Silver nanoparticles are one of the most extensively studied nanomaterials due to their high stability and low chemical reactivity in comparison to other metals. They are commonly synthesized using toxic chemical reducing agents which reduce metal ions into uncharged nanoparticles. However, in the last few decades, several efforts were made to develop green synthesis methods to avoid the use of hazardous materials. The natural biomolecules found in plants such as proteins/enzymes, amino acids, polysaccharides, alkaloids, alcoholic compounds, and vitamins are responsible for the formation of silver nanoparticles. The green synthesis of silver nanoparticles is an eco-friendly approach, which should be further explored for the potential of different plants to synthesize nanoparticles. In the present review we describe the green synthesis of nanoparticles using plants, bacteria, and fungi and the role of plant metabolites in the synthesis process. Moreover, the present review also describes some applications of silver nanoparticles in different aspects such as antimicrobial, biomedicine, mosquito control, environment and wastewater treatment, agricultural, food safety, and food packaging.

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Background Toxoplasmosis remains widely distributed globally and is one of the major neglected parasitic zoonotic infections. The infection is still endemic in most parts of the world due to poor control as well as challenges of the currently used medications which can be overcome by using natural products. This study evaluated the effect of ethanolic extract from the stem of Tinospora crispa (EETC) on host cell invasion and intracellular replication of Toxoplasma gondii. Method The stem powder of T. crispa was soaked in absolute ethanol for 72 hours. The resulting ethanolic extract was screened for the presence of phytochemicals. Vero cells monolayer in 96-well plate was infected with RH strain of T. gondii and treated with concentrations of the EETC, Veratrine alkaloid, and clindamycin ranging from 1.56 to 200 μg/mL. MTT assay was conducted after 24 hours to evaluate the cytotoxicity and antiparasitic activities of the EETC. Four and 24 hours treatment models were adapted to assess the infection index and intracellular proliferation of T. Results The study revealed that the EETC had no cytotoxic effects on Vero cells with IC50 = 179 μg/mL, as compared to clindamycin (IC50 = 116.5 μg/mL) and Veratrine alkaloid (IC50 = 60.4 μg/mL). The EETC had good anti-toxoplasma activities with IC50 = 6.31 μg/mL in comparison with clindamycin (IC50 = 8.33 μg/mL) and Veratrine alkaloid (IC50 = 14.25 μg/mL). The EETC caused more than 70% and 80% reduction in infection index and intracellular proliferation in both treatment models, respectively. Conclusion This in vitro study showed that the EETC contains promising phytochemicals effective against T. gondii and safe to the host cells.