Multifunctional Chitosan-Coated Alginate Microspheres Loaded with Spirulina, Hydroxyapatite, and Metronidazole for Sustainable Periodontitis Treatment

Chitosan-coated alginate microspheres (M0, M1, M2.5, and M5) loaded with spirulina extract, hydroxyapatite, and metronidazole were developed for periodontitis treatment. Fabricated via ionotropic gelation, these formulations were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Their swelling kinetics and biodegradation rate indicated suitability for periodontitis treatment. The M5 formulation demonstrated superior drug loading (73.3 mg/g) and sustained release profiles, achieving 99.67% cumulative metronidazole release over 72 h. Korsmeyer-Peppas modeling revealed non-Fickian release mechanisms (n = 0.48–0.66) for all drug-loaded samples (M1, M2.5, M5), governed by diffusion, polymer swelling, and erosion. All formulations exhibited excellent antibacterial activity against Staphylococcus aureus and Escherichia coli. The microspheres showed 50–60% scavenging activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, demonstrating their potential to suppress intracellular reactive oxygen species (ROS) production. They also displayed excellent hemocompatibility (< 3% hemolysis) and enhanced NIH3T3 fibroblast viability. In wound healing assays, the M5 formulation promoted 80% wound closure within 24 h, significantly outperforming both control and M0 samples. At the molecular level, prepared microspheres upregulated vascular endothelial growth factor (VEGF) expression by up to 6-fold while suppressing tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β) by 60–70%, demonstrating combined angiogenic and anti-inflammatory effects. In conclusion, the M5 formulation emerged as particularly promising, combining optimal drug loading, sustained release, and multifunctional therapeutic effects. Thisstudy represents a significant advancement in localized periodontitis therapy, addressing infection control while promoting tissue regeneration through their unique composition of spirulina, hydroxyapatite, and metronidazole.

Graphical Abstract