Use of peptide functionalized Dynabeads for the magnetic carrier separation of Rare Earth phosphors in low and high magnetic field gradients

Superparamagnetic composite beads are widely used as magnetic carriers in biotechnological processes, including the purification of biomolecules, organelles and cells [1,2]. Their wide range of applications include diagnostic, as well as industrial purposes. Furthermore, the immobilization of surface-binding peptides can render highly specific surface properties to composite beads and facilitate their selective interaction with target particles. In this context, peptide functionalized composite beads have been shown to be promising tools for environmental applications, including biomining and wastewater treatment [3-5]. Nevertheless, to the best of our knowledge, their use has so far only been investigated in low magnetic field gradients, on a milliliter scale.

The waste of fluorescent lamps contains several valuable Rare Earth phosphors in the form of fine particles that are hard to separate and therefore lack efficient recycling schemes [6]. Our junior researchgroup, BioKollekt, has previously identified selectively surface-binding peptides that interact with the Rare Earth phosphor LaPO4:Ce,Tb [7]. Recently, we have chemically immobilized the identified peptides and have tested their interaction with several target phosphors [8], we have thoroughly characterized a range of Rare Earth phosphors and we have shown their compatibility with an upscalable High-Gradient Magnetic Separator [9], which was specifically designed for biotechnological separations with superparamagnetic carriers [10].

In this work, we investigate the use of Dynabeads® M-270, functionalized with previously identified peptides, for the separation of Rare Earth phosphors. First, we characterize the physical properties of functionalized and unfunctionalized beads. Subsequently, we examine the beads’ selectivities towards various Rare Earth phosphors in an LGMS setup. Finally, we compare the carrier behaviour of the beads in low and high magnetic field gradients by the use of an optical microscopic setup. A special focus is placed on the magnetically induced chain formation by sets of beads. Finally, this work can shine a light on the future perspectives of peptide functionalized superparamagnetic composite beads for a selective and upscalable separation process of fine particles.

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