Credit: © 2006 ACS

The delivery of angiogenic growth factors — proteins that promote blood vessel growth — is essential for wound healing. The sustained release of growth factors can be achieved by attaching them to a polymer matrix that has been decorated with heparin — an anticoagulant that binds to many growth factors and protects them from enzymatic degradation. However, the poorly defined polymer-heparin microstructure has limited the efficacy of this approach. Researchers at Northwestern University in the USA have now utilized rigid nanofibres to display heparin molecules more effectively than conventional polymers.

Samuel Stupp and colleagues1 mixed a solution of peptide amphiphiles — each of which had a hydrophobic tail and a hydrophilic head — with heparin in the presence of growth factors. Heparin screens the charges on the peptides and promotes their self-assembly into networks of fibre bundles (50–100 nm in diameter). The resulting nanofibres were rigid and presented heparin on the outside over a large surface area. Rat corneas that received heparin bound nanofibres with added growth factors showed a statistically significant increase in blood vessel length and area compared with control samples. The rigid nanofibres retained the growth factors and oriented them for cell signalling events, which is necessary for effectively directing blood vessel formation.

The work by Stupp and colleagues represents a new strategy to direct blood vessel formation using nanostructures with better-defined shape and surfaces than conventional polymers.