Cost-effective protocol to produce 3D-printed electrochemical devices using a 3D pen and lab-made filaments to ciprofloxacin sensing.

A novel conductive filament based on graphite (Gr) dispersed in polylactic acid polymer matrix (PLA) is described to produce 3D-electrochemical devices (Gr/PLA). This conductive filament was used to additively manufacture electrochemical sensors using the 3D pen. Thermogravimetric analysis confirmed that Gr was successfully incorporated into PLA, achieving a composite material (40:60% w/w, Gr and PLA, respectively), while Raman and scanning electron microscopy revealed the presence of defects and a high porosity on the electrode surface, which contributes to improved electrochemical performance. The 3D-printed Gr/PLA electrode provided a more favorable charge transfer (335 Ω) than the conventional glassy carbon (1277 Ω) and 3D-printed Proto-pasta® (3750 Ω) electrodes. As a proof of concept, the ciprofloxacin antibiotic, a species of multiple interest, was selected as a model molecule. Thus, a square wave voltammetry (SWV) method was proposed in the potential range + 0.9 to + 1.3 V (vs Ag|AgCl|KCl), which provided a wide linear working range (2 to 32 µmol L), 1.79 µmol L limit of detection (LOD), suitable precision (RSD < 7.9%), and recovery values from 94 to 109% when applied to pharmaceutical and milk samples. Additionally, the sensor is free from the interference of other antibiotics routinely employed in veterinary practices. This device is disposable, cost-effective, feasibly produced in financially limited laboratories, and consequently promising for evaluation of other antibiotic species in routine applications.