title: Light-scattering studies of testosterone enanthate containing soybean oil/C18:1E10/water oil-in-water microemulsions.
abstract: Total-intensity light scattering (TILS) and photon correlation spectroscopy (PCS) techniques have been used to determine the droplet size of concentrated, oil-in-water microemulsions formed from soybean oil, polyoxyethylene-10-oleyl ether (C(18:1)E(10)), and water, both in the presence and absence of the lipophilic drug, testosterone enanthate. The TILS data were analyzed using the hard-sphere model of Percus-Yevick to account for interparticulate interactions experienced in the concentrated systems studied and the volume fraction of the hard-sphere droplet obtained from these analyses used to correct the PCS data. Correction of the light-scattering data in this manner yielded a satisfactory agreement between the size of the microemulsion droplets calculated using both techniques. Both the TILS and PCS data showed that, for a constant surfactant concentration, the size of the microemulsion droplets increased with increasing oil content. For example, droplets of radius 52.5 and 65.1 A (as determined by TILS) were obtained at 10.0% w/w C(18:1)E(10) and 0.5 and 2.0% w/w soybean oil, respectively. In contrast, for a constant oil concentration, microemulsion droplet size decreased with increasing surfactant concentration. For example, droplet sizes of 65.1, 59.3, 56.6, 54.5, and 53.3 A were seen with 2.0% w/w soybean oil and 10, 14.0, 18, 22, or 26% w/w C(18:1)E(10), respectively. Furthermore, in the presence of 1.0% w/w of the lipophilic drug, testosterone enanthate, the size of the microemulsion droplet increased by about 6-10 A depending on the concentration of the surfactant; the higher the concentration of the surfactant, the smaller the increase in size. The slight increase in size of the drug-containing microemulsion droplets suggests that some of the drug has penetrated into the core of the droplet.
authors.affiliation: Department of Pharmacy, Franklin Wilkins Building, King's College London, 150 Stamford Street, London, SE1 9NN, United Kingdom.
authors.forename: Carole
authors.initials: C
authors.lastname: Malcolmson
authors.forename: David J
authors.initials: DJ
authors.lastname: Barlow
authors.forename: M Jayne
authors.initials: MJ
authors.lastname: Lawrence
mesh_terms: D004655:Emulsions; D011092:Polyethylene Glycols / Q000737:chemistry*; D013024:Soybean Oil / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D013739:Testosterone / Q000031:analogs & derivatives* / Q000737:chemistry*; D014867:Water
chemical_list: D004655:Emulsions; D014867:Water; D011092:Polyethylene Glycols; D013739:Testosterone; C004648:testosterone enanthate; D013024:Soybean Oil