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An iron oxide/reduced graphene oxide (ION-RGO) nanocomposite has been fabricated to functionalize a low-cost electrochemical nitrite sensor realized by light-scribed reduced graphene oxide (LRGO) electrodes on a PET substrate. To enhance the stability and adhesion of the electrode, the PET substrate was modified by RF oxygen plasma, and a thin layer of the cationic poly (diallyl dimethyl ammonium chloride) was deposited. Raman spectroscopy and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDX) reveal that the light-scribing process successfully reduces graphene oxide while forming a porous multilayered structure. As confirmed by cyclic voltammetry, the LRGO electrochemical response to ferri-ferrocyanide and nitrite is significantly improved after functionalization with the ION-RGO nanocomposite film. Under optimized differential pulse voltammetry conditions, the LRGO/ION-RGO electrode responds linearly (R2 = 0.97) to nitrite in the range of 10–400 µM, achieving a limit of detection of 7.2 μM and sensitivity of 0.14 µA/µM. A single LRGO/ION-RGO electrode stands for 11 consecutive runs. The novel fabrication process leads to highly stable and reproducible electrodes for electrochemical sensors and thus offers a low-cost option for the rapid and sensitive detection of nitrite.

Glioblastoma is considered the most aggressive and prevalent type of glioma. Resistance mechanisms, side effects, and the blood–brain barrier are factors that make its treatment difficult, requiring the development of alternative therapeutic strategies. Herein, we propose a nanocomposite composed of carboxylated graphene oxide nanosheets decorated with zinc oxide nanoparticles and post-functionalized with Pluronic (GOC-ZnO-P) for chemotherapy against U87MG and U138MG human glioblastoma cell lines. The GOC-ZnO-P formulation is fairly stable in the physiological medium (DMEM-FBS) and demonstrates selectivity toward tumor cell lines, even though it is less cytotoxic than free ZnO. Whereas the photothermal activity of the nanocomposite has a negligible cytotoxic effect, images obtained by scanning and transmission electron microscopies reveal that it induces changes in adhesion points and roughness of the tumor cell membrane, and it is uptaken through vesicles and capable of accumulating in the nucleus, a process that can induce cell death by apoptosis, as verified by flow cytometry. In summary, the GOC phase serves as an inert platform for transporting ZnO, which maintains its selectivity for tumor cells and does not interfere with the mechanisms for inducing apoptotic pathways. Therefore, the GOC-ZnO-P nanocomposite offers a strategy for glioblastoma treatment.

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