Treatment of Goat Femur Segmental Defects with Silica-Coated Hydroxyapatite—One-Year Follow-Up

Utility of Chitra-HASi Granules in Cystic Defects of the Maxillofacial Region: A Pilot Study

Background:

Cystic defects that are critical sized or larger require bone replacement strategies. However, due to inherent disadvantages of the various types of grafts, none of the available materials are best suited for these defects. Among the alloplastic materials, hydroxyapatite (HA)-based grafts are the most popular, due to their osteoconductive nature and resemblance to mineral bone. The aim of the study was to assess the utility of the novel material “Chitra-HASi” as a bone substitute in the maxillofacial region.

Materials and Methods:

In a single-arm, prospective study, patients with radicular and dentigerous cysts were included and the minimum defect size was standardized at 20 × 20 mm or above. The Chitra–HASi material was developed by a wet precipitation technique and adopted for use following multiple in vitro and in vivo studies, confirming its safety and biocompatibility profile. All cysts underwent enucleation, followed by peripheral ostectomy and apicectomy of the teeth involved. The HASi graft was packed inside the cystic defect in a granular form and covered with a mucoperiosteal flap. Panoramic radiographs were taken preoperatively and at 3, 6, and 12 months postoperatively.

Results:

Twenty-three patients were included in the study, of which only 10 patients could be followed up for 12 months after graft placement. The mean preoperative bone density was found to be 14.9% ± 4.97 (standard deviation), whereas the postoperative 3-month, 6-month, and 12-month densities had a mean difference of −11.3%, −22.9%, and −37.3%, respectively, and the differences were statistically significant. Minor complications such as sinus formation (n = 7) and extrusion of granules (n = 4) were noted, which were managed conservatively. Only two patients required graft removal secondary to infection, leading to a persistent sinus tract.

Conclusion:

The results of the study suggest that Chitra–HASi granules show potential as an alternative to other bone substitutes. The addition of silica to the porous HA material offers superior strength characteristics and needs long-term evaluation to assess its stability in large cystic defects.

The Role of Three-Dimensional Scaffolds in Treating Long Bone Defects: Evidence from Preclinical and Clinical Literature-A Systematic Review

Long bone defects represent a clinical challenge. Bone tissue engineering (BTE) has been developed to overcome problems associated with conventional methods. The aim of this study was to assess the BTE strategies available in preclinical and clinical settings and the current evidence supporting this approach. A systematic literature screening was performed on PubMed database, searching for both preclinical (only on large animals) and clinical studies. The following string was used: "(Scaffold OR Implant) AND (Long bone defect OR segmental bone defect OR large bone defect OR bone loss defect)." The search retrieved a total of 1573 articles: 51 preclinical and 4 clinical studies were included. The great amount of preclinical papers published over the past few years showed promising findings in terms of radiological and histological evidence. Unfortunately, this in vivo situation is not reflected by a corresponding clinical impact, with few published papers, highly heterogeneous and with small patient populations. Several aspects should be further investigated to translate positive preclinical findings into clinical protocols: the identification of the best biomaterial, with both biological and biomechanical suitable properties, and the selection of the best choice between cells, GFs, or their combination through standardized models to be validated by randomized trials.

Graphene oxide nanoflakes incorporated gelatin-hydroxyapatite scaffolds enhance osteogenic differentiation of human mesenchymal stem cells

In this study, graphene oxide (GO) nanoflakes (0.5 and 1 wt%) were incorporated into a gelatin-hydroxyapatite (GHA) matrix through a freeze drying technique and its effect to enhance mechanical strength and osteogenic differentiation was studied. The GHA matrix with GO demonstrated less brittleness in comparison to GHA scaffolds. There was no significant difference in mechanical strength between GOGHA0.5 and GOGHA1.0 scaffolds. When the scaffolds were immersed in phosphate buffered saline (to mimic physiologic condition) for 60 days, around 50-60% of GO was released in sustained and linear manner and the concentration was within the toxicity limit as reported earlier. Further, GOGHA0.5 scaffolds were continued for cell culture experiments, wherein the scaffold induced osteogenic differentiation of human adipose derived mesenchymal stem cells without providing supplements like dexamethasone, L-ascorbic acid and β glycerophosphate in the medium. The level of osteogenic differentiation of stem cells was comparable to those cultured on GHA scaffolds with osteogenic supplements. Thus biocompatible, biodegradable and porous GO reinforced gelatin-HA 3D scaffolds may serve as a suitable candidate in promoting bone regeneration in orthopaedics.

