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Chitosan and/or Cellulose Yoldaş SEKİ Faculty of Arts & Sciences Chemistry Dep http: //kisi. deu. edu. tr/yoldas. seki
Chitosan n Chitosan (2 -amino-2 deoxy-(1→ 4)-β-D- glucopyranan), a polyaminosaccharide, normally obtained by alkaline deacetylation of chitin is the principal component of living organisms such as fungi and crustacea.
What is the importance of DA? You will buy Chitosan… The degree of N-acetylation (DA) together with the molecular weight are the most important parameters for its characterization. The DA, which is by definition the molar fraction of Nacetylated units, is a structural parameter influencing charge density, crystallinity and solubility, including the propensity to enzymatic degradation, with higher DAs leading to faster biodegradation rates
What are the properties of Chitosan ? n 1 - Chitosan is a linear polymer of mainly anhydroglucosamine which behaves as a linear polyelectrolyte at acidic p. H n 2 - Chitosan is nontoxic and bioabsorbable. n 3 - At p. H below 6. 5, chitosan in solution carries a high positive charge density, one charge per glucosamine unit. n 4 - Since chitosan is one of the few cationic polyelectrolytes, it is an exception to the current industrial high molecular weight polysaccharides, which are mostly neutral or polyanionic.
What are the biomedical applications? Chitosan is being evaluated in a number of biomedical applications icluding wound healing and dressing, dialysis membranes, contact lenses, fibers for digestible sutures, liposome stabilization agents, antitumor uses and drug delivery uses and controlled-release systems
In these uses chitosan’s key properties are : n 1) biocompatibility n 2) nonantigenicity n 3) nontoxicity (its degradation products are known natural metabolites) n 4) the ability to improve wound healing/or clot blood n 5) the ability to absorb liquids and to form protective films and coatings, and n 6) selective binding of acidic liquids, thereby lowering serum cholesterol levels.
How can Chitosan be used in orthopedics? n 1 - Its enzymatic degradability associated to its structural similarity to extracellular matrix glycosaminoglycans makes it an attractive biopolymer for bone tissue repair. n 2 - Numerous bone filling materials have been developed in which chitosan is used in combination with calcium phosphates, essentially as a binding agent, or associated to biological signaling molecules
Can Chitosan be used as nonprotein temporary scaffold? n In addition, its versatility to be processed into injectable, porous and membran forms without use of toxic solvents makes chitosan an interesting material to be used as a non-protein temporary scaffold, for bone regeneration. Presently, an increasing number of anchorage-dependent cells, including bone cells, are being cultured on 2 -D and 3 -D chitosan-based matrices, envisaging cell-based regenerative therapies.
What is the effect of DA of chitosan on cell properties? n Cell adhesion, migration and cell growth kinetics of a number of cells, including keratinocytes and fibroblasts, are known to depend on the DA of chitosan, lower DAs favoring cell adhesion. However, no osteoblast adhesion studies have been reported.
What is P-Chitosan ? Does P-Chitosan nucleate calcium phosphate ? n The ability of phosphorylated chitosan (P-chitosan) membranes to nucleate calcium phosphates under simulated physiologic conditions, was investigated
What is the procedure ? n The membranes M. A. Barbosa et al. / ITBM-RBM 26 (2005) 212– 217 215 were immersed in Ca(OH)2 or Na. OH solutions, in order to obtain the Ca or the Na salts, respectively.
What is the result? n SEM-EDS studies revealed the presence of a calcium phosphate mineral layer all over the surface of Pchitosan membranes, after incubation in Ca(OH)2 solution.
What else ? n During the immersion in simulated body fluid (SBF), a multilayered porous mineral structure composed of a partially carbonated and poorly crystalline apatite was formed on the surface of these membranes,
But chitosan ( Drawbacks? ? ) n has some drawbacks, it is only soluble in aqeous medium in the presence of a small amount of acid such as Ac. OH and its mechanical properties are not good for some biomedical application. Therefore many researchers tried to modify its properties.
How can chitosan be modified ? In the past few years n a number of publications appeared on the blending of chitosan with various polymers such as poly(vinyl alcohol) (Mucha & Pawlak, 2005; starch (Pawlak & Mucha, 2003), cellulose Wu, Yu, Mi, Wu, Shyu and Peng, 2004) and its derivatives (Mucha & Pawlak, 2005; Pawlak & Mucha, 2003), etc
Celulose The cellulose molecule –(C 6 H 10 O 5)
What is the monomer of Cellulose ? n Cellulose monomers (β-glucose) are linked together through 1→ 4 glycosidic bonds by condensation
What is the source of Cellulose ? n Cellulose is a common material in plant cell walls n Cellulose is found in plants as microfibrils (2 -20 nm diameter and 100 - 40 000 nm long). These form the structurally strong framework in the cell walls n Cellulose is the most abundant form of living terrestrial biomass
What is the most common biopolymer on Earth? n The primary cell wall of green plants is made primarily of cellulose; the secondary wall contains cellulose with variable amounts of lignin. Lignin and cellulose, considered together, are termed lignocellulose, which (as wood) is the most common biopolymer on Earth.
