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Development of Fiber Optic and Electrochemical pH Sensors to Monitor Brain Tissue

Sheila A. Grant
Center for Biomedical Engineering, Michigan Technological University, Houghton, Ml

Kerry Bettencourt
Lawrence Livermore National Laboratory, Livermore, CA

Peter Krulevitch
Lawrence Livermore National Laboratory, Livermore, CA

Julie Hamilton
Lawrence Livermore National Laboratory, Livermore, CA

Robert Glass
Lawrence Livermore National Laboratory, Livermore, CA

ABSTRACT

This article describes fiber optic and electrochemical pH sensors that could become part of a therapeutic arsenal to quickly and aggressively treat stroke victims as well as people who have suffered brain trauma. The fiber optic sensor design was based on the immobilization of a pH-sensitive dye, seminaphthorhodamine-1 carboxylate (SNARF-1C), onto the end of a 125-mm-diameter silica optical fiber using the sol-gel method. A miniature bench-top fluorimeter system was developed for use with the optical fiber to obtain pH measurements. The electrochemical sensor was based on sputter-coated indium oxide thin films. Linear and reproducible responses for both sensors were obtained in human blood with pH varying between 6.8 to 8.0, which encompasses the clinically relevant range. In vivo studies were also performed and results indicated that both types of sensors tracked pH with very little drift.