Nanoparticles reshape photosynthetic plant-cell cultures across repeated treatments

Plant cells can multiply, photosynthesize and construct their own cell walls. In an unreviewed bioRxiv preprint, Cyril Routier, Denise Pagliara and colleagues investigate how those activities change when growing cell cultures repeatedly receive CO2-concentrating nanoparticles. They report progressively more cohesive cell clusters alongside changes in chlorophyll, photosynthetic measurements and wall architecture.

Repeated treatment, changing cells

The study combines photosynthetically active Arabidopsis thaliana suspension cells with chitosan-modified polyethyleneimine nanoparticles, abbreviated gPEI–Chi. The authors describe these particles as a synthetic material capable of reversibly capturing inorganic carbon. Their preprint, posted on November 3, 2026, has not been certified by peer review.

The cells were grown under continuous illumination in a medium containing sucrose. This was a suspension-culture experiment, not a study of whole plants or field crops. Its central question was how nanoparticle treatment interacts with a population that keeps dividing and being transferred into fresh medium.

Researchers supplied fresh nanoparticles at each weekly subculture. They labelled the initial treatment Gen0, and cultures maintained through three and six successive weekly subcultures Gen3 and Gen6. These labels track repeated culture transfers and treatment, rather than generations of whole plants.

According to the authors, fluorescently labelled particles initially associated with cell surfaces and subsequently accumulated inside cells. Initial treatment produced no detectable increase in cell death in their staining assay and did not substantially alter culture growth kinetics, although dry biomass changed transiently.

Across repeated treatments, the cultures developed denser, more cohesive clusters. Microscopy also showed changes in chloroplast organization, including more organized internal membranes in Gen6.

Less CO2 above the culture is not a photosynthesis measurement

The researchers monitored CO2 in the headspace—the gas above the liquid—in sealed culture flasks using a closed-loop measurement system. Untreated cultures reached approximately 1,500 parts per million before concentrations declined. Treated cultures remained at or below approximately 750 parts per million, with peak timing varying between treatment stages.

Those readings establish lower net headspace CO2 accumulation under the experimental conditions. They do not, by themselves, identify how much carbon the cells fixed through photosynthesis.

The authors explicitly identify several possible contributors: changes in cellular respiration or CO2 consumption, carbon retention by the nanoparticles, or a combination. Particle suspensions without cells also captured CO2 in their experiment. Consequently, the headspace result should not be presented as a direct measurement of increased photosynthesis or reduced respiration.

The team also measured medium pH, but cautions that nutrient, ion and metabolite exchange influence it. They therefore do not treat pH as a direct proxy for CO2 assimilation.

More chlorophyll, but a stage-dependent response

Separate measurements examined chlorophyll and the photosynthetic apparatus. After one week of culture, Gen3 and Gen6 contained approximately 120% and 160% more chlorophyll, respectively, than age-matched untreated controls, the authors report.

Chlorophyll abundance was not the same thing as uniformly improved photosynthetic performance. Fluorescence measurements assessed photosystem II function and were used to estimate photosynthetic electron transport. Initial nanoparticle treatment reduced several performance measures. Gen3 subsequently showed higher maximum electron transport capacity and less inhibition under high light than controls. Gen6 combined sustained maximum electron transport with recovery toward control-like photosystem II efficiency and low-light performance.

The authors note that these measurements used aggregated cultures, whose structure may modify light exposure within the population. Their electron transport estimates also used an approximate light-absorption factor.

Protein measurements supported a selective reorganization rather than a general increase in photosynthesis. Several photosystem II proteins remained below control levels, while proteins associated with carbon metabolism and energy production changed across treatment stages.

Cell walls changed alongside physiology

The researchers also examined how cells rebuilt their walls after enzymatic digestion. Gen3 and Gen6 showed slower, altered wall-regeneration dynamics, without significant differences in viability from controls at individual measurement times. These cultures also retained more wall-associated fluorescence immediately after digestion, which the authors interpret as consistent with less efficient digestion of aggregated cells.

Analysis of mature walls revealed changes in sugar composition and broader pectin- and cellulose-associated fluorescent regions where cells contacted one another. Electron microscopy showed increasingly granular wall ultrastructure. This was not simply an increase in total cellulose: the authors report no major increase in its overall amount.

They interpret the combined wall measurements as a structural basis for the cultures’ greater cohesiveness. More broadly, they propose repeated nanoparticle treatment as an approach for developing plant biohybrids and engineered living materials. The reported findings concern evolving laboratory cell populations, not demonstrated improvements in crop yields or field carbon capture.