Metallic ion doped tri-calcium phosphate ceramics: Effect of dynamic loading on in vivo bone regeneration.

The present study was carried out to evaluate the effect of dynamic loading on bone regeneration performance of different doped ß-tri-calcium phosphate ceramics. We have developed porous beta tri-calcium phosphate (ß-TCP), 5%zinc doped, 5% magnesium doped and 5% titanium doped ß-TCP by aqueous solution combustion technique. All the synthesized ß-TCP powders showed pore size of 21-146 µm (pure ß-TCP), 16-142 µm (Zn-ß-TCP), 28-156 µm (Mg- ß-TCP) and 14-173 µm (Ti-ß-TCP) while their apparent porosity 17.89%, 28.09%, 26.54% and 25.87% respectively. The pure and doped samples were implanted in femoral bone defect model (rabbit) to assess bone regeneration under dynamic loading. Bone regeneration was assessed after 1 and 2 month post-implantation on the basis of clinical radiological, histological, fluorochrome labelling, micro computed tomography (µ-CT) and scanning electron microscopy (SEM). Radiological and fluorochrome labelling study showed reduced size of 5%Ti-ß-TCPimplant vis-à-vis more new bone formation as compared to other groups. Micro-CT of the implanted bone sample showed a significant amount of newly formed bony tissue surrounding the Ti-ß-TCP implant as compared to other samples. Similar findings of less interfacial gap between the implant and bone were also observed in SEM study. However, all the doped materials are suitable as bone grafting material and have potential for application in bone tissue engineering.

Synergistic Effects of Silicon/Zinc Doped Brushite and Silk Scaffolding in Augmenting the Osteogenic and Angiogenic Potential of Composite Biomimetic Bone Grafts.

Cell instructive scaffolding platforms displaying synergistic effects by virtue of their chemical and physical cues have tremendous scope in modulating cell phenotype and thus improving the success of any graft. In this regard, we report here the development of Si- and Zn-doped brushite cement composited with silk scaffolding that hierarchically emulated the cancellous bone. The composite scaffolds fabricated exhibited an open porous network capable of enhanced osteoblast survival as attested by increased alkaline phosphatase activity and also sustaining osteoclast activity affirmed by tartrate resistant acid phosphatase staining. Moreover, the chemical cues presented by dissolutions products from the composite scaffold enabled the osteoblasts to secrete proangiogenic factors which favored better endothelial cell survival, confirmed through in vitro experiments. Moreover, the efficacy of these composite biomimetic scaffolds was validated in vivo in volumetric femur defects in rabbits, which revealed that these matrices influenced vascular cell infiltration and favored the formation of matured bony plate. Fluorochrome labeling studies and microtomography analysis revealed that at the end of three months, the implanted composite scaffolds had completely resorbed, leaving behind neo-osseous tissue and vouching for clinical translation of these composite matrices as viable and affordable bone-graft substitutes.

In Vitro Biodegradation and In Vivo Biocompatibility of Forsterite Bio-Ceramics: Effects of Strontium Substitution.

The present study investigates the potential use of forsterite as an orthopedic biomaterial along with the role of strontium oxide (SrO) as a dopant. The in vitro degradation behavior was measured as a function of immersion time in simulated body fluid (SBF) for up to 8 weeks and was analyzed by micro computed tomography (µ-CT) and scanning electron microscopy (SEM). All the doped samples showed higher degradation than pure sample. The in vitro cytocompatibility study showed good cytocompatibility and proliferation of MC3T3-E1 cells on Sr-doped MgS samples. The in vivo experiments were carried out by implanting the ceramics in a rabbit femur for 30 and 90 days. The 3D µ-CT and SEM images of 2 and 3 wt % Sr-doped MgS showed increased bone regeneration around the implant materials compared with pure and 1 wt % Sr-doped MgS, which was further confirmed by quantitative oxytetracycline labeling. The histological examination of three major organs of heart, kidney, and liver confirmed that the degradation product of the MgS ceramics, with or without doping, had no toxicological side effects. These results indicate that Sr-doped MgS bioceramics exhibit enhanced degradability with the potential to be used for temporary bone regeneration.

Anomalous in Vitro and in Vivo Degradation of Magnesium Phosphate Bioceramics: Role of Zinc Addition.

In vitro and in vivo degradation behavior and biocompatibility of magnesium phosphate (MgP) bioceramics and the potential role of zinc (Zn) on degradation were compared. Samples were prepared by conventional solid-state sintering at 1200 °C for 2h. Zn-doped MgP (0.5 wt %) showed 50% less degradation than that of pure MgP after immersion into simulated body fluid (SBF) for 8 weeks. Osteoblast-like cell (MG-63) proliferation was evident in MgP ceramics, which was significantly enhanced upon Zn addition. Both Alamar Blue assay and Live/Dead imaging showed the highest cell attachment and proliferation for 0.5 wt % Zn-doped MgP. In vivo biocompatibility of these MgP ceramics were studied after implantation in the rabbit femur. The micro computed tomography (µ-CT) analysis showed that in vivo degradability increased with the increase in the Zn content which is in contradiction to in vitro degradability. Histological evaluation showed large influx of osteoclast cells to the implantation site for Zn-doped MgP samples compared to that of undoped MgP, which is the primary reason of increased degradability of these samples. After 90 days of implantation, large sections of 0.5 wt % Zn-doped MgP samples were replaced by newly formed bones. Fluorochrome labeling showed 78 ± 3% new bone formation for 0.5 wt % Zn-doped MgP ceramics compared to 56 ± 3% for pure MgP samples. Our findings suggest that the addition of Zn in MgP ceramics alters their sintering and degradation kinetics that leads to decreased in vitro degradation, however, when Zn-doped MgP ceramics were implanted in rabbits, higher degradability was observed due to lower Mg2+ ion concentration in the degradation media.

