Textile Scaffolds for Tissue Engineering: Characteristics, Functions and Applications
Mashood Ahmed
Department of Textile Engineering
University of Management and Technology (UMT)
Lahore, Pakistan
Email: mashood093@gmail.com
Introduction:
Use of textile structures in a medical field is not recent because sutures, which for centuries have been used for closure of wound or incision, or fundamentally textile structures. Due to recent advancements in textile engineering and bio-medical research the use of textiles in surgery is growing. They are routinely used to supplement or replace the functions of living tissues of the human body. Soft tissue replacement or implants such as vascular graft, skin grafts, hernia patches and artificial ligaments are made of textile filaments. Moreover polymers reinforced with textiles, called polymer composite materials, are also considered in hard tissue replacements, spine rods, intervertebral disks and spin cages.
Textile structures are an important class of porous scaffolds used in tissue engineering. The basic concept of tissue engineering is to regenerate or to grow tissues or organs by culturing isolated cells from the tissue or organ of interest on porous biodegradable scaffolds as templates. The scaffold acts as an extracellular matrix for the adhesion and growth and/or regeneration of cells. The cells transplanted onto scaffolds multiply and produce tissue matrices that can take up and secrete protein, generate force and resistance, constrain permeability, and exhibit other life processes.
Textile Scaffolds: The scaffolds are three dimensional, porous structures encourage cell attachment, proliferation and migration through an interconnected network of pores.
Fig: Textile Scaffolds
Textile scaffolds are artificial devices, designed to act as templates for attached cells and newly formed tissues.
Nowadays textile scaffolds are commonly used in various biomedical applications, and are generally referred to as ‘medical textiles’. Based on the application, they may be grouped into three broad categories, namely healthcare and hygiene textiles, extracorporeal devices and surgical textiles.
Materials Used in Textile Scaffolds: The scaffolds are made up of fibers which are synthetic and natural. Synthetic fibers can be Bio-Degradable and Non-Biodegradable and Natural fibers are Human, Plant, or Plant Tissue.
Among the various materials used for scaffolds, woven fabrics are normally rigid and inflexible due to the tight interlacing of yarns. The next stiff and strong scaffold is the braid. Knits (non-woven) and foams display the lower end of mechanical properties. Of all the scaffolds, knits display considerable deformability and good compliance owing to their looped yarn arrangement. Polymeric scaffold materials used in tissue engineering can be natural or synthetic.
Fibers Used:
Natural materials: Such as Collagen, Keratin, Silk, Chitin, Fibroin, Chitosan and Mussel Proteins.
Synthetic materials: The non degradable materials such as Polyethylene, PTFE etc.
Synthetic bio degradable polymer: Such as Polyester, Poly anhydride, Poly Orthoesters, Polyphosphazenes, etc.
Textile Scaffolds for Tissue Engineering: Cells are isolated from the patient’s body, and expanded in a petridish in laboratory. Once we have enough number of cells, they can be seeded on a polymeric scaffold material, and cultured in vitro in a bioreactor or incubator. When the construct is matured enough, then it can be implanted in the area of defect in patient’s body.
Fig: Basic principles of tissue engineering
Synthesis of Scaffolds: A number of different methods have been described for preparing porous structure to be employed as tissue engineering scaffolds.
Currently, two methods, phase separation and electro spinning have been used to prepare the nanofiber with diameters ranging from 100 to 900 nm.
Scaffolds Structural Design Parameters: For a scaffold to function effectively
It must possess the optimum structural parameters, conducive to the cellular activities leading to new-tissue formation
These include cell penetration and migration into the scaffold, cell attachment onto the scaffold substrate, cell spreading and proliferation and cell orientation.
Characteristics of Textile Scaffolds:
Porosity for cell migration
Balance between surface hydrophilicity and hydrophobicity for cell attachment
Mechanical properties comparable to natural tissue to withstand natural loading conditions
Degradation capability so that it gets completely reabsorbed after implantation
Nontoxic by products
3D matrix.
Basic Functions of Textile Scaffolds:
Scaffolds Functions
Scaffold Design Parameter
Non inflammatory or non toxicity.
Biocompatible, non-Toxic and non-carcinogenic.
To assist in the growth of 3-d tissue & organs.
3-d scaffold of specific shape.
To promote cell proliferation and migration leading to tissue growth throughout the scaffold.
Optimum pore size to allow for cell penetration, with high porosity & interconnectivity between pores.
To allow for the movement of nutrients and waste in & out of the scaffold.
High porosity and interconnectivity between pores.
The scaffold may degrade to leave only natural tissue.
Rate of degradation to match the rate of tissue formation.
Support for developing tissue.
Scaffold should have mechanical properties of developing tissue.
