Antimicrobial activity of metals: mechanisms, molecular targets and applications
TL;DR: The chemical and toxicological principles that underlie the antimicrobial activity of metals are described and the preferences of metal atoms for specific microbial targets are discussed.
Abstract: 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.
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TL;DR: The current status and possible opportunities for ROS generation for cancer therapy are summarized and it is hoped this review will spur pre-clinical research and clinical practice for ROS-mediated tumour treatments.
Abstract: The reactive oxygen species (ROS)-mediated mechanism is the major cause underlying the efficacy of photodynamic therapy (PDT). The PDT procedure is based on the cascade of synergistic effects between light, a photosensitizer (PS) and oxygen, which greatly favors the spatiotemporal control of the treatment. This procedure has also evoked several unresolved challenges at different levels including (i) the limited penetration depth of light, which restricts traditional PDT to superficial tumours; (ii) oxygen reliance does not allow PDT treatment of hypoxic tumours; (iii) light can complicate the phototherapeutic outcomes because of the concurrent heat generation; (iv) specific delivery of PSs to sub-cellular organelles for exerting effective toxicity remains an issue; and (v) side effects from undesirable white-light activation and self-catalysation of traditional PSs. Recent advances in nanotechnology and nanomedicine have provided new opportunities to develop ROS-generating systems through photodynamic or non-photodynamic procedures while tackling the challenges of the current PDT approaches. In this review, we summarize the current status and discuss the possible opportunities for ROS generation for cancer therapy. We hope this review will spur pre-clinical research and clinical practice for ROS-mediated tumour treatments.
1,305 citations
TL;DR: This overview incorporates a retrospective of previous reviews published from 2007 to 2013 and recent original contributions on the progress of research on antimicrobial mechanisms to summarize the current knowledge in the field of antibacterial activity of silver nanoparticles.
1,055 citations
TL;DR: This Review focuses on current therapeutic strategies and those under development that target vital structural and functional traits of microbial biofilms and drug tolerance mechanisms, including the extracellular matrix and dormant cells.
Abstract: Biofilm formation is a key virulence factor for a wide range of microorganisms that cause chronic infections. The multifactorial nature of biofilm development and drug tolerance imposes great challenges for the use of conventional antimicrobials and indicates the need for multi-targeted or combinatorial therapies. In this Review, we focus on current therapeutic strategies and those under development that target vital structural and functional traits of microbial biofilms and drug tolerance mechanisms, including the extracellular matrix and dormant cells. We emphasize strategies that are supported by in vivo or ex vivo studies, highlight emerging biofilm-targeting technologies and provide a rationale for multi-targeted therapies aimed at disrupting the complex biofilm microenvironment.
1,039 citations
TL;DR: The sources of toxic heavy metals are discussed, the groups of microorganisms with biosorbent potential for heavy metal removal are described and the use of microbial biosorbents is eco-friendly and cost effective.
Abstract: Persistent heavy metal pollution poses a major threat to all life forms in the environment due to its toxic effects. These metals are very reactive at low concentrations and can accumulate in the food web, causing severe public health concerns. Remediation using conventional physical and chemical methods is uneconomical and generates large volumes of chemical waste. Bioremediation of hazardous metals has received considerable and growing interest over the years. The use of microbial biosorbents is eco-friendly and cost effective; hence, it is an efficient alternative for the remediation of heavy metal contaminated environments. Microbes have various mechanisms of metal sequestration that hold greater metal biosorption capacities. The goal of microbial biosorption is to remove and/or recover metals and metalloids from solutions, using living or dead biomass and their components. This review discusses the sources of toxic heavy metals and describes the groups of microorganisms with biosorbent potential for heavy metal removal.
1,035 citations
Cites background from "Antimicrobial activity of metals: m..."
...These transporters assist in either the co-transport of these metals in complexes with low-molecular-mass ligands, or in the direct uptake of non-essential metals [62]....
