Tag Archives: chitin

Using insect corpses to create biodegradable plastics

Caption: Black soldier flies are a good source of chemicals to make bioplastics. Credit: Cassidy Tibbetts

The American Chemical Society (ACS) held its Fall 2023 meeting (Aug. 13 -17, 2023) and amongst roughly 12,000 presentations there was this one on insects and degradable plastics as described in an August 14, 2023 ACS news release (also on EurekAlert),

Imagine using insects as a source of chemicals to make plastics that can biodegrade later — with the help of that very same type of bug. That concept is closer to reality than you might expect. Today, researchers will describe their progress to date, including isolation and purification of insect-derived chemicals and their conversion into functional bioplastics.

The researchers will present their results at the fall meeting of the American Chemical Society (ACS). ACS Fall 2023 is a hybrid meeting being held virtually and in-person Aug. 13–17, and features about 12,000 presentations on a wide range of science topics.

“For 20 years, my group has been developing methods to transform natural products — such as glucose obtained from sugar cane or trees — into degradable, digestible polymers that don’t persist in the environment,” says Karen Wooley, Ph.D., the project’s principal investigator. “But those natural products are harvested from resources that are also used for food, fuel, construction and transportation.”

So Wooley began searching for alternative sources that wouldn’t have these competing applications. Her colleague Jeffery Tomberlin, Ph.D., suggested she could use waste products left over from farming black soldier flies, an expanding industry that he has been helping to develop.

The larvae of these flies contain many proteins and other nutritious compounds, so the immature insects are increasingly being raised for animal feed and to consume wastes. However, the adults have a short life span after their breeding days are over and are then discarded. At Tomberlin’s suggestion, those adult carcasses became the new starting material for Wooley’s team. “We’re taking something that’s quite literally garbage and making something useful out of it,” says Cassidy Tibbetts, a graduate student working on the project in Wooley’s lab at Texas A&M University.

When Tibbetts examined the dead flies, she determined that chitin is a major component. This nontoxic, biodegradable, sugar-based polymer strengthens the shell, or exoskeleton, of insects and crustaceans. Manufacturers already extract chitin from shrimp and crab shells for various applications, and Tibbetts has been applying similar techniques using ethanol rinses, acidic demineralization, basic deproteinization and bleach decolorization to extract and purify it from the insect carcasses. She says her fly-sourced chitin powder is probably purer, since it lacks the yellowish color and clumpy texture of the traditional product. She also notes that obtaining chitin from flies could avoid possible concerns over some seafood allergies. Some other researchers isolate chitin or proteins from fly larvae, but Wooley says her team is the first that she knows of to use chitin from discarded adult flies, which — unlike the larvae — aren’t used for feed.

While Tibbetts continues to refine her extraction techniques, Hongming Guo, another graduate student in Wooley’s lab, has been converting the purified fly chitin into a similar polymer known as chitosan. [emphasis mine] He does this by stripping off chitin’s acetyl groups. That exposes chemically reactive amino groups that can be functionalized and then crosslinked. These steps transform chitosan into useful bioplastics such as superabsorbent hydrogels, which are 3D polymer networks that absorb water.

Guo has produced a hydrogel that can absorb 47 times its weight in water in just one minute. This product could potentially be used in cropland soil to capture floodwater and then slowly release moisture during subsequent droughts, Wooley says. “Here in Texas, we’re constantly either in a flood or drought situation,” she explains, “so I’ve been trying to think of how we can make a superabsorbent hydrogel that could address this.” And because the hydrogel is biodegradable, she says it should gradually release its molecular components as nutrients for crops.

This summer, the team is starting a project to break down chitin into its monomeric glucosamines. These small sugar molecules will then be used to make bioplastics, such as polycarbonates or polyurethanes, which are traditionally made from petrochemicals. Black soldier flies also contain many other useful compounds that the group plans to use as starting materials, including proteins, DNA, fatty acids, lipids and vitamins.