Applications of Textile Scaffolds in Tissue Engineering:
A knitted Poly (lactic-glycolic acid) scaffold seeded with bone marrow stem cells.
A micro braided tube was successfully used as a nerve guide growth conduit in regenerating a 10mm nerve gap with a 90% success rate.
A multi layer-knitted PGLA and Polycaprolactone co-fiber as also been used for skin tissue generation, Heart valve, Tendons and Ligaments.
A woven polyethyleneterephthalate textile rolled into a cylinder was successfully used for dynamic hepatocyte cell culture.
A composite tube made of braided PGLA coated with a porous PLA-PCL copolymer has been used for blood vessel regeneration, with its elasticity adjusted to mimic the native blood vessel.
Application of electro spun poly (l-lactic) acid nanofibrous scaffold seeded with chondrocytes for cartilage tissue engineering.
The range of tissue engineering applications has expanded in recent years. Some typical examples, with special emphasis on the use of textile scaffolds, are described here.
Skin grafts: Skin grafts are perhaps the most successful tissue-engineered constructs. It is a cryopreserved dermal substitute, in which human fibroblast cells derived from newborn foreskin tissue were seeded on a biodegradable polyglactin mesh scaffold. Although there have been considerable improvements in tissue engineered skin grafts, none of them could reproduce the normal architecture of natural skin, including hair follicles, Langerhans cells, sebaceous glands, and sweat glands.
Vascular grafts:
An important requirement for tissue-engineered vascular grafts is that the tubular conduits are made of materials capable of incorporating into host tissues with a functioning self-renewing endothelial layer. Scaffold materials can be either synthetic or natural polymers.
Major disadvantages of natural material-based scaffolds are their rapid absorption rate and poor mechanical strength. To improve both biocompatibility and mechanical strength, many novel grafts use a combination of synthetic and biological materials.
Traditional problems associated with vascular grafts, including clotting and scar tissue formation, is still a problem for current vascular grafts and this has prevented new grafts from entering clinical trials.
Tissue-engineered liver: Several extracorporeal bioartificial liver (BAL) systems have been developed to support essential hepatic functions. In a typical BAL device, patient’s plasma or blood is circulated through a bioreactor with immobilized primary hepatocytes or hepatoma cell lines between artificial plates or capillaries.
Nerve grafts: Neural tissue engineering involves the use of biomaterials as scaffolds with tissue-specific architecture and a controlled pore structure that facilitates growth and organization of resident cells for nerve repair. Nerve guidance conduits to bridge the gap between the nerve stumps and to direct nerve regeneration have been developed recently.
Many biodegradable and non-biodegradable materials have been investigated to construct nerve conduits such as collagen, polyethylene, PLGA, polyphosphoester, silicone, PTFE. Electrospun biodegradable PLA nanofibers have been used to fabricate a nerve conduit.
Bone grafts: Tissue engineering in bone has also undergone major advances in recent years. Natural materials such as collagen, fibrin, chitosan, hyaluronic acid (HA) and the synthetic polymers such as PCL. poly(propylene fumarates), poly(phosphazenes), and PLGA have been applied to establish 3D bone scaffolds.
Other organs:
Besides the applications mentioned above, rapid developments in tissue engineering have extended its scope to encompass many other important human organs, such as cartilage, ligament, heart, pancreas, larynx, and cornea.
Smart textile scaffolds:
The convergence of information technologies and advances in textile materials has created smart textile fabrics. Smart textiles are intelligent textile structures or fabrics that can sense and react to environmental stimuli, which may be mechanical, thermal, chemical, biological, and magnetic amongst others. The initial application was in military and defense systems and it is currently being introduced in biomedicine and tissue engineering.
Smart textile scaffolds made of shape memory materials. These shape memory scaffolds can be transferred into memorized, permanent shapes from their original temporary configuration upon an external stimulus, e.g. an increase in temperature.
Conclusion:
Scaffolds are a boon to Mankind
Textile structure are particularly attractive to tissue engineering because of their ability to tailor a broad spectrum of scaffolds with a wide range of properties.
Further systematic study is necessary to design a optimal scaffold for each tissue applications. Textile scaffolds are extreamly versatile and therefore ideal for encouraging cells to recreate tissue geometry.
They are easily adapted to meet different cell requirements which will be an emerging trend in Medical Textiles.
References:
Advanced Textiles for Wound Care Edited by S. Rajendran
Advances in Polymer Coated Textiles Edited by Guneri Akovali
Smart Fibres, Fabrics and Clothing Edited by Xiaoming Tao
Medical and Healthcare Textiles Edited by S. C. hand, J. F. Kennedy, M. Miraftab and S. Rajendran
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
