Magnetic MXene/PAMAM Composites with Flexible Dimensional Regulation for Highly Effective Enrichment of Phosphopeptides

Highly specific enrichment of phosphopeptide is the prerequisite for in-depth phosphoproteome research and remains a long-standing challenge. In this work, MXenes, a new family of two-dimensional materials which have large specific surface area, flexible functionalization, and unique topological structure, have been applied to construct a novel phosphopeptide enrichment platform with great convenience by combining dimensional regulation with functional modification to prepared multidimensional polyamidoamine (PAMAM) dendrimer functionalized magnetic MXene composites (denoted as Ti3C2Tx@PAMAM@Fe3O4). The different dimensions of Ti3C2Tx@PAMAM@Fe3O4 composites exhibited dimension-dependent enrichment performance in both standard proteins and biological samples ascribed to their different surface properties and amount of affinity sites, indicating the effectiveness of dimension in regulating the enrichment ability. Owing to their superior properties, the two-dimensional Ti3C2Tx@ PAMAM@Fe3O4 composites showed better enrichment performance with high sensitivity (1 fmol mu L-1), excellent selectivity (beta-casein:BSA = 1:800, molar ratio), good reusability (five times), large enrichment capacity (200 mg g(-1)), and great practicability in identifying low-abundance phosphopeptides from nonfat milk, human serum, human saliva, and rat brain lysate. This work held great promise for future practical applications in comprehensive phosphoproteomics analysis and extended the application of MXene in the biological field.