Stabilized, Superparamagnetic Functionalized Graphene/Fe₃O₄@Au Nanocomposites for a Magnetically-Controlled Solid-State Electrochemiluminescence Biosensing Application

Herein, a multifunctional nanoarchitecture has been developed by integrating the branched poly­(ethylenimine) functionalized graphene/iron oxide hybrids (BGNs/Fe₃O₄) and luminol capped gold nanoparticles (luminol-AuNPs). The luminescent luminol-AuNPs as an electrochemiluminescence marker can be assembled on the nanocarrier of BGNs/Fe₃O₄ hybrids efficiently via the Au–N chemical bonds and electrostatic adsorption. Meanwhile, the multifunctional nanoarchitecture has been proved with excellent electron transfer, good stability, high emission intensity, etc. Furthermore, we successfully developed an ultrasensitive magnetically-controlled solid-state electrochemiluminescence (ECL) platform for label-free determination of HeLa cells using this multifunctional nanocomposite. Excellent performance of the magnetically-controlled ECL biosensing platform has been achieved including a high sensitivity for HeLa cells with a linear range from 20 to 1 × 10⁴ cells/mL, good stability, and reproducibility