Mesenchymal Stem Cell Exosomes Enhance Posterolateral Spinal Fusion in a Rat Model.

Spinal fusion, a common surgery performed for degenerative lumbar conditions, often uses recombinant human bone morphogenetic protein 2 (rhBMP-2) that is associated with adverse effects. Mesenchymal stromal/stem cells (MSCs) and their extracellular vesicles (EVs), particularly exosomes, have demonstrated efficacy in bone and cartilage repair. However, the efficacy of MSC exosomes in spinal fusion remains to be ascertained. This study investigates the fusion efficacy of MSC exosomes delivered via an absorbable collagen sponge packed in a poly Ɛ-caprolactone tricalcium phosphate (PCL-TCP) scaffold in a rat posterolateral spinal fusion model. Herein, it is shown that a single implantation of exosome-supplemented collagen sponge packed in PCL-TCP scaffold enhanced spinal fusion and improved mechanical stability by inducing bone formation and bridging between the transverse processes, as evidenced by significant improvements in fusion score and rate, bone structural parameters, histology, stiffness, and range of motion. This study demonstrates for the first time that MSC exosomes promote bone formation to enhance spinal fusion and mechanical stability in a rat model, supporting its translational potential for application in spinal fusion.

Development of cell-laden photopolymerized constructs with bioactive amorphous calcium magnesium phosphate for bone tissue regeneration via 3D bioprinting.

The synthesis of ideal bioceramics to guide the fate of cells and subsequent bone regeneration within the chemical, biological, and physical microenvironment is a challenging long-term task. This study developed amorphous calcium magnesium phosphate (ACMP) bioceramics via a simple co-precipitation method. The role of Mg2+ in the formation of ACMP is investigated using physicochemical and biological characterization at different Ca/Mg molar ratio of the initial reaction solution. Additionally, ACMP bioceramics show superior cytocompatibility and improved osteogenic differentiation of co-cultured MC3T3-E1 cells. Regulation of the microenvironment with Mg2+ can promote early-stage bone regeneration. For this, bioprinting technology is employed to prepare ACMP-modified 3D porous structures. Our hypothesis is that the incorporation of ACMP into methacrylated gelatin (GelMA) bioink can trigger the osteogenic differentiation of encapsulated preosteoblast and stimulate bone regeneration. The cell-laden ACMP composite structures display stable printability and superior cell viability and cell proliferation. Also, constructs loading the appropriate amount of ACMP bioceramic showed significant osteogenic differentiation activity compared to the pure GelMA. We demonstrate that the dissolved Mg2+ cation microenvironment in ACMP-modified composite constructs plays an effective biochemical role, and can regulate cell fate. Our results predict that GelMA/ACMP bioink has significant potential in patient-specific bone tissue regeneration.

Osteosarcoma cell death induced by innovative scaffolds doped with chemotherapeutics.

Osteosarcoma (OS) cancer treatments include systemic chemotherapy and surgical resection. In the last years, novel treatment approaches have been proposed, which employ a drug-delivery system to prevent offside effects and improves treatment efficacy. Locally delivering anticancer compounds improves on high local concentrations with more efficient tumour-killing effect, reduced drugs resistance and confined systemic effects. Here, the synthesis of injectable strontium-doped calcium phosphate (SrCPC) scaffold was proposed as drug delivery system to combine bone tissue regeneration and anticancer treatment by controlled release of methotrexate (MTX) and doxorubicin (DOX), coded as SrCPC-MTX and SrCPC-DOX, respectively. The drug-loaded cements were tested in an in vitro model of human OS cell line SAOS-2, engineered OS cell line (SAOS-2-eGFP) and U2-OS. The ability of doped scaffolds to induce OS cell death and apoptosis was assessed analysing cell proliferation and Caspase-3/7 activities, respectively. To determine if OS cells grown on doped-scaffolds change their migratory ability and invasiveness, a wound-healing assay was performed. In addition, the osteogenic potential of SrCPC material was evaluated using human adipose derived-mesenchymal stem cells. Osteogenic markers such as (i) the mineral matrix deposition was analysed by alizarin red staining; (ii) the osteocalcin (OCN) protein expression was investigated by enzyme-linked immunosorbent assay test, and (iii) the osteogenic process was studied by real-time polymerase chain reaction array. The delivery system induced cell-killing cytotoxic effects and apoptosis in OS cell lines up to Day 7. SrCPC demonstrates a good cytocompatibility and it induced upregulation of osteogenic genes involved in the skeletal development pathway, together with OCN protein expression and mineral matrix deposition. The proposed approach, based on the local, sustained release of anticancer drugs from nanostructured biomimetic drug-loaded cements is promising for future therapies aiming to combine bone regeneration and anticancer local therapy.

