Nanoparticles Used to Detect ‘Zombie’ Cells in Living Organisms

In this study, researchers have developed a new technique to visualise senescent cells in living organisms.

Senescence is a state of dormancy brought about in response to DNA damage and cellular stress. Senescence plays a necessary protective role against the development of cancer by preventing cell division. However, the accumulation of senescent cells within tissues is thought to be a major contributor to the ageing process.

Scientists have a variety of methods for detecting senescent cells, but most of these work only in cell cultures or tissue samples, meaning that an animal has to be sacrificed in order to measure senescence within its organs.

Now, researchers have developed a new technique that allows senescent cells to be visualised in live organisms. The technique uses nanoparticles loaded with a fluorescent dye called Nile Blue. When Nile Blue molecules are packed closely together within the nanoparticle, they remain inactive. However, the sugar cap of the nanoparticle is broken down by β-galactosidase, an enzyme that is overproduced in senescent cells. This means that when the nanoparticles enter a senescent cell, they release their cargo of Nile Blue dye, which is then able to emit light under fluorescence imaging.

The technique was used to measure senescence over time in tumour-bearing mice injected with the nanoparticles. The mice on the right received chemotherapy that induces senescence within the tumour, while those on the left received only the nanoparticle:

Nile Blue is approved for human use by the FDA, suggesting that this, or a similar technique, could potentially be applied to measure the effectiveness of anti-ageing therapies such as senolytics – drugs aimed at removing senescent cells from tissues.