Highly sensitive printed pH sensor using CB/PANI nanocomposite for POC diagnosis of orthopedic infections

Herein, we reported a potentiometric pH screen-printed electrode incorporating Carbon Black (CB) nanomaterial and chemically stable pH-sensitive Polyaniline (PANI) for revealing orthopedic infections, as pH is a pivotal biomarker. A dispersion of CB/PANI nanocomposite was easily drop-cast onto the working electrode surface to deliver a straightforward and efficient functionalization of the printed sensor. An in-depth psychochemical and morphological characterization of the nanocomposite was conducted by Dynamic Light Scattering, Electrophoretic Light Scattering, and Transmission Electron Microscopy. 90 % CB – 10 % PANI mixture was selected for electrode functionalization owing to an outstanding dispersibility and an efficient trade-off between linearity in the pH range 3–8 (R² = 0.994), reliable reproducibility (RSD% = 0.9 %, n = 3), and lack of memory effect, alongside noteworthy sensitivity (−74 ± 3 mV/pH unit). The proposed sensor further showcased a notable selectivity, resulting in negligible pH deviations when exposed to feasible interfering candidates in synovial fluid. Storage stability was also tracked for over 1 month by monitoring the potentiometric response of the designed sensor, kept dry at room temperature. The ANOVA analysis and post-hoc Tukey test demonstrated a stable potential signal, which has been achieved from the second week, with a performance coherence up to one month. Finally, sensor validation was carried out in real samples of healthy and infected synovial fluid by comparing the response of the developed sensor to the pH-meter and the outcome of microbiological analysis, demonstrating the accuracy and the effectiveness of the stable, highly sensitive, and mass-produced printed sensor.