Bacterial exopolysaccharides (EPSs) are biomolecules secreted in the extracellular space and have diverse biological functionalities, such as environmental protection, surface adherence, and cellular ...interactions. EPSs have been found to be biocompatible and eco-friendly, therefore making them suitable for applications in many areas of study and various industrial products. Recently, synthesis and stabilization of metal nanoparticles have been of interest because their usefulness for many biomedical applications, such as antimicrobials, anticancer drugs, antioxidants, drug delivery systems, chemical sensors, contrast agents, and as catalysts. In this context, bacterial EPSs have been explored as agents to aid in a greener production of a myriad of metal nanoparticles, since they have the ability to reduce metal ions to form nanoparticles and stabilize them acting as capping agents. In addition, by incorporating EPS to the metal nanoparticles, the EPS confers them biocompatibility. Thus, the present review describes the main bacterial EPS utilized in the synthesis and stabilization of metal nanoparticles, the mechanisms involved in this process, and the different applications of these nanoparticles, emphasizing in their biomedical applications.
One of the main issues in the medical field and clinical practice is the development of novel and effective treatments against infections caused by antibiotic-resistant bacteria. One avenue that has ...been approached to develop effective antimicrobials is the use of silver nanoparticles (Ag-NPs), since they have been found to exhibit an efficient and wide spectrum of antimicrobial properties. Among the main drawbacks of using Ag-NPs are their potential cytotoxicity against eukaryotic cells and the latent environmental toxicity of their synthesis methods. Therefore, diverse green synthesis methods, which involve the use of environmentally friendly plant extracts as reductive and capping agents, have become attractive to synthesize Ag-NPs that exhibit antimicrobial effects against resistant bacteria at concentrations below toxicity thresholds for eukaryotic cells.
In this study, we report a green one-pot synthesis method that uses
extract as a reducing and capping agent, to produce Ag-NPs with applications as therapeutic agents to treat infections in vivo.
The Ag-NPs were characterized using transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction, energy-dispersive spectroscopy, ultraviolet-visible, and Fourier transform infrared.
We show that Ag-NPs are spherical with a narrow size distribution. The Ag-NPs show antimicrobial activities in vitro against Gram-negative (
,
, and a clinical multidrug-resistant strain of
) and Gram-positive (
) bacteria. Moreover, antimicrobial effects of the Ag-NPs, against a resistant
clinical strain, were tested in a murine skin infection model. The results demonstrate that the Ag-NPs reported in this work are capable of eradicating pathogenic resistant bacteria in an infection in vivo. In addition, skin, liver, and kidney damage profiles were monitored in the murine infection model, and the results demonstrate that Ag-NPs can be used safely as therapeutic agents in animal models.
Together, these results suggest the potential use of Ag-NPs, synthesized by green chemistry methods, as therapeutic agents against infections caused by resistant and nonresistant strains.
Due to the emergence of multi-drug resistant strains, development of novel antibiotics has become a critical issue. One promising approach is the use of transition metals, since they exhibit rapid ...and significant toxicity, at low concentrations, in prokaryotic cells. Nevertheless, one main drawback of transition metals is their toxicity in eukaryotic cells. Here, we show that the barriers to use them as therapeutic agents could be mitigated by combining them with silver. We demonstrate that synergism of combinatorial treatments (Silver/transition metals, including Zn, Co, Cd, Ni, and Cu) increases up to 8-fold their antimicrobial effect, when compared to their individual effects, against E. coli and B. subtilis. We find that most combinatorial treatments exhibit synergistic antimicrobial effects at low/non-toxic concentrations to human keratinocyte cells, blast and melanoma rat cell lines. Moreover, we show that silver/(Cu, Ni, and Zn) increase prokaryotic cell permeability at sub-inhibitory concentrations, demonstrating this to be a possible mechanism of the synergistic behavior. Together, these results suggest that these combinatorial treatments will play an important role in the future development of antimicrobial agents and treatments against infections. In specific, the cytotoxicity experiments show that the combinations have great potential in the treatment of topical infections.
The present study centers on the synthesis of ultra-small silver nanoparticles (AgNPs) with antibacterial properties using citrus peel residues (orange, lemon, and grapefruit) as reducing and ...stabilizing agents, and on assessing their antibacterial activity against multidrug-resistant clinical
. The synthesized AgNPs were analyzed by various techniques, including UV-Vis spectroscopy, SAED, TEM, XRD, FTIR, and Raman. The results demonstrate the formation of ultra-small, monodisperse, quasi-spherical AgNPs with an average particle size of 2.42 nm for AgNPs produced with mixed extracts. XRD analysis indicated that the AgNPs have a crystal size of 9.71 to 16.23 nm. The AgNPs exhibited potent inhibitory activity against resistant
, with a minimum inhibitory concentration (MIC) of 15.625 to 62.50 ppm. The findings suggest that the ultra-small nanometer size of the AgNPs could be attributed to the synthesis method that employs ambient conditions and the presence of polyphenolic compounds from citrus peel. Consequently, AgNPs obtained through sustainable green synthesis hold significant potential in combating clinical multi-resistant bacterial strains that are challenging to treat and eradicate. This approach also contributes to the revaluation of citrus residues in the region, which is an ongoing environmental issue today.
