News from February 16, 2019 — Although magnetic nanoparticles are increasingly used in cell imaging and tissue bioengineering, the changes that occur in their long-term stem cells are still not revealed. A recent study from C has shown that these nanoparticles degrade significantly within stem cells, in some cases "remagnetizing" the cells. The results, published in PNAS on 11 February 2019, explain the presence of "natural" magnetism in human cells and could help develop new tools for nanomedicine.
To track the journey of these nanoparticles through cells, the scientists from Sorbonne went further. Previously, researchers had developed an original method for creating nanomagnetism in biological systems: first, they incorporated magnetic nanoparticles into human stem cells in vitro. They then had them differentiate and develop for a month, observing them for a long time in the intracellular environment and monitoring their transformation.
By tracking the "magnetic fingerprints" of these nanoparticles in cells, researchers have shown that they are first destroyed (the cells' magnetization declines) and iron is released into the intracellular environment. And then, this "free" iron is stored in a non-magnetic form in ferritin, which stores iron, or serves as the basis for the biosynthesis of new magnetic nanoparticles within cells.
This is known to occur in some bacteria, but this biosynthesis has never been shown in mammalian cells. This could explain the existence of magnetic crystals in the human body, which are observed in cells in different organs, particularly the brain. What's more, this magnetic iron storage can also be a way for cells to "detoxify" over time to fight off excess iron. From the perspective of nanomedicine, this biosynthesis opens a new avenue for the possibility of pure biomagnetic markers in cells.