Biosynthesis of gold nanoparticles and related cytotoxicity evaluation using A549 cells

Biosynthesis of gold nanoparticles (AuNPs) has become an attractive area of research as it is environmentally benign. The toxicity of AuNPs synthesized by chemical routes has been widely studied. However, little is known about the toxicity associated with the biological synthesis of AuNPs. The present study was carried out to synthesize AuNPs using star anise (Illicium verum; a commercially available spice in abundance)and evaluate its toxicity using human epithelial lung cells (A549) in comparison with AuNPs synthesized by the traditional chemical methods (using sodium citrate and sodium borohydride). Apart from cell viability, markers of oxidative stress (reduced glutathione) and cell death (caspases) were also evaluated to understand the mechanisms of toxicity. Cell viability was observed to be 65.7 percent and 72.3 percent in cells exposed to chemically synthesized AuNPs at the highest dose (200nM) as compared to 80.2 percent for biologically synthesized AuNPs. Protective coating/capping of AuNPs by various polyphenolic compounds present in star anise extract appears to be a major contributor to lower toxicity observed in biologically synthesized AuNPs.

Experimental studies on removal of microcystin-LR by peat

Cyanotoxins have caused worldwide concerns for their eclectic occurrence and toxic effects, which led to an intensive search of cost-effective techniques for their removal from contaminated waters. A range of biomaterials was tested for their efficacy to adsorb a potent cyanotoxin, microcystin-LR (MCLR). Among these sorbents, peat showed the maximum efficacy to sequester MCLR. The BET (Brunauer-Emmett-Teller) surface area of peat was found to be 12.134 m(2)/g. The pH of the reaction media played a significant role in removal of MCLR; maximum adsorption occurred at pH 3. Kinetic studies showed that the adsorption of MCLR onto peat was a rapid process. The adsorption capacity (Q(max)) from the Langmuir model was found to be 255.7 μg/g at pH 3. Among various desorption media studied, strong alkali (2N NaOH) showed highest desorption (94%).

Removal of a potent cyanobacterial hepatotoxin by peat

Microcystins (cyclic heptapeptides), produced by a number of freshwater cyanobacteria, are of health concern in potable water supplies. In this article, the adsorptive removal of microcystin-RR (MCRR) from the aqueous solution by a low-cost adsorbent, peat, was investigated. The BET surface area of peat was found to be 12.134 m2/g. The adsorption process was pH dependent, with maximum adsorption occurring at pH 3. Kinetic studies revealed that the adsorption of MCRR onto peat was a rapid process. The adsorption capacity (Qmax) as revealed by the Langmuir model was found to be 286 μg/g at pH 3. Among various desorption media studied, strong alkali solutions (2 N NaOH) showed the highest desorption (97%). Thus, peat has potential to be used as an adsorbent for the removal of the cyanotoxin, MCRR, from drinking water.