Lignin-based microcarriers for controlled fungicide release

The excessive and inefficient use of agrochemicals generates severe environmental and health concerns, urging the development of sustainable delivery systems. Herein, we report the encapsulation of the fungicide difenoconazole within kraft lignin microcarriers prepared by spray drying. The process yielded spherical particles ranging from 1 to 10 μm, with high encapsulation efficiency. Structural analysis by Fourier transform infrared (FTIR) spectroscopy evidenced chemical interactions between lignin and difenoconazole, confirming the incorporation of the fungicide into the polymer structure. Release studies under different pH conditions revealed a biphasic profile, characterized by an initial burst followed by a slower, sustained release, with strong pH dependence. Kinetic modeling using singular value decomposition (SVD) and a first-order model showed excellent correlation ( R > 0.99), suggesting that the release process is governed by the partial solubilization of lignin and the release of difenoconazole located in the outer regions of the microcarriers. Furthermore, in vivo phytotoxicity trials demonstrated that the developed microcarriers are highly biocompatible at lower doses; formulations at a concentration of 0.01% triggered a significant biostimulant response, as evidenced by an increased germination index (GI). Overall, our results demonstrate that a precise dosage configuration optimizes the safety profile of the encapsulated matrix, highlighting the potential of these lignin-based microcarriers as a scalable and eco-friendly platform for controlled fungicide delivery, capable of extending field persistence, reducing application frequency, and mitigating environmental impact.