Production of multiple emulsions for drug delivery systems by repeated SPG membrane homogenization: Influence of mean pore size, interfacial tension and continuous phase viscosity

Modification of interfacial characteristics of monodisperse droplets produced using membrane emulsification by surfactant displacement and/or polyelectrolyte electrostatic deposition

“…In the fourth and fifth pass, the median drop size remained virtually constant at about 7 µm with the flux value approaching 79 m 3 m -2 h -1 (Fig. 6), which is equivalent to the production rate of 50 g of emulsion in less than 6 s. The final median drop size was smaller than the membrane pore size, which was the behavior observed earlier using SPG membranes with a mean pore size of 8 and 10.7 µm [3][4][5]. In Figure 6 the mean transmembrane fluxes are presented as a function of number of passes.…”

“…4, the flux during first pass was indeed very high until about 60 g of the permeate had been passed and after that the flux rapidly declined due to sudden rise in the drop concentration. In premix membrane emulsification, transmembrane pressure, ∆p tm provides energy for flow through the membrane and for droplet breakup [5]:…”

“…Membrane emulsification is a relatively new technique for producing uniform micron-sized drops based on: (i) in situ drop generation by permeation of pure dispersed phase through a porous membrane into the continuous phase ('direct membrane emulsification') [1,2], or (ii) passing a pre-emulsified mixture through a porous membrane ('premix membrane emulsification') [3][4][5][6].…”

“…Shirasu Porous Glass (SPG) membranes are one of the most widely used microporous media for membrane emulsification [1][2][3][4][5][6][8][9][10] due to their uniformly sized pores [11], uniform internal microstructure with no microscopic voids or cracks [12], and a wide range of commercially available mean pore diameters (0.05-50 µm) [13]. An untreated SPG membrane has a negative zeta-potential of −15 to −35 mV within a pH range of 2-8, due to dissociation of residual silanol groups on the surface and formation of SiO − sites.…”

“…Nonionic surfactants (Tweens) have been found to be particularly effective at preparing uniform oil-in-water and oil-in-water-in-oil multiple emulsions by premix SPG membrane emulsification [3,5]. However, oil drops stabilised by nonionic surfactants are not suitable for some applications due to their relatively low net charge.…”