Newsflash

The drive for lightweight materials to reduce overall cost and environmental impact for automotive manufacturers is nothing new.  Fuel economy attracts car buyers too. That is how majority of steel parts have been replaced in F-150 pickup truck by aluminum parts, reducing overall weight over 500 pounds. Then there are alloys, carbon fiber and plastics composites.The ambition for lighter vehicles did not stop with alloys (magnesium, aluminum), and/or composites (glass, carbon fibers).  Recently, Japanese researchers at Kyoto University led by Professor Hiroaki Yano along with its industrial partners (Denso Corporation and Daikyo-Nishikawa Corporation) reported that they were developing cellulose nanofiber based materials for automotive as well as aircraft parts to reduce environmental footprint while increasing product performance.Inevitable questions are: 1) would these materials be cost effective? 2) What would be the service life of these products compared to the current ones? 3) How about the parts’ safety in situations like crash or fire?A final question that an automaker has to ask is: what would be the pay back time to replace current production line (machinery) to CNF based plastics line?Reference: https://www.japantimes.co.jp/news/2017/08/15/business/researchers-japan-use-wood-make-cellulose-nanofiber-auto-parts-stronger-lighter-metal/#.WbAIKeTXuUm...
We know polycarbonates mostly from its use in plastics water bottles, safety goggles, smart phones, structural panels (glazing) and the list goes on.  A quick look at Wikipedia gives a spectrum of applications.However, polycarbonates have its weaknesses along with the BPA (bis-phenol) controversy. Polymers such as polysulfates and polysulfonates have similar if not better mechanical properties than polycarbonates.  The issue has been how reliably scale-up the manufacturing process of polysulfates and polysulfonates?“Click chemistry” is a concept in organic chemistry by which highly reactive reactions provide high yielding products and require little to no purification.  The concept was introduced by Nobel Prize winner Professor K. Barry Sharpless in 2001.A recent work published in Nature Chemistry, by a team of researchers from The Scripps Research Institute (La Jolla), Lawrence Berkley National Laboratory (Berkley), California and Shanghai Institute of Organic Chemistry & Soochow University, China claimed that reduced cost of catalyst, product purity, and by-product recycling make their work ready to move from laboratory research to industrial process.Chemists are at work indeed!References:https://en.wikipedia.org/wiki/PolycarbonateK. Barry Sharpless et al; Nature Chemistry, 2017 DOI: 10.1038/nchem.2796...
In a recent The Atlantic interview Bill Gates made a wish on an energy miracle, “Here’s a source of energy that is cheaper than your coal plants, and by the way, from a global-pollution and local-pollution point of view, it’s also better”.  The race is on to find that source. One such energy source is solar energy. We all know that solar energy can be harnessed to generate thermal energy or electrical energy for use in the residential and/or in the commercial applications.  Any material that can store Solar Thermal Energy is called Solar Thermal Fuel (STF).  The quest to harvest solar energy, store the same and use it when needed has been the focus of research in industry and academia alike. For the first time, Professor Grossman’s team at MIT, Cambridge (USA) has come up with a new approach which uses polymer Solar Thermal Fuel (STF) storage platform utilizing STF in its solid-state.  According to the published article, researchers stated, “Closed cycle systems offer an opportunity for solar energy harvesting and storage all within the same material. This approach enables uniform films capable of appreciable heat storage of up to 30 Wh kg?1 and that can withstand temperature of up to 180 °C.”How the STF process works?Certain molecules (chemicals) can have 2 different stable structural forms. These structures are called conformations.  When original molecular conformation is exposed to sunlight, the molecule gets charged and the original conformation changes to the other and stay in that charged conformation for a long period.  The charged molecule snaps back to their original shape (conformation), when triggered by a very specific temperature or other stimulus generating heat in the process. Currently, developed polymeric film can release heat about 10 degree C above the surrounding temperature. Film property improvements are underway. German auto company BMW, has sponsored this research. Where the potential application lies - your guess is as good as mine.References:The Atlantic, p 56, November 2015Zhitomirsky, D., Cho, E. and Grossman, J. C. (2015), Solid-State Solar Thermal Fuels for Heat Release Applications. Adv. Energy Mater., 1502006. doi:10.1002/aenm.201502006...
