Last July’s 4th International Congress on Ceramics was the setting for multiple presentations on the use of advanced ceramics in various industries. Among the application areas covered were biology and medicine. This post is a recap of a paper on the topic from the May/June issue of AcerS’ International Journal of Applied Ceramic Technology.
According to author Vivek Pawar, a materials researcher at Smith and Nephew Inc. (Memphis, Tenn.), seven presentations at the event focused on bioceramics for orthopedic, tissue engineering, and dentistry applications, as well as on innovative manufacturing techniques and novel ceramic materials for use as bearing surfaces.
Pawar writes that the bioceramics used in hard or soft tissue replacement can be classified as bioactive glasses made mainly from calcium oxide, sodium oxide, phosphorus pentoxide, and silica; apatite-based ceramics made from synthetic hydroxyapatite and calcium phosphates; and ceramics that are used as bearing surfaces for orthopedic applications.
Since development of the first bioactive glass by Larry Hench more than 40 years ago, few alterations have been made to the materials’ composition. Pawar reports current research in the area focuses on developing compositions that maintain or increase bioactivity after crystallization during sintering. The goal is to develop low-density, easily machinable materials with fracture toughness greater than 1 MPa m1/2.
A new material aimed at meeting those criteria is a product called ‘Biosilicate’ from Vitrovita (São Carlos, Brazil), which is reported to have antimicrobial properties. In one study assessing the effectiveness of Biosilicate against a variety of microorganisms, the material displayed activity against all the bacteria except one, drastically reducing the number of viable cells in the first 10 minutes of contact.
Hydroxyapatite (HA) coatings are commonly used in orthopedic devices to promote bone in-growth on metallic implants. Pawar writes that current research focuses on increasing the material’s bioactivity by incorporating bioactive ions in the HA crystal structure. Researchers have investigated magnesium, strontium, silver, zinc, titanium, iron, sodium, and potassium cationic substitutions. Anionic substitutions considered include fluorine, chlorine, hydroxide, phosphate, and silicate ions. These ions perturb the HA crystal structure and change solubility. Current work is aimed at understanding how each of these ions affects bioactivity. Substitutions with silver, for example, have increased HA solubility and shown bactericidal effects.
Hip arthroplasty remains the predominant use for ceramic bearing surfaces in orthopedic implants, and materials used in this application have included alumina, yttria-stabilized zirconia, and zirconia-toughened alumina. Newer ceramic materials with higher strength and toughness than alumina and reduced risk of fracture include ‘Biolox delta‘ from CeramTec (Plochingen, Germany). A zirconia-toughened alumina with small additions of chromium oxide and strontium aluminate, the material is “being considered for challenging applications such as hip resurfacing femoral heads and knee femoral components,” Pawar writes.
Another potential bearing material is silicon nitride, which offers high strength and toughness, excellent wear resistance, imaging compatibility, affinity to bone, and an antibacterial surface. Produced by Amedica (Salt Lake City, Utah), Si3N4 is already being used in spinal devices.
In the article Pawar notes, “Although no significant clinical problems have been reported with these two materials, a long-term clinical followup will be required to evaluate the performance of these materials.”
Innovations in ceramic processing techniques are being driven by specific biomedical applications. For example, camphene freeze casting processes are being used to create a 3-D interconnected porous bioceramic scaffold with the aim of producing a bioactive glass scaffold with high strength and bioactivity.
Also proposed is a 3-D printing process for apatite-based ceramics using stereolithography. The method is said to enable production of customized solutions based on clinical needs. A limited clinical study of the technology for repair of large craniofacial bone defects is under way at 3DCeram (Limoges, France).
Finally, nanoceramics with particle sizes of 1 to 100 nm are the focus of considerable research. The unique properties of materials produced using nanoparticles—higher surface-to-volume ratios, no light scattering, and unique mechanical properties in composite form—have led to use in dental fillings and crowns. Bone grafting, bone cement, and bioactive ceramic applications also offer research opportunities. Pawar expects future research in this area will focus on development of methods to produce customized nanoceramics based on patient needs.
In the last few weeks, GlaxoSmithKline finally (and relatively quietly) began the sale of its renowned Sensodyne Repair & Protect toothpaste in the United States, and if you think maybe I am going to write one of those good news/bad news stories, I am not. There is no good news here and I have scratched a bald spot in my wrinkled gray scalp over the past five days trying to make sense of GSK’s decision.
