German researchers have devised a technique that could allow the creation of improved ‘biological scaffolds’ for tissue engineering. They have optimised the electrospinning process – which creates tiny polymeric fibres – to make a mesh that combines fibres of two distinct sizes. Electrospun meshes usually contain fibres of a single size.
‘If you only use one size of fibre, then the cells stick to the surface,’ says Andreas Lankenau, of Fraunhofer Institute for Biomedical Engineering (IBMT) in Potsdam. ‘The mixed fibres help cells to penetrate and stick to internal surfaces.’
The larger fibres have a diameter of 4-9μm, and allow cells to penetrate into the mesh; the nanofibres are 400- 600nm in diameter, and encourage cell adhesion (Macromolecular Rapid Communications doi: 10.1002/ marc.200900431).
Biological scaffolds are designed to mimic a part of the body that needs to be regenerated, such as soft tissue or even brain tissue. They must be strong, biocompatible and sufficiently porous to encourage cell penetration and re-growth.
While the work is at a very early stage, the researchers, from Fraunhofer IBMT and the nearby Max Planck Institute of Colloids and Interfaces, Germany, say that the mesh has advantages over single sized meshes: for a 1.5μm mesh, more than 80% of cells remain at the surface; a 4μm mesh, and the mixed mesh, both showed around 50% of cells at the surface.
Three electrospinning process conditions were critical to the production of the bimodal fibre mesh: a 15% concentration of polycaprolactone (PCL) in chloroform; a slow spinning rate, of 0.2ml/ hour; and humidity of at least 39%. Deviation from these conditions led to the disappearance or reduction in the quantity of nanofibre synthesised.
Rafael Gentsch of the Max Planck Institute, a co-author of the paper, says: ‘Advanced filters will also be possible, as nanofibre meshes increase capture efficiency while microfibres provide porosity, preventing a drastic pressure drop.’
Kerry Kirwan, a researcher at Warwick Manufacturing Group in the UK, who has looked into how electrospinning could be used to create medical materials, says: ‘It’s not groundbreaking, but the notion of generating the two differently scaled fibres – and exploiting that – is interesting. There is a problem with cell growth in current structures. This work could help to solve that.’