Silk Fibroin: An Ideal Scaffold for Tissue Engineering
Aritra Kumar Dan
M .Tech in Biotechnology
School of Biotechnology, KIIT
I would like to acknowledge Dr. Pankaj Kumar Parhi for his help.
Tissue Engineering is a novel approach with the combination of Biology and Engineering for developing the functional substitute of damaged tissue. The most vital part of tissue engineering is the “scaffold” because it provides a micro-environment for the growth of stem cells. The ideal scaffold should have similar structures and functional activity to that of the native extracellular matrix. As a result, the designing of appropriate identical scaffolds becomes challenging.
The designing and fabrication process of an ideal scaffold begins by the selection of a potential biomaterial. An ideal biomaterial has some unique properties like bioactivity, biocompatibility, immuno-compatibility, mechanical resilience, and bio-degradability. With these properties, they are considered a suitable source for substantial usages in different biomedical applications, especially in tissue engineering. In particular, the SF is noticeably found as the most promising green polymeric biomaterial for tissue engineering due to its properties including biocompatibility, biodegradability, low immunogenic response, and easier process ability. The above salient features could easily be attained by the Silk Fibroin (SF) biomaterial because it has a similar structure in comparison to the cell-extracellular matrix. Natural raw silk is made up of sericin (approx 20-25%) and fibroin (approx 62.5-67%), which have different percentages of amino-acids and configurations, and the rest is water with the mineral salts.
Applications of SF spans a wide range of biomedical applications, namely in implantable devices, as supportive matrix-like scaffolds, blood vessels, cartilage, and nerve tissue engineering (Table). Further, due to its excellent mechanical properties, water vapor, and oxygen permeability, SF with chitosan (a blended film) could be ideal for utilizing in wound dressing and artificial skin applications.
Laboratory for Stem Cells and Tissue Engineering, Department of Biomedical Engineering at Columbia University reported that stem cells are isolated from the human adipose tissue and utilize as a seed on the surface of the SF and chitosan scaffold for enhancing the wound restoration in a murine soft tissue injury. Another challenging application of this SF is neural or nerve tissue engineering by regeneration and repair of the central nervous system (CNS).The nervous system is the most crucial and complex part of our body.
The damages caused either by injury or diseases can result in serious chronic and acute neurodegenerative diseases. Some research studies observed that there was a restricted improvement in function due to the limited ability of the CNS to regenerate. The most complicated problem in neural or nerve tissue engineering is the stimulation of the regenerative damage nervous tissue and the regenerative capacity of that tissue. For the regeneration of the damaged nervous tissue a three-dimensional nano scaffold (3DNSs) has been utilized, that is constructed by SF, polyethylene glycol (PEG), and polyvinyl alcohol (PVA). The next is Bone Tissue Engineering, which occurs by regenerate bones through the osteogenesis process. In bone tissue engineering, biocompatibility is one of the most crucial factors. Specific mechanical, physical, and degradation properties are essential for bone tissue engineering. SF is an ideal biomaterial for scaffold preparation in bone tissue engineering because it has some essential characteristics like high mechanical strength, excellent elasticity, biocompatibility, and controllable biodegradability.
| Composition | Method | Microstructure | Tissue or Organ |
| SF | Lyophilization | Conduit (inner diameter 1.6 mm,wall thick 0.75 mm) | Neural |
| SF | Lyophilized, redissolved in HFIP, dried | Mixed pore (pore sizes 112-500 μm) | Bone |
| SF | Chemical crosslinking / Lyophilization | Mixed pore | Bone |
| SF | Lyophilization | Lamellar structures with Lamellae proceeding parallel | Cartilage |
| SF | Dried 24 hours | Pore (size was ~ 550_30 μm) | Cartilage |
| SF | Lyophilization 24 hours | Microporous silk sponges | Ligament and Tendon |
| SF Fibers | Braided on the polyvinylchloride rod | Vascular (1.5 mm in inner diameter and 10 mm in length) | Vascular |
| SF/Collagen | Physical cross-linking | Thin fibroin films | Hepatic Tissue |
| SF/Collagen | Chemical cross-linking / Lyophilization | Mixed pore | Bone |
| SF/Hyaluronic acid | Physical cross-linking | Silk conduits 10 mm in length | Neural |
| SF/Chitosan | Lyophilization | Sheet structure | Neural |
| SF/ Chitosan | Chemical cross-linking (genipin powder) | Different pore sizes and distinct
morphologies |
Cartilage |
| SF/Alginate | Lyophilization | Stripe-type porous morphology | Skin |
| SF/Hyaluronic acid | Chemical cross-linking (genipin powder) | Patches (diameter 13 mm, thickness
200 μm, mass 20–25 mg) |
Cardiac |
| SF/Collagen/Heparin | Lyophilization | mixed pore | Vascular |
| SF/PEO | Electrospun silk | Fiber (diameter 170–570 nm)/
vascular (1.5–4.0 mm) |
Vascular |
| SF/PEO Blends | Electrospun silk | Pore (average pore size of 8 μm) | Bone |
| SF/P(LLA–CL) | Electrospun silk | Conduit (length 12 mm, diameter
1.4 mm, thickness 0.3 mm) |
Neural |
| SF/PLGA | Electrospun silk | Fiber (diameter 200–700 nm) | Ligament and Tendon |
The medical field has revolutionized in recent years, and there is a paradigm shift of attention toward the treatment approach through tissue engineering. The significance of scientific and technological gaps in bio-fabrication could resolve up to a considerable extent by investigating in the depth of the biomaterial research domain. Further advances in the fictionalization of existing and novel approaches could be one of the promising areas of research for the futuristic prospective on tissue engineering.
Reference (Dec-20-A10)
