Vertical graphene-based electrochemical sensor for cisplatin detection and molecular recognition

The reliable monitoring of platinum-based chemotherapeutics remains a major analytical challenge due to their narrow therapeutic window and high reactivity toward biomolecules. Here, we report a dual-architecture electrochemical platform based on vertical graphene (VG) for the label-free detection of cisplatin and biomimetic probing of its molecular interactions with nucleic acids. Two complementary sensing interfaces were integrated on microfabricated VG/Au/TiN/SiO₂/Si interdigitated electrodes (IDEs): (i) VG decorated with gold nanoparticles (VG/AuNPs) for enhanced electrocatalytic signal amplification, and (ii) VG functionalized with a guanine oligonucleotide probe (VG/PolyG) enabling selective molecular recognition via Pt-N7 coordination. Surface characterization by Fourier-transform infrared (FTIR) and Raman spectroscopy confirms the successful functionalization of the VG interfaces, while morphological and elemental analyses (field-emission scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy system (EDX)) verify the uniform decoration of AuNPs on the electrode surface. Electrochemical measurements, including cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS), validate the stepwise assembly and functional performance of both sensing architectures. The VG/AuNPs sensor exhibits a linear response toward cisplatin in the 0.5-10 μM range (R² = 0.9595), with a limit of detection (LOD) of 3.29 μM, consistent with clinically relevant free cisplatin concentrations in plasma. In parallel, the VG/PolyG interface transduces Pt-N7 guanine coordination into a concentration-dependent change in charge-transfer resistance, providing direct insight into drug-biomolecule interactions. This dual-architecture platform simultaneously combines electrocatalytic amplification with biomimetic molecular recognition within a single microfabricated device, offering a versatile and mechanistically informative approach for therapeutic drug monitoring and the investigation of platinum-DNA interactions.