Over the past few decades, metal nanoparticles less than 100 nm in diameter have made a substantial impact across diverse biomedical applications, such as diagnostic and medical devices, for personalized healthcare practice. In particular, silver nanoparticles (AgNPs) have great potential in a broad range of applications as antimicrobial agents, biomedical device coatings, drug-delivery carriers, imaging probes, and diagnostic and optoelectronic platforms, since they have discrete physical and optical properties and biochemical functionality tailored by diverse size- and shape-controlled AgNPs. In this review, we aimed to present major routes of synthesis of AgNPs, including physical, chemical, and biological synthesis processes, along with discrete physiochemical characteristics of AgNPs. We also discuss the underlying intricate molecular mechanisms behind their plasmonic properties on mono/bimetallic structures, potential cellular/microbial cytotoxicity, and optoelectronic property. Lastly, we conclude this review with a summary of current applications of AgNPs in nanoscience and nanomedicine and discuss their future perspectives in these areas.

https://www.mdpi.com/1422-0067/20/4/865/pdf

Silver Nanoparticles: Synthesis and Application for Nanomedicine

During the past few years, silver nanoparticles (AgNPs) became one of the most investigated and explored nanotechnology-derived nanostructures, given the fact that nanosilver-based materials proved to have interesting, challenging, and promising characteristics suitable for various biomedical applications. Among modern biomedical potential of AgNPs, tremendous interest is oriented toward the therapeutically enhanced personalized healthcare practice. AgNPs proved to have genuine features and impressive potential for the development of novel antimicrobial agents, drug-delivery formulations, detection and diagnosis platforms, biomaterial and medical device coatings, tissue restoration and regeneration materials, complex healthcare condition strategies, and performance-enhanced therapeutic alternatives. Given the impressive biomedical-related potential applications of AgNPs, impressive efforts were undertaken on understanding the intricate mechanisms of their biological interactions and possible toxic effects. Within this review, we focused on the latest data regarding the biomedical use of AgNP-based nanostructures, including aspects related to their potential toxicity, unique physiochemical properties, and biofunctional behaviors, discussing herein the intrinsic anti-inflammatory, antibacterial, antiviral, and antifungal activities of silver-based nanostructures.

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Biomedical Applications of Silver Nanoparticles: An Up-to-Date Overview

The acronym ESKAPE includes six nosocomial pathogens that exhibit multidrug resistance and virulence: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. Persistent use of antibiotics has provoked the emergence of multidrug resistant (MDR) and extensively drug resistant (XDR) bacteria, which render even the most effective drugs ineffective. Extended spectrum β-lactamase (ESBL) and carbapenemase producing Gram negative bacteria have emerged as an important therapeutic challenge. Development of novel therapeutics to treat drug resistant infections, especially those caused by ESKAPE pathogens is the need of the hour. Alternative therapies such as use of antibiotics in combination or with adjuvants, bacteriophages, antimicrobial peptides, nanoparticles, and photodynamic light therapy are widely reported. Many reviews published till date describe these therapies with respect to the various agents used, their dosage details and mechanism of action against MDR pathogens but very few have focused specifically on ESKAPE. The objective of this review is to describe the alternative therapies reported to treat ESKAPE infections, their advantages and limitations, potential application in vivo, and status in clinical trials. The review further highlights the importance of a combinatorial approach, wherein two or more therapies are used in combination in order to overcome their individual limitations, additional studies on which are warranted, before translating them into clinical practice. These advances could possibly give an alternate solution or extend the lifetime of current antimicrobials.

/pdf/emerging-strategies-to-combat-eskape-pathogens-in-the-era-of-mchli3dllg.pdf

Emerging Strategies to Combat ESKAPE Pathogens in the Era of Antimicrobial Resistance: A Review.

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.

/pdf/metal-based-nanoparticles-as-antimicrobial-agents-an-y9sfybpk7p.pdf

Metal-based nanoparticles as antimicrobial agents: an overview.

