A chitosan-based antibacterial hydrogel with injectable and self-healing capabilities

Abstract

The presence of bacteria directly affects wound healing. Chitosan-based hydrogel biomaterials are a solution as they offer advantages for wound-healing applications due to their strong antimicrobial properties. Here, a double-cross-linking chitosan-based hydrogel with antibacterial, self-healing, and injectable properties is reported. Thiolated chitosan was successfully prepared, and the thiolated chitosan molecules were cross-linked by Ag-S coordination to form a supramolecular hydrogel. Subsequently, the amine groups in the thiolated chitosan covalently cross-linked with genipin to further promote hydrogel formation. In vitro experimental results indicate that hydrogel can release Ag⁺ over an extended time, achieving an antibacterial rate of over 99% against Escherichia coli and Staphylococcus aureus. Due to the reversible and dynamic feature of Ag-S coordination, an antibacterial hydrogel exhibited injectable and self-healing capabilities. Additionally, the hydrogel showed excellent biocompatibility and biodegradability.

Supplementary information: The online version contains supplementary material available at 10.1007/s42995-023-00211-z.

Keywords: Antibacterial; Chitosan; Cross-linking; Hydrogel; Silver ion.

Fig. 1

A Synthesis of CS-NAC; B FT-IR spectra of CS-NAC and chitosan; C ¹H NMR spectra of CS-NAC and chitosan; and D schematic architecture of CS-NAC/Ag⁺/GP hydrogels

Fig. 2

Characterization of CS-NAC/Ag⁺/GP hydrogels with different Ag⁺ and genipin concentrations. A FT-IR spectra, B XPS patterns, C XPS S2p spectra, D porosity, and E SEM images of the hydrogels (n = 3, mean ± SD, *P < 0.05 and **P < 0.01)

Fig. 3

A Frequency sweeps (G′ and G″) of the CS-NAC/Ag⁺/GP hydrogels with different Ag⁺ concentrations (1 mm gap, n = 3, mean ± SD); B frequency sweeps of the hydrogels with various concentrations of genipin (n = 3, mean ± SD); C the compressive stress–strain curves of the hydrogels with different concentrations of Ag⁺ and genipin; D photographs of healing processes and compressive stress–strain curves of before and after wound healing; and E swelling ratio of the CS-NAC/Ag⁺/GP hydrogels (n = 3, mean ± SD)

Fig. 4

In vitro antibacterial activity of the hydrogels cross-linked with various Ag⁺ or genipin concentrations against E. coli and S. aureus. A and C Photographs of agar plates and B and D corresponding statistical data of the colonies of E. coli and S. aureus. (n = 6, mean ± SD, *P < 0.05 and **P < 0.01). E SEM images showing the morphological changes of E. coli and S. aureus after incubation of the CS-NAC/Ag⁺-1.00/GP-0.05 hydrogel

Fig. 5

A Cumulative release profiles of Ag⁺ from the CS-NAC/Ag⁺-1.00/GP-0.05 hydrogel (n = 3, mean ± SD). B Degradation behavior of the hydrogels with different Ag⁺ concentrations (n = 4, mean ± SD). C Degradation behavior of the hydrogels with various concentrations of GP. D Photographs of the degraded hydrogels

Fig. 6

Biocompatibility analysis. A, B Cell viability of fibroblast cells cultured in the hydrogel-conditioned media. C Live/dead staining fluorescent images (n = 4, mean ± SD, *P < 0.05 and **P < 0.01)