Antibacterial activity of mixed metal oxide derived from Zn-Al layered double hydroxide precursors, effect of calcination temperature

For several decades, the use of antibiotics has led to the emergence of highly resistant human and animal pathogens, posing a significant threat to global health, food security, and economic progress. In the quest for alternatives to combat multidrug-resistant bacteria and yeasts, the utilization of nanoparticles materials has emerged as a promising avenue. In this research, we investigated the antimicrobial properties of Zn-Al-layered double hydroxide, synthesized through co-precipitation and subsequently calcined at temperatures of 400, 600, and 800°C. A total of 21 bacterial strains, including 15 clinical strains and 6 Gram-reference strains, along with one fungal strain, were subjected to testing. The synthesized materials underwent characterization using various techniques such as X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), ultraviolet–visible spectroscopy, and fourier-transform infrared (FTIR) spectroscopy. The key findings indicate that the uncalcined Zn-Al-layered double hydroxide and the heterojunction ZnO-ZnAl₂O₄ calcined at 400°C and 600°C exhibited a minimum inhibitory concentration (MIC) of 0.125 μg/mL against the tested strains. The spinell ZnAl₂O₄ calcined at 800°C showed MICs ranging between 0.125 and 2 μg/mL, with a greater bactericidal effect on gram-negative bacteria (GNBs) such as Enterobacteriaceae and non-Enterobacteriaceae compared to Gram-positive bacteria. Consequently, the heterojunction ZnO-ZnAl₂O₄ demonstrated higher efficacy against Gram-positive bacteria. These findings highlight the potential of heterojunction ZnO-ZnAl₂O₄ and spinell ZnAl₂O₄ as mixed metal oxides derived from ZnAl-layered double hydroxide, offering promising alternatives to traditional antibiotics and suggesting their potential use as impregnating agents in matrices with a broad spectrum of specific antimicrobial activity.