Enhancing resolution of a miniaturized surface plasmon resonance sensor using bimetallic-based chip

In this study, a performance of a waveguide coupled bimetallic (WCBiM) chip in a miniaturized surface plasmon resonance (SPR) sensor in a reflectance detection mode was investigated by comparison with a conventional gold (Au) chip. The WCBiM chip makes sharper slope in the SPR curve than conventional Au chip. The detection abilities of both sensor chips were tested by monitoring an interaction between streptavidin and biotin (very low molecular weight). Firstly, an incident light was fixed at an angle which was steepest slope in the scanned the SPR curve; then, the output signal was measured at fixed angle. The streptavidin diluted to 50 mu g/ml in the phosphate buffered saline (PBS) was injected into a fluidic module of the SPR sensor. Next, the biotin diluted to 50 ng/ml, 100 ng/ml, 150 ng/ml and 200 ng/ml in the PBS were injected into the sensor. In results, the reflectance increments of the lowest concentration of the biotin (50 ng/ml) using the WCBiM chip and Au chip were 0.11 % and 0.04 %, respectively. Experimental results showed that detection ability of the WCBiM chip was about three times larger than that of conventional Au chip. In conclusion, the miniaturized SPR sensor in the reflectance detection mode using the WCBiM chip was expected to detect the biomolecules at trace level concentration or low molecular weight with high resolution.