A ratiometric electrochemiluminescence detection for cancer cells using g-C3N4 nanosheets and Ag-PAMAM-luminol nanocomposites

In this work, a dual-signaling electrochemiluminescence (ECL) ratiometric sensing approach for the detection of HL-60 cancer cells was reported for the first time. G-C3N4 nanosheets and Ag-PAMAMluminol nanocomposits (Ag-PAMAM-Iuminol NCs) were prepared and served as reductive-oxidative and oxidative-reductive ECL emitters respectively. DNA probe functionalized Ag-PAMAM-Iuminol NCs would hybridize with aptamers modified onto magnetic beads. In the presence of HL-60 cells, the aptamer would conjugate with the target cell and release Ag-PAMAM-Iuminol NCs. After magnetic separation, released Ag-PAIVIAM-Iuminol NCs would hybridize with capture DNA on g-C3N4 nanosheets. ECL from g-C3N4 nanosheets coated on ITO electrode at -1.25 V (vs SCE) could be quenched by AgPAMAM-Iuminol NCs due to the resonance energy transfer (RET) from g-C3N4 nanosheets to Ag NPs. Meanwhile, Ag-PAMAM-Iuminol brought the ECL signal of luminol at +0.45 V (vs SCE). Thus, the concentration of HL-60 cancer cells could be quantified by both the quenching of ECL from g-C3N4 nanosheets and the enhancement of ECL from luminol. By measuring the ratio of ECL intensities at two excitation potentials, this approach could achieve sensitive and reliable detection for cancer cells in a wide range from 200 cells/mL to 9000 cells/mL with the detection limit of 150 cells (S/N=3). (C) 2015 Elsevier B.V. All rights reserved.