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Scanning electron microscope image of a bioactive glass scaffold seeded with human osteoblasts (MG-63). The seeded cells are distributed over the whole scaffold area and well adhered on the surface. This image shows that bone cells can grow on and through this bioactive glass construct. Credit: Boccaccini; Uni-Erlangen.

Following last year’s successful Pacific Rim Engineering Ceramics Summit, The ACerS Engineering Ceramics Division has organized a transatlantic European Union-USA Ceramics Summit for the upcoming 36th International Conference on Advanced Ceramics and Composites (36th ICACC), Jan. 22-27, 2012 in Daytona Beach, Florida.

According to organizers of the summit, there has been major progress in the R&D and commercialization of engineered ceramics over the last 50 years in Europe and the US. Seminal contributions have led to the engineering of ceramics with multifunctional properties and broad applications in energy, aerospace, healthcare, communication, infrastructure, transportation, environmental, and other industries. As a result, the living standards and quality of life have been raised for people worldwide.

The goal of the EU-USA Summit is to provide a forum for the information exchange on current status and emerging trends in innovative ceramic technologies and to identify strategic elements and new materials technology pathways for a sustainable future.

The session runs Monday afternoon and all day Tuesday (Jan. 23-24) in Coquina Salon F (Hilton). Two of the 25 presentations from this Summit are highlighted below.

“Innovations in bioactive ceramics and glasses for tissue engineering, drug delivery and regenerative medicine”
Speaker, Aldo Boccaccini, University of Erlangen-Nuremberg, Germany

Abstract: Beyond the well-established and expanding applications of bioceramics in medicine, e.g. as permanent implants and bioactive coatings, there is increasing interest in developing bioactive ceramics and glasses and their composites with biodegradable polymers, for applications in the fields of tissue engineering and drug delivery. Specific innovations involving the design and fabrication of multifunctional scaffolds that combine a variety of biodegradable polymers, signaling molecules, therapeutic drugs and bioactive ceramics will be presented. In this context, significant efforts are being devoted to investigating the effect of the dissolution products of bioactive glasses, both silicate and phosphate glasses, on cellular response, which includes understanding the effect of specific metallic ions (bioinorganics) on osteogenesis and angiogenesis during bone formation, both in vitro and in vivo. In addition, gaining further understanding of the antibacterial effect of specific ions released from bioactive glasses for combating infections more effectively is of particular interest. Specific research areas attracting large research efforts will be presented and promising avenues for future research activities will be discussed, highlighting the current needs and challenges for improving the overall performance of bioactive ceramics in tissue engineering and drug delivery.

“New ceramic membranes for energy- and environmental applications”
Speaker: Alexander Michaelis, Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Germany

Abstract: Ceramic membranes are well established for micro-, ultra- or nano- filtration applications such as waste water purification. Further innovations require an improved control and reduction of pore size. This allows for new applications in gas separation and pervaporation systems. For this, pores sizes below 1 nm have to be generated using specific structural features of selected materials. Several new methods for preparation of such membranes are presented. In a first example we use the well know crystallographic cage structure of zeolites. Employing a new hydrothermal route allows for synthesis of dense zeolite films on porous substrates. It is shown that these membranes can be used for dewatering of bioethanol. In a further example we use carbon layers with well-defined lattice distances of 0.35 nm as a membrane for separation of hydrogen from gas mixtures. By further chemical modification of these carbon layers a well-designed adsorption selective behavior can be achieved as is demonstrated with membranes for purification of biogas. As a last example we present perovskite materials showing mixed conducting behavior. Due to an oxygen vacancy structure in the crystal lattice these materials can be used to generate oxygen which in turn can be used to improve the efficiency of combustion processes. Besides an improved energy balance in the combustion process this leads to reduction of CO2 emissions.

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Professor Susmita Bose uses 3D printing to make bone-like scaffolds from tricalcium phosphate. Credit: Washington State University; YouTube.

We’ve written several posts recently on additive manufacturing of ceramics for heavy manufacturing (investment casting molds) and artistic designs (espresso coffee cups). New work by a Washington State University group further demonstrates the utility of rapid manufacturing techniques for fabricating bone-like scaffolds that could make it possible for surgeons to order custom engineered bone tissue one day.

Professor Susmita Bose’s group uses a commercial printer to build tricalcium phosphate parts with interconnecting porosity. According to the press release, “Paired with actual bone, it acts as a scaffold for new bone to grow on and ultimately dissolves with no apparent ill effects.”

In their paper, the group reports on the effects of doping the TCP with silica and zinc oxide in the amounts of 0.5 wt. percent and 0.25 wt. percent, respectively. The doped-composition scaffolds were more dense than the undoped by a few percent (~94 percent vs. ~91 percent dense). The dopants also slowed down the beta to alpha phase transformation, which more than doubled the compressive strength after sintering.

In vitro tests showed that the doped scaffolds “facilitated faster cell proliferation when compared to pure TCP scaffolds.”

In the YouTube video, Bose says “The way I envision it is, ten to twenty years down the line, physicians and surgeons, should be able to use this type of scaffold—bone scaffolds—along with some bone growth factors… for different types of bone disorder fixation.”

