Internet of things-enabled photomultiplier tube- and smartphone-based electrochemiluminescence platform to detect choline and dopamine using 3D-printed closed bipolar electrodes.

There is a growing demand to realize low-cost miniaturized point-of-care testing diagnostic devices capable of performing many analytical assays. To fabricate such devices, three-dimensional printing (3DP)-based fabrication techniques provide a turnkey approach with marked precision and accuracy. Here, a 3DP fabrication technique was successfully utilized to fabricate closed bipolar electrode-based electrochemiluminescence (ECL) devices using conductive graphene filament. Furthermore, using these ECL devices, Ru(bpy) 3 2+ /TPrA- and luminol/H 2 O 2 -based electrochemistry was leveraged to sense dopamine and choline respectively. For ECL signal capture, two distinct approaches were used, first a smartphone-based miniaturized platform and the second with a photomultiplier tube embedded with the internet of things technology. Choline sensing led to a linear range 5-700 μM and 30-700 μM with a limit of detection (LOD) of 1.25 μM (R 2  = 0.98, N = 3) and 3.27 μM (R 2  = 0.97, N = 3). Furthermore, dopamine sensing was achieved in a linear range 0.5-100 μM with an LOD = 2 μM (R 2  = 0.99, N = 3) and LOD = 0.33 μM (R 2  = 0.98, N = 3). Overall, the fabricated devices have the potential to be utilized effectively in real-time applications such as point-of-care testing.