Practical Polysaccharides (Part 10 - Last): Chitin-Heparin Bico in Wound Care

Part 10 of the paper by Jacek K. Dutkiewicz of Buckeye Technologies Inc given at this years Insight Conference organised by MTS in Norfolk Virginia. (Click here for Part 1)

Chitin and its simple derivative chitosan are highly crystalline which makes them suitable for making high-tenacity structural materials such as fibers and films.   An interesting discovery was made some time ago [10] and remained practically unknown. It resulted from experimentation with solutions of chitosan and heparin, two oppositely charged polymers.   It was observed that at the interface of these two solutions it was possible to form a liquid film which had fiber forming characteristics (Fig. 17).  Thus prepared filaments were composed with a chitosan core and heparin sheath.  The purpose of that study was to combine bacteriostatic and wound-healing properties of chitosan with blood anticoagulant characteristics of heparin.  Potential medical applications of such materials involved for instance vascular grafts.

Another less known property of chitosan and, in particular, some of its salts involves ostensibly self-contradictory interactions with blood.  Chitosan has good hemostatic properties and this is one of the

Practical Polysaccharides (Part 9) - Chitin for Superabsorbents

Part 9 of the paper by Jacek K. Dutkiewicz of Buckeye Technologies Inc given at this years Insight Conference organised by MTS in Norfolk Virginia. (Click here for Part 1)

Last but not least, chitin is a fascinating polysaccharide for a number of reasons.  First, it is the second most abundant polycarbohydrate used by Mother Nature as a structural component both in the animal and in the plant kingdoms. Second, chitin has a chemical structure which is similar to that of cellulose except for a different functional group on the carbon atom number 2.  Finally, from a practical point of view, chitin has been shown to have interesting useful properties. For instance, chitin exhibits biological activity (e.g. wound-healing, bacteriostatic effect) which makes it very attractive for medical applications.
Chitin can be easily converted into various physical and chemical forms when it is first partially deacetylated to chitosan.  Chitosan’s structural uniqueness relies upon ionizable amino groups which make the polymer soluble in dilute acids. Without further derivatization one can then cross-link the deacetylated chitin and obtain a polycationic superabsorbent material which has very high absorbent capacity (Fig. 15).

Practical Polysaccharides (Part 8) Starch-based Nonwovens and Superabsorbents

Part 8 of the paper by Jacek K. Dutkiewicz of Buckeye Technologies Inc given at this years Insight Conference organised by MTS in Norfolk Virginia. (Click here for Part 1)

From the cost point of view, starch may seem even more attractive as a raw material compared to cellulose for a superabsorbent polymer because of its high-molecular weight and abundance of reactive hydroxyl groups.  Indeed, relatively high-capacity products have been commercialized and there were even some attempts to use them for personal care applications.  So far the performance of synthetic SAP is far more superior and it may be hard to replace it in the disposable hygiene area with a starch-based polymer.  Still it is worth mentioning at least one simple technical solution which involved an approach similar to the one referenced above with regard to cellulose [8]. In this case, carboxymethylstarch was cross-linked also by heat treatment to achieve a decent, but not permanent absorbency capacity (Fig.13).  One can speculate that, over a period of time, polysaccharides may undergo morphological changes due to relaxation and reorientation of polymeric chains, which affect the physical crosslink density in the material.   Therefore, the absorbency properties may gradually decline.

Practical Polysaccharides (Part 7) Converting cellulose into superabsorbents?

Part 7 of the paper by Jacek K. Dutkiewicz of Buckeye Technologies Inc given at this years Insight Conference organised by MTS in Norfolk Virginia. (Click here for Part 1)

There have been many attempts to match the performance and cost of the CMC SAP to those of the synthetic sodium polyacrylate SAP.  On both fronts, however,  these efforts have not been successful enough to make the concept commercially viable for personal hygiene applications.

For instance, one of more interesting approaches was to create cross-links within the CMC polymer simply by using heat [8].  The resultant material had high absorbent capacity (Fig. 12). However,  over time the superabsorbent properties of such a polymer tend to decline gradually.   

There were also attempts to enhance the capacity of cellulose-based SAP by creating micro-porous sponge-like structures by applying organic solvent/water exchange techniques.  For low-cost applications such solutions do not seem to be viable because of their complexity and relatively high cost.   So, the concept of replacing synthetic SAP with a cellulose-based equivalent still may wait some time for a satisfactory practical and inexpensive solution.

