Ultrasensitive immunoassay of glycoprotein 125 (CA 125) in untreated human plasma samples using poly (CTAB‑chitosan) doped with silver nanoparticles.

CA 125 is a Mucin glycoprotein and its concentration in human serum correlates with a woman's risk of developing ovarian cancer and also indicates response to therapy in diagnosed patients. Accurate detection of this large, complex protein in patient biofluids is of great clinical relevance. In this work, an innovative immunoassay for quantitation of CA 125 based on signal amplification strategy was proposed. In this work, Horseradish peroxidase (HRP) labeled CA 125-antibody (anti-CA 125) was immobilized onto a green and biocompatible nanocomposite containing poly cetyl trimethyl ammonium bromide (P (CTAB) as conductive matrix, chitosan (CS) as biocompatible agent and sliver nanoparticles (Ag NPs) as signal amplification element. Therefore, a novel nanocomposite film based P (CTAB-CS) and Ag NPs was exploited to develop a highly sensitive immunosensor for detection of CA 125 protein. Importantly, Ag NPs prepared by electrodeposition method which lead to compact morphology. Fully electrochemical methodology was used to prepare a new transducer on a glassy carbon surface which provided a high surface area to immobilize a high amount of the anti-CA 125. The surface morphology of electrode was characterized by high-resolution field emission scanning electron microscope (FE-SEM) and energy dispersive spectroscopy (EDS). The immunosensor was employed for the detection of CA 125 using cyclic voltammetry (CV) and differential pulse voltammetry (DPVs) techniques. Under optimized condition the calibration curve for CA 125 concentration by SWV and DPV was linear in 0.01-400 U/mL with lower limit of quantification of 0.001 U/mL. The method was successfully applied assay of the CA 125 in unprocessed human plasma samples.