Ultra-Sensitive Detection of Biomarker using Localized Surface Plasmon Resonance (LSPR) enhanced by ELISA

We demonstrate a highly sensitive detection of AFP (alpha-fetoprotein) protein (liver cancer marker) in human serum using the LSPR biosensor. Gold metal nanodot array (MNA) on a glass wafer were fabricated by UV nanoimprint lithography (NIL). After the NIL process using a film stamp and the removal of residual layer via oxygen plasma etching, metal films were deposited using an electron-beam evaporator, followed by the lift-off step. Consequently, the gold MNA was realized on 5-inch glass wafer and the pitch, diameter and height of MNA were 300nm, 150 nm and 20 nm, respectively. We employed observation of LSPR spectra via back-reflection, which provides a stable measurement of LSPR because a probe light does not pass a bio-sample. In addition, one channel among two flow channels was used a control channel, the MNA surface in which was modified with bovine serum albumin, not antibody. After antigen-antibody reaction, the enzyme/precipitation was employed on the MNA (Nano-ELISA). As a result, we could detect AFP in 50 mu L human serum with limit of detection (LOD) of 0.7 zeptomole (10(-21) mole).