Biphasic, triphasic and multiphasic calcium orthophosphates

Chitosan-Oligosaccharide-Bearing Biphasic Calcium Phosphate Bone Cement: Preparation and Angiogenic Activity In Vitro

Although calcium phosphate bone cement has some advantages (it is easy to form, self-curing, and does not produce heat), some disadvantages remain that limit its clinical application. Therefore, the question of how we can modify CPC and further improve the various properties of calcium phosphate bone cement is a current research hotspot. In this paper, the preparation conditions and technology of biphasic calcium phosphate (BCP) were optimized; chitosan oligosaccharide (COSM) with MW ≤ 3000 Da was added to the optimal formulation of biphasic calcium phosphate cement particles, and its physical and chemical properties were characterized. The results showed that BCP bone cement carrier for clinical operations was successfully constructed by the high-temperature solid-state reaction method, and COSM-BCP bone cement particles were obtained by loading COSM drugs with an angiogenesis effect. Its formula is biphasic calcium phosphate powder with the molar ratio of α-TCP/β-TCP of 1. The curing time of the prepared BCP particles is 24 ± 1 min, the compressive strength is 29.58 ± 1.89 MPa, and the porosity reaches 52.09%. The loaded COSM can be released continuously and stably in vitro, and has the effect of promoting angiogenesis. The safety evaluation of COSM-BCP bone cement particles and the preliminary pharmacodynamic study of its angiogenesis in vitro provide a promising clinical application basis for the development of drug-loaded biological bone substitute materials.

Calcium Phosphate Apatite Filament Co-Wrapped With Perforated Electrospun Sheet of Phosphorylated Chitosan-A Bioinspired Approach Toward Bone Graft Substitute

Bioinspired bone graft substitutes hold incredible opportunities in tissue engineering, potentiating the healing aspect. Here we have fabricated stacks of glutaraldehyde-genipin crosslinked, microporous nanofibrous N-methyl phosphonic chitosan sheets (NMPC) with impregnated eggshell-derived CaP fibers to mimic osteonal architecture. This composite 3D rolled eggshell-derived calcium phosphate (ESCAP) scaffold (RCS), with density and modulus variation from the center to the periphery, has superior mechanical strength. The zwitterionic nature of NMPC, following the surface modulus of the CaP fibers, upgraded the biological performance. The low modulus of the flexible micro-perforated nanofibrous sheet increases along the ceramic phase, which prompts migration and distribution of proliferated MSCs from the outer polymeric surface to the inner ceramic region through micro-perforations. This movement stimulates endochondral ossification, observed by a gradual increment of collagen II expression alongside a decrement of collagen I expression. In vivo assessment of rabbit tibia bone defects revealed prominent healing in the presence of a scaffold by Day 60, accompanied by scaffold resorption. The cellular activity during healing revealed osteoblasts, osteocytes, blood vessels, and chondroblast cells at the boundary of the scaffolds, indicating neotissue and hypertrophic cartilage formation. Thus, the RCS bone grafts promote faster bone healing by osteogenesis and bone remodeling.

Evolution in Bone Tissue Regeneration: From Grafts to Innovative Biomaterials

Bone defects caused by various traumas and diseases such as osteoporosis, which affects bone density, and osteosarcoma, which affects the integrity of bone structure, are now well known. Given this situation, several innovative research projects have been reported to improve orthopedic methods and technologies that positively contribute to the regeneration of affected bone tissue, representing a significant advance in regenerative medicine. This review article comprehensively analyzes the transition from existing methods and technologies for implants and bone tissue regeneration to innovative biomaterials. These biomaterials have been of great interest in the last decade due to their physicochemical characteristics, which allow them to overcome the most common limitations of traditional grafting methods, such as the availability of biomaterials and the risk of rejection after their application in regenerative medicine. This could be achieved through an exhaustive study of the applications and properties of various materials with potential applications in regenerative medicine, such as using magnetic nanoparticles and hydrogels sensitive to external stimuli, including pH and temperature. In this regard, this review article describes the most relevant compounds used in bone tissue regeneration, promoting the integration of these biomaterials with the affected area's bone structure, thereby allowing for regeneration and preventing amputation. Additionally, the types of interactions between biomaterials and mesenchymal stem cells and their effects on bone tissue are discussed, which is critical for developing biomaterials with optimal regenerative properties. Furthermore, the mechanisms of action of the various biomaterials that enhance osteoconduction and osteoinduction, ensuring the success of orthopedic therapies, are analyzed. This enables the treatment of bone defects tailored to each patient's condition, thereby avoiding limb amputation. Consequently, a promising future for regenerative medicine is emerging, with various therapies that could revolutionize the management of bone defects, offering more efficient and safer solutions.

Dynamic ion-releasing biomaterials actively shape the microenvironment to enhance healing

Dynamic ion-releasing biomaterials have redefined the role of implantable bone devices, transitioning them from passive mechanical support to active players in tissue regeneration. These materials actively modulate the surrounding biological microenvironment by releasing bioactive ions (e.g.: calcium, phosphate, and cobalt) which dynamically interact with cells and tissues surrounding them. This interaction becomes the microenvironment highly active and accelerates bone healing, promoting osteogenesis, and enhancing osseointegration. The ions modulate key biological processes in this regard, including osteoblast adhesion, proliferation, differentiation, angiogenesis, and immune responses, as well as coupled physiological mechanisms, ensuring that the implanted biomaterials foster an optimal environment for bone regeneration. More advanced surface modifications onto materials (e.g.: nanostructuring hydroxyapatites coatings) have been shown to further boost ion release, amplifying the ability of the material to influence surrounding tissues. As a result, ion-releasing biomaterials not only improve implant integration but also accelerate the overall healing process. Looking forward, the development of smart biomaterials capable of adjusting ion release in response to environmental changes offers exciting possibilities for personalized regenerative therapies and this review provides a comprehensive understanding of how dynamic ion-releasing biomaterials actively shape the microenvironment to enhance healing, focusing on their ability to modulate biological processes such as osteogenesis and angiogenesis. By examining the latest advances in surface modifications and ion-release mechanisms, this review also aims to revise the potential of these materials to revolutionize regenerative medicine, offering knowledge to guide the development of next-generation biomaterials for improved clinical outcomes.

Effect of Tricalcium Phosphate Foam and Paste Bone Grafting Materials Designed for Improved Surgical Handling on Osteogenesis in a Sheep Scapula Model

Reconstruction of critical-size bone defects (CSDs) with complex defect morphologies remains clinically challenging. The desire to avoid autograft harvesting has prompted an increasing quest for adequate synthetic bone grafting materials. The clinical success rates, which have been achieved with bioactive β-tricalcium phosphate granules (TCP-G) demonstrate that these materials have become an excellent alternative graft choice. In order to improve surgical handling properties, TCP-G have been combined with natural polymers for creating paste- and foam-like materials, which can easily be molded into any desired shape when grafting a given bony defect or deploying them with a syringe. This study assessed the effect of a TCP paste (TCP-P) and a TCP-foam (TCP-F) bone grafting material as compared to TCP-G on bone formation and osteogenic marker expression after 1, 3, 6, 12, and 18 months of implantation in CSD in the sheep scapula and tested the hypothesis that the addition of natural polymers would not diminish the osteogenic properties of TCP-P and TCP-F. The bone and bone graft material area fractions were determined histomorphometrically in order to quantify bone formation and bone graft material resorption. Immunohistochemical analysis of collagen type I, osteocalcin, and bone sialoprotein expression in the various cell and matrix components of the bone tissue was performed on resin-embedded sections for characterizing the osteogenic and bioactive properties of the test materials. By 6 months, all three TCP materials facilitated excellent defect regeneration with further bone remodeling at 12 and 18 months. TCP-F and TCP-P induced greater osteocalcin expression and exhibited more advanced graft material resorption at 1 and 6 months, respectively. At 18 months, all three grafting materials were almost fully resorbed with the original bony architecture being restored. Taken together, the hyaluronic acid and methylcellulose components in TCP-P and porcine collagen components in TCP-F did not diminish the osteogenic capacity of TCP-P and TCP-F, which exhibited an even slightly higher resorbability and enhancement effect on OC expression by osteoblasts.

