We have investigated the time-dependent effect of multi-walled carbon nanotubes (MWCNTs) in rats upon single inhalation exposure followed by intermittent sacrifice. The effects were monitored by analyzing the bronchoalveolar lavage fluid (BALF) and histopathological analysis. Cell count, neutrophils, lymphocytes, lactate dehydrogenase, alkaline phosphatase, protein and cytokines (tumor necrosis factor-alpha (TNF-α) and interleukin 4 (IL-4)) were significantly increased, while cell viability and alveolar macrophage count significantly decreased in the BALF of MWCNT-treated rats on day 1, day 7 and day 14 post-exposure, when compared to control rats. Histopathological analysis revealed inflammation, fibrosis and granuloma in the lungs of MWCNTs-treated rats on day 7 and day 14 post-exposure. We interpret that MWCNT induces inflammation, fibrosis and granuloma characterized by progressive elevation of TNF-α and IL-4. Histopathological studies further support our view and reveal the distribution of MWCNT in lungs and tracheobronchial lymph nodes (TBLN). We conclude that MWCNT-induced pulmonary toxicity is considerable even on single exposure.

Novel eco-friendly methods for the synthesis of metal nanoparticles are preferred and have recently been widely researched. In this study, a cost-effective and environmentally friendly method for the synthesis of gold nanoparticles was investigated. Costus pictus , also known as insulin plant due to its antidiabetic activity, was used as the reducing agent. Chloroaurate ions were rapidly reduced by the methanolic extract of Costus pictus , which was indicated by the color change from yellow to ruby red. The presence of a peak at 530 nm in UV-visible spectrophotometry confirmed the reduction of chloroaurate to gold nanoparticles. The reaction kinetics and effects of time, temperature, concentration of extract and substrate were also studied. The size and morphology of gold nanoparticles were analyzed using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) and they were found to be cuboidal, with a size of around 20 nm. The size of the particles was also analyzed by the particle size analyzer, and was found to be 45 nm. These particles were functionalized with bisdemethoxycurcumin analog (BDMCA). X-ray diffraction (XRD) analysis of prepared nanoparticles showed that the gold nanoparticles have a face centered cubic structure and that of functionalized nanoparticles showed peaks similar to that of BDMCA. Fourier transform infrared spectroscopy (FTIR) studies revealed the presence of reducing groups in the plant methanolic extract and the functionalization of nanoparticles with BDMCA was also confirmed. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that, the BDMCA-functionalized gold nanocubes possess anticancer activity. The mechanism of action is discussed.