Abstract
The application of hazardous chemicals during nanoparticle (NP) synthesis has raised alarming concerns pertaining to their biocompatibility and equally to the environmental harmlessness. In the recent decade, nanotechnological research has made a gigantic shift in order to include the natural resources to produce biogenic NPs. Within this approach, researchers have utilized marine resources such as macroalgae and microalgae, land plants, bacteria, fungi, yeast, actinomycetes, and viruses to synthesize NPs. Marine macroalgae (brown, red, and green) are rich in polysaccharides including alginates, fucose-containing sulfated polysaccharides (FCSPs), galactans, agars or carrageenans, semicrystalline cellulose, ulvans, and hemicelluloses. Phytochemicals are abundant in phenols, tannins, alkaloids, terpenoids, and vitamins. However, microorganisms have an abundance of active compounds ranging from sugar molecules, enzymes, canonical membrane proteins, reductase enzymes (NADH and NADPH), membrane proteins to many more. The prime reason for using the aforesaid entities in the metallic NPs synthesis is based on their intrinsic properties to act as bioreductants, having the capability to reduce and cap the metal ions into stabilized NPs. Several green NPs have been verified for their biocompatibility in human cells. Bioactive constituents from the above resources have been found on the green metallic NPs, which has demonstrated their efficacies as prospective antibiotics and anti-cancer agents against a range of human pathogens and cancer cells. Moreover, these NPs can be characterized for the size, shapes, functional groups, surface properties, porosity, hydrodynamic stability, and surface charge using different characterization techniques. The novelty and originality of this review is that we provide recent research compilations on green synthesis of NPs by marine macroalgae and other biological sources (plant, bacteria, fungi, actinomycetes, yeast, and virus). Besides, we elaborated on the detailed intra- and extracellular mechanisms of NPs synthesis by marine macroalgae. The application of green NPs as anti-bacterial, anti-cancer, and popular methods of NPs characterization techniques has also been critically reviewed.
Highlights
Sabiha Mahmood Ansari,1 Quaiser Saquib,2 Valeria De Matteis,3 Hend Awad Alwathnani,1 Sulaiman Ali Alharbi,1 and Abdulaziz Ali Al-Khedhairy2
Microorganisms have an abundance of active compounds ranging from sugar molecules, enzymes, canonical membrane proteins, reductase enzymes (NADH and NADPH), membrane proteins to many more. e prime reason for using the aforesaid entities in the metallic NPs synthesis is based on their intrinsic properties to act as bioreductants, having the capability to reduce and cap the metal ions into stabilized NPs
These NPs can be characterized for the size, shapes, functional groups, surface properties, porosity, hydrodynamic stability, and surface charge using different characterization techniques. e novelty and originality of this review is that we provide recent research compilations on green synthesis of NPs by marine macroalgae and other biological sources
Summary
NPs can be synthesized by two fundamental approaches: the top-down and the bottom-up approaches (Figure 2). Within the top-down approach, NPs are generated by slicing the size of their bulk counterpart employing several physical and chemical methods [48]. E top-down approach can be achieved using the microfabrication techniques, where external tools are applied to precisely cut, mill, and change the material into a desired size and structure [33, 49]. The prime focus in these methods was to synthesize NPs of varying sizes with different chemical compositions, monodispersion, and specific morphologies [64, 65]. In both approaches (top-down and bottom-up), the NPs synthesis is achieved by kinetic processes, which help determine the size and shapes of NPs (Figure 2). The color change of the reaction solution serves as a strong indicator of NPs synthesis
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