Modulating the Partitioning of Microparticles in a Polyethylene Glycol (PEG)-Dextran (DEX) Aqueous Biphasic System by Surface Modification

Abstract

Aqueous two-phase systems (ATPSs) or aqueous biphasic systems are useful for biological separation/preparation and cell micropatterning. Specifically, aqueous two-phase systems (ATPSs) are not harmful to cells or biomaterials; therefore, they have been used to partition and isolate these materials from others. In this study, we suggest chemically modifying the surface of target materials (micro/nanoparticles, for example) with polymers, such as polyethylene glycol and dextran, which are the same polymer solutes as those in the ATPS. As a simple model, we chemically coated polyethylene glycol or dextran to the surface of polystyrene magnetic particles and observed selective partitioning of the surface modified particles to the phase in which the same polymer solutes are dominant. This approach follows the principle "like dissolves like" and can be expanded to other aqueous biphasic or multiphasic systems while consuming fewer chemicals than the conventional modulation of hydrophobicities of solute polymers to control partitioning in aqueous biphasic or multiphasic systems.

Immunostaining Extracellular Vesicles Based on an Aqueous Two-Phase System: For Analysis of Tetraspanins

“…This phenomenon happens because unbound antibodies have a stronger affinity to the PEG phase than protein contents due to their hydrophobicity. 21,30 Figure 2c clearly shows the visual proof of ATPS-washing of antibodies. The unwashed (0th) sample is easily distinguishable from washed samples because its fluorescence image is saturated with fluorescence from unbound antibodies.…”

“…For this purpose, an extraction method based on an aqueous two-phase system (ATPS) may be applicable due to the ability to purify biological molecules from biological samples. The ATPS is a phenomenon where two phases spontaneously separate to form a stable biphasic system when the concentration of a polymer–polymer/polymer–salt combination in an aqueous solution exceeds a certain critical point. − According to their affinity to the solutes, the molecules in the system partition accordingly. ,,, The interfacial stress between the phases is usually very low, enabling a gentle separation that does not denature or harm the partitioning molecules. ,, Researchers have utilized this property of the ATPS in separating a variety of particles, including but not limited to biomolecules, metal ions, and even carbon nanotubes, from various samples. ,,, Some researchers have even successfully utilized the ATPS to achieve micropatterning of cells and antibodies for various bioassays and co-cultures. − In addition, the volume ratio of separated phases is adjustable according to the solute concentration, enabling enrichment of the target molecule. Utilizing these properties, the ATPS was utilized in EV separation and purification with high recovery rates as high as ∼90%, while EV isolation using ultracentrifugation recovered only about 25% of the EVs. ,, We have suspected that these features of the ATPS could make ATPS-based biomolecule extraction a potent tool in EV washing after the immunostaining.…”

“…16−19 According to their affinity to the solutes, the molecules in the system partition accordingly. 17,18,20,21 The interfacial stress between the phases is usually very low, enabling a gentle separation that does not denature or harm the partitioning molecules. 16,17,22 Researchers have utilized this property of the ATPS in separating a variety of particles, including but not limited to biomolecules, metal ions, and even carbon nanotubes, from various samples.…”

Novel approach for neuronal stem cell differentiation using aqueous two‐phase systems in 3D cultures

“…Improvements regarding technical processes have been developed, highlighting the use of acoustic droplet ejection in an exclusion patterning system to produce uniform droplet size through ultrasound parameters, enhancing co‐cultures without cross‐contamination 25 . To alter the partition effect, polystyrene‐coated microparticles conjugated with DEX have been performed 26 . To promote 3D cell assembly, the encapsulation of mesenchymal stem cells and fibroblasts was improved by crosslinking DEX with glycidyl methacrylate and dithiothreitol 27 .…”

“…25 To alter the partition effect, polystyrene-coated microparticles conjugated with DEX have been performed. 26 To promote 3D cell assembly, the encapsulation of mesenchymal stem cells and fibroblasts was improved by crosslinking DEX with glycidyl methacrylate and dithiothreitol. 27 Likewise, to generate thin layers, a combination of Matrigel and ECM-based hydrogels with hydroxypropylmethylcellulose (HPMC) and DEX was developed to promote spheroid formation.…”