Injectable, anti-collapse, adhesive, plastic and bioactive bone graft substitute promotes bone regeneration by moderating oxidative stress in osteoporotic bone defect.

The treatment of osteoporotic bone defect remains a big clinical challenge because osteoporosis (OP) is associated with oxidative stress and high levels of reactive oxygen species (ROS), a condition detrimental for bone formation. Anti-oxidative nanomaterials such as selenium nanoparticles (SeNPs) have positive effect on osteogenesis owing to their pleiotropic pharmacological activity which can exert anti-oxidative stress functions to prevent bone loss and facilitate bone regeneration in OP. In the current study a strategy of one-pot method by introducing Poly (lactic acid-carbonate) (PDT) and ß-Tricalcium Phosphate (ß-TCP) with SeNPs, is developed to prepare an injectable, anti-collapse, shape-adaptive and adhesive bone graft substitute material (PDT-TCP-SE). The PDT-TCP-SE bone graft substitute exhibits sufficient adhesion in biological microenvironments and osteoinductive activity, angiogenic effect and anti-inflammatory as well as anti-oxidative effect in vitro and in vivo. Moreover, the PDT-TCP-SE can protect BMSCs from erastin-induced ferroptosis through the Sirt1/Nrf2/GPX4 antioxidant pathway, which, in together, demonstrated the bone graft substitute material as an emerging biomaterial with potential clinical application for the future treatment of osteoporotic bone defect. STATEMENT OF SIGNIFICANCE: Injectable, anti-collapse, adhesive, plastic and bioactive bone graft substitute was successfully synthesized. Incorporation of SeNPs with PDT into ß-TCP regenerated new bone in-situ by moderating oxidative stress in osteoporotic bone defects area. The PDT-TCP-SE bone graft substitute reduced high ROS levels in osteoporotic bone defect microenvironment. The bone graft substitute could also moderate oxidative stress and inhibit ferroptosis via Sirt1/Nrf2/GPX4 pathway in vitro. Moreover, the PDT-TCP-SE bone graft substitute could alleviate the inflammatory environment and promote bone regeneration in osteoporotic bone defect in vivo. This biomaterial has the advantages of simple synthesis, biocompatibility, anti-collapse, injectable, and regulation of oxidative stress level, which has potential application value in bone tissue engineering.

Injectable in situ gelling methylcellulose-based hydrogels for bone tissue regeneration.

Injectable bone substitutes (IBSs) represent a compelling choice for bone tissue regeneration, as they can be exploited to optimally fill complex bone defects in a minimally invasive manner. In this context, in situ gelling methylcellulose (MC) hydrogels may be engineered to be free-flowing injectable solutions at room temperature and gels upon exposure to body temperature. Moreover, incorporating a suitable inorganic phase can further enhance the mechanical properties of MC hydrogels and promote mineralization, thus assisting early cell adhesion to the hydrogel and effectively guiding bone tissue regeneration. In this work, thermo-responsive IBSs were designed selecting MC as the organic matrix and calcium phosphate (CaP) or CaP modified with graphene oxide (CaPGO) as the inorganic component. The resulting biocomposites displayed a transition temperature around body temperature, preserved injectability even after loading with the inorganic components, and exhibited adequate retention on an ex vivo calf femoral bone defect model. The addition of CaP and CaPGO promoted the in vitro mineralization process already 14 days after immersion in simulated body fluid. Interestingly, combined X-ray diffraction and solid state nuclear magnetic resonance characterizations revealed that the formed biomimetic phase was constituted by crystalline hydroxyapatite and amorphous calcium phosphate. In vitro biological characterization revealed the beneficial impact of CaP and CaPGO, indicating their potential in promoting cell adhesion, proliferation and osteogenic differentiation. Remarkably, the addition of GO, which is very attractive for its bioactive properties, did not negatively affect the injectability of the hydrogel nor the mineralization process, but had a positive impact on cell growth and osteogenic differentiation on both pre-differentiated and undifferentiated cells. Overall, the proposed formulations represent potential candidates for use as IBSs for application in bone regeneration both under physiological and pathological conditions.

