Bifunctional pd-decorated polysulfide nanoparticle of Co9S8 supported on graphene oxide: A new and efficient label-free immunosensor for amyloid β-protein detection

In this work, bifunctional Pd-decorated Co9S8 polysulfide nanoparticles supported on graphene oxide (G/Co9S8-Pd) were used to build a label-free immunosensor for amyloid beta-protein (A beta) detection. Grafting Co9S8 onto a conductive graphene support can prevent the aggregation of Co9S8 and improve the conductivity of the nano-composites of G/Co9S8. A large number of Pd nanoparticles (NPs) were loaded on the G/Co9S8 surfaces providing more sites to attach A beta antibodies by a Pd-N chemical bond. As expected, the novel G/Co9S8-Pd nanocomposites with a high specific surface area showed excellent electrocatalytic activity for H2O2 reduction and good conductivity. The efficient catalytic activity originated from the synergy between the integrated Co9S8, Pd NPs and GO. Additionally, G/Co9S8-Pd was applied as a matrix and signal indicator in our immunosensor and obtained a high sensitivity for A beta detection. The developed immunosensor demonstrated a wide linear range (0.1 pg/mL to 50 ng/mL) and had a low detection limit (41.4 fg/mL). Based on the above, the immunosensor exhibits a remarkable analytical ability and shows potential for a wide range of applications in the field of clinical medical examination and treatment.