microrespirometry

Microrespirometry is a set of methods for measuring respiration rates in very small biological samples, ranging from single cells to tiny tissue pieces, using miniaturized oxygen sensors and micro-chamber systems. It determines the rate of oxygen consumption, a proxy for metabolic activity, often reported as nmol O2 per minute per cell or per mg protein.

Techniques include closed or quasi-closed microchambers with optical oxygen sensors based on phosphorescence quenching or electrochemical sensors, integrated into microplates, microfluidic chips, or microfabricated respirometers. The measurements yield oxygen concentration changes over time, from which OCR is calculated. Some approaches combine with fluorescence or luminescence reporters.

Applications include microbial respiration assays, plant root or seed respiration, isolated mitochondria or permeabilized cells, and pharmacological testing of metabolic inhibitors. Microrespirometry allows high sensitivity, low sample consumption, and real-time monitoring, enabling assessment of metabolic responses to temperature, hypoxia, nutrients, or drugs.

Limitations include the need for careful calibration and temperature control; small volumes can yield rapid oxygen depletion and diffusion effects; sensor response times, baseline drift, and oxygen gradients within samples can affect accuracy; data interpretation must consider cell density and chamber geometry.

History notes that advances in oxygen micro-sensors and microfluidics in the 1990s and 2000s expanded the field beyond conventional respirometry, enabling measurements in picoliter to microliter volumes and single-cell experiments.