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ABSTRACT: The effect of the addition of cyclodextrins (CD) viz., alpha-, beta-, HPbeta- and gamma-CD to the aqueous solutions of the most widely prescribed anti-inflammatory drug, diclofenac sodium (DS), has been fully investigated by means of spectroscopic (UV-vis, steady-state fluorescence, (1)H NMR and ROESY) and thermodynamic (conductivity) techniques. The global picture of the results indicates that diclofenac sodium penetrates the CD cavity. The apparent association constants for all the inclusion complexes were estimated from fluorescence data. Conductivity measurements of aqueous solutions of diclofenac sodium were performed both as a function of DS concentration and CD concentration, at different temperatures ranging from 15 to 40 degrees C. Results suggested the existence of 1:1 complex between DS and CD. The thermodynamics of the system was discussed in terms of change in Gibbs free energy. Free energy of the DS/W system was found to decrease on addition of cyclodextrin, which points towards the energetically favorable interactions between drug and cyclodextrin molecules in solution phase. (1)H NMR chemical shift changes and ROESY spectra provide powerful means for probing CD:DS interactions.
Journal of Colloid and Interface Science 10/2008; 326(2):374-81. · 3.07 Impact Factor
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ABSTRACT: Conductivity, static fluorescence and (1)H NMR measurements have been carried out to study the micellar behavior of aqueous solutions of dodecyldimethylethylammonium bromide (DDAB), dodecyltrimethylammonium chloride (DTAC) and tetradecyltrimethylammonium chloride (TDAC) in absence and presence of alpha-cyclodextrin (alpha-CD), beta-cyclodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HPbeta-CD) and gamma-cyclodextrin (gamma-CD). The conductivity measurements were carried out at 298.15 K. The influence of cyclodextrins on the micellar parameters, such as cmc* (apparent critical micellar concentration), beta (degree of ionization) have been analyzed. Thermodynamics of the systems was discussed in terms of the change in standard free energy of micellization, DeltaG(m)(0). Micellization was found to be less spontaneous in presence of cyclodextrins. The fluorescence intensity of the surfactant solutions is enhanced by the addition of cyclodextrins. The association constants obtained from conductivity and fluorescence data suggest the binding of gamma-CD with the surfactants to be strongest among all the cyclodextrins used. (1)H NMR chemical shift changes provide powerful means for probing the cyclodextrin-micellar interactions and inclusion of surfactant is shown by the change in the chemical shift of some of the guest and host protons in comparison with the chemical shifts of the same protons in the free compounds.
Journal of Colloid and Interface Science 06/2008; 321(2):442-51. · 3.07 Impact Factor
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ABSTRACT: The behavior of rifampicin (D) with
D\textG\texto\texta \Delta {\text{G}}^{{\text{o}}}_{{\text{a}}}
of aggregation was also calculated from the critical concentration data. An attempt has also been made to estimate the stoichiometry of -cyclodextrin:rifampicin association.
Colloid and Polymer Science 01/2005; 283(5):532-538. · 2.33 Impact Factor
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ABSTRACT: Micellar behavior of cationic surfactants, dodecyldimethylethylammonium bromide (DDAB) and dodecyltrimethylammonium chloride (DTAC) in aqueous media has been investigated over the temperature range 288.15–308.15 K. The critical micelle concentration (cmc) and degree of ionization (β) of the micelles were determined from the conductivity measurements at different temperatures. The cmc behavior of DDAB and DTAC was analyzed in comparison with the results of DTAB in terms of effect of counter ion and increase in alkyl chain. Thermodynamic parameters (, and ) for the micelle system were estimated by applying the charged pseudo-phase separation model. At lower temperatures, the micellization in case of DDAB was found to be entropy-driven while at higher temperatures it was enthalpy-driven. In case of DTAC only entropic effect dominates over the entire temperature range.
Colloids and Surfaces A: Physicochemical and Engineering Aspects.