Since discovery of the first antibiotic drug, penicillin, in 1928, a variety of antibiotic and antimicrobial agents have been developed and used for both human therapy and industrial applications. However, excess and uncontrolled use of antibiotic agents has caused a significant growth in the number of drug resistant pathogens. Novel therapeutic approaches replacing the inefficient antibiotics are in high demand to overcome increasing microbial multidrug resistance. In the recent years, ongoing research has focused on development of nano-scale objects as efficient antimicrobial therapies. Among the various nanoparticles, silver nanoparticles have gained much attention due to their unique antimicrobial properties. However, concerns about the synthesis of these materials such as use of precursor chemicals and toxic solvents, and generation of toxic byproducts have led to a new alternative approach, green synthesis. This eco-friendly technique incorporates use of biological agents, plants or microbial agents as reducing and capping agents. Silver nanoparticles synthesized by green chemistry offer a novel and potential alternative to chemically synthesized nanoparticles. In this review, we discuss the recent advances in green synthesis of silver nanoparticles, their application as antimicrobial agents and mechanism of antimicrobial mode of action.

https://pubs.rsc.org/en/content/articlepdf/2019/ra/c8ra08982e

Green synthesis of silver nanoparticles: biomolecule-nanoparticle organizations targeting antimicrobial activity

Multidrug resistance of the pathogenic microorganisms to the antimicrobial drugs has become a major impediment toward successful diagnosis and management of infectious diseases. Recent advancements in nanotechnology-based medicines have opened new horizons for combating multidrug resistance in microorganisms. In particular, the use of silver nanoparticles (AgNPs) as a potent antibacterial agent has received much attention. The most critical physico-chemical parameters that affect the antimicrobial potential of AgNPs include size, shape, surface charge, concentration and colloidal state. AgNPs exhibits their antimicrobial potential through multifaceted mechanisms. AgNPs adhesion to microbial cells, penetration inside the cells, ROS and free radical generation, and modulation of microbial signal transduction pathways have been recognized as the most prominent modes of antimicrobial action. On the other side, AgNPs exposure to human cells induces cytotoxicity, genotoxicity and inflammatory response in human cells in a cell-type dependent manner. This has raised concerns regarding use of AgNPs in therapeutics and drug delivery. We have summarized the emerging endeavors that address current challenges in relation to safe use of AgNPs in therapeutics and drug delivery platforms. Based on research done so far, we believe that AgNPs can be engineered so as to increase their efficacy, stability, specificity, biosafety and biocompatibility. In this regard, three perspectives research directions have been suggested that include 1) synthesizing AgNPs with controlled physico-chemical properties, 2) examining microbial development of resistance towards AgNPs, and 3) ascertaining the susceptibility of cytoxicity, genotoxicity, and inflammatory response to human cells upon AgNPs exposure.

/pdf/mechanistic-basis-of-antimicrobial-actions-of-silver-1vmm44o6it.pdf

Mechanistic Basis of Antimicrobial Actions of Silver Nanoparticles.

