Formation Of Apatite Crystals Research Articles

Mechanical and biological properties of Ti–15%Mo-Cenosphere porous composite sintered by SPS

Decreasing the sheath stresses and facilitating osteogenesis are of great interest in the preparation of orthopedic implants. For this reason, the fabrication of porous composite samples based on Ti alloys is of great importance in the medical industry. This research is dedicated to investigating the mechanical and biological properties of porous composite samples prepared by powder metallurgy, space holder technique, and sintering using Spark Plasma Sintering (SPS). According to the results obtained, it was found that owing to an increase in the volume percentage of the space holder, the density of the samples decreased while the true porosity percentage of the samples increased. The morphology of the pores formed in the structure was spherical with a uniform distribution. In addition, it was found that the elastic modulus of the sample decreased significantly so that the samples containing >30 vol% cenosphere space holder exhibited properties similar to those of bones. Also, according to the results of the MTT, SBF immersion, and cell adhesion tests, it was concluded that the samples were of high cell viability. Moreover, the growth and proliferation of bone cells and the formation of apatite crystals using these composites were confirmed.

Investigation on the Microstructural Diversity of a Three-Dimensional Porous Hydroxyapatite/Wollastonite Skeleton via Biomineralization in Simulated Body Fluids

The occurrence of fractures has emerged as one of the most prevalent injuries in the human body. In bone reconstruction surgery, after the implantation of porous hydroxyapatite materials, there is an initial infiltration of body fluids into the porous implant, followed by biomineralization-mediated apatite crystal formation and the subsequent ingrowth of bone cells. Despite extensive research efforts in this field, previous investigations have primarily focused on the formation of apatite crystals on exposed surfaces, with limited literature available regarding the formation of apatite crystals within the internal microstructures of bone implants. Herein, we demonstrate the occurrence of dynamic biomineralization within a three-dimensional porous hydroxyapatite/wollastonite (HA/WS) skeleton, leading to the abundant formation of nano-sized apatite crystals across diverse internal environments. Our findings reveal that these apatite nanocrystals demonstrate distinct rates of nucleation, packing densities, and crystal forms in comparison to those formed on the surface. Therefore, the objective of this study was to elucidate the temporal evolution of biomineralization processes by investigating the microstructures of nanocrystals on the internal surfaces of HA/WS three-dimensional porous materials at distinct stages of biomineralization and subsequently explore the biological activity exhibited by HA/WS when combined with cell investigation into apatite crystal biomineralization mechanisms at the nanoscale, aiming to comprehend natural bone formation processes and develop efficacious biomimetic implants for tissue engineering applications. The simultaneous examination of bone cell attachment and its interaction with ongoing internal nanocrystal formation will provide valuable insights for designing optimal scaffolds conducive to bone cell growth, which is imperative in tissue engineering endeavors.

Cementum is key to periodontal tissue regeneration: A review on apatite microstructures for creation of novel cementum-based dental implants.

The cementum is the outermost layer of hard tissue covering the dentin within the root portion of the teeth. It is the only hard tissue with a specialized structure and function that forms a part of both the teeth and periodontal tissue. As such, cementum is believed to be critical for periodontal tissue regeneration. In this review, we discuss the function and histological structure of the cementum to promote crystal engineering with a biochemical approach in cementum regenerative medicine. We review the microstructure of enamel and bone while discussing the mechanism underlying apatite crystal formation to infer the morphology of cementum apatite crystals and their complex structure with collagen fibers. Finally, the limitations of the current dental implant treatments in clinical practice are explored from the perspective of periodontal tissue regeneration. We anticipate the possibility of advancing periodontal tissue regenerative medicine via cementum regeneration using a combination of material science and biochemical methods.

Bioactive Carbonate Apatite Cement with Enhanced Compressive Strength via Incorporation of Silica Calcium Phosphate Composites and Calcium Hydroxide.