Mechanical Properties and Decomposition Behavior of Compression Moldable Poly(Malic Acid)/α-Tricalcium Phosphate Hybrid Materials

Calcified tissues in living organisms, such as bone, dentin, and enamel, often require surgical intervention for treatment. However, advances in regenerative medicine have increased the demand for materials to assist in regenerating these tissues. Among the various forms of calcium phosphate (CaP), tricalcium phosphate (TCP)-particularly its α-TCP form-stands out due to its high solubility and efficient calcium release, making it a promising candidate for bone regeneration applications. Nevertheless, its rapid dissolution rate presents challenges when used as a reinforcing agent. In this study, we developed a hybrid material composed of poly(malic acid) (PMA) and α-TCP to achieve controlled calcium release while maintaining mechanical strength. The hybrid materials were prepared using a compression molding method optimized to suppress the hydrolysis of PMA. The bond between the carboxyl group of PMA and α-TCP was confirmed through infrared (IR) spectroscopy. A calcium release test demonstrated that the interaction between PMA and α-TCP extends the dissolution period of both components. These findings indicate that PMA/α-TCP hybrid materials have significant potential for applications in bone tissue engineering.

Fabrication of In Situ-Cross-Linked N-Succinyl Chitosan/Oxidized Alginate Hydrogel-Loaded Ascorbic Acid and Biphasic Calcium Phosphate for Bone Tissue Engineering

Bone tissue engineering is a promising technology being studied globally to become an effective and sustainable method to treat the problems of damaged or diseased bones. In this work, we developed an in situ cross-linking hydrogel system that combined N-succinyl chitosan (NSC) and oxidized alginate (OA) at varying mixing ratios through Schiff base cross-linking. The hydrogel system also contains biphasic calcium phosphate (BCP) and ascorbic acid (AA), which could enhance biological characteristics and accelerate bone repair. The hydrogels' properties were examined through physicochemical tests such as scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD), pore size and porosity measurement, swelling ratio, degradation rate, AA release study, as well as cytocompatibility, including live/dead and cytotoxicity assays. The results revealed that the supplementation of AA and BCP components can affect the physico-mechanical properties of the hydrogel system. However, they exhibited noncytotoxic properties. Overall, the results demonstrated that the hydrogel composed of 3% (w/v) NSC and 3% (w/v) OA (NSC: OA volume ratio is 8:2) loaded with 40% (w/w) BCP and 0.3 mg/mL AA has the potential for bone regeneration.

Calcium phosphate complex of recombinant human thrombomodulin promote bone formation in interbody fusion

Interbody fusion is an orthopedic surgical procedure to connect two adjacent vertebrae in patients suffering from spinal disc disease. The combination of synthetic bone grafts with protein-based drugs is an intriguing approach to stimulate interbody bone growth, specifically in patients exhibiting restricted bone progression. Recombinant human thrombomodulin (rhTM), a novel protein drug characterized by its superior stability and potency, shows promise in enhancing bone formation. A composite bone graft, termed CaP-rhTM, has been synthesized, combining calcium phosphate (CaP) microparticles as a delivery vehicle for rhTM to facilitate interbody fusion.In vitrostudies have demonstrated that rhTM significantly promotes the proliferation and maturation of preosteoblasts at nanogram dosage, while exerting minimal impact on osteosarcoma cell growth. The expression levels of mature osteoblast markers, including osteocalcin, osteopontin, alkaline phosphatase, and calcium deposition were also enhanced by rhTM. In rat caudal disc model of interbody fusion, CaP-rhTM with 800 ng of drug dosage was implanted along with a polylactic acid cage, to ensure structural stability within the intervertebral space. Microcomputed tomography analyses revealed that from 8 to 24 weeks, CaP-rhTM substantially improves both bone volume and trabecular architecture, in addition to the textural integrity of bony endplate surfaces. Histological examination confirmed the formation of a continuous bone bridge connecting adjacent vertebrae. Furthermore, biomechanical assessment via three-point bending tests indicated an improved bone quality of the fused disc. This study has demostrated that rhTM exhibits considerable potential in promoting osteogenesis. The use of CaP-rhTM has also shown significant improvements in promoting interbody fusion.

LL-37 and bisphosphonate co-delivery 3D-scaffold with antimicrobial and antiresorptive activities for bone regeneration

This study introduces a novel 3D scaffold for bone regeneration, composed of silk fibroin, chitosan, nano-hydroxyapatite, LL-37 antimicrobial peptide, and pamidronate. The scaffold addresses a critical need in bone tissue engineering by simultaneously combating bone infections and promoting bone growth. LL-37 was incorporated for its broad-spectrum antimicrobial properties, while pamidronate was included to inhibit bone resorption. The scaffold's porous structure, essential for cell infiltration and nutrient diffusion, was achieved through a freeze-drying process. In vitro assessments using SEM and FTIR confirmed the scaffold's morphology and chemical integrity. Antimicrobial efficacy was tested against pathogens of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). In vivo studies in a murine model of infectious bone defect revealed the scaffold's effectiveness in reducing inflammation and bacterial load, and promoting bone regeneration. RNA sequencing of treated specimens provided insights into the molecular mechanisms underlying these observations, revealing significant gene expression changes related to bone healing and immune response modulation. The results indicate that the scaffold effectively inhibits bacterial growth and supports bone cell functions, making it a promising candidate for treating infectious bone defects. Future studies should focus on optimizing the release of therapeutic agents and evaluating the scaffold's clinical potential.

Bovine hydroxyapatite/3Y-TZP bioceramic: Aligning 3Y-TZP content with sintering parameters

This study aimed to produces and characterize bovine hydroxyapatite (HA) bioceramic with 3Y-TZP addition and analyze different sintering curves. HA was extracted from bovine bones and nanoparticulated. HA discs (0, 1, 5 and 10 wt% 3Y-TZP) were subjected to uniaxial and isostatic pressing. Dilatometry analysis was performed and the groups were sintered using 3 different firing curves (conventional, 1300 °C; 2-step, 1292 °C; 2-step, 1420 °C). The samples were analyzed by X-ray diffraction (XRD), biaxial flexural strength (BFS), Vickers microhardness (VH) and Field emission scanning electron microscopy (FE-SEM). The dilatometry results signaled the need for sintering optimization in groups added with 3Y-TZP. XRD demonstrated the characteristic crystallographic peaks of HA in the pure groups and with 1% 3Y-TZP, and decomposition of HA into β-TCP and formation of calcium zirconate in the groups with 5 and 10% 3Y-TZP. Considering each composition, the groups of pure HA (131.3 ± 13.5 MPa; 401 ± 12.7 GPa) sintered by the conventional curve and HA+1%3Y-TZP (145 ± 8.6 MPa; 507 ± 47.9 GPa), HA+5%3Y-TZP (68.1 ± 14.2 MPa; 183 ± 9.8 GPa) and HA+10%3Y-TZP (55.6 ± 5.1 MPa; 96.1 ± 7.64 GPa) sintered by the 2-step curve at 1420 °C, combined the best BFS and VH results. The addition of 1 wt% 3Y-TZP and optimization in the sintering process improved the mechanical and microstructural properties of HA bioceramics and maintenance of its crystalline characteristics. Refinement in material processing is necessary for the future use of this bioceramic in dentistry.

