Multi-point ATP sensing for rapid precise fish freshness check

A microfluidic device for adenosine triphosphate (ATP) was checking of fish freshness. Sample solutions containing ATP and the other solution containing an enzyme substrate were handled in the form of plugs formed in a network of flow channels. To simplify the structure and procedure for mixing solutions, a wider portion was formed in a flow channel to merge the plugs. A row of plugs were ejected from each of three branched flow channels, merged at the wider portion, and transported to an ATP biosensor located in the lower stream. ATP was detected using two enzymatic reactions involving glycerol kinase (GK) and glycerol-3-phosphate oxidase (G3PO). The current observed with solutions of three different ATP concentrations showed different values, demonstrating that the device can be used for multi-point sensing. Furthermore, the detection of ATP in extracts from tuna was carried out and a distinct increase in current was observed as in the case of standard solutions.