Carbonate apatite (CO3Ap) is a bioceramic material with excellent properties for bone and dentin regeneration. To enhance its mechanical strength and bioactivity, silica calcium phosphate composites (Si-CaP) and calcium hydroxide (Ca(OH)2) were added to CO3Ap cement. The aim of this study was to investigate the effect of Si-CaP and Ca(OH)2 on the mechanical properties in terms of the compressive strength and biological characteristics of CO3Ap cement, specifically the formation of an apatite layer and the exchange of Ca, P, and Si elements. Five groups were prepared by mixing CO3Ap powder consisting of dicalcium phosphate anhydrous and vaterite powder added by varying ratios of Si-CaP and Ca(OH)2 and 0.2 mol/L Na2HPO4 as a liquid. All groups underwent compressive strength testing, and the group with the highest strength was evaluated for bioactivity by soaking it in simulated body fluid (SBF) for one, seven, 14, and 21 days. The group that added 3% Si-CaP and 7% Ca(OH)2 had the highest compressive strength among the groups. SEM analysis revealed the formation of needle-like apatite crystals from the first day of SBF soaking, and EDS analysis indicated an increase in Ca, P, and Si elements. XRD and FTIR analyses confirmed the presence of apatite. This combination of additives improved the compressive strength and showed the good bioactivity performance of CO3Ap cement, making it a potential biomaterial for bone and dental engineering applications.

Effect of air-abrasion pretreatment with three bioactive materials on enamel susceptibility to erosion by artificial gastric juice

ObjectiveThe purpose of the study was to investigate the protective effect of three in-office preventive treatments with bioactive materials against enamel erosion induced by artificial gastric juice similar to that found in gastroesophageal reflux disease (GERD) patients. The treatments included air-abrasion of enamel with a fluoride-containing bioactive glass (BioMinF®), Bioglass 45S5 (ProSylc) and nano-hydroxyapatite (MI Pearls) to test enamel susceptibility following an erosive challenge. MethodsEnamel surface loss was evaluated using confocal microscopy, while changes in enamel surface roughness and morphology were also investigated after the treatments. SEM and EDS were used to observe formation of apatite crystals on enamel and to detect alterations in mineral composition. In Group 1 (negative control) the specimens did not receive any treatment; Group 2 specimens (positive control) treated with 0.4 % SnF2, while in Groups 3–5 enamel was air-abraded with BioMinF®, ProSylc and MI Pearls, respectively. ResultsAll the experimental groups reduced significantly enamel surface loss compared to the negative control group (p < 0.05), except for the MI Pearls treatment (p > 0.05). The most protective behavior against erosion presented the treatment with SnF2. BioMinF induced the larger amount of apatite crystals on the enamel surface, followed by ProSylc. SignificanceBioMinF and ProSylc treatments may be beneficial against dental erosion induced by gastric juice in GERD patients, while MI Pearls treatment may not suitable for this indication. Both materials promote formation of apatite crystals on enamel in acidic conditions protecting the surface from the erosion. The tested treatments may be useful in GERD patients who cannot comply with at-home therapies with SnF2.

Preparation of antimicrobial calcium phosphate/protamine composite powders with fluoride ions using octacalcium phosphate

Calcium phosphates are key biomaterials in dental treatment and bone regeneration. Biomaterials must exhibit antibacterial properties to prevent microbial infection in implantation frameworks. Previously, we developed various types of calcium phosphate powders (amorphous calcium phosphate, octacalcium phosphate (OCP), dicalcium phosphate anhydrate, and hydroxyapatite) with adsorbed protamine (which is a protein with antibacterial property) and confirmed their antibacterial property. In this study, as foundational research for the development of novel oral care materials, we synthesized calcium phosphate composite powders from three starting materials: i) OCP, which intercalates organic compounds, ii) protamine, which has antibacterial properties, and iii) F– ion, which promotes the formation of apatite crystals. Through investigating the preparation concentration of the F– ions and their loading into OCP, it was found that more F– ion could be loaded at higher concentrations regardless of the loading method. It was also observed that the higher the preparation concentration, the more the OCP converted to fluorapatite. The synthesized calcium phosphate composite powders were evaluated for biocompatibility through proliferation of MG-63 cells, with none of the powders exhibiting any growth inhibition. Antimicrobial tests showed that the calcium phosphate composite powders synthesized with protamine and F– ion by precipitation had enhanced antimicrobial properties than those synthesized by protamine adsorption. Thus, the calcium phosphate composite powder prepared from OCP, protamine, and F– ion forms the basis for promising antimicrobial biomaterials.Graphical abstract