In a recent The Atlantic interview Bill Gates made a wish on an energy miracle, “Here’s a source of energy that is cheaper than your coal plants, and by the way, from a global-pollution and local-pollution point of view, it’s also better”.  The race is on to find that source. One such energy source is solar energy. We all know that solar energy can be harnessed to generate thermal energy or electrical energy for use in the residential and/or in the commercial applications.  Any material that can store Solar Thermal Energy is called Solar Thermal Fuel (STF).  The quest to harvest solar energy, store the same and use it when needed has been the focus of research in industry and academia alike. For the first time, Professor Grossman’s team at MIT, Cambridge (USA) has come up with a new approach which uses polymer Solar Thermal Fuel (STF) storage platform utilizing STF in its solid-state.  According to the published article, researchers stated, “Closed cycle systems offer an opportunity for solar energy harvesting and storage all within the same material. This approach enables uniform films capable of appreciable heat storage of up to 30 Wh kg?1 and that can withstand temperature of up to 180 °C.”How the STF process works?Certain molecules (chemicals) can have 2 different stable structural forms. These structures are called conformations.  When original molecular conformation is exposed to sunlight, the molecule gets charged and the original conformation changes to the other and stay in that charged conformation for a long period.  The charged molecule snaps back to their original shape (conformation), when triggered by a very specific temperature or other stimulus generating heat in the process. Currently, developed polymeric film can release heat about 10 degree C above the surrounding temperature. Film property improvements are underway. German auto company BMW, has sponsored this research. Where the potential application lies - your guess is as good as mine.References:The Atlantic, p 56, November 2015Zhitomirsky, D., Cho, E. and Grossman, J. C. (2015), Solid-State Solar Thermal Fuels for Heat Release Applications. Adv. Energy Mater., 1502006. doi:10.1002/aenm.201502006...
Reliable and high performance lithium ion batteries commonly known as LIBS are highly sought after product by industries. We all have heard stories about laptops, electric vehicles, airplanes catching fires due to LIBS. Underlying problem is the battery overheating. Preventing batteries from overheating is crucial to the public safety.  Now a team of researchers at Stanford University designed a thermo-responsive (heat sensitive) plastic composite film made from polyethylene and spiky nickel microparticles coated with graphene which shuts down the battery if the temperature is too high.         In a recently published work led by Yi Cui and Zhenan Bao of Stanford University, USA concluded “Safe batteries with this thermoresponsive polymer switching (TRPS) materials show excellent battery performance at normal temperature and shut down rapidly under abnormal conditions, such as overheating and shorting.” How practical this design approach is? Time will tell.References: Y. Cui, Z. Bao et al Nature Energy vol.1, Article number: 15009 (2016); DOI: 10.1038/nenergy.2015.9Chemical & Engineering News, Page 7, January 18, 2016...
In aviation industry, the focus is how to improve fuel safety and handling. Mike Jaffe and Sahitya Allam gave their perspective on safer fuels by integrating polymer theory into design (Science, 350, No. 6256, p. 32, 2015).Mist (generated from the fuel) is much more flammable than the liquid and that is why anti-misting kerosene interferes with mist formation when a low percentage of a polymer is added into it.  The problem however, is that the polymer chain undergoes scission during handling and can’t assist in suppressing mist formation. The answer comes from a recent paper published in the Journal Science by Professor Julia Kornfield and her cross-functional team at Caltech, Pasadena, USA. The group designed a megasupramolecules having polycyclooctadiene backbones and acid or amine end groups (telechelic polymer) which is short enough to resist hydrodynamic chain scission while protecting covalent bonds through reversible linkages. Yes, polymers can be designed to suit our societal needs including aviation fuel safety.Reference: M-H Wei, B. Li, R.L. Ameri David, S.C. Jones, V. Sarohia, J.A. Schmitigal and J.A. Kornfield; Science, 350, (6256), pp. 72-75 (2015)...
At the TED conference, Carbon3D, a Vancouver based company touted a radical 3D printing technology and named it CLIP or Continuous Liquid Interface Product. CLIP grows parts instead of printing them layer by layer. It harnesses light and oxygen to continuously grow objects from a pool of resin.  The result: make commercial quality parts at game-changing speed.  CLIP is 25 to 100 times faster than traditional 3D printing technique.  To make the point, Carbon3D web site provides a head-to-head comparison of CLIP to Polyjet, SLS and SLA.[Press release: March 16, 2015, Vancouver, Canada.  www.carbon3D.com]...
