The concept of tissue engineering has been redefined with the increasing use and popularity of “Scaffolds” for tissue regeneration and the subsequent implantation of the regenerated tissue in human body.

Earlier it was conveniently described as an interdisciplinary field that applies the principles of engineering and the life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function. (Langer, R., and Vacanti, J. P., Science (1993) pg. 260, 920)

But later reviewers realized the necessity of distinguishing tissue regeneration with the help of scaffolds from the conventional methods of inducing cell growth solely with the help of growth and differentiation factors.

The use of scaffolds to regenerate tissues is a sophisticated technique and presents promising possibilities to improve and revolutionize the field of medicine and healthcare in ways that were not known before. But before we proceed to discuss the wonders of scaffolds themselves, let us look at the basic definitions of regenerative medicine and tissue engineering, and most importantly, why do we need them in the first place?

When cells, tissues or organs of a human body gets damaged or diseased by sudden trauma, illness or genetic anomalies, these building blocks of a human body have to be replaced either by inducing natural cell growth or by transplantation.

Induced growth of cells to replace damaged tissues is done with the help of “growth factors”- proteins that help in differentiation and proliferation of cells; whereas transplantation is simply a technique that involves removal of a required tissue from a ‘donor’ and implanting it the ‘receiver’.

Both procedures have helped mankind in medicine and healthcare sector for long; but these conventional procedures come with their own limitations.

Whilst stem cell growth and culture yields cells at a reasonable rate, their potential of differentiation is quite limited. In other words, though we can obtain a significant quantity of cells from two dimensional cultures, all the cells are of the same type; and hence their use is limited to simpler surgeries like skin grafts, etc.

Or stating it more simply, it’s not possible to grow a complex organ like heart or bone tissue on a petri dish.

Transplantation offers an alternative for replacement of complex tissues like liver and bone marrow, but the issue of shortage of donors will always pose a constraint for wide scale application of this technique.

“Scaffolds” offer an answer to this problem. Scaffolds are matrices designed as a three-dimensional mirror image of an organ or tissue to be replaced on which cells grow and regenerate the needed tissues.

Scaffolds which are usually made of polymer and textile materials are supplied with cells that need to be regenerated, and are then placed in either a bio-reactor (in vitro) or in a human body (in vivo) to provide the environmental parameters required for cell growth.

After the polymer and textile materials have served their function as a template and the new organ has been formed, the scaffolds are absorbed into the tissues and the new construct can be used an implant.

Scaffolding provides a promising way to reconstruct complex tissues like cardiac, articular and bladder tissues. It is probably due to this degree of sophistication that scaffolds offered that has led the  reviewers to redefine regenerative medicine in a new way.

For instance, Y. Ikada (September 2009) defines the regenerative medicine as follows:

1. Without Scaffolds – Cell therapy (Internal medicine)
2. With Scaffolds – Tissue Engineering (Surgery)

There are various property requirements that a scaffold has to fulfill to perform its function successfully. These include strength, rigidity, biocompatibility, large surface area to volume ratio, interconnected micro-pores (with the required pore size 100 and 500 mm), absorption kinetics and biodegradation rate, etc.

Fibrous materials (knitted, non woven and bonded) are one class of materials that fulfill these requirements and have therefore found acceptance for use in the fabrication of scaffolds.

 Materials used for constructing scaffolds include a family of aliphatic polyesters: Poly (glycolic acid) (PGA), poly (lactic acid) (PLA), and their copolymers poly (lactic acid-co-glycolic acid) (PLGA).

Other than the synthetic materials, natural macromolecules are also widely employed in scaffold fabrication. These include collagen which is a fibrous protein and also silk.  The table summarizes the textile technologies that are used for construction of scaffolds.

Textile materials and technologies have long seized to serve solely the purposes related to apparel and other conventional product requirements. Their use has been extended to a large area of modern technology such as technical textiles, nanotechnology and composites.

Textiles, in the form of scaffolds, have a potential of providing solutions to many problems in medical and healthcare sector. An exciting new technique of preparing scaffolds through electrospinning of textile materials is also attracting attention of scientists and industrialists, because of its potential to offer greater strength requirements. The world of invention knows no bound, and textile materials, in the form of scaffolds, are a classic example of scientific innovation.

References

• Gandhi, M.R., F.K.K.O., (2007). Producing nanofiber structures by electrospinning for tissue engineering. In Brown P.J and Stevens. K.(Ed.) Nanofibres and nanotechnology in Textiles.(pp 22-45)  U.K, Woodhead Publishing Limited.
• Ikada, Y. (April 2006).Challenges in tissue engineering. J. R. Soc. Interface, 3. 589–601
• Liu C.,Xia Z., Czernuszka J.T., (2007). Design and development of three dimensional Scaffolds for Tissue Engineering. Institution of Chemical Engineers, 85, 1051–1064.
• Ma, P.X. (May 2004) Scaffolds for tissue engineering. Materialstoday
• Smith. M., (2001). Fibrous Scaffolds for Tissue Culturing. In Anand.S. (Ed) Medical Textiles (pp 173-179) U.K, Woodhead Publishing Limited.