Toxicity of Silver Nanoparticles Synthesized from Opuntia ficus-indica on Danio rerio and Arabidopsis thaliana and Their Antimicrobial Activity

Silver nanoparticles (AgNPs) usefulness has been widely demonstrated in fields such as agriculture, medicine, food, and pharmaceutical industries, primarily for their antibacterial properties. AgNPs synthesized from biological extracts are as effective as those obtained by chemical methods, with the advantage that in the former fewer toxic compounds are generated for the environment. In a previous work, we synthesized AgNPs from the aqueous extract of Opuntia ficus-indica fruit peel (OfAgNPs) and tested their activity against microorganisms from a wastewater treatment plant. OfAgNPs were proposed for use as tertiary wastewater treatment; however, more needs to be known about their antimicrobial activity and toxicological potential. In the present study, the antimicrobial effect of OfAgNPs was demonstrated against reference bacterial strains of Escherichia coli (DH5α), Pseudomonas aeruginosa (ATCC 27853), and Staphylococcus aureus (ATCC 29213), and against fungi isolated in the laboratory and identified as Aspergillus sp., Colletotrichum sp., and Cladosporium sp. In addition, in this work, we report the effects of OfAgNPs produced by exposure in two model organisms: a fish, Danio rerio, and a plant, Arabidopsis thaliana. OfAgNPs in A. thaliana caused negative effects on growth and photosynthetic pigment content only when the exposure was constant and greater than 6 mg/L. However, in D. rerio, impaired caudal fin development was observed at 0.15 mg/L from 24 hr of exposure. This is evidence of the toxicological potential of OfAgNPs, so their use should be carried out in a controlled manner.