Evaluation by Bone Scintigraphy of Osteogenic Activity of Commercial Bioceramics (Porous β-TCP and HAp Particles) Subcutaneously Implanted in Rats

Abstract

Osteogenic potential of biomaterials used in bone regenerative therapy has been mainly examined in an animal-implantation study. We have here evaluated the applicability of bone scintigraphy in imaging ectopic bone formation, especially its initial phase, by β-tricalcium phosphate (β-TCP) particles that were implanted in rat dorsal subcutaneous tissues. In implanted osteogenic osteosarcoma cells used as a positive control, osteoid formation was found by histological examination and bone scintigraphy using 99mTc- hydroxymethyl diphosphonate (HMDP) at 2 and 3 weeks post-implantation, respectively, while the microfocuscomputed tomography (μCT) system required further mineralization, which occurred at 4 weeks. Implantation of β-TCP particles alone induced only faint biomineralization inside the particles, which could be microscopically detected by calcein chelation at 2 weeks post-implantation, but not by other histological examinations (e.g., HE staining) or μCT. However, the bone scintigraphy successfully detected this microscopic change at 1 week. Implanted hydroxyapatite (HAp) particles alone used as a negative control did not induce mineralization at microscopic levels, and therefore nothing was detected by either calcein chelation or bone scintigraphy. In conclusion, the bone scintigraphic methodology, although exhibiting less quantitation and resolution, would be applicable as a non-invasive, highly sensitive methodology in detecting the initial, microscopic changes associated with mineralization.

Variability of the Biological Activity of Oxidized Titanium Implants

“…Oxi de coating was formed by anode spark oxidation in electric pulsed mode. Sulfuric and/or phosphoric acid solutions served as the electrolytes [2,8]. The coatings on the implants were studied by x-ray analysis, optical microscopy, and local micro x-ray analysis [2,3].…”

“…Bioinert and osteoinductive characteristics of the implants were studied by ectopic osteoformation by the standard method [2,8,9]. To this end, the bone marrow was washed out from the femoral bone with 1 ml RPMI-1640 (Sigma) into Petri dishes and transferred with forceps onto the surface of titanium implant, which was then implanted under the skin to recipient mice.…”

“…Titanium implants are widely used in medical materials technology due to high biocompatibility, low thermal conductivity, low weight, and corrosion resistance [2,4,6,8]. Interaction of titanium with oxygen, water, other biological fl uids and under specially created conditions leads to the formation of dioxide layer on its surface, due to which titanium implants become bioinert [5,6,8].…”

“…Interaction of titanium with oxygen, water, other biological fl uids and under specially created conditions leads to the formation of dioxide layer on its surface, due to which titanium implants become bioinert [5,6,8]. These implants are indispensable in medicine and dentistry in many cases.…”

Noninvasive near-infrared fluorescent protein-based imaging of tumor progression and metastases in deep organs and intraosseous tissues

“…Excised tissues were then placed on the stage and their fluorescence captured as indicated above. Image analysis was performed according to Nakayama et al 19 In brief, regions of interest (ROIs) were targeted on iRFP fluorescent sites and circles with the minimum size were drawn around lesions on each image. The pixel density in the selected ROI was quantitated using the software for image analysis provided with the Pearl ® Imager.…”