There are a lot of international readers of this blog, so some background is necessary to avoid confusion for those who live outside North America. For years, GSK has sold a unique and remarkable toothpaste outside North America called Sensodyne Repair & Protect. Materials scientists, particularly those that work with advanced glass materials, took interest in this Sensodyne product because it contained a form of the 45S5 Bioglass invented by Larry Hench. As far as I know, it was the first broad-based consumer product that contained a bioactive ingredient that was designed to stimulate the body to rebuild dental tissue that, heretofore, was not rebuildable.
Repair & Protect was reported to be a godsend to people (including most adults) whose teeth have become annoyingly sensitive to heat and cold. Typically, the sensitivity occurs as one ages because some of the tooth enamel gets worn off over the years, which exposes the dentinal tubules that connect with the tooth nerves.
The 45S5 glass particles in Repair & Protect solve this by triggering an ionic reaction. When the glass particles contact saliva and water, the glass releases calcium and phosphate ions that form a calcium phosphate layer. The body then converts this to hydroxyapatite, which creates a physical barrier over the tubules much like the original enamel. Brush twice a day with Repair & Protect and after two weeks the heat/cold sensitivity disappears.
Just for the record, it wasn’t a direct path from Hench’s lab to the innovative toothpaste. Hench licensed his 45S5 to a US startup company, NovaMin, created by a group of dentists who saw the enormous potential for the glass in dental applications. GSK also saw the enormous potential and bought NovaMin for $135 million three years ago.
Quickly, GSK started bringing Repair & Protect to markets in Europe, Asia, Australia, and South America, to name a few. Anecdotally, the product seems to have been well received by consumers (despite being priced at a premium) and dental professionals. I have not read any definitive reports on sales, but according to a December 2011 story on the Consumer Goods Technology website, “As of September 2011, GlaxoSmithKline had sold 20 million units of Sensodyne Repair & Protect in more than 30 international markets.” Not bad for a few months of sales.
And it got better. According to GSK’s 2011 Annual Report, its Sensodyne Sensitivity & Acid Erosion business “grew 16%, driven by the launch of Sensodyne Repair & Protect… . Since its launch in February 2011, Sensodyne Repair & Protect has been available in 30 markets across Europe, Asia and the Middle East, with 20 additional launches planned for 2012. The Sensodyne franchise has registered double-digit growth for 11 consecutive quarters.“
GSK’s 2012 Annual Report (pdf) makes it sound like the toothpaste quickly became one of its cash cows:
“The Oral care category led growth at 8% versus market growth of approximately 4%. Sensodyne became the business’s first ‘billion-dollar brand’ in 2012, boosted by the global roll-out of Sensodyne Repair & Protect and the launch of Sensodyne Repair & Protect Whitening and Extra Fresh.”
But, one of the obvious omissions, marketwise, was that GSK wouldn’t (or couldn’t) sell Repair & Protect in the US marketplace. The reason? Over the years I have spoken with several glass experts at various ACerS meetings and the story they gave was nearly always the same: GSK couldn’t get FDA approval. As recently as two months ago, I was told by someone involved with the product’s development—but not the FDA process—whose understanding was that US sales was delayed because the regulatory agency was fine with the toothpaste composition, but uneasy with the term “repair.” Regardless of the cause of the delay, you couldn’t buy similar Repair & Protect in the US. Even online outlets, such as Amazon, refused to ship the product to the US.
So far, I have been unable to confirm the story about the FDA delays, and I don’t know if there is any truth to it.
What I do know is true is that in the past three weeks, I suddenly starting hearing from friends and ACerS contacts that they either had seen Repair & Protect commercials on US networks or had seen an actual box of the product in US retail outlets. Great, I thought. No more having to sneak it into the US!
But, in fact, I still was a little skeptical because just a week or so ago, when he was receiving the Toledo Glass Award, Larry Hench stated something to the effect that Repair & Protect was unavailable in the US. Coincidentally, my colleague Eileen De Guire excitedly shot out an iPhone picture of a box of Repair & Protect that she just found in a drugstore in Michigan.
Weird, I thought. Then even my chiropractor on Monday mentioned to me that he had seen an ad for the toothpaste.
