title: 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.
authors.affiliation: Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Anja S
authors.initials: AS
authors.lastname: Paulus
authors.affiliation: Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Raphael
authors.initials: R
authors.lastname: Heinzler
authors.affiliation: Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Huey Wen
authors.initials: HW
authors.lastname: Ooi
authors.affiliation: Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Franzreb
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D001709:Biotechnology / Q000379:methods*; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D008863:Microspheres; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry / Q000302:isolation & purification; D013696:Temperature
chemical_list: D000180:Acrylic Resins; D058185:Magnetite Nanoparticles; D011506:Proteins; C052970:poly-N-isopropylacrylamide
keywords: bioseparation process; block copolymer; magnetic microparticles; poly(N-isopropylacrylamide); stimuli-responsive material; thermoresponsive polymer