Photo-triggered g-C₃N₄/Ag₂S nanoenzyme based colorimetric immunosensor for carbohydrate antigen 19-9 detection

Area of Science:

• Biomarker detection
• Nanomaterials in diagnostics
• Colorimetric immunoassays

Background:

• Carbohydrate antigen 19-9 (CA19-9) is a key biomarker in oncology for tumor detection and treatment monitoring.
• Sensitive and reliable detection methods for CA19-9 are crucial for clinical applications.
• Existing methods may require improvement in sensitivity, specificity, or practicality.

Purpose of the Study:

• To develop a novel, highly sensitive colorimetric immunoassay for CA19-9 detection.
• To utilize g-C₃N₄/Ag₂S nanocomposites as photoactive signal probes for enhanced detection.
• To validate the assay's performance and applicability in human serum samples for clinical oncology.

Main Methods:

• Synthesis of g-C₃N₄/Ag₂S nanocomposites via a hydrothermal method.
• Development of a colorimetric immunoassay using antibody-functionalized magnetic beads for CA19-9 capture.
• Labeling with g-C₃N₄/Ag₂S nanocomposite probes and detection via visible light-catalyzed TMB oxidation and UV-vis spectroscopy.

Main Results:

• The assay demonstrated a wide linear detection range (4.0–400 U/mL) and a low detection limit (1.86 U/mL).
• High specificity, stability, and reproducibility were achieved.
• The method was successfully applied to human serum samples, confirming its practical utility.

Conclusions:

• The developed g-C₃N₄/Ag₂S nanocomposite-based colorimetric immunoassay offers a sensitive and reliable method for CA19-9 detection.
• This novel assay holds significant promise for clinical cancer diagnosis and screening.
• The photocatalytic activity of the nanocomposites provides an effective signal amplification strategy for biomarker detection.