Fiber-Optic Biological/Chemical Sensing System Based on Degradable Hydrogel

To improve the sensitivity and shorten the testing time of hydrogel-based bio-toxin sensors, we introduce an optical fiber Fabry-Perot interferometer (FPI) to detect the changes in the optical properties induced by the reactions between the target agent and the hydrogel. The concept is demonstrated by a polyacrylamide hydrogel filled into a cavity of an optical fiber FPI with a length of 150 mu m. Dithiothreitol (DTT) solutions with different concentrations were used as target agent. The degradation of the hydrogel by the DTT solution leads to a long and indistinct change in optical properties, which is difficult to be observed by conventional microscopy methods, but which can be detected by measuring the unique shifting process of the interfering spectrum caused by the hydrogel cleavage in the FPI cavity. Compared to our previous hydrogel-based sensor based on the microscopy observation, the sensitivity of the optic fiber FPI is improved by 2000 times, and the testing time is shortened from hundreds of hours to a few hours. Our approach opens up an avenue for highly sensitive, high-speed in-field detection of bio-toxins in live samples.