Andleeb Z. Naqvi

Mixed Micelle Formation between Amphiphilic Drug Amitriptyline Hydrochloride and Surfactants (Conventional and Gemini) at 293.15−308.15 K

The micellization of amphiphilic drug amitriptyline hydrochloride (AMT, an antidepressant) and conventional as well as gemini surfactants has been studied conductometrically in pure and mixed states in aqueous solutions at different temperatures to derive various physicochemical properties such as critical micelle concentration (cmc), ideal cmc (cmc(id)), counterion dissociation (g), standard Gibbs free energy (DeltaG(m)(0)), enthalpy (DeltaH(m)(0)), and entropy of micellization (DeltaS(m)(0)), micellar mole fractions of surfactant (X1, X1(m)), mole fraction of surfactant in ideal state (X1(id)), interaction parameter (beta), activity coefficients (f1, f2), and excess free energy of mixing (DeltaG(ex)). All the results indicate synergism and attractive interactions in the mixed systems.

Studies of mixed micelle formation between cationic gemini and cationic conventional surfactants

Mixed micellization of dimeric cationic surfactants tetramethylene-1,4-bis(hexadecyldimethylammonium bromide)(16-4-16), hexamethylene-1,6-bis(hexadecyldimethylammonium bromide) (16-6-16) with monomeric cationic surfactants hexadecyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC), and tetradecyltrimethylammonium bromide (TTAB) have been studied by conductivity and steady-state fluorescence quenching techniques. The behavior of mixed systems, their compositions, and activities of the components have been analyzed in the light of Rubinghs regular solution theory. The results indicate synergism in the binary mixtures. Ideal and experimental critical micelle concentrations (i.e., cmc(*) and cmc) show nonideality, which is confirmed by beta values and activity coefficients. The micelle aggregation numbers (N(agg)), evaluated using steady-state fluorescence quenching at a total concentration of 2 mM for CTAB/16-4-16 or 16-6-16 and 5 mM for TTAB/16-4-16 or 16-6-16 systems, indicate that the contribution of conventional surfactants was always more than that of the geminis. The micropolarity, dielectric constant and binding constants (K(sv)) of mixed systems have also been evaluated from the ratios of respective peak intensities (I(1)/I(3) or I(0)/I(1)).

Mixed micelles of amphiphilic drug promethazine hydrochloride and surfactants (conventional and gemini) at 293.15K to 308.15K: Composition, interaction and stability of the aggregates.

Micellization of an amphiphilic phenothiazine drug promethazine hydrochloride (PMT) in presence of conventional (CTAB and TTAB) as well as gemini (16-s-16 and 14-s-14, s=4-6) cationic surfactants has been studied conductometrically at different temperatures. Critical micelle concentration values (cmc and cmc(id)) indicate mixed micelle formation among the two components. Micellar mole fractions of surfactants (X(1), X(1)(M) and X(1)(id)) show greater contribution of surfactants. Interaction parameter, β, suggests attractive interactions in the mixed systems. The thermodynamic parameters suggest dehydration of hydrophobic part of the drug at higher temperatures.

Influence of additives on the clouding phenomenon of chlorpromazine hydrochloride solutions

Herein we report the effect of various additives (viz. alcohols, cycloalcohols, amino acids, sugars, ureas) on the clouding phenomenon observed in 50mM chlorpromazine hydrochloride (CPZ) drug solutions (prepared in 10mM sodium phosphate buffer). Long chain alcohols (except octanol), cyclohexanol and allylalcohol increased the cloud point (CP) followed by a decrease with the increase in alcohol concentration but short chain alcohols affected the CP insignificantly. Effect of amino acids depended upon their nature: acidic and salts of basic amino acids increased the CP while basic amino acids depressed it; non-polar and uncharged polar amino acids caused small changes in CP. Additives of urea family decreased the CP. All sugars caused a decrease in CP, which is in consonance to their effect on the critical micellar concentration. The overall behavior is explained on the basis of additives affecting the solvent as well as micelle aggregation and/or structure.

Study of the Cloud Point of the Phenothiazine Drug Chlorpromazine Hydrochloride : Effect of Surfactants and Polymers

Surfactants/polymers are used extensively in drug delivery as drug carriers. We herein report the effect of surfactants and polymers on the cloud point (CP) of amphiphilic drug chlorpromazine hydrochloride. At fixed drug concentration (50 mM) and pH (6.7) these additives affect the CP in accordance to their nature and structure: anionic surfactants show an increase followed by a decrease, whereas cationic (conventional as well as gemini) and nonionic surfactants show continous increase. The behavior with polymers is dictated by the number of units present in a particular polymer. Increase in drug concentration and pH, in presence of fixed amounts of CTAB, increases and decreases the CP, respectively. Variation of CP with pH at various fixed gemini concentrations shows that gemini surfactants are better candidates for drug delivery.

Micellization of mixtures of amphiphilic drugs and cationic surfactants: a detailed study.

