Immunosensing of breast cancer prognostic marker in adenocarcinoma cell lysates and unprocessed human plasma samples using gold nanostructure coated on organic substrate.

Early stage diagnosis of cancer by monitoring the cancer biomarkers in human biological fluids is the excellent tool and the first step toward adopting efficient therapy, hindering metastasis and reducing mortality rate. An ultrasensitive electrochemical immunosensor for quantitation of tumor suppressor protein Carcinoma Antigen 15-3 (CA 15-3) based on ternary signal amplification strategy was fabricated. In this work, the antibody (horseradish peroxidase (HRP)-Labeled anti CA 15-3) was immobilized onto a green and biocompatible nanocomposite containing gold nano-shrub (Au NSs) electrochemically assembled onto thiolated graphene quantum dots (GQDs/CysA (Cysteamine)). Therefore, a novel multilayer film based on GQDs, CysA, and Au NSs was exploited to develop a highly sensitive immunosensor for detection of CA 15.3. Fully electrochemical methodology was used to prepare a new transducer on a gold surface which provided a high surface area to immobilize a high amount of the anti-CA 15.3. Under optimized condition the calibration curve for CA 15.3 concentration was linear in the range of 0.3-1 U/mL and 2-250 U/mL with detection limit of 0.011 U/mL. The method was applied to the assay of CA 15.3 in malignant cell line lysates of human breast adenocarcinoma cell line-MCF-7.