Monodisperse Magnetic Composite Microspheres with Controllable Carboxyl Density for the Plasma D-Dimer Detection

D-dimer levels have been used in the diagnosis of a variety of thrombosis-related diseases. In this work, magnetic composite microspheres with a carboxyl-functionalized copolymer shell were fabricated and used to establish a chemiluminescence immunoassay system for plasma D-dimer detection. Our strategy was characterized by two remits. (1) Uniform particle size and spherical shape of the magnetic composite microspheres ensured highly repeatable results with a coefficient of variation (CV) less than 2% in D-dimer detection; (2) cross-linked copolymer shell provided controllable carboxyl density for improved sensitivity with a signal-to-noise ratio (SNR) up to 159 and lower limit of detection (LLOD) as low as 0.0010 μg mL^–1 (FEU) in D-dimer detection. Linearity range, repeatability, specificity, and thermal acceleration stability of the immunoassay system were comparable with the commercial chemiluminescence immunoassay reagent kit. Above all, the methodological comparison between the established immunoassay system and the commercial reagent kit exhibited a square R² of correlation coefficient (r) greater than 0.90, which indicated the established immunoassay system could accurately detect the D-dimer levels in the plasma samples. Therefore, our strategy will provide a useful paradigm for monodispersed magnetic composite microspheres to be used in biomarker detection of the chemiluminescence immunoassay.