Comparative evaluation of bioactivity, fluoride release, shear bond strength, and compressive strength of conventional glass ionomer cement incorporated with three inorganic bioactive nanoparticles: An experimental analysis.

Over the course of four decades, the bioactive materials have changed. They have become more specialized, more manageable, possessing superior qualities. Thus, it should be encouraged to conduct ongoing research to improve these materials even further in order to meet the growing clinical and restorative needs. To evaluate and compare bioactivity, fluoride release, shear bond strength and compressive strength of conventional GIC incorporated with three inorganic bioactive nanoparticles. For the study, total of 160 samples were included. The samples were divided in four groups (40 samples per group) i.e. 3 wt% of forsterite (Mg2SiO4) (Group 2), wollastonite (CaSiO3) (Group 3) and niobium pentoxide (Nb2O5) (Group 4) nanoparticles incorporated into GIC (Group 1). The bioactivity (FEG-SEM and EDX analysis), fluoride release (ion-selective electrode), shear bond strength testing (UTM followed by evaluation under stereomicroscope) and the compressive strength (UTM) was checked for each group. Wollastonite nanoparticles (3wt %) incorporated to GIC showed maximum increase in the apatite crystal formation,Ca and P content and highest fluoride release. Mean shear bond strength was highest in niobium pentoxide nanoparticles (3wt %) incorporated to GIC while mean compressive strength was highest in forsterite nanoparticles (3wt %) added to GIC. Positive results were observed which showed increase in the bioactivity alongwith enhancement of the fluoride release, shear bond strength and compressive strength but further research on these materials is warranted before its use in clinical practice.

A time-course Raman spectroscopic analysis of spontaneous in vitro microcalcifications in a breast cancer cell line

Microcalcifications are early markers of breast cancer and can provide valuable prognostic information to support clinical decision-making. Current detection of calcifications in breast tissue is based on X-ray mammography, which involves the use of ionizing radiation with potentially detrimental effects, or MRI scans, which have limited spatial resolution. Additionally, these techniques are not capable of discriminating between microcalcifications from benign and malignant lesions. Several studies show that vibrational spectroscopic techniques are capable of discriminating and classifying breast lesions, with a pathology grade based on the chemical composition of the microcalcifications. However, the occurrence of microcalcifications in the breast and the underlying mineralization process are still not fully understood. Using a previously established model of in vitro mineralization, the MDA-MB-231 human breast cancer cell line was induced using two osteogenic agents, inorganic phosphate (Pi) and β-glycerophosphate (βG), and direct monitoring of the mineralization process was conducted using Raman micro-spectroscopy. MDA-MB-231 cells cultured in a medium supplemented with Pi presented more rapid mineralization (by day 3) than cells exposed to βG (by day 11). A redshift of the phosphate stretching peak for cells supplemented with βG revealed the presence of different precursor phases (octacalcium phosphate) during apatite crystal formation. These results demonstrate that Raman micro-spectroscopy is a powerful tool for nondestructive analysis of mineral species and can provide valuable information for evaluating mineralization dynamics and any associated breast cancer progression, if utilized in pathological samples.The mineralization of MDA-MB-231 breast cells was investigated using Raman micro-spectroscopy. Mineralization was induced by two osteogenic agents: inorganic phosphate (Pi) and β-Glycerophosphate (βG). The results show that the uptake of Pi allows a faster mineralization and the uptake of βG indicated the presence of a precursor phase during the hydroxyapatite crystal formation.