Cuttlefish Bone-Derived Calcium Phosphate Bioceramics Have Enhanced Osteogenic Properties

Cuttlefish bones are byproducts of cuttlefish processing and are readily available in the marine food industry. In this study, calcium phosphate bioceramics were prepared from cuttlefish bones using a two-stage hydrothermal calcination process. The results indicated that all bioceramics derived from cuttlefish bones had a higher degradation capacity, better bone-like apatite formation ability, and higher degree of osteogenic differentiation than commercially available hydroxyapatite. Notably, β-tricalcium phosphate, which had the highest degree of Ca2+ and Sr2+ dissolution among the bioceramics extracted, can significantly upregulate osteogenic markers (alkaline phosphatase, osteocalcin) and stimulate bone matrix mineralization. Thus, it is a promising bioceramic material for applications in bone regeneration.

Bioactive ceramic-based materials: beneficial properties and potential applications in dental repair and regeneration

Bioactive ceramics, primarily consisting of bioactive glasses, glass-ceramics, calcium orthophosphate ceramics, calcium silicate ceramics and calcium carbonate ceramics, have received great attention in the past decades given their biocompatible nature and excellent bioactivity in stimulating cell proliferation, differentiation and tissue regeneration. Recent studies have tried to combine bioactive ceramics with bioactive ions, polymers, bioactive proteins and other chemicals to improve their mechanical and biological properties, thus rendering them more valid in tissue engineering scaffolds. This review presents the beneficial properties and potential applications of bioactive ceramic-based materials in dentistry, particularly in the repair and regeneration of dental hard tissue, pulp-dentin complex, periodontal tissue and bone tissue. Moreover, greater insights into the mechanisms of bioactive ceramics and the development of ceramic-based materials are provided.

Magnetic Hydroxyapatite-Coated Iron-Chromium Microspheres for Dental Surface Polishing and Plaque Removal

This research aimed to engineer magnetic hydroxyapatite-coated iron-chromium (HAp-FeCr) microspheres to enhance dental surface polishing and plaque elimination. Utilizing a tailored sol-gel approach, the HAp-FeCr microspheres were synthesized and exhaustively characterized via scanning electron microscopy, energy-dispersive X-ray spectroscopy, ζ-potential, X-ray diffractometry, and X-ray photoelectron spectroscopy methodologies. Key findings showcased that these microspheres retained their magnetic properties post-HAp coating, as evidenced by the magnetization curves. An innovative magnetic polishing system was developed, incorporating these microspheres and a 2000 rpm magnet. Comparative evaluations between traditional air-powder polishing and the proposed magnetic technique demonstrated the latter's superiority. Notably, the magnetic polishing led to a substantial reduction in dental plaque on the tooth surface, decreasing bacterial adhesion and early biofilm formation by Streptococcus gordonii and Lactobacillus acidophilus, where the most pronounced effects were observed in samples with elevated HAp content. A significant 60% reduction in dental plaque was achieved with the magnetic method relative to air-powder polishing. Furthermore, the HAp-FeCr microspheres' biocompatibility was verified through cytotoxicity tests and animal studies. In essence, the magnetic HAp-FeCr microspheres present a novel and efficient strategy for dental treatments, holding immense potential for improving oral health.

Scaffolds for Dentin-Pulp Complex Regeneration

Background and Objectives: Regenerative dentistry aims to regenerate the pulp-dentin complex and restore those of its functions that have become compromised by pulp injury and/or inflammation. Scaffold-based techniques are a regeneration strategy that replicate a biological environment by utilizing a suitable scaffold, which is considered crucial for the successful regeneration of dental pulp. The aim of the present review is to address the main characteristics of the different scaffolds, as well as their application in dentin-pulp complex regeneration. Materials and Methods: A narrative review was conducted by two independent reviewers to answer the research question: What type of scaffolds can be used in dentin-pulp complex regeneration? An electronic search of PubMed, EMBASE and Cochrane library databases was undertaken. Keywords including "pulp-dentin regeneration scaffold" and "pulp-dentin complex regeneration" were used. To locate additional reports, reference mining of the identified papers was undertaken. Results: A wide variety of biomaterials is already available for tissue engineering and can be broadly categorized into two groups: (i) natural, and (ii) synthetic, scaffolds. Natural scaffolds often contain bioactive molecules, growth factors, and signaling cues that can positively influence cell behavior. These signaling molecules can promote specific cellular responses, such as cell proliferation and differentiation, crucial for effective tissue regeneration. Synthetic scaffolds offer flexibility in design and can be tailored to meet specific requirements, such as size, shape, and mechanical properties. Moreover, they can be functionalized with bioactive molecules, growth factors, or signaling cues to enhance their biological properties and the manufacturing process can be standardized, ensuring consistent quality for widespread clinical use. Conclusions: There is still a lack of evidence to determine the optimal scaffold composition that meets the specific requirements and complexities needed for effectively promoting dental pulp tissue engineering and achieving successful clinical outcomes.

Oxygen-Deficient Bioceramics: Combination of Diagnosis, Therapy, and Regeneration

The journey of ceramics in medicine has been synchronized with an evolution from the first generation-alumina, zirconia, etc.-to the third -3D scaffolds. There is an up-and-coming member called oxygen-deficient or colored bioceramics, which have recently found their way through biomedical applications. The oxygen vacancy steers the light absorption toward visible and near infrared regions, making the colored bioceramics multifunctional-therapeutic, diagnostic, and regenerative. Oxygen-deficient bioceramics are capable of turning light into heat and reactive oxygen species for photothermal and photodynamic therapies, respectively, and concomitantly yield infrared and photoacoustic images. Different types of oxygen-deficient bioceramics have been recently developed through various synthesis routes. Some of them like TiO2- x , MoO3- x , and WOx have been more investigated for biomedical applications, whereas the rest have yet to be scrutinized. The most prominent advantage of these bioceramics over the other biomaterials is their multifunctionality endowed with a change in the microstructure. There are some challenges ahead of this category discussed at the end of the present review. By shedding light on this recently born bioceramics subcategory, it is believed that the field will undergo a big step further as these platforms are naturally multifunctional.

