US researchers develop method of identifying cell-damaging nanomaterials
Because the semiconductor properties of metal-oxide nanomaterials could potentially translate into health hazards for humans, animals and the environment, it is imperative, UCLA researchers in the US say, to develop a method for rapidly testing these materials to determine the potential hazards and take appropriate preventative action.
UCLA scientists and their colleagues have developed a screening technology that allows large batches of these nanomaterials to be assessed quickly, based on their ability to trigger certain biological responses in cells as a result of their semiconductor properties.
The research is published in the journal ACS Nano.
Just as semiconductors can inject or extract electrons from industrial materials, semiconducting metal-oxide nanomaterials can have an electron-transfer effect when they come into contact with human cells that contain electronically active molecules, the researchers found.
Although these oxidation–reduction reactions are helpful in industry, when they occur in the body they have the potential to generate oxygen radicals, which damage cells, triggering acute inflammation in the lungs of exposed humans and animals.
In a key finding, the research team predicted that metal-oxide nanomaterials and electronically active molecules in the body must have similar electron energy levels — called band-gap energy in the case of the nanomaterial — for this hazardous electron transfer to occur and oxidative damage to result.
Based on this prediction, the researchers screened 24 metal-oxide nanoparticles to determine which were most likely to lead to toxicity under real-life exposure. Using a high-throughput screening assay (performed by robotic equipment and an automated image-capture microscope), they tested the materials on a variety of cell types in a few hours and found that six of them led to oxidative damage in cells.
The team then tested the nanomaterials in animal studies and found that only those materials that had caused oxidative damage in cells were capable of generating inflammation in the lungs of mice.
“The ability to make such predictions, starting with cells in a test tube, and extrapolating the results to intact animals and humans exposed to potentially hazardous metal oxides, is a huge step forward in the safety screening of nanomaterials,” said senior author Dr Andre Nel, chief of the division of nanomedicine at the David Geffen School of Medicine at UCLA.
According to the scientists, this technology has the potential to replace traditional testing and could speed up the ability to assess large numbers of emerging new nanomaterials rather than waiting for their toxicological potential to become manifest before action is taken.
Another major advantage of this approach is that one can identify those properties that could potentially be redesigned to make the materials less hazardous.
The implementation of high-throughput screening is also leading to the development of computer tools that assist in prediction-making; in the future, much of the safety assessment of nanomaterials could be carried out using computer programs that perform smart modelling and simulation procedures based on electronic properties.
“We can now further refine the testing of an important class of engineered nanomaterials to the level where regulatory agencies can make use of our predictions and testing methods,” said Haiyuan Zhang, a postdoctoral research scholar at the Center for Environmental Implications of Nanotechnology at UCLA's CNSI and the lead author of the study.
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