Novel self-setting cements based on tricalcium silicate/(ß-tricalcium phosphate/monocalcium phosphate anhydrous)/hydroxypropyl methylcellulose: From hydration mechanism to biological evaluations.

Despite the clinical success of tricalcium silicate (TCS)-based materials in endodontics, the inferior handling characteristic, poor anti-washout property and slow setting kinetics hindered their wider applications. To solve these problems, an injectable fast-setting TCS/ß-tricalcium phosphate/monocalcium phosphate anhydrous (ß-TCP/MCPA) cement was developed for the first time by incorporation of hydroxypropyl methylcellulose (HPMC) and ß-TCP/MCPA. The physical-chemical characterization (setting time, anti-washout property, injectability, compressive strength, apatite mineralization and sealing property) of TCS/(ß-TCP/MCPA) were conducted. Its hydration mechanism was also investigated. Furthermore, the cytocompatibility and osteogenic/odontogenic differentiation of stem cells isolated from human exfoliated deciduous teeth (SHED) treated with TCS/ß-TCP/MCPA were studied. The results showed that HPMC could provide TCS with good anti-washout ability and injectability but slow hydration process. However, ß-TCP/MCPA effectively enhanced anti-washout characteristics and reduced setting time due to faster hydration kinetics. TCS/(ß-TCP/MCPA) obtained around 90 % of injection rate and high compressive strength whereas excessive additions of ß-TCP/MCPA compromised its injectability and compressive strength. TCS/(ß-TCP/MCPA) can induce apatite deposition and form a tight marginal sealing at the dentin-cement interface. Additionally, TCS/(ß-TCP/MCPA) showed good biocompatibility and promoted osteo/odontogenic differentiation of SHED. In general, our results indicated that TCS/(ß-TCP/MCPA) may be particularly promising as an injectable bioactive cements for endodontic treatment.

Magnesium-oxide-enhanced bone regeneration: 3D-printing of gelatin-coated composite scaffolds with sustained Rosuvastatin release.

Critical-size bone defects are one of the main challenges in bone tissue regeneration that determines the need to use angiogenic and osteogenic agents. Rosuvastatin (RSV) is a class of cholesterol-lowering drugs with osteogenic potential. Magnesium oxide (MgO) is an angiogenesis component affecting apatite formation. This study aims to evaluate 3D-printed Polycaprolactone/ß-tricalcium phosphate/nano-hydroxyapatite/ MgO (PCL/ß-TCP/nHA/MgO) scaffolds as a carrier for MgO and RSV in bone regeneration. For this purpose, PCL/ß-TCP/nHA/MgO scaffolds were fabricated with a 3D-printing method and coated with gelatin and RSV. The biocompatibility and osteogenicity of scaffolds were examined with MTT, ALP, and Alizarin red staining. Finally, the scaffolds were implanted in a bone defect of rat's calvaria, and tissue regeneration was investigated after 3 months. Our results showed that the simultaneous presence of RSV and MgO improved biocompatibility, wettability, degradation rate, and ALP activity but decreased mechanical strength. PCL/ß-TCP/nHA/MgO/gelatin-RSV scaffolds produced sustained release of MgO and RSV within 30 days. CT images showed that PCL/ß-TCP/nHA/MgO/gelatin-RSV scaffolds filled approximately 86.83 + 4.9 % of the defects within 3 months and improved angiogenesis, woven bone, and osteogenic genes expression. These results indicate the potential of PCL/ß-TCP/nHA/MgO/gelatin-RSV scaffolds as a promising tool for bone regeneration and clinical trials.

