Probing the antigen-antibody interaction towards ultrasensitive recognition of cancer biomarker in adenocarcinoma cell lysates using layer-by-layer assembled silver nano-cubics with porous structure on cysteamine caped GQDs

The incidence of breast cancer has been increasing over the years. To control and monitor this disease several tumor biomarkers have been proposed for early diagnosis, patient follow-up and/or treatment guidance. The only serum breast cancer biomarker in current use is the cancer antigen 15-3 (CA 15-3). Highly sensitive and label-free detection of the biomarker carbohydrate antigen 15-3 (CA 15-3) remains a challenge in the diagnosis of breast cancer. Here, a novel electrochemical immunosensor capable of sensitive and label-free detection of CA 15-3 is reported. This unique immunosensor, equipped with a highly conductive nanocomposite (i.e., thiolated graphene quantum dots modified silver nanocubics (Ag NCs)-modified electrode, exhibited significantly increased electron transfer and high sensitivity towards CA 15-3. This novel immunosensor, with a limit of detection 0.019 U/mL, worked well over two linear range of 0.095-0.5 and 0.25-1 U/mL. Unlike conventional immunosensors, which usually involve complicated label processing and time consuming separations, the use of highly conductive graphene avoids the need for labels and is simple in nature. The strategy developed for this immunosensor provides a promising approach for clinical research and diagnostic applications.