The products made from these chemical building blocks are intended to degrade or digest when they’re discarded, so they won’t contribute to the current plastic pollution problem. Wooley’s vision for that process would align it with the sustainable, circular economy concept: “Ultimately, we’d like the insects to eat the waste plastic as their food source, and then we would harvest them again and collect their components to make new plastics,” she says. “So the insects would not only be the source, but they would also then consume the discarded plastics.”

The researchers acknowledge support and funding from the Welch Foundation and a private donation.

As you can see from the news release, there were two related presentations,

Title
Harvesting of building blocks from insect feedstocks for transformation into carbohydrate-derived superabsorbent hydrogels

Abstract
A primary interest in the Wooley laboratory is the production of functional polymers from renewable sources that are capable of reverting to those natural products once their purpose has been served. As scaled-up production of biomass-based biodegradable polymers continues to grow, we’ve recognized a need to avoid competition with resources that are important to food, fuel, construction and other societal demands. Therefore, we’re turning to unique supply chains, including harvesting of naturally-derived building blocks from black soldier flies (BSF), a rapidly growing feed crop industry. This presentation will highlight efforts to isolate carbohydrate feedstocks from BSF and transform them into superabsorbent hydrogel materials, which are designed to address global challenges with flooding and drought associated with climate change.

Title
Harvesting of naturally-derived building blocks from adult black soldier flies

Abstract
The urgent threat to our environment created by plastic pollution has continued to grow and develop as we face the well-established problems arising from traditional plastic production using petrochemicals and their accumulation. Polymeric materials constructed from natural building blocks are promising candidates to displace environmentally-persistent petrochemical counterparts, due to their similar thermal and mechanical properties and greater breadth of compositions, structures and properties, sustainability and degradability, thereby redefining the current plastic economy. A key goal in the exploration of building blocks from natural polymers is to avoid competition with resources critical to food, fuel, construction and other societal demands. This requires turning to unique supply chains, such as black soldier flies (BSF).

BSF provides an immense array of potential utility to society, ranging from being a protein source for animal feed to composting waste. However, the larvae are almost exclusively of use for these processes and the adults serve the sole purpose of reproducing. Once the adults die, they are currently considered as waste and disposed of. Intrigued with the opportunity to create a value chain using the adult BSF, studies focusing on optimization and scalability for the digestion of adult black soldier flies to produce high quality chitin and utilize it as a feedstock for the production of super-absorbent hydrogel networks will be discussed.

If you’d like to know more about this work, there’s an ACS Fall 2023 Media Briefings webpage, which includes the briefing for “Transforming flies into degradable plastics.” It runs approximately 10 mins. 29 secs.

A snout weevil at the end of the rainbow

I’ve never heard of a snout weevil before but it seems to be a marvelous creature,

Caption: Left: A photograph of the ‘rainbow’ weevil, with the rainbow-colored spots on its thorax and elytra (wing casings). Right: A microscope image of the rim of a single rainbow spot, showing the different colors of individual scales. Credit: Dr Bodo D Wilts

From a Sept. 11, 2018 news item on Nanowerk,

Researchers from Yale [University]-NUS College and the University of Fribourg in Switzerland have discovered a novel colour-generation mechanism in nature, which if harnessed, has the potential to create cosmetics and paints with purer and more vivid hues, screen displays that project the same true image when viewed from any angle, and even reduce the signal loss in optical fibres.

Yale-NUS College Assistant Professor of Science (Life Science) Vinodkumar Saranathan led the study with Dr Bodo D Wilts from the Adolphe Merkle Institute at the University of Fribourg. Dr Saranathan examined the rainbow-coloured patterns in the elytra (wing casings) of a snout weevil from the Philippines, Pachyrrhynchus congestus pavonius, using high-energy X-rays, while Dr Wilts performed detailed scanning electron microscopy and optical modelling.

They discovered that to produce the rainbow palette of colours, the weevil utilised a colour-generation mechanism that is so far found only in squid, cuttlefish, and octopuses, which are renowned for their colour-shifting camouflage.