Surface functionalization of calcium magnesium phosphate cements with alginate sodium for enhanced bone regeneration via TRPM7/PI3K/Akt signaling pathway.

Although calcium­magnesium phosphate cements (CMPCs) have been widely applied to treating critical-size bone defects, their repair efficiency is unsatisfactory owing to their weak surface bioactivity and uncontrolled ion release. In this study, we lyophilized alginate sodium (AS) as a coating onto HAp/K-struvite (H@KSv) to develop AS/HAp/K-struvite (AH@KSv), which promotes bone regeneration. The compressive strength and hydrophilicity of AH@KSv significantly improved, leading to enhanced cell adhesion in vitro. Importantly, the SA coating enables continuous ions release of Mg2+ and Ca2+, finally leading to enhanced osteogenesis in vitro/vivo and different patterns of new bone ingrowth in vivo. Furthermore, these composites increased the expression levels of biomarkers of the TRPM7/PI3K/Akt signaling pathway via an equilibrium effect of Mg2+ to Ca2+. In conclusion, our study provides novel insights into the mechanisms of Mg-based biomaterials for bone regeneration.

Fabrication and characterization of a bioactive composite scaffold based on polymeric collagen/gelatin/nano ß-TCP for alveolar bone regeneration.

One strategy to correct alveolar bone defects is use of bioactive bone substitutes to maintain the structure of defect site and facilitate cells and vessels' ingrowth. This study aimed to fabricate and characterize the freeze-dried bone regeneration scaffolds composed of polymeric Type I collagen, nano Beta-tricalcium phosphate (ß-TCP), and gelatin. The stable structures of scaffolds were obtained by thermal crosslinking and EDC/NHS ((1-ethyl-3-(3-dimethylaminopropyl) carbodiimide)/(N-hydroxysuccinimide)) chemical crosslinking processes. Subsequently, the physicochemical and biological properties of the scaffolds were characterized and assessed. The results indicated the bioactive composite scaffolds containing 10% and 20% (w/v) nano ß-TCP exhibited suitable porosity (84.45 ± 25.43 nm, and 94.51 ± 14.69 nm respectively), a rapid swelling property (reaching the maximum swelling rate at 1 h), excellent degradation resistance (residual mass percentage of scaffolds higher than 80% on day 90 in PBS and Type I collagenase solution respectively), and sustained calcium release capabilities. Moreover, they displayed outstanding biological properties, including superior cell viability, cell adhesion, and cell proliferation. Additionally, the scaffolds containing 10% and 20% (w/v) nano ß-TCP could promote the osteogenic differentiation of MC3T3-E1. Therefore, the bioactive composite scaffolds containing 10% and 20% (w/v) nano ß-TCP could be further studied for being used to treat alveolar bone defects in vivo.

Characterisation of experimental flowable composites containing fluoride-doped calcium phosphates as promising remineralising materials.

OBJECTIVE: Remineralising composites with antibacterial properties may seal the cavity and prevent secondary caries. This study aimed at developing experimental flowable composites containing different concentrations of fluoride-doped calcium phosphate fillers and evaluating their remineralising and antibacterial properties. METHODS: Experimental resin-based composites containing different concentrations (0-20 %) of fluoride-doped calcium phosphate fillers (VS10/VS20) were formulated. The release of calcium (Ca), phosphate (PO) and fluoride (F) ions was assessed for 30 days. Remineralisation properties were evaluated through ATR-FTIR and SEM/EDX after storage in simulated body fluid (SBF). The metabolic activity and viability of Streptococcus gordonii was also evaluated through ATP, CFU and live/dead confocal microscopy. The evaluation of specific monomer elution from the experimental composites was conducted using high-performance liquid chromatography (HPLC). RESULTS: The composites containing VS10 showed the highest release of Ca, those containing VS20 released more F over time (p < 0.05), while there was no significant difference in terms of PO ions release between the groups (p > 0.05). A quick 7-day mineral precipitation was observed in the tested composites containing VS10 or VS20 at 10 %; these materials also showed the greatest antibacterial activity (p < 0.05). Moreover, the tested composites containing VS10 presented the lowest elution of monomers (p < 0.05). CONCLUSIONS: Innovative composites were developed with low monomers elution, evident antibacterial activity against S. gordonii and important remineralisation properties due to specific ions release. CLINICAL SIGNIFICANCE: Novel composites containing fluoride-doped calcium phosphates may be promising to modulate bacteria growth, promote remineralisation and reduce the risk of cytotoxicity related to monomers' elution.

