Ultrasensitive immunoassay of tumor protein CA 15.3 in MCF-7 breast cancer cell lysates and unprocessed human plasma using gold nanoparticles doped on the structure of mesoporous silica.

Breast cancer is the most common threat in women worldwide. Increasing death rate of diagnosed cases is the main leading cause of designing specific immunoassay for tumor marker in breast cancer. Cancer antigen 15-3 (CA 15-3) is a tumor protein for many types of cancer, most notably breast cancer. Herein, we report a sandwich-type electrochemical immunosensor based on signal amplification strategy of multiple nanocomposites to detection of CA 15-3 biomarker. The proposed immunosensor fabricated by reduced graphene oxide (rGO), poly-dopamine (PDA) and amino functionalized mesoporous silica (MCM-41-NH2) doped by gold nanoparticles composite on the glassy carbon electrode with a large surface area which was prepared a new platform to immobilization of primary antibodies and provide excellent conductivity. To further amplify the electrochemical signal, the trace tag on the foundation of gold nanoparticles (AuNPs) is coated with MCM-41-NH2 nanocomposite through thionine linking, which provides more amino groups to capture more horseradish peroxidase-labeled antibodies (HPR-Ab2) and enhances the conductivity. Under optimal conditions, the developed immunosensor exhibits excellent analytical performance for the determination of CA 15-3 with a wide linear range from 0.002 to 125 U/mL and a low limit of quantification of 0.002 U/mL. Furthermore, satisfactory results are obtained for the determination of CA 15-3 in human plasma samples, indicating the potential of the immunoassay to be applied in clinical analysis.