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One of the most prevalent diseases where point-of-care (POC) diagnostics has focused is diabetes, which impacts hundreds of millions of people globally. Due to the severe negative outcomes including renal failure, nerve damage, and stroke, many POC sensors have been designed to streamline low-cost testing. Recently, the utility of 3D printing for rapidly fabricating housings, electrodes, and sensors for use at the POC has been exploited toward diverse applications. Particularly interesting are 3D printed carbon electrodes (3DpCEs) in POC diagnostics owing to their simplicity, affordability, and mass production capabilities for developing sensors either for direct use or through post-printing surface modifications. Herein, we report a copper modified 3DpCE as a sensitive and selective nonenzymatic biosensor for glucose. Copper deposition, paired with an optimized activation protocol, produced a sensitive and selective sensor for glucose with a larger detection range, enhanced sensitivity, and better reproducibility compared to nonactivated and alkaline immersed 3DpCEs. The sensor displayed excellent linearity between 10–1800 μ M and proved to be highly selective over common biologically relevant interferants. The 3D printed sensor successfully determined biologically relevant concentrations of glucose in human saliva which resulted in percent recoveries of 101 ± 8%, 106 ± 6%, and 98 ± 6% for 74, 402, and 652 μ M glucose, respectively.

This paper describes the design, fabrication, and validation of a paper-based diagnostic device for the rapid diagnosis of hypocalcemia in dairy cattle at the point-of-care (POC). The device incorporates a 3D printed calcium ion-selective membrane (ISM) as the sensing element for free—unbound—calcium in real bovine whole blood samples. With a linear response range of 100 mM to 97.7 μ M, the sensor covers the clinically relevant concentrations of Ca ^2+ associated with both healthy cattle as well as those suffering from hypocalcemia. The components of the Ca ^2+ ion-selective electrodes were successfully translated to a paper-based device to provide a sensing platform that is simple to use, disposable, and low-cost, and is therefore well-situated for applications at the POC. The paper-based calcium sensor showed a Nernstian response between 10 mM and 100 μ M and required only 12 μ l of sample to perform a measurement, which can be accomplished in less than two minutes without the need for time-consuming separation steps. The performance of the paper-based Ca ^2+ sensor was validated using the commercially available epoc ^® Blood Analysis System, which provided results within 5% of the data obtained with 3D printed Ca ^2+ -ISM integrated paper-based device.