# A Reaction‐Diffusion Frame for Accessing Metabolic O2 Fluxes in Single Microalgal Cells with Low‐Cost Wide‐Field Imaging of Nanosensor Luminescence Lifetime

## TL;DR

This paper introduces a low-cost method to measure oxygen fluxes in single microalgal cells using imaging and reaction-diffusion modeling.

## Contribution

A new wide-field imaging protocol is developed to access metabolic O2 fluxes at the single-cell level.

## Key findings

- The method reveals spatial distributions of O2 concentration around microalgal cells.
- Photosynthesis and respiration balances show angular dependencies and magnitude variations.
- The approach is validated for characterizing metabolic fluxes of membrane-permeant molecules.

## Abstract

In cells, many small molecules are membrane‐permeant. This feature opens a road to analyze their flux of production or consumption by quantitatively interpreting the map of their extracellular concentration within a reaction‐diffusion frame. Here, this approach is implemented with a new wide‐field lifetime imaging protocol applied to single microalgae cells sparsely deposited on an agarose pad loaded with a luminescent dioxygen (O2) nanosensor. The resulting maps are processed to access the spatial distribution of the O2 concentration in the plane of the cells. After fitting the data, the cellular O2 flux is extracted, evidencing a span of magnitudes and angular dependencies in the balance between photosynthesis and respiration. Beyond pointing to the disparity of individual behavior within the same colony, this work validates a simple approach for characterizing metabolic fluxes of membrane‐permeant molecules down to the single‐cell level.

Individual Chlamydomonas reinhardtii (C. reinhardtii) living cells on an agarose pad containing luminescent O2 nanosensors are imaged with a simple wide‐field protocol of lifetime imaging. The resulting maps of phosphorescence lifetime are analyzed within a reaction‐diffusion frame to access the distribution of metabolic O2 fluxes generated by single microalga cells.