Layer-by-layer assembly of multilayered double hydroxides/polyoxometalate-coated magnetic nanoparticles for highly efficient phosphopeptide enrichment.

A layer-by-layer (LbL) assembly strategy was developed to prepare multilayered double hydroxide/polyoxometalate shell-coated magnetic nanoparticles. The introduction of functional shells not only offered abundant affinity sites of metal oxide and metal ions but also increased the surface area for the contact with targets. By combining the enrichment strategies of immobilized metal ion affinity chromatography and metal oxide affinity chromatography, the nanomaterial can capture phosphopeptides via a synergistic effect. The method presented a low detection limit of 0.1 fmol in combination with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) analysis. The nanomaterial showed satisfactory selectivity (1:1:5000 M ratio of α-/ß-casein/bovine serum albumin), good recovery (92.07%), high adsorption capacity (117.6 mg g-1), and ten times reusability for capturing phosphopeptides.