Curiosity fully piqued, I jumped online to look for GSK’s press release about the start of Repair and Protect sales in the US. There wasn’t one. I did look for the product on GSK’s website and was eventually directed to the US Sensodyne website. Indeed, the main story proclaimed, “Now a Sensodyne toothpaste that can actually repair sensitive teeth.” A-ha! It is true.
But… there was also button to click on to “Learn more about Repair & Protect.” I clicked hoping read carefully composed marketing copy about the benefits of the NovaMin/45S5 glass particles in Repair & Protect like that on the UK Sensodyne website.
Boy, was I disappointed. Instead of a discussion of NovaMin, the webpage discusses the benefits of stannous fluoride. Stannous fluoride! The webpage also has video from a dentist whose chopped up testimonial has him saying, “I’m always open to new advances…” Now, if you are old enough to remember the old “Crest with Fluoristan” commercials, you know that there is nothing “advanced” about stannous fluoride.
I was certain there was a mistake. I was so certain there was a mistake that I went out to my local CVS to buy a tube so I could read the ingredients myself. Sure enough, the only active ingredient is “stannous fluoride 0.454%.”
I should have been tipped off by the relatively quiet start of the sales of Repair & Protect in the US. Yes, GSK/Sensodyne is running TV ads in the US, but it defies logic that a major consumer product company rolls out a “billion-dollar” brand in a huge market without 1) a press release and press push, 2) social media promotions ($1 off coupon campaigns don’t count), 3) an education campaign aimed at dentists, and 4) some nearly-over-the-top promotional events. But, that is what it appears GSK is doing.
I twice requested an interview with a GSK representative to explain why GSK switched the formulation for the US version of Repair & Protect and why there was such a lackluster product rollout. GSK refused to provide an interview opportunity. Instead, I had to settle for an insipid exchange of emails with GSK’s media contact for North America consumer products, Deborah Bolding.
Bolding wrote to me, “Sensodyne Repair and Protect is a new product here in the US and does not contain NovaMin. The FDA approved the formulation. We work with regulatory authorities in each market on formulations for the specific product to be marketed and sold in that specific market. There are variances by market depending on the local regulatory body and other factors.”
When I asked for examples of other markets where Repair & Protect doesn’t contain 45S5/NovaMin, she didn’t respond other than to write, “As mentioned earlier, formulations vary by market because each market has its own regulatory authorities.”
When I requested that Bolding supply me contact information of the dentist featured in the testimonial video, Bolding responded, “I am pleased that I could address a number of your questions regarding Sensodyne Repair & Protect here in the US. Unfortunately, further comment will not be available on our strategy, rationale and future plans.”
So, advanced materials aficionados, I am sorry to conclude that if you want to buy Sensodyne Repair & Protect in the US, save your money and buy some Crest. If you want “real” Repair & Protect, you are still going to have to go abroad to buy it.
I am confident the story eventually will emerge about why GSK would invest $135 million in a US startup (NovaMin), but not leverage the technology to create a powerful product in the startup’s home nation—all at the risk of diluting and potentially damaging the Repair & Protect brand reputation outside the US. GSK is a publicly traded company, and maybe analysts and stockholders should start asking.
Morgan Advanced Materials announces that it will be showcasing a broad range of its products for the oil and gas production and exploration industries at the 2013 Offshore Technology Conference in Houston, Texas. Morgan will be displaying a wide range of products and solutions, including fire protection, brazed assemblies, piezoelectric ceramic components, CVD Diamond and DLC coatings, and carbon and silicon carbide seals and bearings. The group’s new FireMaster Rigid Enclosure System will be on display. The system uses high-efficiency insulation materials providing a robust, weather protective enclosure solution for all equipment requiring jet fire protection, especially those with very low critical temperature limits. Also on display will be a variety of materials ideal for ceramic liner sleeves in large diameter tubes used in downhole drilling. Morgan’s alumina and Halsic-R recrystallized silicon carbide materials are ideally suited for highly demanding and harsh wear applications. Halsic-R features high thermal conductivity, thermal shock resistance, and good mechanical strength at high temperatures. While Morgan’s Alsint 997 alumina material provides good mechanical strength and electrical resistivity, operates at high temperatures, and is resistant to chemical attack.
