sodium-dodecyl-sulfate and 6-carboxyfluorescein

The mechanisms governing the interaction of equimolecular mixtures of Triton X-100 (Tx-100) and sodium dodecyl sulfate (SDS) with phosphatidylcholine liposomes were investigated. Permeability alterations were determined as a change in 5(6)-carboxyfluorescein released from the interior of vesicles and bilayer solubilization as a decrease in the static light-scattered by liposome suspensions. At subsolubilizing level, a maximum bilayer/water partitioning of surfactant mixture was reached at 30% CF release, which correlated with the increased presence of SDS in the bilayers. However, transition stages between 70% CF release and 100% light-scattering corresponded to the increased presence of Tx-100 in these structures. These findings may be correlated with the reduced deleterious effects caused by this mixture in different tissues versus pure SDS, given that the presence of Tx-100 may modulate the level of SDS partitioning in the human stratum corneum. At subsolubilizing level, the mixture showed higher affinity with bilayers than those reported for single components, whereas at solubilizing level this affinity was slightly lower and higher than those reported for Tx-100 and SDS respectively. A direct relationship was established in the initial interaction steps between the growth of vesicles, the leakage of entrapped CF and the effective molar ratio of surfactant to phospholipid in bilayers (Re). This dependence was also detected during solubilization, where the decrease in the vesicle size and in the scattered light of the system depended on the Re parameter and hence on the bilayer composition. The fact that the free surfactant concentration at subsolubilizing and solubilizing levels showed respectively lower and similar values than the critical micelle concentration (c.m.c.) of the surfactant mixture indicates that permeability alterations and solubilization were determined respectively by the action of surfactant monomer and by the formation of mixed micelles. This finding supports the generally admitted assumption, for single surfactants, that the concentration of free surfactant must reach the c.m.c. for solubilization to occur and highlights the influence of the negative synergism of this surfactant mixture on the free surfactant concentration needed to saturate or solubilize liposomes.

Topics: Detergents; Fluoresceins; Light; Lipid Bilayers; Liposomes; Micelles; Octoxynol; Particle Size; Permeability; Phosphatidylcholines; Scattering, Radiation; Sodium Dodecyl Sulfate; Solubility

The mechanisms governing the interaction of mixtures of sodium dodecyl sulfate (SDS) and nonylphenol oxyethylenated with 10 mol of ethylene oxide (NP(EO)10) with phosphatidylcholine liposomes were investigated. Permeability alterations were detected as a change in 5(6)-carboxyfluorescein (CF) released from the interior of vesicles and bilayer solubilization as a decrease in the static light scattered by liposome suspensions. Three parameters were described as the effective surfactant/lipid molar ratios (Re) at which the surfactant system (a) resulted in 50% of CF release (Re50%CF), (b) saturated the liposomes (ReSAT), and (c) led to a complete solubilization of these structures (ReSOL). From these parameters the corresponding surfactant partition coefficients (K50%CF, KSAT, and KSOL) were determined. Despite the fact that Re increased as the mole fraction of the SDS rose (XSDS), the K parameters showed maximum values at XSDS 0.6 and 0.2 for K50%CF and KSAT, respectively, the KSOL reaching the highest value in the absence of SDS XSDS = 0). Thus, the higher the surfactant contribution in surfactant/lipid system, the lower the XSDS at which the maximum bilayer/water partitioning of mixed surfactant systems added took place. The free surfactant concentrations SW were lower than the mixed surfactant CMCs at subsolubilizing level, whereas it remained similar to these values during saturation and solubilization of bilayers in all cases.

Topics: Chemical Phenomena; Chemistry, Physical; Drug Stability; Ethylene Glycols; Fluoresceins; Lipid Bilayers; Liposomes; Micelles; Permeability; Phosphatidylcholines; Sodium Dodecyl Sulfate; Solubility; Surface-Active Agents

The mechanism underlying the shark repellency of SDS was studied by comparing it with the shark nonrepelling detergent, Triton X-100. The findings can be summarized as follows: (1) The effective concentration of SDS for termination of shark tonic immobility (an immediate and fast response) was close to its critical micellar concentration in sea water (70 microM). The fish lethal concentrations (LD50) were far below the CMC value for SDS, and at CMC level for Triton X-100. (2) In sea water SDS possesses a strong affinity for lipid membranes, expressed in a lipid sea water partition coefficient (Kp) of about 3000. (3) In liposomal systems examined by assays of turbidity, fluorescence resonance energy transfer and kinetics of carboxyfluorescein (CF) release, the pattern of SDS induced changes in the phospholipid bilayer suggests: (a) absence of vesicle-vesicle fusion; (b) occurrence of vesicle size increase, and (c) nonlytic gradual release of CF above and below its CMC values. In contrast, Triton X-100 above its CMC induces membrane solubilization. (4) Assays coupling CF release from liposomes to potassium diffusion potential induced by valinomycin indicate that SDS related CF release can also be attributed to a specific mechanism such as cation pore formation and not only to membrane solubilization. The hypothesis of pore formation by SDS is discussed.

Topics: Animals; Detergents; Fluoresceins; Kinetics; Lethal Dose 50; Liposomes; Octoxynol; Polyethylene Glycols; Seawater; Sharks; Sodium Dodecyl Sulfate; Temperature

We have investigated the promotive effect of various agents on percutaneous absorption of 6-carboxyfluorescein (CF), a water-soluble fluorescent dye, as poorly absorbable drugs. The absorption of CF was determined by measuring rat plasma CF levels. As an absorption promoter, several reagents such as surface-active agents, protein solubilizers and permeation promoters were used. The used concentration of the reagents was determined so as not to make a trauma on the skin. As results, plasma CF levels following the co-administration of 0.05 w/v% sodium dodecyl sulfate and 0.1 v/v% 2-mercaptoethanol showed the highest values. Plasma CF level was increased 40 times as compared to that of control experiment and was increased 9 times as compared to that of pretreatment with 4 w/v% calcium thioglycolate which was reported previously as a strong absorption promoter for theophylline by us. When the stratum corneum, having a barrier function for percutaneous absorption of many compounds, was removed mechanically, plasma CF levels of control experiment and pretreatment with 4 w/v% calcium thioglycolate were increased remarkably. However, plasma CF level after the co-administration of 0.05 w/v% sodium dodecyl sulfate and 0.1 v/v% 2-mercaptoethanol did not show a considerable difference as compared to that of the case with the presence of the stratum corneum.

Topics: Administration, Topical; Animals; Coloring Agents; Dimethyl Sulfoxide; Fluoresceins; Male; Mercaptoethanol; Rats; Rats, Inbred Strains; Skin Absorption; Sodium Dodecyl Sulfate; Thioglycolates; Urea