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.