Fabrication and biocompatibility of a porous bioglass ceramic in a Na2O-CaO-SiO2-P2O5 system

Bioactive Glass—An Extensive Study of the Preparation and Coating Methods

Diseases or complications that are caused by bone tissue damage affect millions of patients every year. Orthopedic and dental implants have become important treatment options for replacing and repairing missing or damaged parts of bones and teeth. In order to use a material in the manufacture of implants, the material must meet several requirements, such as mechanical stability, elasticity, biocompatibility, hydrophilicity, corrosion resistance, and non-toxicity. In the 1970s, a biocompatible glassy material called bioactive glass was discovered. At a later time, several glass materials with similar properties were developed. This material has a big potential to be used in formulating medical devices, but its fragility is an important disadvantage. The use of bioactive glasses in the form of coatings on metal substrates allows the combination of the mechanical hardness of the metal and the biocompatibility of the bioactive glass. In this review, an extensive study of the literature was conducted regarding the preparation methods of bioactive glass and the different techniques of coating on various substrates, such as stainless steel, titanium, and their alloys. Furthermore, the main doping agents that can be used to impart special properties to the bioactive glass coatings are described.

Micro-CT and Histomorphometric Study of Bone Regeneration Effect with Autogenous Tooth Biomaterial Enriched with Platelet-Rich Fibrin in an Animal Model

The aim of this study was to evaluate the potential of tooth biomaterials as bone graft biomaterials for bone healing in rabbits. We prepared tooth biomaterial and platelet-rich fibrin (PRF) to fill the round-shaped defect in the skull of New Zealand white rabbits. These cranial defects were treated with different conditions as follows: group 1, a mixture of tooth biomaterials and platelet-rich fibrin (PRF); group 2, only tooth biomaterials; group 3, only PRF; and group 4, the unfilled control group. Specimens of the filled sites were harvested for analysis with microscopic computerized tomography (micro-CT) and histomorphology at 4 and 8 weeks. As a result of micro-CT, at 4 weeks, the bone volume percentages in groups 1 and 2 were 50.33 ± 6.35 and 57.74 ± 3.13, respectively, and that in the unfilled control group was 42.20 ± 10.53 (p = 0.001). At 8 weeks, the bone volume percentages in groups 1 and 2 were 53.73 ± 9.60 and 54.56 ± 8.44, respectively, and that in the unfilled control group was 37.86 ± 7.66 (p = 0.002). The difference between the experimental group 3 and the unfilled control group was not statistically significant. Histomorphologically, the total new bone was statistically different.

Effect of alumina on microstructure and compressive strength of a porous silicated hydroxyapatite

PURPOSE

We investigated the effects of alumina addition on microstructure and compressive strength of a porous silicate substituted hydroxyapatite (Si-HA).

METHODS

Hydroxyapatite (HA) was synthesized under precipitation conditions and 10 %Wt. of sol-gel derived CaO.P2O5.SiO2 based bioglass (BG) powder was added to HA. Polyurethane foam was used to form a high porous structure with integral porosity of 70%. Phase analysis was performed using XRD and FTIR and the microstructure was studied using SEM.

RESULTS

The results confirmed that the Si-HA was the only formed phase before Al2O3 addition while after addition the presence of silicon-incorporated HA and alumina without any other phases was proved using these analyses.

CONCLUSIONS

The porous structures of Si-HA and Al2O3 were synthesized using the replication technique. The compressive strength of porous bioceramics increased with increasing Al2O3 content up to 30 wt% (ANOVA, P<.05).

Fabrication of bioglass infiltrated Al(2)O (3)-(m-ZrO (2)) composites

Using 80 vol.% of poly methyl methacrylate (PMMA) as a pore-forming agent to obtain interconnected porous bodies, porous Al(2)O(3)-(m-ZrO(2)) bodies were successfully fabricated. The pores were about 200 microm in diameter and were homogeneously dispersed in the Al(2)O(3)-25 vol.% (m-ZrO(2)) matrix. To obtain Al(2)O(3)-(m-ZrO(2))/bioglass composites, the molten bioglass was infiltrated into porous Al(2)O(3)-(m-ZrO(2)) bodies at 1400 degrees C. The material properties of the Al(2)O(3)-(m-ZrO(2))/bioglass composites, such as relative density, hardness, compressive strength, fracture toughness and elastic modulus were investigated.

