Introduction: The present work reports the production and characterization of chitosan microspheres (QUI) and chitosan/palygorskite hybrid microspheres (QUI/Pal) and investigates their performance for the controlled delivery of the biostimulants glycine (Gly) and glutamic acid (Glu) and their potential application in plants. Methods: Three groups of microspheres were obtained using the water-in-oil emulsion method and characterized by Scanning Electron Microscopy (SEM), swelling degree (H), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The captured amino acids were quantified by UV-Visible spectrophotometry, and their potential biological activity was assessed. Results: The incorporation of palygorskite into hybrid microspheres (QUI/Pal) significantly improved amino acid capture efficiency and modulated delivery kinetics, resulting in slower and more gradual release profiles compared to QUI microspheres. Discussion: Mathematical modeling revealed a two-stage diffusion process: an initial Fickian phase followed by a non-Fickian phase associated with polymer matrix relaxation. Biological studies demonstrated that QUI/Pal microspheres loaded with amino acids did not generate adverse toxic effects in plants. Conclusion: Biological assays with Capsicum chinense (habanero pepper) showed that QUI/Pal microspheres improved germination percentage, biomass production, and root elongation in a dose-dependent manner. These results confirm the potential of QUI/Pal microspheres as effective systems for the controlled delivery of biostimulants in agricultural applications.
Torres-López et al. (Mon,) studied this question.