Facile synthesis of a two-dimensional magnetic nickel-titanium polyphthalocyanine and its study in phosphopeptide enrichment.

In this study, we synthesized a two-dimensional magnetic nickel-titanium polyphthalocyanine with metal ions covalently incorporated into its framework. The composite was constructed using nickel-titanium polyphthalocyanine as the matrix, with magnetite (Fe3O4) embedded into the two-dimensional structure. This design addresses the metal leaching problem associated with conventional immobilized metal affinity chromatography (IMAC) materials, which often leads to false negatives in mass spectrometry (MS) analysis. The composite exhibited excellent hydrophilicity, good thermal stability, and abundant affinity sites. The results demonstrated high selectivity (1:1:5000), sensitivity (0.01 fmol), satisfactory recovery (89.9%), and good recyclability (at least 10 cycles) toward phosphopeptides. This approach allowed for the enrichment of 771 phosphopeptides from A549 cell lysate. The design and application of this composite provide new value for advancing phosphopeptide enrichment.