Carboxymethyl chitosan-grafted polyvinylpyrrolidone-iodine microspheres for promoting the healing of chronic wounds

Abstract

Chronic wounds that fail to heal are the most common complications experienced by diabetic patients, and current treatment remains unsatisfactory, mainly due to the vulnerability of diabetic wounds to bacterial infections. Chitosan derivatives are widely used to treat chronic wounds due to their excellent hydrophilicity, biodegradability, and antimicrobial activity and substantial contribution to tissue regeneration. However, the antimicrobial effect of chitosan is not sufficient due to the complicated pathological mechanism of diabetes mellitus. Here, we prepared carboxymethyl chitosan-grafted polyvinylpyrrolidone-iodine (CMC-g-PVPI) microspheres and used them to treat chronic wounds. Carboxymethyl chitosan (CMC) was used as the skeleton and was grafted with polyvinylpyrrolidone-iodine (PVPI) to form a CMC-g-PVPI complex hydrogel and CMC-g-PVPI microspheres, which formed as a result of the high shearing dispersion of the complex hydrogel. In vivo experiments on diabetic wounds revealed significantly accelerated wound closure in the presence of the microspheres, demonstrating the excellent potential of CMC-g-PVPI to promote skin wound regeneration under diabetic conditions.

Keywords: Carboxymethyl chitosan; chronic wounds; healing; microspheres; polyvinylpyrrolidone-iodine.

Graphical abstract

Scheme 1.

Schematic illustration of diabetic wound healing with the application of CMC-g-PVPI microspheres.

Figure 1.

(a) Diagram of the synthesis process of CMC-g-PVPI-γ-PGA and CMC-g-PVPI microspheres. (b) and (c) Appearances of the produced CMC-g-PVPI-γ-PGA and CMC-g-PVPI microspheres.

Figure 2.

Synthesis, production and characterization of the CMC-g-PVPI complex hydrogel and CMC-g-PVPI microspheres. (a) Photograph of the formed CMC-g-PVPI complex hydrogel and CMC-g-PVPI microspheres. (b-c) Tyndall effect of the CMC-g-PVPI complex hydrogel and CMC-g-PVPI microspheres in deionized water. (d-e) SEM images of CMC-g-PVPI microspheres. (f) Size distribution of CMC-g-PVPI microspheres. (g) FTIR spectra of CMC and CMC-g-PVPI microspheres. (Black) CMC, (red) CMC-g-PVPI microspheres.

Figure 3.

Application of CMC-g-PVPI microspheres and CMC-g-PVPI-γ-PGA to diabetic wounds. (a) Representative photographs of different healing statuses of diabetic wounds treated with CMC-g-PVPI microspheres and CMC-g-PVPI-γ-PGA or untreated (control) on Days 0, 3, 5, 7, 9, 12, and 14. (b) Wound area ratios of all three groups. N = 5, * P < 0.05, ** P < 0.01.

Figure 4.

(a-c) H&E staining results of different groups on day 14. Scale bars = 500 µm.

Figure 5.

(a-c) Masson trichrome staining results of different groups on day 14. Scale bars = 500 µm.

Figure 6.

Immunohistochemical staining results of different groups on day 14. Scale bars = 100 µm. (a) Anti-CD31 immunohistochemical staining images of wounds in the control group, hydrogel group and powder group. (b) Anti-Ki67 immunohistochemical staining images of wounds in the control group, hydrogel group and powder group. (c) Quantitative evaluation of anti-CD31 immunohistochemical staining of different groups on Day 14. (d) Quantitative evaluation of anti-Ki67 immunohistochemical staining of different groups on Day 14.