David Itzhak

Hard tissue remodeling using biofabricated coralline biomaterials.

Biotechnical and biomedical approaches were combined in an attempt to identify potential uses of biofabricated marine carbonate materials in biomedical applications, particularly as biomatrices for remodeling bone and cartilage tissue. After grafting, it is desirable for bone ingrowth to proceed as quickly as possible because the strength of the implanted region depends on a good mechanical bond forming between the implant and surrounding regions in the body. Ingrowth can take place as a result of growth of tissue and cells into the implanted porous material, or it may be promoted by transplanting cells seeded onto such a material. The rate at which ingrowth occurs is dependent on many factors, including pore size and the interconnectivity of the implanted structure. In vivo graftings into osteochondral defects demonstrated that our biofabricated porous material is highly biocompatible with cartilage and bone tissue. The biofabricated matrix was well incorporated into the biphasic osteochondral area. Resorption was followed by bone and cartilage formation, and after 4 months, the biomaterial had been replaced by new tissue. Ossification was induced and enhanced without introduction of additional factors. We believe that this is the first time that such biofabricated materials have been used for biomedical purposes. In face of the obvious environmental disadvantages of harvesting from limited natural resources, we propose the use of bioengineered coralline and other materials such as those cultured by our group under field and laboratory conditions as a possible biomatrix for hard tissue remodeling.

Crystal structure of Nd2- xMxRu2O7- y (M=Cu, Ag) pyrochlores by X-ray powder diffraction

The crystal structures of ruthenium oxides with the general formula Nd 2− x M x Ru 2 O 7− y , where M is Cu or Ag, 0≤ x ≤0.25, were investigated. All compounds that were prepared exhibit the pyrochlore structure with a cubic unit cell. The compounds were characterized by X-ray powder diffraction, and single-phase structures were found for Nd 2− x Cu x Ru 2 O 7− y , x =0.1, 0.2, 0.25, and for Nd 2− x Ag x Ru 2 O 7− y , x =0.1, 0.15, 0.2. The relative metal concentrations were verified by EDS. The cell parameters were determined by advanced peak-position analysis and calibrated by a Si internal standard. Atomic positions and oxygen occupancies where refined by the Rietveld method. It was found that the cell-size modifications agree with the relations between ionic sizes.

Interaction Between Various Metals and the Hydrozoan Millepora Dichotoma in a Coral-Reef Environment

Small fragments of the hydrocoral, Millepora dichotoma, were glued to PVC racks containing three different types of metals. The following groups of metals were deployed: electrochemically passive metals UNS S30403, UNS S31603, UNS S31254, UNS R50400, UNS R52400, UNS R53400 and UNS Ν10276; electrochemically active metal with no harmful biological effect St-37 mild steel; mi tals with biocidic effect commercial copper and bras 30/70. The samples w.,re immersed in the coral reef environment, at 6 meters depth for a period of 3 months, between May-August 2000. An adhesive two-dimensional growth of the M. dichotoma encrustation layer on the metal surface was clearly observed in all the electrochemically passive metals. No two-dimensional development of the hydrocoral was observed on the mild steel. The tips attached to the plates of commercial copper and brass 3o/70 were damaged and died within three weeks.