A Sept. 11, 2018 Yale-NUS College news release (also on EurekAlert), which originated the news item, offers more on the weevil and on the research,

P. c. pavonius, or the “Rainbow” Weevil, is distinctive for its rainbow-coloured spots on its thorax and elytra (see attached image). These spots are made up of nearly-circular scales arranged in concentric rings of different hues, ranging from blue in the centre to red at the outside, just like a rainbow. While many insects have the ability to produce one or two colours, it is rare that a single insect can produce such a vast spectrum of colours. Researchers are interested to figure out the mechanism behind the natural formation of these colour-generating structures, as current technology is unable to synthesise structures of this size.

“The ultimate aim of research in this field is to figure out how the weevil self-assembles these structures, because with our current technology we are unable to do so,” Dr Saranathan said. “The ability to produce these structures, which are able to provide a high colour fidelity regardless of the angle you view it from, will have applications in any industry which deals with colour production. We can use these structures in cosmetics and other pigmentations to ensure high-fidelity hues, or in digital displays in your phone or tablet which will allow you to view it from any angle and see the same true image without any colour distortion. We can even use them to make reflective cladding for optical fibres to minimise signal loss during transmission.”

Dr Saranathan and Dr Wilts examined these scales to determine that the scales were composed of a three-dimensional crystalline structure made from chitin (the main ingredient in insect exoskeletons). They discovered that the vibrant rainbow colours on this weevil’s scales are determined by two factors: the size of the crystal structure which makes up each scale, as well as the volume of chitin used to make up the crystal structure. Larger scales have a larger crystalline structure and use a larger volume of chitin to reflect red light; smaller scales have a smaller crystalline structure and use a smaller volume of chitin to reflect blue light. According to Dr Saranathan, who previously examined over 100 species of insects and spiders and catalogued their colour-generation mechanisms, this ability to simultaneously control both size and volume factors to fine-tune the colour produced has never before been shown in insects, and given its complexity, is quite remarkable. “It is different from the usual strategy employed by nature to produce various different hues on the same animal, where the chitin structures are of fixed size and volume, and different colours are generated by orienting the structure at different angles, which reflects different wavelengths of light,” Dr Saranathan explained.

The research was partly supported though the National Centre of Competence in Research “Bio-Inspired Materials” and the Ambizione program of the Swiss National Science Foundation (SNSF) to Dr Wilts, and partly through a UK Royal Society Newton Fellowship, a Linacre College EPA Cephalosporin Junior Research Fellowship, and Yale-NUS College funds to Dr Saranathan. Dr Saranathan is currently part of a research team led by Yale-NUS College Associate Professor of Science Antonia Monteiro, which has recently been awarded a separate Competitive Research Programme (CRP) grant by Singapore’s National Research Foundation (NRF) to examine the genetic basis of the colour-generation mechanism in butterflies. Dr Saranathan and Dr Monteiro are both also from the Department of Biological Sciences at the National University of Singapore (NUS) Faculty of Science. In addition, Dr Saranathan is affiliated with the NUS Nanoscience and Nanotechnology Initiative.

Here’s a link to and a citation for the paper,

Literal Elytral Rainbow: Tunable Structural Colors Using Single Diamond Biophotonic Crystals in Pachyrrhynchus congestus Weevils by Bodo D. Wilts, Vinodkumar Saranathan. Samll https://doi.org/10.1002/smll.201802328 First published: 15 August 2018

This paper is behind a paywall.

Cellulose- and chitin-based biomaterial to replace plastics?

Although the term is not actually used in the news release, one of the materials used to create a new biomaterial could safely be described as nanocellulose. From a Sept. 20, 2017 Pennsylvania State University (Penn State) news release (also on EurekAlert) by Jeff Mulhollem,

An inexpensive biomaterial that can be used to sustainably replace plastic barrier coatings in packaging and many other applications has been developed by Penn State researchers, who predict its adoption would greatly reduce pollution.

Completely compostable, the material — a polysaccharide polyelectrolyte complex — is comprised of nearly equal parts of treated cellulose pulp from wood or cotton, and chitosan, which is derived from chitin — the primary ingredient in the exoskeletons of arthropods and crustaceans. The main source of chitin is the mountains of leftover shells from lobsters, crabs and shrimp consumed by humans.