The development of magnetic degradable DP-Bioglass for hyperthermia cancer therapy

In this study, a novel magnetic degradable material was developed by adding Fe ions into DP-Bioglass (Na(2)O-CaO-P(2)O(5)-SiO(2)) as thermoseed for hyperthermia cancer therapy under an alternating magnetic field. We have investigated the properties of developed magnetic DP-Bioglass including morphology, chemical composition, and magnetism. The degradability was conducted by measuring the released concentrations of Na, Ca, Si, P, and Fe ions. The biocompatibility was analyzed by biological assays, and the functional hyperthermia effect to cancer cells was evaluated by in vitro cell culture test. In the results, the morphology of synthesized magnetic DP-Bioglass was revealed in sphere and rod shape with particle size around 50-100 nm. From the hysteresis loop analysis, it showed that the group of Fe/Bioglass = 0.2 possessed the maximum magnetization property. When cultured with fibroblasts, the magnetic DP-Bioglass had no significant influence on cell viability and mediated low cytotoxicity. The thermal-induced property demonstrated that after exposure to an alternating magnetic field, the cell number of human Caucasian lung carcinoma cells (A549) was significantly decreased when temperature was increasing to 45 degrees C. In brief, successfully incorporated with Fe ions by sol-gel method, this magnetic degradable DP-Bioglass possessed the potential and properties of hyperthermia effect to lung carcinoma cells.

Calvarial bone response to a tricalcium phosphate-genipin crosslinked gelatin composite

A biodegradable composite which was composed of genipin cross-linked gelatin mixing with tricalcium phosphate ceramic particles (GGT) was developed as a bone substitute. This study was evaluated by the biological response of rabbit calvarial bone to assess the potential of the GGT composite as a biodegradable and osteoconductive bone substitute. Eighteen New Zealand white rabbits were used for cranial implantation. Bone defects (15 x 15 mm) of nine rabbits were filled with the GGT composites, while the others were filled with the de-proteinized bovine bones as controls. Three rabbits were examined for each group in every time period at 4, 8 and 12 weeks post-surgery. The assessment included serial post-operative gross examinations, radiographic analyses and histological evaluations. This study demonstrated that this composite is: (1) malleable, with easily molded to the calvarial bone defect without fracture; (2) biocompatible, with no evidence of adverse tissue reaction; (3) osteoconductive, with progressive growth of new bone into the calvarial bone defect; (4) biodegradable, with progressive replacement of the composite by new bone. Additionally, results of both radiographic analyses and histological evaluations revealed obviously greater new bone ingrowth in the GGT composite compared with the de-proteinized bovine bone at the same implantation time. Therefore, the GGT composite could serve as a useful bone substitute for repairing bone defects.

In vitro evaluation of degradation and cytotoxicity of a novel composite as a bone substitute

The purpose of this study was to prepare and evaluate in vitro the feasibility and cytocompatibility of a novel composite (GGT) as a large defect bone substitute. The composite is tricalcium phosphate ceramic particles combined with genipin crosslinked gelatin. After soaking the GGT composites in Ringer solutions at 37 degrees C for 7, 14, 28, 42, 56, and 84 days, the in vitro biologic degradation rate and biocompatibility were determined. Substances released from soaked GGT composites were analyzed with an ultraviolet visible light spectrophotometer. In addition, the solution soaking the GGT was co-cultured with osteoblasts to determine whether or not the released substances from GGT could facilitate the growth of bone cells. After they had been cultured for 2 days, the osteoblasts were tested for differentiation and proliferation by alkaline phosphatase (ALP) activity and a MTT assay. Results indicate that the concentration of the genipin solution is a critical factor in deciding the crosslinking degree of the GGT composite. Complete crosslinking reaction in the GGT composite occurred when 0.5 wt % of genipin had been added. Cytotoxic testing revealed that 80 ppm of the genipin in the culture medium served as the level over which cytotoxicity to osteoblasts could be produced. In addition, we found that gelatin and calcium continuously were released from the GGT composite in the soaking solution, which promoted differentiation and proliferation of the osteoblasts.