Self-healing plastics has been around for a while. Applications include self-healing medical implants, self-repairing materials for use in airplanes and spacecrafts. Even scientists have made polymeric materials that can repair itself multiple times. A recent report in Science describes a significant advance in self-healing plastics. The authors describe a product that mimics how blood can clot to heal a wound. When the plastic is damaged a pair of pre-polymers in channels combines and rapidly forms a gel, which then hardens over 3 hours.The authors demonstrated that holes up to 8 millimeters wide can be repaired. The repaired parts can absorb 62% of the total energy absorbed by undamaged parts.  Science never stops.Reference:S. R. White, J. S. Moore, N. R. Sottos, B. P. Krull, W. A. Santa Cruz, R. C. R. Gergely; Science, Restoration of Large Damage Volumes in Polymers, Vol. 344 no. 6184 pp. 620-623; (9 May 2014). ...
Knowingly or unknowingly, flexible electronics has become a part of our daily life.  Transparent conductive films (TCFs) are used in mobile phones, tablets, laptops and displays.  Currently, Indium Tin Oxide or commonly known as ITO is the material of choice.  But use of ITO has some major disadvantages and these are brittleness, higher conductivity at greater transparency, and supply of Indium.  This is where non-ITO materials come into play. Based in St. Paul, Minnesota (USA), Cima NaoTech’s uses its SANTETM nanoparticle technology, a silver nanoparticle conductive coating which self-assembles into a random mesh like network when coated onto a flexible substrate such as PET and PC.  According to a recent press release, the company stated SANTETM nanoparticle technology enabled transparent conductors in a multitude markets from large format multi-touch displays to capacitive sensors, transparent and mouldable EMI shielding, transparent heaters, antennas, OLED lighting, electrochromic and other flexible applications.  Cima NanoTech is working with Silicon Integrated Systems Corp. (SIS) of Taiwan and using its highly conductive SANTE FS200TM touch films to develop large format touch screens.References: Press release, San Diego, June 03, 2014; www.cimananotech.com ; http://www.cimananotech.com/sante-technology ; http://www.sis.com/...
In an article appeared today (January 29, 2014) in The Guardian newspaper, Stuart Dredge wrote, “From jet parts to unborn babies, icebergs to crime scenes, dolls to houses: how new technology is shaking up making things”1. Mr. Dredge was speaking about 3D printing technology.  The heart of this technology is the 3D printer itself. Stratasys, a company headquartered in Minneapolis, USA is the manufacturer of 3D printers.  It recently announced the launch of Color Multi-material 3D Printer, the first and only 3D printer to combine colors with multi-material 3D printing.  According to the press release2, by using cyan, magenta, and yellow, multi-material objects can be printed in hundreds of colors.  The technology is based on proven Connex technology.  While the base materials are plastics and elastomers, they can be combined and treated to make finished products of wide ranging flexibility and rigidity, transparency and opacity.  Designers, engineers and manufacturers can create models, mold, and parts that match the characteristics of the finished production part. This includes achieving excellent mechanical properties.  According to the manufacturer, print job in the newly revealed printer can run with about 30 kg of resin per cycle and prints as fine as 16 micron layers for models.  No wonder why some call the new Color Multi-material 3D printer a groundbreaking stuff.References: 1. www.theguardian.com.technology/2014/jan/29/3d-printing-limbs-cars-selfies (January 29, 2014)2. http://investors.stratasys.com/releasedetail.cfm?ReleaseID=821134 (August 3, 2014)...
Instead of stitches or skin staples, doctors use skin glue to close wounds. The glue joinsthe edges of a wound together while the wounds heal underneath. Most of the timeskin glue is used for simple cuts or wounds. According to the paper published inScience Translational Medicine, there are no clinically approved surgical glues thatare non-toxic, bind strongly to tissue, and work well in wet and highly dynamicenvironments within the body. This is the reason why this published work is promisingwhere infants born with heart defects would benefit tremendously. Researchers at the Brigham and Women’s hospital in Boston have engineered ‘bio-inspired’ gluethat can bind strongly to tissues on demand, and work well in the presence ofactively contracting tissues and blood flow. The authors of the paper show howthe glue can effectively be used to repair defects of the heart and blood vessels during minimally invasive procedures. [References: P. J. del Nido et al; Sci. Transl. Med., DOI: 10.1126/scitranslmed.3006557; See also, www.geckobiomedical.com/news/gecko-biomedicals-co-founde.html]...
Stability of organic electronics in water is a major research challenge. For this reason,organic electronics has yet to see any sensing application in aqueous environment.However, as understanding of underlying mechanism of stability aspect is becomingclearer, new developmental efforts to make water compatible organic polymer devicesare taking place. Recently, Professor Zhenan Bao’s group in the department of chemical engineering at Stanforduniversity revealed in a paper published in the journal of Nature Communications thatsolution- processable organic polymer could be stable under both in freshwater andin seawater. Developed organic field-effect transistor sensor is able to detect mercury ionsin the marine environment (high salt environment). Researchers believe that the work hasthe potential to develop inexpensive, ink-jet printed, and large-scale environmental monitoring devices. [References: O. Knopfmacher, M.L. Hammock, A.L. Appleton, G. Schwartz, J. Mei, T. Lei, J. Pei,and Z. Bao; Nature Communications, 5, 2954, January 6, 2014; DOI: 10.1038/ncomms3954]...
