Self-supporting scaffolds for biomedical applications
Researchers in the UK have developed a groundbreaking technique for growing self-supporting scaffolds from polymeric fibres. Referred to as electrohydrodynamic jet assembly, the technique has resulted from a collaboration between Dr Suwan Jayasinghe at University College London and Professor Alice Sullivan at Queen Mary, University of London.
The conventional jet-based method for producing polymeric fibres in the nano- to micrometre range is by electrospinning, a technique that has been studied for well over a century. This involves using a potential difference to draw a liquid or suspension through the end of a needle, forming a so-called jet. Importantly, the jet does not break up. It produces continuous fibres, or an umbrella of fibres, that go on to form meshes through instabilities within the solution.
Although similar in some regards, the method developed by Jayasinghe and Sullivan is fundamentally different in one crucial aspect - the jet breaks up into individually charged droplets, which can then form continuous self-supporting fibres as these droplets self-assemble. Fundamental to their technique is a tailor-made siloxane resin. ‘The liquid has ethanol in it,' explains Jayasinghe, ‘so when the droplet is in the air the ethanol evaporates.' The droplets of polymer solution become attracted to one another, forming fibres that create self-supporting scaffolds, or webs, in two or three-dimensions (see image above).
The excellent cross-linking nature of the polymer, together with this novel jetting approach, is responsible for the droplet interaction. According to Jayasinghe, the droplets undergo polycondensation at the point where the molecules cross-link, resulting in the molecules becoming ‘completely fused'. The technique could be used in biological applications because of the biocompatibility of the polymeric material and its ability to act as a scaffold on which cells can grow. ‘We are hoping to grow structures in different sizes and shapes in confined spaces,' explains Jayasinghe, who follows up with a dental example - ‘Imagine you get your tooth drilled, and some of the solution is sprayed into the hole to form a scaffold. If you put the necessary cells in there, the tooth could be re-grown. Essentially, the scaffold provides a breeding ground for your cells.'
As well as biomedical applications, Jayasinghe suggests the scaffolds could also be used to make porous materials, such as those required for nano-filters. Using this technique, he says it is possible to make structures ranging in size from nanometres to millimetres. But controlling the structure is something the team cannot do at present and this will be the focus for future investigations.
Journal of Physical Chemistry B 2006, 110, pp2522-2528