Plant-Growth Synchronized, Acid Phosphatase-Responsive Lignin-Based Controlled Release Phosphorus Nanofertilizers

Deploying agrochemicals as nanoparticle-based formulations not only provides opportunities to tune release kinetics, prevent premature degradation, increase shelf life, and reduce loss of active ingredient but also can enable the design of systems that can interact with or respond to soil and/or plants in a specific manner, which provides further opportunities to refine the delivery of agrochemicals. This article presents tripolyphosphate (TPP)-cross-linked lignin-based nanofertilizers that are designed to disintegrate and release phosphorus upon exposure to acid phosphatase, which is an enzyme that is upregulated as part of the phosphate starvation response of plants. In model experiments, it was shown that phosphorus release from the lignin-TPP nanoparticles was triggered by acid phosphatase, dependent on the enzymatic activity, and accompanied by the simultaneous disintegration of the nanoparticles. Experiments with the model plant Arabidopsis thaliana showed that lignin-TPP nanoparticles are an efficient phosphorus source for plants, suppressing the typical growth inhibition and activation of the molecular mechanisms triggered by phosphate deficiency. These experiments underline the potential of lignin-TPP nanoparticles in providing readily accessible phosphate for plants during growth and development, which represents a step forward toward nanofertilizers that are able to release their payload on demand in a plant-growth-synchronized manner.