Polyethylenimine Based Nanoparticles for Enhancing Photosynthesis in Plants

During photosynthesis, plants use light energy to transform carbon dioxide and water into carbohydrates for their own growth. The photosynthetic process comprises many steps that can in principle be optimized to have higher efficiency. RuBisCO (Ribulose 1,5-bisphosphate carboxylase/oxygenase) catalyzes the carboxylation reaction that is the initial reaction for carbon fixation and conversion of CO₂ to sugars. The reaction occurs in organelles called chloroplasts present in leaf cells. However, RuBisCO has naturally a poor affinity for CO₂ and the transfer of the atmospheric CO₂ to the RuBisCO enzyme is highly limited by the diffusion of CO₂ through the stomata and the intercellular space which ultimately considerably reduces the photosynthesis rate. Polyamines have been shown in-vitro to be able to transfer carbon dioxide to RuBisCO for the carboxylation reaction. In this work, we present biocompatible fluorescent polyethylenimine nanoparticles for enhancing the CO₂ transfer to the RuBisCO enzyme. With <i>in</i> <i>vitro</i> and <i>in vivo</i> studies, we evaluated the nanoparticles uptake of atmospheric CO₂ and transfer kinetics to RuBisCO for the carboxylation reaction. Then, we introduced the nanoparticles into the plant apoplast via localized infiltration. First, we studied the toxicity of the nanoparticles and results showed no evidence of a direct harmful impact. We then investigated their distribution within the plant leaf with confocal microscopy and showed that the nanoparticles not only are present in the intercellular space but also in the direct centers of photosynthetic activity: the chloroplasts, which indicate the possibility of a pathway to increase the diffusion of CO₂ in the plant tissue.