Light, pH, and Temperature Triple-Responsive Magnetic Composites for Highly Efficient Phosphopeptide Enrichment.

Smart materials can dynamically and reversibly change their structures and functions in response to external stimuli. In this study, we designed a smart magnetic composite (MNP-pSPA--pNIPAm) with a triple response to ultraviolet (UV) light, pH, and temperature. Relying on the response of spiropyranyl acrylate (SPA) and -isopropylacrylamide (NIPAm) to external stimuli (light, pH, and temperature), MNP-pSPA--pNIPAm was used for the controlled capture and release of phosphopeptides. The established phosphopeptide enrichment platform exhibits high sensitivity (detection limit of 0.04 fmol), high selectivity (BSA/β-casein, 1000:1), and good reusability (6 cycles). In addition, the method was also applied to the enrichment of phosphopeptides in real samples (skim milk, human saliva, and serum), demonstrating the feasibility of this method for phosphoproteomic analysis. After enriching from human nonsmall cell lung cancer cell (A549) lysates with MNP-pSPA--pNIPAm, 2595 phosphopeptides corresponding to 2281 phosphoproteins were identified. The novel responsive enrichment probe is highly specific for phosphoproteomic analysis and provides an effective method for studying the significance of protein phosphorylation in complex biological samples.