In materials science, “green” synthesis has gained extensive attention as a reliable, sustainable, and eco-friendly protocol for synthesizing a wide range of materials/nanomaterials including
 metal/metal oxides nanomaterials, hybrid materials, and bioinspired materials. As such, green synthesis is regarded as an important tool to reduce the destructive effects associated with the traditional methods of synthesis for nanoparticles commonly utilized in laboratory and industry. In this review, we summarized the fundamental processes and mechanisms of “green” synthesis approaches, especially for metal and metal oxide [e.g., gold (Au), silver (Ag), copper oxide (CuO), and zinc oxide (ZnO)] nanoparticles using natural extracts. Importantly, we explored the role of biological components, essential phytochemicals (e.g., flavonoids, alkaloids, terpenoids, amides, and aldehydes) as reducing agents and solvent systems. The stability/toxicity of nanoparticles and the associated surface engineering techniques for achieving biocompatibility are also discussed. Finally, we covered applications of such synthesized products to environmental remediation in terms of antimicrobial activity, catalytic activity, removal of pollutants dyes, and heavy metal ion sensing.

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‘Green’ synthesis of metals and their oxide nanoparticles: applications for environmental remediation

A systematic review on silver nanoparticles-induced cytotoxicity: Physicochemical properties and perspectives.

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

Biogenic synthesis of nanoparticles: A review

The green synthesis of nanoparticles (NPs) using living cells is a promising and novelty tool in bionanotechnology. Chemical and physical methods are used to synthesize NPs; however, biological methods are preferred due to its eco-friendly, clean, safe, cost-effective, easy, and effective sources for high productivity and purity. High pressure or temperature is not required for the green synthesis of NPs, and the use of toxic and hazardous substances and the addition of external reducing, stabilizing, or capping agents are avoided. Intra- or extracellular biosynthesis of NPs can be achieved by numerous biological entities including bacteria, fungi, yeast, algae, actinomycetes, and plant extracts. Recently, numerous methods are used to increase the productivity of nanoparticles with variable size, shape, and stability. The different mechanical, optical, magnetic, and chemical properties of NPs have been related to their shape, size, surface charge, and surface area. Detection and characterization of biosynthesized NPs are conducted using different techniques such as UV-vis spectroscopy, FT-IR, TEM, SEM, AFM, DLS, XRD, zeta potential analyses, etc. NPs synthesized by the green approach can be incorporated into different biotechnological fields as antimicrobial, antitumor, and antioxidant agents; as a control for phytopathogens; and as bioremediative factors, and they are also used in the food and textile industries, in smart agriculture, and in wastewater treatment. This review will address biological entities that can be used for the green synthesis of NPs and their prospects for biotechnological applications.

Green Synthesis of Metallic Nanoparticles and Their Prospective Biotechnological Applications: an Overview

Green synthesis of silver nanoparticles using polysaccharides extracted from marine macro algae.

Green synthesis of nanoparticles that have environmentally acceptable solvent systems and eco-friendly reducing agents is of great importance. The aim of this work was to synthesis of silver nanoparticles (AgNPs) using water soluble polysaccharides extracted from four marine macro-algae, namely, Pterocladia capillacae (Pc) , Jania rubins (Jr) , Ulva faciata (Uf) , and Colpmenia sinusa (Cs) as reducing agents for silver ions as well as stabilizing agents for the synthesized AgNPs. The formed Ag-NPs have been confirmed by UV–Vis spectroscopy, FTIR analysis and TEM. The resultant Ag-NPs colloidal solutions were applied to cotton fabrics in presence and absence of citric acid (CA) or a binder (B). The antimicrobial activity of the treated fabrics was evaluated. The results revealed that the antimicrobial activity depends on type of the fabric treatment, size of the synthesized Ag-NPs and the algal species used for polysaccharides extraction.

Green synthesis of silver nanoparticles using polysaccharides extracted from marine macro algae

work aims to synthesis of fast green biogenic silver nanoparticles (AgNPs) using the ethanolic extracts of three Terminalia spices, namely, T. catapa (T.C), T. bellarica (T.B) and T. mellurie (T.M). AgNPs formed was affirmed by using UV–visible spectrophotometer with the characteristic SPR (Surface Plasmon Resonance) band at 424-430nm and by using FT-IR (Fourier transform infrared spectroscopy) and TEM (transmission electron microscopy). Quantification of carbohydrates, total phenolic compounds, flavonoids, and protein contents of these extracts were appraised since these constituents have effective dual roles for AgNPs synthesis. That is, they reduce Ag+ ions to Ag˚ nanoparticles and thereafter they stabilize these particles. GC/MS analyses of these extracts were also done. The cotton fabrics treated with the synthesized AgNPs showed good antimicrobial and anti-inflammatory activities toward both Gram-positive (S. aureus ATCC 25923) and Gram-negative (E. coli ATCC 25922) bacteria.

