To make the nanofibre tubes, the scientists electrospun a 7 wt% solution of poly(L-lactide-co-glycolide) (PLGA 10:90) in hexafluoroisopropanol. They put the polymer solution in a syringe, maintaining the needle tip at a voltage of 12 kV. Then they fed polymer into the tip at a rate of 1 ml per hour. An aluminium collection grid 10 cm away was kept at a negative voltage.

The resulting fluid jet formed nanofibres of polymer, which the team collected by rolling the fibre around a 1.27 mm diameter Teflon tube just in front of the aluminium target. This created a nanofibre tube with an inner diameter of 1.27 mm. The researchers then used these tubes as nanofibre nerve-guide conduits.

To test the structures' performance, the team implanted 14 mm-long nanofibre conduits into rats. They removed a 5-7 mm-long piece of the right sciatic nerve of the rat and inserted the two remaining nerve ends a distance of 2 mm into each end of the conduit. One month after this procedure, the reflex responses of five of the 11 rats tested (i.e. 45%) showed that nerve regeneration had taken place in those animals.

"From our study, it was significant that permeability of the nerve conduit is an important factor governing nerve regeneration," researcher T B Bini told nanotechweb.org. "Permeability of the tubes allowed nutrients from the external surroundings to flow into the conduit lumen, which was essential for nerve regeneration."

As well as having a porous structure, the implanted tubes were also flexible enough not to break and prevented unwanted tissues from infiltrating from outside. What's more, the tubes did not cause any inflammation response, which is desirable as it minimizes the adhesion of the conduit to surrounding tissues. The nanofibres are also biodegradable, which means that they would not need to be removed from the body at a later date.

The team believes that they could improve the nerve regeneration by incorporating Schwann cells or nerve growth factors into the polymer nanofibre tubes.

Now the team plans to carry out studies on larger animals and look at regenerating other tissues. Bini says the technique could have applications in biotechnology - perhaps for making functionalized nanofibre substrates for the separation, expansion and differentiation of stem cells.

"Using our modified electrospinning technique, a wide range of polymer nanofibre scaffolds can be made," said Bini. "Through material selection and surface functionalization using secondary processing techniques, the nanofibre scaffolds can be tailor-made to specific tissues to be regenerated, for example, nerve, blood vessel, skin, bone, cartilage and liver."

The researchers reported their work in Nanotechnology.