▎ 摘　　要

Early diagnosis is very important for improving the quality of life and prolonging the survival time of lung cancer patients. In this work, glutamine-functionalized graphene quantum dot (Glu-GQD) was prepared by pyrolysis of the mixture of citric acid and glutamine at 180 degrees C for 3 h. The resulting Gln-GQD was reacted with HAuCl4 to produce Gln-GQD/Au hybrid. On one hand, the Gln-GQD as the reductant converted Au (3+) into Au-0, finally leading to the formation of Au nanocrystals. On the other hand, the Gln-GQD as the stabilizer was immobilized on the surface of Au nanocrystals to achieve the hybridization of Gln-GQD and Au nanoparticle. The results of scanning electron microscopy, transmission electron microscopy, X-ray diffraction and infrared spectroscopy analysis revealed that the Gln-GQD/Au offerred the crystal structure of cubic gold, in which the gold and nitrogen elements were uniformly distributed on the surface of spherical Au nanoparticles, with the average particle size of (31. 2 +/- 0. 15) nm and the rich of functional groups such as -OH, -NH and -COOH. To obtain H2-Gln-GQD/Au-Thi redox probe, one hairpin DNA2 (H2) was connected to the surface of Au nanoparticles via the Au-S bond, and then the condensation of -COOH in the Gln-GQD with -NH2 in the thionine (Thi) by EDC/NHS activation was achieved. Further, the redox probe was used to construct electrochemical sensing platform coupled with the nonenzymatic amplification strategy. In the presence of CYFRA21-1 , the H2 in the redox probe was hybridized with the hairpin DNA 1 (H1) modified on the surface of gold electrode to release one CYFRA21-1, which could be directly used in the next target DNA cycle. By the target-induced DNA self-assembly reaction, one CYFRA21-1 molecule transferred multiple redox probes to the surface of gold electrodes, resulting in a significant electrochemical signal amplification. In the detection of CYFRA21-1, the hybridization of H2 with H1 achieved the specific response to target DNA. Thi underwent reversible redox reaction on the electrode surface and produced the electrochemical signal in the response to target DNA. The Gln-GQD/Au in situ catalytzed the oxidation-reduction reaction of Thi. This would further amplify the detection signal. When the concentrations of CYFRA21-1 were in the range of 2-100000 fmol/L , the differential pulse voltammetric peak current increased linearly with the increase of CYFRA21-1 concentration. The detection limit was found to be 0.67 fmol/L (S/N = 3). The sensitivity was much better than that of reported electrochemical sensors for CYFRA21-1. This method was successfully applied to the electrochemical detection of CYFRA21-1 in human serum samples.