https://ejchem.journals.ekb.eg/article_4211_8ea445093a6afc3a59ad340ada98a604.pdf

Anti-Inflammatory and Antibacterial Activities of Nanosilver-Treated Cotton Fabric Prepared From Ethanolic Extracts of Three Terminalia SpecieS

Abstract Nanotechnology has a real-world impact on every aspect of life. Many researchers have been drawn to the biosynthesis of gold and iron oxide nanoparticles (Au-NPs and SPIONS) because they have a wide range of life applications. In this work, a single-step environmentally friendly biosynthesis of Au-NPs and SPIONS is reported by reducing solutions of gold aureate and ferric chloride is reported for the first time using the hydroethanolic extract (HEE) of Salvia officinalis ( S. officinalis ), an edible plant found in Egypt. The phytochemicals present in HEE were responsible for the reduction as well as stabilization of these nanoparticles. Before using the HEE, it was phytochemically screened for its constituents. Qualitatively, the HEE was found to have comparable levels of phenolics, flavonoids, tannins, proteins, carbohydrates, terpenoids, steroids, and polysaccharides. Quantitatively, total phenolics (236.91 ± 2.15 mg GAE/g extract), flavonoids (91.38 ± 0.97 mg QE/g extract), tannins (101.60 ± 1.33 mg/g extract), proteins (284.62 ± 2.65 mg/g extract), carbohydrates (127.73 ± 1.68 mg/g extract), soluble sugars (52.3 ± 0.67 mg/g extract), and polysaccharides (75.43 ± 1.01 mg/g extract) were estimated. In addition, HPLC analysis revealed the identification of seven phenolic compounds [ferulic (67.26%), chlorogenic (3.12%), caffeic (3.11%), p- coumaric (1.13%), protocatechuic (0.65%), catechin (0.69%), rosmarinic (0.53%)] and three flavonoids [apigenin (5.29%), quercetin-7- O -glucoside (3.39%), and luteolin-7- O -rutinose (2.01%)]. The characterization of the biosynthesized NPs was confirmed by Fourier transform infrared (FT-IR) spectroscopy, UV–Vis absorption spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). In vitro cytotoxic studies showed that Au-NPs, SPIONS, and HEE have an inhibitory effect on the growth of human breast cancer (MCF-7) cells at an IC 50 of 6.53, 6.97, and 26.12 µg mL −1 , respectively, by comparison with the standard drug (Doxorubicin) effect (0.18 µg mL −1 ). 

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In vitro cytotoxicity against breast cancer using biogenically synthesized gold and iron oxide nanoparticles derived from the hydroethanolic extract of Salvia officinalis L

Abstract Digenea simplex ( D. simplex ), an Egyptian marine red macroalga, contains a diverse group of phytochemicals with unique bioactivities. At the same time, the synthesis of nanosuspension (NS) has received increasing interest to optimize the technological aspects of drugs. Thence, the main objective of this work was to use the chloroform extract (ChlE) of D. simplex to prepare its nanosuspension (ChlE-NS) formulation to increase its aqueous solubility, thereby improving its bioactivity. By using FTIR, GC/MS analysis, and phytochemical screening assays, the chemical profiling of ChlE was assessed. NS was prepared by the antisolvent precipitation technique using 1.5% w/v polyvinyl alcohol (PVA). A light microscope, FTIR, particle size distribution, polydispersity index (PDI), and zeta potential (ZP) measurements was used to characterize the prepared NS. Four cancer cell lines were used in the MTT experiment to investigate the anticancer potential of ChlE and ChlE-NS. An apoptotic mechanism was established using acridine orange/ethidium bromide (AO/EB) dual staining, DNA fragmentation, and increased caspase activity. ChlE and ChlE-NS were also evaluated as antioxidants using DPPH and ABTS free radical assays. The results showed that, when compared to ChlE, ChlE-NS had greater cytotoxic activity against the four cancer cell lines. However, results of antioxidant activity showed that ChlE-NS had an IC 50 of 36.86 ± 0.09 and 63.5 ± 0.47%, while ChlE had values of 39.90 ± 0.08 and 86.5 ± 0.8% in DPPH and ABTS assays, respectively. Based on the results of this research, D. simplex ChlE-NS may be an effective strategy for enhancing ChlE's cytotoxic and antioxidant activities. Graphical abstract 

https://link.springer.com/content/pdf/10.1007/s00449-022-02833-6.pdf

H. M. El-Rafie

Papers

Green synthesis of silver nanoparticles using polysaccharides extracted from marine macro algae.

Green synthesis of silver nanoparticles using polysaccharides extracted from marine macro algae

Anti-Inflammatory and Antibacterial Activities of Nanosilver-Treated Cotton Fabric Prepared From Ethanolic Extracts of Three Terminalia SpecieS

In vitro cytotoxicity against breast cancer using biogenically synthesized gold and iron oxide nanoparticles derived from the hydroethanolic extract of Salvia officinalis L

Enhancement of cytotoxic and antioxidant activities of Digenea simplex chloroform extract using the nanosuspension technique