Formation of Hydroxyapatite-Based Hybrid Materials in the Presence of Platelet-Poor Plasma Additive

Biomaterials based on hydroxyapatite with controllable composition and properties are promising in the field of regenerative bone replacement. One approach to regulate the phase composition of the materials is the introduction of biopolymer-based additives into the synthesis process. The purpose of present study was to investigate the formation of hydroxyapatite-based hybrid materials in the presence of 6-24% platelet-poor plasma (PPP) additive, at a [Ca2+]/[PO43-] ratio of 1.67, pH 11, and varying maturing time from 4 to 9 days. The mineral component of the materials comprised 53% hydroxyapatite/47% amorphous calcium phosphate after 4 days of maturation and 100% hydroxyapatite after 9 days of maturation. Varying the PPP content between 6% and 24% brought about the formation of materials with rather defined contents of amorphous calcium phosphate and biopolymer component and the desired morphology, ranging from typical apatitic conglomerates to hybrid apatite-biopolymer fibers. The co-precipitated hybrid materials based on hydroxyapatite, amorphous calcium phosphate, and PPP additive exhibited increased solubility in SBF solution, which defines their applicability for repairing rhinoplastic defects.

Properties of Coatings Based on Calcium Phosphate and Their Effect on Cytocompatibility and Bioactivity of Titanium Nickelide

Coatings based on calcium phosphate with thicknesses of 0.5 and 2 μm were obtained by high-frequency magnetron sputtering on NiTi substrates in an argon atmosphere. The coating was characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, and in vitro cytocompatibility and bioactivity studies. A biphasic coating of tricalcium phosphate (Ca₃(PO₄)₂) and hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) with a 100% degree of crystallinity was formed on the surface. The layer enriched in calcium, phosphorus, and oxygen was observed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Scanning electron microscopy showed that the surface structure is homogeneous without visible defects. The 2 µm thick coating obtained by sputtering with a deposition time of 4 h and a deposition rate of 0.43 µm/h is uniform, contains the highest amount of the calcium phosphate phase, and is most suitable for the faster growth of cells and accelerated formation of apatite layers. Samples with calcium phosphate coatings do not cause hemolysis and have a low cytotoxicity index. The results of immersion in a solution simulating body fluid show that NiTi with the biphasic coating promotes apatite growth, which is beneficial for biological activity.

Biomimetic Growth of Hydroxyapatite in Hybrid Polycaprolactone/Graphene Oxide Ultra-Porous Scaffolds

This paper reports the preparation and characterization of hybrid scaffolds composed of polycaprolactone (PCL) and different graphene oxide (GO) amounts, intending to incorporate the intrinsic characteristics of their constituents, such as bioactivity and biocidal effect. These materials were fabricated by a solvent-casting/particulate leaching technique showing a bimodal porosity (macro and micro) that was around 90%. The highly interconnected scaffolds were immersed in a simulated body fluid, promoting the growth of a hydroxyapatite (HAp) layer, making them ideal candidates for bone tissue engineering. The growth kinetics of the HAp layer was influenced by the GO content, a remarkable result. Furthermore, as expected, the addition of GO neither significantly improves nor reduces the compressive modulus of PCL scaffolds. The thermal behavior of composites was investigated by differential scanning calorimetry, showing an increase in crystallinity as the addition of GO raised, which implies that GO nanosheets can act as seeds to induce the crystallization of PCL. The improved bioactivity was demonstrated by the deposition of an HAp layer on the surface of the scaffold with GO, especially with a 0.1% GO content.

New N- and C-modified RGD-hemorphins as potential biomedical application on Ti-surface materials: synthesis, characterization and antinociceptive activity

This manuscript presented the synthesis and characterization of two new N- and C-modified analogues of VV-hemorphin-7 containing RGD (Arg-Gly-Asp) residues as potential nociceptive agents and bioactive materials. It has been shown that the addition of one or two RGD sequences to natural VV-hemorphin-7 increases its effect on acute nociception, but the reduction of the inflammatory phase depends on the concentration of the peptide. The structure-property relationship of the new peptide derivatives was highlighted by electrochemical and FT-IR methods of analysis. Because of the proven bone-structural bonds of hydroxyapatite, the simultaneous deposition of peptide/hydroxyapatite on the surface of a titanium surface was investigated. The deposition was performed in a medium of gelatin solution containing dissolved amounts of peptide and hydroxyapatite using ultrasound. SEM-EDS analyzes confirmed the presence of a layer of the studied system.

Hydroxyapatite-bioglass nanocomposites: Structural, mechanical, and biological aspects

This research work focuses on the fabrication and study of a series of nanocomposites consisting of two types of hydroxyapatite (HA), obtained by precipitate (HAP) and sol-gel (HAG) methods, and a boro-silico-phosphate bioglass. The microstructure and chemical, mechanical, and biological properties as functions of three factors, namely (i) the type of hydroxyapatite, (ii) glass content, and (iii) sintering temperature, were investigated. It was found that all of these factors affect the final composition and microstructure, especially, porosity, which shows significantly lower values for HAP-based composites than for HAG-based ones and higher values for higher glass content. This, in turn, has an impact on the microhardness, which exhibits a strong correlation with porosity, as well as on the mineralization capability and cell viability due to the different dissolution rate.

Molecular Dynamics Simulation of Biomimetic Biphasic Calcium Phosphate Nanoparticles

Biphasic calcium phosphate (BCP) is used as a bone substitute and bone tissue repair material due to its better control over bioactivity and biodegradability. It is crucial to stabilize the implanted biomaterial while promoting bone ingrowth. However, a lack of standard experimental and theoretical protocols to characterize the physicochemical properties of BCP limits the optimization of its composition and properties. Computational simulations can help us better to learn BCP at a nanoscale level. Here, the Voronoi tessellation method was combined with simulated annealing molecular dynamics to construct BCP nanoparticle models of different sizes, which were used to understand the physicochemical properties of BCP (e.g., melting point, infrared spectrum, and mechanical properties). We observed a ∼20 to 30 Å layer of calcium-deficient hydroxyapatite at the HAP/β-TCP interface due to particle migration, which may contribute to BCP stability. The BCP model may stimulate further research into BCP ceramics and multiphasic ceramics. Moreover, our study may facilitate the optimization of compositions of BCP-based biomaterials.

Phosphorus biogeochemistry regulated by carbonates in soil

Phosphates are the dominant phosphorus (P) source on Earth. The phosphates govern available P in soil, or even the complete ecosystem. The common deficiency of available P in carbonate-enriched soils suggests the tight correlation between P and C biogeochemistry, although the two elements have diverse abundance in soil. The influences of carbonates on P cycle were reviewed in this study, via both abiotic and biotic pathways. The abiotic processes at geochemical scale include element release, transport, sorption, desorption, weathering, precipitation, etc. The sorption of P on carbonate and buffering ability of carbonates were particularly addressed. Biotic factors are ascribed to various microorganisms in soil. As the most active P pool in soil, microorganisms prefer to consume abundant P, and then accumulate it in their biomass. Carbonates, however, are usually utilized by microorganisms after conversion to organic C. Meanwhile, extracellular precipitation of Ca-P phases significantly regulates the transportation of P in/out the cells. Moreover, they boost and complexify both carbonates and P turnover in soil via bioweathering and biomineralization, i.e., the intense interactions between biosphere and lithosphere. Based on this review, we proposed that carbonates may negatively affect P supply in soil system. This comprehensive review regarding the regulation by carbonates on P biogeochemistry would shed a light on predicting long-term P availability influenced by C biogeochemistry.

