Silk as biomaterial. Preparation, Application, Mechanical Properties

Silk as a biomaterial
Preparation, mechanical properties and application.
Omoyayi Ibrahim O.
20142575
Mechanical properties of sIlk
Source;
Silk-based biomaterials
Gregory H. Altman,Frank Diaz,Caroline Jakuba,Tara Calabro,Rebecca L. Horan, Jingsong Chen,Helen Lu,John Richmond, David L. Kaplan
The ability to control silk material properties offers a number of advantages over other biopolymer systems like collagen, chitosan, and alginate. The formation of silk structures begins with fibroin proteins aggregating into protein globules in solution.

The fibroin globules then aggregate to form larger bulk macromolecular structures that can then be modified through a variety of processing methods.

The silk material properties can then be controlled through inducing protein secondary structure formations, such as alpha-helices and beta-sheets, through a variety of post-processing techniques.

Liquid crystalline phases and conformational polymorphism have been implicated in the biological processing of these proteins to contribute to the architectural features within the fibers.
SIlk Preparation, Structure and properties
Jin and Kaplan, 2003; Keten et al., 2010; K ö nig and Kilbinger, 2007
Jin and Kaplan, 2003).
Winkler S, 2000
Fig 3. One of many silk cords manufactured by the twisting equipment
Fig 2. The Twisting Equipment
Fig. 1. (A) SEM of raw virgin B. mori silk fibers prior to extraction showing the gum-like sericin proteins coating the core fibroin and (B) following extraction at 90 degree C for 60 min.
Source;
G.H. Altman et al. / Biomaterials 24 (2003) 401–416
Silkworm cocoon is composed primarily of three proteins, which consist of the glue-like glycoprotein sericin and heavy and light chains of the structural fibrous protein fibroin.

It has been shown that fibroin may be resolubilized into an aqueous solution, and then formed into a number of different geometrical forms to produce 'regenerated' silk .

Derived silk is highly biocompatible within the body, and also demonstrates an impressive range of material properties based on a variety of processing protocols.

Regenerated silk fibroin solution is produced by dissolving silk cocoons into water through the use of chaotropic agents (heavy salts), to disrupt the high degree of hydrogen bonding that exists between the individual protein molecules.


Kaplan, 1994
Preparation of silk as a biomaterial
Altman et al., 2003
Keten et al., 2010)
Silk fibroin protein can be degraded through a number of naturally occurring proteolytic enzymes.
Horan et al., 2005;
Applications…
Skin / Wound Healing
Fibroin films and fibroin-alginate sponges have been found to enhance skin wound healing.

Keratinocytes also proliferate on woven fibroin meshes,used for wound healing applications.

A fibroin-chitosan blend has been reported to
give superior performance when tested for repair of ventral hernias.
Topics in Tissue Engineering, Vol. 4. Eds. N Ashammakhi, R Reis, & F Chiellini © 2008.
Bone
D. L. Kaplan has conducted the majority of research into the use of fibroin based
scaffolds for cartilage tissue engineering.

Ligament /Tendon
Cartilage
Wang, Y.Z et all 2005.
Marolt, D., et all 2006
Kaplan, D.L. 2005
Fibroin Films electrospun processed into a 3-D porous scaffold by salt-leaching, growth factors etc.
Kaplan, D.L. 2005
Vascular Tissue
B. mori silk (after sericin extraction) wound into strands wound into yarns, has been investigated for its potential for ligament tissue engineering .
Matrices have suitable mechanical properties for reconstruction.
Surface modification allows tailoring of the mechanical properties.
Silk fibroin nets have been reported to
support endothelial cell attachment,
Recent evidence suggests that sulphonated silk fibroin films have suitable mechanical properties for use as artificial blood vessels.
Couet, F et ll, 2007
Fini, M., 2005
Applications…
Silk fibers are composed primarily of 2 types of proteins:
Gum-like Sericin,
Fibroin, the core filaments of silk.