The micellization behaviors of two amphiphilic drugs ((amitriptyline hydrochloride (AMT) and imipramine hydrochloride (IMP)) in presence of cationic surfactants (conventional as well as gemini) have been investigated conductometrically at four mole fractions and four temperatures. The critical micelle concentration (cmc) values come out to be lower than cmc(id) values (cmc(id) is the cmc value at ideal mixing state) indicating attractive interactions between the two components in mixed micelles. Micellar mole fractions of surfactants (X(1) and X(1)(M)), calculated by Rubingh and Motomura models, are always greater than X(1)(id) (micellar mole fraction at ideal mixing). The rigid structure of drugs decreases their contribution in mixed micelles as compared to that predicted by X(1)(id) values. Although α(1) (mole fraction of surfactant) is higher for DTAB than that of 12-4-12, the contribution of 12-4-12 is almost equal to that of DTAB. The interaction parameter (β) is negative at all temperatures and at all compositions indicating attractive interactions. Activity coefficients (f(1) and f(2)) are always less than unity suggesting nonideality in the systems. Thermodynamic parameters suggest dehydration of hydrophobic part of the drug at or above certain temperature which is different for the two drugs.

Mixed micellization of antidepressant drug amitriptyline hydrochloride with cationic surfactants

The surface tension measurements have been carried out on aqueous solutions of antidepressant drug amitriptyline hydrochloride with six cationic surfactants (decyl-, dodecyl-, tetradecyl-, cetyltrimethylammonium bromide, cetylpyridinium bromide and cetylpyridinium chloride) at different mole fractions to study the surface and micellar properties at the interface as well as in the micelles. The properties studied include critical micelle concentration (cmc), Gibbs surface excess (Gamma(max)), minimum head group area at the air/water interface (A(min)), free energy of micellization (DeltaG(m)( composite function)), and standard Gibbs energy of adsorption (DeltaG(ads)( composite function)), while synergistic behavior of drug-surfactant binary mixtures was analysed using Clints and Rubinghs models. Deviations of cmc from cmc(*) and X(1)(m) from X(1)(ideal) indicate the synergistic behavior (i.e., non-ideal behavior) for the drug-surfactant binary mixtures. The values of interaction parameters beta and activity coefficients f(1) and f(2) (for both, in mixed monolayer as well as in mixed micelles) also indicate the synergistic behavior. The excess free energy (DeltaG(ex)) for the drug-surfactant binary mixtures explains stability of mixed micelles in comparison to micelles of pure drug and variation with alkyl chain length of surfactants.

Cloud Point Phenomenon in Amphiphilic Drug Promethazine Hydrochloride+Electrolyte Systems

Herein we report clouding phenomenon occurring in amphiphilic drug promethazine hydrochloride (PMT) in the presence of electrolytes. The CP of 50 mM drug solution, prepared in 10 mM sodium phosphate buffer, was found to decrease with increasing pH due to deprotonation of drug molecules at high pH. Addition of inorganic salts (KF, KCl and KBr) to drug solutions at fixed pH (6.7) and drug concentration (50 mM) caused an increase in CP. The results have been discussed on the desorption/adsorption of counterions to the headgroups. Cations also increased the CP by affecting the water structure with their effectiveness being in the order: Li+<Na+<K+<NH4 +. In the presence of NaCl, increase in drug concentration increased the CP while increase in pH showed an opposite trend.

Conductometric study of antidepressant drug–cationic surfactant mixed micelles in aqueous solution

Conductivity measurements have been carried out on aqueous solutions of two antidepressant drugs (nortriptyline hydrochloride and clomipramine hydrochloride) with four cationic surfactants (monomeric: cetyltrimethylammonium bromide, tetradecylammonium bromide; dimeric: 1,5-pentanediyl-alpha-omega-bis(hexadecyldimethylammonium bromide), 1,4-butanediyl-alpha,omega-bis(hexadecyldimethylammonium bromide) as well as with sodium chloride. Counterions from NaCl adsorb to the charged headgroup of the drug molecules and reduce the repulsion, hence cmc decreases. cmc values decreased with the addition of surfactants indicating mixed micelle formation. Experimental mole fraction of surfactants in micelle (X1) and their ideal values (X1 id) also support this explanation. Interaction parameter, beta, and excess free energy of micellization are negative suggesting synergism in mixed state. Activity coefficients are less than unity which means non-ideal mixing.

Aqueous amphiphilic drug (amitriptyline hydrochloride)-bile salt mixtures at different temperatures.

The mixing behavior of amphiphilic drug amitriptyline hydrochloride (AMT) with bile salts (NaC, NaDC, NaTC) was studied at different compositions and temperatures by conductometry. Rubinghs, Motomuras and Clints approaches were used to analyse the behavior. The obtained results indicate attractive interactions among the two components upon mixing. The experimentally obtained critical micelle concentration (cmc) values are always lower than ideal cmc values. Increase in temperature gives a peaked behavior to cmc. Micellar mole fraction (X(1) and X(1)(m)) values show that the contribution of bile salts in mixed micelles increases with the increase in concentration of these salts.