Water-Dilutable Biocompatible Microemulsion Systems: Design and Characterisation

The present study describes a screening approach in design of microemulsion preconcentrates (self-microemulsifying systems) comprising: PEG-8 caprylic/capric glycerides (Labrasol (R)) (surfactant), PEG-40 hydrogenated castor oil (Cremophor (R) RH40) (cosurfactant) (at surfactant-to-cosurfactant mass ratios 9:1, 7:3, 5:5, 3:7 and 1:9), and 10% w/w or 20% w/w of medium-chain triglycerides or olive oil (oil). The self-microemulsifying ability of the prepared surfactant/cosurfactant/oil mixtures in water and 0.1 M HCl (pH 1.2), was evaluated by droplet size and zeta potential analysis and cross-polarized light microscopy. The formation of microemulsions was observed only in the presence of medium-chain triglycerides at surfactant-to-cosurfactant ratios 7:3 and 5:5 (in the mixtures containing 10% w/w of the oil phase) and 3:7 and 1:9 (when 20% w/w of the same oil was used). The obtained results provide new implications for development of microemulsion preconcentrates suitable as delivery systems for food and pharmaceutical applications.