Self-referencing optrodes for measuring spatially resolved, real-time metabolic oxygen flux in plant systems

Abstract

The ability to non-invasively measure metabolic oxygen flux is a very important tool for physiologists interested in a variety of questions ranging from basic metabolism, growth/development, and stress adaptation. Technologies for measuring oxygen concentration near the surface of cells/tissues include electrochemical and optical techniques. A wealth of knowledge was gained using these tools for quantifying real-time physiology. Fiber-optic microprobes (optrodes) have recently been developed for measuring oxygen in a variety of biomedical and environmental applications. We have adopted the use of these optical microsensors for plant physiology applications, and used the microsensors in an advanced sensing modality known as self-referencing. Self-referencing is a non-invasive microsensor technique used for measuring real-time flux of analytes. This paper demonstrates the use of optical microsensors for non-invasively measuring rhizosphere oxygen flux associated with respiration in plant roots, as well as boundary layer oxygen flux in phytoplankton mats. Highly sensitive/selective optrodes had little to no hysteresis/calibration drift during experimentation, and an extremely high signal-to-noise ratio. We have used this new tool to compare various aspects of rhizosphere oxygen flux for roots of Glycine max, Zea mays, and Phaseolus vulgaris, and also mapped developmentally relevant profiles and distinct temporal patterns. We also characterized real-time respiratory patterns during inhibition of cytochrome and alternative oxidase pathways via pharmacology. Boundary layer oxygen flux was also measured for a phytoplankton mat during dark:light cycling and exposure to pharamacological inhibitors. This highly sensitive technology enables non-invasive study of oxygen transport in plant systems under physiologically relevant conditions.

A multiplexing fiber optic microsensor system for monitoring oxygen concentration in plants

“…The upper and lower limits of detection for the PtTFPP sensor in this study were 54 kPa and 1kPa, respectively. Response time for all sensors was less than 1 second, which was similar to the 2μm tapered microoptrodes in McLamore et al [7]. The measured hysteresis of the oxygen sensor was 0.5±0.4 % (n=6).…”

“…The average sensitivity was -1.26±0.21 °/kPa-O 2 between 0 and 21 kPa (n=6); and -3.92±1.2 °/kPa-O 2 between 21 and 32 kPa. These values were not significantly different than the 2μm tapered microoptrodes in McLamore et al [7].…”

“…Optrodes have been used in many laboratory and field experiments [7,[9][10][11][12]. To date, most (if not all) commercial systems developed for optrode sensing have been single channel systems.…”

Integrated paper-based electroanalytical devices for determination of dopamine extracted from striatum of rat

“…Electrochemical biosensors play critical roles in physiological research [25,26]. In electrochemical detection, the working electrode plays an important role because the electrochemical reactions occur on its surface.…”

Mouse and human islets survive and function after coating by biosilicification

“…Analyte flux is calculated using Fick's first law of diffusion (25) by continuously recording differential concentration (⌬C) while oscillating the microsensor between two locations separated by a fixed excursion distance (⌬X). An optical oxygen sensor was constructed by immobilizing an oxygen-quenched fluorescent dye (platinum tetrakis pentafluoropheynl porphyrin) on the tip of a tapered optical fiber (tip diameter 5 m) (29). Background flux was recorded in bulk medium at least 5 mm away from cellular material for 5 min.…”