Did you choose a technical study or have you worked in the high-tech industry in Twente or abroad? Do not miss the event ‘High-tech future for women in Twente’ on Tuesday, May 14 in Rabotheater Hengelo, Netherlands. This special event is organized by high-tech companies PANalytical, DEMCON and Thales. It will be a day entirely devoted to the high-tech woman. Together we discuss the many opportunities and challenges we face in the technical world and it will be a day full of inspiring speakers, stimulating debates and surprising twists. Watch a short video of whom you might meet on May 14.
Resodyn Acoustic Mixers has announced the dates for a demonstrations of their line of innovative industrial mixers. Demonstration appointments are available from May 13 though 24 in Minnesota, Illinois, and Texas pharmaceutical, technical, research, and industrial corridors. Resodyn manufactures noninvasive mixers for processing and materials applications in both production and laboratory environments. Demonstrating substantively faster mixing times and exceptionally high levels quality and dispersion, Resodyn sales engineers’ appointments include on-site prrof of technology uses both generic and customer-supplied materials. Demonstration reservations can be made by emailing.
A bauxite processing facility picked Izory zirconia ceramic trunnion bushings for use in high-temperature trunnion mounted ball valves to improve their longevity. Two years ago, a Texas valve company contacted Refractron to discuss the possibility of making Izory ceramic bushings for high temperature trunnion mounted valves used in the processing of bauxite materials. This valve company manufactures a variety of valves for controlling various fluids in many severe service applications. The valves range in size from ½” to 60″ in diameter. Typical application industries are power generation, oil and gas, refining, chemicals, pulp and paper, gasification, synfuels, mining, steam, and more. For our client, the application required a trunnion bushing that could withstand continuous use at 1,200ºF. The application had very little thermal shock, but had consistent high temperatures. At 1,200ºF, trunnion bushings made of polymer-based materials fatigue and wear; metal trunnion bushings fatigue, corrode, and wear. When the bushings made of polymers and metals suffer failure, it reduces or even stops the ability to open and close the valve properly. This valve failure would cause delays in the manufacturing process, and has the potential to cause injury to people in the area if the valve would crack or break. Trunnion bushings made with Izory Zirconia ceramic have no issue handling the high temperature, corrosion, or wear. Also, the coefficient of thermal expansion of Izory Zirconia ceramic for the trunnion bushing was very close to the expansion rate of the metal trunnion and the mating metal valve housing.
DePuy Orthopedics Inc. announced that the FDA has granted premarket supplement approval for its Ceramax Total Hip System with Biolox delta ceramic-on-ceramic 36-mm large femoral head. According to a company press release, this premarket supplement approval for the 36-mm size follows the initial PMA approval of the Ceramax Hip 28-mm size in 2010. With the launch of the Ceramax System this summer, the company’s Pinnacle Acetabular Cup System will offer the only FDA approved ceramic-on-ceramic bearing surface with Biolox delta femoral head, a next generation nanocomposite ceramic material with high strength and toughness. The Ceramax Hip System expands the Pinnacle Hip Solutions portfolio of high performance instruments, advanced implants, materials and solutions designed to provide surgeons flexibility in techniques and procedures and provide pain relief and a smooth range of motion for patients. In a clinical study of 264 patients who required hip replacement surgery for non-inflammatory degenerative joint disease, the researchers found no significant differences between the Ceramax System to a ceramic-on-polyethylene hip replacement in adverse events or survivorship. Patients also had similar pain relief and improved function and range of motion.
Further to its announcement on April 30, 2013, Ceramic Fuel Cells Ltd., a developer of generators that use fuel-cell technology to convert natural gas into electricity and heat for homes and other buildings, has announced that it has conditionally raised £5.0 million (A$7.6 million). The company has conditionally raised £4.3 million (A$6.5 million) through the issue of secured convertible loan notes to a number of institutional investors and a further £0.7 million (A$1.1 million) through the placing of 32,710,300 new ordinary shares of nil par value in the company. Commenting on the fund raising, CEO Bob Kennett says, “Having proved the commercialization of our technology we are now rapidly moving towards a major increase in the volumes sold by the company. This fund raise will allow us to meet the working capital requirements of the initial phase of this ramp up and the Board considers that it would be in the best interests of shareholders to raise these funds in this manner to allow the company to take advantage of these opportunities.”
