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Contact Mode Atomic Force Microscopy as a Rapid Technique for Morphological Observation and Bacterial Cell Damage Analysis

Electron microscopy is one of the tools required to characterize cellular structures. However, the procedure is complicated and expensive due to the ...

Universidad de Guadalajara

Magnesium oxide nanoparticles (MgO NPs) were obtained by the calcination of precursor microparticles (PM) synthesized by a novel triethylamine-based precipitation method. Scanning electron microscopy (SEM) revealed a mean size of 120 nm for the MgO NPs. The results of the characterizations for MgO NPs support the suggestion that our material has the capacity to attack, and have an antibacterial effect against, Gram-negative and Gram-positive bacteria strains. The ability of the MgO NPs to produce reactive oxygen species (ROS), such as superoxide anion radicals (O2•-) or hydrogen peroxide (HO), was demonstrated by the corresponding quantitative assays. The MgO antibacterial activity was evaluated against Gram-positive  and Gram-negative  bacteria, with minimum inhibitory concentrations (MICs) of 250 and 500 ppm on the microdilution assays, respectively. Structural changes in the bacteria, such as membrane collapse; surface changes, such as vesicular formation; and changes in the longitudinal and horizontal sizes, as well as the circumference, were observed using atomic force microscopy (AFM). The lipidic peroxidation of the bacterial membranes was quantified, and finally, a bactericidal mechanism for the MgO NPs was also proposed.

Two-Step Triethylamine-Based Synthesis of MgO Nanoparticles and Their Antibacterial Effect against Pathogenic Bacteria.

This study reports a green, simple, and fast method for the synthesis of gold and silver nanoparticles using natural antioxidant compounds. The aqueous extract from dried rosehips (pseudofruit of  L.) was used as a reducing and capping agent of HAuCl and AgNO during the noble metal colloid synthesis at room temperature and no other chemical reagent was used. The high antioxidant activity of the plant extract was proven by 2,2-diphenyl-1-picrylhydrazyl assay by a spectrophotometric method. The formation of stable gold and silver nanoparticles was observed by UV-visible spectroscopy and the evolution of their characteristic surface plasmon resonance band was followed over several days. Transmission electron microscopy confirmed the formation of quasi-spherical nanoparticles with mean diameters 26 and 34 nm, for gold and silver nanoparticles, respectively; XRD revealed an FCC crystalline structure for both gold and silver NPs. The effects of concentrations of noble metal precursor and plant extract solution on the formation, stabilization and size of nanoparticles are discussed, as well as some applications of these colloids.

Virginia Villa-Cruz

Centro Universitario de los Lagos

Universidad de Guadalajara

Contact Mode Atomic Force Microscopy as a Rapid Technique for Morphological Observation and Bacterial Cell Damage Analysis

Virginia Villa-Cruz

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Universidad de Guadalajara

Contact Mode Atomic Force Microscopy as a Rapid Technique for Morphological Observation and Bacterial Cell Damage Analysis

Centro Universitario de los Lagos