Review Article Recent Advances in Preventing Dental Erosion

Dental erosion is defined as an irreversible loss of dental hard tissue due to exposure to chelating agents or non-bacterial acids. The occurrence of this condition was noted and the incidence and prevalence of dental erosion has been increasingly documented.The Ant erosive agents such as Anacardic acid in which the key component is the cashewnut shell liquid is phenolic lipids. It is a mixture of molecules which are saturated and unsaturated. It is also considered to have an anti-microbial effect and has been studied for the treatment of cancer, oxidative damage, inflammation and obesity disorders. Other anti-erosive agent like Fluoride helps in tooth remineralization. Fluorapatite, rather than hydroxyapatite, forms during the process of remineralization when fluoride is found in oral fluids. In apatite crystal lattice formation, fluoride ions replace hydroxy ions. Fluorapatite, even under acidic conditions, is less soluble than hydroxyapatite, which helps to regenerate tooth enamel. Fluoride is therefore a stronger anti-erosive agent. Various Recent advances in anti-erosive agents are Calcium and phosphate, Casein phosphopeptide amorphous calcium phosphate (CPP-ACP), Protease inhibitors, Oils, Chitosan chitosan and Multivalent metal ions Various techniques to evaluate dental erosion are in vitro techniques and in vivo techniques. In vitro techniques are Scanning electron microscope, Surface Profilometry, Polarized Light Microscopyand Non-Contact Confocal Laser Scanning Microscopy (CLSM). And iv vivo techniques are Photographs Clinical review and indices. The most important point of treatment is identifying and removing the erosion factor, above all current materials and methods. Therefore, early identification of the lesions, evaluation and removal of the etiological variables are relevant topics.

Functional modification of silicone rubber through nano‐hydroxylapatite embedding

AbstractSilicone rubber (SR) has extensively been used for different industrial and biomedical applications, in view of its good elasticity, chemical inertness, and biocompatibility. However, cure inhibition features, poor mechanical properties, and hydrophobicity, often, limit the possible expansion of its spectrum of applications. The present work has been designed to address these issues by embedding a potential biocompatible filler, nano‐hydroxylapatite (n‐HA), within the SR matrix, through compression molding. The n‐HA particles were initially synthesized by a wet chemical method, and were subsequently introduced into SR quantitatively. The rheological features, compressive properties, simulated body fluid (SBF) uptake, bovine serum albumin (BSA) adsorption, blood compatibility, and cytocompatibility of n‐HA modified SR systems have been investigated. The change in rheological characteristics after n‐HA embedding within SR clearly indicated the favorable interactions between them, and a compatible functional existence under external stresses. The compressive strength, which is critical for the different applications of SR, has been found to be increased with an increase in n‐HA loading. In‐vitro mineralization studies using SBF showed the formation of apatite crystals on the surface of SR/n‐HA system indicating its biocompatibility. This has been confirmed by SEM and FTIR examinations. It has further been observed that the addition of n‐HA particles into SR matrix enhances the protein adsorption characteristics. The n‐HA embedded system exhibited excellent blood compatibility, which has been complemented through hemolysis (%) studies and thrombogenicity assay. The results indicate that the strategy of n‐HA embedding would do significant value addition to SR, and widen its scope in the industrial and biomedical sectors.

The effect of Allium cepa extract on the chitosan/PLGA scaffolds bioactivity

Allium cepa extracts (AC) allow the fabrication of a biomaterial that, together with chitosan and PLGA, could be osteoconductive and promote a better and faster regeneration of bone tissue, with biocompatibility and biomineralization properties. In this work, scaffolds were developed by the thermally induced phase separation (TIPS) technique. An in vitro bioactivity analysis was performed using simulated body fluid (SBF). Scanning electron microscopy (SEM), energy dispersion spectroscopy, and infrared spectroscopy were used for the scaffolds characterization. The results showed a structure with a pore size distribution between 50 and 100 μm, which allowed the uniform formation of biological apatite crystals on the surface of the scaffolds. The chitosan/policaprolactone/Allium cepa scaffold (ChPAC) showed the most promising results with a ratio of P/Ca between 1.6 and 1.7, a value very close to that of hydroxyapatite.

