Aqueous two-phase systems (ATPSs) have been recognized for their applications in extraction, separation, purification, and enrichment of (bio)molecules and cells. Recently, their unique ability to create aqueous-aqueous interfaces through phase separation and the characteristics of these interfaces have created new opportunities in biomedical applications. In this review, we summarize recent progress in understanding the dynamics at aqueous-aqueous interfaces, and in developing interface-assisted design of artificial cells and cyto-mimetic materials, fabrication of cyto- and bio-compatible microparticles, cell micropatterning, 3D bioprinting, and microfluidic separation of cells and biomolecules. We also discuss the challenges and perspectives to leverage the unique characteristics of ATPSs and their interfaces in broader applications.

Emerging aqueous two-phase systems: from fundamentals of interfaces to biomedical applications

Preparation and evaluation of w/o/w type emulsions containing vancomycin.

Bioactives have shown excellent protective effect against chronic diseases such as cancer, cardiovascular diseases and metabolic disorders. However, many of the bioactives like anthocyanins, carotenoids, flavonoids, vitamins and essential fatty acids are sensitive to surrounding environment stresses like pH, ionic strength, light, temperature, oxygen and gastro-intestinal (GI) conditions during transit. Hence, the functionality diminishes upon exposure to such unfriendly environment and leads to reduction in bioavailability. Double emulsions are designed to provide protection to bioactives in the innermost compartment through encapsulation and prevent loss of functionality in food matrix as well as during the GI transit. This article reviews the work done on double emulsion for food applications, covering various aspects of double emulsion like its matrix, constituents (aqueous phase, oil phase, emulsifiers, and other additives) and properties (viscosity, particle size, electrical conductivity and zeta potential). In addition to the stability of double emulsion, various means to express and modern techniques to measure it, the review also elucidates the role of newer emulsifiers and additives in improving the stability of double emulsion. The developments in target delivery of bioactives through double emulsion are highlighted. In vitro and in vivo studies proved target delivery of bioactives through double emulsion; however, confirmation through human trial is still pending.

Double Emulsions: Emerging Delivery System for Plant Bioactives

Publisher Summary This chapter discusses the multiple emulsions as targetable delivery systems The stability of a resultant multiple emulsions will depend not only on formulation variables but also on the conditions employed in its production The objectives will be to produce a multiple emulsion system that has a high yield of multiple droplets, containing the drug entrapped in the innermost phase, and for such a system to have good stability in vitro and the desired release characteristics in vivo Multiple emulsions of the w/o/w type can be used for drug delivery and drug targeting, particularly as lymphotropic agents The emulsions can be formulated using mineral or vegetable oils, and can be stabilized by a combination of lipophilic and hydrophilic emulsifiers Multiple emulsions have generally poor stability characteristics but more stable systems can be created through the use of added complexing and gelling agents

[5] Multiple emulsions as targetable delivery systems

The effect of the nature of the oil phase of w/o/w emulsions stabilized by interfacial complexation between span 80 (sorbitan mono-oleate) and albumin has been studied. The long-term stability of the systems has been assessed by photomicrography and by measuring the quantity of an internal marker (NaCl) remaining entrapped with time. The number of multiple oil drops and the diameters of the internal aqueous droplets were determined over 6 weeks, and the amounts of NaCl entrapped over the same period were followed. There were no significant changes in w/o/w emulsions prepared with a range of hydrocarbons (octane, dodecane, hexadecane, toluene and cyclohexane), indicating stable multiple emulsions. The release of NaCl and 5-fluorouracil (5-FU) separately entrapped in the internal aqueous phase of w/o/w emulsions was measured. Diffusion of the un-ionized species of 5-FU across the oil phase or through localized thin oil lamellae is the primary transport mechanism. In the presence of surface active agents, water is solubilized in inverse micelles which would possess the ability to solubilize other water-soluble components, such as NaCl and 5-FU. The mixed inverse micellar units of Span 80 and polysorbate (Tween) 80 therefore act as solute carriers across the liquid hydrocarbon membrane separating the two aqueous phases of the emulsions. The main factor in determining the differences in rates of release from the hydrocarbon emulsions appears to be the droplet size of the internal aqueous phase.

I.M. Walker

Papers

Measurement of the yield of multiple emulsion droplets by a fluorescent tracer technique

The in vivo evaluation of emulsion formulations administered intramuscularly