AMID the increasing debate about the potential health risks of nanoparticles comes a surprising result: they can prolong the life of brain cells. Neurons usually only live for around 25 days in the lab, but after a low dose of cerium oxide nanoparticles, they survived and functioned normally for 6 months. The finding raises hopes that the particles could one day be used to treat age-related disorders such as Alzheimer’s disease.
Molecular biologist Beverly Rzigalinski and engineer Sudipta Seal of the University of Central Florida in Orlando originally teamed up to see if the nanoparticles could be used to deliver drugs into cells. Their first experiment was to add bare particles to rat neurons in culture to see how well they were taken up. When Rzigalinski later checked the neurons, she found that they survived much longer than untreated cells, and that they were signalling to each other as effectively as young cells. The longest-lived culture survived for 6 months. “It’s amazing,” says Seal. “I’m ecstatic.”
The team has also found the treated cells are protected against damage from UV radiation. This suggests that the nanoparticles are mopping up free radicals – reactive molecules that damage cells and are known to be involved in ageing and inflammation. Each nanoparticle consists of atoms of cerium and oxygen that form a structure 5 nanometres across. Rzigalinski suggests that this binds to the free radicals, keeping hold of them until they become neutralised (see Graphic).
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The particles are four times as good at mopping up radicals as natural scavengers such as vitamin C or vitamin E, and also seem to last much longer within the cells. Although the neurons only received one dose of nanoparticles, the scavenging effect lasted for months. Whereas a molecule of vitamin C is destroyed when it binds to a free radical, the nanoparticles seem to be able to repeat the process over and over again.
Rzigalinski now plans to see if cerium oxide nanoparticles can slow the progression of neurodegenerative diseases in mice. She also plans to feed the particles to fruit flies to see if they live longer than normal. The particles might one day be used to coat artificial joints or medical equipment, she says, to reduce inflammation in patients.
But chemical biologist Tony Cass at Imperial College London cautions that safety concerns will need to be answered before nanoparticles can be used in people. “We need to consider the potential for other interactions with cellular constituents,” he says.