Bone tissue engineering gelatin-hydroxyapatite/graphene oxide scaffolds with the ability to release vitamin D: fabrication, characterization, and in vitro study.

Developing smart scaffolds with drug release capability is one of the main approaches to bone tissue engineering. The current study involves the fabrication of novel gelatin (G)-hydroxyapatite (HA)-/vitamin D (VD)-loaded graphene oxide (GO) scaffolds with different concentrations through solvent-casting method. Characterizations confirmed the successful synthesis of HA and GO, and VD was loaded in GO with 36.87 ± 4.87% encapsulation efficiency. Physicochemical characterizations showed that the scaffold containing 1% VD-loaded GO had the best mechanical properties and its porosity percentage and density was in the range of natural spongy bone. All scaffolds were degraded after 1-month, subjecting to phosphate buffer saline. The release profile of VD did not match any mathematical kinetics model, porosities and the degradation rate of the scaffolds were dominant controlling factors of release behavior. Studies on the bioactivity of scaffolds immersed in simulated body fluid indicated that VD and HA could encourage the formation of secondary apatite crystals in vitro. Buccal fat pad-derived stem cells (BFPSCs) were seeded on the scaffolds, MTT assay, alkaline phosphatase activity as an indicator of osteoconductivity, and cell adhesion were conducted in order to evaluate in vitro biological responses. All scaffolds highly supported cell adhesion, MTT assay indicated better cell viability in 0.5% VD-loaded GO containing scaffold, and the scaffold enriched with 2% VD-loaded GO performed the most ALP activity. The results demonstrated the potential of these scaffolds to induce bone regeneration. Developing smart scaffolds with drug release capability is one of the main approaches to bone tissue engineering. The current study involves the fabrication of novel gelatin (G)-hydroxyapatite (HA)-/vitamin D (VD)-loaded graphene oxide (GO) scaffolds with different concentrations through solvent-casting method. Characterizations confirmed the successful synthesis of HA and GO, and VD was loaded in GO with 36.87 ± 4.87% encapsulation efficiency. Physicochemical characterizations showed that the scaffold containing 1% VD-loaded GO had the best mechanical properties and its porosity percentage and density was in the range of natural spongy bone. All scaffolds were degraded after 1-month, subjecting to phosphate buffer saline. The release profile of VD did not match any mathematical kinetics model, porosities and the degradation rate of the scaffolds were dominant controlling factors of release behavior. Studies on the bioactivity of scaffolds immersed in simulated body fluid indicated that VD and HA could encourage the formation of secondary apatite crystals in vitro. Buccal fat pad-derived stem cells (BFPSCs) were seeded on the scaffolds, MTT assay, alkaline phosphatase activity as an indicator of osteoconductivity, and cell adhesion were conducted in order to evaluate in vitro biological responses. All scaffolds highly supported cell adhesion, MTT assay indicated better cell viability in 0.5% VD-loaded GO containing scaffold, and the scaffold enriched with 2% VD-loaded GO performed the most ALP activity. The results demonstrated the potential of these scaffolds to induce bone regeneration.

