Electrochemical DNA sensor based on three-dimensional folding paper device for specific and sensitive point-of-care testing

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The development of low-cost, accurate and sensitive diagnostic tests is crucial to many clinical, laboratory, and field applications, including forensics and medical diagnostics. Cellulose fiber-based paper is an inexpensive, biodegradable, and renewable resource, the use of which as a diagnostic device confers several advantages compared to traditional substrate. In this work, wax printer was used to produce collapsible microfluidic paper-based analytical devices (μPADs), which were combined with screen-printed electrodes (SPEs) to create simple, low-cost, disposal devices in bulk. Herein, an electrochemical DNA sensor was introduced for the first time into a folding paper based on the AuNPs/graphene modified screen-printed working paper electrode (SPWPE). Thionine (TH) bound to double stranded DNA(dsDNA) as signal tags (TH/D1), together with Complementary ssDNA (S3) immobilized on Nanoporous gold (NPG) forming a S3-TH/D1-NPG bioconjugates. Owing to the chain structure of dsDNA and large specific surface area of NPG, the bioconjugates proved to be an excellent amplification label. Under optimal conditions, the folding μPADs DNA sensor showed high sensitivity, good precision, acceptable stability, reproducibility and excellent performance in human serum assay. In addition, the simple, low-cost, sensitive device can be easily applied for point-of-care testing (POCT), public health and environmental monitoring in remote regions, developing or developed countries.