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

Silver nanoparticles (AgNPs) have been one of the most attractive nanomaterials in biomedicine due to their unique physicochemical properties. In this paper, we review the state-of-the-art advances of AgNPs in the synthesis methods, medical applications and biosafety of AgNPs. The synthesis methods of AgNPs include physical, chemical and biological routes. AgNPs are mainly used for antimicrobial and anticancer therapy, and also applied in the promotion of wound repair and bone healing, or as the vaccine adjuvant, anti-diabetic agent and biosensors. This review also summarizes the biological action mechanisms of AgNPs, which mainly involve the release of silver ions (Ag+), generation of reactive oxygen species (ROS), destruction of membrane structure. Despite these therapeutic benefits, their biological safety problems such as potential toxicity on cells, tissue, and organs should be paid enough attention. Besides, we briefly introduce a new type of Ag particles smaller than AgNPs, silver Angstrom (A, 1 A = 0.1 nm) particles (AgAPs), which exhibit better biological activity and lower toxicity compared with AgNPs. Finally, we conclude the current challenges and point out the future development direction of AgNPs.

Silver nanoparticles: Synthesis, medical applications and biosafety

Nanoparticle biosynthetic discipline is still under development and is known to have a big impact on numerous manufactures for a long time. Nowadays, biosynthesis of silver nanoparticles (AgNPs) had gained so much attention in developed countries due to development demand of environmental friendly technology for material synthesis. The use of green chemistry is environmental friendly, non-toxic, and cheap. This review focused on the recent scientific publications in the green synthesis field of AgNPs and its applications. A number of microorganisms including bacteria, fungi, yeasts, algae, and plants either intra- or extracellular have been found to be capable of synthesizing AgNPs. All scientific reports reflect the unique properties AgNPs possess that find myriad applications such as antibacterial, antifungal, antivirus, and anticancer drugs, larvicidal excellent catalytic natural action towards degradation of dyes, very good antioxidants, treatment of diabetes-related complications, and wound healing activities. The recent strategy for improving the efficacy of antibiotics is to combine them with AgNPs in order to control the microbial infections as confirmed by the damage action of AgNPs on microbial deoxyribonucleic acid. This review describes also the microorganism/plant extract and the reaction parameters used in synthesis of the AgNPs, which hold prominent impact on their size, shape, and application. Recently published information on AgNP synthesis and its applications are summarized in this review.

Recent Advances in Green Synthesis of Silver Nanoparticles and Their Applications: About Future Directions. A Review

Nanoparticles (NPs) are new inspiring clinical targets that have emerged from persistent efforts with unique properties and diverse applications. However, the main methods currently utilized in their production are not environmentally friendly. With the aim of promoting a green approach for the synthesis of NPs, this review describes eco-friendly methods for the preparation of biogenic NPs and the known mechanisms for their biosynthesis. Natural plant extracts contain many different secondary metabolites and biomolecules, including flavonoids, alkaloids, terpenoids, phenolic compounds and enzymes. Secondary metabolites can enable the reduction of metal ions to NPs in eco-friendly one-step synthetic processes. Moreover, the green synthesis of NPs using plant extracts often obviates the need for stabilizing and capping agents and yields biologically active shape- and size-dependent products. Herein, we review the formation of metallic NPs induced by natural extracts and list the plant extracts used in the synthesis of NPs. In addition, the use of bacterial and fungal extracts in the synthesis of NPs is highlighted, and the parameters that influence the rate of particle production, size, and morphology are discussed. Finally, the importance and uniqueness of NP-based products are illustrated, and their commercial applications in various fields are briefly featured.

/pdf/metal-nanoparticles-fabricated-by-green-chemistry-using-3mk4d9a8qf.pdf

Metal nanoparticles fabricated by green chemistry using natural extracts: biosynthesis, mechanisms, and applications

Silver nanoparticles: An integrated view of green synthesis methods, transformation in the environment, and toxicity.

