Hydrophilic polydopamine-derived mesoporous channels for loading Ti(IV) ions for salivary phosphoproteome research

Salivary phosphoproteome holds great promise in clinic diagnosis. For profiling of salivary phosphoproteome, it is essential to develop efficient enrichment methods prior to mass spectrum (MS). Among developed enrichment strategies, immobilized metal ions affinity chromatography (IMAC) has exhibited outstanding performance. In this work, we report a coherent approach where polydopamine (PDA) is first utilized to form mesoporous structure through soft templating method, then chelated with Ti 4+ to construct hydrophilic polydopamine-derived magnetic mesoporous nanocomposite (denoted Fe 3 O 4 @mPDA@Ti 4+ ). In virtue of the merits including ordered mesoporous channels, appropriate superparamagnetism , and abundant Ti 4+ , the enrichment strategy based on Fe 3 O 4 @mPDA@Ti 4+ combined with MS is employed for accurate identification of phosphopeptides in β-casein digest and human saliva. As expected, Fe 3 O 4 @mPDA@Ti 4+ revealed a great selectivity (1:200) and a low detection limit (0.1 fmol μL −1 ) toward phosphopeptides. More importantly, the further successful capture of phosphopeptides from human saliva indicated the prominent potential of this method for seeking phosphopeptide biomarkers in further analysis.