Biphasic calcium sulfate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications: in vitro study

Composite Materials Based on Gelatin and Iron Oxide Nanoparticles for MRI Accuracy

The majority of recent studies have focused on obtaining MRI materials for internal use. However, this study focuses on a straightforward method for preparing gelatin-based materials with iron oxide nanoparticles (G-Fe2O3 and G-Fe3O4) for external use. The newly obtained materials must be precisely tuned to match the requirements and usage situation because they will be in close touch with human/animal skin. The biocompatible structures formed by gelatin, tannic acid, and iron oxide nanoparticles were investigated by using FTIR spectroscopy, SEM-EDAX analysis, and contact angle methods. The physico-chemical properties were obtained by using mechanical investigations, dynamic vapor sorption analysis, and bulk magnetic determination. The size and shape of iron oxide nanoparticles dictates the magnetic behavior of the gelatin-based samples. The magnetization curves revealed a typical S-shaped superparamagnetic behavior which is evidence of improved MRI image accuracy. In addition, the MTT assay was used to demonstrate the non-toxicity of the samples, and the antibacterial test confirmed satisfactory findings for all G-based materials.

Mechanical Characterization and In Vitro Assay of Biocompatible Titanium Alloys

Metals that come into contact with the body can cause reactions in the body, so biomaterials must be tested to avoid side effects. Mo, Zr, and Ta are non-toxic elements; alloyed with titanium, they have very good biocompatibility properties and mechanical properties. The paper aims to study an original Ti20Mo7ZrxTa system (5, 10, 15 wt %) from a mechanical and in vitro biocompatibility point of view. Alloys were examined by optical microstructure, tensile strength, fractographic analysis, and in vitro assay. The obtained results indicate very good mechanical and biological properties, recommending them for future orthopedic medical applications.

Novel Mg-0.5Ca-xMn Biodegradable Alloys Intended for Orthopedic Application: An In Vitro and In Vivo Study

Mg-based biodegradable materials, used for medical applications, have been extensively studied in the past decades. The in vitro cytocompatibility study showed that the proliferation and viability (as assessed by quantitative MTT-assay-3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyl tetrazolium bromide) were not negatively affected with time by the addition of Mn as an alloying element. In this sense, it should be put forward that the studied alloys don't have a cytotoxic effect according to the standard ISO 10993-5, i.e., the level of the cells' viability (cultured with the studied experimental alloys) attained both after 1 day and 5 days was over 82% (i.e., 82, 43-89, 65%). Furthermore, the fibroblastic cells showed variable morphology (evidenced by fluorescence microscopy) related to the alloy sample's proximity (i.e., related to the variation on the Ca, Mg, and Mn ionic concentration as a result of alloy degradation). It should be mentioned that the cells presented a polygonal morphology with large cytoplasmic processes in the vicinity of the alloy's samples, and a bipolar morphology in the remote region of the wells. Moreover, the in vitro results seem to indicate that only 0.5% Mn is sufficient to improve the chemical stability, and thus the cytocompatibility; from this point of view, it could provide some flexibility in choosing the right alloy for a specific medical application, depending on the specific parameters of each alloy, such as its mechanical properties and corrosion resistance. In order to assess the in vivo compatibility of each concentration of alloy, the pieces were implanted in four rats, in two distinct body regions, i.e., the lumbar and thigh. The body's reaction was followed over time, 60 days, both by general clinical examinations considering macroscopic changes, and by laboratory examinations, which revealed macroscopic and microscopic changes using X-rays, CT(Computed Tomography), histology exams and SEM (Scanning Electron Microscopy). In both anatomical regions, for each of the tested alloys, deformations were observed, i.e., a local reaction of different intensities, starting the day after surgery. The release of hydrogen gas that forms during Mg alloy degradation occurred immediately after implantation in all five of the groups examined, which did not affect the normal functionality of the tissues surrounding the implants. Imaging examinations (radiological and CT) revealed the presence of the alloy and the volume of hydrogen gas in the lumbar and femoral region in varying amounts. The biodegradable alloys in the Mg-Ca-Mn system have great potential to be used in orthopedic applications.