Insulin, the wonder medicine for diabetes was discovered about a century ago.Since insulin does not get into the blood stream easily, diabetes patients oftenhave injected themselves with insulin. Now a group of scientists led by Dr. Sanyog Jainat the Center for Pharmaceutical Nanotechnology of National Institute of Pharmaceutical Education and Research in Punjab, India has designed a polymerbased package for oral insulin administration. The package design addresses two major obstacles, 1) digestive enzymes must notdegrade insulin prior to its action and 2) the insulin gets into the blood stream.The package contained folic acid functionalized insulin loaded in liposomes.To protect the liposomes (lipids or fat molecules) they were alternately coated withnegatively charged polyacrylic acid (PAA), and positively charged poly allylamine hydrochloride. Studies were conducted to compare the efficacy of bothdelivery systems: designed polyelectrolyte based insulin and standard insulinsolution. Effects of oral administration lasted longer than that of injectedinsulin, authors reported in a recent article in Biomacromolecules. [Reference: A.K. Agarwal, H. Harde, K. Thanki, and S. Jain; Biomacrmolecules, Nov. 27, 2013;DOI: 10.1021/bm401580k]...
Research in the area of stretchable electronics is heating up!  Thanks to polymers. Led by Professor George M. Whitesides of Harvard University (USA), a team of researchers have demonstrated in a recently published paper in Science that ionic conductors can be used in devices requiring voltages and frequencies much higher than commonly associated with devices using ionic conductors.  The team showed for the first time that electrical charges carried by ions and not electrons, can be utilized in fast-moving, high voltage devices.As a proof of concept, the authors of the study built a transparent loudspeaker that produces sound across the full audible range i.e., 20 Hz to 20 kHz.  Components [such as VHB 4910 tape (acrylic tape with PE liner), polyacrylamide hydrogel containing NaCl electrolyte] used for the high speed, transparent actuators are described in the paper.Tissues and cells are soft and require stretchable conductors for biological systems. Many hydrogels are biocompatible which makes this work particularly an important one. The design of gel-based ionic conductors is highly stretchable, completely transparent and offer new opportunities for designers of soft machines.   [Reference: C.Keplinger, J-Y. Sun, C.C. Foo, P. Rothemund, G.M. Whitesides, and Z. Suo; Science, 341 (6149), pp. 984-987 (2013); DOI: 10.1126/science.1240228]...
Interweaving biological tissue with functional electronics, one can make bionic ears.  NASA has tested 3D-printed rocket engine part.  Then why not 3D print yourself?Well, Twinkind, a German start-up company is now offering enthusiasts statues of themselves for display.  How this works?  A full body scanner takes an image of the customer’s body, transfers the file to the printer after which 3D printer laser sinters a composite powder layer by layer into the customer image.Can we dare to say that Madame Tussauds wax figure of Voltaire can now be 3D printed in polymers soon!  [Reference: www.twinkind.com ]...
Polymer membranes have become a leading contender in numerous separation processes.  Be it in gas (air, hydrogen etc.) or be it in water purifications (salinated water, waste water etc.).  Not only polymer membrane technology helps reducing the environmental impact but also it is cost-effective.  Fracking in shell gas is one of many examples. New advances in drilling technology (such as horizontal drilling) have led to new hydraulic fractures called fracking.  Hydraulic fracturing requires about 2.5 to 5 million gallons of water per well.  Water management and its disposal are major costs for producers.One major challenge, however, of the membrane technology is the fouling (damage caused by contaminants) mitigation.  This has been recently studied by a group of researchers from University of Texas at Austin led by Professor Benny Freeman to address efficiency and reuse of water for fracking in shale gas plays.Researchers modified polydopamine coated UF (ultrafiltration) module by grafting polyethylene glycol brushes onto it.  The result is more hydrophilic surfaces which in turn improved cleaning efficiency relative to unmodified modules. The coating improves the membrane life, and can easily be applied to membrane surface by rinsing it through the recycling system.[References: D.J. Miller, X. Huang, H. Li, S. Kasemset, A. Lee, D. Agnihotri, T. Hayes, D.R. Paul, and B. Freeman; J. Membrane Sci., 437, pp. 265-275 (2013); Also see www.advancedhydro.net ]...
