Development of a Nonenzymatic Potentiometric or Amperometric Lactate Biosensor Enhanced by Silver Phosphate/Titanium Dioxide on Flexible Printed Circuit Board

In this study, a nonenzymatic lactate biosensor based on a novel silver phosphate and titanium dioxide (Ag3PO4/TiO2)-modified SnO2 sensing platform was developed to improve the detection performance. Different from traditional enzyme or single metal oxide sensors, this work introduces a catalytic composite Ag3PO4/TiO2 combined with SnO2 to enhance charge transfer and surface reactivity under ambient conditions. This improvement significantly increased the selectivity and average sensitivity of lactate detection. The interaction of lactic acid with the composite material induces measurable voltage or current changes, which can be characterized through voltage-time (V– ${T}\text {)}$ and current-time (I– ${T}\text {)}$ measurements. The proposed lactate biosensor demonstrated a sensitivity of $43.38~\mu $ A $\cdot $ mM ${}^{-{1}}~\cdot $ cm ${}^{-{2}}$ with a linearity of 0.997 in amperometric measurements, and a sensitivity of 8.09 mV/mM with a linearity of 0.992 in potentiometric measurements. The limit of detection (LOD) was as low as 0.01 mM, the response time was only $6~{s}$ , and excellent selectivity was observed against common interfering species such as glucose, uric acid (UA), as well as ascorbic acid (AA). The experimental results show that the Ag3PO4/TiO2 modified sensor exhibits higher sensitivity, improved linearity over a wider lactic acid concentration range, and superior stability compared to the unmodified SnO2 sensor. Structural and morphological analyses (X-Ray diffractometer (XRD), SEM, Raman) confirmed the homogeneous dispersion and successful integration of the composites. In addition, this sensor also has the characteristics of fast response speed, high selectivity, low hysteresis, and good long-term operation stability. These findings suggest that the proposed Ag3PO4/TiO2SnO2 platform provides a promising alternative to conventional lactate sensing strategies, especially in nonenzymatic detection systems.