In Situ MXene-Controlled Synthesis of Polycrystalline TiO₂ for Highly Efficient Enrichment of Phosphopeptides

Phosphopeptide enrichment methods based on commercial TiO 2 suffer from difficulties in regulating intermolecular interactions, resulting in low coverage rate and the loss of information on multiphosphorylation sites, thereby limiting comprehensive phosphoproteomic analysis. In this work, MXene Ti 3 C 2 T x was incorporated into the design of enrichment materials, with its surface structure functionalized and regulated to address the low elution efficiency of TiO 2 for multiphosphorylated peptides. Upon oxidation treatment, the Ti 3 C 2 T x material formed numerous uniformly distributed TiO 2 nanoparticles on the surface of Ti 3 C 2 T x -O, providing abundant affinity sites (Ti–O) for selective phosphopeptide enrichment. The polycrystalline structure and rich oxygen vacancies of the material effectively regulated its binding affinity with phosphate groups, achieving simultaneous high-efficiency enrichment of both monophosphorylated and multiphosphorylated peptides. Its performance was significantly superior to that of commercial TiO 2 and IMAC materials. This study presents great promise for the practical application of comprehensive phosphoproteomic analysis in the future and broadens the application of MXene in the biological field.