Silymarin-functionalized nanohydroxyapatite-chitosan nanocomposite: a promising biomaterial for oral health applications.

Background: Nanohydroxyapatite (nHAP) is widely recognized for its potential biomedical applications, particularly in bone regeneration and periodontal therapy. Green synthesis methods, which are eco-friendly and non-toxic, have gained attention for the production of nanocomposites. Silymarin, a bioactive compound, can serve as both a reducing and stabilizing agent in such synthetic processes. In this study, we aimed to develop a nanohydroxyapatite nanocomposite using silymarin (SL) and chitosan (CH) and evaluate its antioxidant, antibacterial, and anti-inflammatory properties for oral health applications.

Methods: Nanohydroxyapatite nanocomposites were synthesized using a green synthesis technique, with silymarin acting as both reducing and stabilizing agent. Chitosan was incorporated to form the polymer-based nanocomposites. The synthesized materials (silymarin-chitosan, silymarin-nHAP, and nanocomposite) were characterized by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FTIR) to assess their morphology and functional groups. Antioxidant activity was evaluated using the DPPH assay, and the antibacterial activity was tested against common oral pathogens. Biocompatibility was assessed using human gingival fibroblast (HGF) cells and cell viability was measured via live/dead cell assays using fluorescence imaging and in vitro migration assays. Wettability analysis was performed using a contact angle measurement technique to evaluate the surface hydrophilicity of the nanocomposite, a crucial factor for biointegration and tissue adhesion. Additionally, the anti-inflammatory potential was examined using the human red blood cell (HRBC) membrane stabilization assay, where the nanocomposite was evaluated for its ability to inhibit heat-induced hemolysis.

Results: The characterization revealed the successful formation of nanoHA nanocomposites with distinct morphological features. Antioxidant assays indicated significant free radical scavenging activity, whereas antibacterial testing demonstrated effective inhibition of oral pathogens, including Streptococcus mutans and Porphyromonas gingivalis. Wettability analysis revealed a favorable contact angle, indicating enhanced surface hydrophilicity, which is beneficial for cell attachment and biointegration. Biocompatibility studies revealed that the nanocomposites exhibited minimal cytotoxicity and enhanced cell viability. Migration assays revealed favorable activity in promoting fibroblast migration, suggesting its potential for tissue regeneration. Furthermore, the HRBC membrane stabilization assay confirmed the anti-inflammatory potential of the nanocomposite, indicating its ability to protect erythrocytes against heat-induced hemolysis.

Conclusion: The silymarin-chitosan-nanohydroxyapatite nanocomposite synthesized using green methods demonstrated high crystallinity, improved wettability, excellent biocompatibility, and multifunctional bioactivity, including antioxidant, antibacterial, and anti-inflammatory effects. The ability of the nanocomposite to support cell migration, inhibit oral pathogens, enhance surface hydrophilicity, and stabilize cell membranes suggests its potential application in oral health, particularly in bone regeneration, periodontal therapy, and inflammation management.