Fabrication and evaluation of a new composite composed of tricalcium phosphate, gelatin and chi-li-saan as a bone substitute

The purpose of this study was to prepare and evaluate the feasibility and biocompatibility of a new composite as a bone substitute. The new composite (GTGC) was mainly composed of tricalcium phosphate ceramics and gelatin to which chi-li-saan, a Chinese medicinal remedy was added. The GTGC composite was manually packed into cylindrical Teflon molds, dried overnight in an oven and sterilized by gamma-ray prior to use. Mature New Zealand rabbits, weighting 3-3.5 kg, underwent full-thickness excision of the parietal bone. In the experimental group, bone defects of 12 animals were filled with the GTGC composites and another 12 unreconstructed rabbits were considered as controls. Three rabbits were examined for each group in every time period at 2, 4, 8 and 12 weeks after operation. There was no evidence of adverse tissue reaction to the GTGC composite. In addition, examination with light and fluorescent microscopy revealed a significantly greater amount of new bone ingrowth in the GTGC group at the same implantion time as compared with the controls. Therefore, the GTGC composite could serve as a useful substitute when repairing bone defects.

Osteogenic evaluation of glutaraldehyde crosslinked gelatin composite with fetal rat calvarial culture model

The cytotoxicity of the synthetic bone substitute composed of tricalcium phosphate and glutaraldehyde crosslinked gelatin (GTG) were evaluated by osteoblast cell culture. In a previous study, the GTG composites were soaked in distilled water for 1, 2, 4, 7, 14, 28, and 42 days, and then the solutions (or extracts) were cocultured with osteoblasts to evaluate the cytotoxicity of GTG composites by alive cell counting. In this study, the extracts were cocultured with the osteoblasts; thereafter, the concentration of transforming growth factor-beta (TGF-beta1) and prostaglandin E2 (PGE2) in the medium was analyzed to strictly reflect the biological effects of GTG composites on the growth of osteoblasts. In order to investigate the osteoconductive potential of the GTG composites on new bone formation in a relative short term, a model of neonatal rat calvarial organ culture was designed prior to animal experiments. Three experimental materials of 4, 8, and 12% GTG composites were evaluated by fetal rat calvarial organ culture for their ability for bone regeneration. Deproteinized bovine and porcine cancellous bone matrixes were used as the controlled materials. All the organ culture units were maintained in cultured medium for 5 weeks. Following the culture period, the morphology of tissue was observed under an optical microscope, and the quantitative evaluation of the new generation bone was determined by using a semiautomatic histomorphometeric method. Except in the initial 4 days, the concentration of TGF-beta1 of 4% and 8% GTG composites was higher than that of the blank group for all the other experimental time periods. The PGE2 concentration for 4% and 8% GTG composites was lower than that of the blank group. It revealed that the 4% and 8% GTG composites would not lead to inflammation and would promote osteoblast growth. The morphology and activity of the osteoblasts were not transformed or changed by the 2 GTG composites. For the 12% GTG composite, the performance of the in vitro condition was inferior to the blank group and the other 2 GTG composites. Although the concentration of TGF-beta1 and PGE2 was gradually back to normal after 14 days, the morphology of the osteoblasts was abnormal with features such as contracted cytoplast structures. The osteoblast was damaged perhaps in the initial stage. We suggested that the 4% and 8% GTG composites should be soaked in distilled water at least for 4 days before medical applications. The 12% GTG composite and the composites with a concentration of glutaraldehyde solution higher than 12% were not recommended as a medical prostheses in any condition. The fetal rat calvaria culture also showed the same results with the analysis of TGF-beta1 and PGE2. From the study, we could predict the results of animal experiments in the future.