The effect of combined use of resin infiltration with different bioactive calcium phosphate-based approaches on enamel white spot lesions: An in vitro study.

OBJECTIVES: This in vitro study aimed to evaluate the effect of resin infiltration combined with casein phosphopeptide-amorphous calcium phosphate with fluoride (CPP-ACPF) or bioactive glass (BAG) on the stability of enamel white spot lesions (WSLs) treatment. MATERIALS AND METHODS: Eighty-four enamel blocks were prepared from the buccal surfaces of sound human premolars. All enamel blocks were placed in a demineralisation solution for 3 days to establish the artificial enamel WSLs. Enamel blocks with WSLs were randomly divided into three groups (n = 28 each group): RI/B: one-off resin infiltration followed by twice daily BAG treatment; RI/C: one-off resin infiltration followed by twice daily CPP-ACPF treatment; RI: one-off resin infiltration treatment only (as control) and subjected to pH cycling for 7 days. Surface morphology, elemental analysis, crystal characteristics, surface roughness and microhardness of enamel surfaces were investigated by scanning electron microscopy and energy-dispersive spectrometry observation, X-ray diffraction (XRD), atomic force microscope and Vickers' hardness testing, respectively. RESULTS: Mean values of the surface roughness (mean±standard deviation (nm)) were 24.52±5.07, 27.39±5.87 and 34.36±4.55 for groups RI/B, RI/C and RI respectively (p = 0.003). The calcium to phosphate ratios were 1.32±0.16, 1.22±0.26 and 0.69±0.24 for groups RI/B, RI/C and RI respectively (p < 0.001). XRD revealed apatite formation in all three groups. The mean enamel surface microhardness (kg/mm2) of the groups were 353.93±28.49, 339.00±27.32 and 330.38±22.55 for groups RI/B, RI/C and RI respectively (p = 0.216). CONCLUSIONS: Resin infiltration combined with CPP-ACPF or BAG remineralisation appears to improve the surface properties of WSLs. CLINICAL SIGNIFICANCE: The combination of resin infiltration and CPP-ACPF/BAG remineralisation may be a potential treatment for the management of the WSLs.

Synergistic effects of calcium silicate/zinc silicate dual compounds andin-situinterconnected pores on promoting bone regeneration of composite scaffolds.

Rapid bone regeneration in implants is important for successful transplantation. In this regard, we report the development of calcium silicate/zinc silicate (CS/ZS) dual-compound-incorporated calcium phosphate cement (CPC) scaffolds with a three-dimensional poly (lactic-co-glycolic acid) network that synergistically promote bone regeneration.In vitroresults demonstrated that the incorporation of CS/ZS dual compounds into the CPC significantly promoted the osteogenic differentiation of stem cells compared to the addition of CS or ZS alone. Moreover, the bone-regeneration efficacy of the composite scaffolds was validated by filling in femur condyle defects in rabbits, which showed that the scaffolds with CS and ZS possessed a great bone repair effect, as evidenced by more new bone formation and a faster scaffold biodegradation compared to the scaffold with CS alone.

Biocompatibility and Osseointegration of the Biomimetically Coated and Water-Soluble Eggshell Membrane Protein Cross-Linked Ti Alloy Screws.

