A Novel High Sensitivity Fiber SPR Sensor for the Specific Detection of Baohuoside-I

Fiber SPR sensors can be used for rapid detection of active ingredients in traditional Chinese medicine. To achieve micro-detection of specific active ingredients in traditional Chinese medicine, its further development requires significantly improving sensitivity and achieving specific detection. In this article, we proposed and demonstrated a new type of highly sensitive and specific detection fiber SPR sensor, which employed a graded index multimode fiber as the sensing fiber. Due to the self-focusing effect of the graded index multimode fiber, the mode number of transmission light in the sensing area is significantly reduced. By using an eccentric core fiber to inject light and controlling the depth of the flat bottom groove made on the graded index multimode fiber to control the incident angle of light, the sensitivity of the fiber SPR sensor is greatly improved. By modifying the Retinoid X Receptor
$\alpha $
(RXR
$\alpha $
) protein on the surface of sensing gold film, the specific recognition of the active ingredient Baohuoside I in traditional Chinese medicine Epimedium has been achieved. According to the experiment, the sensor has a detection sensitivity of 0.66 nm/(
$\mu \text{g}$
/ml) and a LOD of
$0.15 ~\mu \text{g}$
/ml. At a concentration of
$100 ~\mu \text{g}$
/ml, the wavelength shift of Baohuoside I or a mixed solution containing Baohuoside I is higher than 60 nm, while the wavelength shift of other components is lower than 10 nm. The new sensor proposed in this article has a stable structure, high sensitivity, and specific recognition ability, providing a new solution for the highly sensitive detection of specific active ingredients in traditional Chinese medicine using fiber SPR sensors.