Facile synthesis of magnetic metal organic frameworks for the enrichment of low‐abundance peptides for MALDI‐TOF MS analysis

In this work, core‐shell magnetic metal organic framework (MOF) microspheres were successfully synthesized by coating magnetite particles with mercaptoacetic acid and subsequent reactions with ethanol solutions of Cu(OAc)₂ and benzene‐1,3,5‐tricarboxylic acid (designated as H₃btc) alternately. The resulting Fe₃O₄@[Cu₃(btc)₂] possess strong magnetic responsiveness. We applied the novel nanocomposites in the enrichment of low‐concentration standard peptides, peptides in MYO and BSA tryptic digests and in human urine in combination with MALDI‐TOF MS analysis for the first time. In addition, the Cu₃(btc)₂ MOF shells exhibit strong affinity to peptides, thus providing a rapid and convenient approach to the concentration of low‐abundance peptides. Notably, peptides at an extremely low concentration of 10 pM could be detected by MALDI‐TOF MS after enrichment with the magnetic MOF composites. In brief, the facile synthesis and efficient enrichment process of the Fe₃O₄@[Cu₃(btc)₂] microspheres make them promising candidates for the isolation of peptides in even complex biological environments.