Toxicity of N-Nitrosodimethylamine and SiO2 nanoparticles to HaCaT and caco-2 cell lines found in waste water treatment

Abstract

Nanoparticles (NPs) offer the possibility of safe removal of pollutants and microbes in water treatment and purification. Nowadays, NPs are used in the detection and purification of water from chemicals and biological substance such as metals (cadmium, copper, lead and zinc) nutrients (nitrate, nitrite ammonia and phosphate) bacteria, viruses, parasite and antibiotics. Metal containing NPs are among the four classes of particles used commonly in water treatment. Membrane technologies such as Ultrafiltration (UF), Nanofiltration (NF) and Reverse Osmosis (RO) have been widely used all over the world especially for water treatment and desalination. NPs after have been incorporated into membranes gained attention due to its ability to enhance membrane permeability, mechanical properties and selectivity in some cases. However, these membranes are suspected to fouling causing NPs and other contaminate to reach waterways. In this study, we tested the toxicity of SiO 2 NPs synthesised by Stöber method and N-Nitrosodimethylamine (NDMA) as potent known carcinogens forms during chlorination on HaCaT and caco-2 cell lines for 4, 24 and 48h using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays also the morphology and size of SiO 2 determined by Scanning electron microscopy (SEM). After exposure to SiO 2 NPs (concentrations between 0.05-2 mg/mL), the concentration of 2 mg/mL inactivated LDH in both cell lines; however, it did not reduce the metabolic activity of both cell lines when MTT assay used. SEM revealed spherical and uniformed SiO 2 particles with size 200 nm in diameter. NDMA (concentrations between 0.1-1000 µg/mL) inactivated LDH leakage in HaCaT and caco-2 also reduced the metabolic activity of HaCaT cell line at 48 hours exposure. The outcome of this study suggest that a concentration of SiO 2 <2 mg/mL used in water treatment can reduce the risk of nanmaterials toxicity to human and possibly the ecosystem. Our results urgefor more studies on the effect of nanomaterials to the aquatic environment and human exposure to NPs.