Cartilage wounds can be very difficult to treat. While they may eventually heal on their own, the resulting tissue often won't take the same form – or allow for the same function – as the original. Cartilage injuries are often treated with a process known as ACI (autologous chondrocyte implantation), in which a patient's own cells are injected at the wound site to form new tissue. The procedure doesn't always work, as the cells are just injected loosely, with no carrier to transport them or help them get established. Now, however, a scientist from the University of Michigan has developed a technique in which cells are delivered to wounds via injectable nanofiber spheres, and the results are said to be very promising.

Professor Peter Ma's process starts with star-shaped biodegradable polymers that self-assemble into hollow nanofiber microspheres. Cells, which are slightly smaller than the spheres, are then inserted into them.

Because they are very porous, the spheres allow nutrients to reach and nourish the cells, mimicking the cellular matrix in which the cells would normally be located. Once they reach the wound site, the spheres biodegrade, producing little in the way of byproducts that could affect cell development. Because of the protected environment they were in, the cells will have already started to grow by this point, and so are better able to integrate themselves into the wound site.

In small animal tests, wounds treated with the microspheres grew as much as three to four times the amount of tissue as a control group. Ma and his colleagues at U Michigan now plan on moving the tests up to larger animals, with human patients as their ultimate goal.

The research is being published in the journal Nature Materials.