Controllable Preparation of CuFeMnO^sub 4^ Nanospheres as a Novel Multifunctional Affinity Probe for Efficient Adsorption and Selective Enrichment of Low-Abundance Peptides and Phosphopeptides

A facile solvothermal method for the synthesis of multifunctional magnetic CuFeMnO4 nanospheres affinity probe (NSAP) with controllable morphology and size was developed for the first time. The CuFeMnO4 nanospheres combine the brilliant features of Cu2+, Fe3+, and Mn2+ ions, so their multifunction performances are embodied by strong coordination to carboxyl and amine groups of peptides (Cu2+ and Fe3+), special affinity to phosphate groups of phosphopeptides (Fe3+ and Mn2+), and high magnetic responsiveness in a magnetic field. Their potential as an affinity probe was evaluated for highly effective enrichment, rapid magnetic separation of low-abundance peptides (neutral condition), and effective selective capture of phosphopeptides (acid condition) from various complex biosamples. Notably, CuFeMnO4 NSAP was explored for highly selective capture and isolation of phosphopeptides from A549 cells after exposure to ZnO nanoparticles for different times. Consequently, we put forward a new nanospinel ferrite-based protocol here to analyze and identify the phosphoproteins/phosphopeptides involved in cellular signaling pathways in response to exogenous stimulation.