Stereolithography 3-D Printed Electrochemiluminescence Platform With Random Grade Graphite Electrodes: Detection of HO and Cholesterol Using a Smartphone

The growing demand for low-cost mini biosensing platforms combining important features, such as fast performance, rapid prototyping, portability, and easy integration in point-of-care settings, has proven their existence in the field of targeted biomolecule detection. This work encompasses a novel, simple, and ultrafast fabrication of a stereolithographic 3-D printed electrochemiluminescence (GP-SE-ECL) biosensor with a graphite pencil-based single electrode (SE) to detect H2O2 and cholesterol. Graphite pencil electrodes were extensively used as a replacement for screen-printing, laser-induced graphene-based electrodes due to their user-friendliness, ease of availability, excellent electrochemical properties, and cost-efficiency. Different graded graphite electrodes (F, H, HB, 3B, 6B, and 8B) were used to fabricate SE electrochemiluminescence (ECL) devices. Since the conductivity values and surface area for different graded pencils vary, the impact of conductivity and surface area of the electrodes on the effectiveness of the ECL device was confirmed with optimized parameters by sensing H2O2. The lab-made, portable 3-D printed dark room platform integrated with a smartphone was used to capture the ECL signals. The smartphone android application was developed which can not only capture the ECL images, but also calculates the intensities values for the region of interest. Finally, the performance of the fabricated GP-SE-ECL biosensor was corroborated for cholesterol sensing to obtain a linear range (LR) from 50 to $1000 ~\mu \text{M}$ and a detection limit of $15.71 ~\mu \text{M}$ . Based on the experimental data, it was confirmed that the fabricated device with random grade pencil possesses strong acceptability in the field of biomolecule detection.