Flexible electronics can change the way we use electronic devices.  It is a term used for assembling electronic circuits by mounting electronic devices on a flexible plastic. A recent review article captured the advancement of CNT and graphene based flexible thin film transistors from material preparation, device fabrication to transistor performance control compared to traditional rigid silicon1. Silicon is used almost exclusively in electronic devices.Now Prof. Ali Javey led a team at the University of California, Berkley to develop a printing process to make nanotube transistors at room temperature with gravure printer.  The plastics used is polyethylene terephthalate (PET). The device exhibited excellent performance with mobility and on/off current ratio of up to ~9 cm2/ (V s) and 105 respectively.  Also, maximum bendability is observed.  The paper authors conclude that this high-throughput printing process serves as enabling nanomanufacturing scheme for range of large-area electronic applications based on nanotube networks2. References:1. D-M. Sun, C. Liu, W-C. Ren and H-M Cheng; Small, DOI: 10.1002/smll.2012031542. P.H. Lau, K. Takei, C. Wang, Y. Zu, J. Kim, Z. Yu, T. Takahashi, G. Cho, and Ali Javey; Nano Letters, 13 (8), pp. 3864-3869 (2013); DOI. 10.1021/nl401934a...
Drinking coffee from paper cups are as common as drinking water from plastics bottle. The issue however, is recycling of disposable cups. The disposable cups are made up of 90-95% of high strength paper (fibers) with a 5% thin coating of plastic (PE).To address the recycling issue, James Cropper Speciality Papers of UK have developed a process which involves softening the cup waste, and separating the plastic coating from the fiber.  After skimming off the plastic, remains are pulverised and recycled, leaving water and pulp behind.  According to the company news release, the high grade pulp is reused in luxury papers and packaging materials.An innovative approach to address a common problem.[Reference: www.jamescropper.com/news ]...
A search for an alternative to rigid silicon wafers gave birth to the area of flexible or bendable electronics. Research has been intense for the past few years in the area flexible electronics as it opens up multitude of new applications. Polymers play an important role to exciting field of flexible electronics.In a recent research report, a team of scientist led by Prof. Ali Javey of University of California, Berkeley (USA)  has shown for the first time user-interactive electronic skin or e-skin can conformally wrap irregular surfaces and spatially map and quantify various stimuli through a built-in active matrix OLED display.  Three electronic components namely thin film transistor (uniform carbon nanotube based), pressure sensor, and OLED arrays (red, green, and blue) are integrated over a plastic substrate.  Spin coated and cured polyimide on a silicon wafer is used as the flexible substrate.  Details are in the paper.This work essentially provides a technology platform where integration of several components (organic and inorganic) can be done at a system level on plastic substrates. According to the paper, this e-skin technology could find applications in interactive input/control devices, smart wallpapers, robotics, and medical/health monitoring devices.    [Ref: C. Wang, D. Hwang, Z. Yu, K. Takei, J. Park, T. Chen, B. Ma, and Ali Javey; Nature Materials, Published online July 21, 2013; DOI: 10.1038/NMAT3711]...
Recent buzz in the technology world is 3D printing.  Researchers to designers are creating new products everyday using 3D printing technology.  Even eBay has unveiled its services to those looking to make their own creations using 3D printing App.Since ages composites have played a crucial role in our society. Inspired by natural (biological) composites such as bone or nacreous abalone shell, researchers from MIT (USA) and Stratasys have developed composite materials that have fracture behaviour similar to bones.  Using computer model with soft and stiff polymers, the team has come up with a specific topological arrangements (hierarchical structures) of polymer phases to boost the mechanical behaviour in the composites.Interestingly, the team has been able to manufacture (thanks to 3D printing) a composite material that is more than 20 times larger than its strongest constituent.  The referenced paper showed that one can use computer model to design composite materials of their choice, tailor the fracture pattern and then use 3D printing technology to manufacture the composites.[Ref: L.S. Dimas, G.H. Bratzel, I. Eylon, and M.J. Buehler; Advanced Functional Materials, Published online June 17, 2013; DOI: 10.1002/adfm.201300215]...
ImageOnce words such as chitin and chitosan are in your mental radar screen, you will find them everywhere. Possibly, you had a lobster supper last night and you removed that hard outer shell as a useless stuff. In fact, you discarded the hard shell that consisted millions of tightly interwoven polymer strands called chitin. The hard outer shell, or exoskeleton, are known to give protection to shrimps, crabs, lobsters, scorpions, insects etc. from their predators.Chitin is one of the most abundant polysaccharide in nature1, being only second after cellulose. It can be found in animals (exoskeletons of crustacean and insects) as well as in fungi, mushrooms and yeasts2.

