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"Green" synthesized and coated nanaosilver alters the membrance permeability of barrier (intestinal, brain, endothelial) cells and stimulates oxidative stress pathways in neurons.
Citation:
Baruwati, B., Steve Simmons, R. Varma, AND B. Veronesi. "Green" synthesized and coated nanaosilver alters the membrance permeability of barrier (intestinal, brain, endothelial) cells and stimulates oxidative stress pathways in neurons. ACS Sustainable Chemistry & Engineering. American Chemical Society, Washington, DC, 1(7):753-759, (2013).
Impact/Purpose:
Linkage of physicochemistry to biological activity/toxicity is important in the prediction of nanotoxicity. Essential for the development of intelligible and valid guidelines on nanoparticles. Research just awarded ORD’s Peer Ovation award (2012).
Description:
Nanosilver's (nanoAg) use in medical applications and consumer products is increasing. Because of this, its "green" synthesis and surface modification with beneficial coatings are desirable. Given nanoAg's potential exposure routes (e.g., dermal, intestinal, pulmonary)) questions on its potential to move through these "port of entry" barriers and enter the body's circulatory system remain unanswered. In view of nanoAg's free radical activity and the brain's sensitivity to oxidative stress damage, the possibility that nanoAg particles can move from the systemic circulation, transport through the blood-brain barrier (BBB) and pose neurotoxic threat is also a legitimate question. Because of these concerns, this study addressed if "green" synthesized nanoAg, coated with green tea polyphenols (GT), or glutathione (GSH) could alter the permeability of human intestinal epithelia (Caco-2) or rat brain endothelial (RBEC4) cells. Additionally, it asked if such "green" synthesis and coating modifies nanoAg's toxicity to oxidative stress sensitive cultured neurons (N27). Physicochemical (PC) characterization of conventionally synthesized nanoAg and "green" synthesized nanoAg-GT or nanoAg-GSH indicated that all samples aggregated (>500-2500 nm) when suspended in cell culture exposure media. NanoAg-GSH showed the lowest zeta potential and largest aggregate size in both Caco-2 and RBEC4 exposure media. Resistance measures indicated that within 15 min exposure to 6.5 ppm, both conventional and "green" nanoAg-GSH altered the permeability of intestinal Caco-2 cells and all nanoAg treatments altered the permeability of RBEC4 brain endothelial cells. To examine if a differential toxicity existed in the response of oxidative stress-sensitive neurons, a non-cytotoxic (1.0 ppm) concentration of each nanoAg material was exposed (18 hr) to rat dopaminergic neurons (N27), transfected with a NFKB reporter gene. Results indicated that all nanoAg samples significantly stimulated this oxidative stress pathway in the N27 neuron. Together, these data suggest that both conventional and "green synthesized" coated nanoAg alter the permeability of barrier cell membranes and activate oxidative stress pathways in target neurons, equally.