Lectin-based optical sensing for quantitative analysis of cancer antigen CA15-3 as a breast cancer marker

Accurate detection of tumor-associated biomarkers remains a challenge in the diagnosis of cancer. To address the issue, we developed a sensitive biosensing system using lectins for breast cancer diagnosis based on the analysis of tumor-associated O-linked glycoprotein such as cancer antigen 15-3 (CA15-3). In cancerous cells, aberrant short-terminated glycan moieties such as TF-antigen and sialic acid are expressed on cell surfaces, becoming cancer antigens. Based on the difference between the glycan moieties in normal and cancer cells, CA15-3 was biospecifically detected using Sambucus nigra agglutinin (SNA) and peanut agglutinin (PNA) lectins. These lectins were conjugated with fluoro-microbeads and used as a detection molecule for an antibody–lectin sandwich assay. A fluoro-microbead guiding chip (FMGC) containing multiple sensing and fluidic channels was designed to measure CA15-3 proteins using the lectin-based assay. A capture antibody against CA15-3 that binds to the peptide backbone was immobilized on the gold-patterned sensing surface. On the modified FMGC, antibody–lectin sandwich assay for target CA15-3 was conducted. The developed PNA- and SNA-based assays, which exhibited a detection limit of 1.2 and 0.4 U/mL, worked well over the clinically important range from 1.25 to 25 U/mL CA15-3. The developed biosensor showed good sensitivity, fast response and reproducibility with a small volume of sample. This lectin-based sandwich assay provides a promising tool for the quantitative diagnosis of CA15-3 and glycated markers in clinical applications.