Tilapia Bone-Derived Hydroxyapatite Particles for Controlled Citronella ( <i>Cymbopogon nardus</i> ) Release and Antimicrobial Activity

This study investigated the use of nanostructured hydroxyapatite (HA) derived from tilapia (<i>Oreochromis niloticus</i>) bones to produce particles for encapsulating citronella essential oil within a sodium alginate matrix, aimed at antimicrobial applications. Particles were obtained by emulsifying sodium alginate, citronella essential oil, and HA in different proportions, followed by dripping the emulsion into a CaCl₂ solution. Rheological properties were characterized by rotational rheometry to assess emulsion stability, thixotropy, and viscosity. All emulsions exhibited pseudoplastic and thixotropic behavior, with viscosity decreasing as HA concentration increased. While higher HA content improved emulsion stability, it reduced thixotropy, resulting in lower encapsulation efficiency. Release kinetics indicated that the formulation with intermediate HA content enabled more controlled essential oil release. In antimicrobial assays, this formulation achieved the highest activity against <i>Escherichia coli</i>, with an inhibition halo of 34 ± 3 mm. The results propose a sustainable strategy for enhancing controlled release and antimicrobial performance of encapsulated agents, employing biocompatible materials derived from animal waste, with potential applications in biomedicine, food preservation, and environmental protection.