Silver has been recognized as a nontoxic, safe inorganic antibacterial/antifungal agent used for centuries. Silver demonstrates a very high potential in a wide range of biological applications, more particularly in the form of nanoparticles. Environmentally friendly synthesis methods are becoming more and more popular in chemistry and chemical technologies and the need for ecological methods of synthesis is increasing; the aim is to reduce polluting reaction by-products. Another important advantage of green synthesis methods lies in its cost-effectiveness and in the abundance of raw materials. During the last five years, many efforts were put into developing new greener and cheaper methods for the synthesis of nanoparticles. The cost decrease and less harmful synthesis methods have been the motivation in comparison to other synthesis techniques where harmful reductive organic species produce hazardous by-products. This environment-friendly aspect has now become a major social issue and is instrumental in combatting environmental pollution through reduction or elimination of hazardous materials. This review describes a brief overview of the research on green synthesis of silver metal nanoparticles and the influence of the method on their size and morphology.

https://downloads.hindawi.com/journals/amse/2015/682749.pdf

A Review on the Green Synthesis of Silver Nanoparticles and Their Morphologies Studied via TEM

Nanoparticles are mainly synthesized by chemical methods that usually involve toxic reactants as reducing agents that further produce toxic by-products, which in turn are hazardous to the environment. During the last decade, the development of eco-friendly alternative chemical methods based on microorganisms like bacteria or fungi, or more recently biological molecules extracted from plants, have spurred a lot of interest as it brings forward a solution to curb the production of toxic by-products. The purpose of these investigations is to combine the natural biocidal properties of nanoparticles with specific properties derived from plant extracts, not limited to anti-inflammatory or anti-cancer properties. The development of antibacterial/antifungal coatings based on nanoparticles exhibiting biocidal properties offers a method to overpower multi-drug resistant bacteria. Metal oxide nanoparticles (TiO2, ZnO, and MgO) and noble metal nanoparticles like Ag, Au, and Pt have shown efficient biocidal properties against microorganisms. However, these mechanisms are still not fully understood and moreover, depend on the type of nanoparticles. Antibacterial activity of metal oxide nanoparticles is mainly attributed to the production of reactive oxygen species whereas metal nanoparticles interact with surface membranes and are capable of infiltrating into bacteria whereupon they induce apoptosis. Here, the mechanism of preventing bacterial growth is different from conventional antibiotics and offers a promising alternative.

Plant extract mediated synthesis of nanoparticles

We report on the study of surfactant-free silver nanoparticles synthesized using non-hydrolytic sol–gel methods for applications in straw bale constructions. Micro-organism infestation in green constructions is of concern as their proliferation tends to induce health problems. We demonstrate the biocidal properties of these Ag nanoparticles and their efficacy against fungi. Outdoor tests with Ag nanoparticles have demonstrated the effective protection of straw against micro-organisms. Indoor tests using broth liquid are compared with a method of testing we recently developed where the possible nature of the biocidal properties of the silver nanoparticles are further probed. In contrast to the commonly reported results, this study shows that Ag nanoparticles synthesized using non-hydrolytic sol–gel methods have antifungal properties against common fungi in outdoor conditions which demonstrate high potential in related applications.

/pdf/biocidal-properties-study-of-silver-nanoparticles-used-for-wz1jwp1ufs.pdf

Biocidal properties study of silver nanoparticles used for application in green housing

Silver nanoparticles synthesized through plant-mediated synthesis have recently gained recognition in the field of biocidal coatings. However, the accurate control of the synthesis using plant extract appears difficult and tends to produce a silver chloride secondary phase. In this study, 2 different methods of synthesis using the same plant extract of Plantago major have been investigated to evaluate their influence on the production of AgCl. In both cases the silver nanoparticles have demonstrated efficient biocidal properties against micro-organisms.

Optimisation of plant mediated synthesis of silver nanoparticles by common weed Plantago major and their antimicrobial properties

This work presents a method that enables the cheap production of surfactant-free stable metal nanoparticles in air. The silver nanoparticles are good candidates for new applications in green housing. Recently, we demonstrated usage of air-stable silver MNPs as biocidal coatings instead of chemical agents for protection of straw bales used in a green housing construction. Application of the silver nanoparticles as antifungal agents needs a method that does not neutralize their biocidal properties as a result of the testing method. In this study, we discuss the usual methods that are used for the antibacterial property testing and the development of a method that allows demonstrating the antifungal properties of metal nanoparticles.

Siim Küünal

Papers

A Review on the Green Synthesis of Silver Nanoparticles and Their Morphologies Studied via TEM

Plant extract mediated synthesis of nanoparticles

Biocidal properties study of silver nanoparticles used for application in green housing

Optimisation of plant mediated synthesis of silver nanoparticles by common weed Plantago major and their antimicrobial properties

New Methodology for the Antifungal Testing of Surfactant-Free Silver Metal Nanoparticles for Applications in Green Housing