Polymers May Fill the Gap for Bone Growth

Polycaprolactone (PCL), the type of polymer used in "bone foam."

A sample of polycaprolactone (PCL), the type of polymer used in “bone foam.”

Many people have to live with facial deformities due to a gap in their bone structure. These gaps can be caused by an injury, tumor removal, or birth defect. If the holes are too big, bone cannot grow to span the gap and close it. In this situation, a bone graft can be done to fill the hole, but the grafts don’t always take and can be ineffective at replacing the intricate structure of facial bones.

The bone graft must also be harvested from the patient — a challenging procedure. Then the bone must be formed to fill the gap, and it’s difficult to create a perfect fit. There are alternatives to bone grafting such as bone cement (a combination of polymethyl methacrylate (PMMA) and methyl methacrylate (MMA), or bone putties. The major downside to these materials is they lack the porous nature needed to proliferate natural bone growth, which inhibits regeneration of the host’s bone.

Turning to Polymers

Enter Melissa A. Grunlan, Ph.D., of Texas A & M University. Dr. Grunlan and her team have created a foamlike polymer sponge that can fill in bone gaps for those with facial deformities. The foam is made of polycaprolactone (PCL), a known biomaterial used in sutures and other applications. PCL is stiff at 98.6°F (body temperature) and pliable at 140°F or above, and it degrades in the body at a safe and slow rate.

The “bone foam” would be heated by the surgeon in salt water; when optimal temperature is reached, it would be formed to into the shape of the missing piece of bone. After the foam is put in place, it would stiffen at the lower body temperature. It would then act as a scaffold, with bone cells gradually moving in to replace the foam, which would slowly and naturally degrade and be absorbed by the body, then expelled. Grunlan estimates that considering the rates of bone growth and degradation of the PCL, an implanted patient should have full bone growth after approximately a year.

Boning Up

Grunlan points out that during experiments, she and her team coated the PCL with another polymer, polydopamine, which encourages bone development. They then seeded the polymers with human bone cells. After a couple of days of observation, they noticed not only the growth of new bone tissue, but also the proliferation of proteins vital to bone formation.

So far the only tests have been executed in a lab setting. According to Grunlan, the next phase would be to use mice to determine bone growth in a live specimen before moving on to clinical trials. There is still quite a bit of testing to go regarding this new foamy wonder, but with FDA approval, doctors may have a new, easier, and more precise medical product to treat patients with facial bone gaps. Other possible applications for this type of bone-regenerating technique may include aiding those with a slower rate of bone development such as the elderly.

So, you might say this polymer is “Bad to the Bone,” because it’s good for bone growth!

Image by Steve Jurvetson.
Source: “This Sponge-Like Polymer Could Fix Facial Deformities,” by Nick Stockton, www.wired.com, August 14, 2014.
Source: “This Sponge Could Help Fill Gaps Where Bone Can’t Regrow Itself,” by Robert Sorokanich, www.gizmodo.com, August 14, 2014.
Source: “Continuous Gradient Scaffolds for Rapid Screening of Cell-Material Interactions and Interfacial Tissue Regeneration,” by Brennan M. Bailey, et al., Acta Biomaterialia, September 2013, DOI: 10.1016/j.actbio.2013.05.012.

The Plastic Bank Lets You Deposit Your Recyclable Plastics For Cash — It Just Makes Cents!

three plastic bottles in shape of recycling logoThe Plastic Bank is an endeavor to create value in recycling in countries with high poverty levels and low recycling rates. The Plastic Bank’s success could help reduce the amount of plastic in our oceans. It could also serve as a humanitarian project that fights poverty at the same time. The first Plastic Bank will open in Lima, Peru.

How It Works

People are encouraged to bring in recyclable plastics (i.e. polyethylene terephthalate (PET or PETE) and high-density polyethylene (HDPE) among others) and are offered monetary compensation for their effort. The Plastic Bank sorts and sends out the plastic for recycling. The recycled material can then be used for 3-D printing as seen in this video:

The company coined the term SocialPlastic™ for the recycled material produced by the Plastic Bank endeavor. Consumers are encouraged to call companies that make their favorite products and ask them to use SocialPlastic™ when it becomes available.

The “Social Plastic” terminology is a way for consumers to identify with the plastic collected as a means to improve the planet through their purchasing power. The call to action on their website states:

Please help us lead the Social Good movement by ASKING your favourite brands to use recycled Social Plastic™ when ever plastic is needed to manufacture a product. Together we can reduce global poverty and plastic pollution.

Changing The World

By “revealing value in plastic,” the recyclable trash becomes a valuable commodity. The Plastic Bank puts money into the hands of the people who need it most while encouraging a cleaner environment. This creates safer and more hygienic surroundings, cleaning up the pollution in waterways and on the streets. David Katz, founder of The Plastic Bank, hopes to rid the world of plastic polluting the land, waterways, and oceans. Here’s what he says about the project:

The Plastic Bank project helps the poor while cleaning up the environment and creates a new and valuable product in the process. It’s a win-win-win any way you look at it.

