Study of antibacterial activity of copper zinc nanocomposites and disruption of bacterial cytoplasmic membrane

Abstract

In recent years, the widespread use of antibiotics has led to the emergence of numerous drug-resistant bacteria, posing a severe threat to both human health and the economy. As a result, it is imperative to develop efficient antibacterial agents that do not induce drug resistance. This study employed layer-by-layer assembly technology to prepare ZnFe₂O₄@ZnS/Cu₂S (ZZC) nanocomposites Gram-negative Escherichia coli (E. coli), Gram-positive Staphylococcus aureus (S. aureus) and drug-resistant Salmonella (T-Salmonella) were utilized as test bacteria to investigate the antibacterial effectiveness and mechanism of ZZC. The findings demonstrated that, the MIC of the ZZC against E. coli, S. aureus and T-Salmonella were 50, 60 and 80 μg/mL, respectively; At a material concentration of 200 μg/mL and a reaction time of 80 min, ZZC demonstrated a bacteriostatic rate of 99.99% against the three tested bacteria. The nano-composite can disrupt cell walls and plasma membranes and effectively and resulting in bacterial rupture and demise. Furthermore, the nano-composite displayed strong biocompatibility and was also able to heal mixed bacterial-induced wound infections and essentially eliminated the bacterial burden after 9 days, and also exhibited excellent antimicrobial activity in vivo. The results also indicate significant potential for its application in medical materials and other areas of research.

Keywords: Antibacterial mechanism; Bacteriostatic materials; Healing of wound; Nano-composites; ZnFe2O4.

Fig. 1

Schematic showing the synthesis of the nano- ZZC complexes.

Fig. 2

TEM image of ZnFe₂O₄ (a), ZZ (b) and ZZC composites (c). HRTEM of nano-ZZC composites (d). Images of EDS element mapping of nano-ZZC composites (e–j). EDS spectra and total mass fraction of the ZZC composites (k, l).

Fig. 3

Full-scan XPS spectra of the nanocomposites (a). XPS spectra of Cu2p (b), Zn2p (c), Fe2p (d), C1s (e), O1s (f) and S2p (g) in nano-ZZC composites. XRD pattern of nano-ZZC composites (h). FT-IR spectra of nano-ZZC composites (i).

Fig. 4

Results of filter paper diffusion of different concentrations of ZnFe₂O₄, ZZ, ZZZ, ZZZC and nano-ZZC composites against E. coli (a), S. aureus (b) and T-Salmonella (c).

Fig. 5

(a) Colony numbers at different times after treatment of the three test bacteria with nano-ZZC composites. (b) Bacteriostatic rates of nano-ZZC composites against the three test bacteria at different times.

Fig. 6

Three test bacteria not treated with nano-ZZC (a–c). Representative fluorescence images of bacterial cells after 12 h of treatment. Dead S. aureus (d), E. coli (e) and T-Salmonella (f), shown by PI staining.

Fig. 7

Zeta potentials of 200 µg/mL nano-ZZC composites mixed with S. aureus, E. coli and T- Salmonella for 5 and 40 min (a). Cytoplasmic leakage of S. aureus (b), E. coli (c) and T-Salmonella (d) after treatment with the nanocomposites.

Fig. 8

The results of Ion leakage of E. coli (a), S. aureus (b) and T-Salmonella (c).

Fig. 9

Different samples were tested using DMPO, DMPO + CH₃OH, and TEMP as spin traps to obtain the Electron Paramagnetic Resonance (EPR) spectra of O₂^·−, ¹O₂, and ·OH.

Fig. 10

Toxicity analysis of the ZZC composites.

Fig. 11

Schematic of ZZC-mediated treatment to inhibit bacteria and promote wound healing (a). Photographs of skin wounds infected with three bacterial mixtures on different days of treatment and superimposed wound healing diagram (b). Changes in skin wound area in different groups of mice (c). Dynamics of tissue recovery as shown by H&E staining and Masson staining histological images of ZZC on days 3 and 9 ninety days in the mixed bacterial wound infection mouse model. Scale bar is 100 μm (d).

Fig. 12

Schematic depicting the bacteriostatic mechanism.