Dual-modal fiber-optic sensor for simultaneous pH and temperature monitoring in tumor microenvironment

The tumor microenvironment (TME) is a complex system. Temperature, pH, oxygen content, and other biomarkers comprehensively reflect the growth state of the tumor, necessitating a multi-parameter detection strategy to garner the precise status of tumor for treatment guidance. Fluorescence imaging technology is a promising tool for realizing this goal due to its advantages of low cost, real-time responses, and high sensitivity. However, several limitations, including the shallow penetration depth of fluorescence signals in biological tissues and the potential crosstalk between multiple fluorescence signals, hinder the practical application of current fluorescence imaging technology. In this paper, a dual-mode optical fiber sensor consisting of a fiber fluorescence pH sensor and a fiber Bragg grating (FBG) temperature sensor is presented. The compact sensor uses different principles for pH and temperature monitoring, thus effectively eliminating potential crosstalk between different signals. In addition, its small size allows it to be inserted into deep tissues for detection. The sensor responds quickly to changes in pH.Moreover, the temperature sensitivity of FBG packaged with PDMS is 34 % higher than the uncoated FBG. In vivo experiments confirmed that the sensor can accurately distinguish normal tissues and tumor tissues. The proposed sensor provides a novel way to realize multi-parameter monitoring of tumor microenvironment and improve the specificity of tumor detection.