CdSe@CdS quantum dot–sensitized Au/α-Fe 2 O 3 structure for photoelectrochemical detection of circulating tumor cells

Circulating tumor cells (CTCs) are the important biomarker for cancer diagnosis and individualized treatment. However, due to the extreme rarity of CTCs (only 1–10 CTCs are found in every milliliter of peripheral blood) high sensitivity and selectivity are urgently needed for CTC detection. Here, a sandwich PEC cytosensor for the ultrasensitive detection of CTCs was developed using the photoactive material Au NP/-Fe 2 O 3 and core-shell CdSe@CdS QD sensitizer. In the proposed protocol, the CdSe@CdS QD/Au NP/α-Fe 2 O 3 -sensitized structure with cascade band-edge levels could evidently promote the photoelectric conversion efficiency due to suitable light absorption and efficient electron-hole pair recombination inhibition. Additionally, a dendritic aptamer-DNA concatemer was constructed for highly efficient capture of MCF-7 cells carrying CdSe@CdS QDs, a sensitive material. The linear range of this proposed signal-on PEC sensing method was 300 cell mL −1 to 6 × 10 5 cell mL −1 with a detection limit of 3 cell mL −1 , and it demonstrated an ultrasensitive response to CTCs. Furthermore, this PEC sensor enabled accurate detection of CTCs in serum samples. Hence, a promising strategy for CTC detection in clinical diagnosis was developed based on CdSe@CdS QD–sensitized Au NP/α-Fe 2 O 3 -based PEC cytosensor with dendritic aptamer-DNA concatemer. Graphical abstract