Self-Healing Hydrogels Fabricated by Introducing Antibacterial Long-Chain Alkyl Quaternary Ammonium Salt into Marine-Derived Polysaccharides for Wound Healing

Abstract

The development of hydrogels as wound dressings has gained considerable attention due to their promising ability to promote wound healing. However, in many cases of clinical relevance, repeated bacterial infection, which might obstruct wound healing, usually occurs due to the lack of antibacterial properties of these hydrogels. In this study, we fabricated a new class of self-healing hydrogel with enhanced antibacterial properties based on dodecyl quaternary ammonium salt (Q12)-modified carboxymethyl chitosan (Q12-CMC), aldehyde group- modified sodium alginate (ASA), Fe³⁺ via Schiff bases and coordination bonds (QAF hydrogels). The dynamic Schiff bases and coordination interactions conferred excellent self-healing abilities to the hydrogels, while the incorporation of dodecyl quaternary ammonium salt gave the hydrogels superior antibacterial properties. Additionally, the hydrogels displayed ideal hemocompatibility and cytocompatibility, crucial for wound healing. Our full-thickness skin wound studies demonstrated that QAF hydrogels could result in rapid wound healing with reduced inflammatory response, increased collagen disposition and improved vascularization. We anticipate that the proposed hydrogels, possessing both antibacterial and self-healing properties, will emerge as a highly desirable material for skin wound repair.

Keywords: antibacterial; double cross-linked; self-healing hydrogels; wound healing.

Figure 1

Schematic illustration of the preparation and application of QAF hydrogels.

Figure 2

Preparation and structural characterizations of hydrogels. (A,B) Route of synthesis of ASA, Q12 and Q12-CMC; (C) 1H NMR spectrum of CMC and Q12-CMC (The dotted box indicates the NMR peak corresponding to the dodecyl quaternary ammonium salt); (D) 1H NMR spectrum of SA and ASA (The dotted box indicates the NMR peak corresponding to the aldehyde group); (E,F) FTIR spectra of SA, ASA, CMC, Q12-CMC and QAF hydrogels.

Figure 3

(A) SEM images, (B) rheological properties and (C) uptake ratios (n = 3) of QAF hydrogels and CAF hydrogels. * p < 0.05.

Figure 4

Self-healing abilities of the QAF hydrogels. (A) Macroscopic self-healing tests; (B) Strain amplitude sweep measurements (γ = 1–500%); (C) Alternate step strain sweep measurements with small strain (γ = 1%) to large strain (γ = 200%) with 120 s for every interval.

Figure 5

Antibacterial properties of hydrogels. (A) The counter board pictures of S. aureus and E. coli growth on QAF and CAF hydrogels; (B) Antibacterial rates of QAF and CAF hydrogels (n = 3); (C) FDA/PI fluorescence staining images of S. aureus and E. coli cultured with extracts of QAF and CAF hydrogels for 12 h. (D) SEM images of S. aureus and E. coli after contact with QAF hydrogels for 12 h.

Figure 6

In vitro hemocompatibility evaluation. (A) Cell viabilities of L929 fibroblast cells (n = 3); (B) Hemolysis performances of hydrogels (n = 3); (C) The BCI values of whole blood clotting evaluation (n = 3); (D) Hemostatic performances of QAF hydrogels in mouse liver hemorrhage model (The control mouse received no treatment, n = 3). ns > 0.05, * p < 0.05, **** p < 0.0001.

Figure 7

(A) Images of the wound healing sites on days 0, 3, 7, 10 and 14; (B) Traces of wound-bed closure on days 0, 3, 7, 10 and 14. (C) Quantitative analysis of wound healing rates according to Figure 7 (A) (n = 3).

Figure 8

(A) HE staining of wound sections at day 14; (B) Masson’s staining of wound sections at day 14; (C) Immunofluorescence staining of CD31 structures at day 7.