Optical fibre chemical sensors and biosensors based on fluorescent polymers

Abstract

Optical fibre-based pH sensors have been well explored and studied for physiological use since the development of the first optical fibre pH probe in 1980. However, the need for robust attachment of pH reporters onto the end of the optical fibre has driven considerable efforts in order to develop better, more robust, devices. In my PhD, I exploited and developed polymer microarray technology as a high-throughput means to discover optimal polymeric matrixes with the abilities to trap reporter molecules while responding rapidly to pH. Initially, contact printing was utilized to identify preformed polymers, which allowed, via dip-coating, attachment of fluorescent pH reporters onto the tip of an optical fibre. This resulted in a robust, rapidly responding and reliable optical fibre pH sensor, which was used to measure subtle pH changes in lung tissue validating its capabilities for biomedical applications. Parts of this work have been published in ACS Comb. Sci. 2019, 21, 417-424. Evolving this concept, a compact hydrogel-based optical fibre pH sensor was fabricated by in-situ photo-polymerization on the end of the optical fibre. Here inkjet printing was used for the high-throughput discovery of the optimal matrix for pH reporter immobilization, while two dyes (5(6)-FAM and Porphyrin) were used to offer a robust ratiometric method to measure pH. The fabricated hydrogel-based sensor responded rapidly to pH changes (less than 30s) and showed a linear response to pH within the physiological pH range with a precision of 0.10 pH units. This new optical fibre sensor was used to measure pH of normal and tumorous tissue, showing that tumorous tissue was more acidic compared to normal tissue, thus offering the potential for rapid and accurate observation of pH tissue changes.