Background: The surface properties of dental and orthopedic implants are directly related to their osseointegration rate. Coating and/or modifying the implant surface might reduce the time of healing. In this study, we aimed to examine the effects of a hybrid surface consisting of a brushite surface coating and cross-linked water-soluble eggshell membrane protein on the osseointegration of titanium (Ti) screws under in vivo conditions. Methods: Twenty Ti alloy screws were implanted monocortically in anteromedial regions of New Zealand rabbit tibiae. Ten screws were untreated and used as controls. The remaining 10 screws were coated with calcium phosphate and following cross-linked with ostrich eggshell membrane protein. All rabbits were sacrificed six weeks after the surgery. Peri-screw tissues were evaluated by micro-computed tomography (µ-CT), histological and histomorphometrical methods. Results: The µ-CT assessments indicated that the experimental group had significantly higher mean bone surface area (BSA) and trabeculae number (TbN) than those of the control group (p ˂ 0.05). Bone surface area (BV), trabecular separation (TbSp), trabecular thickness (TbTh), and bone mineral density (BMD) scores of the control and experimental groups were quite similar (p > 0.05). The vascularization score of the experimental group was significantly higher than the control group (4.29 vs. 0.92%). No sign of the graft-versus-host reaction was observed. Conclusion: Our findings reveal that coating Ti alloy implants with calcium phosphate cross-linked with ostrich eggshell membrane protein increases the osseointegration of Ti alloy screws by increasing the bone surface area, number of trabeculae and vascularization in the implant site.

Effects of vehicles on the physical properties and biocompatibility of premixed calcium silicate cements.

Premixed calcium silicate cements (pCSCs) contain vehicles which endow fluidity and viscosity to CSCs. This study aimed to investigate the effects of three vehicles, namely, polyethylene glycol (PEG), propylene glycol (PG), and dimethyl sulfoxide (DMSO), on the physicochemical properties and biocompatibility of pCSCs. The setting time, solubility, expansion rate, and mechanical strength of the pCSCs were evaluated, and the formation of calcium phosphate precipitates was assessed in phosphate-buffered saline (PBS). The effects of pCSC extracts on the osteogenic differentiation of mesenchymal stem cells (MSCs) were investigated. Finally, the tissue compatibility of pCSCs in rat femurs was observed. CSC containing PEG (CSC-PEG) exhibited higher solubility and setting time, and CSC-DMSO showed the highest expansion rate and mechanical strength. All pCSCs generated calcium phosphate precipitates. The extract of CSC-PG induced the highest expressions of osteogenic markers along with the greatest calcium deposites. When implanted in rat femurs, CSC-PEG was absorbed considerably, whereas CSC-PG remained relatively unaltered inside the femur.

Simultaneous Regulation of the Mechanical/Osteogenic Capacity of Brushite Calcium Phosphate Cement by Incorporating with Poly(ethylene glycol) Dicarboxylic Acid.

Brushite calcium phosphate cement (brushite CPC) is a prospective bone repair material due to its ideal resorption rates in vivo. However, the undesirable mechanical property and bioactivity limited its availability in clinic application. To address this issue, incorporating polymeric additives has emerged as a viable solution. In this study, poly(ethylene glycol) dicarboxylic acid, PEG(COOH), was synthesized and employed as the polymeric additive. The setting behavior, anti-washout ability, mechanical property, degradation rate, and osteogenic capacity of brushite CPC were regulated by incorporating PEG(COOH). The incorporation of PEG(COOH) with carboxylic acid groups demonstrated a positive effect on both mechanical properties and osteogenic activity in bone repair. This study offers valuable insights and suggests a promising strategy for the development of materials in bone tissue engineering.

Natural, biphasic calcium phosphate from fish bones for enamel remineralization and dentin tubules occlusion.

