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<p>A disposable electrochemical sensor based on a competitive surface-blocking mechanism driven by covalent epoxide–amine coupling is reported for the selective voltammetric determination of fosfomycin (Fos). The sensing strategy employs ferrocen (Fc)-tagged surface chemistry as a redox reporter, where Fc surface occupancy inversely reflects Fos binding to cysteamine-derived amine groups. Screen-printed carbon electrodes (SPCEs) modified with a reduced graphene oxide/gold nanoparticle (rGO/AuNP) nanocomposite provide enhanced electroactive surface area and improved electron-transfer kinetics. Increasing Fos concentrations progressively consume surface amines, reducing Fc labeling and leading to a concentration-dependent decrease of the differential pulse voltammetric oxidation signal. Under optimized conditions, the sensor exhibits a linear response from 50 to 2000 µM with a limit of detection of 10 µM, matching the clinically relevant mid-therapeutic range of intravenous fosfomycin therapy (≈ 7–276&#xa0;mg L⁻¹). Matrix effects are effectively minimized by controlled serum dilution, enabling accurate Fos quantification with recoveries of 97.8–103.7% and without extensive sample pretreatment. The platform retains stable performance for at least 15 days at 4&#xa0;°C. Rather than replacing chromatographic techniques, this proof-of-concept platform is positioned as a rapid, low-cost, and portable electrochemical tool for routine therapeutic drug monitoring and point-of-care screening.</p> Graphical abstract <p></p>

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Competitive surface-blocking electrochemical sensor for fosfomycin detection based on ferrocen-tagged surface chemistry

  • 期刊论文

  • 发表日期：

    2026年2月25日

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  • Mohamed Zouari,
  • Ahmet Cetinkaya,
  • Sibel A. Ozkan

摘要

A disposable electrochemical sensor based on a competitive surface-blocking mechanism driven by covalent epoxide–amine coupling is reported for the selective voltammetric determination of fosfomycin (Fos). The sensing strategy employs ferrocen (Fc)-tagged surface chemistry as a redox reporter, where Fc surface occupancy inversely reflects Fos binding to cysteamine-derived amine groups. Screen-printed carbon electrodes (SPCEs) modified with a reduced graphene oxide/gold nanoparticle (rGO/AuNP) nanocomposite provide enhanced electroactive surface area and improved electron-transfer kinetics. Increasing Fos concentrations progressively consume surface amines, reducing Fc labeling and leading to a concentration-dependent decrease of the differential pulse voltammetric oxidation signal. Under optimized conditions, the sensor exhibits a linear response from 50 to 2000 µM with a limit of detection of 10 µM, matching the clinically relevant mid-therapeutic range of intravenous fosfomycin therapy (≈ 7–276 mg L⁻¹). Matrix effects are effectively minimized by controlled serum dilution, enabling accurate Fos quantification with recoveries of 97.8–103.7% and without extensive sample pretreatment. The platform retains stable performance for at least 15 days at 4 °C. Rather than replacing chromatographic techniques, this proof-of-concept platform is positioned as a rapid, low-cost, and portable electrochemical tool for routine therapeutic drug monitoring and point-of-care screening.

Graphical abstract