Electrochemical Detection of a Breast Cancer Biomarker with an Amine-Functionalized Nanocomposite Pt-Fe 3 O 4 -MWCNTs-NH 2 as a Signal-Amplifying Label.

We report an ultrasensitive sandwich-type electrochemical immunosensor to detect the breast cancer biomarker CA 15-3. Amine-functionalized composite of reduced graphene oxide and Fe ₃ O ₄ nanoparticles (MRGO-NH ₂ ) was used as an electrochemical sensing platform material to modify the electrodes. The nanocomposite comprising Pt and Fe ₃ O ₄ nanoparticles (NPs) anchored on multiwalled carbon nanotubes (Pt-Fe ₃ O ₄ -MWCNTs-NH ₂ ) was utilized as a pseudoenzymatic signal-amplifying label. Compared to reduced graphene oxide, the composite MRGO-NH ₂ platform material demonstrated a higher electrochemical signal. In the Pt-Fe ₃ O ₄ -MWCNTs-NH ₂ label, multiwalled carbon nanotubes provided the substratum to anchor abundant catalytic Pt and Fe ₃ O ₄ NPs. The nanocomposites were thoroughly characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. An electroanalytical study and prevalidation of the immunosensor was carried out. The immunosensor exhibited exceptional capabilities in detecting CA 15-3, offering a wider linear range of 0.0005-100 U mL ^-1 and a lower detection limit of 0.00008 U mL ^-1 . Moreover, the designed immunosensor showed good specificity, reproducibility, and acceptable stability. The sensor was successfully applied to analyze samples from breast cancer patients, yielding reliable results.