Enrichment of peptides in serum by C8-functionalized magnetic nanoparticles for direct matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis

Human serum contains a complex array of proteolytically derived peptides (serum peptidome), which contain biomarkers of preclinical screening and disease diagnosis. Recently, commercial C8-functionalized magnetic beads (1–10 μm) were widely applied to the separation and enrichment of peptides in human serum, prior to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF-MS) analysis. In this work, laboratory-prepared C8-functionalized magnetic nanoparticles (about 50 nm) were prepared and applied to the fast separation and the enrichment of peptides from serum. At first, the C8-magnetic nanoparticles were synthesized by modifying amine-functionalized magnetic nanoparticles with chlorodimethyloctylsilane. These synthesized C8-amine-functionalized magnetic particles have excellent magnetic responsibility, high dispersibility and large surface area. Finally, the C8-magnetic nanoparticles were successfully applied to fast and efficient enrichment of low-abundance peptides from protein tryptic digestion and human serum followed by MALDI–TOF-MS analysis.