Fibroin comprised of highly organized b-sheet

The ease of reconstruction during preparation of the
Fibroin allows structural conformational changes in
*protien structure *crystalinity *surface modification
allowing easy access to the mechanical properties
as desired by the biomedical application.

conclusion
A few brain teasers for you…..
Q1: The scientific name of the silkworm is
a. Morus alba
b. Bombyx mori
c. Caterpillar
d. None of these

Q2: What is my name?

rEFERENCES
Moy RL, Lee A, Zalka A. Commonly used suture materials in skin surgery. Am Fam Physician 1991;44(6):2123–2128. [PubMed: 1746393]
Winkler S,Kaplan DL. Molecular biology of spider silk. Rev Mol Biotech 2000;74:85–93.
Vollrath F, Knight DP. Liquid crystalline spinning of spider silk. Nature 2001;410(6828):541–548. [PubMed: 11279484]
Silk-based biomaterials Gregory H. Altman,Frank Diaz,Caroline Jakuba,Tara Calabro,Rebecca L. Horan, Jingsong Chen,Helen Lu,John Richmond, David L. Kaplan
Zhou CZ, Confalonieri F, Medina N, Zivanovic Y, Esnault C, Yang T, Jacquet M, Janin J, Duguet
M, Perasso R, Li ZG. Fine organization of Bombyx mori fibroin heavy chain gene. Nucleic Acids Res 2000;28(12):2413–2419. [PubMed: 10871375]
Yamaguchi K, Kikuchi Y, Takagi T, Kikuchi A, Oyama F, Shimura K, Mizuno S. Primary structure of the silk fibroin light chain determined by cDNA sequencing and peptide analysis. J Mol Biol 1989;210(1):127–139. [PubMed: 2585514]www.dreamstine.com/photos-images/silkworm.html
www.wikipedia.org/wiki/sericulture
www.andyuong.wix.com/sericulture
http://www.designboom.com/history/silk2.html
Wang, Y.Z., Kim, U.J., Blasioli, D.J., Kim, H.J., Kaplan, D.L. In vitro cartilage tissue engineering with 3D porous aqueous-derived silk scaffolds and mesenchymal stem cells. Biomaterials 2005; 26(34):7082-7094.
Couet, F., Rajan, N., Vesentini, S., Mantovani, D. Design of a collagen/silk mechanocompatible composite scaffold for the vascular tissue engineering: Focus on compliance.
Key Engineering Materials 2007; 334-335 II:1169-1172.

THANK YOU
Preparation of silk
1:
raising silkworms &
harvesting cocoons
2:
thread extractionstep
3: dyeing
4: spinning
5: weaving
6: ikat
1:
www.designboom.com/history/silk2.html
2
3
4
5
6
Mechanical properties of sIlk
Source;
Silk-based biomaterials
Gregory H. Altman,Frank Diaz,Caroline Jakuba,Tara Calabro,Rebecca L. Horan, Jingsong Chen,Helen Lu,John Richmond, David L. Kaplan
History / fun fact of Silk
A Chinese tale of the discovery of the silkworm's silk was by an ancient empress Lei Zu, the wife of the Emperor.
She was drinking tea under a tree when a silk cocoon fell into her tea and the hot tea loosened the long strand of silk. 
As she picked it out and started to wrap the silk thread around her finger, she slowly felt a warm sensation.
When the silk ran out, she saw a small larva. She realized that this caterpillar larva was the source of the silk.
She taught this to the people and it became widespread.
Chinese Empress
Drinking tea under a tree
Silkworm cocoon falls into hot tea
Silk strand unravels and larva exposed
Slide share images
Introduction

Similar to how humans use concrete, metals, and plastics to build the world around us, arthropods have employed nearly 40000 different silk proteins to produce varyings tructures such as webbing, nests, cocoons, and underwater air sacks

Silks represent a unique family of structural proteins that are biocompatible, degradable, mechanically superior, and are amenable to aqueous or organic solvent processing.

They can be chemically modified to suit a wide range of biomedical applications.

Silks have been investigated as biomaterials due to the successful use of silk fibers.

Difference in species gives different primary amino acid sequence.

Recently regenerated silk solutions have been used to form a variety of biomaterials, such as gels, sponges and films, for medical applications.

Degradability of silk biomaterials can be related to the mode of processing and the corresponding.


Moy RL, Lee A , 1991
Vollrath F, Knight DP , 2001
(Kaplan, 1994)
The rearing of silkworms for the production of raw silk is Sericulture.


Bombyx mori is the most widely used species of silkworm and intensively studied.

serIculture
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