Calcium Phosphate-Based Biomaterials for Bone Repair

Traumatic, tumoral, and infectious bone defects are common in clinics, and create a big burden on patient's families and society. Calcium phosphate (CaP)-based biomaterials have superior properties and have been widely used for bone defect repair, due to their similarities to the inorganic components of human bones. The biological performance of CaPs, as a determining factor for their applications, are dependent on their physicochemical properties. Hydroxyapatite (HAP) as the most thermally stable crystalline phase of CaP is mostly used in the form of ceramics or composites scaffolds with polymers. Nanostructured CaPs with large surface areas are suitable for drug/gene delivery systems. Additionally, CaP scaffolds with hierarchical nano-/microstructures have demonstrated excellent ability in promoting bone regeneration. This review focuses on the relationships and interactions between the physicochemical/biological properties of CaP biomaterials and their species, sizes, and morphologies in bone regeneration, including synthesis strategies, structure control, biological behavior, and the mechanisms of CaP in promoting osteogenesis. This review will be helpful for scientists and engineers to further understand CaP-based biomaterials (CaPs), and be useful in developing new high-performance biomaterials for bone repair.

Simultaneous Substitution of Fe and Sr in Beta-Tricalcium Phosphate: Synthesis, Structural, Magnetic, Degradation, and Cell Adhesion Properties

β-tricalcium phosphate is a promising bone graft substitute material with biocompatibility and high osteoinductivity. However, research on the ideal degradation and absorption for better clinical application remains a challenge. Now, we focus on modifying physicochemical properties and improving biological properties through essential ion co-substitution (Fe and Sr) in β-TCPs. Fe- and Sr-substituted and Fe/Sr co-substituted β-TCP were synthesized by aqueous co-precipitation with substitution levels ranging from 0.2 to 1.0 mol%. The β-TCP phase was detected by X-ray diffraction and Fourier transform infrared spectroscopy. Changes in Ca–O and P–O bond lengths of the co-substituted samples were observed through X-ray photoelectron spectroscopy. The results of VSM represent the M-H graph having a combination of diamagnetic and ferromagnetic properties. A TRIS–HCl solution immersion test showed that the degradation and resorption functions act synergistically on the surface of the co-substituted sample. Cell adhesion tests demonstrated that Fe enhances the initial adhesion and proliferation behavior of hDPSCs. The present work suggests that Fe and Sr co-substitution in β-TCP can be a candidate for promising bone graft materials in tissue engineering fields. In addition, the possibility of application of hyperthermia for cancer treatment can be expected.

Apatitic calcium phosphate /montmorillonite nano-biocomposite: in-situ synthesis, characterization and dissolution properties

Recently, calcium phosphate/montmorillonite composites have received attention as a synthetic bone substitutes. In this study, apatitic calcium phosphate/Montmorillonite nano-biocomposites were in-situ synthesized at 22 °C by reaction between calcium hydroxide and orthophosphoric acid in the presence of different contents of montmorillonite (MNa). Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Brunauer–Emmett–Teller (BET) surface areas were used to characterize the prepared powders. The XRD results show that the composites prepared with 2 and 5 wt% MNa and sintered at 900 °C, show the formation of hydroxyapatite (HAP) structure, whereas that prepared with 10 wt% MNa leads to the formation of β-tricalcium phosphate (β-TCP) structure. The HAP structure decomposes at 1000 °C and leads to the formation of biocomposite containing HAP, β and α-TCP. However, β-TCP composites show thermal stability. FTIR and structural refinement results show the incorporation of clay ions into the apatitic structure causing changes in the crystal structure of the formed calcium phosphate phases. The changes in the composition and structure lead to an increase in the dissolution rate of HAP and a decrease in that of β-TCP.

Phase transition of Mg3(PO4)2 polymorphs at high-temperature: In-situ synchrotron X-ray diffraction and Raman spectroscopic study

In-situ synchrotron X-ray diffraction and Raman spectroscopy were used to study the stabilities, thermal expansion and vibrational modes of synthetic Mg₃(PO₄)₂. The polymorphs (Mg₃(PO₄)₂-I, II, III) were investigated in the temperature range of 299 ∼ 1173 K at ambient pressure. An irreversible phase transition was observed for both Mg₃(PO₄)₂-II and Mg₃(PO₄)₂-III, whereas Mg₃(PO₄)₂-I is stable in the present study. Based on the in-situ synchrotron X-ray diffraction and Raman spectroscopic measurements, Mg₃(PO₄)₂-II and Mg₃(PO₄)₂-III transform to Mg₃(PO₄)₂-I at 1073 K and 1023 K, respectively. The volumetric thermal expansion coefficients of Mg₃(PO₄)₂-I, II and III were determined as 3.31(4) × 10^-5 K^-1, 3.91(4) × 10^-5 K^-1, and 3.25(5) × 10^-5 K^-1, respectively. All three Mg₃(PO₄)₂ polymorphs show axial thermal expansive anisotropy since the thermal expansion coefficients along different axes are inconsistent. The effect of temperature on the Raman vibrations of the three Mg₃(PO₄)₂ polymorphs was quantitatively analyzed. And the isobaric mode Grüneisen parameters of three Mg₃(PO₄)₂ polymorphs are calculated, which are in the range of 0.07 ∼ 3.54.

Sustainable phosphorus management in soil using bone apatite

Soil fertility and phosphorus management by bone apatite amendment are receiving increasing attention, yet further research is needed to integrate the physicochemical and mineralogical transformation of bone apatite and their impact on the supply and storage of phosphorus in soil. This study has examined bone transformation in the field over a span of 10-years using a set of synchrotron-based microscopic and spectroscopic techniques. Transmission X-ray microscopy (TXM) observations reveal the in-situ deterioration of bone osteocyte-canaliculi system and sub-micron microbial tunneling within a year. Extensive organic decomposition, secondary mineral formation and re-mineralization of apatite are evident from the 3rd year. The relative ratio of (v₁ + v₃) PO₄^3- to v₃ CO₃^2- and to amide I increase, and the v_3c PO₄^3- peak exhibits a blue-shift in less than 3 years. The carbonate substitution of bone hydroxyapatite (HAp) to AB-type CHAp, and phosphate crystallographic rearrangement become apparent after 10 years' aging. The overall CO₃^2- peak absorbance increases over time, contributing to a higher acid susceptibility in the aged bone. The X-ray Photoelectron Spectroscopy (XPS) binding energies for Ca (2p), P (2p) and O (1s) exhibit a red-shift after 1 year because of organo-mineral interplay and a blue-shift starting from the 3rd year as a result of the de-coupling of mineral and organic components. Nutrient supply to soil occurs within months via organo-mineral decoupling and demineralization. More phosphorus has been released from the bones and enriched in the associated and adjacent soils over time. Lab incubation studies reveal prominent secondary mineral formation via re-precipitation at a pH similar to that in soil, which are highly amorphous and carbonate substituted and prone to further dissolution in an acidic environment. Our high-resolution observations reveal a stage-dependent microbial decomposition, phosphorus dissolution and immobilization via secondary mineral formation over time. The active cycling of phosphorus within the bone and its interplay with adjacent soil account for a sustainable supply and storage of phosphorus nutrients.

