Restricted and Unrestricted Migration Mechanisms of Silica Nanoparticles in Agarose Gels and Their Utilization for the Separation of Binary Mixtures

Abstract

The migration of SiO2 nanoparticles (NPs) was investigated during agarose gel electrophoresis with various gel mesh sizes. As a model system, spherical SiO2 NPs of different sizes were synthesized by Stöber synthesis, and the surface was modified by covalently binding different types of ligands to tailor the ζ-potential as required. In the following step, agarose gels were cast with Tris/borate/EDTA (TBE) buffer solution, thereby controlling the mesh sizes by varying agarose concentrations, with higher concentrations leading to smaller mesh sizes. Additionally, the applied voltage could be varied for different electrophoretic experiments. Generally, large mesh sizes and high applied voltages lead to faster particle migration. The migration of SiO2 NPs occurs under two regimes: restricted migration, where small mesh size interferes with large particles so that the gel is acting similar to a sieve; and unrestricted migration, where the mesh size does not influence the particles’ migration behavior and they move according to their ζ-potential. Following these regimes, two different mechanisms of NP separation were possible inside agarose gels. Both mechanisms were used to separate binary mixtures into the former individual fractions, as proven by scanning electron microscopy (SEM) or the ninhydrin test.

Size fractionation of magnetic nanoparticles by magnetic chromatography

“…In this context, size separation means a selective fractionation of particles with a broad size distribution into two or more fractions, which differ in their mean particle diameter. So far, various processes have been investigated for this purpose, including micro-and ultrafiltration [25,26], acoustic fractionation [23,27], gel electrophoresis [28] and ultracentrifugation [29,30]. An established separation process for MNPs is the use of so-called high gradient magnetic separators [31,32].…”

Aufreinigung von Nano‐ und Submikronpartikeln durch präparative Gelelektrophorese

“…30 min). Im Anschluss wurde dann ein Teil entfernt und mit einem ho ¨her konzentrierten Gel (1,20 Die Synthese der Gold-NP wurde mittels einer seededgrowth-Synthese realisiert [16]. Zuna ¨chst wurden Gold(III)chlorid-Hydrat (HAuCl 4 Á 3 H 2 O, 49 %), Hexadecyltrimethylammoniumbromid CTAB ( 99 %), Hexadecyltrimethylammoniumchlorid CTAC ( 25 % in H 2 O) und Natriumborhydrid NaBH 4 ( 98 %) sowie Ascorbinsa ¨ure ( 99 %) in definierten Mengen gemischt, um Au-Keime von < 5 nm Gro ¨ße zu erhalten [29].…”

“…Dabei wurde beobachtet, dass das Verhältnis der Partikelgröße zur Maschenweite der essenzielle Parameter ist, der die Wanderung maßgeblich beeinflusst. Es stellen sich zwei Migrationsregime ein: eine uneingeschränkte Wanderung, bei der die Partikelgröße viel kleiner als die Maschenweite ist und das Gel somit keinen signifikanten Einfluss ausübt, und die eingeschränkte Wanderung, bei der durch das Gel eine Art Siebeffekt auftritt 16.…”

Magnetic/flow controlled continuous size fractionation of magnetic nanoparticles using simulated moving bed chromatography

“…Size fractionation in this context refers to selective fractionation of particles with a wide size distribution into two or more fractions that differ among each other in their median particle diameter. On an analytical scale, other innovative methods have already been investigated for this purpose, including microfiltration and ultrafiltration [28,29], acoustic fractionation [30,31] or gel electrophoresis [32]. Furthermore, due to their magnetic addressability, processing of MNPs is widely carried out using so-called high gradient magnetic separation (HGMS) [33,34].…”