Production of uniform droplets using membrane, microchannel and microfluidic emulsification devices

This review provides an overview of major microengineering emulsification techniques for production of monodispersed droplets. The main emphasis has been put on membrane emulsification using Shirasu Porous Glass and microsieve membrane, microchannel emulsification using grooved-type and straight-through microchannel plates, microfluidic junctions and flow focusing microfluidic devices. Microfabrication methods for production of planar and 3D poly(dimethylsiloxane) devices, glass capillary microfluidic devices and single-crystal silicon microchannel array devices have been described including soft lithography, glass capillary pulling and microforging, hot embossing, anisotropic wet etching and deep reactive ion etching. In addition, fabrication methods for SPG and microseive membranes have been outlined, such as spinodal decomposition, reactive ion etching and ultraviolet LIGA (Lithography, Electroplating, and Moulding) process. The most widespread application of micromachined emulsification devices is in the synthesis of monodispersed particles and vesicles, such as polymeric particles, microgels, solid lipid particles, Janus particles, and functional vesicles (liposomes, polymersomes and colloidosomes). Glass capillary microfluidic devices are very suitable for production of core/shell drops of controllable shell thickness and multiple emulsions containing a controlled number of inner droplets and/or inner droplets of two or more distinct phases. Microchannel emulsification is a very promising technique for production of monodispersed droplets with droplet throughputs of up to 100 l h−1

Production of biocompatible gold nanoparticles for drug delivery using droplet based glass capillary microfluidic [Abstract]

Production of biocompatible gold nanoparticles for drug delivery using droplet based glass capillary microfluidic [Abstract

Polycaprolactone multicore-matrix particle for the simultaneous encapsulation of hydrophilic and hydrophobic compounds produced by membrane emulsification and solvent diffusion processes

Co-encapsulation of drugs in the same carrier, as well as the development of microencapsulation processes for biomolecules using mild operating conditions, and the production of particles with tailored size and uniformity are major challenges for encapsulation technologies. In the present work, a suitable method consisting of the combination of membrane emulsification with solvent diffusion is reported for the production of multi-core matrix particles with tailored size and potential application in multi-therapies. In the emulsification step, the production of a W/O/W emulsion was carried out using a batch Dispersion Cell for formulation testing and subsequently a continuous azimuthally oscillating membrane emulsification system for the scaling-up of the process to higher capacities. In both cases precise and gentle control of droplet size and uniformity of the W/O/W emulsion was achieved, preserving the encapsulation of the drug model within the droplet. Multi-core matrix particles were produced in a post emulsification step using solvent diffusion. The compartmentalized structure of the multicore-matrix particle combined with the different chemical properties of polycaprolactone (matrix material) and fish gelatin (core material) was tested for the simultaneous encapsulation of hydrophilic (copper ions) and hydrophobic (α-tocopherol) test components. The best operating conditions for the solidification of the particles to achieve the highest encapsulation efficiency of copper ions and α-tocopherol of 99 (±4)% and 93(±6)% respectively were found. The multi-core matrix particle produced in this work demonstrates good potential as a co-loaded delivery system

Preparation of microemulsions and nanoemulsions by membrane emulsification

This paper is an overview of the applications of microporous membranes for preparation of micro/nano- emulsions. Membrane emulsification offers compact devices for preparation of nanoemulsions with low energy consumption, tuneable droplet size, monomodal distribution, and high encapsulation efficiency of entrapped functional components without shear or thermal degradation. The properties and wettability modification of Shirasu Porous Glass (SPG) membrane, track-etched polymeric sheets, syringe filters, anodic alumina membrane, and nickel-based superalloy membranes were discussed, as well as the design and operation of membrane devices. Particular emphasis was placed on the effect of formulation, operating parameters, and membrane properties on the resulting droplet size in direct and premix membrane emulsification with the examples of nano-sized emulsions produced using different membranes. The application of microemulsions prepared using synthetic membranes for production of solid self-microemulsifying drug delivery systems for enhanced solubility and oral bioavailability of BSC Class II and III drugs was also reviewed, as well as production of solid nanoparticles such as nanogels, solid lipid nanoparticles, synthetic biodegradable polymer nanoparticles, silica and metal oxide nanoparticles from nanoemulsion templates prepared by membrane emulsification

