Development of CoFe2O4/Ketjen Black enhanced ultrasensitive electrochemical immunosensor for PSA detection in reference and real samples

Abstract

In this study, the development of an ultrasensitive electrochemical immunosensor based on a novel nano-composite involving cobalt ferrite oxide (CoFe2O4) LDH (layered double hydroxide) and Ketjen Black (KB) to obtain a highly electroconductive surface with a high surface area is demonstrated. The CoFe2O4 LDH/Ketjen Black composite significantly improved electrocatalytic activity, electron transfer efficiency, and surface area on the glassy carbon electrodes (GCE) and enabled efficient immobilization of antibodies. Electrochemical immunosensor characterization confirmed the high electroconductivity and electrocatalytic properties of the modified electrodes. Under optimized conditions, the immunosensor demonstrated a broad linear detection range between 100 ag/mL to 100 ng/mL and a very low limit of detection (LOD) of 37.71 ag/mL (S/N = 3) and limit of quantification (LOQ) of 43.24 ag/mL (S/N = 3) in reference samples. The proposed method showed better performance compared to conventional Enzyme-Linked Immunosorbent Assay (ELISA) and existing electrochemical methods, which is one of the most sensitive electrochemical immunosensor systems reported to date. Selectivity studies revealed minimal interference from analogs such as Human Serum Albumin (HSA), Human Epididymis 4 Protein (HE4), Human Epidermal Growth Factor Receptor (HER1), Cancer Antigen 125 (CA125), and Interleukin 6 (IL-6). The performance of the immunosensor in real samples was evaluated in synthetic serum and synthetic saliva samples that yielded recoveries of 101.1-104.3 % (n = 5), highlighting robustness in complex biological matrices. Overall, the nanocomposite-modified biosensor provided reliable detection of PSA with stability over three weeks, offering potential for early prostate cancer screening and broader clinical applications.