The level of solubilization of the drug testosterone propionate into 2% w/w oil-in-water (o/w) microemulsions, stabilized by the nonionic surfactant polyoxyethylene 10-oleyl ether (Brij 96) and containing a range of oils, has been determined. Although testosterone propionate was readily soluble in the ethyl esters ethyl oleate, ethyl caprylate, and ethyl butyrate, and the triglycerides soybean oil, Miglyol 812, and tributryin, and the alkene 1-heptene, only microemulsions containing the ethyl esters and the triglyceride oils exhibited a significant increase in solubilization over the corresponding micellar solution (i.e., surfactant solution in the absence of oil). Furthermore, the increase in drug solubility observed in the microemulsion systems was not related to the solubility of the drug in the bulk oil. That is, while the smaller molecular volume oils, such as ethyl butyrate, exhibited a greater capacity for the drug, microemulsions containing these oils were only marginally better at solubilizing the drug than the corresponding micellar solution. In contrast, microemulsions containing the larger molecular volume oil, Miglyol 812, gave levels of drug solubilization almost three times those containing ethyl butyrate, yet the bulk capacity for drug in this oil was less than half that of ethyl butyrate. Light scattering and phase inversion temperature studies suggested that the structure of the microemulsion was sensitive to the oil being used, in that, at the low oil concentrations used in this study, the smaller molecular volume oils generally penetrated the interfacial surfactant monolayer in much the same way as a cosurfactant, causing an alteration, presumably a dilution, of the relatively concentrated polyoxyethylene region close to the hydrophobic core, thereby destroying one of the main loci of drug solubilization and counteracting any advantages encountered due to the high solubility of the drug in the bulk oil.

This paper reports the first use of a novel completely optically based photothermal method (O-PTIR) for obtaining infrared spectra of both fixed and living cells using a quantum cascade laser (QCL) and optical parametric oscillator (OPO) laser as excitation sources, thus enabling all biologically relevant vibrations to be analyzed at submicron spatial resolution. In addition, infrared data acquisition is combined with concomitant Raman spectra from exactly the same excitation location, meaning the full vibrational profile of the cell can be obtained. The pancreatic cancer cell line MIA PaCa-2 and the breast cancer cell line MDA-MB-231 are used as model cells to demonstrate the capabilities of the new instrumentation. These combined modalities can be used to analyze subcellular structures in both fixed and, more importantly, live cells under aqueous conditions. We show that the protein secondary structure and lipid-rich bodies can be identified on the submicron scale.

Specular neutron reflectometry is a powerful technique to resolve interfacial compositions and structures in soft matter. Surprisingly however, even after several decades, a universal modeling approach for the treatment of data of surfactant and phospholipid monolayers at the air/water interface has not yet been established. To address this shortcoming, first a systematic evaluation of the suitability of different models is presented. The result is a comprehensive validation of an optimum model, which is evidently much needed in the field, and which we recommend as a starting point for future data treatment. While its limitations are openly discussed, consequences of failing to take into account various key aspects are critically examined and the systematic errors quantified. On the basis of this physical framework, we go on to show for the first time that neutron reflectometry can be used to quantify directly in situ at the air/water interface the extent of acyl chain compaction of phospholipid monolayers with respect to their phase. The achieved precision of this novel quantification is ∼10%. These advances together enhance significantly the potential for exploitation in future studies data from a broad range of systems including those involving synthetic polymers, proteins, DNA, nanoparticles and drugs.