Do You Know Your Recycling Numbers?

People collecting material for the Plastic Bank will not need to know the differences between plastics in order to redeem them. The main objective is collecting a significant volume from the environment. Plastics collected will be sorted by the bank for various uses.

The types of recyclable plastic vary and are easily recognizable thanks to the classification number in the triangle on the bottom of the container. Here’s a look at what the codes mean:

1 is for PET or PETE (polyethylene terephthalate). This plastic is most widely used as bottles for drinks, medicine bottles, and food containers among many others. PETE is frequently recycled and used to make tote bags, carpet, polar fleece, and fiberfill for winter outerwear.

2 is for HDPE (high-density polyethylene). HDPE is used to make milk jugs, motor oil bottles and hair care products. This plastic is usually recycled and used for recycling containers, floor tile, picnic tables, and fencing.

3 is for PVC (polyvinyl chloride). PVC is used for pipes usually for plumbing. It generally isn’t recycled but when it is it’s used as flooring, mudflaps, speed bumps, and more.

4 is for LDPE (low-density polyethylene). This type of plastic is used as cling wrap, grocery and sandwich bags, as well as squeeze bottles. It’s also not commonly recycled but when it is it’s used for making furniture, trash cans, trash can liners, lumber, and much more.

5 is for PP (polypropylene). It is used in products such as medicine bottles, syrup bottles, Tupperware, and plastic bottle caps. While PP isn’t typically recycled, it is accepted in many areas. When recycled it can make battery cables, ice scrapers, bins, and rakes, among other items.

6 is for PS (polystyrene). PS is widely known as Styrofoam. It’s used in making packing peanuts, coffee cups, and take-out containers. The recycling process is difficult but can be accomplished. The recycled material is used for insulation, egg cartons, rulers, and license plate frames, to name a few.

7 designates miscellaneous types of plastic that are not easy to recycle (i.e. polycarbonate PC or polylactide). PC is used in making CDs and DVDs, baby bottles, and large water bottles for dispensing. When PC can be recycled, the material can be used to make plastic lumber, as well as other custom-made items.

Do your part by always trying to use plastics that are recyclable, and please recycle whatever you can, whenever you can. Ask your favorite brands to incorporate SocialPlastic™. Maybe we can help The Plastic Bank to reduce pollution and poverty in the world. We only have one planet, and we’re all in it together — let’s keep it clean.

Image by picsfive
World’s First 3D Printed Item Made from Recycled Plastic from the Ocean,” by Derek Markham
Our Story,” by The Plastic Bank, www.plasticbank.org
The Different Types Of Plastics And Classification,” by Jill Tooley
What Do Recycling Symbols on Plastics Mean?” by Brian Clark Howard

New Polymer Biomaterial Advances Wound and Burn Healing

polymer nanosheet for bandageBandages are great for standard cuts and scrapes. However, when you get a cut in an area that’s not so easy to bandage – for example, between your fingers or toes – finding a bandage that will stay in place to protect the wound is serious business. New solutions require medical device testing.

Yosuke Okamura, Ph.D., had a solution to this problem in mind when he created a new kind of bandage. The new design uses ultra-thin, transparent, sticky, and extraordinarily flexible nanosheets made of the biodegradable polyester poly-L-lactic acid (PLLA). The thin coating clings to bends and wrinkles in the skin while still adhering to flat and broad surfaces. It does this without the addition of adhesives, making it an ideal bandage for any type of wound.

“The nanosheets can adhere not only to flat surfaces, but also to uneven and irregular surfaces without adding any adhesives,” said Okamura, a researcher at the Department of Life Science and Medical Bioscience Graduate School of Advanced Science and Engineering at Waseda University in Japan.

Screen shot2 2014-08-12 at 1.36.23 PMThe PLLA is placed into a test tube with water and spun, disrupting the sheets and creating smaller pieces. The liquid and fiber are then poured out onto a flat surface where the fibers overlap and dry to form a thin nanosheet of material. The material’s ability to coat small and difficult contours was tested by dipping into the preparation irregularly shaped objects such as a needle and the digits from a mouse paw. The nanosheet covered each of the objects extensively, including the bends and wrinkles of the mouse digits. The material dried and stayed in place, keeping bacteria out.

But Wait, There’s More…

This discovery can change the way burn victims are cared for in hospitals. Burns are highly susceptible to infection. In order for a burn to heal properly, the bandage must be impenetrable to bacteria. The most common bacteria to infect a burn wound is Pseudomonas aeruginosa. It has also been known to cause skin infections and deadly hospital-induced infections. There are antibiotic-resistant strains that are very dangerous.

The nanosheet dressing was able to keep bacteria at bay for three days. Upon application of a second layer, the bacteria was kept out for six days. This level of protection from bacteria would significantly cut down on the number of dressing changes a burn patient will have to endure. It will also offer burn victims a chance to heal without the added worry of infection slowing the process or causing harm. The material has not yet been approved for human trials pending further medical testing for safety and efficacy.