Synthesis and Characterization of Calcium Phosphate Materials Derived from Eggshells from Different Poultry with and without the Eggshell Membrane

Calcium phosphate materials such as hydroxyapatite (HA) or tricalcium phosphate (β-TCP) are highly attractive due to their multitude of applications in bone replacement as well as their environmental and ecological credentials. In this research, quail, hen, duck, and pigeon eggshells were used as a calcium source to obtain calcium phosphate materials via the environmentally friendly wet synthesis. Using the eggshells with the organic membrane, the biphasic calcium phosphate materials composed mainly of HA were obtained. The second mineral phase was β-TCP in the case of using quail, hen, and pigeon eggshells and octacalcium phosphate (OCP) in the case of duck eggshells. The HA content in the obtained materials depended on the amount of membrane in the eggshells and decreased in the order of pigeon, duck, hen, and quail eggshells. The eggshell membrane removal from the eggshells caused the reduced content of HA and the presence of the more soluble β-TCP or OCP phase in the obtained materials. The calcium ions release profile in the PBS buffer indicates the potential biomedical application of these materials.

Nanosized calcium deficient hydroxyapatites for tooth enamel protection

Calcium phosphates (CaP) are extensively studied as additives to dental care products for tooth enamel protection against caries. However, it is not clear yet whether substituted CaP could provide better enamel protection. In this study we produced, characterized and tested in vitro substituted and co‐substituted calcium deficient hydroxyapatite (CDHAp) with Sr²⁺ and F⁻ ions. X‐ray powder diffractometry, Fourier transformation infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray analysis, Brunauer–Emmett–Teller were used to characterize synthesized powders and also cytotoxicity was evaluated. pH = f(t) test was performed to estimate, weather synthesized CDHAp suspensions are able to increase pH of experimental media after acid addition. Synthesis products were incorporated into paste to perform in vitro remineralization on the bovine enamel. In addition to mentioned instrumental methods, profilometry was used for evaluation of remineralised enamel samples. The obtained results confirmed formation of CDHAp substituted with 1.5–1.6 wt% of fluoride and 7.4–7.8 wt% of strontium. pH = f(t) experiment pointed out that pH increased by approximately 0.3 within 10 min after acid addition for all CDHAp suspensions. A new layer of the corresponding CDHAp was formed on the enamel. Its thickness increased by 0.8 ± 0.1 μm per day and reached up to 5.8 μm after 7 days. Additionally, octa calcium phosphates were detected on the surface of control samples. In conclusion, we can assume that CDHAp substituted with Sr²⁺ and/or F⁻ could be used as an effective additive to dental care products promoting formation of protecting layer on the enamel, but there was no significant difference among sample groups.

Conjunction of gallium doping and calcium silicate mediates osteoblastic and osteoclastic performances of tricalcium phosphate bioceramics

Gallium-containing biomaterials are considered promising for reconstructing osteoporotic bone defects, owing to the potent effect of gallium on restraining osteoclast activities. Nevertheless, the gallium-containing biomaterials were demonstrated to disturb the osteoblast activities. In this study, tricalcium phosphate (TCP) bioceramics were modified by gallium doping in conjunction with incorporation of calcium silicate (CS). The results indicated that the incorporation of CS promoted transition ofβ-TCP toα-TCP, and accelerated densification process, but did not improve the mechanical strength of bioceramics. The silicon released from the composite bioceramics diminished the inhibition effect of released gallium on osteoblast activities, and maintained its effect on restraining osteoclast activities. The TCP-based bioceramics doped with 2.5 mol% gallium and incorporated with 10 mol% CS are considered suitable for treating the bone defects in the osteoporotic environment.

Biphasic calcium phosphate microspheres in biomedical applications

Biphasic calcium phosphate (BCP) microspheres benefit from, on the one hand, a desired shape offering improved flowability and injectability to fill complex-shaped bone defects and on the other hand, a promising combination of bioresorbability, bioactivity, biocompatibility, osteogenesis and angiogenesis. The biofunctional characteristics of BCP microspheres are mainly controlled by varying the constitute phase ratio, porosity and surface roughness, which are all determined by the used production route and its parameters. In this paper, the manufacturing methods, properties and applications of BCP microspheres are reviewed and concluded in terms of future work directions to develop their uses in biomedicine, particularly in bone tissue regenerative and delivery applications.

Biocompatible magnesium-doped biphasic calcium phosphate for bone regeneration

Autologous bone grafting remains the gold standard for almost all bone void-filling orthopedic surgery. However, autologous bone grafting has several limitations, thus scientists are trying to identify an ideal synthetic material as an alternative bone graft substitute. Magnesium-doped biphasic calcium phosphate (Mg-BCP) has recently been in the spotlight and is considered to be a potential bone substitute. The Mg-BCP is a mixture of two bioceramics, that is, hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), doped with Mg2+ , and can be synthesized through chemical wet-precipitation, sol-gel, single diffusion gel, and solid state reactions. Regardless of the synthesis routes, it is found that the Mg2+ preferentially accommodates in β-TCP lattice instead of the HA lattice. The addition of Mg2+ to BCP leads to desirable physicochemical properties and is found to enhance the apatite-forming ability as compared to pristine BCP. In vitro results suggest that the Mg-BCP is bioactive and not toxic to cells. Implantation of Mg-BCP in in vivo models further affirmed its biocompatibility and efficacy as a bone substitute. However, like the other bioceramics, the optimum physicochemical properties of the Mg-BCP scaffold have yet to be determined. Further investigations are required regarding Mg-BCP applications in bone tissue engineering.

Direct 3D Printing of Seashell Precursor toward Engineering a Multiphasic Calcium Phosphate Bone Graft

Multiphasic calcium phosphate (Ca-P) has widely been explored for bone graft replacement. This study represents a simple method of developing osteoinductive scaffolds by direct printing of seashell resources. The process demonstrates a coagulation-assisted extrusion-based three-dimensional (3D) printing process for rapid fabrication of multiphasic calcium phosphate-incorporated 3D scaffolds. These scaffolds demonstrated an interconnected open porous architecture with improved compressive strength and higher surface area. Multiphasic calcium phosphate (Ca-P) and hydroxyapatite present in the multi-scalar naturally resourced scaffold displayed differential protein adsorption, thus facilitating cell adhesion, migration, and differentiation, resulting in enhanced deposition of the extracellular matrix. The microstructural and physicochemical attributes of the scaffolds also lead to enhanced stem cell differentiation as witnessed from gene and protein expression analysis. Furthermore, the histological study of subcutaneous implantation evidently portrays promising biocompatibility without foreign body reaction. Neo-tissue in-growth was manifested with abundant blood vessels, thus indicative of excellent vascularization. Notably, cartilaginous and proteoglycan-rich tissue deposition indicated ectopic bone formation via an endochondral ossification pathway. The hierarchical interconnected porous architectural tribology accompanied with multiphasic calcium phosphate composition manifests its successful implication in enhancing stem cell differentiation and promoting excellent tissue in-growth, thus making it a plausible alternative in bone tissue engineering applications.

