"This technique allows us to control the concentration of nanoparticles at different parts of the mesh," Dilhan Kalyon of the Stevens Institute of Technology, US, told nanotechweb.org. "As a result, we can generate continuous gradients that will enable the better mimicking of native tissue characteristics."

The process allows the compounding of various additives with a high degree of freedom, which provides greater control over functions such as drug release.

In the mix
At the heart of the hybrid platform are two fully intermeshing and co-rotating screws (supplied by Material Processing and Research, US) that are connected to a hydraulic drive. Designed for higher degrees of dispersive and distributive mixing, the screws feature reversely configured kneading blocks that are ideal for breaking up agglomerates of nanoparticles.

To make their mesh structure, the researchers first feed a biodegradable and electrically conductive polymer into the extruder. Here the material is loaded with varying concentrations of nanoparticles and other ingredients in a controlled manner, processed to disperse the nanoparticles and then forced out of a spinneret die ready for electrospinning. A high potential difference created between the extruder's outlet (spinneret) and a collecting plate draws a fibre of polymer incorporated with nanoparticles onto the substrate to create the mesh.

The group tested its process by adding beta-tricalciumphosphate nanoparticles to polycaprolactone dissolved in dichloromethane and obtained fibres in the range 200–2000 nm in diameter. Images revealed that the nanoparticles appear to be well dispersed and distributed within the fibres.

As Kalyon explains, the team is able to keep the pore size of its non-woven mesh within the range 5–50 µm, which is particularly suitable for cartilage and skin tissue applications.

The researchers presented their work in Nanotechnology.