Key Engineering Materials Vols. 361-363

Abstract: Magnetite nanoparticles were used for their ability to be heated when they are put in an oscillating magnetic field. When they are located inside tumors they can eradicate the tumor cells by heating. We have developed a biomaterial constituted by a mineral degradable matrix containing magnetite nanoparticles. This material can be injected into bone metastasis in which it sets and releases magnetite particles uptaked inside the cancer cells. We have implanted this material inside rabbit bone to check by histology the fate of the nanoparticles in bone. The implant matrix was degraded within a few days releasing the nanoparticles. They were found inside monocytes and fibroblasts having ingrown the material. The nanoparticles could form aggregates which then were fragmented in micro/nanoparticles penetrating the surrounding cells. This study showed that the nanoparticles are released from the mineral matrix within a few days and penetrate the cells in their close proximity.

Abstract: Porous chitosan-silicate hybrids were prepared by freeze-drying the precursor sol solutions synthesized from chitosan and 3-glycidoxypropyltrimethoxysilane (GPTMS). Degradability of and the release of cytochrome C in to phosphate buffer saline solution (PBS) were examined as a function of the GPTMS content. The hybrids were less degradable with larger GPTMS contents, and the cytochrome C release profile was so controllable as to give either burst release or slow one due to the GPTMS content. Thus, the present porous chitosan-silicate hybrids were considered applicable to drug delivery systems.

Abstract: Nano-materials and technology increasingly come under emphasis on application in biomedical treatment and pharmaceutical field. Drug particle with nano-size has better bioactivity and absorptivity, which advance the efficiency of utilization. The nanoporous alumina membranes fabricated by anodization are provided with orderd nanoporous structure, highly uniform pore size, straight and parallel pore channels, moreover, this material possesses favorable biocompatibility. Recently, application of nanoporous alumina membranes in medical science has becoming public concerned in present biomedical material field. Our experiment aimed at fabricating nanoporous alumina membranes with definite mechanical strength to cylindrical biofiltration capsules, which can be used to encapsulate nanodrug to control drug delivery. The release characteristic was examined by monitoring the diffusion of fluorescein isothocyanate (FITC) with molecular weight of 389.4Da as a function of time after encapsulation within the alumina tubes.

Abstract: Our previous studies showed that synthetic octacalcium phosphate (OCP) enhances bone regeneration more than hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP). Also, a synthetic bone substitute constructed of synthetic octacalcium phosphate (OCP) and porcine atelocollagen sponge (OCP/Col) showed stable bone regeneration. The present study was designed to investigate the difference of bone regeneration by OCP/Col and other calcium phosphate-collagen composites. OCP/Col, β-TCP$-collagen% composite (β-TCP/Col), or HA$-collagen% composite (HA/Col) sponge was prepared from pepsin-digested atelocollagen isolated from the porcine dermis and OCP, β-TCP, or HA granules, respectively. A standardized critical-sized defect was made in the rat calvarium, and various calcium phosphate-collagen composites were implanted into the defect. The rats were fixed at four weeks after implantation and radiographic and histological examinations were performed by undecalcified cross sections of implants. Radiographic examination showed that uniform radiopaque masses were observed in the created defects treated with OCP/Col, whereas granulous and foggy radiopacity was observed in β-TCP/Col and HA/Col. Histological examination showed that newly formed bone was observed in the reticulum of OCP/Col and around the implanted OCP. The regenerated bone by β-TCP/Col or HA/Col seemed to be less than that by OCP/Col and would not to be nucleated by the granules of β-TCP or HA. The present study indicated that bone regeneration by OCP/Col was different from those of β-TCP/Col and HA/Col. Application of OCP/Col would be expected for clinical use in the future.

Abstract: Microporosity and granules size are important parameters for the development of suspension, composites and injectable bone substitutes. In this experimental study performed in a rat bone model of critical size defects, were have determined the kinetics of bioceramic resorption and bone ingrowth. Two kinds of granules (1mm in diameter) of Biphasic Calcium Phosphate BCP (60/40 HA/TCP ratio) with 20% and 40% microporosity of less of 5 microns in size, were used. Higher bone ingrowth was observed for low porosity (LP) at 3 weeks versus high porosity (HP); the contrary was measured after 6 weeks. About the kinetics of BCP resorption, significant difference between the 2 porosities was noticed, the higher for high microporosity. High porosity on time, promotes more bone ingrowth at the expense of the bioceramic than lower microporosity.

Abstract: Apatite/β−TCP particles exhibiting non-conventional urchin-like morphology were prepared by hydrothermal synthesis. Their implantation in the rat calvarium was followed during 60 days. A total absence of osteoconduction was observed despite a favorable chemical composition, stressing the fundamental role of particle morphology on bone regeneration. Results are discussed in relation with other literature data. Possible explanations include the disfavored accumulation of biological mediators due to the acicular shape of the particles and/or a limited accessibility for cells.

Abstract: The aim of this study was to study bone marrow quality from various location and species for reconstruction of segmental critical size defect in irradiated weigh bearing bone. Sample of bone marrow aspirates from rabbits and Beagle dog were analyzed. Rabbits were implanted with a composite associating resorbable collagen membrane plus micro macroporous biphasic calcium phosphate (MBCP®) and autologous bone marrow (BM) injected after irradiation. Bone marrow samples were found to be significantly less rich in tibia than in humerus and ilium in Dog and less rich in Dog than in Rabbit (p<0,05). Successful osseous colonization bridging of the defect were obtain at 16 weeks in all animals. Identical repartition of bone ingrowth and residual ceramic at the different levels of the implant suggest an osteoinduction role of the bone marrow graft in the center of the defect. This model succeeded in reconstruct a large segmental defect in weight bearing and irradiated bone in rabbit.

Abstract: To clarify new bone tissues, radiography with a newly developed tunable wavelength and highly parallel Parametric X-ray, PXR, was applied. Methods: PXR was generated by a LINAC at LEBRA, Nihon University (Hayakawa et al., 2005). X-ray wavelength was tuned from 7 KeV, 0.177 nm, to 16 KeV, 0.0775 nm. Coated or grit-blasted Ti-alloy implants modified with coating or blasting were implanted in surgically created defects in rabbit tibia. Undecalcified polished thin sections were prepared from the implant/bone areas 1 and 4 weeks after implantation. Results: PXR radiography showed a distinct difference between the newly formed bone and the compact bone. Color-mapping of the images showed an increase in the total amount of bone formation with time. Conclusion: Application of LEBRA-PXR, a high-powered, highly monochromatized and highly parallel oriented X-ray allowed easy and accurate radiographic analysis of new bone formation around the implant.