Formation of Double (W1/O/W2) Emulsions as Carriers of Hydrophilic and Lipophilic Active Compounds

Abstract

This work aimed at obtaining an optimized formation procedure of water-in-oil-in-water (W1/O/W2) double emulsions as potential templates to carry hydrophilic (e.g., chlorophyllin; CHL) and/or hydrophobic (e.g., lemongrass essential oil; LG-EO) active compounds. As a first step, the impact of the hydrophobic surfactant (i.e., Span 80 or PGPR), sodium alginate or NaCl concentration as well as the homogenization method (i.e., high-shear homogenization, ultrasonication, or microfluidization) on the particle size of the primary W1/O emulsions was evaluated. The inner phase (W1/O) formulated with PGPR (4% w/w) and sodium alginate (2% w/w) with NaCl (0.05 M) and treated by high-shear homogenization (11,000 rpm, 5 min) presented the smallest particle size (d[4;3] ≈ 0.51 μm). As a second step, the primary W1/O emulsion was subsequently dispersed in a secondary aqueous phase (W2) at varying hydrophilic surfactant (i.e., lecithin or Tween 20), sodium alginate or NaCl concentrations and magnetic stirring rate (rpm and time) to obtain double emulsions (W1/O/W2). The formation of stable W1/O/W2 emulsions with d[4;3] of 7 μm was achieved with the use of lecithin (2% w/w), sodium alginate (2% w/w) with NaCl (0.05 M) and treated by low-intensity UT homogenization (5600 rpm, 2 min) followed by 24 h of magnetic stirring. The incorporation of CHL and LG-EO in the inner aqueous phase and lipid phase respectively did not change the double emulsion characteristics. Overall, this study presents an effective two-step optimized procedure to form stable double emulsions as potential delivery systems for functional compounds.