Multifunctionalized Hydrogel Beads for Label-Free Chemiluminescence Imaging Immunoassay of Acute Myocardial Infarction Biomarkers

Hydrogel beads exhibit good biocompatibility, high stability, and monodispersity. However, hydrogel beads possessing intensive and multicolor chemiluminescence (CL) have not been reported. In this work, two kinds of multifunctionalized hydrogel beads, one consisting of chitosan (CS), Co2+, luminol, and gold nanoparticles (AuNPs) (CS-Co2+-Lu-Au), and another consisting of CS, Co2+, luminol, fluorescein, and AuNPs (CS-Co2+-Lu-FL-Au), were prepared via a facile synthesis method. The synthesized CS-Co2+-Lu-Au and CS-Co2+-Lu-FL-Au hydrogel beads exhibit high stability, simple operability, and can generate strong and uniform blue- and green-colored CL emission, respectively, when reacting with H2O2. Specific antibodies (Ab) can be assembled onto the surface of CS-Co2+-Lu-Au and CS-Co2+-Lu-FL-Au hydrogel beads directly via CS and surface-coated AuNPs as binding sites to obtain multifunctionalized hydrogel beads with both good CL activity and immunoactivity. Then, simple, fast, and versatile label-free CL imaging immunoassays were fabricated for the determination of two important acute myocardial infarction (AMI) biomarkers, including cardiac troponins I (cTnI) and heart-type fatty acid-binding protein (h-FABP), using a smartphone as a portable detector. The proposed CL imaging immunoassays using CS-Co2+-Lu-Au-Ab and CS-Co2+-Lu-FL-Au-Ab as sensing platforms can be carried out without complex instruments or time-consuming centrifugation or magnetic separation, greatly simplifying the assay procedures. The linear ranges for cTnI and h-FABP detection were 1.0 x 10(-11) to 1.0 x 10(-5) g/mL with detection limits as low as 1.57 and 1.61 pg/mL, respectively. Furthermore, the fabricated CL imaging immunoassays were successfully applied to determine cTnI and h-FABP in healthy human and patient serum samples, demonstrating their practicability in AMI diagnosis. The easy synthesis and versatility of the as-prepared CL hydrogel beads for the direct immobilization of Ab provide universal platforms for a wide range of CL immunoassays.