In this study, biosynthesis of silver nanoparticles (AgNPs) and its toxicity were investigated. Different functional groups responsible for adsorption, morphology and absorption of the nanoparticle were characterized using UV-Vis, Fourier transmission infrared spectroscopy (FTIR), and scanning electron microscope (SEM) analyses, respectively. The toxicity of orally administered Azadirachta indica AgNPs was assessed in Swiss albino rats. Sub-acute toxicity was determined in daily dosages from 30-0.3 mg/kg body weight for 28 days. Chronic toxicity was determined in two dosages 30 and 10 mg/kg body weight for 180 days. Control groups were included and were administered with distilled water. The UV-Vis spectroscopy showed surface plasmon resonance of 430 nm for the silver nanoparticle. The FTIR spectrum showed primary-N-H bond and secondary-C-N amides. The nanoparticles synthesized were 45 nm average sizes. There were no significant differences (P>0.05) observed between the packed cell volume (PCV), animals body weight of the control and treatment groups in sub-acute and chronic toxicity. Portal hepatitis in the liver at the 30 mg/kg b. wt was noted. Hence, histopathology examinations confirmed the liver damage noted in clinical biochemistry. Kidneys histological organization appeared normal generally with glomeruli and tubules visible. Our results demonstrate that A. indica silver nanoformulation may be safe at daily dosage of up-to 10 mg/kg b. wt. However, it indicates that the A. indica silver nanoformulation on daily use at 30 mg/kg may lead to liver damage.
Key words: Silver nanoparticles, toxicity, Azadirachta indica, rats.