'Nano-in-micro' stem cell delivery could rescue blood flow after injury

Xiaoming "Shawn" He, Zhenguo Liu and colleagues recognized that in order to improve the viability of stem cell treatments for ischemia, it was crucial to continuously deliver molecules like growth factors to help the stem cells survive and develop into new blood vessels. Nanoparticles are good at this sort of biomolecule delivery, but they tend to drag the cargo inside cells. To treat ischemia, the growth factors need to stay outside the cells. The researchers hypothesized that bigger particles could do the trick.

The researchers encapsulated a growth factor inside nanoparticles first to protect them from degradation, and then placed the nanoparticles inside much larger hydrogel microcapsules that cannot be taken up by cells. This design provided long-term protection and delivery of the growth factor. When the authors tested their system in a mouse model of ischemia, they observed successful differentiation of stem cells, growth of blood vessels and the restoration of blood supply, collectively rescuing muscle tissue and saving the limbs of the mice.