Biological synthesis of silver nanoparticles by using Viola serpens extract

Tannin acyl hydrolase (E.C.3.1.1.20) universally known as tannase is an inducible enzyme that predominantly acts on tannins. Tannins have been documented as high molecular weight polyphenolic compounds possessing molecular weight in the range (500–3000 kDa). Tannins are the second most abundant polyphenolic compounds existing in nature after lignin. Tannins are water-soluble secondary metabolites existing in abundance in plants. Apparently, tannins exist in plants as the fourth most bountiful constituents behind cellulose, hemicellulose, and lignin. Tannins possess acrid properties and have the inherent capability of binding with proteins, cellulose, gelatin, and pectin thereby forming insoluble complexes. Tannases derived from microbial sources have enormous applications in various industries. This tremendous biocatalytic potential of tannase is attributed to their higher stability and feasibility. Tannases have a vast range of applications in various industrial bioprocesses ranging from food, feed to chemical as well as pharma sector. Furthermore, tannery effluents are loaded with surplus amount of tannins, predominantly polyphenols, which are life-threatening pollutants and pose severe environmental and health hazards. As a matter of fact, tannases can be substantially utilized for degrading the tannins that predominantly exist in the tannery effluents, thus offering a much cheaper treatment for the eviction of these compounds. The enzyme also finds significant utilization in cosmetic industries to so as to lessen the extensive turbidity of plant extracts. Tannase can also be predominantly used for high-grade leather tannins preparation in the leather industry. The present chapter is an attempt to emphasize on microbial sources, substrates for maximal tannase production, factors governing tannase production, mechanism of action, purification, immobilization, inhibitors as well as widespread applications of tannases. The advancements in molecular tools and techniques have enabled a better understanding of tannase structure, underlying mechanism of its action as well as the more precise understanding of various process parameters governing tannase production. Over the years, tannases have witnessed a significant rise in their utilization in commercial sector; thus, there is always an opportunity for researchers to search out novel tannases with better and improved characteristics.

Fungal Tannase: Recent Advances and Industrial Applications

Nanoparticles have been suggested as useful antibacterial and anti-plaque solutions for patients with dental caries. The purpose of this study was to compare the antimicrobial and antiplaque effects of silver nanoparticles synthesized by using Viola serpens plant. Furthermore, oral cavities are inhabited by both commensal and pathogenic bacterial species. In some conditions bacteria belonging to the indigenous or resident oral microorganisms can lead to infectious dental diseases. The total 40 samples were collected analyzed for the prevalence of Streptococcus mutans (S. mutans ) in dental plaque. Total recovered isolates were 32 out of which 18 S. mutans were isolated, and the prevalence of recovered isolates was found to be 45%. In the present investigation, the evaluation of efficacy of biologically synthesized silver nanoparticles against recovered isolates was performed using agar well diffusion method and were found to be moderately effective against the three strains of S. mutans in comparison to reference drug.

http://nopr.niscair.res.in/bitstream/123456789/44149/1/JSIR%2077%284%29%20225-228.pdf

In Vitro Efficacy of Biosynthesized AgNPs against Streptococcus mutans Causing Dental Plaque Formation

In the present scenario there is an urgent need to discover new antimicrobial agents for therapeutic use, as resistance to current drugs increase in severity and extent on the passage of time. Our research work was focused on the identification of natural products from leaves extracts of Morus nigra and Viola serpens in order to decipher the antibacterial activity against bacteria causing jaundice disease. Natural products based drugs are known as potential pharmacological agents. The Phytochemical screening of the plants studied showed the presence of Flavonoids, Terpenoids, reducing sugars, amino acids and tannins. In-vitro antibacterial activity was evaluated against strains isolated from patients suffering from jaundice i.e. Staphylococcus aureus, Pseudomonas aeruginosas, Salmonella typhi, Escherichia coli and Klebsiella pneumonia. Comparative study of Ethanolic extract of Viola serpens & Morus nigrawith standard antibiotics showed that Ethanolic extract of Viola serpens showed maximum antibacterial activity. Concerning the zone of inhibition, the values were merely higher for those caused by the plant extracts as compared to different antibiotics.

In - vitro antibacterial activity of ethanolic extracts of viola serpens and morus nigra against pathogens isolated from patients suffering from jaundice

Anu Kumar

Papers

Mechanistic Basis of Antimicrobial Actions of Silver Nanoparticles.

Biological synthesis of silver nanoparticles by using Viola serpens extract

Fungal Tannase: Recent Advances and Industrial Applications

In Vitro Efficacy of Biosynthesized AgNPs against Streptococcus mutans Causing Dental Plaque Formation

In - vitro antibacterial activity of ethanolic extracts of viola serpens and morus nigra against pathogens isolated from patients suffering from jaundice