Plasma-treated paper device for instrument-free decentralized fluorescence metalloimmunoassay of carcinoembryonic antigen

This work initially investigated potential changes in the surface chemistry of cellulose induced by oxygen plasma treatment through the application of complementary optical surface characterization techniques. Subsequently, a simplified paper-based metalloimmunoassay for carcinoembryonic antigen (CEA) detection was developed, employing plasma-treated paper disks as the functional substrate. In-house synthesized CdS quantum dots (QDs) were directly bio-conjugated to reporter anti-CEA antibody and were utilized as fluorescent labels using simple instrumentation for detection. The plasma-treated paper demonstrated enhanced analytical sensitivity, attributed to the increased exposure of cellulose fibers following treatment. The proposed assay achieved a limit of detection of 0.09 ng mL⁻¹ for CEA, significantly below the clinical cut-off value of 5 ng mL⁻¹. The recoveries in serum samples were in the range 103–120%, with relative standard deviations ranging from 6.2% to 12.4%. The paper-based metalloimmunoassay represents a field-deployable sensing tool with potential for point-of-care applications, particularly in resource-limited settings.