The Effect of Poly (Vynil Pyrrolidine) (PVP) Added in Variation of Ca2+ and PO43- Concentration in Microbial Cellulose-Hydroxyapatite Composite As Scaffold For Bone Healing

In Indonesia, the traffic accident causing 6 million people suffered injuries, particularly injuries fractures. 46.2% incidence of fractures occur in the lower extremities, 25% of them dying, 45% had a physical disability, 15% experienced psychological pressure and only 10% were healed well. Implant (graft) are used to support and accelerate the healing process of broken bones (bone healing). This study was done to make microbial cellulose-hydroxyapatite scaffold as a candidate for bone healing. Microbial cellulose obtained from culturing Acetobacter xylinum is used as a matrix and hydroxyapatite as a filler that is synthesized using the method of immersion in a solution of CaCl2 and KH2PO4, to increase the formation of apatite crystals, added polyvinyl Pyrrolidine (PVP). Scaffold synthesized using methods of freeze dried. Formation of composites varied in the concentration of Ca2+ and PO 3- of 25:125; 50:100; 75:75; 100:50 mM. The samples were then characterized using FTIR spectroscopy which shows the phosphate groups and the carbonate indicates the formation of hydroxyapatite in the eighth sample. Furthermore, to determine the morphology and identify the elements in the scaffold used SEM-EDAX, it was found that the pore formed measuring about 150-300 μm and obtained ratio of Ca / P best on microbial cellulose scaffold-PVP-hydroxyapatite with a variation of the concentration of Ca2+ and PO43- of 100 : 50 mM is equal to 0.6046 with an average degradation rate of 18.617% and the percentage of porosity contained in the sample amounted to 88.4%. This proves that microbial cellulose scaffold-PVP-hydroxyapatite with a variation of the concentration of Ca2+ and PO43- of 100:50 mM potential as a candidate for bone healing.

New Nano-Bioactive Glass/Magnesium Phosphate Composites by Sol-Gel Route for Bone Defect Treatment

This work was mainly aimed to synthesize new ceramic composites based on nano-bioactive glass (nBG) and magnesium phosphate ceramic (MgP) with different ratios using the sol-gel approach in order to overcome the limitations of both materials. The glass was based on 85SiO2-10CaO-5P2O5 (mole %), and MgP was based on the formula; Mg3(PO4)2. The obtained composites were characterized by DTA, XRD, FTIR, SEM/EDX and Zeta potential techniques. The in vitro bioactivity test was carried out in SBF, and the cell viability test was conducted by culturing the composites with human normal fibroblast cell line (BJ1). The results of XRD analyses showed that there were often no strong diffraction peaks detected which indicated the amorphous nature of the ceramic composites. Moreover, soaking of the ceramic composites in SBF exhibited that addition of MgP to nBG was increased the degradation of the latter one, and nBG was improved the formation of apatite crystals on MgP ceramic. Moreover, the cell viability results showed that MgP was showed significant higher viability than nBG at high concentrations, and it improved the viability of nBG in the ceramic composites.

Indirect printing of hierarchical patient-specific scaffolds for meniscus tissue engineering

The complex meniscus tissue plays a critical role in the knee. The high susceptibility to injury has led to an intense pursuit for better tissue engineering regenerative strategies, where scaffolds play a major role. In this study, indirect printed hierarchical multilayered scaffolds composed by a silk fibroin (SF) upper layer and an 80/20 (w/w) ratio of SF/ionic-doped β-tricalcium phosphate (TCP) bottom layer were developed. Furthermore, a comparative analysis between two types of scaffolds produced using different SF concentrations, i.e., 8% (w/v) (Hi8) and 16% (w/v) (Hi16) was performed. In terms of architecture and morphology, the produced scaffolds presented homogeneous porosity in both layers and no differences were observed when comparing both scaffolds. A decrease in terms of mechanical performance of the scaffolds was observed when SF concentration decreased from 16 to 8% (w/v). Hi16 revealed a static compressive modulus of 0.66 ± 0.05 MPa and dynamical mechanical properties ranging from 2.17 ± 0.25 to 3.19 ± 0.38 MPa. By its turn, Hi8 presented a compressive modulus of 0.27 ± 0.08 MPa and dynamical mechanical properties ranging from 1.03 ± 0.08 MPa to 1.56 ± 0.13 MPa. In vitro bioactivity studies showed formation of apatite crystals onto the surface of Hi8 and Hi16 bottom layers. Human meniscus cells (hMCs) and human primary osteoblasts were cultured separately onto the top layer (SF8 and SF16) and bottom layer (SF8/TCP and SF16/TCP) of the hierarchical scaffolds Hi8 and Hi16, respectively. Both cell types showed good adhesion and proliferation as denoted by the live/dead staining, Alamar Blue assay and DNA quantification analysis. Subcutaneous implantation in mice revealed weak inflammation and scaffold’s integrity. The hierarchical indirect printed SF scaffolds can be promising candidate for meniscus TE scaffolding applications due their suitable mechanical properties, good biological performance and possibility of being applied in a patient-specific approach.

