Superparamagnetic core-shell nanoparticles as solid supports for peptide synthesis

Christian Stutz,a Idalia Bilecka,b Andreas F. Thünemann,c Markus Niederberger,b Hans G. Börner*,a

a Humboldt-Universität zu Berlin, Department of Chemistry, Laboratory of Organic Synthesis of Functional Systems, Brook-Taylor-Str. 2, Berlin 12489, Germany, Fax: +49 30 2093 7215,
b ETH Zürich, Department of Materials, Laboratory of Multifunctional Materials, Wolfgang-Pauli-Str. 10, Zürich 8093, Switzerland.
c BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, Berlin 12205, Germany.

Functional core-shell nanoparticles were synthesized by a microwave assisted route, enabling rapid and reproducible synthesis of well-defined Fe3O4@SiO2@NH2 nanoparticles with d = 6 nm magnetite core, 67 nm silica shell and approximately 2-5 nm amino functional silica layer. The constructs proved long-term resistance against acids and bases (e. g. 50% TFA in DCM for 3 h or 20% piperidine in NMP for 24 h). They could be decorated on the surfaces with Rink-amide-linkers to make the Fe3O4@SiO2@NH-(βAla)2-Rink core-shell particles applicable as colloidal supports for peptide synthesis.
Magnetic sedimentation proved to be effective means to ease of purification of the supported peptide intermediate products after each reaction step. A tetrapeptide model and a potentially bioactive undecapeptide were accessed, exhibiting both excellent purities as isolated crude products. Colloidal supports using magnetic nanoparticles span permanent surfaces and provide in contrast to the commonly used cross linked poly(styrene)-based microgels direct accessibility of reagents to the location of the synthesis.