Synthesis and characterization of chitosan nanoparticle-based sustained release formulation for targeted delivery of the plant growth hormone indole-3-acetic acid

Nanoencapsulation of bioactive compounds within biopolymeric matrices has been at the forefront of modern agricultural interventions aimed at improving crop performance. One such biopolymer is chitosan, which has established its place in both agricultural and drug delivery fields. Among the bioactive compounds of interest, indole-3-acetic acid (IAA) is a crucial plant growth hormone that regulates diverse physiological processes and plays a vital role in crop growth and stress response. The present study involves the synthesis, characterization, and evaluation of chitosan nanoparticles (CNPs) loaded with IAA, combining the benefits of IAA as a key plant growth regulator and chitosan as a natural bio stimulant and controlled release carrier to improve efficiency and sustainability. The nanoparticles, both loaded with and without IAA were prepared using the ionotropic gelation technique, which utilizes the electrostatic interaction between cationic CNPs and anionic sodium tripolyphosphate (TPP) molecules. The CNP-IAA formulation exhibiting high loading and encapsulation efficiency (LE % and EE%) was selected for release and swelling studies under both acidic and alkaline conditions. The release profiles in both pH conditions showed a rapid initial increase in release within the first 24 h reaching, a maximum at 168 h. Further characterization using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), particle size analysis (PSA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the effective loading of IAA into the nanoparticles with the desired attributes needed for agricultural applications.