Chinese scientists have combined two separate scaffold-making techniques to create an artificial biomaterial that can withstand conditions in the body. 

Biomaterials are materials designed to replace or improve a natural function of a living structure. These materials can either be natural or man-made. 

Xiang Yao from Tsinghua University, Beijing, and colleagues combined ice-segregation-induced self-assembly (ISISA) and electrostatic self-assembly (ESA) to fabricate macroscale biomaterials from nanoscale building blocks. 

In ISISA, ice is used as a template to fabricate a porous structure whereas ESA uses two oppositely charged particles, suspended in a fluid, to attract each other. The ESA process has mainly been used to make 2D biomaterials, but Yao says his goal was 'to achieve a three dimensional and nanometre level biomimetic control of cell behaviour.' ISISA has been used to create 3D scaffolds but because the scaffolds are held together with weak forces with this method, a water soluble polymer such as polyvinyl alcohol is often used to bind them together. Unfortunately, the polymer is toxic, which limits its use in tissue engineering. 

When Yao combined the two methods by using ESA building blocks in an ISISA process, the team found that the resulting 3D scaffold was strong in water at 37 °C without the need to add toxic binders. This makes it suitable for use in physiological environments and Yao says he hopes his research can be used in biomedical applications such as stem cell tissue engineering. 

'The absence of cross-linkers should improve their biocompatibility as biomaterials but this issue must still be addressed,' says Marisa Ferrer, an expert in biomaterial design and application at the Instituto de Ciencia de Materiales de Madrid, Spain, who adds: 'The combination of ice ISISA and ESA beats the challenge of preparing 3D scaffolds working at physiological pH.'
 
Paul Hatton, who works on tissue engineering and polymer biocompatibility at the University of Sheffield, UK, comments that Yao's work is 'an elegant solution to one of the more significant challenges faced by those seeking to fabricate biomimetic materials, that of how to "build in" a nanoscale level of hierarchy in order to contribute to functional properties.' 

Rebecca Brodie 

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This story was changed on the 27th July 2009 to better reflect the meaning of biomaterials.