Synthesis of Chitosan-Based Gold Nanoparticles: Antimicrobial and Wound-Healing Activities

Abstract

The global spread of multidrug-resistant bacteria has become a significant hazard to public health, and more effective antibacterial agents are required. Therefore, this study describes the preparation, characterization, and evaluation of gold nanoparticles modified with chitosan (Chi/AuNPs) as a reducing and stabilizing agent with efficient antimicrobial effects. In recent years, the development of an efficient and ecofriendly method for synthesizing metal nanoparticles has attracted a lot of interest in the field of nanotechnology. Colloidal gold nanoparticles (AuNPs) were prepared by the chemical reduction of gold ions in the presence of chitosan (Chi), giving Chi/AuNPs. The characterization of Chi/AuNPs was carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and X-ray diffraction (XRD). Chi/AuNPs appeared spherical and monodispersed, with a diameter ranging between 20 to 120 nm. The synergistic effects of AuNPs and Chi led to the disruption of bacterial membranes. The maximum inhibitory impact was seen against P. aeruginosa at 500 µg/mL, with a zone of inhibition diameter of 26 ± 1.8 mm, whereas the least inhibitory effect was reported for S. aureus, with a zone of inhibition diameter of 16 ± 2.1 mm at the highest dose tested. Moreover, Chi/AuNPs exhibited antifungal activity toward Candida albicans when the MIC was 62.5 µg/mL. Cell viability and proliferation of the developed nanocomposite were evaluated using a sulphorhodamine B (SRB) assay with a half inhibitory concentration (IC₅₀) of 111.1 µg/mL. Moreover, the in vitro wound-healing model revealed that the Chi/AuNP dressing provides a relatively rapid and efficacious wound-healing ability, making the obtained nanocomposite a promising candidate for the development of improved bandage materials.

Keywords: antibacterial activity; antifungal activity; chitosan; cytotoxicity; nanocomposite; wound healing.

Figure 1

TEM images (A), SAED pattern (B), SEM image (C), and (D) EDX spectrum of Chi/AuNPs.

Figure 2

FTIR spectrum (A), XRD pattern (B), particle size distribution (C), and zeta potential (D) of Chi/AuNPs.

Figure 3

In vitro cytotoxicity effects on doxorubicin and Chi/AuNPs against the normal human skin cell line (BJ-1), assessed by SRB colorimetric assay, respectively.

Figure 4

Effects of different treatments on wound area contraction (0–72 h). Values are given as mean ± SD (n = 3/group). Different letters indicate significant differences (p < 0.05).

Figure 5

Representative micrograph pictures of cells treated with 100 μg/mL of the tested compound (Chi/AuNPs) and untreated (control) at 0 and 24 h. Wound closure rates are expressed as a percentage of scratch closure after 0 to 96 h compared to the initial area.

Figure 6

Time-kill plots of Chi/AuNPs against human pathogenic bacterial strains A: Staphylococcus aureus (A), Pseudomonas aeruginosa (B), Bacillus subtilis (C), and Klebsiella oxytoca (D) at different concentrations and time length. The experiment was performed in triplicate and a graph of the log CFU/mL was plotted against time.

Figure 6

Time-kill plots of Chi/AuNPs against human pathogenic bacterial strains A: Staphylococcus aureus (A), Pseudomonas aeruginosa (B), Bacillus subtilis (C), and Klebsiella oxytoca (D) at different concentrations and time length. The experiment was performed in triplicate and a graph of the log CFU/mL was plotted against time.

Figure 7

Antifungal activity (A) and minimum inhibitory concentration (B) of Chi/AuNPs, chitosan, HAuCl4.3H2O, and nystatin against C. albicans, A. terreus, A. niger, and A. fumigatus.