Thin Microgels Encapsulate and Protect Therapeutic Cells

Cell-based therapies, such as those involving the delivery of stem cells, require a way to encapsulate cells inside a protective package in order for them to not be destroyed and washed out by the body. There have been successful attempts…

Cell-based therapies, such as those involving the delivery of stem cells, require a way to encapsulate cells inside a protective package in order for them to not be destroyed and washed out by the body. There have been successful attempts to contain therapeutic cells within hydrogels, but the resulting materials were bulky and could not be delivered intravenously.

Now, researchers at Harvard’s Wyss Institute have developed a way of packaging individual cells within thin-walled hydrogels, which can then be intravenously injected to take on therapeutic tasks. Moreover, their approach results in nearly all of the vesicles having exactly one cell inside, a huge improvement on previous attempts which suffered from poor efficiency. And as a sweetener, the resulting encapsulated cells can be frozen and thawed later when they actually have to be used in a procedure, greatly simplifying the clinical workflow.

Dividing MSCs (blue) within a thin layer of the crosslinked alginate microgel (purple) showed improved performance over a previous version of the microgel. This could be a model for improving cell therapy in humans.
So far, this technology has been tested in lab mice, but in their study, reported in the Proceedings of the National Academy of Sciences, the Wyss researchers were able to significantly improve the effectiveness of mesenchymal stem cells delivered using this encapsulation technique. That’s probably because the thin walls of the hydrogel protect the cell inside, giving it time to do its job, while also allowing the cell to interact with its nearby environment.

“This is an exciting and important extension of cell-based biomaterials to the level of single cells, which can then serve both as a precise building block for larger cell structures and as a means of investigating the behavior at the level of single cells, providing unprecedented insight into cell function and properties,” said David Weitz, Ph.D., one of the leads of the research.

An announcement from the Wyss Institute briefly explains the encapsulation process:

As done in pre-existing techniques, the team first coated cells in calcium carbonate nanoparticles, a step that facilitates cell encapsulation when mixed with an alginate polymer solution. But for the first time before mixing with a polymer solution, the team washed away the nanoparticles that had not adhered to the cells using a water and oil emulsion inside a microfluidic device. What remained were predominantly microgel-encapsulated single cells.

The researchers can already pack thousands of cells within the thin hydrogels in a matter of minutes, and if the process of tissue building is further refined, the new technique could be a component of how new tissues will be printed one cell at a time.