Highly sensitive electrochemiluminescence biosensors for cholesterol detection based on mesoporous magnetic core-shell microspheres

A sensitive electrochemiluminescence (ECL) biosensor for cholesterol detection based on multifunctional core-shell structured microspheres (Fe3O4@SiO2-Au@mpSiO(2)) is reported. This microsphere consisted of a core of silica-coated magnetite nanoparticle, an active transition layer of gold nanoparticles and a mesoporous silica shell. Scanning electron microscopy was employed to observe the morphology of the nanomaterials and transmission electron microscopy was used to further confirm the subtle structure of Fe3O4@SiO2-Au@mpSiO(2). The microspheres possessed a large surface area that increased enzyme loading, and an active transition layer gold nanoparticles enhanced the ECL signal. They were used to immobilize cholesterol oxidase for cholesterol detection with a high sensitivity, low detection limit and wide linear range. The linear range was from 0.83 to 2.62 mM with a detection limit of 0.28 A mu M (S/N = 3). Moreover, the reproducibility, stability and selectivity of the biosensor were established.