Streptavidin-functionalized-polyethyleneimine/chitosan/HfO₂-Pr₆O₁₁ nanocomposite using label-free electrochemical immunosensor for detecting the hunger hormone ghrelin

We report the hydrothermal synthesis of the bimetal oxide hafnium oxide-praseodymium oxide nanoflakes (HfO₂-Pr₆O₁₁) incorporated with chitosan (CS) and polyethyleneimine (PEI) to produce a PEI/CS/HfO₂-Pr₆O₁₁ nanocomposite. The negative charge of HfO₂-Pr₆O₁₁ and the positive charge of PEI interact electrostatically in the PEI/CS/HfO₂-Pr₆O₁₁ nanocomposite. The reported nanocomposites exhibit distinct attributes, including high electrical conductivity and surface area, more accessible active sites, and good hydrophilicity. In addition, streptavidin (Strep)-functionalized PEI/CS/HfO₂-Pr₆O₁₁ nanomaterials improved the antibody loading efficiency on the biosensing platform, and certified the protein immobilization activity. The Strep/PEI/CS/HfO₂-Pr₆O₁₁ composites were analyzed using various characterization techniques for use as a label-free electrochemical immunosensor of the hunger hormone ghrelin (GHRL). The constructed immunosensor demonstrated linearity over a wide range (0.01 pg/mL–50 ng/mL) and a LOD of 0.006 pg/mL, along with good specificity, precision (reproducibility and repeatability), and cyclic and storage stability for GHRL detection. The practicability of the immunosensor was assessed using serum samples from healthy individuals.