Lignin increases stability and effectiveness of herbicide nanoparticles, study finds

A recent study showed that a fraction obtained from lignin, an organic polymer responsible for the rigidity of plant cell walls, was able to improve the performance of nanoparticles with the herbicide.

The work is published in the journal ACS Sustainable Chemistry and Engineering and was recently featured on its cover.

The study was conducted by researchers from three research institutes in the state of São Paulo, Brazil: the State University of São Paulo (UNESP), the State University of Campinas (UNICAMP), and the Federal University of São Carlos (UFSCar).

“Lignin has antioxidant properties and is one of the main components of plant biomass, but it is still underutilized and often treated as a waste from the pulp and paper industry. This is why our group looked for more sustainable ways to add value to this abundant and renewable material,” explains Leonardo Fraceto, professor at the UNESP Institute of Science and Technology, Sorocaba campus.

The substance was obtained from Eucalyptus urograndis, a deciduous tree, and then put through a green process. This process used acetic acid as a solvent to obtain different fractions with distinct structural and chemical properties. Next, nanoparticles were produced from atrazine, a herbicide that fights weeds.

These nanoparticles underwent a series of physical, chemical and thermal analyzes to examine their structure and behavior.

“We found that different lignin fractions have very distinct properties. Some are richer in phenolic groups. Others have a higher molar mass or promote greater thermal stability. These differences have a direct impact on the formation and performance of the nanoparticles,” explains Fraceto.

Some fractions are more effective in protecting polymeric materials (e.g. composed of macromolecules, proteins, and cellulose) from UV-induced degradation, while others act as stabilizers in substance delivery systems. These results demonstrate that lignin is not a single, uniform waste, but rather a material that can be customized for different applications.

According to Fraceto, this discovery is significant because although the use of lignin as a surfactant holds promise for the efficient delivery of active ingredients in agrochemical formulations, several challenges must be overcome. A major problem is the variability of its structure, which can affect its consistency and performance as a stabilizing agent.

In the case of atrazine nanoparticles, the use of the lignin moiety increased the stability and efficiency of herbicide release. The use of specific lignin moieties was crucial to optimize the performance of the nanoparticles. The developed formulations effectively control blackjack (Bidens pilosa L.) and green amaranth (Amaranthus viridis L.), demonstrating their potential for sustainable control of agricultural pests.

“Not only were we able to use a simple and environmentally friendly process, but we also took advantage of a byproduct that is abundant in Brazil, opening up possibilities for the bioeconomy,” says Fraceto. “This type of study connects materials science, sustainability and technological innovation, bringing academia closer to solutions to current challenges, such as the development of greener agricultural inputs.”