(The Express-Times) An officials with Essroc Cement says the company will comply with stricter environmental regulations by 2015. Delaying new federal environmental regulations on the US cement industry by two years will lead to increased health risks and missed work days due to sickness, environmentalists say. But, imposing those regulations immediately would cripple the cement industry and could cost jobs across the country and in the Lehigh Valley at three local plants, according to at least one lawmaker. The updated rules change the monitoring method and limits for particulate matter: a mixture of extremely small particles and droplets, according to the Environmental Protection Agency. The new requirements dramatically reduce the emission of mercury, acid gases, particulate matter and total hydrocarbons from existing cement kilns across the country and ensure that emissions from new kilns remain low, says EPA spokeswoman Enesta Jones. The EPA won’t impose the restrictions until 2015 to allow some companies more time to reevaluate their emissions control strategies, Jones says.Cement plant grows greener to be of service
(KnoxvilleBiz.com) At the Cemex cement plant in Knoxville, what became a robust sustainability initiative and trend-setting conservation program began simply as an effort to be of service. ”Back then, it was an effort to be supportive of the community,” says Antonio DeLuca, the local plant manager. By “back then,” DeLuca means 15 years ago, before many local companies were thinking green. In the late 1990s, as communities were searching for an alternative way to dispose of tires in lieu of open burning and dumping, the Environmental Protection Agency asked Cemex to help investigate a solution. The cement-making process involves a large kiln in which rock mined for the purpose undergoes a thermal reaction process. Fired largely with fossil fuels, Cemex developed a process that utilizes tires. A resulting solid byproduct is also used as an ingredient in the cement. Cemex has burned 986,000 tires since 2010, contributing to a 9 percent reduction in the plant’s fossil fuel requirements. And, company executives continue to seek to turn waste into energy. At a sister plant in Georgia, peanut and pistachio shells provide 100 percent of the fuel for its thermal process. Tests are now underway to determine what type of waste stream might be viable in East Tennessee. One experiment, for example, used discarded items from the recycling sorting process.
Chemical engineering researchers have identified a new mechanism to convert natural gas into energy up to 70 times faster, while effectively capturing the greenhouse gas carbon dioxide. “This could make power generation from natural gas both cleaner and more efficient,” says Fanxing Li, coauthor of a paper on the research and an assistant professor of chemical and biomolecular engineering at North Carolina State University. At issue is a process called chemical looping, in which a solid, oxygen-laden material—called an “oxygen carrier”—is put in contact with natural gas. The oxygen atoms in the oxygen carrier interact with the natural gas, causing combustion that produces energy. Previous state-of-the-art oxygen carriers were made from a composite of inert ceramic material and metal oxides. But Li’s team has developed a new type of oxygen carrier that include a “mixed ionic-electronic conductor,” which effectively shuttles oxygen atoms into the natural gas very efficiently—making the chemical looping combustion process as much as 70 times faster. This mixed conductor material is held in a nanoscale matrix with an iron oxide. The oxide serves as a source of oxygen for the mixed conductor to shuttle out into the natural gas. In addition to energy, the combustion process produces water vapor and CO2. By condensing out the water vapor, researchers are able to create a stream of concentrated CO2 to be captured for sequestration.
Over 20 million people in Europe suffer from osteoarthritis, which can lead to extensive damage to the knee and hip cartilage. Stem cells offer a promising way forward but a key challenge has been to design a ’smart material’ that is biologically effective for cartilage tissue regeneration. Now researchers have identified a blend of naturally occurring fibers such as cellulose and silk that makes progress towards affordable and effective cell-based therapy for cartilage repair a step closer. The EPSRC-funded study, published in Biomacromolecules and undertaken by University of Bristol (UK) researchers, explored the feasibility of using natural fibers such as silk and cellulose as stem cell scaffolds—the matrix to which stem cells can cling to as they grow. Both cellulose and silk are commonly used in textiles but the researchers demonstrated an unexpected use for the two natural polymers when mixed with stem cells. The team treated blends of silk and cellulose for use as a tiny scaffold that allows adult connective tissue stem cells to form into preliminary form of chondrocytes—the cells that make healthy tissue cartilage - and secrete extracellular matrix similar to natural cartilage. Wael Kafienah, lead author from the University’s School of Cellular and Molecular Medicine, says, “We were surprised with this finding, the blend seems to provide complex chemical and mechanical cues that induce stem cell differentiation into preliminary form of chondrocytes without need for biochemical induction using expensive soluble differentiation factors. This new blend can cut the cost for health providers and makes progress towards effective cell-based therapy for cartilage repair a step closer.”
