency increases with increasing carbon chain length, reaches a maximum, and then decreases. This behavior frequentiy reflects a balance between increased surface activity of the monomer and decreased monomer concentration with increased surface activity. Similar effects are seen in surfactants in biological systems. 

Recent publications indicate the cloud-point extraction by phases of nonionic surfactant as an effective procedure for preconcentrating and separation of metal ions, organic pollutants and biologically active compounds. The effectiveness of the cloud-point extraction is due to its high selectivity and the possibility to obtain high coefficients of absolute preconcentrating while analyzing small volumes of the sample. Besides, the cloud-point extraction with non-ionic surfactants insures the low-cost, simple and accurate analytic procedures. 

In recent years bi- and polyfunctional phosphorus-containing surfactants have attracted interest, mainly due to their combination of surface activity and sequestering ability. However, anticorrosiveness and biologically active behavior are also effects that are sought after. 

Sample preparation used to extract proteins from cells prior to analysis is an important step that can have an effect on the accuracy and reproducibility of the results. Proteins isolated from bacterial cells will have co-extracted contaminants such as lipids, polysaccharides, and nucleic acids. In addition various organic salts, buffers, detergents, surfactants, and preservatives may have been added to aid in protein extraction or to retain enzymatic or biological activity of the proteins. The presence of these extraneous materials can significantly impede or affect the reproducibility of analysis if they are not removed prior to analysis. 

The difficulty with HLB as an index of physicochemical properties is that it is not a unique value, as the data of Zaslavsky et al. (1) on the haemolytic activity of three alkyl mercaptan polyoxyethylene derivatives clearly show in Table 1. Nevertheless data on promotion of the absorption of drugs by series of nonionic surfactants, when plotted as a function of HLB do show patterns of behaviour which can assist in pin-pointing the necessary lipophilicity required for optimal biological activity. It is evident however, that structural specificity plays a part in interactions of nonionic surfactants with biomembranes as shown in Table 1. It is reasonable to assume that membranes with different lipophilicities will"require" surfactants of different HLB to achieve penetration and fluidization one of the difficulties in discerning this optimal value of HLB resides in the problems of analysis of data in the literature. For example, Hirai et al. (8 ) examined the effect of a large series of alkyl polyoxyethylene ethers (C4,C0, Cj2 and C 2 series) on the absorption of insulin through the nasal mucosa of rats. Some results are shown in Table II. 

In some biological systems nonionic surfactants have an intrinsic biological activity the Ci2 alkyl ethers were too toxic to be used in the experiments of drug absorption with goldfish. The activity of the C12 ethers was quantified by measurement of the fish turnover time, T. When the reciprocal of the turnover time is plotted against alkyl chain length for the series Cx and Ejq and C12 compound is distinguished by its marked effect. (12). 

Although supercritical CO2 is an effective solvent for oils, fats, and similar substances, it is a poor one for nonvolatile hydrophilic (water-loving) substances such as proteins or metallic salts. Adding water as such to the supercritical CO2 is of little help, as the solubility of water in it is limited. Johnson and co-workers216 overcame the latter limitation by forming water-in-C02 emulsions with the aid of an added nontoxic perfluoropolyether surfactant that forms reverse micelles around the water microdroplets, in effect combining the special properties of supercritical CO2 with the solvent power of water. These emulsions can dissolve a variety of biomolecules at near-ambient temperatures, without loss of their biological activity. 

The micelle formulation approach often possesses disadvantages such as its toxicity associated with surfactants even at relatively low concentrations. In general, nonionic surfactants have the least toxic effects. Cremophor EL produces hypersensitivity reactions in human and animals (Jonkman-de Vries et al., 1996). Tween-80 is also believed to cause acute hepatitis and renal failure (Uchegbu and Florence, 1996). On intravenous administration, owing to their surface activity, surfactant molecules have the potential to penetrate and disrupt biological membranes and can be hemolytic (Ten Tije et al., 2003). Often the absorption capacity of the micelle is too small and the extent of the... 

The presence of surfactants in drug formulations may produce unwanted side or toxic effects because of their interaction with proteins, lipids, membranes and enzymes. To fully understand these interactions, it is essential to have information on the metabolic fate of the ingested surfactant. Membrane disruption by surfactants involves binding of the surfactant monomers to the membrane components, followed by the formation of co-micelles of the surfactant with segments of the membrane. The interaction between surfactants and proteins can lead to solubilization of the insoluble-bound protein or to changes in the biological activity of enzyme... 

Vieitez et al [247] interpreting the disparate effects of Tween 20,40 and 80 on the elongation of Avena coleoptile sections concluded that the fatty acid moiety of the surfactant accounted for any intrinsic biological activity. Tween 20 has a growth inhibiting effect. Tween 40 has little effect, whereas Tween 80 enhances... 

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