These environmentally friendly barrier coatings have numerous applications ranging from water-resistant paper, to coatings for ceiling tiles and wallboard, to food coatings to seal in freshness, according to lead researcher Jeffrey Catchmark, professor of agricultural and biological engineering, College of Agricultural Sciences.

“The material’s unexpected strong, insoluble adhesive properties are useful for packaging as well as other applications, such as better performing, fully natural wood-fiber composites for construction and even flooring,” he said. “And the technology has the potential to be incorporated into foods to reduce fat uptake during frying and maintain crispness. Since the coating is essentially fiber-based, it is a means of adding fiber to diets.”

The amazingly sturdy and durable bond between carboxymethyl cellulose and chitosan is the key, he explained. The two very inexpensive polysaccharides — already used in the food industry and in other industrial sectors — have different molecular charges and lock together in a complex that provides the foundation for impervious films, coatings, adhesives and more.

The potential reduction of pollution is immense if these barrier coatings replace millions of tons of petroleum-based plastic associated with food packaging used every year in the United States — and much more globally, Catchmark noted.

He pointed out that the global production of plastic is approaching 300 million tons per year. In a recent year, more than 29 million tons of plastic became municipal solid waste in the U.S. and almost half was plastic packaging. It is anticipated that 10 percent of all plastic produced globally will become ocean debris, representing a significant ecological and human health threat.

crab shells

The material is comprised of cellulose pulp from wood or cotton, and chitosan, derived from chitin, the primary ingredient in the exoskeletons of arthropods and crustaceans. The main source of chitin is shells from lobsters, crabs and shrimp. Image: © iStock Photo OKRAD

The polysaccharide polyelectrolyte complex coatings performed well in research, the findings of which were published recently in Green Chemistry. Paperboard coated with the biomaterial, comprised of nanostructured fibrous particles of carboxymethyl cellulose and chitosan, exhibited strong oil and water barrier properties. The coating also resisted toluene, heptane and salt solutions and exhibited improved wet and dry mechanical and water vapor barrier properties.

“These results show that polysaccharide polyelectrolyte complex-based materials may be competitive barrier alternatives to synthetic polymers for many commercial applications,” said Catchmark, who, in concert with Penn State, has applied for a patent on the coatings.

“In addition, this work demonstrates that new, unexpected properties emerge from multi-polysaccharide systems engaged in electrostatic complexation, enabling new high-performance applications.”

Catchmark began experimenting with biomaterials that might be used instead of plastics a decade or so ago out of concerns for sustainability. He became interested in cellulose, the main component in wood, because it is the largest volume sustainable, renewable material on earth. Catchmark studied its nanostructure — how it is assembled at the nanoscale.

He believed he could develop natural materials that are more robust and improve their properties, so that they could compete with synthetic materials that are not sustainable and generate pollution — such as the low-density polyethylene laminate applied to paper board, Styrofoam and solid plastic used in cups and bottles.

“The challenge is, to do that you’ve got to be able to do it in a way that is manufacturable, and it has to be less expensive than plastic,” Catchmark explained. “Because when you make a change to something that is greener or sustainable, you really have to pay for the switch. So it has to be less expensive in order for companies to actually gain something from it. This creates a problem for sustainable materials — an inertia that has to be overcome with a lower cost.”

lab vials

The amazingly sturdy and durable bond between carboxymethyl cellulose and chitosan is the key. The two very inexpensive polysaccharides, already used in the food industry and in other industrial sectors, have different molecular charges and lock together in a complex that provides the foundation for impervious films, coatings, adhesives and more. Image: Penn State

Funded by a Research Applications for Innovation grant from the College of Agricultural Sciences, Catchmark currently is working to develop commercialization partners in different industry sectors for a wide variety of products.

“We are trying to take the last step now and make a real impact on the world, and get industry people to stop using plastics and instead use these natural materials,” he said. “So they (consumers) have a choice — after the biomaterials are used, they can be recycled, buried in the ground or composted, and they will decompose. Or they can continue to use plastics that will end up in the oceans, where they will persist for thousands of years.”

Also involved in the research were Snehasish Basu, post-doctoral scholar, and Adam Plucinski, master’s degree student, now instructor of engineering at Penn State Altoona. Staff in Penn State’s Material Research Institute provided assistance with the project.

