Fe ₃ O ₄ –Chitosan Nanocomposite as a pH-Responsive Delivery System for Enhanced Delivery of <i>Punica Granatum</i> L. Polyphenols

<i>Punica granatum</i> extract (PG), consisting of punicalagin, ellagic acid, and gallic acid, was loaded onto an Fe₃O₄/Chitosan (Fe₃O₄@Chi) nanocomposite (Fe₃O₄@Chi-PG) to enhance pharmacokinetic properties. Fe₃O₄ was synthesized via the coprecipitation method and coupled with chitosan in 2% acetic acid solution via glutaraldehyde cross-linking. The presence of interested polyphenols in the pomegranate extract was confirmed by HPLC analysis, and the extract was post-loaded to the nanocarrier. XRD confirmed the crystallographic orientation of the nanocarrier, and SEM analysis confirmed the successful coupling of Fe₃O₄ onto the chitosan surface during the fabrication of Fe₃O₄@Chi. BET surface area analysis revealed the presence of micro- and mesopores in the synthesized materials. Significant reduction of the BET surface area and the pore volume of Fe₃O₄@Chi-PG compared to Fe₃O₄@Chi suggested the loading of the porous network and surface by PG. The presence of vibrational bands corresponding to the functional groups of the relevant bioactive compounds was confirmed via FT-IR analysis. The IC₅₀ values of the nanocomposite for DPPH and egg albumin denaturation assays were 18.69 and 257.69 μg/mL, respectively. The PG encapsulation efficiency of Fe₃O₄@Chi-PG was reported to be 86.44%. The pH-responsive release of the polyphenols was studied by fitting the release data into five kinetic models, including Korsemeyer-Peppas (KP) and Peppas-Sahlin (PS). The KP and PS models were selected to interpret the release mechanism based on the <i>R</i> ² ≥ 0.95 value. A combination of Fickian diffusion, relaxation, and swelling dominates the polyphenol release. Quasi-Fickian diffusion is responsible for the release in media with pH 1-6.7, whereas anomalous transport occurs at pH 7.4 (<i>n</i> = 0.46) according to the KP model. Polymer relaxation is the dominant mechanism for the release of bioactive compounds at pH 7.4, as exhibited by R/F > 1. However, the contribution of relaxation to the release of polyphenols at pH 2.5, 4, and 5.5 was negligible according to the parameters (<i>k</i> _R = 0). Characteristics of chitosan, including protonation and deprotonation of NH₂ groups, surface charge of Fe₃O₄, ionization of COOH and OH groups of the polyphenols, and molecular weight of the active compounds, contributed to the differences in the release behavior.