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• A smartphone-interfaced flow injection sensing system was developed. • An electrode was modified with Pd-PANI/Carbon microspheres@carbon nanotubes. • Sensitive determination of glucose was achieved in real human serum samples. Integrating a flow injection system with an electrochemical sensor controlled by a smartphone enables rapid, precise real-time monitoring and reduces analyte consumption, contamination and costs. An enzyme-free electrochemical sensor is presented for the monitoring of glucose, an important indicator of diabetes. The sensor integrates a smartphone and a flow injection amperometric system. The flow cell is fabricated from acrylic plastic and includes an electrochemical three-electrode cell that comprises a working electrode modified with a catalyst of palladium-polyaniline/carbon microspheres@carbon nanotubes (Pd-PANI/CM@CNTs/E) for the detection of glucose oxidation. In the optimal condition, the proposed system produced good analytical performances. The sensor determined glucose linearly in a range from 0.020 to 100 mM, with a sensitivity of 51.51 μA mM−1 cm−2, and a detection limit (LOD) of 0.0071 mM. The developed system also exhibited good repeatability, reproducibility, operational stability, and anti-interference properties, and accurately determined glucose levels in real human serum samples. This sensing platform provides an alternative tool for the development of a continuous glucose monitor system for clinical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• Electrochemical glucose biosensor based on metal-free N-doped carbon material obtained from polyaniline. • High glucose sensitivity 23.57 ± 1.77 μA cm−2 mM−1 and linear working range 5 µM- 5 mM at −0.4 V vs. Ag/agcl (3 M KCl). • Glucose detection and quantification in commercial sugary drink and human urine sample have been performed. An enzymatic metal-free electrochemical biosensor based on immobilized glucose oxidase on a N-doped porous carbon material has been studied for the detection of glucose in different real samples. The N-doped carbon material, which contains quaternary nitrogen groups, has been obtained by heat treatment of polyaniline. These functionalities promote the electrocatalytic activity to oxygen reduction reaction. The electrochemical biosensor presents a remarkable electrochemical activity towards oxygen reduction reaction, being able to detect changes in oxygen concentration generated by the enzymatic oxidation of glucose, allowing the indirect detection of this compound in phosphate buffered solution (0.1 M PB solution, pH=7.2). The metal-free electrochemical biosensor shows an outstanding performance, with a linear detection range between 5 µM and 5 mM and a high sensitivity of 23.57±1.77 µA mM−1 cm−2 at -0.4 V vs. Ag/AgCl. At these conditions, the addition of ascorbic acid, dopamine, uric acid and l -gluconic acid does not interfere with glucose determination. The method has been successfully applied to human urine and commercial sugary drink samples, without significant matrix effects, providing an alternative for glucose detection. Image, graphical abstract [ABSTRACT FROM AUTHOR]