Electrochemical detection of cancer cells in human blood using folic acid and glutamic acid-functionalized graphene quantum dot-palladium@gold as redox probe with excellent electrocatalytic activity and target recognition

Determination of circulating cancer cells in human blood is potential to be convenient diagnosis of different cancers. The study reports one strategy for synthesis of folic acid and glutamic acid-functionalized graphene quantum dot-palladium@gold (FA/Glu-GQD-Pd@Au). Firstly, FA/Glu-GQD was prepared by thermolysis of the mixture of citric acid, glutamic acid and folic acid. Then, it was used as the stabilizer and reducer for synthesis of FA/Glu-GQD-Pd@Au. The resulting hybrid was employed as one redox probe for construction of electrochemical sensing platform for cancer cells. The study reveals that the FA/Glu-GQD-Pd@Au offers one core@shell nanostructure. Pd nanocube as the core was covered by gold nanocrystal as the shell. For the detection, Pd@Au gives high electrocatalytic activity due to its unique structure as well as combination with FA/Glu-GQD. FA/Glu-GQD strongly binds with cancer cells to produce target recognition. FA/Glu-GQD occurs reversible redox reactions on the electrode surface and produces electrochemical signal for binding cancer cells. Pd@Au in situ catalyzes redox of FA/Glu-GQD and achieves to significant signal amplification. The sensor based on FA/Glu-GQD-Pd@Au exhibits ultrahigh sensitivity for detection of cancer cells. The differential pulse voltammetric peak current linearly reduces with the increase of cancer cells in the range of 3-1 x 10(5) HepG2 cells mL(-1) with the detection limit of 2 cells mL(-1) (S/N = 3). The proposed analytical method has been successfully applied in electrochemical detection of circulating cancer cells in human blood.