The paper is “Effects of silica and zinc oxide doping on mechanical and biological properties of 3D printed tricalcium phosphate tissue engineering scaffolds,” Gary A. Fielding, Amit Bandyopadhyay, Susmita Bose, Dental Materials (doi:10.1016/j.dental.2011.09.01)

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Mathematics—the common language of science and engineering—often proves to be the doorway between disciplines. The common ground between a skyscraper, an airplane wing, and facial bones may not seem obvious until one realizes that from a structural perspective, they are all framework systems that must support and transmit loads within certain constraints. By breaking a structure into trusses, nodes, forces, etc., the mathematics transcends the application, and modeling principles can be applied broadly.

A story on the NSF website describes a study that demonstrates the use of topological optimization to “engineer” new faces when facial bones are destroyed by severe injury or disease. The standard surgical approach to craniofacial repair has been to take part of a larger bone from the patient and sculpt it to shape for implantation, an imperfect approach that may leave the patient improved but still significantly deformed.

“The middle of the face is the most complicated part of the human skeleton. What makes the reconstruction more complicated is the fact that the bones are small, delicate, highly specialized and located in a region highly susceptible to contamination by bacteria,” says Glaucio Paulino in the story. Paulino is program director of the mechanics of materials program at the NSF, professor of civil and environmental engineering at the University of Illinois, Urbana-Champaign and one of the PIs on the study.

Topological optimization takes into account limiting factors, such as available space, applied force, load and layout constraints. From the story, “Imagine a building grid in which you can determine where there should be material and where there shouldn’t. Moreover, you can express loads and supports that would affect certain parts of this block of material. Your final result is an optimized structure that fits your established constraints.”

In a PNAS paper (pdf) published in 2010, Paulino and his colleagues from Ohio State University’s School of Medicine demonstrated the feasibility of using the method to custom design a bone replacement for a massive facial injury. In the conclusions of the paper, they also note that the computational algorithms can be expanded to include other critical variables like oxygen levels, surgical flaps, aesthetics and even cost.

(This fascinating 40-second video shows the transformation of a block into a complex upper jaw prosthesis.)

This approach to designing the prosthetic’s structure dovetails very nicely with work already being done in the materials community on additive manufacturing and laser-based manufacturing fabrication of surgical implants.

At the Fraunhofer Institute in Germany, studies are showing that selective laser melting can be used to fabricate a porous polylactide-tricalcium phosphate composite that the body absorbs as natural bone grows into the scaffold. Structures have been assembled that can close openings of up to 25 cm. Selective laser melting is an additive manufacturing process that uses three dimensional CAD renderings to guide a laser beam through a powder bed to melt powders into a dense component.

The Roger Narayan group at the combined UNC-NC State biomedical engineering department is using two-photon polymerization to synthesize polymeric and zirconia shapes for medical applications. Two-photon polymerization uses laser radiation to initiate chemical reactions, polymerization and hardening of a material to build submicrometer structures.

There are commercial examples, too, of rapid prototyping fabrication of customized surgical implants. TMJ Concepts manufactures temporomandibular joint prostheses from titanium using computer numerical control machining based on patient CAT scans.

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A bone allograft being placed into position.

The University of the Basque Country (Universidad del País Vasco) reports that one of its Ph.D. students has developed a new porous, biodegradable nanocompound support for the regeneration of bone tissue. According to UPV, Beatriz Olalde, in her doctoral thesis, reported on her approach that combines polylactic acid, hydroxyapatite and carbon nanotubes to form a material that could be used instead of bone grafts. Her material interacts chemically and electrically with bone cells and adjoining tissue to speed bone replacement and recovery.

Beatriz Olalde

Each of the components in Olalde’s foam-like material plays a specific role. The polylactic acid forms a basic biodegradable scaffold. Hydroxyapatite – a benign, bone-like bioceramic substance that is very compatible with tissues – is added attract cell growth and provide a source of calcium. The CNTs are added to provide strength. The CNTs also provide a material that reacts with an external electric field in a way that stimulates cell growth.

The desire for materials like Olalde’s (alloplastic grafts) stems from problems the medical profession faces when, due to events like large scale physical trauma or tumor removal, a patient loses a significant section of bone. Bone has the ability to regenerate itself to a large extent, but that requires time and support for the injured area.

Typically, bone grafts have been used either from the patient (an autograft), a living donor or a cadaver (allografts). But often a patient isn’t capable of providing the graft and donated bone raises complications due to tissue rejection issues, contamination, etc.

According to Olalde, trials involving both in vitro and in vivo experiments have shown satisfactory results. She says the foam displayed good mechanical properties and bone support. In in vivo trials, bone growth was observed after three weeks, and after 16 weeks this new bone showed mechanical, histomorphometric and densitometric properties similar to those of intact, healthy bone tissue.

Olalde has published before about polylactic acid and carbon nanotubes, and has collaborated with the University of Aberdeen, Scotland, and the Institute of Biomechanics of Valencia (IBV). She was awarded her Ph.D. and is currently working as a researcher in the Department of Biomaterials and Nanotechnologies Unit Tecnalia Health.

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ACerS Fellow Prashant Kumta has been a pioneer in the use of nanoceramic materials for bone regeneration and to bind and transport proteins and protein-like substances into cells. Kumta, who teaches at both Carnegie Mellon University and the University of Pittsburgh’s Schools of Engineering and Dental Medicine, discusses how his interest in bioglass and bioceramics coincided with the explosion of nanotechology, opening up new opportunities for biocompatible materials that could be slowly absorbed by the body.

9 minutes.

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