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 H(3)btc) alternately. The resulting Fe3O4@[Cu-3(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 Cu-3(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@[Cu-3(btc)(2)] microspheres make them promising candidates for the isolation of peptides in even complex biological environments.