Biocompatibility property of 100% strontium-substituted SiO2 -Al2 O3 -P2 O5 -CaO-CaF2 glass ceramics over 26 weeks implantation in rabbit model: Histology and micro-Computed Tomography analysis

One of the desired properties for any new biomaterial composition is its long-term stability in a suitable animal model and such property cannot be appropriately assessed by performing short-term implantation studies. While hydroxyapatite (HA) or bioglass coated metallic biomaterials are being investigated for in vivo biocompatibility properties, such study is not extensively being pursued for bulk glass ceramics. In view of their inherent brittle nature, the implant stability as well as impact of long-term release of metallic ions on bone regeneration have been a major concern. In this perspective, the present article reports the results of the in vivo implantation experiments carried out using 100% strontium (Sr)-substituted glass ceramics with the nominal composition of 4.5 SiO2 -3Al2 O3 -1.5P2 O5 -3SrO-2SrF2 for 26 weeks in cylindrical bone defects in rabbit model. The combination of histological and micro-computed tomography analysis provided a qualitative and quantitative understanding of the bone regeneration around the glass ceramic implants in comparison to the highly bioactive HA bioglass implants (control). The sequential polychrome labeling of bone during in vivo osseointegration using three fluorochromes followed by fluorescence microscopy observation confirmed homogeneous bone formation around the test implants. The results of the present study unequivocally confirm the long-term implant stability as well as osteoconductive property of 100% Sr-substituted glass ceramics, which is comparable to that of a known bioactive implant, that is, HA-based bioglass.

Triphasic ceramic scaffold in paediatric and adolescent bone defects

We evaluated novel triphasic hydroxyapatite tricalcium phosphate calcium silicate scaffold (HASi) in the management of paediatric bone defects. Their main advantage is considered to be adequate strength and stimulation of bone formation without resorting to autograft. A total of 42 children younger than 16 years of age were recruited over a period of 1 year and were treated with this synthetic bone substitute as a stand-alone graft for pelvic, femur, calcaneal and ulnar osteotomies, cystic bone lesions, subtalar arthrodesis and segmental bone defects. Forty children, 22 boys and 18 girls, mean age 8.3 years and a mean follow-up of 18.51 months, were available for evaluation. Analysis showed that younger age, cancellous defects and no internal fixation were associated with significantly faster healing. Partial incorporation was observed in 22.5% and complete incorporation in 77.5% of cases at 18 months of follow-up. Sex, type of defect, BMI and the shape of the ceramic graft did not significantly affect the rate of healing. Complications attributable to HASi included four nonunions, three of which were diaphyseal. HASi was found to be safe in children with cancellous or benign cavitatory defects. It is not suitable for diaphyseal and segmental bone defects as a stand-alone graft.

Assessing the repair of critical size bone defects performed in a goat tibia model using tissue-engineered constructs cultured in a bidirectional flow perfusion bioreactor

This work evaluated in vivo performance of a tissue-engineered bone-like matrix obtained by culturing cell-scaffold constructs in a flow perfusion bioreactor, designed to enable culture of large constructs, envisioning the regeneration of critical-sized defects. A blend of starch with polycaprolactone scaffolds was seeded with goat bone marrow stromal cells (GBMSCs) cultured in the perfusion bioreactor for 14 days using osteogenic medium. Cell seeded scaffolds cultured in static conditions acted as controls. After 14 days, constructs (42 mm length and 16 mm in diameter) were implanted in critical size defects performed in the tibial bone of six adult goats from which the bone marrow had been collected previously. Explants were retrieved after six and 12 weeks of implantation and characterized using scanning electron microscopy, energy-dispersive spectroscopy, micro-computed tomography and radiographic analysis to assess tissue morphology and calcification. Explants were histologically analyzed, using Hematoxylin & Eosin and Masson Trichrome staining. Results provided relevant information about the performance and functionality of starch with polycaprolactone-goat bone marrow stromal cell constructs in a critical size orthotopic defect performed in a large animal model and demonstrated that culture of the starch with polycaprolactone scaffolds with the autologous cells in perfusion culture provide a good therapy for the healing and regenerative process of bone defects.

