Aggregation Behavior of Sodium Fusidate in Aqueous Solution

Coello, Adela; Meijide, Francisco; Rodríguez‐Núñez, Eugenio; Tato, José Vázquez

doi:10.1002/jps.2600830614

Cited by 9 publications

(4 citation statements)

References 32 publications

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“…Such a difference has been related to the lower surface charge of bile salt micelles than classical ones, i.e., the palisade layer, in the sense given to it in classical surfactant micelles, does not exist in bile salt aggregates . This is in agreement with the values obtained for the fraction of bound counterions for NaC, sodium fusidate (an antibiotic with a similar structure to that of a bile salt), and other bile salts . For most of these compounds, and in particular for NaDC, a value of 3:1 is observed for the ratio of monomers:bound counterions, which has been related to a structure in which the monomers are packed in a back-to-back way , with the orientation of monomers alternatively up and down, the lateral chain supporting the carboxylate group which defines it.…”

Section: Resultssupporting

confidence: 84%

Unusual Pyrene Excimer Formation during Sodium Deoxycholate Gelation

Jover¹,

Meijide²,

Núñez³

et al. 1996

Langmuir

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Steady-state and time-resolved fluorescence have been used to study the gelation of sodium deoxycholate at pH values close to neutrality. Pyrene was used as a probe. The results suggest the formation of pyrene excimer as a result of the aggregation process: when two clusters carrying probes form a larger one, pyrene molecules can interact in both the ground and excited states. Fluorescence lifetimes for monomer and excimer pyrene are given and favorably compared to similar systems. A structure for the aggregates is also suggested.

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Section: Resultssupporting

confidence: 84%

Unusual Pyrene Excimer Formation during Sodium Deoxycholate Gelation

Jover¹,

Meijide²,

Núñez³

et al. 1996

Langmuir

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“… log false[ Q false] cmc .15em ≅ .15em log .25em cmc -.25em = -.10em 1 N .25em log .25em false[ micelles false] K − normalβ .25em log false[ X false] From cmc values in Table , values of β = 0.46 and β = 0.48 are obtained for bis(DC)-EDTA and bis(C)-EDTA, respectively. The results are in agreement with those of natural bile salts, for which values in the range β = 0.3−0.6 have been published. ,− It must be remembered that the palisade layer, in the sense given to it in classical surfactant micelles, does not exist in bile salt aggregates. , …”

Section: Resultssupporting

confidence: 85%

Aggregation Behavior of Tetracarboxylic Surfactants Derived from Cholic and Deoxycholic Acids and Ethylenediaminetetraacetic Acid

et al. 2009

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The reaction of 3beta-aminoderivatives of cholic and deoxycholic acids (steroid residues) with dimethyl ester of ethylenediaminetetraacetic acid (bridge) leads to the formation of dimers carrying four carboxylic organic functions, two of them located on the side chain of each steroid residue and the other two on the bridge. As tetrasodium salts, these new compounds behave as surfactants and have been characterized by surface tension, fluorescence intensity of pyrene (as a probe), and static and dynamic light scattering measurements. Thermodynamic parameters for micellization were obtained from the dependence of the critical micelle concentration (cmc) with temperature. For both surfactants, the fraction of bound counterions is close to 0.5. The aggregation behavior is similar to one of their bile salt residues [i.e., sodium cholate (NaC) and sodium deoxycholate (NaDC)] and can be summarized as follows: (i) molecular areas at the interface for the new surfactants are fairly close to twice the value for a single molecule in a monolayer of natural bile salts; (ii) the environment where pyrene is solubilized is very apolar, as in natural bile salt aggregates; (iii) Gibbs free energies (per steroid residue) for micellization are not far from published values for NaC and NaDC, and the differences can be understood on the basis of less hydrophobicity of the new surfactants due to the charges in the bridge; and (iv) as for NaC and NaDC, aggregates have rather low aggregation numbers (which depend on the amount of added inert salt, NaCl). A structure based on the disklike model accepted for small bile salt aggregates is proposed.

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“…Bile salts have hydrophobic and hydrophilic molecular surfaces, rather than a hydrophilic headgroup and a hydrophobic hydrocarbon tail. As a consequence of their structure, the aggregation number and size of bile salt micelles is strongly dependent on the total bile salt concentration. − …”

Section: Resultsmentioning

confidence: 99%

“…As a consequence of their structure, the aggregation number and size of bile salt micelles is strongly dependent on the total bile salt concentration. 35 − 37 …”

Section: Resultsmentioning

confidence: 99%

Extending the Pseudo-Phase Model of Detergent–Lipid Dispersions by a Detergent-Binding Protein

Vormittag

Heerklotz

2022

Langmuir

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Mixed micellar drug delivery systems for poorly soluble active pharmaceutical ingredients (APIs) are easy to produce and long-term stable, because they represent equilibrium structures. However, their fate after intravenous injection is still largely unknown. Once injected into the bloodstream, they can potentially convert to vesicles or disappear altogether, with both API and excipients being picked up by blood components. Our study aimed at reducing the gap between the good, quantitative understanding of aqueous glycocholate (GC)–lecithin dispersions alone and the highly complex situation in the blood. To this end, we extended the pseudophase model previously established for lipid–detergent dispersions to include the detergent-binding protein albumin as another component. The model predicted a quaternary phase diagram with planar phase boundaries defined by key parameters of the ternary subsystems, which were then determined by isothermal titration calorimetry. They include the aqueous GC concentration upon bilayer-micelle coexistence, 5.2 mM, the GC-to-lipid mole ratios in coexisting bilayers (R e sat = 0.2) and micelles (R e sol = 0.7), as well as the capacity of the albumin to bind 0.1 GC molecules with a dissociation constant of K D = 0.1 mM and 6 GC molecules with K D = 0.7 mM. Subsequent measurements in the quaternary system showed phase boundaries in good agreement with the model predictions. In addition, the critical micelle concentration of GC shows a minimal value (midpoint of transition) of 9.1 mM at the temperature of 24 °C where the demicellization enthalpy is zero. The demicellization process is accompanied by a heat capacity change of 29 cal/mol K. The model improves the understanding of the mixed micellar drug delivery systems. The success of the approach encourages including even more blood components, like lipoproteins, to a quantitative treatment.

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Aggregation Behavior of Sodium Fusidate in Aqueous Solution

Cited by 9 publications

References 32 publications

Unusual Pyrene Excimer Formation during Sodium Deoxycholate Gelation

Unusual Pyrene Excimer Formation during Sodium Deoxycholate Gelation

Aggregation Behavior of Tetracarboxylic Surfactants Derived from Cholic and Deoxycholic Acids and Ethylenediaminetetraacetic Acid

Extending the Pseudo-Phase Model of Detergent–Lipid Dispersions by a Detergent-Binding Protein

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