Preparation of apigenin-loaded microspheres and their effects against Porphyromonas gingivalis

Periodontal disease is a leading cause of tooth loss in adults, and current drug treatments are limited by issues such as drug resistance and short duration of action. This study aimed to prepare apigenin-loaded PLGA microspheres (AM) with sustained-release properties and evaluate their physicochemical characteristics as well as their antibacterial and anti-biofilm activities against Porphyromonas gingivalis, a key pathogen in periodontitis. AM were prepared using a solvent evaporation method and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and drug release studies. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration (MBEC) of AM against Porphyromonas gingivalis were determined. Biofilm disruption was visualized by confocal laser scanning microscopy (CLSM) and SEM, and the expression of virulence factor genes was analyzed by RT-qPCR. AM exhibited a regular spherical shape with an average particle size of 44.7 μm, a drug loading capacity of 10.43%, and an encapsulation efficiency of 78.22%. FTIR and XRD confirmed the successful encapsulation of apigenin, and the drug release profile demonstrated sustained-release characteristics. The MIC, MBC, MBIC, and MBEC of AM against Porphyromonas gingivalis were 3, 6.5, 4, and 7 mg/mL, respectively. CLSM and SEM revealed that AM disrupted biofilm integrity and caused damage to bacterial cell membranes. RT-qPCR showed significant downregulation of the virulence factor genes hagA, rgpA, and kgp (P < 0.05). This study successfully developed sustained-release apigenin-loaded PLGA microspheres (AM) that exert effective suppression of Porphyromonas gingivalis through combined antibacterial, anti-biofilm, and anti-virulence mechanisms.