pH and temperature dual-responsive covalent organic framework composites for efficient enrichment of phosphoproteins

Smart-responsive materials can keenly sense changes in the external environment and respond swiftly by adjusting their physical or chemical properties. In this study, we prepared pH and temperature dual-responsive magnetic composite (Mag@COF-pNIPAm) with triazine-based covalent organic framework and N-isopropylacrylamide (NIPAm). This material facilitates the effective capture and controlled release of phosphopeptides, based on which a phosphoprotein analysis platform was established, coupled with mass spectrometry (MS). Exceptional sensitivity (detection limit of 0.04 fmol), remarkable selectivity (BSA/α-casein ratio of 5000:1), and excellent reusability (up to 7 cycles) were achieved. Furthermore, the developed adsorbent was successfully applied to enrich phosphopeptides from actual samples, such as non-fat milk, human saliva, and serum. When used for phosphoprotein analysis in human lung cancer cell (A549) lysates samples, 1323 phosphopeptides were identified (11% N-phosphopeptides and 89% O-phosphopeptides). The present study provides a perspective for the fabrication and application of smart-responsive COF materials in phosphoproteomics analysis.