Promising Bone Repair Material Research Articles

<i>In Vitro</i> and <i>In Vivo</i> Evaluation of Bioactive Glass/PVA Porous Hybrids for Application in Bone Reconstruction

Bioactive glass/polymer hybrids are promising materials for biomedical applications because they combine the bioactivity of these bioceramics with the flexibility of polymers. In previous work hybrid foams with 50% bioactive glass and 50% polyvinyl alcohol (PVA) were prepared by the sol-gel process for application as scaffold for bone tissue engineering. In this work the hybrid samples were tested in osteoblast culture to evaluate adhesion and proliferation. Samples were also implanted subcutaneously in the dorsal region of adult rats. The hybrid 50% PVA/bioactive glass foam was chosen as the best scaffold in the composition range studied and it is a promising material for bone repair, providing a good environment for the adhesion and proliferation of osteoblasts in vitro. Concerning the in vivo studies we can assure that the “foreing body” reaction was moderate and that the presence of osteoid indicated bone matrix formation.

Improved injectability and in vitro degradation of a calcium phosphate cement containing poly(lactide-co-glycolide) microspheres

An injectable calcium phosphate cement (CPC) containing 30 wt.% poly(lactide-co-glycolide) (PLGA) microspheres was developed in the present study. Sodium citrate solution was used as the cement liquid phase. The effects of sodium citrate concentration on the injectability, rheological properties, mechanical strength and self-setting properties of CPC containing PLGA microspheres were systematically investigated. The in vitro degradation behavior of the composite during immersion in phosphate buffer solution was also studied. With an increase in sodium citrate concentration, the viscosity and yield stress of the paste were reduced, thereby improving the injectability. At a sodium citrate concentration of 15%, the injectability of the paste reached 95%. The compressive strength of the specimen was also enhanced by the addition of sodium citrate. The specimens had a compressive strength of 32.24 ± 2.72 MPa at 15% sodium citrate concentration, compared to 22.15 ± 3.60 MPa for the specimen without sodium citrate. The in vitro degradation results demonstrate that incorporated PLGA microspheres can provide the required high strength to CPC in the early stage, which would gradually degrade to create macropores for bone ingrowth. In conclusion, an in situ macropore-generable CPC exhibited excellent injectability and high early strength, and should be a promising material for bone repair and bone reconstruction.

β‐CaSiO3/β‐Ca3(PO4)2 composite materials for hard tissue repair: In vitro studies

In this study, a series of beta-CaSiO(3) (CS)/beta-Ca(3)(PO(4))(2) (TCP) composites with different ratios were prepared to produce new bioactive and biodegradable biomaterials for potential bone repair. The mechanical properties of CS-TCP composites increased steadily with the increase of TCP amounts in composites. Formation of bone-like apatite on a range of CS-TCP composites with CS weight percentage ranging from 0 to 100 has been investigated in simulated body fluid (SBF). The presence of bone-like apatite layer on the composite surface after soaking in SBF was demonstrated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and fourier transform infrared reflection spectroscopy (FTIR). The results showed that the apatite formation ability of the CS-TCP composite was enhanced with increasing CS content in the composites. For composites with more than 50% CS contents, the samples were completely covered by a layer of dense bone-like apatite just after 3 days immersion. Dissolution tests in Tris-HCl buffer solution showed obvious differences with different CS contents in composites. The dissolution rate increased with the increase of CS content, which suggested that the solubility of biphasic composites could be tailored by adjusting the initial CS/TCP ratio. In vitro cell experiments showed that higher content of CS phase in composites promoted cell proliferation and differentiation. When the CS amount in the composite increased to 50%, the proliferation rate and ALP activities of osteoblast-like cells showed significant difference compared with pure TCP (p < 0.05). Results of the study suggested that the CS-TCP composites with more than 50% CS content might be promising bone repair materials.

Use of collagen sponge incorporating transforming growth factor- β1 to promote bone repair in skull defects in rabbits

The objective of this study was to evaluate the potential of collagen sponge incorporating transforming growth factor- β1 (TGF- β1) to enhance bone repair. The collagen sponge was prepared by freeze-drying aqueous foamed collagen solution. Thermal cross-linking was performed in a vacuum at 140°C for periods ranging from 1 to 48 h to prepare a number of fine collagen sponges. When collagen sponges incorporating 125I-labeled TGF- β1 were placed in phosphate-buffered saline (PBS) solution at 37°C, a small amount of TGF- β1 was released for the first hour, but no further release was observed thereafter, irrespective of the amount of cross-linking time the sponges had received. Collagen sponges incorporating 125I-labeled TGF- β1 or simply labeled with 125I were implanted into the skin on the backs of mice. The radioactivity of the 125I-labeled TGF- β1 in the collagen sponges decreased with time; the amount of TGF- β1 remaining dependent on the cross-linking time. The in vivo retention of TGF- β1 was longer in those sponges that had been subjected to longer cross-linking times. The in vivo release profile of the TGF- β1 was matched with the degradation profile of the sponges. Scanning electron microscopic observation revealed no difference in structure among sponges subjected to different cross-linking times. The TGF- β1 immobilized in the sponges was probably released in vivo as a result of sponge biodegradation because TGF- β1 release did not occur in in vitro conditions in which sponges did not degrade. We applied collagen sponges incorporating 0.1 μg of TGF- β1 to skull defects in rabbits in stress-unloaded bone situations. Six weeks later, the skull defects were covered by newly formed bone, in marked contrast to the results obtained with a TGF- β1-free empty collagen sponge and 0.1 μg of free TGF- β1. We concluded that the collagen sponges were able to release biologically active TGF- β1 and were a promising material for bone repair.