A brief background of chitin

The basic principles of the chitin isolation are known since the beginning of 19th century. It was, Professor Henri Braconnot, Director of the Botanical Garden in Nancy, France first isolated a fraction called fungine in 1811 from the cell walls of mushrooms. In 1823 Odier renamed fungine as chitin (meaning tunic in Greek) almost 3 decades before the isolation of cellulose. Chitin is mostly obtained from the exoskeleton of industrially processed crustaceans, such as lobster, crab and shrimp which contains between 20 to 40% of chitin3. The increased use of chitin (and its derivates) is motivated by the fact that contrary to the petroleum derivatives, chitin is obtained from fisheries by-products, naturally renewable source, non-toxic, non-allergenic, anti-microbial and biodegradable.



Chemistry of chitin

Chitin is a polysaccharide. A polysaccharide is a polymer - a giant molecule consisting of smaller molecules of sugar strung together. Chitin can be described as a biopolymer composed of N-acetyl-D-glucosamine; a chemical structure very close to cellulose except that the hydroxyl group in C (2) of cellulose being replaced by an acetamido group in chitin. One can associate this chemical similarity between cellulose and chitin as serving similar structural and defensive functions2.

 

How to extract chitin from the crustacean (hard) shells?

While there exists many extraction methods of the chitin from the crustacean shells, the principles of chitin extraction are relatively simple. The proteins are removed by a treatment in a dilute solution of sodium hydroxide (1-10%) at high temperature (85-100°C). Shells are then demineralized to remove calcium carbonate. This is done by treating in a dilute solution of hydrochloric acid (1-10%) at room temperature. Depending on the severity of these treatments such as temperature, duration, concentration of the chemicals, concentration and size of the crushed shells, the physico-chemical characteristics of the extracted chitin will vary. For instance, the three most important characteristics of the chitin i.e., degree of polymerization, acetylation and purity, will be affected. Shell also contains lipids and pigments. Therefore, a decolorizing step is sometimes needed to obtain a white chitin. This is done by soaking in organic solvents or in a very dilute solution of sodium hypochlorite. Again, these treatments will influence the characteristics of the chitin molecule.



Chitosan - another important derivative of chitin

Chemists love to play with molecules. They did not spare chitin, the polymer either and made chitosan. The term chitosan is used when chitin could be dissolved in weak acid. When chitin is heated in a strong solution of sodium hydroxide (>40%) at high temperature (90-120°C), chitosan is formed. This harsh treatment removes acetylic grouping on the amine radicals to a product (chitosan) that could be dissolved. It is said that at least 65% of the acetylic groups should be removed on each monomeric chitin to obtain the ability of being put in solution2. The degree of deacetylation will vary according to the duration, the temperature and the concentration of the sodium hydroxide. Furthermore, many chemical characteristics of the chitosan (molecular weight, its polydispersity, the purity) are greatly dependant on the method, the equipment used and also of the source of the shells. It is therefore, crucial to control precisely methods of production of the chitosan to obtain the exact characteristics needed for end use application of the product.

 

Making chitosan into a value-added ingredient - how?