Researchers from Ulsan National Institute of Science and Technology (UNIST) demonstrated high-performance polymer solar cells (PSCs) with power conversion efficiency (PCE) of 8.92 percent, which are the highest values reported to date for plasmonic PSCs using metal nanoparticles (NPs). Compared to silicon-based devices, PSCs are lightweight (which is important for small autonomous sensors), solution processability (potentially disposable), inexpensive to fabricate (sometimes using printed electronics), flexible, and customizable on the molecular level, and they have lower potential for negative environmental impact. Polymer solar cells have attracted a lot of interest due to these many advantages. Although these many advantages, PSCs currently suffer from a lack of enough efficiency for large scale applications and stability problems but their promise of extremely cheap production and eventually high efficiency values has led them to be one of the most popular fields in solar cell research. The research team employed the surface plasmon resonance effect via multi-positional silica-coated silver NPs to increase light absorption.
Preterm infants appear to mature better if they are shielded from most wavelengths of visible light, from violet to orange. But it has been a challenge to develop a controllable light filter for preterm incubators that can switch between blocking out all light—for sleeping—and all but red light to allows medical staff and parents to check up on the kids when they’re awake. Now, in a paper accepted for publication in Applied Physics Letters, researchers describe a proof-of-concept mirror that switches between reflective and red-transparent states when a small voltage is applied. The research team had previously identified a magnesium-iridium reflective thin film that transforms into a red-transparent state when it incorporates protons. Providing those protons in a way that is practical for preterm incubators, however, was the challenge. The typical method—using dilute hydrogen gas—is unacceptable in a hospital setting. So the team created a stack of thin films that includes both an ion storage layer and the magnesium-iridium layer: a voltage drives protons from the ion storage layer to the magnesium-iridium layer, transforming it into its red-transparent state. Reversing the voltage transforms it back into a reflective mirror. The researchers report that the device still allows some undesirable light wavelengths through, but a force of just 5 volts changes the device’s state in as little as 10 seconds. The researchers are now looking at other materials to improve color filtering and switching speed.
Simpleware, a company set up to commercialize EPSRC-supported research at the University of Exeter, has won The Queen’s Award for Enterprise in the International Trade Category. Founded in 2003 by Philippe Young, the company’s pioneering software converts 3D image data into high-quality computer models used for engineering design and simulation. The technology has been applied across a host of disciplines and industries—from mobile phones to car engines; asphalt damage to back pain, contact lenses to hearing aids. The software is underpinned by patented techniques developed and improved with the aid of EPSRC funding to produce a previously unattainable level of realism in 3D simulations. Since 2008, Simpleware’s exports have seen an overseas sales growth of 690 percent. The company’s global export markets include the United States, Germany, Japan, France, China, Australia, Canada and other EU countries. Strong re-selling networks are also being established in India, Taiwan, and Singapore. The majority of sales are to blue-chip companies, research institutes and universities world-wide, including NASA and the Naval Research Laboratory. Young says, “The ability to generate robust and accurate numerical models from various sources of image data has started a revolution in the world of multi-physics simulation.
University of Illinois researchers have developed a new way to produce highly uniform nanocrystals used for both fundamental and applied nanotechnology projects. “We have developed a unique approach for the synthesis of highly uniform icosahedral nanoparticles made of platinum,” explains Hong Yang, a professor of chemical and biomolecular engineering and a faculty affiliate at the Center for Nanoscale Science and Technology at Illinois. “This is important both in fundamental studies-nanoscience and nanotechnology-and in applied sciences such as high performance fuel cell catalysts. Yang’s research group focuses on the synthesis and understanding structure-property relationship of nanostructured materials for applications in energy, catalysis, and biotechnology. “Although polyhedral nanostructures, such as a cube, tetrahedron, octahedron, cuboctahedron, and even icosahedron, have been synthesized for several noble metals, uniform Pt icosahedra do not form readily and are rarely made,” states Wei Zhou, a visiting scholar with Yang’s research group. An icosahedron crystal is a polyhedron with 20 identical equilateral triangular faces, 30 edges and 12 vertices. According to Yang, icosahedral shaped crystals can improve the catalytic activity in oxygen reduction reaction partly because of the surface strain. “The key reaction step to improve the activity of oxygen electrode catalysts in the hydrogen fuel cell is to optimize the bond strength between Pt and absorbed oxygen-containing intermediate species,” Yang says. “This allows the rapid production of water and let the intermediate react and leave the surface quickly so the catalyst site can be used again.”
