Ionic gelation synthesis and characterization of Chitosan nanoparticles from Sepia aculeata cuttlebone and their in-vitro antimicrobial activity against oral pathogens

The current study focuses on the production of chitosan nanoparticles from the internal bone of the cuttlefish Sepia aculeata, with a specific emphasis on their antimicrobial capabilities against dental infections. The extract was found to be rich in carbohydrates, indicating the existence of acidic polysaccharides, a key indicator of chitosan precursors. Chitosan nanoparticles were manufactured employing both physical and chemical modifications to achieve high nanoparticle production. The samples’ structural and chemical characteristics were characterized using FTIR, FESEM, and XRD techniques. The FTIR investigation confirmed the functional groups of chitosan, revealing significant peaks between 3429 cm⁻¹ and 646 cm⁻¹, indicating strong intermolecular interaction. FESEM imaging revealed nanoparticles ranging in size from 0.120 to 0.2734 microns, with mostly spherical shapes and erratic manufacturing patterns. The XRD analysis revealed seven distinct peaks, with the most significant peak at 30°, confirming the amorphous nature of the nanoparticles. The antimicrobial activity of chitosan nanoparticles was investigated against Streptococcus mutans, Pseudomonas aeruginosa, Escherichia coli, and Candida tropicalis using the well diffusion method. At the highest tested dosage, inhibition zones for S. mutans and P. aeruginosa were 20 ± 1.53 mm and 15 ± 0.83 mm, respectively, demonstrating significant antibacterial efficacy. E. coli showed an inhibition zone of 14 ± 0.58 mm, but C. tropicalis was less sensitive. Microbial viability was reduced concentration-dependently, with significant differences (P < 0.05) between tested doses. The results demonstrate that Sepia aculeata-derived chitosan nanoparticles exhibit broad-spectrum antibacterial activity, suggesting a potential role in controlling dental infections and biomedical applications.