Potential of growth factor incorporated mesoporous bioactive glass for in vivo bone regeneration.

Mesoporous bioactive glass (MBG) has drawn much attention due to its superior surface texture, porosity and bioactive characteristics. Aim of the present study is to synthesize MBG using different surfactants, viz., hexadecyltrimethylamonium(CTAB) (M1), poly-ethylene glycol (PEG) (M2) and pluronic P123 (M3); bioactivity study; and to understand their bone regeneration efficacy in combination with insulin-like growth factors (IGF-1) in animal bone defect model. SBF study revealed the formation of calcium carbonate (CaCO3) and hydroxyapatite (HAp) phase over 14 days. Formation of apatite layer was further confirmed by FTIR, FESEM and EDX analysis. M1 and M2 showed improved crystallinity, while M3 showed slightly decrease in crystalline peak of CaCO3 and enhanced HAp phase. More Ca-P layer formed in M1 and M2 supported the in vivo experiments subsequently. Degree of new bone formation for all MBGs were high, i.e., M1 (80.7 ±â€¯2.9%), M2 (74.4 ±â€¯2.4%) and M3 (70.1 ±â€¯1.9%) compared to BG (66.9 ±â€¯1.8%). In vivo results indicated that the materials were non-toxic, biodegradable, biocompatible, and is suitable as bone replacement materials. Thus, we concluded that growth factor loaded MBG is a promising candidate for bone tissue engineering application.

Mechanical and in vitro degradation behavior of magnesium-bioactive glass composites prepared by SPS for biomedical applications.

In order to make magnesium (Mg) a successful candidate for fracture fixation devices, it is imperative to control the corrosion rate and enhance its elastic modulus. In the present work, we have prepared bioactive glass (BG) reinforced magnesium composite using spark plasma sintering (SPS). Simultaneous application of heat and pressure during SPS decreased the softening point of BG (600°C), allowing it to coat the Mg particles partially. As a result, BG was found along the Mg particle boundaries, which was confirmed by elemental mapping. Addition of BG improved microhardness and elastic modulus of Mg-BG composites. Corrosion behavior was studied by hydrogen evolution and immersion corrosion in phosphate buffered saline (PBS). After 64 h of immersion, Mg-10 wt % BG composite showed highest corrosion resistance. Quantitative micro-computed tomography (micro-CT) results indicated porosity increase in Mg-BG composites during immersion. The maximum increase in porosity (1.66%) was noticed for pure Mg while the minimum for Mg-10 wt % BG composite. MG63 cell-material interactions, using extract method, showed good cytocompatibility for Mg-10 wt % BG composite. The concentration of Mg ion in cell culture media was measured using atomic absorption spectroscopy after 24 h immersion of Mg/BG composites. The results indicated that using BG as reinforcement and SPS as sintering method; we can prepare corrosion resistant and high modulus Mg-BG composites that can be used for fabricating bone fracture fixation plates. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 352-365, 2019.

Preparation and in vivo biocompatibility studies of different mesoporous bioactive glasses.

A new generation of nanostructured glasses called mesoporous bioactive glasses (MBGs) exhibit superior surface texture, porosity and bioactive characteristics. The present study is carried out to develop and detailed characterize of ternary SiO2-CaO-P2O5 MBG structure, fabricated by three different variations using different surfactants, e.g., hexadecyltrimethylammonium bromide (CTAB), poly-ethylene glycol,(PEG) and Pluronic P123. After thorough physico-chemical characterization, MBG granules were investigated for in vivo bone regeneration in animal bone defect model (rabbit) where standard S53P4 bioactive glass was used as control. All the synthesized MBG powders showed nano-range median particle size of 80-120 nm (MBG-CTAB), 50-70 nm (MBG-PEG and MBG-P123) while their specific surface area as 473.2, 52.2 and 169.3 m2/g respectively. All MBGs showed mesoporous nature corroborating transmission electron microscopy (TEM) observation as well. Bone regeneration property was measured after 45 and 90 days post-implantation at distal epiphysis of rabbit femur by radiography, histology, fluorochrome labeling, micro computed tomography (micro-CT) and vital organ histology. Results from in vivo studies indicated that the MBG materials produce minimal toxicity to the body. Furthermore, the biocompatibility and biodegradability of the implant makes them more suitable for application in bone tissue engineering. Among various implants, MBG fabricated using suitable surfactant (CTAB) shown the best result compared to other implants. Nonetheless, all the materials are suitable for application in bone tissue engineering and have potential for bone regeneration and healing.

In Vivo Biocompatibility of Zinc-Doped Magnesium Silicate Bio-Ceramics.

Magnesium-based bioceramics have emerged as a new class of biodegradable bone replacement material due to their higher degradation and good cytocompatibility. In the current research, we have prepared pure and zinc-doped magnesium silicate (MgS) bioceramics by solid state method and evaluated the in vitro degradability and in vivo biocompatibility. In vitro degradation of the MgS bioceramics was assessed in simulated body fluid (SBF) which showed enhanced degradability for 0.5 wt % Zn doped MgS samples. The in vivo biocompatibility was evaluated by implanting the samples in rabbit femur critical size defect. All the MgS samples were well-integrated at the host tissue site as evident in 90 day radiographic images and micro computed tomography (µ-CT). Oxytetracycline labeling indicated that 0.5 wt % Zn doped MgS samples had better bone regeneration after 90 days of implantation as compared to pure and 0.25 wt % Zn-doped samples. Any systemic and organ toxicity was negated by normal vital organ (heart, kidney, and liver) histology at 90 days.