Fig. 4
From: Liquid crystal-amplified optofluidic biosensor for ultra-highly sensitive and stable protein assay
(a) Oil was filled in resonator to study the effect of BSA absorption behavior on WGM spectral wavelength shift. The WGM spectral responses at 10− 3 g/ml BSA (left panel) showed only red-shift tendency and the overall wavelength shift under several BSA concentrations was shown in right panel. (b) The overall wavelength shift responses from WGM laser spectra under various BSA concentrations (from 10− 12 to 10− 3 g/ml) are calculated by summing up the blue shift distance and the red shift distance. The left panel exhibits the corresponding wavelength responses at various extremely low BSA concentrations (10− 12, 4 × 10− 12, 7 × 10− 12 and 10− 11 g/ml). According to the calibration curve, the limit of detection for BSA is 1.92 fM (1.28 × 10− 13 g/ml)