Mkit: A mobile nucleic acid assay based on a chitosan-modified minimalistic microfluidic chip (CM-chip) and smartphone.

Mobile sensing enabled by MS technology, which integrates microfluidic and smartphone components, has seen many applications in recent years. In this direction, we developed an MS platform (an integrated kit) for nucleic acid assay, which included a chitosan-modified minimalistic microfluidic chip (CM-chip), a smartphone-based fluorescence detector (SF-detector), an APP for imaging and analysis, reagents, and accessories. Once the lysed sample was loaded into the CM-chip modified by 1% concentration and 200-260 kDa molecular weight of chitosan, the following assay can be completed in approximately 1 h. The Mkit can detect 3 × 10° copies μL of plasmid DNA and its polymerase chain reaction (PCR) efficiency was 96.8%. The CM-chip equipped for the Mkit can enrich nucleic acid from the pH = 5 of lysis buffer, instead of using conventional adsorption mediums such as the magnetic beads and silica gel membranes, which could result in unexpected impurity residuals and tedious cleaning operations. In addition, the performance of the Mkit equipped with the pristine chip was demonstrated to perform poorer than that coupled with the CM-chip in which the enriched nucleic acid can be all used for "in-situ PCR". The universality, selectivity, and user-friendliness of the Mkit were also validated. We finally demonstrated the feasibility of the Mkit for testing artificially prepared infected samples. H5N6 and IAV-infected saliva samples provided the limits of detection of 5 × 10 copies mL and 3.24 × 10 copies mL per chamber, respectively. The streamlined assay and compact device should enable the great potential of the Mkit in research and potential diagnostic uses.