Magnetic γ-Fe2O3@REVO4 (RE = Sm, Dy, Ho) affinity microspheres for selective capture, fast separation and easy identification of phosphopeptides

Abstract

The multifunctional microspheres consisting of the magnetic γ-Fe₂O₃ core and the affinity REVO₄ (RE = Sm, Dy, Ho) shell have been synthesized via the homogenous precipitation–calcination–ion exchange three-step synthetic route. Their morphologies, structures, surface properties, and magnetisms were characterized, respectively. SEM and TEM images indicate that they all have an average size of about 400 nm and very rough surfaces. The TEM images further reveal that the γ-Fe₂O₃@REVO₄ microspheres are all core–shell structures and the REVO₄ shells are about 55–60 nm in thickness. The XRD pattern analyses show that the magnetic γ-Fe₂O₃ cores belong to cubic structure and the REVO₄ (RE = Sm, Dy, Ho) shells are composed of their corresponding tetragonal major phases. HRTEM images, FTIR spectra and EDS further demonstrate the formations of tetragonal REVO₄ shells based on checkup of the corresponding lattice fringes, characteristic IR absorption peaks and element signals. Their potentials for selective capture, rapid separation, and convenient mass spectra (MS) labeling of the phosphopeptides from complex proteolytic digests are explored and evaluated for the first time. The experimental results show that the magnetic γ-Fe₂O₃@REVO₄ core–shell structured microspheres have high selective affinity for the phosphopeptides. The trapped phosphopeptides can be rapidly isolated by an external magnetic field, and can be easily identified by characteristic MS signals from 80 Da mass losses in the mass spectra (MS). Additionally, the γ-Fe₂O₃@REVO₄ affinity materials can be reused after recovery.