Estriol sensing using miniaturized electrochemical sensor fabricated by laser-scribed graphene modified with Nafion® and TiO2:05Au nanoparticles

Estriol (E3) is an important endogenous hormone among estrogens, vital for fetal-placental health. Significant changes in its levels can signal serious medical conditions that require immediate medical attention [1]. The use of miniaturized electrochemical sensors and electroanalytical techniques offers many advantages for E3 analysis, including rapid analysis, cost-effectiveness and the possibility of miniaturization [2]. The fabrication of these devices by laser-scribed graphene (LSG) on low-cost substrates ensures a scalable, fast, and inexpensive sensor production [3]. In this work, an electrochemical sensor fabricated on polyimide by LSG is proposed. Raman and FT-IR spectroscopy confirmed that the sensor surface resembles reduced graphene oxide (rGO). Testing different modifiers revealed that combining Nafion^® and TiO₂:05Au nanoparticles enhanced the E3 signal by 93% and increased the electroactive area by 27%. Scan rate studies indicated E3 mass transport on the Nafion^®/TiO₂:05Au/LSG surface occurs via mixed diffusional-adsorptive mechanisms. pH studies showed optimal analytical response at pH 2, with a 1:1 ratio of protons and electrons in the E3 oxidation process. Differential Pulse Voltammetry (DPV) outperformed Square-wave voltammetry (SWV) for E3 detection and was chosen for quantitative analysis. Future steps include construction of the calibration curve, conducting selectivity tests, evaluating stability, and performing assays on real samples.