Green synthesis and characterization of gold nanoparticles from South African plants and their biological evaluations
Elbagory, Abdulrahman Mohammed Mohammed Nagy
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The field of nanotechnology continues to offer solutions for biotechnologists whose target is to improve the quality of life by finding new therapies to combat diseases. Gold nanoparticles (AuNPs) have been showing great potentials in many biomedical applications. The antibacterial activity of the AuNPs presents a therapeutic option for conditions caused by bacterial infections such as chronic wounds. Also, these versatile particles can offer solutions in the treatments of infectious diseases and can also be exploited as “smart” vehicles to carry drugs, such as antibiotics, for improved efficiency. Moreover, the anti-inflammatory activity of AuNPs makes them useful in the management of prolonged inflammation caused by bacterial infections. The synthesis of AuNPs can be achieved by variety of physical and chemical methods that have been successfully applied in labs and industry. Nonetheless, the drawbacks of these “conventional” methods in terms of high cost, adverse health side effects and incompatibility with the ecosystem cannot be overlooked. Thus, new safer and more cost-effective protocols have been reported for the synthesis of AuNPs. Plants have provided alternate synthesis methods in which the reducing capabilities of the phytochemicals, found in the aqueous plant extracts, can be used to chemically synthesize AuNPs from gold precursors. The biosynthesis and characterization of AuNPs from the phytochemicals of several South African plants is investigated in this study. The study also reports the optimization of the AuNPs biosynthesis by varying reaction conditions such as temperature and plant extracts’ concentrations. Furthermore, the study highlights the wound healing activity of the AuNPs synthesized from selected plants by investigating their antibacterial activity on bacterial strains known to cause chronic wounds. The ability of these AuNPs to carry ampicillin in order to enhance the antibacterial activity is also described herein. The cytotoxicity of the biosynthesized AuNPs was evaluated on human normal fibroblasts cells (KMST-6). Additionally, the immunomodulatory effect of the biosynthesized AuNPs on the cytokines production from macrophages and Natural Killer (NK) cells was examined. The study was successful to produce biocompatible and safe AuNPs synthesized from the tested aqueous plant extracts. The resulted AuNPs showed different physicochemical properties by varying the reaction conditions. The AuNPs exhibited antibacterial activity against several Gram-positive and Gram-negative bacteria. Also, ampicillin was successfully loaded on the biosynthesized AuNPs, which led to the formation of more antibacterial active conjugated AuNPs compared to the free AuNPs. The green synthesized AuNPs were also found to have anti-inflammatory responses as shown by the reduction of pro-inflammatory cytokines from immune cells. In vitro assays showed that the biogenic AuNPs were not toxic to KMST-6 cells. Overall, the data suggest that plant extracts produce biologically safe AuNPs with antibacterial and anti-inflammatory activities that can be exploited in the treatment of chronic wounds and in the management of chronic inflammation.