Combining Step Gradients and Linear Gradients in Density

Abstract

Combining aqueous multiphase systems (AMPS) and magnetic levitation (MagLev) provides a method to produce hybrid gradients in apparent density. AMPS solutions of different polymers, salts, or surfactants that spontaneously separate into immiscible but predominantly aqueous phasesoffer thermodynamically stable steps in density that can be tuned by the concentration of solutes. MagLevthe levitation of diamagnetic objects in a paramagnetic fluid within a magnetic field gradientcan be arranged to provide a near-linear gradient in effective density where the height of a levitating object above the surface of the magnet corresponds to its density; the strength of the gradient in effective density can be tuned by the choice of paramagnetic salt and its concentrations and by the strength and gradient in the magnetic field. Including paramagnetic salts (e.g., MnSO 4 or MnCl 2 ) in AMPS, and placing them in a magnetic field gradient, enables their use as media for MagLev. The potential to create large steps in density with AMPS allows separations of objects across a range of densities. The gradients produced by MagLev provide resolution over a continuous range of densities. By combining these approaches, mixtures of objects with large differences in density can be separated and analyzed simultaneously. Using MagLev to add an effective gradient in density also enables tuning the range of densities captured at an interface of an AMPS by simply changing the position of the container in the magnetic field. Further, by creating AMPS in which phases have different concentrations of paramagnetic ions, the phases can provide different resolutions in density. These results suggest that combining steps in density with gradients in density can enable new classes of separations based on density.

Magnetic Levitation in Chemistry, Materials Science, and Biochemistry

“…Air bubble mm~0N dFeB 0.4 MnCl 2 in water [22,93] Polymer particles (PMMA, PS, Nylon, etc.) mm-mm 0.9-2.3 NdFeB 0.4 MnCl 2 /GdCl 3 in water and alcohol [20,42,44,74,86,[93][94][95] Organic liquids (e.g.,chlorobenzene, 2-nitrotoluene, dichloromethane, 3-bromotoluene, and chloroform. )…”

“…[94] Foreach paramagnetic phase in an AMPS,t he applied magnetic field creates an effective linear gradient in density in it, and the specific range of accessible density depends on the location of the phase in the applied magnetic field and also the concentration of the paramagnetic species.T he applied magnetic field, therefore, effectively transforms simple steps in density of ap aramagnetic AMPS (in the absence of an applied magnetic field, Figure 3G)t oah ybrid profile combining step and linear gradients in density.Since the range of densities accessible in each phase depends on their physical locations in the applied magnetic field, it is,t herefore,p articularly convenient to adjust the apparent densities of the phases-and by inference, the "density bins" at the interfaces-by repositioning the Reticulocytes mm1 .08 2F icoll/dextran [118] Bacteria mm1 .03-1.10 2P EG/Ficoll [150] Angewandte Chemie Reviews interfaces in the applied magnetic field, without having to adjust the chemical composition of the AMPS.F igure 3H demonstrates this capability of adjusting the effective step in density in aparamagnetic two-phase system by repositioning the interface relative to the bottom surface of the magnet. [94] Thec ombined use of AMPS and MagLev provides an operationally straightforward method to generate complex profiles of gradients in density-combining step and linear gradients-and, therefore,p rovides both au niquely flexible capability to develop solutions to problems in density-based separations, [94] and am ethod of discovering new phenomena in MagLev. Aqueous multiphase systemsa nd their combinedu se with MagLev (A) Af ive-phase AMPS forms upon centrifugation, and density standards (colored glass beads) indicate the densitiesa tthe interfaces.…”

“…Sources:Images (A), [130] (B), [118] (C), [131] and (D-H). [94] 3.3.6. Colloidal Systems:F errofluids Af errofluid is typically ac olloidal system in which~10nm superparamagnetic particles (e.g.,o fm agnetite) are suspended in ac arrier fluid.…”

Magnetische Levitation in Chemie, Materialwissenschaft und Biochemie

“…B. Zellen, Organellen, Bakterien, Viren, Proteinen und Nukleinsäuren) wird für die Fraktionierung verwendet (z. B. zur Abtrennung von Viren oder Bakterien in einem Gemisch mit Säugetierzellen) [94, 117–120] . Die Dichte kann auch verwendet werden, um das Wachstum von Zellen während eines Zellzyklus zu verfolgen und die pathophysiologischen Veränderungen im Zusammenhang mit Infektionen oder genetischen Störungen zu analysieren) [121] …”

“…Der Behälter (die feste Phase) in (H) ist eine Küvette aus PMMA. Quellen: Bilder (A), [130] (B), [118] (C), [131] und (D–H) [94] …”