Temperature-Switchable Agglomeration of Magnetic Particles Designed for Continuous Separation Processes in Biotechnology

Abstract

The purpose of this work was the synthesis and characterization of thermally switchable magnetic particles for use in biotechnological applications such as protein purification and enzymatic conversions. Reversible addition-fragmentation chain-transfer polymerization was employed to synthesize poly(N-isopropylacrylamide) brushes via a "graft-from" approach on the surface of magnetic microparticles. The resulting particles were characterized by infrared spectroscopy and thermogravimetric analysis and their temperature-dependent agglomeration behavior was assessed. The influence of several factors on particle agglomeration (pH, temperature, salt type, and particle concentration) was evaluated. The results showed that a low pH value (pH 3-4), a kosmotropic salt (ammonium sulfate), and a high particle concentration (4 g/L) resulted in improved agglomeration at elevated temperature (40 °C). Recycling of particles and reversibility of the temperature-switchable agglomeration were successfully demonstrated for ten heating-cooling cycles. Additionally, enhanced magnetic separation was observed for the modified particles. Ionic monomers were integrated into the polymer chain to create end-group functionalized particles as well as two- and three-block copolymer particles for protein binding. The adsorption of lactoferrin, bovine serum albumin, and lysozyme to these ion exchange particles was evaluated and showed a binding capacity of up to 135 mg/g. The dual-responsive particles combined magnetic and thermoresponsive properties for switchable agglomeration, easy separability, and efficient protein adsorption.

Kinetic and Thermodynamic Effects on the Agglomeration of Magnetite Nanoparticles by Magnetic Field

“…3,4 Magnetic weight of magnetic nanoparticle, which appears by magnetization of nanoparticle, can be measured with a conventional electronic balance. 5,6 When the magnetic field from a small disc magnet is applied to the superparamagnetic magnetite solution, the magnetic weight of the sample jumps instantaneously (<<1 s) by the Neel and Brown mechanism.…”

“…Solution of magnetic nanoparticles called ferrofluid shows the well‐known interesting morphological behaviors under magnetic field . Magnetic nanoparticles of relatively low concentration agglomerate by magnetic field . Agglomeration of magnetite nanoparticles under low magnetic field (<100 T/m) is used in the protein purification or the separation of magnetic impurities for water purification …”

Thermoresponsive-polymer-based materials for temperature-modulated bioanalysis and bioseparations

“…Thermoresponsive chromatographic techniques for separating bioactive compounds and proteins while retaining their biological activities, and cell-separation techniques that do not require cell-surface modification are reviewed. We focused on these two topics to limit the length of the review; however, there are other bioanalytical and bioseparation techniques such as those using thermoresponsive-polymer-modified membranes, [38][39][40] magnetic beads, 41,42 and microfluidic techniques. 40,[43][44][45]…”

Effects of Sample Container Morphology on Agglomeration Dynamics of Magnetite Nanoparticles under Magnetic Field

“…The magnetite nanoparticles agglomerate via interparticle interactions enhanced by magnetic field, and the magnetization of the sample increases with agglomeration. The superparamagnetic magnetite nanoparticles have been used extensively in medical and biological applications, and agglomeration of magnetic nanoparticles is employed in the purification of water and proteins . The magnetic weight can be measured with a conventional electronic balance.…”

“…The superparamagnetic magnetite nanoparticles have been used extensively in medical and biological applications, 4,5 and agglomeration of magnetic nanoparticles is employed in the purification of water and proteins. 6,7 The magnetic weight can be measured with a conventional electronic balance. Details of the experimental setup have been previously reported.…”