Oliveira, DanielaOliveira, PedroXu, AnaRodrigues, EduardaGuerreiro, Susana G.Castro, Rafael C.Ribeiro, David S. M.Santos, João L. M.Piloto, Ana Margarida L.2025-02-112025-02-112025Oliveira, Daniela, Oliveira, Pedro, Xu, Ana, Rodrigues, Eduarda, Guerreiro, Susana G., Castro, Rafael C., Ribeiro, David S.M., Santos, João L.M. & Piloto, Ana Margarida L. (2025). Optical immunosensor panel using quantum dot-antibody conjugates for highly sensitive detection of carbohydrate antigen 19–9 (CA19-9). Analytica Chimica Acta, 1333. https://doi.org/10.1016/j.aca.2024.343399.0003-2670http://hdl.handle.net/10400.22/29454This study introduces a fluorescent immunosensor colour panel with antibody-conjugated quantum dots for detecting CA19-9 in human serum. The immunosensors presented decreasing fluorescence with increasing CA19-9 concentrations, with a linear detection range from 0.01 to 501.87 U mL−1 and detection limits of 1.66 × 10⁻⁴, 2.71 × 10⁻⁴, and 5.45 × 10⁻⁴ U mL−1 for the green-, orange-, and red-emitting conjugates in human serum. These limits are well below the 37 U mL−1 cutoff for early pancreatic cancer risk. The immunosensor panel is simple, sensitive, and specific, offering a visual colour readout for rapid CA19-9 detection, making it ideal for point-of-care applications. The results highlight the potential of the developed conjugates as a sensitive fluorescence colour panel for detecting CA19-9 across a wide range in human serum, both below and above the pancreatic cancer cutoff. With just 200 μL of sample and a single pre-filtration step, the assay delivers results in under 15 min, offering a cost-effective and efficient platform for point-of-care use.engCarbohydrate antigen 19–9 (CA19-9)Pancreatic cancer (PC)Quantum dots (QDs)Fluorescent panel immunosensorjournal article10.1016/j.aca.2024.343399