Non-invasive tools for measuring metabolism and biophysical analyte transport: self-referencing physiological sensing

Abstract

Biophysical phenomena related to cellular biochemistry and transport are spatially and temporally dynamic, and are directly involved in the regulation of physiology at the sub-cellular to tissue spatial scale. Real time monitoring of transmembrane transport provides information about the physiology and viability of cells, tissues, and organisms. Combining information learned from real time transport studies with genomics and proteomics allows us to better understand the functional and mechanistic aspects of cellular and sub-cellular systems. To accomplish this, ultrasensitive sensing technologies are required to probe this functional realm of biological systems with high temporal and spatial resolution. In addition to ongoing research aimed at developing new and enhanced sensors (e.g., increased sensitivity, enhanced analyte selectivity, reduced response time, and novel microfabrication approaches), work over the last few decades has advanced sensor utility through new sensing modalities that extend and enhance the data recorded by sensors. A microsensor technique based on phase sensitive detection of real time biophysical transport is reviewed here. The self-referencing technique converts non-invasive extracellular concentration sensors into dynamic flux sensors for measuring transport from the membrane to the tissue scale. In this tutorial review, we discuss the use of self-referencing micro/nanosensors for measuring physiological activity of living cells/tissues in agricultural, environmental, and biomedical applications comprehensible to any scientist/engineer.

The Signal Transducer NPH3 Integrates the Phototropin1 Photosensor with PIN2-Based Polar Auxin Transport in Arabidopsis Root Phototropism

“…This different behavior was not unexpected, as PIN2 is not expressed in Arabidopsis hypocotyls (Chen et al, 1998). Moreover, in vivo measurements of auxin flow in the root tips showed that the root apex transition zone (0.1 to 0.3 mm from the root tip in Arabidopsis; Verbelen et al, 2006;Baluš ka et al, 2010) is the most active region with respect to polar auxin flow Baluš ka et al, 2010;McLamore et al, 2010;McLamore and Porterfield, 2011) and gravity-stimulated peak cell elongation rates (Chavarria-Krauser et al, 2008). A BL illumination significantly increased the peak value of the auxin flux rate in the root apex transition zone of both dark-grown wildtype and pin2 seedlings, among which the response of the pin2 mutant was less significant than that of the wild type.…”

“…Measurement of the rhizosphere auxin flux reflex activity of cell-to-cell auxin transport, which occurs in the apoplast, provides a quantitative analysis of polar auxin transport (McLamore et al, 2010;McLamore and Porterfield, 2011). A carbon nanotube auxin-selective microelectrode was used to monitor auxin fluxes in Arabidopsis roots as described previously Santelia et al, 2005;Bouchard et al, 2006;Bailly et al, 2008;Kim et al, 2010).…”

Processing Issues and the Characterization of Soft Electrochemical 3D Sensor

“…Real-time, non-invasive monitoring of cellular processes from cell cultures has received increased interest in the past decades [39,22,40]. Electrochemical sensors can provide a wide range of information on biophysical and biochemical events.…”

“…Molecules that are directly relevant to metabolism (e.g., oxygen, adenosine triphosphate), homeostasis (e.g., H + , Na + , K + , Ca 2 + ), and cell signaling (e.g., nitric oxide, glutamate, dopamine) can be measured using these techniques. Over the past years there have been intensive efforts to develop non-invasive tools for cellular microphysiology monitoring [22,23]. Due to demonstrated sensitivity and non-invasiveness, electrochemical detection methods have been applied for cell-based investigation [24,25].…”

Determining rates of epithelial solute transport by optical measurement of fluorochrome concentration gradients in the unstirred layer

“…Potentiometric electrodes are available for common physiological ions (Na ) and for organic anions such as salicylate and organic cations such as tetraethylammonium. In addition, amperometric electrodes and/or optrodes have been developed for molecules such as oxygen, glucose and nitric oxide (Smith et al, 2007;McLamore and Porterfield, 2011).…”