Electrochemical Biosensor Based on Nitrogen and Sulfur Co-Doped Graphene Quantum Dot Decorated Gold Nanostars for Breast Cancer Diagnosis—From Academic Research to Clinical Translation

In this study, we leveraged the synergistic effect of nitrogen and sulfur co-doped graphene quantum dots (NSGQDs) and three-dimensional gold nanostars (AuNS) in the hybrid material of AuNS@NSGQDs as a superior material for constructing a label-free electrochemical biosensor. Consequently, the as-prepared AuNS@NSGQDs nanocomposite was simply drop-casting onto the screen-printed platinum electrode (SE), followed by conjugating with phytohemagglutinin-L (PHAL) to form the SE=AuNS@NSGQDs/PHAL sensor probe. This SE=AuNS@NSGQDs/PHAL sensor probe was then employed for the detection of MCF-7 breast cancer cells, illustrating the remarkable sensitivity and selectivity through linear sweep voltammetry (LSV) and electrochemical impedance spectrometry (EIS). Intriguingly, the sensing system exhibits enhanced electrochemical performance with excellent conductivity owing to AuNS@NSGQDs, while PHAL serves as an effective anchor for the MCF-7 breast cancer cells, which provides outstanding background for electrochemically ultrasensitive and selective detection. In fact, the developed novel AuNS@NSGQDs/PHAL biosensor depicts an outstanding performance in detecting MCF-7 with an impressively low limit of detection (LOD) of 3 cancer cells mL⁻¹ in a wide linear range of 10 - 10⁵ cells mL^-1, showcasing a great potential in clinical and cancer diagnostic applications. Furthermore, the SE=AuNS@NSGQDs/PHAL reveals a remarkable selectivity over different co-existing cell lines, highlighting its specificity for MCF-7 cells. The sensor also displayed remarkable stability and reproducibility, maintaining performance over a storage period of 100 days and sustaining functionality over 30 consecutive cycles of reuse. The low toxicity of AuNS@NSGQDs nanocomposite was observed at high concentrations, indicating a trivial effect on the MCF-7 cell line, underscoring its safety for biosensor applications. This achievement paves the way for the development of an electrochemical sensing probe as a robust platform for simple, rapid detection of MCF-7 with high accuracy and specialty, facilitating early diagnosis and therapy of diseases, particularly in the context of breast cancer.