Femto-molar detection of cancer marker-protein based on immuno-nanoplasmonics at single-nanoparticle scale

We describe an in vitro biomarker sensor based on immuno-silver nanomarbles (iSNMs) and the nanoscattering spectrum imaging analysis system using localized surface plasmon resonance (LSPR). In particular, highly monodisperse SNMs with large figures of merit are prepared, and the sensing substrates are also fabricated using the nanoparticle adsorption method. The high sensitivity of the LSPR sensor based on an SNM is confirmed using various solvents that have different refractive indexes. For the sensitive and specific detection of epithelial cell adhesion molecules (EpCAMs) expressed on cancer cells, the surface of the SNM is conjugated with an anti-EpCAM aptamer, and molecular sensing for the EpCAM expression level is carried out using whole cell lysates from various cancer cell lines. Collectively, we have developed a biomarker-detectable LSPR sensor based on iSNMs, which allows for the sensitive and effective detection of EpCAMs at both the single-cell and femto-molar level.