Biogenic carbon dot-based fluorescence-mediated immunosensor for the detection of disease biomarker

The dynamic interplay of nanotechnology and immunoassay has unlocked an arena for developing next-generation techniques to contribute to detecting disease biomarkers. Herein, the work establishes the strategic fabrication of an immunosensor by sandwich technique based on the fluorescence phenomenon of carbon dots for the detection of the disease biomarker VEGF (Vascular Endothelial Growth Factor). VEGF, a biomarker for angiogenesis, is considered cancerous if found in elevated levels in the blood, and so is paramount for early detection of disease. Carbon dots derived from a biogenic source were synthesized employing a green microwave-assisted method followed by conjugating with a detection antibody, human immunoglobulin G (IgG), via EDC-NHS amidation reaction. On the other hand, the VEGF biomarker was immobilized onto the capture antibody. The detection antibody tagged with the fluorescent probe is employed as a bridge to connect with the VEGF biomarkers bound to the capture antibody. The response to different concentrations of VEGF biomarkers was recorded in terms of the fluorescence intensity of the carbon dots. The fluorescence immunosensor could exhibit a wide linear range of 0.1 fg/mL to 10 pg/mL with a low detection limit of 5.65 pg/mL towards VEGF. The potentiality of this designed immunosensor was qualitatively assessed with human blood plasma samples, showing promising results, thereby upholding the applicability of carbon dots as fluorescent labels in immunoassay techniques.