Developing efficient green chemistry–based approaches for producing commercially sustainable quantities of metal nanoparticles has attracted considerable research interest in recent years. At the same time, there has also been significant interest shown toward developing sustainable eco-friendly practices and innovative strategies that can valorize plant-based food losses and wastes. Importantly, plant-based food waste is produced in extremely larger quantities and is also a renewable resource that is composed of many bioactive phytochemicals. The presence of large quantities of phytochemicals in plant-based food waste makes them attractive agents for the green synthesis of metal nanoparticles. This alternative green approach, besides being a potential waste valorization strategy, is also a method of reducing the dependence on hazardous chemicals and solvents commonly used in conventional manufacturing processes. The chapter summarizes and reviews published research articles in this relatively new and emerging field. It highlights and discusses the results of several studies carried out to investigate the potential use of plant-based food wastes to produce metal nanoparticles. Importantly, limitations preventing this green chemistry–based approach from being used as an alternative waste valorization strategy are also discussed.

Sustainable utilization of renewable plant-based food wastes for the green synthesis of metal nanoparticles

Nanotechnology has been gaining interest worldwide as a novel field of science and technology. The unique attribute of nanotechnology is that it transforms metals into nanolevel particles, which results in the overall change of its physical, chemical, and optical properties. Moreover, remarkable applications of nanotechnology in healthcare, cosmetics, food, biomedical sciences, environmental issues, and drug delivery are of paramount significance. However, studies are still at their infancy to explore the maximum potential of this robust technology. Although several studies have been carried out in diverse arenas of nanotechnology, much of the current research is challenged by setbacks due to safety issues, ecodestruction, and incompatibility in drug delivery applications. This chapter reviews the biosynthesis of nanoparticles employing different plant groups. It also discloses the particular methodologies devised by several researchers resulting in the phytoproduction of valuable nanomaterials and their applications at the molecular scale or cellular level. Moreover, this review also reveals the research gaps that must be bridged in the years to come to meet higher targets in the field of nanotechnology.

Green nanoparticles from different plant groups

Solanum tubersum is the fourth most challenging plant in Egypt, affected by several fungi, viral and bacterial diseases. Bacterial and fungal isolates (Brown rot disease (Ralstonia solaniserum), soft root disease (Pectobacterium carotovora) and dry rot disease (Fusarium oxisporum) were collected. The green extracts of silver nanoparticles were prepared by means of aqueous extracts of three wild plants, Physalis peruviana (leaves, red and green fruits) (N1, N2 and N3), Solanum nigrum (fruit) (N4) and Moringa oliefera (leaves) (N5). SEM, TEM, FT-IR and X-RD obtained the characterization of the biosynthesis of silver nanoparticles. The results indicated that nanoparticles were spherical, smooth and the sizes varied between 12 and 33 nm. The activity of the nanoparticle formulations was tested against the bacterial isolates using agar diffusion method and one fungus using mycelial growth method. The results also elucidated that N5 formulation showed a significantly potent antibacterial activity against R. solanacearum. However, N1 formulation was the highest active one against P. carotovra. In addition, the antifungal activity indicated that N1 had the highest effect (EC50 = 687.03 mg/L) followed by N3 (EC50 = 981.61 mg/L) against F. oxysporium. Nanoparticles synthesized by wild plants could be used as safe alternatives to harmful microbicides.

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Biosynthesis and Characterization of Silver Nanoparticles Produced by Plant Extracts and Its Antimicrobial Activity

Objective: Synthesize silver nanoparticles using a green synthesis approach and encapsulate silver nanoparticles with a naturally occurring polymer, particularly of an-hydroglucose type, like dextran sulfate sodium salt and to study its anticancer activity. \nMethods: Green synthesis approach is been employed in the synthesis of silver nanoparticles using Psidium guajava leaf extract. The nanoparticles were then encapsulated with dextran sulfate biopolymer and the nanoparticles were subjected to different characterization techniques. The structure of the synthesized nanoparticles was analyzed using X-ray diffraction analysis, the presence of different functional groups was analyzed by FTIR studies. Size and morphology of the prepared nanoparticles were investigated using FESEM analysis. Anticancer activity of the synthesized nanoparticles was tested against the MCF-cell line. \nResults: The XRD analysis shows the crystalline nature of the synthesized nanoparticles. The stretching and vibrating modes of different functional groups were confirmed by FTIR result. The SEM image confirmed the presence of spherical shaped nanoparticles and the TEM image confirmed the average size of the particles to be around 24 nm. The Ag-DS NPs showed 91% cell inhibition for the concentration of 100 μg/ml, indicating the cytotoxicity of the nanoparticles against MCF-7 cell line. \nConclusion: Dextran sulfate stabilized silver nanoparticles show potent anticancer activity against MCF-7 cell line.

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Dextran sulfate stabilized silver nanoparticle: next generation efficient therapy for cancer

Physico-chemical properties are crucial characteristics of hydrocolloids as they decide the applicability of them. Rheology of system, flow behaviour and mechanical properties make hydrocolloids suitable for food industry. Modification of consistency or texture properties of functional polymers also controls their sensory characteristics, thereby they become significant essences such as thickener, gelling agents, foaming agent, texture modifier, viscosifier, emulsifier, stabilizer and binder. Industrial and pharmaceutical applications are also controlled by some suitable physico-chemical properties of hydrocolloids. The polysaccharide gum exudates constitute a architecturally distinct class of complex biomacromolecules having unique physico-chemical properties. Due to their good bio/tissue compatibility, non-toxicity, they are extensively used in the field of tissue engineering, drug delivery and wound healing. Chemical and molecular architecture of hydrocolloids in turn controls their physico-chemical and functional properties. Sterculia gum is a substituted rhamnogalacturonoglycan (pectic) type exudate gum used as suspending agent, gelling agents, emulsifier, bulk laxative, dental adhesive, drug delivery agent and wound healing agent. It exhibits high water retention capacity, high viscosity and least solubility. Solutions of sterculia gum are viscoelastic and thixotropic. Sterculia gum has been recommended as effective wound dressing material as it can form a intensely adhesive gel when dispersed in minimum ammount of water. Owing to wide applications and distinctive properties of sterculia gum, present work is an endeavor to summarize the molecular organization, chemical configuration and physico-chemical properties of sterculia gum and the factors affecting physico-chemical properties of sterculia gum.

K. Jeganathan

Papers

Plant extract mediated synthesis of silver and gold nanoparticles and its antibacterial activity against clinically isolated pathogens B Biointerfaces