BIOCOMPATIBILITY OF HAp/CNTs COATING ON Ti6Al4V ALLOY INTO THE SIMULATED BODY FLUID SOLUTION

Hydroxyapatite doped carbon nanotubes (HAp/CNTs) was synthesized successfully as a coating on the surface of titanium alloy (Ti6Al4V) by a scanning potential method. The biocompatibility of the materials soaked into a simulated body fluid solution (SBF) were investigated. SEM images are observed that the formation of new apatite crystals on the surface of Ti6Al4V with HAp or HAp/CNTs coating is better than that of Ti6Al4V. The formed apatite crystals are confirmed by XRD result of Ti6Al4V after 21 soaked days in SBF solution. These results indicated that the coatings of HAp or HAp/CNTs have a good biocompatibility.

Enzymatically Cross-Linked Silk Fibroin-Based Hierarchical Scaffolds for Osteochondral Regeneration.

Osteochondral (OC) regeneration faces several limitations in orthopedic surgery, owing to the complexity of the OC tissue that simultaneously entails the restoration of articular cartilage and subchondral bone diseases. In this study, novel biofunctional hierarchical scaffolds composed of a horseradish peroxidase (HRP)-cross-linked silk fibroin (SF) cartilage-like layer (HRP-SF layer) fully integrated into a HRP-SF/ZnSr-doped β-tricalcium phosphate (β-TCP) subchondral bone-like layer (HRP-SF/dTCP layer) were proposed as a promising strategy for OC tissue regeneration. For comparative purposes, a similar bilayered structure produced with no ion incorporation (HRP-SF/TCP layer) was used. A homogeneous porosity distribution was achieved throughout the scaffolds, as shown by micro-computed tomography analysis. The ion-doped bilayered scaffolds presented a wet compressive modulus (226.56 ± 60.34 kPa) and dynamic mechanical properties (ranging from 403.56 ± 111.62 to 593.56 ± 206.90 kPa) superior to that of the control bilayered scaffolds (189.18 ± 90.80 kPa and ranging from 262.72 ± 59.92 to 347.68 ± 93.37 kPa, respectively). Apatite crystal formation, after immersion in simulated body fluid (SBF), was observed in the subchondral bone-like layers for the scaffolds incorporating TCP powders. Human osteoblasts (hOBs) and human articular chondrocytes (hACs) were co-cultured onto the bilayered structures and monocultured in the respective cartilage and subchondral bone half of the partitioned scaffolds. Both cell types showed good adhesion and proliferation in the scaffold compartments, as well as adequate integration of the interface regions. Osteoblasts produced a mineralized extracellular matrix (ECM) in the subchondral bone-like layers, and chondrocytes showed GAG deposition. The gene expression profile was different in the distinct zones of the bilayered constructs, and the intermediate regions showed pre-hypertrophic chondrocyte gene expression, especially on the BdTCP constructs. Immunofluorescence analysis supported these observations. This study showed that the proposed bilayered scaffolds allowed a specific stimulation of the chondrogenic and osteogenic cells in the co-culture system together with the formation of an osteochondral-like tissue interface. Hence, the structural adaptability, suitable mechanical properties, and biological performance of the hierarchical scaffolds make these constructs a desired strategy for OC defect regeneration.

