Preparation and Characterization of Nanoparticles Based on Silybin-Modified Chitosan and Evaluation of Their Antiseptic Effects

To develop multifunctional nanomaterials integrating superior biocompatibility, antioxidant capacity, and antibacterial activity, this study represents the first attempt to graft silybin (SLB) onto the molecular backbone of chitosan (CS). Three types of modified CS (CS-SLB) with varying grafting degrees (6.04%, 6.46%, and 7.47%) were synthesized, and SLB-modified CS nanoparticles (CS-SLB NPs) were subsequently prepared using the ionic gelation method. Spectroscopic analyses, including Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible(UV-Vis), and X-ray diffraction(XRD), were used to confirm the successful synthesis of CS-SLB, which demonstrated decreased crystallinity and improved solubility compared with pristine CS. Dynamic light scattering and transmission electron microscopy results revealed that the newly prepared CS-SLB NPs possessed a spheroidal morphology with a uniform particle-size distribution ranging from 150 to 350 nm and that their zeta potential decreased from +32.06 mV (for CS NPs) to a range of +14.01 to +20.70 mV (for CS-SLB NPs). Antioxidant and antibacterial tests demonstrated scavenging rates of CS-SLB NPs of 99.51% and 99.70% against DPPH· and ABTS·⁺ free radicals, respectively, significantly exceeding those of CS NPs (25.12% and 36.43%, respectively). Moreover, the minimum inhibitory concentrations of CS-SLB NPs against both Escherichia coli and Staphylococcus epidermidis were 188 μg/mL, indicating superior antibacterial activity to that of CS NPs (375 μg/mL). Biological safety evaluations revealed hemolysis rates of CS-SLB NPs is less than 5%, and these nanoparticles exhibited low cytotoxicity toward HSF and L929 cells, in compliance with the Chinese national standard (GB/T 16886.5—2017) for the biological evaluation of medical devices. To determine the practical application potential of the newly fabricated nanoparticles, CS-SLB NPs were added as a preservative to a facial mask essence. At 752 μg/mL, their inhibitory effects against four bacterial strains were superior to those of the positive control, and excellent inhibition of Candida albicans was also observed. Overall, CS-SLB NPs possessed favorable antioxidant and antibacterial activities, along with biocompatibility, indicating their great potential as an alternative to traditional chemical preservatives in cosmetic preservation.