Tunable Polymer-Brush Interfaces on Magnetic Beads Enable Enhanced Chemiluminescence Immunoassay

). By systematically varying the initiator loading and monomer feed, a clear structure-property relationship is established between brush architecture, surface carboxyl density, antibody immobilization, and interfacial sensing performance. The optimized beads achieve a 23-fold enhancement in chemiluminescence intensity and increase the signal-to-background ratio from 79 to 575 for creatine kinase MB (CK-MB) detection, with a limit of detection of 0.11 ng/mL. The analytical performance is rigorously evaluated, and the method is validated using 50 clinical plasma samples, demonstrating the robustness of the engineered biointerface for practical diagnostic applications.