Biomedical subjects

Y P Bovell

Publications and source records attributed to Y P Bovell.

5 recordsLinked to original sources

PubMed2001

Biocompatibility testing of novel starch-based materials with potential application in orthopaedic surgery: a preliminary study.

This paper describes an extensive biocompatibility evaluation of biodegradable starch-based materials aimed at orthopaedic applications as temporary bone replacement/fixation implants. For that purpose, a polymer (starch/ethylene vinyl alcohol blend, SEVA-C) and a composite of SEVA-C reinforced with hydroxyapatite (HA) particles, were evaluated in both in vitro and in vivo assays. For the in vitro analysis cell culture methods were used. The in vivo tissue reactions were evaluated in an intramuscular and intracortical bone implantation model on goats, using light and scanning electron microscopy. A computerized image analysis system was used to obtain histomorphometric data regarding bone contact and remodelling after 6 and 12 weeks of implantation. In both in vitro and in vivo models, the SEVA-C-based materials did not induce adverse reactions, which in addition to their bone-matching mechanical properties makes them promising materials for bone replacement fixation.

Animals↗

PubMed1999

Bone induction by implants coated with cultured osteogenic bone marrow cells.

The availability of osteoinductive coatings on dental and orthopedic implants will result in an improved fixation of these devices. Those cases where implants are placed in poor-quality bone or where high failure rates are obtained are especially expected to gain from such coatings. This paper presents a novel, biological approach to obtain bioactive and osteoinductive coatings on bone-replacement implant materials. This so-called tissue engineering approach utilizes osteogenic bone marrow cells that are cultured on an implant material to form a bone-like tissue. The implant materials used herein included porous calcium phosphate scaffolds and metallic plates, the latter of which were coated with a biomimetic calcium phosphate coating to facilitate cellular attachment. Bone marrow cells were obtained from a variety of species, including humans, and were grown to facilitate cellular proliferation. The cells were subsequently seeded onto the implants and cultured for an additional week to facilitate osteogenic differentiation and extracellular matrix production. The resulting hybrid implants, encompassing the biomaterial carrier and cultured bone-like tissue, were subsequently implanted subcutaneously in nude mice for 4 weeks, followed by histological examination for de novo bone formation. The results revealed that newly formed bone was seen both in porous implants and on flat metallic surfaces. This bone tissue engineering approach, therefore, offers great potential to enhance bony healing around implants in a compromised bone bed.

Aged↗

PubMed1998

Bone tissue engineering on calcium phosphate-coated titanium plates utilizing cultured rat bone marrow cells: a preliminary study.

The use of osteoinductive in vitro tissue-coated implants in orthopaedic and dental surgery (e.g. revision hip arthroplasty), could result in a better fixation of these implants. However, this tissue engineering technology has only proved to be effective in porous materials and not on flat implant surfaces. In this study we have demonstrated that calcium phosphate-coated titanium plates with a layer of cultured osteogenic cells and their extracellular matrix can initiate bone formation in vivo. Both primary and subcultured rat bone marrow cells were grown on to biomimetic calcium phosphate-coated titanium plates. After 7 d of culture, in the presence or absence of dexamethasone, the implants were subcutaneously implanted in nude mice for 4 wk. Control samples, which consisted of calcium phosphate-coated plates without cultured cells and porous calcium phosphate particles with or without cultured cells, were also implanted subcutaneously. At autopsy, no bone formation could be detected on any of the control samples without cells and samples with subcultured cells, which were primary cultured in medium without dexamethasone. In contrast, clear de novo bone formation could be observed on the calcium phosphate-coated plates and in the porous calcium phosphate particles with primary or subcultured cells, which had been continuously cultured in medium with dexamethasone. These results indicate that this hybrid technology offers great potential for the fixation of flat bone replacement implants (e.g. artificial hips) in inferior bone in the future.

Journal Article↗

PubMed1994

Osteoclastic resorption of calcium phosphates is potentiated in postosteogenic culture conditions.

Cell-mediated resorption of densely sintered hydroxyapatite (HA1250), tricalcium phosphate (TCP), and 600 degrees or 900 degrees C calcined hydroxyapatite (HA600 and HA900, respectively), was investigated by using two culture systems. The first was an osteoclastic cell culture, and the second was a two-stage culture that was composed of a bonelike tissue formation on the substrata in the first stage and its subsequent resorption by osteoclasts in the second stage. Neither of the materials showed resorption or surface alterations in the osteoclastic cell culture, except for some limited phagocytotic activity on HA600 and HA900. In the two-stage culture, production of mineralized extracellular matrix was only observed on HA1250 and TCP, and its subsequent resorption by osteoclastlike cells was evident. Small and occasionally larger tartrate-resistant acid phosphatase positive cells produced 20-150 microns diameter resorption pits in both the mineralized extracellular matrix on HA1250 and TCP and the surfaces of HA600 and HA900. Resorption of the mineralized extracellular matrix on TCP also resulted in degradation of the underlying ceramic surface, mainly initiating from intergrain boundaries, whereas the surface of HA1250 remained unaltered. The results of this study clearly demonstrate that osteoclastic resorption of calcium phosphates is potentiated in postosteogenic culture conditions. A possible role for bone matrix constituents in cell-mediated resorption is hypothesized, whereas the occurrence of resorption seems to be mainly governed by the combined effects of material characteristics such as grain size and crystal structure.

Acid Phosphatase↗

PubMed1994

Structural arrangements at the interface between plasma sprayed calcium phosphates and bone.

Plasma sprayed coatings of tetracalcium phosphate, magnesium whitlockite and three types of hydroxyapatite, varying in degree of crystallinity, were evaluated with light microscopy, scanning electron microscopy and backscatter electron microscopy (BSE) after implantation periods of 1, 2 and 4 wk in rat femora. BSE revealed that both tetracalcium phosphate and semi-crystalline hydroxyapatite underwent distinct bulk degradation and loss of relatively large particles. Amorphous hydroxyapatite showed a gradual surface degradation, indicated by a transition zone varying in grey level between that of the coating and bone tissue, while degradation was negligible with the highly crystalline material and magnesium whitlockite. Degradation appeared to be related to bone apposition, since more bone seemed to be present on amorphous hydroxyapatite and tetracalcium phosphate, as compared to highly crystalline hydroxyapatite and magnesium whitlockite coatings. At the interface between bone and magnesium whitlockite, a seam of unmineralized bone-like tissue was frequently seen with light microscopy, while few areas with bone contact were present. X-ray microanalysis revealed that both the magnesium whitlockite coating and the unmineralized bone-like tissue contained substantial amounts of aluminium which, in addition to possible influences of magnesium, may have caused the impaired mineralization. The results of this preliminary study indicate that, with regard to early bone formation, amorphous hydroxyapatite coatings seem to be beneficial over highly crystalline coatings. However, further experiments should be performed to give conclusive data on (i) the statistical significance of the differences in bone apposition rate, and (ii) the long-term behaviour of both amorphous and highly crystalline coatings in bone and their relation to implant performance.

Aluminum↗