(Go to Part 8)

Practical Polysaccharides (Part 6) Collaboration between modified fibres and SAP

Part 6 of the paper by Jacek K. Dutkiewicz of Buckeye Technologies Inc given at this years Insight Conference organised by MTS in Norfolk Virginia. (Click here for Part 1)

One of these solutions utilizes cellulose fluff carrying polyvalent cations such as Al3+ [6].  These ions are subsequently released to the entering liquid and can precipitate the soluble sodium polyacrylate fraction which diffuses from the SAP particles. The polyvalent cations can also react with the surface of the superabsorbent granules creating in situ a “skin” on them, which protects the soluble oligomers from leaching out to the system.  This concept is illustrated in Fig. 9.  As a result of the collaborative interaction between the modified fibers and the SAP, the permeability of the system is improved as is the efficiency of the fiber matrix liquid distribution capability.

Here is another example of a system in which cellulosic fibers can help enhance

Practical Polysaccharides (Part 5) A solution to the ammonia odour problem in personal absorbents

Part 5 of the paper by Jacek K. Dutkiewicz of Buckeye Technologies Inc given at this years Insight Conference organised by MTS in Norfolk Virginia. (Click here for Part 1)

An example of using cellulose fibers both for this purpose and simultaneously, for absorbency was presented a few years ago at the Insight Conference [5].   The concept of storing a urease inhibitor in absorbent fluff proved to be very effective for eliminating ammonia odor which normally occurs due to enzymatic hydrolysis of urea.   This solution to the odor problem is shown in Fig. 8. 


 Inhibition of microbial ammonia production had an additional benefit for skin wellness, which is maintaining the pH at a level slightly below neutral.

Practical Polysaccharides (Part 4) Cellulose fibres to store functional agents

Part 4 of the paper by Jacek K. Dutkiewicz of Buckeye Technologies Inc given at this years Insight Conference organised by MTS in Norfolk Virginia. (Click here for Part 1)
The coarseness and length of natural wood or cotton-linter cellulosic fibers may vary depending on the origin, geography and age of the plant.  There are tools known by cellulose pulp experts to control or modify fiber geometry but only to a limited extent since the basic parameters have been already defined by Mother Nature.   Cellulosic fiber webs possess excellent absorbent properties, in large part because of their high surface energy.  Water-based liquids, depending on their liquid rate constant W [4], can move more quickly within the pores of cellulose fiber networks than in other kinds of porous materials.  The liquid rate constant is defined here as a ratio of surface tension to viscosity of a given liquid.   The units of W are the same as the physical units of velocity.   This parameter can be used in mathematical descriptions of the rate of fluid flow for instance in the Laplace and Lucas-Washburn equations (Fig.6).

Cellulosic fibers have unique properties such as surface polarity and reactive

Practical Polysaccharides - Part 2 - Cellulose

Part 2 of the paper by Jacek K. Dutkiewicz of Buckeye Technologies Inc given at this years Insight Conference organised by MTS in Norfolk Virginia. (Click here for  Part 1)

Cellulose is the main component of biomass whose total annual production is estimated at more than 100 billion metric tons based on its carbon content [2].  Most of this carbon is stored in woodlands and is produced by the plants through photosynthesis using atmospheric carbon dioxide. The global balance of so-called biomass carbon cycle is not certain and the plants producing cellulose are our allies in controlling the greenhouse gas effect.  According to the results available from the U.S. Forest Service [3] within the United States the growth of woodlands measured as the volume of trees historically has had a positive trend. It is suggested that this trend should have a favorable impact on the biomass carbon balance in North America (Fig. 2)

Fig. 2. Biomass carbon balance.

Practical Polysaccharides: Some Less Known Stories of Cellulose, Starch and Chitin

This paper by Jacek K. Dutkiewicz of Buckeye Technologies Inc was given at this years Insight Conference organised by MTS in Norfolk Virginia.  We thought it was good enough to appear here in several instalments so here's the first part. (The nonwovens from thermoplastic starch look particularly interesting.)

Polysaccharides are everywhere and all around us. They are in plants, animals, LCD screens, tires, medicines, cosmetics, paints, nonwovens, and binders. We use them as food, tools, furniture, paper, home, cloth … and so on and on.

Cellulose is the most abundant natural polymer followed by chitin. Starch belongs to the group of most common polycarbohydrates and its importance is mainly due to the fact that it is digestible by humans and stores energy. 

Combined together, polysaccharides represent the largest group of polymers harvested and produced in the world [1]. It is because they are renewable and extremely useful in countless areas of applications whose number is steadily growing. Cellulose, chitin and starch are liked by scientists and researchers due to their chemical and physical properties and by product developers due to their availability and affordability depending on the grade and on specific target applications. Starch is the cheapest of all three, cellulose is much more expensive and chitin, especially its preferred derivative chitosan, in order of magnitude is more costly than starch.

What can these natural polymers offer as raw materials? Fig. 1 illustrates