The U.S. Department of Agriculture supported this work. Southern Champion Tray, of Chattanooga, Tennessee, provided paperboard and information on its production for experiments.

Here’s a link to and a citation for the paper,

Sustainable barrier materials based on polysaccharide polyelectrolyte complexes by
Snehasish Basu, Adam Plucinski, and Jeffrey M. Catchmark. Green Chemistry 2017, 19, 4080-4092 DOI: 10.1039/C7GC00991G

This paper is behind a paywall. One comment, I found an anomaly on the page when I visited. At the top of the citation page, it states that this is issue 17 of Green Chemistry but the citation in the column on the right is “2017, 19 … “, which would be issue 19.

Prawn (shrimp) shopping bags and saving the earth

Using a material (shrimp shells) that is disposed of as waste to create a biodegradable product (shopping bags) can only be described as a major win. A Jan. 10, 2017 news item on Nanowerk makes the announcement,

Bioengineers at The University of Nottingham are trialling how to use shrimp shells to make biodegradable shopping bags, as a ‘green’ alternative to oil-based plastic, and as a new food packaging material to extend product shelf life.

The new material for these affordable ‘eco-friendly’ bags is being optimised for Egyptian conditions, as effective waste management is one of the country’s biggest challenges.

An expert in testing the properties of materials, Dr Nicola Everitt from the Faculty of Engineering at Nottingham, is leading the research together with academics at Nile University in Egypt.

“Non-degradable plastic packaging is causing environmental and public health problems in Egypt, including contamination of water supplies which particularly affects living conditions of the poor,” explains Dr Everitt.

Natural biopolymer products made from plant materials are a ‘green’ alternative growing in popularity, but with competition for land with food crops, it is not a viable solution in Egypt.

A Jan. 10, 2017 University of Nottingham press release, which originated the news item,expands on the theme,

This new project aims to turn shrimp shells, which are a part of the country’s waste problem into part of the solution.

Dr Everitt said: “Use of a degradable biopolymer made of prawn shells for carrier bags would lead to lower carbon emissions and reduce food and packaging waste accumulating in the streets or at illegal dump sites. It could also make exports more acceptable to a foreign market within a 10-15-year time frame. All priorities at a national level in Egypt.”

Degradable nanocomposite material

The research is being undertaken to produce an innovative biopolymer nanocomposite material which is degradable, affordable and suitable for shopping bags and food packaging.

Chitosan is a man-made polymer derived from the organic compound chitin, which is extracted from shrimp shells, first using acid (to remove the calcium carbonate “backbone” of the crustacean shell) and then alkali (to produce the long molecular chains which make up the biopolymer).

The dried chitosan flakes can then be dissolved into solution and polymer film made by conventional processing techniques.

Chitosan was chosen because it is a promising biodegradable polymer already used in pharmaceutical packaging due to its antimicrobial, antibacterial and biocompatible properties. The second strand of the project is to develop an active polymer film that absorbs oxygen.

Enhancing food shelf life and cutting food waste

This future generation food packaging could have the ability to enhance food shelf life with high efficiency and low energy consumption, making a positive impact on food wastage in many countries.

If successful, Dr Everitt plans to approach UK packaging manufacturers with the product.

Additionally, the research aims to identify a production route by which these degradable biopolymer materials for shopping bags and food packaging could be manufactured.

I also found the funding for this project to be of interest (from the press release),

The project is sponsored by the Newton Fund and the Newton-Mosharafa Fund grant and is one of 13 Newton-funded collaborations for The University of Nottingham.

The collaborations, which are designed to tackle community issues through science and innovation, with links formed with countries such as Brazil, Egypt, Philippines and Indonesia.

Since the Newton Fund was established in 2014, the University has been awarded a total of £4.5m in funding. It also boasts the highest number of institutional-led collaborations.

Professor Nick Miles Pro-Vice-Chancellor for Global Engagement said: “The University of Nottingham has a long and established record in global collaboration and research.

The Newton Fund plays to these strengths and enables us to work with institutions around the world to solve some of the most pressing issues facing communities.”