OBJECTIVES: A calcium phosphate extracted from fish bones (CaP-N) was evaluated for enamel remineralization and dentinal tubules occlusion. METHODS: CaP-N was characterized by assessing morphology by SEM, crystallinity by PXRD, and composition by ICP-OES. CaP-N morphology, crystallinity, ion release, and pH changes over time in neutral and acidic solutions were studied. CaP-N was then tested to assess remineralization and dentinal tubules occlusion on demineralized human enamel and dentin specimens (n = 6). Synthetic calcium phosphate in form of stoichiometric hydroxyapatite nanoparticles (CaP-S) and tap water were positive and negative controls, respectively. After treatment (brush every 12 h for 5d and storage in Dulbecco's modified PBS), specimens' morphology and surface composition were assessed (by SEM-EDS), while the viscoelastic behavior was evaluated with microindentation and DMA. RESULTS: CaP-N consisted of rounded microparticles (200 nm - 1 µm) composed of 33 wt% hydroxyapatite and 67 wt% ß-tricalcium phosphate. In acidic solution, CaP-N released calcium and phosphate ions thanks to the preferential ß-tricalcium phosphate phase dissolution. Enamel remineralization was induced by CaP-N comparably to CaP-S, while CaP-N exhibited a superior dentinal tubule occlusion than CaP-S, forming mineral plugs and depositing new nanoparticles onto demineralized collagen. This behavior was attributed to its bigger particle size and increased solubility. DMA depth profiling and SEM showed an excellent interaction between the newly formed mineralized structures and the pristine tissue, particularly at the exposed collagen fibrils. SIGNIFICANCE: CaP-N demonstrated very good remineralizing and occlusive activity in vitro, comparable to CaP-S, thus could be a promising circular economy alternative therapeutic agent for dentistry.

Amelogenin-inspired peptide, calcium phosphate solution, fluoride and their synergistic effect on enamel biomimetic remineralization: an in vitro pH-cycling model.

BACKGROUND: Several methods were introduced for enamel biomimetic remineralization that utilize a biomimetic analogue to interact and absorb bioavailable calcium and phosphate ions and induce crystal nucleation on demineralized enamel. Amelogenin is the most predominant enamel matrix protein that is involved in enamel biomineralization. It plays a major role in developing the enamel's hierarchical microstructure. Therefore, this study was conducted to evaluate the ability of an amelogenin-inspired peptide to promote the remineralization potential of fluoride and a supersaturated calcium phosphate solution in treating artificially induced enamel carious lesions under pH-cycling regimen. METHODS: Fifty enamel slices were prepared with a window (4*4 mm2 ) on the surface. Five samples were set as control healthy enamel and 45 samples were subjected to demineralization for 3 days. Another 5 samples were set as control demineralized enamel and 40 enamel samples were assigned into 8 experimental groups (n=5) (P/I, P/II, P/III, P/AS, NP/I, NP/II, NP/III and NP/AS) according to peptide treatment (peptide P or non-peptide NP) and remineralizing solution used (I; calcium phosphate solution, II; calcium phosphate fluoride solution, III; fluoride solution and AS; artificial saliva). Samples were then subjected to demineralization/remineralization cycles for 9 days. Samples in all experimental groups were evaluated using Raman spectroscopy for mineral content recovery percentage, microhardness and nanoindentation as healthy, demineralized enamel and after pH-cycling. Data were statistically analysed using two-way repeated measures Anova followed by Bonferroni-corrected post hoc test for pairwise multiple comparisons between groups. Statistical significance was set at p= 0.05. Additionally, XRD, FESEM and EDXS were used for crystal orientation, surface morphology and elemental analysis after pH-cycling. RESULTS: Nanocrystals clumped in a directional manner were detected in peptide-treated groups. P/II showed the highest significant mean values in mineral content recovery (63.31%), microhardness (268.81±6.52 VHN), elastic modulus (88.74±2.71 GPa), nanohardness (3.08±0.59 GPa) and the best crystal orientation with I002/I300 (1.87±0.08). CONCLUSION: Despite pH changes, the tested peptide was capable of remineralizing enamel with ordered crystals. Moreover, the supplementary use of calcium phosphate fluoride solution with peptide granted an enhancement in enamel mechanical properties after remineralization.

Selective Laser Melting of the Porous Ta Scaffold with Mg-Doped Calcium Phosphate Coating for Orthopedic Applications.

