Fluorescence 'turn-on' sensing of glial fibrillary acidic protein using graphene oxide-quenched copper nanoclusters

This study introduces a fluorescence based sensing platform made to detect glial fibrillary acidic protein (GFAP), a critical biomarker associated with glioblastoma and other astrocytic malignancies. Leveraging the unique optical properties of copper nanoclusters (CuNCs) functionalized with GFAP antibodies (GFAP Ab), the platform incorporates graphene oxide (GO) as a fluorescence quencher to create a highly sensitive turn on sensor responsive to GFAP antigens. The detection mechanism relies on Förster resonance energy transfer (FRET), wherein the binding of GFAP antigens disrupts the GFAP Ab@CuNCs-GO interaction, effectively restoring fluorescence. The CuNCs stabilized with l-cysteine to enhance biocompatibility and stability, exhibited strong green fluorescence with a quantum yield of 1.0%. Graphene oxide efficiently quenched the fluorescence of GFAP Ab@CuNCs therefore enhancing the platform's sensitivity. The sensor displayed a linear fluorescence response across a GFAP concentration range 0-46 ng/mL, with a detection limit of 32 pg/mL, demonstrating its capability to detect GFAP at clinically relevant levels. Validation of the sensor in biological fluids, including saliva, serum and urine, confirmed its applicability for minimally invasive diagnostics. Situated at the intersection of biosensing and clinical relevance, this study aims to address the need for cost effective and accessible diagnostic and screening tools for glioblastoma.