C H I T O S A NCrawling from crab-shells to Bio-textiles

Submitted to:

Kayode Adekunle

SUSTAINABLE MATERIALS

Submitted by: Ubaid ur Rehman [X080310@utb.hb.se]

Abstract:

Chitosan, after cellulose, is the most abundant natural amino polysaccharide and is annually

produced roughly around as much as cellulose. It is produced by deacetylation of chitin which is

obtained from marine crustaceans. Chitosan, unlike chitin is soluble in aqueous acidic medium

and is used in many applications such as food, cosmetics, pharmaceutical and biomedical. In this

paper the use of chitosan in bio-textiles for use in medical is discussed.

Introduction:

Chitin, the main source of chitosan occurs in nature as ordered crystalline micro fibrils

forming structural components in the exoskeleton of arthropods or in the cell walls of fungi and

yeast. It is produced by a number of other living organisms in the lower plant and animal

kingdoms, serving in many functions where reinforcement and strength are required.

Despite its widespread occurrence, the main commercial sources of chitin have been crab

and shrimp shells up to now. Industrially, chitin is extracted from crustaceans by acid treatment

to dissolve calcium carbonate and then treated with alkali to solubilise proteins. The extracted

chitin is again treated for decolourization purpose to get a colourless product. It is then graded in

terms of purity and colour because the residual protein and pigment can cause problems for

further use, especially for biomedical purpose. Finally chitin is partially deacetylated under

alkaline conditions to get chitosan.

Fig. 1 Structure of cellulose, chitin, chitosan

SWOT Analysis:

S T R E N G T H S

Hi absorbency. Ease of application and removal. Bacterial barrier. Comfort. Haemostatic. pH sensitive. Sustainable

O P P O R T U N I T I E S

Mass availability; mass production Under extensive research for various

medical applications. Other technical applications areas

W E A K N E S S E S

Wet spun. Cost (as much as 7.5$/10g). pH sensitive. Underutilized. Producing facilities Government (legislations)

T H R E A T S

Validation process gratification Under investigation whether if it is

suitable for people allergic to shellfish or not?!

Medical applications of Chitosan:

The cationic character of chitosan is unique as it is the only pseudo-natural cationic

polymer. The film forming properties (which is because it is soluble in acidic medium) and

biological activity of chitosan invite the researchers to explore its potential use as a biomaterial. It

is extensively being used in wound dressings by Hemcon as war bandage because of its unique

haemostatic nature, low toxicity and tensile strength retention in many situations. It has been

tested on US marines in Iraq and made significant improvements in fatalities due to blood loss.

In burn patients, where standard of care involves application silver sulfadiazine cream,

silver toxicity is a major concern because of reduced skin barrier. Membranes, including

chitosan, reduce this toxicity by entrapment of silver ions in the matrix. Chitosan is studied for

stimulating the growth of fibroblast in the wound and promote the tissue growth.

Biocompatible characteristic of chitosan makes it possible to be used as surgical sutures; it

is useful as absorbable suture material. Chitin sutures resist attack in bile, urine and pancreatic

juice, which are problem areas with other absorbable sutures.

Chitosan is non-toxic and easily bio-absorbable with gel forming ability at low pH. It also

has antacid and antiulcer activities which prevent or weaken drug irritation in the stomach.

Moreover, chitosan matrix formulations appear to float and gradually swell in an acid medium.

All these interesting properties of chitosan make this natural polymer an ideal candidate for

controlled drug release formulations. Due to the versatility in processing of chitosan, controlled

drug delivery can be achieved in several ways such as using chitosan based hydro-gels, chitosan

tablets because they are reported to be useful in pharmaceutical preparations, chitosan

microcapsules/microspheres (a spherical particle with size from 50nm to 2mm, containing a core

substance) and chitosan based trans-dermal drug delivery system.

Chitosan possesses all the properties that are necessary for manufacturing an ideal contact

lens. It includes Optical clarity, mechanical stability, sufficient optical correction, gas

permeability (specifically towards oxygen), wet ability, and immunological compatibility.

Contact lenses made from chitosan are clear, tough and posses other physical characteristics for

example modulus, tensile & tear strength, elongation, water content and oxygen permeability.

Additionally the anti-microbial and wound healing quality of chitosan in conjunction with good

film forming ability make it suitable for development of ocular (related to eye) bandage lenses.

Polymeric nano-fibers that mimic the structure and function of the natural extracellular

matrix (ECM) are of great interest in tissue engineering as scaffolding materials to restore,

maintain or improve the function of human tissues. The natural ECMs in the body are mainly

composed of two classes of extracellular macromolecules: proteo-glycans and fibrous proteins

with fiber diameters ranging from 50 to 150 nm, depending on tissue type. Studies show that the

material size feature could substantially influence the morphology and function of cells grown on

the ECM. The cells attachment and proliferation were found to be good on micro and nano-

structured materials.

During a study chitosan/PEO nanofibrous scaffolds promoted the attachment of human

osteoblasts and chondrocytes and maintained characteristic cell morphology and viability

throughout the period of study. Chitosan nanofibrous matrix is of particular interest in tissue

engineering for controlled drug release and tissue remodeling. According to another study

Chitosan/PEO nano-fibers showed the biocompatibility with chondrocytes. Cells were attached to

the chitosan/PEO nano-fiber matrix and the results indicated that the electro-spun chitosan/PEO

mats could be used for cartilage tissue repair.

Conclusion:

Chitosan has a wide range of applications in various fields of science. They may be

employed for example to solve numerous problems in environmental and biomedical

engineering. Chitosan can be easily molded to various forms and its derivatives are digested in

vivo, thus it appears that this material can be a most interesting candidate for use in biomedical

applications. Another advantage of chitosan over other polysaccharides is that its chemical

structure allows specific modifications without too many difficulties, i.e. specific groups can be

introduced to design polymers for selected applications.

Chitosan is a natural material with virtually no environmental impact except that a lot of

chemicals are used to extract from the source, yet it should be remembered that it is obtained by

making use of the waste material rejected from fisheries which a renewable resource if used

responsibly.

References:

Marguerite Rinaudo, 2006, Chitin and chitosan: Properties and applications.

Majeti N.V. Ravi Kumar, 2000, a review of chitin and chitosan applications.

Hitoshi Sashiwa*, Sei-ichi Aiba, 2004, chemically modified chitin and chitosan as biomaterials.

Bhattarai N, Edmondson D, Veiseh O, Matsen FA, Zhang M., 2005, Electro-spun chitosan-based

Nano-fibers and their cellular compatibility.

Mo X, Chen Z, Weber HJ., 2007, Electrospun nanofibers of collagen-chitosan and P(LLA-CL)

for tissue engineering.

Shigemasa Y, et al., 1996, Biotechnology Genet Eng Rev.

Tsipouras N, et al., 1997, Clinical Chemistry.

http://www.drugs.com/npp/chitosan.html, Feb’10.