Addressing the repair of large-scale bone defects has become a hot research topic within the field of orthopedics. This study assessed the feasibility and effectiveness of using porous tantalum scaffolds to treat such defects. These scaffolds, manufactured using the selective laser melting (SLM) technology, possessed biomechanical properties compatible with natural bone tissue. To enhance the osteogenesis bioactivity of these porous Ta scaffolds, we applied calcium phosphate (CaP) and magnesium-doped calcium phosphate (Mg-CaP) coatings to the surface of SLM Ta scaffolds through a hydrothermal method. These degradable coatings released calcium and magnesium ions, demonstrating osteogenic bioactivity. Experimental results indicated that the Mg-CaP group exhibited biocompatibility comparable to that of the Ta group in vivo and in vitro. In terms of osteogenesis, both the CaP group and the Mg-CaP group showed improved outcomes compared to the control group, with the Mg-CaP group demonstrating superior performance. Therefore, both CaP and magnesium-CaP coatings can significantly enhance the osseointegration of three-dimensional-printed porous Ta, thereby increasing the surface bioactivity. Overall, the present study introduces an innovative approach for the biofunctionalization of SLM porous Ta, aiming to enhance its suitability as a bone implant material.

Enhanced osteogenic and bactericidal performance of premixed calcium phosphate cement with photocrosslinked alginate thin film.

The increasing prevalence of implant-associated infections (IAI) in orthopedics remains a public health challenge. Calcium phosphates (CaPs) are critical biomaterials in dental treatments and bone regeneration. It is highly desirable to endow CaPs with antibacterial properties. To achieve this purpose, we developed a photocrosslinked methacrylated alginate co-calcium phosphate cement (PMA-co-PCPC) with antibacterial properties, using α-tricalcium phosphate (α-TCP) powders with 16% amorphous contents as solid phase, liquid phases containing CuCl2 and SrCl2 as an inhibitor, and CaCl2 as an activator to construct PCPC. When CaCl2 started to activate the hydration reaction, Sr2+ or Cu2+ ions were exchanged with Ca2+, and α-TCP dissolution was restarted and gradually hydrated to form calcium-deficient hydroxyapatite (CDHA). PMA was added to crosslink with Cu/Sr ions and form gel-layer-wrapped hydrated CDHA. This study explored the binding mechanism of PMA and PCPC and the ion release rule of Ca2+ → Sr2+/Cu2+, optimized the construction of several antibacterial PMA-co-PCPC materials, and analyzed the physical, chemical, and biological properties. Because of the combined effect of Cu and Sr ions, the scaffold exhibited a potential antibacterial activity, promoting bone formation and vascular regeneration. This work provides a basis for designing antibacterial calcium phosphate biomaterials with controllable treatment, which is an important characteristic for preventing IAI of biomaterials.

Fabrication of vascularized tissue-engineered bone models using triaxial bioprinting.

Bone tissue is a highly vascularized tissue. When constructing tissue-engineered bone models, both the osteogenic and angiogenic capabilities of the construct should be carefully considered. However, fabricating a vascularized tissue-engineered bone to promote vascular formation and bone generation, while simultaneously establishing nutrition channels to facilitate nutrient exchange within the constructs, remains a significant challenge. Triaxial bioprinting, which not only allows the independent encapsulation of different cell types while simultaneously forming nutrient channels, could potentially emerge as a strategy for fabricating vascularized tissue-engineered bone. Moreover, bioinks should also be applied in combination to promote both osteogenesis and angiogenesis. In this study, employing triaxial bioprinting, we used a blend bioink of gelatin methacryloyl (GelMA), sodium alginate (Alg), and different concentrations of nano beta-tricalcium phosphate (nano ß-TCP) encapsulated MC3T3-E1 preosteoblasts as the outer layer, a mixed bioink of GelMA and Alg loaded with human umbilical vein endothelial cells (HUVEC) as the middle layer, and gelatin as a sacrificial material to form nutrient channels in the inner layer to fabricate vascularized bone constructs simulating the microenvironment for bone and vascular tissues. The results showed that the addition of nano ß-TCP could adjust the mechanical, swelling, and degradation properties of the constructs. Biological assessments revealed the cell viability of constructs containing different concentrations of nano ß-TCP was higher than 90% on day 7, The cell-laden constructs containing 3% (w/v) nano ß-TCP exhibited better osteogenic (higher Alkaline phosphatase activity and larger Osteocalcin positive area) and angiogenic (the gradual increased CD31 positive area) potential. Therefore, using triaxial bioprinting technology and employing GelMA, Alg, and nano ß-TCP as bioink components could fabricate vascularized bone tissue constructs, offering a novel strategy for vascularized bone tissue engineering.