Three main characteristics of chitosan to be considered are: molecular weight, degree of deacetylation and purity. Since chitosan is a polymer formed by repeating units of D-glucosamine (sugar), the total length of the molecule is an important characteristic of the molecule. As a result, the molecular weight is a key feature for a particular application of chitosan. The molecular weight of the native chitin has been reported to be as high as many million Daltons. However, the harsh chemical treatment tends to bring down the molecular weight of the chitosan, ranging from 100 KDa to 1500 KDa. An inert environment during the deacetylation could preserve the molecular chain. On the other hand, low molecular weight could be produced by different ways including enzymatic or chemical methods. When the chain becomes short to shorter, chitosan could be dissolved directly in water without the need of an acid. This is particularly useful for specific application in cosmetic or in medicine when the pH should stay around 7.0. Molecular weight of chitosan could be measured by gel permeation chromatography, light scattering, or viscometry. Because of simplicity, viscometry is the most commonly used methods even though it is influenced by many factors (concentration temperature, ionic strength, pH, type of acids) other than the molecular weight.
Since chitosan is made by deacetylation of chitin, the term degree of deacetylation (DAC) is used to characterize chitosan. This value gives the proportion of monomeric units of which the acetylic groups that have been removed, indicating the proportion of free amino groups (reactive after dissolution in weak acid) on the polymer. DAC could vary from 70 to 100%, depending of the manufacturing method used. This parameter is important since it indicates the cationic charge of the molecule after dissolution in a weak acid. There are many methods of DAC measurements like UV and infrared spectroscopy, acid-base titration, nuclear magnetic resonance, dye absorption, etc.. Since there are no official standard methods, numbers tend to be different for different methods. In high value product, NMR gives the most precise DAC number. Given its high cost, many producer uses titration or dye adsorption as a quick and convenient method, that yields similar results as NMR.
Finally, the purity of the product is vital particularly for high-value product (biomedical or cosmetic area). This purity is quantified as the remaining ashes, proteins, insolubles, and also in the bio-burden (microbes, yeasts and moulds, endotoxins). Even in the lower value chitosan such as that used for the wastewaters treatment, the purity is a factor because the remaining ashes or proteins tend to block active sites, the amine grouping. Being not available to bind, a greater amount of chitosan is needed to be effective.

 

Here comes the multitude of applications …

Chitosan is a biological product with cationic (positive electrical charge) properties. It is of great interest, all the more so because most polysaccharides of the same types are neutral or negatively charged. By controlling the molecular weight, the degree of deacetylation and purity, it is possible to produce a broad range of chitosans and derivatives that can be used for industrial, dietary, cosmetic and biomedical purposes. Together these properties have led to the development of hundreds of applications so far. There are plethora of literature, books and conference proceedings that documented the multiple uses of the chitosan4. It is out of the scope of this article to describe extensively every applications of chitosan. We will concentrate on the major uses of chitosan and the most promising future applications. Applications of chitosan can be classified mainly in 3 categories according to the requirement on the purity of the chitosan:



  • Technical grade for agriculture and water treatment
  • Pure grade for the food and cosmetics industries
  • Ultra-pure grade for biopharmaceutical uses

In agriculture:

Chitosan offers a natural alternative to the use of chemical products that are sometimes harmful to humans and their environment. Chitosan triggers the defensive mechanisms in plants (acting much like a vaccine in humans), stimulates growth and induces certain enzymes (synthesis of phytoalexins, chitinases, pectinases, glucanases, and lignin). This new organic control approach offers promise as a biocontrol tool. In addition to the growth-stimulation properties and fungi, chitosans are used for:

 

  • Seed-coating
  • Frost protection
  • Bloom and fruit-setting stimulation
  • Timed release of product into the soil (fertilizers, organic control agents, nutrients)
  • Protective coating for fruits and vegetables

For water treatment:

At the present time, physicochemical-type treatment is widely used at potable and wastewater treatment plants. The major disadvantage of using synthetic chemical products is the risk of resulting environmental pollution. Treating wastewater using "greener" methods has become an ecological necessity. Chitosan, due to its natural origin and being biodegradable, has proven to be a most interesting alternative from several points of view.
Integrating a natural polymer made of crustacean residue into an existing system achieves a two-fold purpose: it improves the effectiveness of water treatment while reducing or even eliminating synthetic chemical products such as aluminum sulphate and synthetic polymers. Here are a few characteristics of chitosan that offer an ecological solution:

 

  • Natural and biodegradable
  • A powerful competitor for synthetic chemical products
  • Potentially reduces the use of alum by up to 60% and eliminates 100% of the polymers from the treated water
  • Improves system performance (suspended solids and chemical oxygen demand)
  • Significantly reduces odor

 

In food:

Chitosan is already used as a food ingredient in Japan, in Europe and in the United States as a lipid trap, an important dietetic breakthrough. Since chitosan is not digested by the human body, it acts as a fiber, a crucial diet component. It has the unique property of being able to bind lipids arriving in the intestine, thereby reducing by 20 to 30% the amount of cholesterol absorbed by the human body. This raises the question: is chitosan really a "Fat Magnet"?
In solutions, chitosan has thickening and stabilizing properties, both essential to the preparation of sauces and other culinary dishes that hold their consistency well. Finally, as a flocculating agent, it is used to clarify beverages. Because of its phytosanitary properties, it can be sprayed in dilute form on foods such as fruits and vegetables, creating a protective, antibacterial, fungi static film. In Japan, a dilute solution of chitosan is commonly sprayed on apples and oranges as a protective measure. There are many other applications in the areas of nutraceutical and nutritional supplements, particularly for the broad range of chitosans that have been chemically or enzymatically modified.
Principal commercial applications include:

 

  • Preservatives
  • Food stabilizers
  • Animal feed additives
  • Anti-cholesterol additives (fat traps)

In cosmetics:

Chitosan forms a protective, moisturizing, elastic film on the surface of the skin that has the ability to bind other ingredients that act on the skin. In this way, chitosan can be used in formulating moisturizing agents such as sunscreens, organic acids, etc. to enhance their bioactivity and effectiveness. Today, chitosan is an essential component in skin-care creams, shampoos, and hairsprays due to its antibacterial properties. Many patents have been registered and new applications are just beginning to appear including the most highly prized moisturizing and antibacterial properties. Applications include

 

  • Maintain skin moisture
  • Treat acne
  • Tone skin
  • Protect the epidermis
  • Reduce static electricity in hair
  • Fight dandruff
  • Improve suppleness of hair
  • Make hair softer

For biopharmaceutical uses:

It is in the field of health that the many properties of chitosan (bacteriostatic, immunologic, antitumoral, cicatrizant, hemostatic and anticoagulant) are of interest. For example, because of its biocompatibility with human tissue, chitosan's cicatrizant properties have proven its effectiveness as a component, notably, in all types of dressings (artificial skin, corneal dressings, etc.), surgical sutures, dental implants, and in rebuilding bones and gums. Applications currently being developed include artificial skin, surgical sutures that are absorbed naturally after an operation, and corneal contact lenses. Finally, chitosan delivers and time-releases drugs used to treat animals and humans. There are many potential chitosan applications in the health field but their development calls for the use of components that comply with strict pharmaceutical-grade requirements.
Possible applications include:

 

  • Ointments for wounds
  • Surgical sutures
  • Ophthalmology
  • Orthopedics
  • Pharmaceutical products (delivery agent)
  • Contact lenses

Looking forward ...

Applications of chitosan is growing rapidly. Not only due to its multitude of applications but due to increasing environmental awareness of the population, biodegradable, and non-toxic products from 'natural' sources such as chitin and chitosan are going to be more and more appealing for the replacement of synthetic compounds. Moreover, in cosmetic and in biopharmaceutical industries, chitosan has exclusive properties which are not found in other synthetic products.

 

References

1. Knorr, D. Functional properties of chitin and chitosan. J. Food Sci. 47, pp. 593-595, 1982.
2. Roberts, G.A.F. Chitin Chemistry, Macmillan, London, 1992.
3. No, H.K. and Meyers, S.P. (1995). Preparation and characterization of chitin and chitosan (A review). J. Aquatic Food product Technol., 4, pp. 27-52 (1995).
4. Gossen, M.F.A. (1997) Applications of Chitin and Chitosan. Technomic Publishing Company Book, Lancaster, 1997.

 

Clermont Beaulieu

Clermont Beaulieu, Marinard Biotech Inc., 30 de l'Entrepôt, Rivière-au-Renard (Qc),G4X 5L4 Canada



Clermont Beaulieu received his Ph.D. from Laval University (Québec City), and did his post-doctoral studies at the Dalhousie University (Halifax) and at the University of Oxford (England). He then joined University of British Columbia as an Assistant Professor in 1991. Moved back to University of Montreal as a Professor (1991-1997) at the department of pathology. Currently, he is Asssociate Professsor at the Dept. of Biology, Université du Québec à Rimouski since 2001.



Dr. Beaulieu's research focuses on value-added products from seafood processing wastes as he continues to develop production facilities (industrial, food-grade and pharmaceutical grade) for extracting value-added bio-molecules from the sea. He has authored over 80 papers and Chaired conferences. His many honors and prizes include scholar of the Canadian Medical Research Council & Fonds de la recherche en santé du Québec (1982-'97), Quebec annual forum of chemical industries (2001), Canada Economic Development for the excellence of the regional project, and from the regional exportation bureau for business growth (2004).



Currently, he is the CEO of Marinard Biotech.


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