Free radicals play a key role in the ageing process. The strongly debated
free radical theory of ageing even states that damage caused by free radicals
is the main cause of aging on a cellular level. However, free radicals are
small, reactive and short lived and thus challenging to measure. We utilize a
new technique called diamond magnetometry for this purpose. We make use of
nitrogen vacancy centers in nanodiamonds. Via a quantum effect these defects
convert a magnetic resonance signal into an optical signal. While this method
is increasingly popular for its unprecedented sensitivity in physics, we use
this technique here for the first time to measure free radicals in living
cells. Our signals are equivalent to T1 signals in conventional MRI but from
nanoscale voxels from single cells with sub-cellular resolution. With this
powerful tool we are able to follow free radical generation after chemically
inducing stress. In addition, we can observe free radical reduction in presence
of an antioxidant. We were able to clearly differentiate between mutant strains
with altered metabolism. Finally, the excellent stability of our diamond
particles allowed us to follow the ageing process and differentiate between
young and old cells. We could confirm the expected increase of free radical
load in old wild type and sod1{\Delta} mutants. We further applied this new
technique to investigate tor1{\Delta} and pex19{\Delta} cells. For these
mutants an increased lifespan has been reported but the exact mechanism is
unclear. We find a decreased free radical load in, which might offer an
explanation for the increased lifespan in these cells.Comment: Main Text: 21 pages, 4 figures / Supplementary information: 13 pages,
13 figure