Metal-based nanoparticles have been extensively investigated for a set of biomedical applications. According to the World Health Organization, in addition to their reduced size and selectivity for bacteria, metal-based nanoparticles have also proved to be effective against pathogens listed as a priority. Metal-based nanoparticles are known to have non-specific bacterial toxicity mechanisms (they do not bind to a specific receptor in the bacterial cell) which not only makes the development of resistance by bacteria difficult, but also broadens the spectrum of antibacterial activity. As a result, a large majority of metal-based nanoparticles efficacy studies performed so far have shown promising results in both Gram-positive and Gram-negative bacteria. The aim of this review has been a comprehensive discussion of the state of the art on the use of the most relevant types of metal nanoparticles employed as antimicrobial agents. A special emphasis to silver nanoparticles is given, while others (e.g., gold, zinc oxide, copper, and copper oxide nanoparticles) commonly used in antibiotherapy are also reviewed. The novelty of this review relies on the comparative discussion of the different types of metal nanoparticles, their production methods, physicochemical characterization, and pharmacokinetics together with the toxicological risk encountered with the use of different types of nanoparticles as antimicrobial agents. Their added-value in the development of alternative, more effective antibiotics against multi-resistant Gram-negative bacteria has been highlighted.

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Metal-based nanoparticles as antimicrobial agents: an overview.

Synthesis of zinc oxide nanoparticles using plant leaf extract against urinary tract infection pathogen

The ability of organisms and organic compounds to reduce metal ions and stabilize them into nanoparticles (NPs) forms the basis of green synthesis. To date, synthesis of NPs from various metal ions using a diverse array of plant extracts has been reported. However, a clear understanding of the mechanism of green synthesis of NPs is lacking. Although most studies have neglected to analyze the green-synthesized NPs (GNPs) for the presence of compounds derived from the extract, several studies have demonstrated the conjugation of sugars, secondary metabolites, and proteins in these biogenic NPs. Despite several reports on the bioactivities (antimicrobial, antioxidant, cytotoxic, catalytic, etc.) of GNPs, only a handful of studies have compared these activities with their chemically synthesized counterparts. These comparisons have demonstrated that GNPs possess better bioactivities than NPs synthesized by other methods, which might be attributed to the presence of plant-derived compounds in these NPs. The ability of NPs to bind with organic compounds to form a stable complex has huge potential in the harvesting of precious molecules and for drug discovery, if harnessed meticulously. A thorough understanding of the mechanisms of green synthesis and high-throughput screening of stabilizing/capping agents on the physico-chemical properties of GNPs is warranted to realize the full potential of green nanotechnology.

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Secondary Metabolites in the Green Synthesis of Metallic Nanoparticles

Over the past decade, incorporation of nanomaterials into agricultural practices like nanofertilizers and nanopesticides has gained a lot of attention. Progress and application of fertilizers in nanoforms are one of the effective options for considerable improvement of the agricultural yield worldwide. Zinc oxide nanoparticles (ZnO NPs) are considered as a biosafe material for biological species. Earlier studies have shown the potential of ZnO NPs in stimulation of seed germination and plant growth as well as disease suppression and plant protection by its antimicrobial activity. However, both positive and negative effects of ZnO NPs on plant growth and metabolism at various developmental periods have been documented. Uptake, translocation and accumulation of ZnO NPs by plants depend upon the features of NPs as well as the anatomy of the host plant. This review summarizes the applications of ZnO NPs as nanofertilizer in crop production and also attempts to examine and record the possible mechanism of antimicrobial activity of ZnO NPs. Biological synthesis of ZnO NPs and their uptake, translocation and biotransformation in plants via various routes have also been examined.

Zinc oxide nanoparticles: a review of their biological synthesis, antimicrobial activity, uptake, translocation and biotransformation in plants

Green synthesis of metal oxide nanoparticles using plant extract is a promising alternative to traditional method of chemical synthesis. In this paper, we report the synthesis of nanostructured zinc oxide particles by biological method. Highly stable and spherical zinc oxide nanoparticles are produced by using zinc acetate and Ixora coccinea leaf extract. Formation of zinc oxide nanoparticles has been confirmed by UV-Vis absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Dynamic light scattering analysis (DLS), zetapotential study and Scanning Electron Microscope with the Energy Dispersive X-ray studies (EDX). Dynamic light scattering analysis shows average particle size of 145.1 nm whereas high zeta potential value confirms the stability of formed zinc oxide nanoparticles. The Scanning Electron Microscope reveals spherical morphology of nanoparticles and Energy Dispersive X-ray analysis confirms the formation of highly pure zinc oxide nanoparticles. The zinc oxide nanoparticles from Ixora coccinea leaves are expected to have applications in biomedical, cosmetic industries, biotechnology, sensors, medical, catalysis, optical device, coatings, drug delivery and water remediation, and also may be applied for electronic and magneto-electric devices. This new eco-friendly approach of synthesis is a novel, cheap, and convenient technique suitable for large scale commercial production.

