In vitro and in vivo measurements of fiber optic and electrochemical sensors to monitor brain tissue pH

We report herein the development of fiber optic and electrochemical pH sensors that could become part of an arsenal to quickly and aggressively treat people undergoing a stroke as well as people who have suffered traumatic brain injury. The fiber optic pH sensor design consists of the immobilization of a pH sensitive dye, seminaphthorhodamine-1 carboxylate (SNARF-1C) within a silica sol–gel matrix. A miniature optoelectronics package was developed to acquire data from the fiber optic sensor. The electrochemical sensor consists of a thin film multilayer coating sputtered on a kapton substrate. The sensors were tested in vitro and in vivo. For both sensors, the in vitro results show linear and reproducible responses in human blood in the pH range 6.8–8.0. The results of the in vivo studies which were performed in Spraque–Dawley rats indicate that both the fiber optic and electrochemical sensors monitor pH with very little drift. It was concluded that both types of sensors would be useful in tracking brain tissue pH.