<![CDATA[Carbon dots (CDs) are widely utilized in biomedical applications as fluorescent labels for imaging and diagnostics due to their excellent biocompatibility and superior optical properties. These advantages often make CDs a substitute for organic fluorescent dyes, which suffer from low emission intensity and poor photostability when interacting with biomolecules. Moreover, carbon-based materials are eco-friendly and can be synthesized from natural sources, such as curcumin, a chromophore compound abundantly available in Indonesia. Therefore, this study conducted a preliminary investigation on curcumin CDs-labeled IgY antibodies (IgY-cur CDs) for fluorescence immunoassay of SARS-CoV-2 in rapid test applications. The synthesis of the fluorescent label involved a carbodiimide coupling reaction using EDC/NHS agents to conjugate IgY antibodies with curcumin CDs. The IgY-cur CDs conjugate was confirmed to detect antigens through FRET immunosensor mechanisms, showing a significant increase in fluorescence intensity with increasing antigen concentrations (p < 0.05), with a minimum sample concentration of 10 ng. Furthermore, the IgY-CDs cur conjugate was applied as a reporter in a fluorescence-based LFIA using a sandwich assay format. The test strip successfully detected synthetic multiepitope SARS-CoV-2 antigens with an estimated detection limit of 54.28 µg and nasopharyngeal samples from confirmed COVID-19 patients within 35 minutes of operation. The test strip was evaluated to be stable under cold storage at 4°C for up to 3 weeks. In conclusion, curcumin CDs-labeled IgY antibodies demonstrate promising potential for further development as fluorescent labels in rapid diagnostic applications targeting SARS-CoV-2.]]>
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