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Biosynthesis of Zinc Oxide Nanoparticles Using Ixora Coccinea Leaf Extract—A Green Approach

Zinc oxide (ZnO) nanoparticles (NPs) have been synthesized using Hibiscus subdariffa leaf extract. Temperature dependent synthesis and particle growth have been studied. Formation of NPs was confirmed by UV-visible (UV-VIS) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Electron microscopy has been used to study the morphology and size distribution of the synthesized particles. The synthesized ZnO nanoparticles as potential anti-bacterial agents have been studied on Escherichia coli and Staphylococcus aureus. Another study has indicated that small sized ZnO NPs, stabilized by plant metabolites had better anti-diabetic effect on streptozotocin (STZ) induced diabetic mice than that of large sized ZnO particles. It has also been observed by enzyme linked immunosorbent assay (ELISA) and real time polymerase chain reaction (RT-PCR) that ZnO can induce the function of Th1, Th2 cells and expressions of insulin receptors and other genes of the pancreas associated with diabetes.

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Green synthesis of zinc oxide nanoparticles using Hibiscus subdariffa leaf extract: effect of temperature on synthesis, anti-bacterial activity and anti-diabetic activity

A single-step synthesis of copper oxide nanoparticles (CuO NPs) from a phenolic compound (rosmarinic acid) at ambient temperature was developed in this study. The physico-chemical properties of the synthesized particles were characterized by different instruments (UV-visible; ultra-violet spectroscopy, XRD; X-ray diffraction, FTIR; Fourier transformed infrared resonance, FESEM; field emission scanning electron microscope equipped with EDS; energy dispersive spectroscopy and TEM; transmission electron microscope), which revealed the good crystallinity with homogeneous distribution (30 ± 5 nm) of CuO NPs on the surface. The applicability of the nanoparticles as an anti-bacterial agent against Gram-negative (E. coli) and Gram-positive (S. aureus) bacterial strain was determined by bactericidal kinetics study. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values as determined by a batch culture process that exhibited a considerably low amount of copper content are capable of enhancing the anti-microbial efficacy. The cyto-compatibility of the CuO NPs was investigated by cell viability (MTT) and proliferation of mammalian fibroblast cell line experiments. The underlying mechanisms behind the anti-microbial activity and cell death were also studied by inner membrane permeabilization assay (β-galactosidase assay), intracellular ROS measurement, fluorescence images and cell wall degradation by FESEM. Significant photocatalytic activity of CuO NPs was observed through the degradation of methylene blue (MB) and para-nitrophenol (PNP) under visible light exposure conditions. The phenolic compound-assisted CuO NPs have the advantages of being environmentally benign with a beneficial and single-step synthesis approach that can be further used for various biomedical and waste water treatment purposes.

Phenolic compound-mediated single-step fabrication of copper oxide nanoparticles for elucidating their influence on anti-bacterial and catalytic activity

Background To find association between prostate gland volume to components of the metabolic syndrome. Methods Cross-sectional, observational study in a tertiary care hospital of the Armed Forces of India. A total of 115 male patients aged 50–65 years attending the Urology OPD between Jan 2014 and July 2015 with lower urinary tract symptoms (LUTS) were included. Men with known malignant disease including carcinoma prostate, those on medical management for BPH and individuals with previous history of surgery related to urinary bladder/prostate were excluded. Blood Pressure (BP), weight in kgs, height, waist and hip circumference to nearest cm were recorded. Body Mass Index (BMI) and Waist/Hip ratio (WHR) were calculated. Fresh serum was analysed for lipid profile and glycaemic levels. The International Diabetes Federation (IDF) – 2005 guideline for metabolic syndrome was used for the diagnosis. The total prostate volume and the severity of LUTS as per AUA Symptom index were considered as the primary and secondary outcome measure respectively. Statistical software SPSS version 20 was used for analysis. Mean prostate volume was compared with the components of MetS. An alpha level of 5% was considered significant. Results The study showed positive association between prostate volume with metabolic syndrome and its four components – raised blood pressure, fasting blood glucose and triglycerides and HDL ≤ 40 mg/dl. No correlation was found with waist circumference. Conclusion Our study indicates that metabolic syndrome and its individual components may predispose patients to a higher risk of prostatic enlargement/LUTS.

Association between components of metabolic syndrome and prostatic enlargement: An Indian perspective.

The importance of pKa in an analysis of the interaction of compounds with DNA.

In situ reactivity of electrochemically generated nitro radical anion on Ornidazole and its monomeric Cu(II) complex with nucleic acid bases and calf thymus DNA

Promita Nandy

Papers

Green synthesis of zinc oxide nanoparticles using Hibiscus subdariffa leaf extract: effect of temperature on synthesis, anti-bacterial activity and anti-diabetic activity

Phenolic compound-mediated single-step fabrication of copper oxide nanoparticles for elucidating their influence on anti-bacterial and catalytic activity

Association between components of metabolic syndrome and prostatic enlargement: An Indian perspective.

The importance of pKa in an analysis of the interaction of compounds with DNA.

In situ reactivity of electrochemically generated nitro radical anion on Ornidazole and its monomeric Cu(II) complex with nucleic acid bases and calf thymus DNA