Biomimetic 3D printable electrochemical filament integrated with CuO nanopowder for enzyme-free biosensing

3D printing technology enables the on-demand fabrication of low-cost thermoplastic electrodes, which have shown promising results in enzymatic bioassays. To fully harness the potential of 3D printing in electrochemical biosensing, this work introduces a new generation of tailor-made conductive filament integrated with a biomimetic functional material for the 3D printing of ready-to-use sensors designed for enzyme-free biodeterminations. The filament was synthesized using the solvent casting method and was composed of polylactic acid as the base, carbon black as the conductive filler, and CuO nanopowder as the artificial nanozyme. The filament was characterized using thermogravimetry, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and electrochemical techniques. The as-printed sensors enabled direct electrochemical monitoring of crucial bioindicators—glucose (GLU), lactic acid (LA), and creatinine (CRE)—with exceptional sensitivity, offering limits of detection of 5.1 µM, 0.12 mM, and 1.5 µM, respectively. Moreover, the sensors exhibited high anti-interference capability and were successfully applied to the determination of the target biomarkers in blood, sweat, and urine samples. The amperometric determination of GLU was based on the conversion of integrated CuO to CuOOH, which subsequently oxidized GLU to gluconic acid. The voltammetric determination of CRE was based on the formation of copper-creatinine complexes, resulting in the suppression of the oxidation signal of electrogenerated copper. Meanwhile, LA voltammetric detection relied on the characteristic increases in the redox signals of CuO. This work paves the way for the development of accessible, point-of-need printable, and ready-to-use electrochemical biomimetic sensors for easy applications in the biosensing field.