What are the variations among cellulose types ? n Given a cellulose material, the portion that does not dissolve in a 17. 5% solution of sodium hydroxide at 20 °C is α cellulose, which is true cellulose; the portion that dissolves and then precipitates upon acidification is &beta cellulose; and the proportion that dissolves but does not precipitate is &gammal cellulose.
How can we assay Celloluse ? n Cellulose can be assayed using a method described by Updegraff in 1969, where the fiber is dissolved in acetic and nitric acid, and allowed to react with anthrone in sulfuric acid. The resulting coloured compound is assayed spectrophotometrically at a wavelength of approximately 635 nm.
What are the unique properties for medical application? n Nontoxicity (monomer residues are not hazardous to health), water solubility or high swelling ability by simple chemical modification, stability to temperature and p. H variations, and a broad variety of chemical structures. n Biodegradable polymer
What is the other properties? n Ikada has described cellulose as a polymer usually exhibiting relatively low protein adsorption and cell adhesion (particularly blood cells), low immune response (low phagocytosis by macrophages and low interleukin-1 release), and inducing comparatively higher activation of the complement system
n The second line of defense includes four nonspecific mechanical steps: Phagocytes: also known as leukocytes or white blood cells, contain and destroy pathogens by phagocytosis. These include monocytes that enlarge into gigaintic phagocytic cells. These phagocytic cells are called macrophages and are known as natural killer cells or NK cells
n Steps of a macrophage ingesting a pathogen: a. Ingestion through phagocytosis, a phagosome is formed b. The fusion of lysosomes with the phagosome creates a phagolysosome, the pathogen is broken down by enzymes c. Waste material is expelled or assimilated (the latter not pictured) Parts: 1. Pathogens 2. Phagosome 3. Lysosomes 4. Waste material 5. Cytoplasm 6. Cell membrane
n Cellulose is poorly biodegradable in the body and is not digestible, but it can be made hydrolysable by changing its higher order structure
What is the largest application ? n In medicine, membranes for blood purification (haemodialysis) made of cellulosics, are among the largest applications of polymers in therapy .
Derivatives ? n The hydroxyl groups of cellulose can be partially or fully reacted with various chemicals to provide derivates with useful properties. Cellulose esters and cellulose ethers are the most important commercial materials. In principle, though not always in current industrial practice, cellulosic polymers are renewable resources
What is regenerated cellulose hydrogels? n Baquey and coworkers have pioneered and considerably contributed to this field of study by firstly proposing the use of regenerated cellulose hydrogels (RCH) for orthopedic applications. Cellulose Regenerated by the Viscose process (CRV®) was patented and thoroughly investigated in terms of physicochemical, mechanical and biological properties. It was later chemically modified to enhance its bioactivity through modifications such as phosphorylation, grafting of adhesive peptides and oxidation.
How is CRV produced ? n 1 - Briefly, the starting cellulose material (most usually, refined wood pulp) is converted into alkalicellulose by steeping in sodium hydroxide, which is then aged. n 2 - Alkali cellulose is then converted into sodium cellulose xanthate with carbon disulfide, and finally the xanthate is dissolved in dilute alkali, and viscose is regenerated thereof. n 3 - Filtration and purification determine the quality of the final product
Where is CRV used ? n CRV is highly stable to gamma sterilization and ageing. It was investigated as implantable material in orthopedic surgery, as a sealing material for the femoral component in hip prostheses, in place of the acrylic cement. n It was envisaged to take advantage not only of its biostability and good matching with mechanical properties of cortical bone but also of its hydroexpansivity, allowing therefore a satisfactory fixation to hard tissue
The others n 3 - It is cytocompatible although it seemed not to allow proliferation of bone cells, after an initial attachment of the cells. n 4 - The biostability and osteoconduction of this material have been demonstrated in vivo, although a complete osseointegration was not observed
What is CP? n 1 - The applicability of cellulose phosphate (CP) as a biomaterial for orthopedic applications was then investigated to improve the osseointegration of cellulose. n 2 - CP has been used for decades in the treatment of Ca metabolism-related diseases, such as renal stones, due to its high Ca binding capacity, associated with lack of toxicity and indigestibility
Is CP promising alternative biomaterial ? How was it synthesized? n Due to its capability of binding Ca and eventually growth factors, CP can be envisaged as a promising alternative biomaterial, capable of promoting an adequate healing response once implanted. n CP was synthesized according to an optimization of the H 3 PO 4/P 2 O 5/Et 3 PO 4/hexanol method
More about CP In vitro biocompatibility studies in cultured bone cells showed that CP is not cytotoxic, independently of the phosphate content. However, CP promoted poor rates of cell attachment, proliferation and differentiation, which were attributed to the negative charge, associated with the high hydrophilicity of the cellulose derivative .
