Engineering a Gd₂(WO₄)₃–P@rGO heterostructure for enhanced electrochemical sensing and therapeutic drug monitoring of erdafitinib

Erdafitinib (ERDF), a tyrosine-kinase inhibitor approved for metastatic urothelial carcinoma, possesses a narrow therapeutic index and risk of severe adverse effects, making its precise quantification essential for therapeutic drug monitoring, pharmacokinetic profiling, pharmaceutical quality control, and environmental surveillance. To address the lack of highly sensitive and accessible analytical platforms, a hybrid Gd₂(WO₄)₃–P@rGO nanocomposite was fabricated using a hydrothermal synthesis followed by ultrasonication-assisted integration and subsequently immobilized onto a glassy carbon electrode (GCE). Comprehensive structural and chemical characterization (SEM, TEM, XRD, FT-IR, and XPS) verified the successful formation of a well-distributed heterostructure with enhanced defect density, abundant active sites, and improved electronic coupling between Gd₂(WO₄)₃ and P-doped rGO. Electrochemical assessment using CV and DPV demonstrated a significantly amplified ERDF oxidation response, yielding an ultralow detection limit of 0.0024 nM (S/N = 3), high sensitivity (16.670 µA nM⁻¹ cm⁻²), and a broad linear range spanning 0.01–800 nM (R² = 0.9980). The modified electrode demonstrated excellent selectivity against common interferents, along with strong operational stability and reproducibility. Validation in spiked human serum and urine showed accurate recoveries with minimal matrix effects, meeting internationally recognized bioanalytical standards. Scalable fabrication without toxic reducing agents further underscores the platform’s environmental and practical advantages. Collectively, these attributes position the Gd₂(WO₄)₃–P@rGO sensor as a promising tool for therapeutic drug monitoring, personalized dosing, pharmacokinetics, and future point-of-care diagnostics.