Hierarchical Dendritic Mesoporous TiO2 Nanocomposites for Highly Selective Enrichment of Endogenous Phosphopeptides

The uniform growth of metal oxides into mesoporous nanostructures with controllable orientations is challenging but of significance. Here, a polydopamine (PDA)-induced oriented growth strategy is proposed to uniformly grow metal ions into mesoporous metal oxides with controllable orientation. Two mesoporous nanostructures (3D hierarchical dendritic nanostructures and 2D nanosheets) were constructed by this strategy. It is worth emphasizing that the 3D hierarchical mesoporous nanostructures (DMSNs@TiO2) are formed by constructing single-layered porous TiO2 in dendritic mesoporous tunnels, which is different from the previously reported generation of hierarchical pores inside frameworks or accumulation of various channels. In such a pore system, small pores are connected by large pores, thereby enhancing the accessibility of pores. DMSNs@TiO2 with a large surface area and connected hierarchical pore structure exhibit highly improved phosphopeptide enrichment performance compared with commercial TiO2 and single-pored TiO2. Especially for real samples such as human saliva, DMSNs@TiO2 captured 49 endogenous phosphopeptides from 1 μL of saliva, demonstrating their broad prospects in phosphopeptidomics analysis.