Electrochemical sensor utilizing ferrocene loaded porous polyelectrolyte nanoparticles as label for the detection of protein biomarker IL-6

A facile method for the preparation of ferrocene (FC) loaded porous polyelectrolyte nanoparticles (FC-PPN) using CaCO3 as template was reported. Polyelectrolyte, ferrocene and CaCO3 nanoparticles were dispersed in ethanol/water solution. After the evaporation of solution under stirring, the FC-PPN was prepared with the polyelectrolyte layer adsorbed onto CaCO3 surface during the solution evaporation process, and FC encapsulated within the polyelectrolyte framework. The resulted FC-PPN showed high FC loading and good stability. Sensitive electrochemical immunosensor for the detection of oral cancer biomarker interleukin-6 (IL-6) using this FC-PPN as label was prepared. Using the redox current of FC as signal, the immunosensor displays high sensitivity, wide linear range (0.002–20 ng/mL), low detection limit (1 pg/mL) and good reproducibility. In addition, this porous nanoparticle preparation method could be extended to the incorporation of different interesting materials onto nanoparticles and find wide applications in various areas, such as bioassay, drug delivery and catalysis.