Water fluxes and encapsulation efficiency in double emulsions: impact of emulsification and osmotic pressure unbalance

Abstract

We study the influence of the emulsification process on encapsulation efficiency of drugs in double water-in-oil-in-water emulsions. Two drugs were used, first vitamin B12 which can be considered as a model drug and secondly a suspension of Cydia pomonella Granulovirus (CpGV), a virus used in organic agriculture to protect fruits against the Carpocapse insect. Encapsulation is measured by classical UV-Vis spectroscopy method. Additionally we show that rheology is a useful tool to determine water exchanges during emulsification. In a two-step emulsification process, using rotor-stator mixers, encapsulation reaches high levels, close to 100% whatever the flowing regime. This encapsulation decreases only if two conditions are fulfilled simultaneously: (i) during the second emulsification step the flow is turbulent and (ii) it leads to excessive fragmentation inducing formation of too small drops. We also investigate the effect of a deliberate loss of osmotic pressure balance on the encapsulation and characterize the induced water fluxes. We show that encapsulation of vitamin B12 is not affected by the osmotic pressure unbalance, while water exchanges, if they exist, are very fast and aim at restoring equilibrium. As a consequence, the emulsification efficiency is not very sensitive to osmotic stresses provided that the interfaces resist mechanically.

Cross-linking of double oil-in-water-in-oil emulsions: A new way for fragrance encapsulation with tunable sustained release

“…Coalescence events could also have occurred before the polymerization explaining the encapsulation decrease [49,50]. Knowing the drop and globule sizes as well as the droplet volume fraction, the number of coalescence events leading to a decrease of the encapsulation by 20% can be estimated [51]. This corresponds to 135 coalescence events.…”

Synthesis of Oil-Laden Poly(ethylene glycol) Diacrylate Hydrogel Nanocapsules from Double Nanoemulsions

“…43,[50][51][52][53][54][55] Unlike single emulsions, whose stability can be inferred from changes in their droplet size distribution alone, the stability of double emulsions is additionally characterized by the amount of inner droplet phase retained within the outer droplet phase, i.e., the encapsulation efficiency. 53 Most studies of encapsulation efficiency have been in W/O/W emulsions, where efficiency is typically measured either by encapsulating a water-soluble molecular probe (e.g. NaCl) and measuring its release profile under different compositional makeup and processing conditions, or using in situ microscopy to track the size distribution and amount of the inner phase.…”

W/O/W Multiple Emulsions as the Functional Component of Dairy Products

“…One way to improve the thermodynamic stability of w/o/w emulsions is by incorporation of electrolytes, sugars, or hydrocolloids. These components (osmotic regulators) enable maintenance of osmotic balance [1,100,[105][106][107]. The Laplace pressure formula (Eq.…”

“…Highly monodisperse emulsions can also be prepared using the microfluidic capillary flow technique under strict laboratory conditions. Then, each monodisperse outer droplet contains a certain number of internal water droplets, which are identical [1,52,68,101,106,[170][171][172].…”