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 (eg. chlorophyllin; CHL) and/or hydrophobic (eg. lemongrass essential oil; LG-EO) active compounds. As a first step, the impact of the hydrophobic surfactant (ie. Span 80 or PGPR), sodium alginate or NaCl concentration as well as the homogenization method (ie. 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 (0.05M) and treated by highshear 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 (ie. 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 (0.05M) and treated by low-intensity UT homogenization (5,600 rpm, 2 min) followed by 24h 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.

Formation and Stabilization of W1/O/W2 Emulsions with Gelled Lipid Phases

“…W 1 /O/W 2 emulsions both with gelled and liquid lipid phases showed CHL EE values higher than 98%. Our results are in agreement with a previous study where the CHL EE values in liquid lipid W 1 /O/W 2 emulsions were around 91% [ 3 ]. Interestingly, in this study, emulsions containing lecithin had the highest CHL EE, which might be due to a possible interaction between the phosphate ions of lecithin and the hydroxyl groups of the encapsulated compound, being capable of forming H-bonds with the CHL.…”

“…W 1 /O/W 2 were prepared according to a two-step emulsification method previously used by Artiga-Artigas et al [ 3 ] with some modifications, consisting on the formation of the W 1 /O emulsion followed by its dispersion in an outer aqueous phase.…”

“…The most common method to fabricate W 1 /O/W 2 emulsions consist of a two-step process in which an initial step of making the W 1 /O emulsion is followed by its dispersion in another aqueous phase [ 1 ]. Due to the compartmentalized internal structure, W 1 /O/W 2 emulsions offer great potential for the encapsulation and controlled release of hydrophilic bioactive compounds [ 2 , 3 ]. However, in these systems, multiple instability mechanisms can occur during their production and storage, such as coalescence of the lipid droplets and/or inner water droplets, and the coalescence of the inner water droplets with the outer water phase, which leads to water migration between both water phases.…”

“…In principle, in order to form a W 1 /O/W 2 emulsion, an initial lipophilic emulsifier is used for the stabilization of the inner interface. Polyglycerol ester of polyricinoleic acid (PGPR) has been demonstrated to be highly effective as W 1 /O stabilizer, due to its ability to form small W 1 droplets, and because it forms a physical barrier around these droplets preventing their coalescence [ 3 , 9 ]. To stabilize the second interface, it is necessary to use a hydrophilic emulsifier.…”

The Stability, Microstructure, and Microrheological Properties of Monascus Pigment Double Emulsions Stabilized by Polyglycerol Polyricinoleate and Soybean Protein Isolate

“…Water-in-oil-in-water (W/O/W) emulsions are complex liquid dispersion systems known also as double emulsions, in which a water-in-oil emulsion dispersed in a second continuous water phase (9)(10)(11). It is reported that double emulsions can be used to protect and control release of bioactive compounds (12,13).…”