And Even More…

The PLLA nanosheets are just the beginning. Okamura and his group have begun development on another highly flexible, fiber coating polymer with a phosphorylcholine group. The combined materials are compatible with blood and could be used as coatings on medical devices.

Thanks to the wonderful world of polymers, in the future those annoying cuts in hard-to-cover places or a burn from the grill will be covered completely, and nasty bacteria will be kept out.

Images by Yosuke Okamura.
Cling Wrap For Burn Wounds: Biomaterial Nanosheets Coat Tricky Burns, Blocks Out Infection,” by Phys.org, www.phys.org, August 10, 2014
Nanosheets To Protect From Burn Wound Infections,” by mangalorean, www.magalorean.com, August 11, 2014
Fragmentation of Poly(lactic acid) Nanosheets and Patchwork Treatment for Burn Wounds,” Yosuke Okamura, et al., Advanced Materials, November 1, 2012, DOI: 10.1002/adma.201202851

The Polymer That Lights the Way for MRI Scans

mri scan of human brainA PEEK (polyaryletherketone) polymer capsule, the size of a grain of rice and containing a water-based cobalt salt solution, is lighting up possibilities for magnetic resonance imaging (MRI) scans.

The What and How

During an MRI, the ability to visualize the internal structures is greatly increased when using a contrast agent. This technology is excellent for focusing on certain areas of the body. The agents are usually taken orally or administered intravenously. Current standard contrasting agents include intravenous gadolinium, which is used for boosting visualization of vessels or brain tumors, and oral gadolinium, which is used for the gastrointestinal tract.

The MRI creates a very strong magnetic field while a radio frequency is pulsed, causing some atoms to spin and then to relax when the pulse stops. The relaxed state sends out a signal that the scanner mathematically translates into an image. The image itself can use varying weights to give a higher or lower signal.

Making High-Tech Even High-Techier

In his research on prostate cancer at the University of Texas’ MD Anderson Cancer Center, Steve Frank, M.D., was trying to improve the process of MRI scans in brachytherapy. The brachytherapy procedure includes the implantation of radioactive seeds in the treatment of prostate cancer. Up to 100 seeds are directly implanted into the prostate and held in place by inserting a spacer on each side of the seeds. This procedure is standard for prostate cancer treatment as it is successful, accessible, and minimally invasive, as well as having a low occurrence of erectile dysfunction. Radiation released from the seeds is confined to the area within the prostate, penetrating the tissue.

The use of the MRI to identify the seeds accurately illustrates certain parts of the prostate but cannot identify the implanted seeds. This inadequacy is due to the paramagnetic titanium shell of the seed, which shows a void or “black hole” in the MRI image. The void makes the seeds indistinguishable from the surrounding vessels.

MRI_Marker_in_StrandIn his research, Frank developed the first permanently implantable MRI contrast agent. This technology can be used when a specific place of interest in the body needs to be observed – for example, a biopsy site. The PEEK capsules, which Frank calls Sirius capsules, have been in development since 2006. However, because the original beads he used contained titanium, Frank had a hard time finding a coating that could stop the “black hole” created by the MRIs.

He began working with Karen Martirosyan, Ph.D, a bioengineer at the University of Texas. Together they discovered a new contrasting agent that they refer to as “cobalt-chloride complex contrasting agent” or C4. Cobalt’s paramagnetic properties were clearly visible using an MRI. Moreover, they decided that instead of using standard spacers to hold the seeds in place, they would use plastic capsules filled with a droplet of C4. Frank said:

‘To be able to take a novel contrast agent and place it inside a polymer tube for visualization, it provides the potential for additional applications that may have not been thoroughly thought through. It’s exciting on that side, too.’

PEEK was chosen for its standard use in medical equipment and its low degradation rate with exposure to radiation. While micromolding and extrusion were both considered in regards to fabrication, extrusion was chosen based on reproducibility.

The capsules are 5.5 mm long, with a diameter of 0.8 mm; the walls are 0.1 mm thick.

Frank and Martirosyan started C4 Imaging to develop Sirius capsules and won FDA 510(k) approval for Sirius in late 2013. They now have an undisclosed contract ramping up to start production next month. Andrew Bright, the former vice president of sales and marketing at GE Healthcare’s Oncura business, joined C4 Imaging as its CEO in 2010.

When it comes to MRI scans, it seems that PEEK has helped in giving us a visually enhanced peek into the human body.

Images by Mark Herreid, 123RF and C4Imaging.com.
The Material That Is Lighting Up MRI Scans,” by Chris Newmarker, www.qmed.com, July 25, 2014
Prostate Brachytherapy,” by C4 Imaging, www.c4imaging.com
Novel MRI Technology,” by C4 Imaging, www.c4imaging.com
A Biodistribution and Toxicity Study of Cobalt Dichloride-N-Acetyl Cysteine in an Implantable MRI Marker for Prostate Cancer Treatment,” by Steven J Frank et al., International Journal of Radiation Oncology*Biology*Physics, March 15, 2013, DOI: 10.1016/j.ijrobp.2012.09.007
MRI Contrasting Agent,” by Wikipedia