The use of natural zeolite clinoptilolite to reduce the leaching rate of potentially toxic elements such as Cd, Pb, and Mn in soil from mine tailings was studied. Soil from the surroundings of the ...mine El Bote in Zacatecas, Mexico, was analyzed, and the zeolite was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and nitrogen physisorption. An ammonium-exchange method for the zeolite was employed. Leaching experiments using packed columns with polluted soil and zeolite mixtures were carried out and the effect of the pH of the carrier solutions was studied. Incorporation of zeolite in the soil achieved a beneficial increase in pH, from 5.03 to 6.95. The concentration of Cd and Mn was reduced when zeolite was present in the column and the ammonium-modified zeolite with ammonia also enhanced the concentration reduction of metallic species in leachates in a range of 28 to 68%. The first-order model best fits the experimental data, suggesting that the leaching rate is controlled by concentration difference between the liquid and the soil matrix. These results demonstrate the potential for using natural zeolite clinoptilolite to reduce the leaching rate of potentially toxic elements in soil from mine tailings.
Currently, the large amount of organic waste produced represents one of the leading environmental problems. According to United Nations, every year a third of all food produced ends up rotting and, ...therefore, becoming waste. Its use and revalorization represent an attractive alternative in the search for solutions to this situation. In this context, these residues can be used to obtain extracts beneficial for nanotechnology, acting as a reducing and stabilizing agent to produce metal nanomaterials such as silver nanoparticles by green synthesis, an ecofriendly and nontoxic method. Silver nanoparticles have been applied in applications as antibacterial, antifungal, and catalytic agents, as well as antioxidants, biosensors, and treatment of various diseases. Thus, this review contributes to fostering and promoting a sustainable environmental awareness through the reuse and revalorization of organic waste, which allows the sustainable biosynthesis of functional silver nanoparticles to be widely applied successfully in various fields of application.
The revalorization and use of organic waste allows obtaining extracts that act as a reducing and stabilizing agent for green and sustainable synthesis of functional AgNPs from Ag+ ions, which have potential application in biomedical and environmental areas due to their diverse properties such as antibacterial, antifungal, anti‐aging and treatment of various diseases, as well as catalytic agents, antioxidants, biosensors, among others.
Due to the recent emergence of multi-drug resistant strains, the development of novel antimicrobial agents has become a critical issue. The use of micronutrient transition metals is a promising ...approach to overcome this problem since these compounds exhibit significant toxicity at low concentrations in prokaryotic cells. In this work, we demonstrate that at concentrations lower than their minimal inhibitory concentrations and in combination with different antibiotics, it is possible to mitigate the barriers to employ metallic micronutrients as therapeutic agents. Here, we show that when administered as a combinatorial treatment, Cu
2+
, Zn
2+
, Co
2+
, Cd
2+
, and Ni
2+
increase susceptibility of
Escherichia coli
and
Staphylococcus aureus
to ampicillin and kanamycin. Furthermore, ampicillin-resistant
E. coli
is re-sensitized to ampicillin when the ampicillin is administered in combination with Cu
2+
, Cd
2+
, or Ni
2
. Similarly, Cu
2+
, Zn
2+
, or Cd
2+
re-sensitize kanamycin-resistant
E. coli
and
S. aureus
to kanamycin when administered in a combinatorial treatment with those transition metals. Here, we demonstrate that for both susceptible and resistant bacteria, transition-metal micronutrients, and antibiotics interact synergistically in combinatorial treatments and exhibit increased effects when compared to the treatment with the antibiotic alone. Moreover,
in vitro
and
in vivo
assays, using a murine topical infection model, showed no toxicological effects of either treatment at the administered concentrations. Lastly, we show that combinatorial treatments can clear a murine topical infection caused by an antibiotic-resistant strain. Altogether, these results suggest that antibiotic-metallic micronutrient combinatorial treatments will play an important role in future developments of antimicrobial agents and treatments against infections caused by both susceptible and resistant strains.
The Ginkgo biloba extract (GbE) is a commercial product used as a nutraceutic herbal remedy in Europe and US. It contains 27% of the polyphenols isorhamnetin, kaempferol, and quercetin, as ...antioxidants. We used male adult Wistar rats (200–300 g), divided into four groups: control group (treated with 5.0 mg/kg of sodium chloride, intravenous), titanium dioxide nanoparticles (TiO2-NPs) group (5.0 mg/kg, intravenous), GbE group (10 mg/kg, intraperitoneal), and GbE + TiO2-NPs group (treated 24 h before with 10 mg/kg of GbE, intraperitoneal), followed, 24 h later, by 5.0 mg/kg of TiO2-NPs intravenously. The statistical analysis was performed using Student’s t-test for grouped data with ANOVA posttest. The GbE protected renal cells against the effects of TiO2-NPs because it reversed the increased activity of γ-glutamyltranspeptidase and the enzymatic activity of dipeptidylaminopeptidase IV at all times tested (0–5, 5–24, 24–48, and 48–72 h). Also it reversed the glucosuria, hypernatriuria, and urine osmolarity at three times tested (5–24, 24–48, and 48–72). Thus, we conclude that GbE has a beneficial activity in the cytoplasmic membranes of brush border cells on the renal tubules, against the adverse effects that can be produced by some xenobiotics in this case the TiO2-NPs, in experimental rats.
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