Greening perfluorocarbon based nanoemulsions by direct membrane emulsification: Comparative studies with ultrasound emulsification

Abstract

A systematic experimental methodology was employed to produce oil-in-water (O/W) nanoemulsions by direct membrane emulsification while exploring first-ever studies on using polymeric membranes. Perfluorodecalin (PFD) constituted the dispersed phase and the continuous phase was an aqueous solution of two surfactants, Tween 80 and (1H,1H,2H,2H-perfluorooctyl)phosphocholine (FC8). This work aimed to formulate monomodal PFD-based nanoemulsions having a narrow-sized distribution with mean droplet sizes of around 150 nm or below, suitable for biomedical applications. Relevant processing conditions of membrane emulsification were optimised, and a monomodal emulsion of 103.4 ± 2.6 nm was achieved using an isoporous Nuclepore track-etched 30 nm nominal pore diameter membrane. In comparison to the reported ultrasound emulsification studies with the same colloidal system, direct membrane emulsification offered several advantages, such as electrokinetically stable nanoemulsions with a 40% reduction in the emulsion droplet sizes. Additionally, 36 times lower molar concentration of optimised surfactants’ composition were sufficient. Besides, interfacial tensions between the oil and aqueous phases were determined to explain the observed emulsion droplet sizes. Lastly, a critical analysis to determine energy expenditure and energy requirement to create nanoemulsion surface area, favourably indicates that the membrane-based process ensures a 99.5% reduction of energy expenditure to produce the same surface area.