Guided tissue fabrication from periosteum using preformed biodegradable polymer scaffolds

A successful tissue engineering method for bone replacement would imitate natural bone graft by providing the essential elements for new bone formation using synthetic scaffolds, osteogenic cell populations, and bone induction factors. This is a study of the suitability of various formulations of poly(DL-lactic-co-glycolic acid) (PLGA) foams to provide a tissue conducting scaffold in an ovine model for bone flap fabrication. Three formulations were used of different copolymer ratio and molecular weight. Porous wafers of PLGA were stacked into rectangular chambers (volume 4 cm3) enclosed on five sides. Some chambers also contained autologous morcellized bone graft (MBG). The chambers were inserted with the open face adjacent to the cambium layer of the periosteum in rib beds of seven sheep and harvested after 8 weeks in vivo. Gross and histologic examination of the resulting tissue specimens demonstrated molded units of vascularized tissue generally conforming to the shape of the chambers and firmly attached to the periosteum. Polymer degradation appeared to occur by varying degrees based on polymer formulation. New bone formation was observed only in areas containing MBG. There was no evidence of significant inflammatory reaction or local tissue damage at 8 weeks. We conclude that a PLGA foam scaffold is (1) an efficient conductor of new tissue growth but not osteoinductive, (2) contributes to the shape of molded tissue, and (3) biocompatible when used in this model. Further studies are warranted to develop practical methods to deliver bone induction factors to the system to promote osseous tissue generation throughout the synthetic scaffold.

Hydroxyapatite ceramics with selected sintering additives

Several sintering additives for hydroxyapatite (HA) have been tested in order to enhance its sinterability without decomposing the HA and/or decreasing bioactivity and biocompatibility, additionally providing a weak interface for HA ceramics. The ion species of sintering additives were selected from those in the mineral constituents of hard tissues and bioactive glasses. After investigation of phase diagrams in the CaO-P2O5-additive systems, and analysis of physiochemical properties of the additives, several sintering aids for HA have been chosen. Subsequently, densification, phase composition, grain growth and fracture behaviour of HA containing 5 wt% of each additive, sintered at 1000-1100 degrees C, have been studied. H3BO3, CaCl2, KCl, KH2PO4, (KPO3)n and Na2Si2O5 did not enhance densification of HA. K2CO2, Na2CO3, KF and sodium phosphates improved the densification significantly. Expect for KCl and some sodium phosphates, all the additives caused formation of large quantities of undesired beta-tricalcium phosphate or CaO; therefore, they are not appropriate for HA. In the case of sodium phosphate additives, it was possible to avoid formation of CaO or beta-tricalcium phosphate by control of the additive quantity and chemical composition. beta-NaCaPO4 has been found to be an effective sintering agent which causes neither decomposition of HA nor formation of other undesired phases.

The effects of ultrasonic stimulation on DP-bioglass bone substitute

In previous studies, DP-bioglass showed good biocompatibility and can form a chemical bond with natural bone. After implementation in the rabbit femur condyle for 32 weeks, DP-bioglass gradually biodegraded and osteocytes grew into the material. In this study, an attempt has been made to utilize low intensity pulsed ultrasound to speed up the bone regeneration rate and DP-bioglass absorption rate when the DP-bioglass is implanted into the rabbit femur condyle as a bone substitute. The fundamental parameters of the ultrasound used were 1.5 MHz frequency, 0.5 W cm-2 intensity, on-off ratio 1:1 and 2 ms for the on-off time interval. The stimulation, in all cases, was started 24 h after the operations by applying the transducer to the skin using DIR ultrasound jelly as a coupling medium. The evaluation of the progress of bone regeneration and the material's biodegradable rate were conducted by histological examination and by measurements of the areas of regenerated bone, pores and DP-bioglass made with a planimeter. It was found that low intensity pulsed ultrasound had a profound effect on the rate both of bone regeneration and DP-bioglass bioabsorption in this rabbit model and that its mechanism of the action may be via an electromechanical kinetic effect on the cell membrane interfaces.