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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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Credit: Fraunhofer ILT

Researchers at Fraunhofer’s Institute for Laser Technology say they are getting excellent results from a bone replacement system that uses a paste of polyactide (PLA) and tricalcium phosphate that is melted by a fine laser to build up layers of material that can provide a strong and precise fit.

This new approach was developed under the aegis of federal ministry “Resobone” project in Germany.

Researchers say the laser-treated paste develops precise microchannels in the PLA, creating a lattice structure which the adjacent bones can grow into. “Its precision fit and perfect porous structure, combined with the new biomaterial, promise a total bone reconstruction that was hitherto impossible to achieve,” says Ralf Smeets of the University Medical Center of Aachen.

Both PLA and TCP are tolerated well by the body. Many consumers have unknowingly run into PLA, the major component of biodegradable packaging material and clear disposable cups that are becoming commonplace. While the PLA provides the framework, the TCP resides in more or less a granular form in it and acts as a stimulus for bone growth. The body can catabolize both substances as natural bone grows through the lattice.

Fraunhofer says the PLA/TCP Resobone system isn’t really suitable for bones that experience high stress, such as in limbs or joints. Instead, it is ideal for certain low-stress bony areas such as cranial, facial and maxillary bones. For example, a five-centimeter large replacement piece of cranium can be completed in an overnight process that uses data from CT imaging to guide a thin laser beam to melt the PLA/TCP mix layer by layer. The precise, customize-sized implants that results from this “Selective Laser Melting” process can be as thin as 80 micrometers and as large as 25 square centimeters.

Fraunhofer gives much of the credit for developing the manufacturing process to its Institute for Laser Technology in Aachen.

“No custom-fit, degradable implants ever existed before now. During the operation, the surgeon had to cut TCP cubes, or the patient‘s own previously removed bone material, to size and insert it into the fissure,” explains Simon Höges, project manager at ILT. “We have achieved our project goal: a closed process chain to produce individual bony implants from degradable materials.

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Osteoblasts forming compact bone. Credit: Robert M. Hunt

Apropos to the new MS&T symposium on materials and the effects of electric and magnetic fields, I received a notice that there will be a paper presented tomorrow (March 17) at the annual meeting of the American Physical Society the explores possible routes for improving bone growth, grafts and implants, and looks at the role these fields could play. Yizhi Meng of Stony Brook University and her colleagues have been studying the very early stages of bone formation. Here is the abstract to her paper:

The induction of bone formation to an intentional orientation is a potentially viable clinical treatment for bone regeneration. Among the many chemical and physical factors, electric and magnetic fields are an essential way to regulate the behavior of cells and matrix fibers. The aims of this study are to investigate the effects of electric and magnetic fields on protein self-organization and osteoblast biomineralization on polymer surfaces in vitro. To this end, we use atomic force microscopy to characterize the morphology of protein fiber and ECM by cells. The mechanical property of protein fibers was investigated by shear modulation force microscopy. The late-stage of mineralization was characterized by scanning electron microscopy and grazing incident x-ray diffraction. The primary data indicated that the magnetic field could enhance the biomineralization of osteoblast.

Meng is actually presenting a series of papers at the meeting regarding bone growth, formation of calcium phosphate and biomineralization.

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Lehigh University professor Himanshu Jain discusses the school’s work to lead an international effort to develop biocompatible, dually porous glass that helps damaged human bone to regenerate. Jain, who teaches in the Department of Materials Science and Engineering, was the subject of another post we did about a week ago concerning a project to encourage more African-Americans to adopt science and engineering careers.

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