pH-Responsive Controlled Release of the Fungicide Hexaconazole From Chitosan Nanoparticles

The continued reliance on chemical fungicides such as hexaconazole raises concerns regarding solubility, persistence, and resistance, highlighting the need for safer delivery systems. In this study, chitosan-hexaconazole nanoparticles (CHEN) were developed as a nanocarrier-based fungicide delivery system and evaluated at a tenfold production scale. A modified ionic gelation method that eliminated centrifugation achieved a yield of 83.10% compared with 76.0% in earlier work, while maintaining loading content at 15.44%. Dynamic light scattering confirmed a unimodal particle size of 28.2 nm, with Fourier transform infrared spectroscopy, thermogravimetric, and X-ray fluorescence analyses verifying reproducibility and elemental composition. Brunauer-emmett-teller (BET) analysis revealed a type IV mesoporous structure (26.01 m²/g surface area, 30.91 nm pore diameter), supporting controlled release. In vitro studies showed biphasic, pH-responsive release best fitted to the pseudo-second-order model. Cumulative release was highest at pH 4 (70.20%) and pH 9 (73.10%) but limited at pH 7 (45.98%). Korsmeyer-Peppas modeling indicated Fickian diffusion at pH 7 (n = 0.308), while non-Fickian transport dominated at pH 4 (n = 0.659) and pH 9 (n = 0.625). Colloidal stability was maintained for 6 months before aggregation reduced release predictability. Overall, CHEN demonstrates scalability, pH-responsive behavior, and sustained release potential, making it a strong candidate for sustainable fungicide delivery.