Microstructural, Electrochemical and In Vitro Analysis of Mg-0.5Ca-xGd Biodegradable Alloys

The subject of Mg-based biodegradable materials, used for medical applications, has been extensively studied throughout the years. It is a known fact that alloying Mg with biocompatible and non-toxic elements improves the biodegradability of the alloys that are being used in the field of surgical applications. The aim of this research is to investigate the aspects concerning the microstructure, electrochemical response (corrosion resistance) and in vitro cytocompatibility of a new experimental Mg-based biodegradable alloy—Mg–0.5%Ca with controlled addition of Gd as follows: 0.5, 1.0, 1.5, 2.0 and 3.0 wt.%—in order to establish improved biocompatibility with the human hard and soft tissues at a stable biodegradable rate. For this purpose, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), light microscopy (LM) and X-ray diffraction (XRD) were used for determining the microstructure and chemical composition of the studied alloy and the linear polarization resistance (LPR) method was used to calculate the corrosion rate for the biodegradability rate assessment. The cellular response was evaluated using the 3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test followed by fluorescence microscopy observation. The research led to the discovery of a dendritic α-Mg solid solution, as well as a lamellar Mg2Ca and a Mg5Gd intermetallic compound. The in vivo tests revealed 73–80% viability of the cells registered at 3 days and between 77 and 100% for 5 days, a fact that leads us to believe that the experimental studied alloys do not have a cytotoxic character and are suitable for medical applications.

Strontium-calcium phosphate hybrid cement with enhanced osteogenic and angiogenic properties for vascularised bone regeneration

Vascularized bone tissue engineering is regarded as one of the optimal treatment options for large bone defects. The lack of angiogenic properties and unsatisfactory physicochemical performance restricts calcium phosphate cement (CPC) from application in vascularized bone tissue engineering. Our previous studies have developed a starch and BaSO4 incorporated calcium phosphate hybrid cement (CPHC) with improved mechanical strength and handling properties. However, the bioactivity-especially the angiogenic ability-is still absent and requires further improvement. Herein, based on the reported CPHC and the osteogenic and angiogenic properties of strontium (Sr) ions, a strontium-enhanced calcium phosphate hybrid cement (Sr-CPHC) was developed to improve both biological and physicochemical properties of CPC. Compared to CPC, the initial setting time of Sr-CPHC was prolonged from 2.2 min to 20.7 min. The compressive strength of Sr-CPHC improved from 11.21 MPa to 45.52 MPa compared with CPC as well. Sr-CPHC was biocompatible and showed promotion of alkaline phosphatase (ALP) activity, calcium nodule formation and osteogenic relative gene expression, suggesting high osteogenic-inductivity. Sr-CPHC also facilitated the migration and tube formation of human umbilical vein endothelial cells (HUVECs) in vitro and up-regulated the expression of the vascular endothelial growth factor (VEGF) and Angiopoietin-1 (Ang-1). In vivo evaluation showed marked new bone formation in a rat calvarial defect model with Sr-CPHC implanted. Sr-CPHC also exhibited enhancement of neovascularization in subcutaneous connective tissue in a rat subcutaneous implantation model. Thus, the Sr-CPHC with the dual effects of osteogenesis and angiogenesis shows great potential for clinical applications such as the repair of ischemic osteonecrosis and critical-size bone defects.

Electrochemical Analysis and In Vitro Assay of Mg-0.5Ca-xY Biodegradable Alloys

In recent years, biodegradable Mg-based materials have been increasingly studied to be used in the medical industry and beyond. A way to improve biodegradability rate in sync with the healing process of the natural human bone is to alloy Mg with other biocompatible elements. The aim of this research was to improve biodegradability rate and biocompatibility of Mg-0.5Ca alloy through addition of Y in 0.5/1.0/1.5/2.0/3.0wt.%. To characterize the chemical composition and microstructure of experimental Mg alloys, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), light microscopy (LM), and X-ray diffraction (XRD) were used. The linear polarization resistance (LPR) method was used to calculate corrosion rate as a measure of biodegradability rate. The cytocompatibility was evaluated by MTT assay (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide) and fluorescence microscopy. Depending on chemical composition, the dendritic α-Mg solid solution, as well as lamellar Mg₂Ca and Mg₂₄Y₅ intermetallic compounds were found. The lower biodegradability rates were found for Mg-0.5Ca-2.0Y and Mg-0.5Ca-3.0Y which have correlated with values of cell viability. The addition of 2-3 wt.%Y in the Mg-0.5Ca alloy improved both the biodegradability rate and cytocompatibility behavior.

Novel titanium-apatite hybrid scaffolds with spongy bone-like micro architecture intended for spinal application: In vitro and in vivo study

Titanium alloy scaffolds with novel interconnected and non-periodic porous bone-like micro architecture were 3D-printed and filled with hydroxyapatite bioactive matrix. These novel metallic-ceramic hybrid scaffolds were tested in vitro by direct-contact osteoblast cell cultures for cell adhesion, proliferation, morphology and gene expression of several key osteogenic markers. The scaffolds were also evaluated in vivo by implanting them on transverse and spinous processes of sheep's vertebras and subsequent histology study. The in vitro results showed that: (a) cell adhesion, proliferation and viability were not negatively affected with time by compositional factors (quantitative MTT-assay); (b) the osteoblastic cells were able to adhere and to attain normal morphology (fluorescence microscopy); (c) the studied samples had the ability to promote and sustain the osteogenic differentiation, matrix maturation and mineralization in vitro (real-time quantitative PCR and mineralized matrix production staining). Additionally, the in vivo results showed that the hybrid scaffolds had greater infiltration, with fully mineralized bone after 6 months, than the titanium scaffolds without bioactive matrix. In conclusion, these novel hybrid scaffolds could be an alternative to the actual spinal fusion devices, due to their proved osteogenic performance (i.e. osteoinductive and osteoconductive behaviour), if further dimensional and biomechanical optimization is performed.

