Glycocyamine functionalized magnetic layered double hydroxides with multiple affinity sites for trace phosphopeptides...

Efficient enrichment and identification of phosphopeptides are of great significance in biological applications. Glycocyamine functionalized magnetic layered double hydroxides (Fe₃O₄@LDH@NH₂-GAA) was fabricated through an easy process. The magnetic composite possessed high surface area, good biocompatibility, and fast magnetic response. Fe₃O₄@LDH@NH₂-GAA, combining not only metal ions (Cu²⁺ and Ga³⁺) in LDH but also functional guanidyl groups in glycocyamine, offered multiple affinity sites for phosphopeptides enrichment. With these favorable characters, it exhibited high selectivity (β-casein: bovine serum albumin = 1:5000), low detection limit (0.1 fmol), satisfactory enrichment recovery (94.5%), high adsorption capacity (82.4 mg g^-1), and good repetitiveness. Moreover, the efficient enrichment of phosphopeptides by Fe₃O₄@LDH@NH₂-GAA from nonfat milk, human saliva, serum, and A549 cell lysates further confirmed its great potential for trace biological detection and proteomic analysis.