Toxic potential of green synthesized silver nanoparticles using Annona glabra leaf extract against Daphnia magna

Abstract

This study aims to evaluate the acute toxicity of biosynthetic AgNPs produced using Annona glabra leaf extract, against a selected aquatic-indicator, Daphnia magna. The toxicity of the biosynthetic AgNPs was compared against the Ag+ ion solution. Aqueous leaf extracts of A. glabra were prepared by heating chopped leaves (20.0 g) with water (100.0 mL) at 100 oc for 1 hour. AgNPs were synthesized by incubating the leaf extract of A. glabra (2 mL) with AgN03 solution (l mM, 20 mL) for 3 hours. The formed AgNPs were separated using centrifugation (6000 rpm, 20 minutes) and the separated AgNPs were freeze dried. AgNPs were Characterized by UV — visible Spectrometer, particle size analyzer and scanning electron microscopy. acute toxicity tests against D. magna were conducted according to the Organization for Economic Co-operation and Development (OECD) standard procedure using neonates aged less than 24 hours reproduced using parthenogenesis. D. magna neonates were exposed to solutions within the concentration range Of 0.01 — 10 mg/L Of AgNP solutions and concentration range Of 0.5 — 2 gg/L Of ion solutions for 48 hours. Tests were conducted in quadruplicate and 95% confidence interval was calculated. Biosynthesized AgNPs showed a plasmon resonance peak at 419 nm, were spherical in shape and the size ranged between 10 — 190 nm. The EC50 value against D. magna for Agt ions were 1.41 ± 0.2 gg/L and for AgNPs it was 3.96 ± 1.1 mg/L after 48 hours. Results obtained from this study suggests that the toxicity ofbiosynthetic A. glabra - AgNPs exerts lesser toxic effect to D. magna than the Agt ions.