Abstract:

A review. A novel technol. to prep. modified reverse microemulsion (denoted NSSL, nanosized self-assembled liq.) vehicles loaded with cosmetoceuticals, based on permitted ingredients that can be progressively dild. with water, was developed recently in our labs. The microemulsion isotropic regions representing water-in-oil (W/O), bicontinuous mesophase, and oil-in-water (O/W) microemulsion structures are presented in a phase diagram so-called U-type. In such compns. in the isotropic regions of the phase diagram, structures can invert from L2 (reverse micelles) to an L1 (direct micelles) phase via W/O, bicontinuous, and O/W regions progressively, without phase sepn. The concs. (condensed reverse micelles) can be loaded at very high solubilization capacities of guest mols. (lycopene, phytosterols, tocopherols, CoQ10, lutein, antioxidants, aromas, fragrances) that are oil sol. or even mostly insol. in the water or oil phase. The solubilization exceeds manyfold that of the soly. capacity of each of the phases. The microemulsion phase transformations were studied by cond., viscosity differential scanning calorimetry (DSC), and self-diffusion-NMR (SD-NMR) measurements, and the microstructure was detd. by small-angle x-ray scattering (SAXS), cryo-transmission electron microscopy (TEM). The loci of the solubilizate at any given water content were detd. by following the self-diffusion coeffs. of each of the ingredients. It was concluded that the solubilizates are easily accommodated and tightly packed at the concave, hydrophobic-in-nature, water-in-oil interface and at the bicontinuous interface. Most solubilizates are more loosely packed at the oil-in-water interface and tend to be released from the interface once inversion occurs. Upon inversion to O/W microemulsion droplets, the interface becomes more hydrophilic and convexes toward the water, becoming the continuous phase. The solubilization capacity drops dramatically, and the active matter can be trigger released. The nutraceuticals are solubilized at higher solubilization capacities if interacting with the surfactant. Upon entrapping guest mols., the transition from W/O to bicontinuous, and thereafter to an O/W microemulsion, is occurring, in some cases, at higher levels of water diln., while in other cases, depending on the nature of the solubilizate, at lower dilns., indicating that some of the guest compds. add some order to the internal microemulsion organization, while others are destructive to the interface and enhance phase sepn. or phase transitions. [on SciFinder(R)]