Metals have been used as antimicrobial agents since antiquity, but throughout most of history their modes of action have remained unclear. Recent studies indicate that different metals cause discrete and distinct types of injuries to microbial cells as a result of oxidative stress, protein dysfunction or membrane damage. Here, we describe the chemical and toxicological principles that underlie the antimicrobial activity of metals and discuss the preferences of metal atoms for specific microbial targets. Interdisciplinary research is advancing not only our understanding of metal toxicity but also the design of metal-based compounds for use as antimicrobial agents and alternatives to antibiotics.

Antimicrobial activity of metals: mechanisms, molecular targets and applications

Recent advances in nanoscience and nanotechnology radically changed the way we diagnose, treat, and prevent various diseases in all aspects of human life. Silver nanoparticles (AgNPs) are one of the most vital and fascinating nanomaterials among several metallic nanoparticles that are involved in biomedical applications. AgNPs play an important role in nanoscience and nanotechnology, particularly in nanomedicine. Although several noble metals have been used for various purposes, AgNPs have been focused on potential applications in cancer diagnosis and therapy. In this review, we discuss the synthesis of AgNPs using physical, chemical, and biological methods. We also discuss the properties of AgNPs and methods for their characterization. More importantly, we extensively discuss the multifunctional bio-applications of AgNPs; for example, as antibacterial, antifungal, antiviral, anti-inflammatory, anti-angiogenic, and anti-cancer agents, and the mechanism of the anti-cancer activity of AgNPs. In addition, we discuss therapeutic approaches and challenges for cancer therapy using AgNPs. Finally, we conclude by discussing the future perspective of AgNPs.

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Silver Nanoparticles: Synthesis, Characterization, Properties, Applications, and Therapeutic Approaches

Synthesis of metallic nanoparticles using plant extracts.

Polymeric materials with antimicrobial activity

Silver nanoparticles: A new view on mechanistic aspects on antimicrobial activity

The antibacterial activity and acting mechanism of silver nanoparticles (SNPs) on Escherichia coli ATCC 8739 were investigated in this study by analyzing the growth, permeability, and morphology of the bacterial cells following treatment with SNPs. The experimental results indicated 10 microg/ml SNPs could completely inhibit the growth of 10(7) cfu/ml E. coli cells in liquid Mueller-Hinton medium. Meanwhile, SNPs resulted in the leakage of reducing sugars and proteins and induced the respiratory chain dehydrogenases into inactive state, suggesting that SNPs were able to destroy the permeability of the bacterial membranes. When the cells of E. coli were exposed to 50 microg/ml SNPs, many pits and gaps were observed in bacterial cells by transmission electron microscopy and scanning electron microscopy, and the cell membrane was fragmentary, indicating the bacterial cells were damaged severely. After being exposed to 10 microg/ml SNPs, the membrane vesicles were dissolved and dispersed, and their membrane components became disorganized and scattered from their original ordered and close arrangement based on TEM observation. In conclusion, the combined results suggested that SNPs may damage the structure of bacterial cell membrane and depress the activity of some membranous enzymes, which cause E. coli bacteria to die eventually.

Antibacterial activity and mechanism of silver nanoparticles on Escherichia coli.

In this paper, according to the fieldwork and statistic analysis, the issues for the relativity between airborne microbes and environmental factors in Pearl River delta’ Urban Agglomeration, Guangdong are discussed using ecological method in order to research on health prevention and environment control measures in Pearl River delta’ Urban. The results show that as follow:(1) The average content of airborne microbes (fungi and bacteria) in Guangzhou and Dongguan is higher than other 6 cities in Pearl River delta’ Urban; the content of bacteria is higher than fungi; outdoor content is higher than indoor content; the average content of airborne microbe in the area without greenbelt is higher than the area with greenbelt; the average content of airborne microbe are higher during spring and summer than other seasons. (2) There are obvious relativity between the average content of airborne microbes (fungi and bacteria) and environment factors (wind speed, humidity, temperature, total suspended particulate (Tsp); Furthermore, most of those have positive or negative linear relationship. (3) There are also obvious relativity between the average content of airborne microbes (fungi and bacteria) and the number of person flowrate, car flowrate and condition of afforestation, population density.

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Study on the Relativity between Airborne Microbes and Environmental Factors in Pearl River Delta’ Urban Agglomeration, Guangdong

The invention relates to a sauce anti-corrosive antistaling agent, comprising 75%-90% quality percentage of prptamine, 2%-10% quality percentage of sucrose fatty acid ester, 2%-10% quality percentage of EDTA and 2%-5% quality percentage of sodium glutamate. The effect of the sauce anti-corrosive antistaling agent has reached or exceeds the sodium benzoate and potassium sorbate. The sauce anti-corrosive antistaling agent is safe and non-poisonous and beneficial to the health of the user with wide application prospect.

Sauce antisepsis antistaling agent

The strong survival ability of Salmonella in low-moisture foods (LMFs) has been of public concern, and is considered a threat to people’s health. Recently, the development of omics technology has promoted research on the molecular mechanisms of the desiccation stress response of pathogenic bacteria. However, multiple analytical aspects related to their physiological characteristics remain unclear. We explored the physiological metabolism changes of S. enterica Enteritidis exposed to a 24 h-desiccation treatment and a subsequent 3-month desiccation storage in skimmed milk powder (SMP) with an approach of gas chromatography–mass spectrometry (GC–MS) and ultra-performance liquid chromatography-Q Exactive-mass spectrometry (UPLC-QE-MS). A total of 8,292 peaks were extracted, of which 381 were detected by GC–MS and 7,911 peaks were identified by LC–MS/MS, respectively. Through analyses of differentially expressed metabolites (DEMs) and key pathways, a total of 58 DEMs emerged from the 24 h-desiccation treatment, which exhibited the highest relevance for five metabolic pathways, involving glycine, serine, and threonine metabolism, pyrimidine metabolism, purine metabolism, vitamin B6 metabolism, and pentose phosphate pathway. After 3-month SMP storage, 120 DEMs were identified, which were related to several regulatory pathways including arginine and proline metabolism, serine and threonine metabolism, β-alanine metabolism, glycerolipid metabolism, and glycolysis. The analyses of key enzyme activities of XOD, PK, and G6PDH and ATP content provided further evidence that supported the metabolic responses such as nucleic acid degradation, glycolysis, and ATP production played an important role in Salmonella’s adaptation to desiccation stress. This study enables a better understanding of metabolomics-based responses of Salmonella at the initial stage of desiccation stress and the following long-term adaptive stage. Meanwhile, the identified discriminative metabolic pathways may serve as potentially useful targets in developing strategies for the control and prevention of desiccation-adapted Salmonella in LMFs.

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Haiyan Zeng

Papers

Antibacterial activity and mechanism of silver nanoparticles on Escherichia coli.

Study on the Relativity between Airborne Microbes and Environmental Factors in Pearl River Delta’ Urban Agglomeration, Guangdong

Sauce antisepsis antistaling agent

Metabolomics-based response of Salmonella to desiccation stress and skimmed milk powder storage