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.

To develop multifunctional hydrogels possessing excellent biocompatibility, antibacterial activity, and antioxidant property, as well as suitable adhesion and degradability, we innovatively modified chitosan (CS) by using hydrotropic acid (HA) for obtaining HA-modified CS (CSHA) in this work. FTIR and UV-Vis results showed that CSHA with a grafting degree of 26.64% was successfully synthesized via the amide reaction. Compared to that of CS, the crystallinity of CSHA decreased and its solubility was improved. Simultaneously, oxidized glucomannan (OGM) with an oxidation degree of 24.07% was acquired through the periodate oxidation method. Based on the above outcomes, four kinds of CSHA/OGM hydrogels (CH-OG-HGs) were successfully constructed via the Schiff base reaction, and their physicochemical and biological properties were studied. Experimental results revealed that CH-OG-HGs had a short period of gelation time (< 70 s), a maximum equilibrium swelling rate of 17.54%, a maximum adhesion strength of 1400 kPa, and a high degradation rate (> 99.39%) within 30 days. Rheological test results showed that CH-OG-HGs had shear thinning characteristics, self-healing property, and appropriate mechanical strength. SEM results indicated that CH-OG-HGs possessed interconnected three-dimensional network structures. CH-OG-HGs had much low cytotoxicity to L929 and HSF cells, and their hemolysis rates were less than 5%, which is in accord with the standards of biomedical materials. Furthermore, CH-OG-HGs exhibited a remarkable inhibition rate (up to 95.94%) against both E. coli and S. aureus, and different radical scavenging ratios of around 90% for ABTS⁺· and 40% for ·OH. In summary, CH-OG-HGs not only possessed suitable mechanical strength, adhesive strength, swelling property, and low toxicity, but also had excellent antibacterial, antioxidant, injectable, degradable, and self-recovery properties, which collectively highlights their enormous potential for application in various biomedical fields such as wound dressings, drug release carriers, and tissue engineering materials.