Electrosynthesis of Silver Particles–Polypyrrole on Screen-Printed Carbon Electrodes, with a View to Their Modification with Ki-67 Antibodies

The development of reliable electrochemical interfaces for biosensor applications requires materials that combine high conductivity, large effective surface area, and suitable platforms for biomolecule immobilization. In this work, a hybrid electrochemical platform based on screen-printed carbon electrodes (SPCEs) modified with electropolymerized polypyrrole (PPy) and electrodeposited silver particles (AgPs) is presented for the subsequent immobilization of Ki-67 antibodies. PPy films were synthesized under optimized electrochemical conditions, producing homogeneous, porous, and electrochemically stable coatings that significantly enhanced the doping/undoping processes from 0.3280 C/0.3284 C to 0.3281 C/0.3284 C for SPCE and SPCE-PPy, respectively. Subsequently, silver particles were deposited onto the PPy matrix, resulting in a well-dispersed and uniform distribution of AgPs, promoted by the interaction between Ag0 and the nitrogen groups in the polymer backbone. The synergistic combination of PPy and AgPs resulted in improved charge-transfer properties and enhanced electrochemical reversibility, thereby decreasing the peak-to-peak separation of the ferricyanide/ferrocyanide redox couple used as a probe by 40%. Immobilization of Ki-67 antibodies was achieved via direct interaction with AgPs, resulting in a marked passivation effect, as evidenced by the suppression of redox probe signals, confirming successful biofunctionalization. The proposed SPCE-PPy-AgP architecture provides a robust, reproducible, and versatile platform for antibody immobilization, as demonstrated by oxidation and reduction peaks with relative standard deviations (RSDs) of 3.18% and 4.43%, respectively, highlighting its potential for developing label-free electrochemical immunosensors for clinically relevant proliferation biomarkers.