Sudoku-like Lab-on-Paper Cyto-Device with Dual Enhancement of Electrochemiluminescence Intermediates Strategy.

This paper describes the design and construction of a sudoku-like lab-on-paper platform, in which dual enhancement of reaction intermediates strategy was incorporated for multiplexed competitive electrochemiluminescence (ECL) cyto-assay. Benefiting from the sudoku-like structure, integrated multifunctions were obtained on such an elaborately devised platform, including specific reagents storage, multiple samples immobilization, residual automatic washing, and signal collection. By utilizing semicarbazide (SE) and silver nanoparticles (AgNPs) as dual enhancers, more ECL intermediates could be obtained in the graphene quantum dots (GQDs) and peroxydisulfate system, resulting in the production of more excited-state GQDs to emit light. Moreover, the double-stranded DNA nanowire with multiple branched arms (MBdsDNA) was chosen as an efficient nanocarrier to load more GQDs and AgNPs. Via immobilizing AgNPs on the end of the plentiful branched arms, Ag-MBdsDNA were obtained and trapped on the sensing interface through the valid competitive interactions between target cells and Ag-MBdsDNA. Afterward, abundant GQDs were attached to the three-dimensional (3D) DNA skeleton of the captured Ag-MBdsDNA via π-π stacking. Due to their good self-catalytic activity of labeled AgNPs, more silver was deposited on the Ag-MBdsDNA@GQDs, giving rise to further amplification of expected signal. With four types of cancer cells as models, MCF-7, CCRF-CEM, HeLa, and K562 cells were assayed in the ranges of 1.0 × 10(2)-1.0 × 10(7), 1.5 × 10(2)-2.0 × 10(7), 2.0 × 10(2)-5.0 × 10(6), and 1.2 × 10(2)-2.0 × 10(6) cells mL(-1) with the detection limits of 38, 53, 67, and 42 cells mL(-1), respectively. Notably, this strategy supplies a simple and versatile platform for sensitive determination of multiple targeted cells, which would play a crucial role in point-of-care diagnostic fields.