Assessment of FeO and MnO Nanoparticles Toxicity on Chlorella pyrenoidosa

Nowadays, nanometal oxides are commonly applied in diverse industries like food, medicine and cosmetics. The enormous utilization of nanoparticles may cause toxic effects in the environment. Hence, it is very essential to evaluate its fate in the environment. In this study, ecotoxicity of nano and micro metal oxides, namely Iron oxide (FeO) and Manganese oxide (MnO), on the growth of algae (Chlorella pyrenoidosa) is being discussed. Standard procedures were used to analyze their toxicity in respect of growth, total chlorophyll and protein contents. Outcome of this study reveals non toxic nature of FeO nano and micro particles on C. pyrenoidosa up to a concentration of 1000 mg/L. However, MnO nanoparticles are less toxic while MnO microparticles exert high toxicity at 1000 mg/L by decreasing the growth, chlorophyll and protein contents of the tested algae. This study also explores the nano-toxicity with respect to hydrophobicity and surface charge. The positive zeta potential of algal cells reveals their electrostatic interaction with the negative MnO particles, which may result in deposition of the particles on the surface of algal cells, resulting in cell death. In addition, MnO particles exhibit less contact angle (more hydrophilic) both in nano and micro form compared to FeO particles. The study reveals that MnO particles render more toxicity towards C. pyrenoidosa compared to FeO particles. The present investigation drives an innovative insight on toxicity of metal oxide particles on algae.