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Carbon nanotubes (CNTs) hold tremendous potential due to their unique and modifiable properties. Their robust biological applications necessitate minimizing their cytotoxicity and increasing the solubilization. In the present manuscript, we have functionalized multiwalled carbon nanotubes (MWCNTs) using defect functionalization methodology to covalently bind carboxy and amino groups on their walls. This functionalization was reassured through fourier-transform infrared spectroscopy (FTIR), energy dispersive x-ray analysis (EDX), elemental and field emission scanning electron microscopy (FE-SEM) analysis. The observations demonstrated that addition of carboxy as well as amino groups on MWCNTs, besides enabling MWCNTs solubilization also significantly ameliorated the cytotoxicity and the oxidative stress in comparison to pristine MWCNTs. It is envisaged that changes in agglomeration of the functionalized MWCNTs and the acquired surface charge is the reason for the reduction of cytotoxicity. Zebra fish embryo model test system employed for in vivo analysis of the MWCNTs showed no significant toxicity on account of any nanoparticle tested pointing towards intrinsic mechanisms in place for deterring the damage in complex organisms. Overall, the observations besides pointing towards functionalized MWCNTs effectiveness towards weakening the toxicity of pristine MWCNTs also caution for extrapolating in vitro data to in vivo observations. The observations further lend credibility for exploiting the zebra fish as a model system for analyzing the effects of MWCNTs functionalization.

Metal and metal oxide nanoparticles are being used in different industries now‐a‐days leading to their unavoidable exposure to humans and animals. In the present study, toxicological testing was done using nanoparticles of copper oxide, cerium oxide and their mixture (1:1 ratio) on zebra fish embryos and THP‐1 cell line. Zebrafish embryos were exposed to 0.01 μg/ml to 50 μg/ml concentrations of dispersed nanoparticles using a 96 well plate and their effects were studied at different hours post fertilization (hpf) i.e. 0 hpf, 24 hpf, 48 hpf, 72 hpf and 96 hpf respectively. Results showed that copper oxide nanoparticles has drastic effects on the morphology and physiology of zebra fish whereas cerium oxide nanoparticles and mixture of these nanoparticles did not show much of the effects. Comparable results were obtained from in vitro study using human monocyte cell line (THP‐1). It is concluded that these nanoparticles may cause toxicological effects to humans and environment.

Marine oil spills and petrochemical discharges occurring either naturally or deliberately can have destructive impacts on environment and economy of a nation. Water bodies contaminated by oil pose challenge to the survival of aquatic biodiversity. Nanotechnology is offering new potential routes to remediate the oil pollution. In the present study, a superparamagnetic nanocomposite of Fe 3 O 4 /chitosan was synthesised using co-precipitation method. The prepared material was characterized to determine chemical structure, morphology, shape and size, thermal and magnetic properties. The magnetic adsorbent was employed for the adsorptive removal of petroleum based diesel oil from oil-in-water emulsions. The efficiency of the synthesized nanocomposite was examined by batch adsorption experiments to determine the effect of pH, adsorption time and adsorbent dose on the oil removal process. From the experimental data, it was found that the adsorption process followed the pseudo second order kinetics (R 2 = 0.9962) and Langmuir isotherm (R 2 = 0.9998) indicating towards a monolayer chemisorption process. Thermodynamic parameters showed that the adsorption was spontaneously endothermic (ΔH = + 38.779 kJ/ mol) and the nanocomposite was found to be recyclable up to least five cycles of oil-water separation. The optimization of oil removal process was carried out using response surface methodology (RSM) as function of four factors consisting of pH, adsorbent dose, stirring speed and adsorption time. The study provides the basis for development of an eco-friendly and promising material for treatment of oil and hydrocarbon pollution from water bodies in environmental clean-up.