Rare Earth phosphor-binding peptides for the functionalization of magnetic nanoparticles and application in biomagnetic separation

In a global effort towards a low-carbon and green economy, the ongoing search for novel techniques to recycle rare-earth elements (REEs) will play a crucial role, due to their increasing demand, high supply risk and incompatibility with conventional separation methods [1,2]. In this context, surface-binding peptides immobilized on magnetic carriers can facilitate highly specific interactions with their target materials to promote highly innovative and selective particle separation processes [3].
Previously, the Junior Research Group BioKollekt has applied Phage Surface Display to succesfully identify selectively surface-binding peptides that interact with the commercially applied green phosphor LaPO4:Ce,Tb [4]. Subsequently, we have thoroughly characterized a range of REE phosphors, commercially applied in fluorescent lamps, and have proven their compatibility with an upscalable biotechnological high-gradient magnetic separator [5]. Furthermore, we have investigated the interaction of the identified peptides with the target phosphors, in dissolved as well as chemically immobilized conformations [6].
In this work, we present the use of REE phosphor-binding peptides for the functionalization of magnetic nanoparticles by chemical immobilization. We give a comprehensive overview of the peptides’ roles in the nanoparticle functionalization, interaction with the target phosphors and an upscalable biomagnetic separation, as summarized in Fig. 1. Amongst others, we present the surface load of the immobilized peptides on the nanoparticles, as well as surface zeta potential measurement.
Finally, this work can shine a light on the future perspectives of peptides for their role in selective particle separation processes for environmental applications.

REFERENCES
[1] European Commission, Study on the EU’s list of Critical Raw Materials – Final Report (2020).
[2] Binnemans, K.; Jones, P.; Blanpain, B.; Van Gerven, T.; Yang, Y.; Walton, A.; Buchert, M. Recycling of Rare Earths a Critical Review. Journal of Cleaner Production 2013, 51, 1-22, doi:10.1016/j.jclepro.2012.12.037.
[3] Pollmann, K.; Kutschke, S.; Matys, S.; Raff, J.; Hlawacek, G.; Lederer, F. Bio-recycling of metals: Recycling of technical products using biological applications. Biotechnol. Adv. 2018, 36, doi:10.1016/j.biotechadv.2018.03.006.
[4] Lederer, F.; Curtis, S.; Bachmann, S.; Dunbar, S.; MacGillivray, R. Identification of lanthanum-specific peptides for future recycling of rare earth elements from compact fluorescent lamps: Peptides for Rare Earth Recycling. Biotechnol. Bioeng. 2016, 114, doi:10.1002/bit.26240.
[5] Boelens, P.; Lei, Z.; Drobot, B.; Rudolph, M.; Li, Z.; Franzreb, M.; Eckert, K.; Lederer, F. High-Gradient Magnetic Separation of Compact Fluorescent Lamp Phosphors: Elucidation of the Removal Dynamics in a Rotary Permanent Magnet Separator. Minerals 2021, 11, doi:10.3390/min11101116.
[6] Schrader, M.; Bobeth, C.; Lederer, F. Quantification of Peptide-Bound Particles: A Phage Mimicking Approach via Site-Selective Immobilization on Glass. ACS Omega 2021, XXXX, doi:10.1021/acsomega.1c04343.