Md. Tajuddin Sikder

Removal of Cadmium and Chromium Ions Using Modified α, β, and γ-Cyclodextrin Polymers

The adsorption of cadmium and chromium from aqueous solutions with epichlorohydrin cross-linked α, β, and γ-cyclodextrin polymers (CDPs) was investigated under a wide range of experimental conditions including pH, metal concentration, and CDP amounts. Recent studies have shown that α, β, and γ-CDPs follow the Freundlich, Langmuir, and Brunauer–Emmett–Teller models and are capable of reducing heavy metal ion concentrations in water to desirable levels with enhanced sorption capabilities. The removal of cadmium and chromium achieved equilibrium in 4 h. The pH of effective cadmium removal was 6.5 to 7.5, and phosphate buffer favored the removal of cadmium in the presence of potassium ion. Chromium removal was optimal at pH 3.6 to 6.5. Current technologies can remove 99% cadmium ions from solution, yet this process is not very efficient for chromium ions. Furthermore, a small amount of CDPs can remove large quantities of heavy metal ions and can then be regenerated with acid for reuse. The present results are promising for using inexpensive CDPs as a low-cost material that is effective in remediating waters contaminated with heavy metal species. The sorption kinetics of CDPs along with the conditions to adsorb cadmium and chromium are reported here for the first time.

Sustainable pesticide governance in Bangladesh: socio-economic and legal status interlinking environment, occupational health and food safety

Pesticides, regardless of their known toxic impacts to human health and environment, are widely used in the rapid growing agricultural sectors of developing countries. As an agricultural country with small lands and enormous population to feed, a developing country like Bangladesh rely heavily on the uses of pesticides to increase crop yields. Nevertheless, during the past decades, Peoples’ Republic of Bangladesh has experienced 26.46% decrease in total pesticide consumption. However, the presence of unregistered pesticides in the environmental samples and agricultural products has pointed out the weakness in the existing legal regime of the pesticide governance. This, in turn, is threatening the livelihood and health of the farmers, food safety and consumer health. This paper reviews the antiquity of the status of pesticide consumption, evolution and drawbacks of pesticide in the context of existing socio-economic position of Bangladesh. A consolidated uniform system is lacking to project pesticide management in the country. Existing legal policy, rules and regulations in the context of international agreements regarding pesticide management have been reviewed and suggested for further amendment. Moreover, role of green microfinance in sustainable management of pesticides and food safety were recommended. A framework is proposed for pesticide governance with a stronger pesticide surveillance program and coordination of ministries interlinking environmental, occupational health and food safety.

Ameliorative effects of selenium on arsenic-induced cytotoxicity in PC12 cells via modulating autophagy/apoptosis

Arsenic is well known toxicant responsible for human diseases including cancers. On the other hand, selenium is an essential trace element with significant chemopreventive effects, anticancer potentials and antioxidant properties. Although previous studies have reported antagonism/synergism between arsenic and selenium in biological systems, the biomolecular mechanism/s is still inconclusive. Therefore, to elucidate the molecular phenomena in cellular level, we hypothesized that co-exposure of selenium with arsenic may have suppressive effects on arsenic-induced cytotoxicity. We found that selenium in co-exposure with arsenic increases cell viability, and suppresses oxidative stress induced by arsenic in PC12 cells. Consequently, DNA fragmentation due to arsenic exposure was also reduced by arsenic and selenium co-exposure. Furthermore, western blot analyses revealed that simultaneous exposure of both metals significantly inhibited autophagy which further suppressed apoptosis through positively regulation of key proteins; p-mTOR, p-Akt, p-Foxo1A, p62, and expression of ubiquitin, Bax, Bcl2, NFкB, and caspases 3 and 9, although those are negatively regulated by arsenic. In addition, reverse transcriptase PCR analysis confirmed the involvement of caspase cascade in cell death process induced by arsenic and subsequent inhibition by co-exposure of selenium with arsenic. The cellular accumulation study of arsenic in presence/absence of selenium via inductively coupled plasma mass spectrometry confirmed that selenium effectively retarded the uptake of arsenic in PC12 cells. Finally, these findings imply that selenium is capable to modulate arsenic-induced intrinsic apoptosis pathway via enhancement of mTOR/Akt autophagy signaling pathway through employing antioxidant potentials and through inhibiting the cellular accumulation of arsenic in PC12 cells.

Inhibitory effects of selenium on cadmium-induced cytotoxicity in PC12 cells via regulating oxidative stress and apoptosis

Purpose of this study is to investigate mechanism/s of cyto-protection by selenium (Na2SeO3; Se4+) against cadmium (CdCl2; Cd2+)-induced cytotoxicity using PC12 cells. In addition, Se (5, 10, 20 and 40 μM) and Cd (2.5, 5 and 10 μM)-induced cytotoxicity is determined. Cytotoxicity assays and western blot analyses confirmed that Se (≥10 μM) promotes autophagic cell death via inhibition of mTOR activation and p62 accumulation due to increase of cellular oxidative stress. On the other hand, co-presence of non-toxic Se (5 μM) and toxic Cd (5 μM) showed to increase cell viability, glutathione and glutathione peroxidase 1 (GPx1) levels, and to decrease DNA fragmentation and lactate dehydrogenase (LDH) activity compared to Cd-treated (5 μM) cells alone. Furthermore, western blot analyses of cytochrome c and ERK1 indicated that Cd-induced apoptotic cell death in PC12 cells. However, the co-exposure of Se with Cd significantly decreases the release of cytochrome c into cytosol from mitochondria, and up-regulates ERK1 protein to inhibit Cd-induced apoptosis. In conclusion, Se (≥10 μM) possess cytotoxicity in PC12 cells; however, co-presence of Se (5 μM) with Cd (5 μM) protects against Cd-induced apoptosis in PC12 cells due to inhibition of Cd-induced oxidative stress and subsequently suppression of mitochondrial apoptosis pathway.

Application of α, β and γ cyclodextrin polyurethanes in the removal of size specific copper derivatives

Copper can be found in many wastewater sources including, printed circuit board manufacturing, electronics plating, plating, wire drawing, copper polishing, paint manufacturing, wood preservatives and printing operations. Typical concentrations vary from several thousand ppm from plating bath waste to less than 1 ppm from copper cleaning operations. Copper can be removed from wastewater by precipitation as an insoluble hydroxide salt or by ion exchange. In this study, single batch adsorption experiment of copper derivatives, e.g. CuCl2.2H2O, Cu(CH3COO)2 and CuSO4.5H2O from aqueous solutions with epichlorohydrin linked α, β and γ cyclodextrin polyurethanes (CDPs) have been investigated for a wide range of experimental conditions: pH, metal concentration and CDP amounts. The aim of this study was to specify highly effective derivatives of copper to fit on the CDP backbone as the size of the copper molecules is different to each other. Recent studies have shown that α, β and γ CDPs are capable of removing copper ions of all derivatives from water to desirable levels with enhanced sorption capabilities. The adsorption efficiencies of CDPs were surprisingly similar and found to be independent for each type of copper derivatives. The phosphate buffer with pH 6.5-7.5 was found the best alkaline environment to remove the ions. Current technologies have been