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High-performance fiber-optic pH microsensors for practical physiological measurements using a dual-emission sensitive
1Department of Chemistry, University of Michigan, Ann Arbor 48109-1055, USA.
Analytical Chemistry
|March 1, 1997
Summary
A novel ratiometric pH microoptode using 5 (and 6)-carboxynaphthofluorescein (CNF) offers high accuracy and durability for biological applications. This optical sensor provides fast, reproducible pH measurements in physiological conditions.
Area of Science:
- Biomedical Engineering
- Analytical Chemistry
- Optical Sensing
Background:
- Accurate real-time pH monitoring is crucial for biological and physiological studies.
- Existing pH sensing technologies face limitations in speed, durability, and applicability in complex biological matrices.
- Development of microscale optical sensors offers potential for minimally invasive and precise measurements.
Purpose of the Study:
- To develop a fast, durable, and highly accurate ratiometric pH microoptode for physiological applications.
- To characterize the performance of the microoptode in terms of precision, sensitivity, response time, and reproducibility.
- To evaluate the suitability of the developed microoptode for biological sample analysis.
Main Methods:
- Fabrication of a microoptode by entrapping 5 (and 6)-carboxynaphthofluorescein (CNF) in a polyacrylamide gel matrix on an optical fiber.
- Utilizing photopolymerization for matrix immobilization.
- Employing ratiometric measurement principles based on pH-sensitive emission peaks around an isosbestic point.
Main Results:
- The CNF microoptode demonstrated high precision (better than +/- 0.03 pH unit) in physiological buffers and biological samples.
- Response times were as fast as 1 ms for pulled optodes.
- The sensor exhibited excellent durability, retaining sensitivity over thousands of measurements and a 7-week period.
- Minimal errors were observed due to photobleaching, leaching, quenching, or excitation source fluctuations.
Conclusions:
- A highly accurate, precise, sensitive, reversible, and reproducible ratiometric pH microoptode has been successfully developed.
- The CNF microoptode is well-suited for biological applications due to its linear response in the physiological pH range (7-8) and high sensitivity.
- The developed sensor minimizes common sources of error, making it a reliable tool for in-situ pH monitoring.