Single-loop fiber ATR sensor enhanced by silver nanoparticles for continuous glucose monitoring

A miniaturized fiber Attenuated Total Reflection (ATR) sensor based on mid-infrared spectroscopy was proposed to overcome the drawbacks of enzyme electrode sensor for implantable continuous glucose monitoring. Two methods were proposed to improve the sensitivity of fiber ATR sensors. A single-loop structure of fiber ATR sensor was used to increase the effective optical length to enhance the sensitivity. By growing silver nanoparticles (AgNPs) on the cylindrical surface of the fiber ATR sensor with chemical silver mirror method, the sensitivity of the infrared absorption signal was further enhanced. In the experiment, the AgNPs modified fiber ATR sensor showed an intense absorption signal for glucose with enhancement factors of two to six times at different absorption wavenumbers compared with the bare fiber ATR sensors. The prediction of glucose concentration with high accuracy was achieved by using the five-variable partial least-squares model yielding a root-mean-square error of prediction as small as 4.45 mg/dL.