PubMed · 9567895
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J S Gross. 1996. Suturing techniques for advanced extraction therapy.. https://pubmed.ncbi.nlm.nih.gov/9567895/
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Highly porous poly(D,L-lactide)/Bioglass composites scaffolds were prepared by thermally induced phase separation process of polymer solutions and subsequent solvent sublimation. A series of composite foams with different polymer/Bioglass weight ratios was prepared to study the influence of Bioglass content on the foam characteristics such as porous structure, density, and pore volume. The pore volume was decreased from 9.5 to 5.7 cm(3)/g when the Bioglass content was increased up to 40 wt %, but the overall pore morphology was not affected very much by changing the polymer/glass composition ratio. The composites foams were then incubated in phosphate-buffered saline at 37 degrees C to study the in vitro degradation of the polymer and to detect hydroxyapatite (HA) formation as an indication of their bioactivity. The addition of Bioglass to polymer foams increased the water absorption and weight loss as compared with pure polymer foams. However, the polymer molecular weight, determined by size exclusion chromatography, was found to decrease more rapidly and to a larger extent in absence of Bioglass. This delayed degradation rate in the composite foams was probably caused by the dissolution of alkaline ions from the Bioglass, resulting in a buffering effect of the incubation medium. After incubation for 7 days, HA was detected by X-ray diffractometry and Raman spectroscopy and confirmed by environmental scanning electron microscopy and energy-dispersive X-ray analysis. The porous composites developed here are promising materials for bone regeneration applications because the formation of HA on the surface of the pore walls should provide good environment for the adhesion and proliferation of osteoblasts and osteoprogenitor cells.
Previous in vivo studies revealed a stimulating effect of locally applied IGF-I and TGF-beta1 released from poly(D,L-lactide)-coated titanium implants on rat and porcine fracture healing. The purpose of the present study was to evaluate the effect of IGF-I (5% w/w) and TGF-beta1 (1% w/w) and the carrier PDLLA on osteoblasts in cell culture to improve the understanding of these growth factors. The well-characterized human osteoblast cell line hFOB 1.19 was used in the study. The implants and cells were cocultured in a noncontact manner. The cells were incubated for 10 days in total, and the implants (n = 6 each group and time point) were added for 1 h, 12 h, 24 h, 2 d, 4 d, or 10 d. To analyze a possible effect of the growth factors or the coating, cell proliferation, metabolism, and differentiation were investigated. As an indicator for differentiation the production of collagen I was chosen. All experimental groups showed comparable cell vitality. No change in the pH of the medium was detectable between the analyzed groups. When the effect of the titanium implant and the PDLLA coating were compared with the control culture, no differences in proliferation, metabolic activity, and collagen I production were detectable. The osteoblasts treated with IGF-I and TGF-beta1 released from PDLLA revealed a significantly enhanced collagen I production with a decrease in proliferation and metabolic activity compared to the other groups. No significant differences in collagen I production were seen due to the incubation time points. None of the experimental groups evoked an immunological response on mouse macrophages. In conclusion, the PDLLA-carrier showed no negative effect on osteoblasts, whereas the incorporated growth factors stimulated osteoblast differentiation.
Pulsed electromagnetic fields (PEMFs) are known to be effective in the stimulation of cultured osteoblasts and in vivo healing of delayed and nonunion fractures. In the present in vitro study the effects of PEMFs on osteoblastic cell cultures (MG63 human osteoblast-like cells) grown in the presence of poly-methylmethacrylate (PMMA) and of a biomimetic bone substitute made of a PMMA matrix added with alfa-tricalcium phosphate (PMMA+alpha-TCP) were evaluated, to assess the biological response at the cell-biomaterial interaction. Cultures were stimulated with PEMFs (75 Hz, 2.3 mT, 1.3-ms pulse duration) 12 h/day for 3 days and evaluations (MTT, ALP, OC, PICP, TGFbeta-1, IL-6) were performed at 3 and 6 days. PMMA had a negative effect on osteoblasts, whereas PMMA+alpha-TCP enhanced production of ALP, PICP, OC and TGFbeta-1, and reduced IL-6 levels. Cells responded positively to PEMF stimulation even when cultured with a poorly biocompatible material, such as PMMA. This effect was more evident in the presence of PMMA+alpha-TCP (further improvement in proliferation and synthetic activity) both at 3 and at 6 days. The properties of PMMA+alpha-TCP look promising, and the present results support the use of PEMFs to improve tissue response to biomaterials implanted as bone substitutes.