The solvated droplet size of concentrated water-in-oil (w/o) microemulsions prepared frome egg and soy lecithin/water/isopropyl myristate and containing short-chain alcohol cosurfactants has been determined using photon correlation spectroscopy (PCS). The effect of increasing the water volume fraction (from 0.04 to 0.26) on the solvated size of the w/o droplets at 298 K has been investigated at 4 different surfactant/cosurfactant weight ratios (Km of 1∶1, 1.5∶1, 1.77∶1, and 1.94∶1); in all cases the total surfactant/cosurfactant concentration was kept constant at 25% w/w. In the case of the microemulsions prepared from egg lecthin, the diffusion coefficients obtained from PCS measurements were corrected for interparticulate interactions using a hard-sphere model that necessitated estimation of the droplet volume fractions, which in the present study were obtained from earlier total intensity light-scattering (TILS) studies performed on the same systems. Once corrected for hard-sphere interactions, the diffusion coefficients were converted to solvated radii using the Stokes-Einstein equation assuming spherical microemulsion droplets. For both egg and soy lecithin systems, no microemulsion droplets were detected at water concentrations less than 9 wt% regardless of the alcohol and Km used, suggesting that at low concentrations of added water, cosolvent systems were formed. At higher water concentrations, however, microemulsion droplets were observed. The changes in droplet size followed the expected trend in that for a fixed Km the size of the microemulsion droplets increased with increasing volume fraction of water. At constant water concentration, droplet size decreased slightly upon increasing Km. Interestingly, only small differences in size were seen upon changing the type of alcohol used. The application of the hard-sphere model to account for interparticulate interactions for the egg lecithin systems indicated that the uncorrected diffusion coefficients underestimated particle size by a factor of slightly less than 2. Reassuringly, the corrected droplet sizes agreed very well with those obtained from our earlier TILS study.
Lecithin Droplet Size Microemulsion System Photon Correlation Spectroscopy Microemulsion Droplet
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Lawrence MJ. Microemulsions as drug delivery vehicles. Curr Opin Colloid Sci. 1996; 1: 826–832.CrossRefGoogle Scholar
Khoshnevis P, Mortazavi SA, Lawrence MJ, Aboofazeli R. In-vitro release of sodium salicylate from water-in-oil phospholipid microemulsions. J Pharm Pharmacol. 1997; 49(Suppl 4): 47.Google Scholar
Trotta M. Influence of phase transformation on indomethacin release from microemulsions. J Control Rel. 1999; 60: 399–405.CrossRefGoogle Scholar
Trotta M, Morel S, Gasco MR Effect of oil phase composition on the skin permeation of felodipine from oil-in-water microemulsions. Pharmazie. 1997; 52: 50–53.PubMedGoogle Scholar
Lyklema J. Fundamentals of Interface and Colloid Science. Vol. 1: Fundamentals. London: Academic Press, 1991.Google Scholar
Hou MJ, Kim M, Shah, DO: A light-scattering study on the droplet size and interdroplet interaction in microemulsions of AOT-oil-water system. J Colloid Interface Sci. 1988; 123: 398–412.CrossRefGoogle Scholar
Cheung HM, Qutubuddin S, Edwards R, Man JA Jr. Light scattering study of oil-in-water microemulsions: corrections for interactions. Langmuir. 1987; 3: 744–752.CrossRefGoogle Scholar
Delgado Charro MB, Iglesias Vilas G, Blanco Mendez J, Lopez Quintela MA, Marty JP, Guy RH: Delivery of a hydrophilic solute through the skin from novel microemulsion systems. Eur J Pharm Biopharm. 1997; 43: 37–42.CrossRefGoogle Scholar
Constantinides PP, Scalart J-P. Formulation of water-in-oil microemulsions containing long- versus medium-chain triglycerides. Int J Pharm. 1997; 158: 57–68.CrossRefGoogle Scholar
Gao Z-G, Choi H-G, Shin H-J, et al. Physicochemical characterization and evaluation of a microemulsion system for oral delivery of cyclosporin A. Int J Pharm. 1998; 161: 75–86.CrossRefGoogle Scholar
Schmalfuss U, Neubert R, Wohlrab W. Modification of drug penetration into human skin using microemulsion. J Control Rel. 1997; 46: 279–285.CrossRefGoogle Scholar
Constantinides PP, Lancaster CM, Marcello J, et al. Enhanced intestinal-absorption of an RGD peptide from water-in-oil microemulsions of different composition and particle size. J Controlled Rel. 1995; 34: 109–116.CrossRefGoogle Scholar
Aboofazeli R, Barlow DJ, Lawrence MJ. Particle size analysis of phospholipid microemulsions. I. Total intensity light scattering. PharmSci. 2000; 2: 12.Google Scholar
Aboofazeli R, Lawrence MJ. Investigations into the formation and characterization of phospholipid microemulsions. I. Pseudo-ternary phase diagrams of systems containing water-lecithin-alcohol-isopropyl myristate. Int J Pharm. 1993; 93: 161–175.CrossRefGoogle Scholar
Koppel DE. Analysis of macromolecular polydispersity in intensity correlation spectroscopy: the methods of cumulants. J Phys Chem. 1972; 57: 4814–4820.CrossRefGoogle Scholar
Coumou DJ. Apparatus for the measurement of light scattering in liquids. Measurement of the Rayleigh factor of benzene and of some other pure liquids. J Colloid Sci. 1960; 15: 408–417.CrossRefGoogle Scholar
Finsy R. Particle sizing by quasi-elastic light scattering. Advan Colloid Interface Sci. 1994; 52: 79–143.CrossRefGoogle Scholar
Constantinides PP, Yiv SH. Particle size determination of phase-inverted water-in-oil microemulsions under different dilution and storage conditions. Int J Pharm. 1995; 115: 225–234.CrossRefGoogle Scholar
Percus JK, Yevick GJ. Analysis of classical statistical mechanics by means of collective co-ordinates. Phys Rev. 1958; 110: 1–13.CrossRefGoogle Scholar