In tissue engineering, the type, composition and properties of biomaterials used as scaffolds have a profound effect on the regeneration of new tissues. In the case of collagen, for example, its structure and fibrillar arrangement in vivo have a direct affect on its function – such as its ability to withstand mechanical stress – and so optimal scaffold mechanics should provide an environment that mimics the molecular arrangement of collagen fibrils.
Continued improvements in biomaterial design have been able to translate some of these structure-function relationships successfully to yield new in vivo models, and new materials have emerged that provide more optimal environments for cellular growth and tissue reconstruction.
These new “smart” scaffolds generally involve combination and hybrid materials coated with growth factors or cells for improved vascularization. The growth factors are usually chosen so that they mimic specific functions of in vivo tissue and are crucial for optimal engrafment of the implanted scaffolds and to support the function of the newly formed tissue.
The trend toward such “smart” scaffolds has created a number of novel biomaterials with promising regenerative behavior.
In a study published last week in the Proceedings of the National Academy of Sciences, a new combination scaffold, made from a combination of silk protein and a collagen-based gel, coated with rat neurons, was developed as a model of 3D brain-like tissue. The authors, led by Dr. David Kaplan of Tufts University, showed that the neurons managed to grow axons through the scaffold, which itself survived for more than two months in the lab. The authors also founds that neurons in their 3D brain-like tissue exhibited higher expression of genes involved in neuron growth and function.
Elsewhere, novel approaches for improved coating of scaffolds are being developed: researchers at the University of Colorado developed a new 3D scaffold based on PLGA coated with growth factors for controllable bone tissue regeneration. Using a layer-by-layer assembly approach, the authors coated the PLGA scaffolds with platelet-derived growth factor (PDGF) first, followed by bone morphogenetic protein 2 (BMP-2), two most important growth factors for bone repair. By coating PDGF first followed by layers of BMP-2, the authors achieved sustained release of the growth factors in a way that mimics the process of in vivo healing.
Nanotechnology is also emerging as a tool to achieve molecular structures of scaffolds closer to those of native tissue – such as the recent development of nanoparticles – published about in Scientific Reports – for the assembly of collagen scaffolds with fibrillar lamellae that resemble native lamellae.
Such examples of new 3D scaffolds emphasize the importance of combination approaches for developing next generation tissue regeneration substrates and show that scaffolds of the future will benefit multipronged development approaches.