Monetite, an important calcium phosphate compound-Its synthesis, properties and applications in orthopedics

This review recognizes a unique calcium phosphate (CaP) phase known as monetite or dicalcium phosphate anhydrous (DCPA, CaHPO₄), and presents an overview of its properties, processing, and applications in orthopedics. The motivation for the present effort is to highlight the state-of-the-art research and development of monetite and propel the research community to explore more of its potentials in orthopedics. After a brief introduction of monetite, we provide a summary of its various synthesis routes like dehydration, solvent-based, energy-assisted processes and also discuss the formation of different crystal structures with respect to the synthesis conditions. Subsequently, we discuss the material's noteworthy physico-chemical properties including the crystal structure, vibrational spectra, solubility, thermal decomposition, and conversion to other phases. Of note, we focus on the biological (in vitro and in vivo) properties of monetite, given its ever-increasing popularity as a biomaterial for medical implants. Appropriately, we discuss various orthopedic applications of monetite as bone cement, implant coatings, granules for defect fillers, and scaffolds. Many in vitro and in vivo studies confirmed the favorable osteointegration and osteoconduction properties of monetite products, along with a better balance between implant resorption and new bone formation as compared to other CaP phases. The review ends with translational aspects of monetite and presents thoughts about its possible future research directions. Further research may explore but not limited to improvements in mechanical strength of monetite-based scaffolds, using monetite particles as a therapeutic agent delivery, and tissue engineering strategies where monetite serves as the biomaterial. STATEMENT OF SIGNIFICANCE: This is the first review that focusses on the favorable potential of monetite for hard tissue repair and regeneration. The article accurately covers the "Synthesis-Structure-Property-Applications" correlations elaborating on monetite's diverse material properties. Special focus is put on the in vitro and in vivo properties of the material highlighting monetite as an orthopedic material-of-choice. The synthesis techniques are discussed which provide important information about the different fabrication routes for monetite. Most importantly, the review provides comprehensive knowledge about the diverse biomedical applications of monetite as granules, defect--specific scaffolds, bone cements and implant coatings. This review will help to highlight monetite's potential as an effective regenerative medicine and catalyze the continuing translation of this bioceramic from the laboratory to clinics.

Materials and Manufacturing Techniques for Polymeric and Ceramic Scaffolds Used in Implant Dentistry

Preventive and regenerative techniques have been suggested to minimize the aesthetic and functional effects caused by intraoral bone defects, enabling the installation of dental implants. Among them, porous three-dimensional structures (scaffolds) composed mainly of bioabsorbable ceramics, such as hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) stand out for reducing the use of autogenous, homogeneous, and xenogenous bone grafts and their unwanted effects. In order to stimulate bone formation, biodegradable polymers such as cellulose, collagen, glycosaminoglycans, polylactic acid (PLA), polyvinyl alcohol (PVA), poly-ε-caprolactone (PCL), polyglycolic acid (PGA), polyhydroxylbutyrate (PHB), polypropylenofumarate (PPF), polylactic-co-glycolic acid (PLGA), and poly L-co-D, L lactic acid (PLDLA) have also been studied. More recently, hybrid scaffolds can combine the tunable macro/microporosity and osteoinductive properties of ceramic materials with the chemical/physical properties of biodegradable polymers. Various methods are suggested for the manufacture of scaffolds with adequate porosity, such as conventional and additive manufacturing techniques and, more recently, 3D and 4D printing. The purpose of this manuscript is to review features concerning biomaterials, scaffolds macro and microstructure, fabrication techniques, as well as the potential interaction of the scaffolds with the human body.

Atomic Layer Deposition of Bioactive TiO2 Thin Films on Polyetheretherketone for Orthopedic Implants

TiO₂ thin films were deposited on the orthopedic implant material polyetheretherketone (PEEK) by plasma enhanced atomic layer deposition (PEALD) and characterized for their ability to enhance the osseointegrative properties. PEALD was chosen for film deposition to circumvent drawbacks present in line-of-sight deposition techniques, which require technically complex setups for a homogeneous coating thickness. Film conformality was analyzed on silicon 3D test structures and PEEK with micron-scale surface roughness. Wettability and surface energy were determined through contact angle measurements; film roughness and crystallinity were determined by atomic force microscopy and X-ray diffraction, respectively. Adhesion properties of TiO₂ on PEEK were determined with tensile strength tests. Cell tests were performed with the mouse mesenchymal tumor stem cell line ST-2. TiO₂-coated PEEK disks were used as substrates for cell proliferation tests and long-term differentiation tests. After 28 days of cultivation, a mineralized bone matrix was observed. Furthermore, the collagen I and osteocalcin content were determined. The results reveal that the osteogenic properties of the TiO₂ thin film are comparable to those of hydroxyapatite, and thus bioactive properties of PEEK implants are improved by TiO₂ thin films deposited with PEALD.

Stem Cell-Friendly Scaffold Biomaterials: Applications for Bone Tissue Engineering and Regenerative Medicine

Bone is a dynamic organ with high regenerative potential and provides essential biological functions in the body, such as providing body mobility and protection of internal organs, regulating hematopoietic cell homeostasis, and serving as important mineral reservoir. Bone defects, which can be caused by trauma, cancer and bone disorders, pose formidable public health burdens. Even though autologous bone grafts, allografts, or xenografts have been used clinically, repairing large bone defects remains as a significant clinical challenge. Bone tissue engineering (BTE) emerged as a promising solution to overcome the limitations of autografts and allografts. Ideal bone tissue engineering is to induce bone regeneration through the synergistic integration of biomaterial scaffolds, bone progenitor cells, and bone-forming factors. Successful stem cell-based BTE requires a combination of abundant mesenchymal progenitors with osteogenic potential, suitable biofactors to drive osteogenic differentiation, and cell-friendly scaffold biomaterials. Thus, the crux of BTE lies within the use of cell-friendly biomaterials as scaffolds to overcome extensive bone defects. In this review, we focus on the biocompatibility and cell-friendly features of commonly used scaffold materials, including inorganic compound-based ceramics, natural polymers, synthetic polymers, decellularized extracellular matrix, and in many cases, composite scaffolds using the above existing biomaterials. It is conceivable that combinations of bioactive materials, progenitor cells, growth factors, functionalization techniques, and biomimetic scaffold designs, along with 3D bioprinting technology, will unleash a new era of complex BTE scaffolds tailored to patient-specific applications.

Improved in vitro bioavailability of a newly developed functionalized calcium carbonate salt as a food ingredient and its comparison with available commercial calcium salts

The bioaccessibility and bioavailability of a functionalized Calcium (Ca) salt as food ingredient, based on modified Ca carbonate and hydroxyapatite (FCC), was determined and compared with frequently used Ca sources (Ca citrate tetrahydrate (CCT), tri-Ca phosphate (triCP) and Ca carbonate (CC). Results showed a similar Ca bioaccessibility for CCT (76.44 ± 9.73%), CC (73.7 ± 8.18%) and FCC (74.4 ± 1.87%) and a lower value for tri-CP (46.07 ± 8.68%). FCC showed the highest bioavailability, 5.68 ± 0.26%, compared to CC, CCT and tri-CP (3.93 ± 0.99%, 3.41 ± 0.33%, 1.85 ± 0.34%, respectively). The innovative chemical composition and structure of FCC based on amorphous hydroxyapatite combined with Ca carbonate, a greater porosity, lower agglomerates and particle size, improve the Ca solubility in the intestinal media, explaining the similar bioaccessibility but higher bioavailability of FCC compared to CCT, tri-CP and CC.

"Hard" ceramics for "Soft" tissue engineering: Paradox or opportunity?

