ANTIBODY/APTAMER-BASED AFFINITY PURIFICATION WITH RAMAN LABEL FOR SENSITIVE DETECTION OF CA 125

Epithelial ovarian cancer (EOC) is considered to have higher mortality, with no or few symptoms at an early stage and a poor prognosis. The treatments and survival solely depend on the stage of cancer at diagnosis. Developing a non-invasive technique that can detect biomarkers (antigens) with sufficient sensitivity, selectivity, and reproducibility is a promising approach to overcome the challenges in the early diagnosis of EOC. The bioconjugation technique is a promising approach for detecting serum biomarkers, such as cancer antigen 125 (CA 125) and human epididymis protein 4 (HE4) at low concentrations.

This study investigates the affinity of antibody and aptamer towards CA 125 and the sensitivity of each approach using affinity purification with gold nanoparticles (AuNps) with Raman-label. For this purpose, Ni-NTA (Nickel-nitrilotriacetic acid) microparticles, used for the magnetic separation process, were conjugated to CA 125-Histidine (CA 125 His Tag). It was then allowed to bind biotinylated antibodies or aptamers. Afterward, the conjugate was incubated with gold nanoparticles pre-modified with streptavidin and a Raman label. After the magnetic separation process, the final conjugate was investigated with surface-enhanced Raman spectroscopy. The Raman signatures from the label verified the sandwich-type conjugation of the CA 125-antibody or CA125-aptamer complex in between Ni-NTA and AuNPs.