Image: A field-emission scanning electron microscope image showing the good spreading and interactions of cells (appearing as red) with a scaffold made from the new fibres.
“It has long been known that mechanical, chemical and nanotopographic cues influence cell functionality, so a biomaterial with the ability to direct cell response has been a holy grail in tissue engineering,” says Nadège Sachot, first author on the paper.
The team coated nanostructured, electrospun polymer fibres with bioactive glass, assembling hybrid nanofibres with a strong union between the fibre and the coating – effectively creating a new material, rather than simply a composite. Previous attempts, which usually involved ceramic or glass being dispersed into a polymer matrix, which improves resilience, have always resulted in a loss of bioactivity and the collapse of the architecture.
“We did it the other way around, thus avoiding the usual problems that include lack of cell adhesion and too-fast degradation,” explains Nadège. “Working from previously published knowledge about the different components, we have managed to coordinate dissimilar compounds with different features in a synergic hierarchical device”. For example, in a bike, each separate material – the rubber tyres, the metal or plastic body, the upholstered seat – fit and work together, while each has an inherent role to play to accomplish the overall function: safe and fast motion, with an excellent cost-efficiency ratio.
“The core of the fibres is polylactic acid, a well-known biodegradable polymer, which acts as a flexible foundation and gives the coated fibers, which look like Japanese tempura, tailorable surface characteristics,” she says. “They also interact well with the biological environment. In the longer term, they aim to trigger specific cellular responses; in other words, they will provide the right chemical signals, topography, and mechanical properties to the cells to promote differentiation into a particular cell lineage, therefore stimulating the formation of new tissue. The resulting fibres are fully biodegradable, and will eventually be entirely replaced by the naturally regenerated tissue.”
The group’s new protocol, which can be transferred to other structures to allow the fabrication of different architectures depending on the application, offers a promising and versatile approach. It has possibilities in a broad range of biomedical applications that require well-defined, hierarchically engineered biomaterials with well-defined features, such as bone, vascular, skin or nervous tissue regeneration.
Reference article: Sachot, N., Castaño, O., Mateos-Timoneda, M.A., Engel, E. & Planell, J.A. (2013). Hierarchically Engineered Fibrous Scaffolds for Bone Regeneration. Interface, 10: 20130684