Preparation of Lignin/Poly(Lactic Acid) Composite Microspheres as Potential Carriers for Biopesticides Delivery

Polymer blending is a straightforward physical modification technique capable of providing materials with useful properties compared with single polymer equivalents. The main aim of this work is to study the preparation of composite poly(lactic acid)(PLA)/lignin microparticles by a solvent evaporation method. Microparticles with different biopolymers composition were characterized by SEM, FTIR, and DSC techniques to determine their particle size, morphology, chemical structure, and thermal properties. In addition, their potential application for azadirachtin (AZD) encapsulation and protection against photodegradation was investigated. The encapsulation efficiency for PLA/lignin microparticles with a 55:45 ratio was 23.25%, indicating that a higher lignin content improved the biopesticide encapsulation efficiency. The release assays of AZD in water revealed a lower release rate for the formulation containing a higher PLA content. In addition, the photodegradation of AZD was more noticeable for the free compound in comparison with microparticle formulations. The results show that the biopolymer blend represents a promising alternative for microparticle preparation to encapsulate and protect AZD against degradation. Graphical Abstract