IG-13-1 peptide-loaded chitosan nanoparticles in dental adhesives: Physicomechanical, and biological performance

The aims of this study were to formulate a triethylene glycol dimethacrylate (TEGDMA)-based dental adhesive incorporating IG-13-1 peptide-coated chitosan nanoparticles (CNPs), and evaluate its polymerization, physicomechanical/bonding performance, antibacterial activity, and cytocompatibility.

Five samples were prepared (n = 5/group): commercial universal adhesive (Ruby Bond), experimental unfilled TEGDMA control, and experimental adhesives containing 1.5, 3, or 6 wt% IG-13-1-CNPs. Specimens were light-emitting diode (LED)-cured (1300 mW/cm²; 20 s/side). The degree of conversion (by Fourier transform infrared-attenuated total reflectance spectroscopy), depth of cure (ISO 4049), water sorption (baseline 21 days), flexural strength (ISO 4049), and shear bond strength to enamel (ISO 29022) were measured. Antibacterial testing against Streptococcus mutans was conducted using direct contact testing (optical density at 600 nm, OD₆₀₀) and disk diffusion. Cytocompatibility was assessed by using Alamar Blue.

All experimental adhesives had a high degree of conversion (>90%) but it decreased significantly (p < 0.001) with higher CNP loadings. The shear bond strength differed (p < 0.001) and decreased with higher loadings: 4.549 ± 0.698 MPa for commercial adhesive vs 2.080 ± 0.302 MPa for 6% loading. Antibacterial activity assessment against Streptococcus mutans using direct contact testing showed that peptide-coated CNPs reduced OD₆₀₀ from 1.6846 to 0.53275 (68.38%), whereas the reduction with uncoated CNPs was from 1.5267 to 1.196 (21.66%). Cell viability remained >85% across all treatments.

IG-13-1-CNP incorporation led to strong antibacterial activity while also maintaining a high degree of conversion and acceptable cytocompatibility. However, higher loadings compromised the cure depth and enamel bond strength, supporting the need to optimize the nanoparticle concentration/dispersion.