Functionalized Polydopamine Nanospheres with Chemiluminescence and Immunoactivity for Label-Free Copeptin Immunosensing

A multifunctionalized polydopamine (PDA) nanosphere was developed as a versatile nanoplatform for chemiluminescence (CL)-based immunosensors. PDA nanospheres were synthesized and engineered to serve as a host platform for the immobilization of gold nanoparticles (AuNPs) and CL precursors Co2+/N-(4-aminobutyl)-N-ethylisoluminol (ABEI) to obtain the Co2+-ABEI-AuNPs-PDA nanocomposites. Surface characterization and elemental analysis demonstrated that the synthesized nanocomposites possessed a spherical shape with an average diameter of 266 ± 59 nm effectively decorated with AuNPs, Co2+, and ABEI on the surface of PDA nanospheres. Remarkable CL properties were observed from the Co2+-ABEI-AuNPs-PDA nanospheres when they were reacted with H2O2. The CL intensity of the Co2+-ABEI-AuNPs-PDA nanospheres was enhanced almost 500 times compared to the ABEI-AuNPs-PDA nanospheres. Furthermore, utilizing a biomarker copeptin for acute myocardial infarction (AMI) as a model target, a label-free copeptin immunosensor based on direct incorporation of the antibody to the Co2+-ABEI-AuNPs-PDA nanocomposites via AuNPs was developed. Copeptin could be determined in the range of 1.0 × 10–12–1.0 × 10–7 g/mL with a detection limit of 3.25 × 10–13 g/mL and good selectivity. The proposed immunosensor has been successfully used to determine copeptin in real serum samples, suggesting its practicability in AMI clinical assessments. The ease of fabrication and versatility toward the direct immobilization of antibodies offered by the proposed CL-functionalized nanoplatforms open up possibilities for the design of a wide range of immunosensors.