Electrosprayed Alginate-Fmoc Amino Acid Microcapsules for Quercetin Loading and Release

This study presents the development of hybrid microcapsules for the loading and release of quercetin, produced by incorporation of Fmoc-Tyrosine (Fmoc-Y) or Fmoc-Proline (Fmoc-Pro) into alginate, followed by Ca²⁺-ion-mediated cross-linking. The microcapsules produced using this method were characterized in terms of particle size, morphology, chemical structure (FTIR), release behavior, and swelling properties. An average diameter of microcapsules loaded with quercetin was measured at 187 ± 19 μm for Ca-Alginate, 154 ± 14 μm for Ca-Alginate/Fmoc-Y, and 131 ± 15 μm for Ca-Alginate/Fmoc-Pro. The inclusion of Fmoc-Pro or Fmoc-Y in the Ca-Alginate structure was shown by changes and shifts in the peak in FTIR. Rheological analyses revealed the flow behavior, viscoelastic properties, and shear-induced structural stability of alginate solutions used in microcapsule production. The incorporation of Fmoc-aa into alginate was intended to enhance the structural durability of the alginate matrix and thereby improve its drug release performance. Consistent with this expectation, examination of quercetin release at pH = 7.4 revealed that release from Ca-Alginate microcapsules was completed within 7 h, whereas release from the hybrid microcapsules extended to 24 h. Moreover, the zero-order model for Ca-Alginate microcapsules and the Korsmeyer-Peppas model for hybrid microcapsules were determined as the most appropriate mathematical models. The swelling behavior of the microcapsules was investigated at pH = 1.2 and 7.4. Although shrinkage occurred in the microcapsules at pH = 1.2, the spherical form was maintained in the first 7 h in hybrid and nonhybrid microcapsules. At pH = 7.4, it was observed that Ca-Alginate microcapsules were largely eroded approximately at the 6^th hour, while hybrid Ca-Alginate/Fmoc-Y and Ca-Alginate/Fmoc-Pro microcapsules maintained their spherical form up to 16 h. These findings are supported by SEM analyses showing that hybrid microcapsules exhibit a more compact and less porous surface morphology compared to pure Ca-Alginate microcapsules.