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TL;DR: In this paper, the main parameters that will affect the surface state of nanoparticles and their influence on antimicrobial efficacy are reviewed and an analysis of several works on Ag NPs activity, observed through the scope of an oxidative Ag+ release.
976 citations
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TL;DR: In this paper, the rate data for the generalized nucleophilic displacement reaction were reviewed, and the authors presented a method to estimate the rate of the generalized displacement reaction in terms of the number of nucleophiles.
Abstract: Recently (1) the rate data for the generalized nucleophilic displacement reaction were reviewed.
8,433 citations
TL;DR: In this paper, a property called absolute hardness eta is defined for neutral and charged species, atomic and molecular, for both hard and soft acids and bases, by making use of the hypothesis that extra stability attends bonding of A to B when the ionization potentials of A and B in the molecule are the same.
Abstract: For neutral and charged species, atomic and molecular, a property called absolute hardness eta is defined. Let E(N) be a ground-state electronic energy as a function of the number of electrons N. As is well-known, the derivative of E(N) with respect to N, keeping nuclear charges Z fixed, is the chemical potential ..mu.. or the negative of the absolute electronegativity chi: ..mu.. = (deltaE/deltaN)/sub Z/ = /sup -/chi. The corresponding second derivative is hardness: 2eta = (delta..mu../deltaN)/sub Z/ = (deltachi/deltaN)/sub Z/ = (delta/sup 2/E/deltaN/sup 2/)/sub Z/. Operational definitions of chi and eta are provided by the finite difference formulas (the first due to Mulliken) chi = 1/2(I+A), eta = 1/2(I-A), where I and A are the ionization potential and electron affinity of the species in question. Softness is the opposite of hardness: a low value of eta means high softness. The principle of hard and soft acids and bases is derived theoretically by making use of the hypothesis that extra stability attends bonding of A to B when the ionization potentials of A and B in the molecule (after charge transfer) are the same. For bases B, hardness is identified as the hardness of the species B/sup +/. Tables ofmore » absolute hardness are given for a number of free atoms, Lewis acids, and Lewis bases, and the values are found to agree well with chemical facts. 1 figure, 3 tables.« less
6,030 citations
TL;DR: Monodisperse samples of silver nanocubes were synthesized in large quantities by reducing silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP), characterized by a slightly truncated shape bounded by {100, {110}, and {111} facets.
Abstract: Monodisperse samples of silver nanocubes were synthesized in large quantities by reducing silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP). These cubes were single crystals and were characterized by a slightly truncated shape bounded by {100}, {110}, and {111} facets. The presence of PVP and its molar ratio (in terms of repeating unit) relative to silver nitrate both played important roles in determining the geometric shape and size of the product. The silver cubes could serve as sacrificial templates to generate single-crystalline nanoboxes of gold: hollow polyhedra bounded by six {100} and eight {111} facets. Controlling the size, shape, and structure of metal nanoparticles is technologically important because of the strong correlation between these parameters and optical, electrical, and catalytic properties.
5,992 citations
TL;DR: This review examines the evidence for involvement of the oxidative stress in the carcinogenesis process and the role of enzymatic and non-enzymatic antioxidants in the process of carcinogenesis as well as the antioxidant interactions with various regulatory factors.
5,937 citations
TL;DR: The results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diameter of approximately 1-10 nm.
Abstract: Nanotechnology is expected to open new avenues to fight and prevent disease using atomic scale tailoring of materials. Among the most promising nanomaterials with antibacterial properties are metallic nanoparticles, which exhibit increased chemical activity due to their large surface to volume ratios and crystallographic surface structure. The study of bactericidal nanomaterials is particularly timely considering the recent increase of new resistant strains of bacteria to the most potent antibiotics. This has promoted research in the well known activity of silver ions and silver-based compounds, including silver nanoparticles. The present work studies the effect of silver nanoparticles in the range of 1-100 nm on Gram-negative bacteria using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). Our results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diameter of approximately 1-10 nm.
5,609 citations