Early osseointegration of a strontium containing glass ceramic in a rabbit model

The most important property of a bone cement or a bone substitute in load bearing orthopaedic implants is good integration with host bone with reduced bone resorption and increased bone regeneration at the implant interface. Long term implantation of metal-based joint replacements often results in corrosion and particle release, initiating chronic inflammation leading onto osteoporosis of host bone. An alternative solution is the coating of metal implants with hydroxyapatite (HA) or bioglass or the use of bulk bioglass or HA-based composites. In the above perspective, the present study reports the in vivo biocompatibility and bone healing of the strontium (Sr)-stabilized bulk glass ceramics with the nominal composition of 4.5SiO2-3Al2O3-1.5P2O5-3SrO-2SrF2 during short term implantation of up to 12 weeks in rabbit animal model. The progression of healing and bone regeneration was qualitatively and quantitatively assessed using fluorescence microscopy, histological analysis and micro-computed tomography. The overall assessment of the present study establishes that the investigated glass ceramic is biocompatible in vivo with regards to local effects after short term implantation in rabbit animal model. Excellent healing was observed, which is comparable to that seen in response to a commercially available implant of HA-based bioglass alone.

Pulsed laser deposition and in vitro characteristics of triphasic – HASi composition on titanium

Pulsed laser deposition was used to deposit bioactive triphasic glass-ceramic composition (HASi) over titanium substrate using dense HASi target. Bioactive glass compositions are considered the most useful synthetic materials for immediate bone attachment because of its bioresorption, osteoconduction and osteointegration characteristics under in vivo conditions. The disadvantage of its brittleness associated with bioactive glass-ceramics has prompted its coating over metallic implants for the combination of duo mechanical and bioactive properties. The hard HASi target was able to undergo laser ablation under ambient gas pressure without bulk erosion of the target. Laser deposition was found to be efficient in depositing triphasic composition for immediate bone integration. The target and deposits were analyzed for the phase, composition and microstructural characteristics by means of X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis and scanning electron microscopy. Simultaneously, the adherent nature and mechanical behaviour of deposits were confirmed by scratch test and micro-indentation methods. Further, the in vitro dissolution and bioactivity were assessed by soaking in simulated body fluid followed by elemental analysis using inductively coupled plasma spectroscopy. The deposits were found to be cell-friendly, which was indicated by the phenomenology of stem cells under in vitro conditions.

Bioactive starch-based scaffolds and human adipose stem cells are a good combination for bone tissue engineering

Silicon is known to have an influence on calcium phosphate deposition and on the differentiation of bone precursor cells. This study explores the effect of the incorporation of silanol (Si-OH) groups into polymeric scaffolds on the osteogenic differentiation of human adipose stem cells (hASC) cultured under dynamic and static conditions. A blend of corn starch with polycaprolactone (30/70 wt.%, SPCL) was used to produce three-dimensional fibre meshes scaffolds by the wet-spinning technique, and a calcium silicate solution was used as a non-solvent to develop an in situ functionalization with Si-OH groups. In vitro assessment, using hASC, of functionalized and non-functionalized scaffolds was evaluated in either α-MEM or osteogenic medium under static and dynamic conditions (provided by a flow perfusion bioreactor). The functionalized materials, SPCL-Si, exhibit the capacity to sustain cell proliferation and induce their differentiation into the osteogenic lineage. The formation of mineralization nodules was observed in cells cultured on the SPCL-Si materials. Culturing under dynamic conditions using a flow perfusion bioreactor was shown to enhance the hASC proliferation and differentiation and a better distribution of cells within the material. The present work demonstrates the potential of these functionalized materials for future applications in bone tissue engineering. Additionally, these results highlight the simplicity, economic and reliable production process of those materials.