ABSTRACT
Two-dimensional nanostructures have gained tremendous interest in the field of biomedical applications and cancer activity in particular. Although sulfur is known for its wide range of biological activities, its potentiality in two-dimensional forms as an antitumor agent is hitherto unexplored. To address the current deficient knowledge on nano-sulfur as an antitumor agent, we report the synthesis of nano-sulfur sheets/particles and their cytotoxic, apoptotic activity against human carcinoma cell lines. In vitro cytotoxic effects of biogenic nanosheets (SNP-B) and chemogenic nanoparticles (SNP-C) were assessed against human lung carcinoma (A549), human epidermoid carcinoma (A431), human promyelocytic leukaemia (HL60) and human lung fibroblast (IMR90) cell lines. Cell cycle analysis, apoptotic study, and caspase-3 expression studies were carried out to understand the mechanism of cytotoxic activity of nano-sulfur. The MTT assay indicated a dose-dependent decrease in viability of all the cell lines treated with nano-sulfur, with SNP-B being more toxic compared to SNP-C. The apoptotic study and cell cycle analysis indicated cell cycle arrest followed by apoptosis-induced cell death. The caspase-3 expression study indicated that nano-sulfur induces apoptosis by the activation of caspase through the mitochondrial pathway. Apart from this, a lower cytotoxicity was observed in IMR90 cell lines treated with SNP-B , indicating a higher specificity of synthesized nanosheets towards cancer cells. Taken all together, this work highlights the potentiality of sulfur nanosheets in inducing cytotoxicity and apoptotic activity, and the impact of morphology as a critical determinant on the cytotoxic response on various cell lines.
ABSTRACT
Despite great advancements in optical materials and luminescent hosts, self-luminescent blue-emitting phosphors are very limited. In this study we present the influence of fuels used in combustion synthesis on the photoluminescence and thermoluminescence (TL) characteristics of self-luminescent Sr2 CeO4 blue-emitting phosphors. Four different fuels, oxalyldihydrazide (ODH), sugar, glycine, and ethylenediaminetetraacetic acid, were used to synthesize Sr2 CeO4. Powder X-ray diffraction patterns showed that pure orthorhombic Sr2 CeO4 was formed only with the ODH fuel and the other fuels resulted in the formation of impurity phases. Excitation spectra showed peaks at ~290 and 340 nm, corresponding to charge transfer bands from different O2 - to Ce4+ ions. The emission spectra showed an intense blue-emitting band at 470 nm and the highest emission intensity was found for the sample prepared with ODH. Furthermore, TL glow curves for the γ-irradiated Sr2 CeO4 nanophosphor showed that ODH as fuel produced a more intense glow curve compared with other fuels investigated. TL glow curve analysis was carried out by calculating parameters such as activation energy, frequency factor, and order of kinetics. This study explores the importance and role of fuel in tuning the optical properties of phosphor hosts.