Good hydration and cell-biological performances of superparamagnetic calcium phosphate cement with concentration-dependent osteogenesis and angiogenesis induced by ferric iron

Superparamagnetic Fe³⁺-doped calcium phosphate cement (Fe-CPC) has prospective applications in bone remodeling due to its good hydration properties and significant effect on osteogenesis and angiogenesis.

Osteogenesis of mineralized collagen bone graft modified by PLA and calcium sulfate hemihydrate: in vivo study

In this study, the biocompatibility and bone regeneration performance of nano-hydroxyapatite/collagen/poly(L-lactide) (nHAC/PLA) and nano-hydroxyapatite/collagen/calcium sulfate hemihydrate (nHAC/CSH) as bone-filling materials were evaluated and compared in a critical box-shaped defect model in the mandible of the rabbits. In vivo results indicated that there was significant difference in early bone remodeling between two types of bone substitutes. nHAC/PLA has shown excellent biocompatibility, but no adequate handling properties. The addition of CSH to nHAC provided better manipulability compared to nHAC/PLA. Furthermore, nHAC/CSH possesses superior properties in restoring critical-sized bone defects of maxillofacial region at the early stage of remodeling over nHAC/PLA. Our results suggested that nHAC/CSH could be an alternative to the conventionally used bone tissue engineering materials.

Biocompatibility and osteogenic potential of new generation endodontic materials established by using primary osteoblasts

INTRODUCTION

Generex A and Generex B (calcium silicate based), Capasio (calcium-phospho-alumino silicate based) along with Ceramicrete-D (magnesium phosphate based) are being introduced as a new generation of endodontic materials with the potential to facilitate bone healing. The aim of this study was to evaluate the biocompatibility and osteogenic potential of these new materials by using primary osteoblasts.

METHODS

Primary osteoblasts were prepared from rat calvaria and exposed to mineral trioxide aggregate (MTA), Generex A, Generex B, Capasio, and Ceramicrete-D prepared to standardized size and shape (n = 5). Trypan blue staining was used to evaluate cell viability from 1-6 days. Mineralization potential was evaluated by scanning electron microscopy for the presence of mineralized nodules. Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

Only Generex A and MTA allowed cell growth and proliferation throughout the experiment. There were statistically significant differences between groups throughout the experiment beginning on day 1. The greatest amount of cell growth was consistently observed with Generex A and MTA. There was no difference in mineralized nodule formation between any test materials.

CONCLUSIONS

Generex A was the only new generation endodontic material that supported primary osteoblast growth; no material besides MTA facilitated nodule formation.

Preparation of combined β-TCP/α-CSH artificial bone graft and its performance in a spinal fusion model

To evaluate α-calcium sulfate hemihydrate (α-CSH)/β-tricalcium phosphate (β-TCP) combined artificial bone graft (COB) in an animal model of posterolateral spinal fusion, α-CSH and β-TCP were combined in a 3 : 7 weight ratio. A rabbit model of posterolateral spinal fusion was produced ( N = 36); one side was implanted with the COB, and the other with local autogenous bone. Rabbits were killed on the 4th, 8th, or 12th week after surgery and fusion, COB degradation, mineralization, and new bone formation were evaluated. Scanning electron microscopy revealed that the COB retained the porous spatial structure of β-TCP and α-CSH crystals were adhered to the surface and pores of β-TCP. At the 12th week after surgery, the fusion rate was 75.0% on the 12th week after the operation, which was higher than the fusion rate of 54.4% the autogenous bone side ( p = 0.073). Bone volume fraction of the COB was 0.49 ± 0.08 for the 4th week and 0.16 ± 0.05 for the 12th week after surgery. The mineralization rate of the new bone was greater on the side implanted with autogenous bone than on the side implanted with COB at all the three time points after surgery. At each time point after surgery, the difference in mineralization rate between the autogenous bone side and the COB side was statistically significant ( p < 0.001); α-CSH/β-TCP in a 3 : 7 weight ratio was as effective as local autogenous bone in producing spinal fusion in a rabbit model. Used in this ratio, the speed of material degradation and new bone formation are relatively equivalent, and the rate of new bone mineralization is similar to that of autogenous bone graft.