A team led by Professor Keon Jae Lee from the Department of Materials Science and Engineering at KAIST has developed in vivo silicon-based flexible large-scale integrated circuits (LSI) for biomedical wireless communication. Silicon-based semiconductors have played significant roles in signal processing, nerve stimulation, memory storage, and wireless communication in implantable electronics. However, the rigid and bulky LSI chips have limited uses in in vivo devices due to incongruent contact with the curvilinear surfaces of human organs. Although several research teams have fabricated flexible integrated circuits (ICs, tens of interconnected transistors) on plastics, their inaccurate nanoscale alignment on plastics has restricted the demonstration of flexible nanotransistors and their large-scale interconnection for in vivo LSI applications such as main process unit, high-density memory and wireless communication. Professor Keon Jae Lee’s team fabricated radio frequency integrated circuits interconnected with thousand nanotransistors on silicon wafer by state-of-the-art CMOS process, and then they removed the entire bottom substrate except top 100 nm active circuit layer by wet chemical etching.
One of the holy grails in tissue engineering is developing scaffolds that will support robust vascular growth. Apropos to Eileen’s earlier story about a new award for Larry Hench, a research group with members from the University of Erlangen-Nuremberg and Imperial College London has, for the first time demonstrated that a type of bioactive scaffold based on 45S5 Bioglass just might be able to foster the right type of vascularization that surgeons are looking for in implant design.
By way of background, it might first be worth looking at the just-published interview I did with Hench, the Bioglass inventor. In this Bulletin article, Hench describes the emergence of what he call the “third generation” of biomedical glasses and other bioceramics, which are defined by their ability to achieve a controlled release of biological stimuli that triggers the body’s intrinsic repair mechanisms.
The composition of Bioglass often appears to have this third-generation ability, and the new research I mentioned above, published in Tissue Engineering C (doi:0.1089/ten.tec.2012.0572), is an important new example. The goal of the study was to investigate—in cooperation with Dr. Raymund E. Horch, head of the Department of Plastic and Hand Surgery in Erlangen and Dr. Andreas Arkudas, from the same department—the angiogenic effects of bioactive glass in a relevant in vivo model.
In brief, the group tested the scaffold and grew tissue using an arteriovenous loop (AVL) model in rats. An AV loop is a commonly used hybrid blood vessel, formed via microsurgery, which joins a small arterial vessel with a vein counterpart. The AVL stays connected to the animal.
The researchers made the scaffolds by first using 45S5 Bioglass powder and applying a foam replica technique developed by the group of Aldo R. Boccaccini, an ACerS Fellow and head of the Institute of Biomaterials in Erlangen. They then filled this Bioglass-derived granular matrix with fibrin gel. Finally, they placed the scaffold in a small Teflon isolation chamber containing the AVL. They left the AVL–Teflon isolation chamber in the rats, which, they say, tolerated the material well.
After about three weeks, they removed the isolation chamber from the rats and examined the resultant combination of scaffold and newly grown tissue using microcomputed tomography and histology. To their delight, they found extensive axial vascularization of the matrix, confirming the significant potential of the material in tissue engineering applications. Furthermore, because other research has shown that the presence of Bioglass generally can have a positive effect on the growth of new bone tissue, this in vivo study, in particular, suggests that it should be possible to use the 45S5 for the development of vascularized bone tissue.
The fact that the group found axial vascularization shouldn’t be missed. This is a key finding that allows the microsurgical transfer of the biomaterial independent of local conditions at the recipient site. In addition, they found that the newly grown microvessels were immature and had consistent, small diameters, meaning that they would be prime for continued growth once implantation occurs. Implantation could occur as easily as transplanting the entire AVL pedicle to another site where, for example, bone or another type of tissue repair is needed.
The hope is that this technique, or one similar, could be used to engineer tissue to address large-bone defects and eventually replace the practice of harvesting bone graft material from, for example, a patient’s pelvis, a method that often causes additional and serious medical complications.