Membrane-assisted liquid phase extraction of Lu(III) in U-shaped contactor with a single hollow fibre membrane under recirculation mode of operation

Extraction of Lu(III) from an aqueous LuCl3 solution at pH 3.5 into an organic phase containing 5% (v/v) di(2-ethylhexyl)phosphoric acid (DEHPA) in di-n-hexyl ether (DHE) immobilized within a polypropylene hollow fibre membrane and a simultaneous back-extraction of Lu(III) into 2 mol dm-3 HCl solution has been investigated using two miniaturized supported liquid membrane (SLM) systems: (i) a single hollow fibre membrane, with stagnant acceptor phase in the lumen, immersed into a donor phase reservoir; (ii) U-shaped module containing a single hollow fibre membrane with a closed-loop recirculation of aqueous phases through the module. In the stagnant SLM system, the maximum extraction efficiency was 8.8% due to limited acceptor volume and absence of flow within the lumen. In recirculating SLM system, after 80 min of operation at the donor phase flow rate of 5.3 cm3 min-1, the acceptor phase flow rate of 0.4 cm3 min-1 and the donor-to-acceptor phase volume ratio of 6.7, the equilibrium removal efficiency of Lu(III) reached 88% and less than 5% of Lu(III) extracted from the feed solution was kept in the organic phase. For shell side flow of the donor phase at the Reynolds number of 3−34, the overall mass transfer coefficient was proportional to the donor flow rate raised to the power of 0.63 and increased from 2.3 to 8.8 × 10-5 m s-1. The rate-limiting step was the mass transfer of Lu(III) within the boundary layer of the donor phase adjacent to the outer wall of the hollow fibre

Kinetics of the pre-treatment of used cooking oil using Novozyme 435 for biodiesel production [conference paper]

The pretreatment of used cooking oil (UCO) for the preparation of biodiesel has been investigated, using Novozyme 435, Candida antarctica Lipase B immobilized on acrylic resin, as the catalyst. The reactions in UCO were carried out using a jacketed batch reactor with a reflux condenser. The liquid chromatography mass spectrometry (LC-MS) method was developed to monitor the mono-, di and triglyceride concentrations for this work and it has been shown that it is possible to obtain linear calibration curves. This work showed that Novozyme 435 will catalyse the esterification of FFAs and the transesterification of mono- and diglycerides typically found in UCO when Novozyme 435 is used to catalyse the pretreatement of UCO for the formation of biodiesel

Microencapsulation of oil droplets using cold water fish gelatine/gum arabic complex coacervation by membrane emulsification

Food grade sunflower oil was microencapsulated using cold water fish gelatine (FG)–gum arabic (GA) complex coacervation in combination with a batch stirred cell or continuous pulsed flow membrane emulsification system. Oil droplets with a controllable median size of 40–240 μm and a particle span as low as 0.46 were generated using a microengineered membrane with a pore size of 10 μm and a pore spacing of 200 μm at the shear stress of 1.3–24 Pa. A biopolymer shell around the oil droplets was formed under room temperature conditions at pH 2.7–4.5 and a total biopolymer concentration lower than 4% w/w using weight ratios of FG to GA from 40:60 to 80:20. The maximum coacervate yield was achieved at pH 3.5 and a weight ratio of FG to GA of 50:50. The liquid biopolymer coating around the droplets was crosslinked with glutaraldehyde (GTA) to form a solid shell. A minimum concentration of GTA of 1.4 M was necessary to promote the crosslinking reaction between FG and GTA and the optimal GTA concentration was 24 M. The developed method allows a continuous production of complex coacervate microcapsules of controlled size, under mild shear stress conditions, using considerably less energy when compared to alternative gelatine types and production methods