Ultrasensitive Label-Free Electrochemical Immunosensor for Carbohydrate Antigen-125 (CA125) Employing Cu(II)-Polyethyleneimine (PEI)/Silica Nanoparticle@Overoxidized Polypyrrole (OPPy)/Multi-Walled Carbon Nanotubes (MWNTs) Hybrid Nanomaterial. - Chang, Zheng; Zhao, Qiqi; Yao, Binghua; Han, Lei (Analytical Letters, 2025)