Tissue engineering provides great possibilities to manage tissue damages and injuries in modern medicine. The involvement of hard biocompatible materials in tissue engineering-based therapies for the healing of soft tissue defects has impressively increased over the last few years: in this regard, different types of bioceramics were developed, examined and applied either alone or in combination with polymers to produce composites. Bioactive glasses, carbon nanostructures, and hydroxyapatite nanoparticles are among the most widely-proposed hard materials for treating a broad range of soft tissue damages, from acute and chronic skin wounds to complex injuries of nervous and cardiopulmonary systems. Although being originally developed for use in contact with bone, these substances were also shown to offer excellent key features for repair and regeneration of wounds and "delicate" structures of the body, including improved cell proliferation and differentiation, enhanced angiogenesis, and antibacterial/anti-inflammatory activities. Furthermore, when embedded in a soft matrix, these hard materials can improve the mechanical properties of the implant. They could be applied in various forms and formulations such as fine powders, granules, and micro- or nanofibers. There are some pre-clinical trials in which bioceramics are being utilized for skin wounds; however, some crucial questions should still be addressed before the extensive and safe use of bioceramics in soft tissue healing. For example, defining optimal formulations, dosages, and administration routes remain to be fixed and summarized as standard guidelines in the clinic. This review paper aims at providing a comprehensive picture of the use and potential of bioceramics in treatment, reconstruction, and preservation of soft tissues (skin, cardiovascular and pulmonary systems, peripheral nervous system, gastrointestinal tract, skeletal muscles, and ophthalmic tissues) and critically discusses their pros and cons (e.g., the risk of calcification and ectopic bone formation as well as the local and systemic toxicity) in this regard. STATEMENT OF SIGNIFICANCE: Soft tissues form a big part of the human body and play vital roles in maintaining both structure and function of various organs; however, optimal repair and regeneration of injured soft tissues (e.g., skin, peripheral nerve) still remain a grand challenge in biomedicine. Although polymers were extensively applied to restore the lost or injured soft tissues, the use of bioceramics has the potential to provides new opportunities which are still partially unexplored or at the very beginning. This reviews summarizes the state of the art of bioceramics in this field, highlighting the latest evolutions and the new horizons that can be opened by their use in the context of soft tissue engineering. Existing results and future challenges are discussed in order to provide an up-to-date contribution that is useful to both experienced scientists and early-stage researchers of the biomaterials community.

Development of injectable chitosan/biphasic calcium phosphate bone cement and in vitro and in vivo evaluation

Injectable biphasic calcium phosphate bone cements (BCPCs) composed of β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) have been intensively investigated because of their high rate of biodegradation, bioactivity and osteoconductivity, which can be adjusted by changing the ratio between β-TCP and HA phases after setting. The aim of this study was to evaluate the performance of 1 wt% chitosan fiber additive with biphasic calcium phosphate as an injectable bone cement both in vitro and in vivo. In vitro evaluation of compressive strength, degradation rate, morphology, and cell and alkaline phosphatase activities was done by comparison with bone cement without β-TCP. The in vivo results for micro-CT scanning and histological examinations for three groups (control, BCPC and commercial biphasic calcium phosphate granules) were characterized and compared. After the addition of 20 wt% β-TCP to calcium phosphate cement, the initial and final setting times of the sample were 3.92 min and 11.46 min, respectively, which were not significantly different from cement without β-TCP. The degradation time of the BCPC material was longer than that of calcium phosphate cement alone. The healing process was significantly faster for BCPC than for the control and commercial product groups. Therefore, this is the first evidence that BCPC is an attractive option for bone surgery due to its faster stimulation of healing and faster degradation rate.

In vitro and in vivo study on the osseointegration of BCP-coated versus uncoated nondegradable thermoplastic polyurethane focal knee resurfacing implants

Focal knee resurfacing implants (FKRIs) are intended to treat cartilage defects in middle-aged patients. Most FKRIs are metal-based, which hampers follow-up of the joint using magnetic resonance imaging and potentially leads to damage of the opposing cartilage. The purpose of this study was to develop a nondegradable thermoplastic polyurethane (TPU) FKRI and investigate its osseointegration. Different surface roughness modifications and biphasic calcium phosphate (BCP) coating densities were first tested in vitro on TPU discs. The in vivo osseointegration of BCP-coated TPU implants was subsequently compared to uncoated TPU implants and the titanium bottom layer of metal control implants in a caprine model. Implants were implanted bilaterally in stifle joints and animals were followed for 12 weeks, after which the bone-to-implant contact area (BIC) was assessed. Additionally, 18F-sodium-fluoride (18F-NaF) positron emission tomography PET/CT-scans were obtained at 3 and 12 weeks to visualize the bone metabolism over time. The BIC was significantly higher for the BCP-coated TPU implants compared to the uncoated TPU implants (p = .03), and did not significantly differ from titanium (p = .68). Similar 18F-NaF tracer uptake patterns were observed between 3 and 12 weeks for the BCP-coated TPU and titanium implants, but not for the uncoated implants. TPU FKRIs with surface modifications could provide the answer to the drawbacks of metal FKRIs.

A review of calcium phosphate cements and acrylic bone cements as injectable materials for bone repair and implant fixation

Treatment of bone defects caused by trauma or disease is a major burden on human healthcare systems. Although autologous bone grafts are considered as the gold standard, they are limited in availability and are associated with post-operative complications. Minimally invasive alternatives using injectable bone cements are currently used in certain clinical procedures, such as vertebroplasty and balloon kyphoplasty. Nevertheless, given the high incidence of fractures and pathologies that result in bone voids, there is an unmet need for injectable materials with desired properties for minimally invasive procedures. This paper provides an overview of the most common injectable bone cement materials for clinical use. The emphasis has been placed on calcium phosphate cements and acrylic bone cements, while enabling the readers to compare the opportunities and challenges for these two classes of bone cements. This paper also briefly reviews antibiotic-loaded bone cements used in bone repair and implant fixation, including their efficacy and cost for healthcare systems. A summary of the current challenges and recommendations for future directions has been brought in the concluding section of this paper.

Phosphate functionalization and enzymatic calcium mineralization synergistically enhance oligo[poly(ethylene glycol) fumarate] hydrogel osteoconductivity for bone tissue engineering

A current approach in bone tissue engineering is the implantation of polymeric scaffolds that promote osteoblast attachment and growth as well as biomineralization. One promising polymer is oligo[poly(ethylene glycol) fumarate] (OPF), a polyethylene glycol-based material that is biocompatible, injectable, and biodegradable, but in its native form does not support robust bone cell attachment or growth. To address this issue, this study evaluated the osteoconductivity of bis[02-(methacryloyloxy)ethyl] phosphate (BP) functionalized OPF hydrogels (OPF-BP) using MC3T3-E1 pre-osteoblast cells, both before and after enzymatic mineralization with a calcium solution. The inclusion of negatively charged functional groups allowed for the tailored uptake and release of calcium, while also altering the mechanical properties and surface topography of the hydrogel surface. In cell culture, OPF-BP hydrogels with 20 and 30% (w/w) BP optimized osteoblast attachment, proliferation, and differentiation after a 21-day in vitro period. In addition, the OPF-BP30 treatment, when mineralized with calcium, exhibited a 128% increase in osteocalcin expression when compared with the non-mineralized treatment. These findings suggest that phosphate functionalization and enzymatic calcium mineralization can act synergistically to enhance the osteoconductivity of OPF hydrogels, making this processed material an attractive candidate for bone tissue engineering applications.