Finally about CP Finally, animal implantation studies in rabbits revealed the biocompatibility of both unmodified and phosphorylated cellulose, as well as their osteoconductive properties. A full osseointegration could not be observed, although some remodeling activity of the bone tissue was observed when CP was used
What is cellulose viscose sponges ? 1 - Martson et al. reported regenerated cellulose viscose sponges as compatible implantable tissue matrices for bone tissue regeneration. They described this material as slowly degradable. 2 - Cellulose viscose sponges have also been proposed as connective tissue regeneration matrices. Taillac et al. [42, 43] are presently investigating the applicability of oxidized and macroporous regenerated cellulose structures for promoting cell colonization of 3 -D structures.
Where is Oxidized cellulose used ? n Oxidized cellulose is used as a wound dressing and has been proposed for bone regeneration [27– 30].
n Cellulosic materials are increasingly used as reinforcements for thermoplastic matrix composites, due to advantages such as low cost, good mechanical properties, low density, biodegradability and availability of renewable natural resources
Conducting polymer n The development of conducting polymer composites with cellulose (wood) and protein fibres (wool) with the polymer fully encapsulating the fibre, provide the opportunity to develop new hybrid materials that exhibit the inherent proprieties of both components.
n These properties include the tensile strength, flexibility and relatively high surface areas that are associated with cellulose (wood) and wool fibres, and the electronic and chemical properties of conducting polymers. The resulting fibre-conducting polymer hybrid materials can then be incorporated into other commodity/consumer type materials such as plastics, surface coatings and films to impart new or enhanced properties to them.
Chitosan/cellulose n chitosan/cellulose acetate blend, with cellulose acetate (CA) acting as a matrix polymer and chitosan (CS) as a functional polymer have been prepared
What are the properties of blend? n The preliminary study has indicated that the blend hollow fiber membranes have high mechanical strength, tunable hydrophilicity/hydrophobicity and good binding or adsorption capabilities toward heavy metal ions or albumins, even at the presence of a small amount of CS in the blend hollow fiber membranes.
Which forms is it possible ? n Natural or chemically modified polysaccharides, derived from cellulose acetate or chitosan, have the ability to be molded in different forms such as films, fibers and spheres.
What kind of application ? n new hybrids embracing cellulose acetate have been demonstrated to be versatile in having numerous applications such as in exchange processes , as substrates for enzyme immobilization , as semi-permeable membranes
What is the difference and similarity? n Both biopolymers, -chitosan and cellulose acetate, have very similar structural backbones, differing in the presence of either acetate or amino groups distributed along the polymeric chains, as shown schematically in Fig 1
Cellulose ? Chitosan ?
Why is cellulose a blending material for chitosan ? n The interest in using cellulose as a blending polymer for chitosan arises from two facts: (a) cellulose is the most abundant natural biopolymer with relatively strong mechanical strength of up to 1 GN/m 2 (10, 000 MPa) , and (b) cellulose has similar chemical structures as chitosan, providing the possibility of producing a homogeneous blend that combine the unique properties of chitosan and the good availability of cellulose to make chitosan–cellulose hydrogel.
What is limitation of Chitosan ? n The major material limitation of the hydrogel beads is however in their poor acidic resistance and mechanical strength.
How can the chemical stability of chitosan improved ? n Attempts have been made to improve the chemical stabilities of the hydrogel beads in acidic conditions by chemical crosslinking of the surface with crosslinking agents, such as glutaricdialdehyde(GA), ethylene glycol diglycidyl ether (EGDE), and epichlorhydrine . Chemical crosslinking reaction was found to be able to reduce the solubility of chitosan hydrogel beads in aqueous solutions of low p. H values.
Cellulose and… n Jin and Bai  studied lead adsorption with chitosan/polyvinyl alcohol (PVA) hydrogel beads and found that the blending of PVA in chitosan improved the mechanical strength of the hydrogel beads.