From a total of 68 universities, The University of Nottingham has emerged as the top awardee of British Council Newton Fund Institutional Links grants (13) and is joint top awardee from a total of 160 institutions competing for British Council Newton Fund Researcher Links Workshop awards (6).

Professor Miles added: “This is testament to the incredible research taking place across the University – both here in the UK and in the campuses in Malaysia and China – and underlines the strength of our research partnerships around the world.”

That’s it!

Mining uranium from the ocean

We are running short of uranium as terrestrial mining of this element has become more hazardous environmentally. A July 18, 2014 news item on Azonano highlights an ‘ocean mining’ uranium project at the University of Alabama (US),

The U.S. Department of Energy [DOE] selected a University of Alabama [UA] start-up company for an approximate $1.5 million award to refine an alternative material to potentially extract uranium from the ocean.

Uranium, which naturally occurs in seawater and in the Earth’s crust, is the fuel for nuclear power. For decades, scientists have sought a more economical and efficient way to remove it from the ocean, as the terrestrial supply is dwindling and environmentally unfriendly to mine.

A July 17, 2014 University of Alabama news release, which originated the news item, describe the University of Alabama’s unique approach to the problem of extracting uranium from the ocean (Note: A link has been removed),

“Every scientist in the world, except us, who is trying to do this is working with plastics,” said Dr. Gabriela Gurau, a chemist and CEO of the UA-based company, 525 Solutions.

Instead, the UA company is developing an adsorbent, biodegradable material made from the compound chitin, which is found in shrimp shells and in other crustaceans and insects. The researchers have developed transparent sheets, or mats, comprised of tiny chitin fibers, modified for the task. When suspended beneath the ocean’s surface, the mats are designed to withdraw uranium.

“Once you put it in the ocean, it will attract uranium like a magnet, and uranium will stick to it,” said Gurau, a University of Alabama alumna.

If one day implemented, the mats, with uranium attached, would be taken to an industrial plant where the nuclear fuel source would be removed.

Earlier work led by Dr. Robin Rogers, Robert Ramsay Chair of Chemistry at UA and director of UA’s Center for Green Manufacturing, initially proved the concept for extracting uranium using chitin. Rogers is an owner/founder of 525 Solutions and serves as a scientific adviser to the company’s representatives.

“The oceans are estimated to contain more than a thousand times the amount of uranium found in total in any known land deposit,” Rogers said. “Fortunately, the concentration of uranium in the ocean is very, very low, but the volume of the oceans is, of course, very, very high. Assuming we could recover only half of this resource, this much uranium could support 6,500 years of nuclear capacity.”

Removing chitin, in a pure form, from shells had previously proven difficult, but Rogers and his UA colleagues discovered a way to use a relatively new class of solvents, called ionic liquids, for removal. Ionic liquids are liquid salts which have other unique and desirable properties that traditional solvents do not. Rogers is recognized as a world-leader in the field of  ionic liquids.

UA researchers use a time-honored laboratory technique called electrospinning to produce the mats. In this process, the scientists use a specially-prepared, chitin-based, ionic liquid solution, which is loaded in the electrospinning apparatus. Some 30,000 volts of electricity are applied, spinning the fibers into a water bath. After several hours, nanofiber mats, consisting of fibers much thinner than a strand of a spider’s web, form, weaved together into a solid sheet.

The increased surface area the nanomats provide is central to the project, said Dr. Julia Shamshina, the company’s chief technology officer and also a UA alumna.

“The larger the surface area, the larger modifications we can make and the more uranium it will uptake,” Shamshina said. “If you have one very thick fiber and 10 which, when combined, equal the size of the thick fiber, the ten smaller ones will take up hundreds, or even thousands, of times more uranium.”

Rogers extolled the potential environmental benefits of  the company’s approach and addressed cost factors.

“Mining uranium from land is a very dirty, energy intensive process, with a lot of hazardous waste produced,” Rogers said. “If we eliminate land mining by mining from the ocean, we not only clean up the ocean, we eliminate all of the environmental problems with terrestrial mining.

