Octyl-functionalized hybrid magnetic mesoporous microspheres for enrichment of low-concentration peptides prior to direct analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Octyl‐functionalized hybrid magnetic mesoporous (Fe₃O₄·nSiO₂·meso‐hybrid‐C8) microspheres were synthesized and applied in the isolation and pre‐concentration of low‐concentration peptides prior to direct analysis by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). Such microspheres possess high surface area (324 m²/g), hydrophobic group (C8), relatively large pore volume (0.304 cm³/g), uniform pore diameter (~3.7 nm), and magnetic responsivity, which make them a simple and efficient kind of adsorbent for the enrichment of low‐concentration peptides. For bovine serum albumin (BSA, 15 fmol μL^–1) digest, after concentration by Fe₃O₄·nSiO₂·meso‐hybrid‐C8 microspheres, the enrichment performance was evidently better than those obtained by solvent evaporation and C8‐functionalized magnetic particles, and comparable to those obtained by commercial Anchor chip target and ZipTipC18 pipette tip. Such microspheres were further applied in the enrichment of the tryptic digests of rat cerebellum proteins and endogenous peptides of crude human serum, and more peaks with higher signal‐to‐noise (S/N) ratio were obtained than before pre‐concentration. Furthermore, the pre‐concentration reproducibility of magnetic microspheres for biological samples was good, and the limit of detection (LOD) for BSA digests by MALDI‐TOF MS was decreased by at least one order of magnitude compared with that obtained without pre‐concentration. All the above‐mentioned results indicate that the synthesized Fe₃O₄·nSiO₂·meso‐hybrid‐C8 microspheres are promising for the enrichment of low‐concentration peptides from complex biosamples. Copyright © 2011 John Wiley & Sons, Ltd.