Calcium release and physical properties of modified carbonate apatite cement as pulp capping agent in dental application

BackgroundCarbonate apatite (CO3Ap) and silica-calcium phosphate composite (SCPC) are bone substitutes with good prospect for dental application. SCPC creates a hydroxyapatite surface layer and stimulate bone cell function while, CO3Ap induce apatite crystal formation with good adaptation providing good seal between cement and the bone. Together, these materials will add favorable properties as a pulp capping material to stimulate mineral barrier and maintain pulp vitality. The aim of this study is to investigate modification of CO3Ap cement combined with SCPC, later term as CO3Ap-SCPC cement (CAS) in means of its chemical (Calcium release) and physical properties (setting time, DTS and pH value).MethodsThe study consist of three groups; group 1 (100% calcium hydroxide, group 2 CO3Ap (60% DCPA: 40% vaterite, and group 3 CAS (60% DCPA: 20% vaterite: 20% SCPC. Distilled water was employed as a solution for group 1, and 0.2 mol/L Na3PO4 used for group 2 and group 3.Samples were evaluated with respect to important properties for pulp capping application such as pH, setting time, mechanical strength and calcium release evaluation.ResultsThe fastest setting time was in CO3Ap cement group without SCPC, while the addition of 20% SCPC slightly increase the pH value but did not improved the cement mechanical strength, however, the mechanical strength of both CO3Ap groups were significantly higher than calcium hydroxide. All three groups released calcium ions and had alkaline pH. Highest pH level, as well as calcium released level, was in the control group.ConclusionThe CAS cement had good mechanical and acceptable chemical properties for pulp capping application compared to calcium hydroxide as a gold standard. However, improvements and in vivo studies are to be carried out with the further development of this material.

Expression and function of Slc34 sodium-phosphate co-transporters in skeleton and teeth.

Under normal physiological condition, the biomineralization process is limited to skeletal tissues and teeth and occurs throughout the individual's life. Biomineralization is an actively regulated process involving the progressive mineralization of the extracellular matrix secreted by osteoblasts in bone or odontoblasts and ameloblasts in tooth. Although the detailed molecular mechanisms underlying the formation of calcium-phosphate apatite crystals are still debated, it is suggested that calcium and phosphate may need to be transported across the membrane of the mineralizing cell, suggesting a pivotal role of phosphate transporters in bone and tooth mineralization. In this context, this short review describes the current knowledge on the role of Slc34 Na+-phosphate transporters in skeletal and tooth mineralization.

Pyrophosphate-Inhibition of Apatite Formation Studied by In Situ X-Ray Diffraction

The pathways to crystals are still under debate, especially for materials relevant to biomineralization, such as calcium phosphate apatite known from bone and teeth. Pyrophosphate is widely used in biology to control apatite formation since it is a potent inhibitor of apatite crystallization. The impacts of pyrophosphate on apatite formation and crystallization kinetics are, however, not fully understood. Therefore, we studied apatite crystallization in water by synchrotron in situ X-ray diffraction. Crystallization was conducted from calcium chloride (0.2 M) and sodium phosphate (0.12 M) at pH 12 where hydrogen phosphate is the dominant phosphate species and at 60 °C to allow the synchrotron measurements to be conducted in a timely fashion. Following the formation of an initial amorphous phase, needle shaped crystals formed that had an octacalcium phosphate-like composition, but were too small to display the full 3D periodic structure of octacalcium phosphate. At later growth stages the crystals became apatitic, as revealed by changes in the lattice constant and calcium content. Pyrophosphate strongly inhibited nucleation of apatite and increased the onset of crystallization from minute to hour time scales. Pyrophosphate also reduced the rate of growth. Furthermore, when the pyrophosphate concentration exceeded ~1% of the calcium concentration, the resultant crystals had reduced size anisotropy suggesting that pyrophosphate interacts in a site-specific manner with the formation of apatite crystals.