“Research studies have shown that uranium can be extracted from the ocean, but the process remains prohibitively costly,” said Rogers, a  two-time UA graduate. “The search for more effective adsorbents — which is what we’re doing  – is under way and expected to solve this issue.”

Gurau said the two-year grant, from the DOE’s Office of Science through its Small Business Innovation Research and Small Business Technology Transfer programs, will enable the researchers to refine their processes, measure costs and conduct an environmental analysis.

“We need to know if it’s viable from an economic standpoint,” Gurau said. “I think this is a critical step in getting this to the pilot-plant stage.”

Think shrimp for wound healing and face creams for age-defying skin

A research team at Fairleigh Dickinson University (New Jersey, US) has taken the first step towards developing new treatments for skin wounds and, possibly, new anti-aging cosmetics. From the March 16, 2012 news item on physorg.com,

… Mihaela Leonida of Fairleigh Dickinson University, in Teaneck, New Jersey and colleagues writing in the International Journal of Nano and Biomaterials describe how they have prepared nanoparticles of chitosan that could have potential in preventing infection in wounds as well as enhancing the wound-healing process itself by stimulating skin cell growth.

Here’s where the shrimp figure in,

Chitosan is a natural, non-toxic and biodegradable, polysaccharide readily obtained from chitin, the main component of the shells of shrimp, lobster and the beak of the octopus and squid. Its antimicrobial activity is well known and has been exploited in dentistry to prevent caries and as preservative applications in food packaging. It has even been tested as an additive for antimicrobial textiles used in clothing for healthcare and other workers.

You can also find this March 16, 2012 news item on Nanowerk,

The team made their chitosan nanoparticles (CNP) using an ionic gelation process with sodium tripolyphosphate. This process involves the formation of bonds between polymers strands, a so-called cross-linking process. Conducted in these conditions it precludes the need for complex preparative chemistry or toxic solvents. CNP can also be made in the presence of copper and silver ions, known antimicrobial agents. The researchers’ preliminary tests show the composite materials to have enhanced activity against two representative types of bacteria.

… The team has also demonstrated that the CNP have skin regenerative properties in tests on skin cell fibroblasts and keratinocytes, in the laboratory, which might even have implications for anti-aging skin care products.

Shrilk—save your insect skeletons, they may come in handy

If you should happen to find a dead beetle or other insect with a hard exoskeleton, take a good look and marvel at strength that doesn’t require bulk or weight. Scientists at the Wyss Institute for Biologically Inspired Engineering at Harvard University have been inspired by those exoskeletons, made of  something called insect cuticle, to create a new material, shrilk. From the Dec. 13, 2011 news item on phosorg.com,

Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University have developed a new material that replicates the exceptional strength, toughness, and versatility of one of nature’s more extraordinary substances—insect cuticle. Also low-cost, biodegradable, and biocompatible, the new material, called “Shrilk,” could one day replace plastics in consumer products and be used safely in a variety of medical applications.

Natural insect cuticle, such as that found in the rigid exoskeleton of a housefly or grasshopper, is uniquely suited to the challenge of providing protection without adding weight or bulk. As such, it can deflect external chemical and physical strains without damaging the insect’s internal components, while providing structure for the insect’s muscles and wings. It is so light that it doesn’t inhibit flight and so thin that it allows flexibility. Also remarkable is its ability to vary its properties, from rigid along the insect’s body segments and wings to elastic along its limb joints.

Insect cuticle is a composite material consisting of layers of chitin, a polysaccharide polymer, and protein organized in a laminar, plywood-like structure. Mechanical and chemical interactions between these materials provide the cuticle with its unique mechanical and chemical properties. By studying these complex interactions and recreating this unique chemistry and laminar design in the lab, Fernandez [Javier G. Fernandez] and Ingber [Donald Ingber] were able to engineer a thin, clear film that has the same composition and structure as insect cuticle. The material is called Shrilk because it is composed of fibroin protein from silk and from chitin, which is commonly extracted from discarded shrimp shells. [emphasis mine]

The researchers say that shrilk could be used as an environmentally-safe and biodegradable alternative to plastic, e.g. trash bags, diapers, and packaging. It could also be used to suture wounds.