It was over a sushi lunch that John Kessler, a neurobiologist in the Medical School at Northwestern University, learned about self-assembling peptide amphiphiles from Sam Stupp, a materials scientist at Northwestern. In aqueous solutions these amphiphiles — which have hydrophilic, hydrophobic and peptide segments — self-assemble into cylindrical nanofibres, with the peptides displayed at very high densities on the outside. After in vitro testing of various samples from Stupp's lab, Kessler and co-workers showed that amphiphiles containing the IKVAV peptide fragment could support the growth of neuronal cells while keeping the cells that make scar tissue at bay.

Reckoning that it might be possible to treat spinal cord injuries with the nanofibres, Kessler's team injected the amphiphiles into the spinal cords of mice that had been compressed to simulate an injury. They found that the treatment led to regeneration of motor and sensory fibres at the site of the lesion. Furthermore, the treatment reduced cell death in the area and encouraged the growth of oligodendroglia (the cells that form the insulating sheaths around neuronal cells). The behaviours of the mice also improved considerably compared with those treated with saline solution or a solution in which the IKVAV peptides were not part of the self-assembled nanofibres (J. Neurosci. 28, 3814–3823; 2008).

“The most rewarding part of the collaboration was our ability to merge technologies to, we hope, eventually impact on the treatment of human disease,” says Kessler. “The most difficult part was convincing the different cultures of our professional fields of the potential of nanotechnology in medical research. I had to learn at the very beginning how the density of peptides presented to a cell can change the properties of the materials. Most medical researchers do not fully appreciate this point.”