Ultrasensitive electrochemiluminescence assay of tumor cells and evaluation of H2O2 on a paper-based closed-bipolar electrode by in-situ hybridization chain reaction amplification.

In this manuscript, a disposable paper-based analytical device comprised of a closed bipolar electrode (BPE) was fabricated for the ultrasensitive electrochemiluminescence (ECL) detection of intracellular H2O2 and the number of cancer cells. In this approach, wax printing was used to fabricated reaction zone, and carbon ink-based BPE and driving electrodes were screen-printed into the paper. AuPd nanoparticles (NPs), which served as a carrier of the capture aptamer and as the catalyst for the ECL reaction of luminol and H2O2, were used to modify the BPE. Luminol/Au NPs were attached to the surface of the captured cells via hybridation chain reaction with two hairpin structure DNA labelled luminol/Au NPs. In the stimulation of phorbol myristate acetate, The coreactant H2O2 was released from the target cells. The ECL response of the luminol-H2O2 system was related to the number of cancer cells in the testing buffer, which served as a quantitative signal for the determination of cancer cells and the concentration of H2O2. In order to decrease the external voltage, K3[Fe(CN)6] was introduced in the cathode resevoir of BPE because it gained electrons at the cathode more easily than oxygen. The ECL intensity was quantitatively related to the concentration of MCF-7 in the range of 1.0 × 102-1.0 × 107 cells/mL. The detection limit was 40 cells/mL and it showed good specificity for cells with high overexpression of mucin-1 receptor, it was concluded that the developed protocol could be effectively utilized for the detection of MCF-7 cells.