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Gadolinium-containing calcium phosphates are promising contrast agents for various bioimaging modalities. Gadolinium-substituted tricalcium phosphate (TCP) powders with 0.51 wt% of gadolinium (0.01Gd-TCP) and 5.06 wt% of (0.1Gd-TCP) were synthesized by two methods: precipitation from aqueous solutions of salts (1) (Gd-TCP-pc) and mechano-chemical activation (2) (Gd-TCP-ma). The phase composition of the product depends on the synthesis method. The product of synthesis (1) was composed of β-TCP (main phase, 96%), apatite/chlorapatite (2%), and calcium pyrophosphate (2%), after heat treatment at 900 °C. The product of synthesis (2) was represented by β-TCP (main phase, 73%), apatite/chlorapatite (20%), and calcium pyrophosphate (7%), after heat treatment at 900 °C. The substitution of Ca2+ ions by Gd3+ in both β-TCP (main phase) and apatite (admixture) phases was proved by the electron paramagnetic resonance technique. The thermal stability and specific surface area of the Gd-TCP powders synthesized by two methods were significantly different. The method of synthesis also influenced the size and morphology of the prepared Gd-TCP powders. In the case of synthesis route (1), powders with particle sizes of tens of nanometers were obtained, while in the case of synthesis (2), the particle size was hundreds of nanometers, as revealed by transmission electron microscopy. The Gd-TCP ceramics microstructure investigated by scanning electron microscopy was different depending on the synthesis route. In the case of (1), ceramics with grains of 1–50 μm, pore sizes of 1–10 µm, and a bending strength of about 30 MPa were obtained; in the case of (2), the ceramics grain size was 0.4–1.4 μm, the pore size was 2 µm, and a bending strength of about 39 MPa was prepared. The antimicrobial activity of powders was tested for four bacteria (S. aureus, E. coli, S. typhimurium, and E. faecalis) and one fungus (C. albicans), and there was roughly 30% of inhibition of the micro-organism’s growth. The metabolic activity of the NCTC L929 cell and viability of the human dental pulp stem cell study demonstrated the absence of toxic effects for all the prepared ceramic materials doped with Gd ions, with no difference for the synthesis route.

Sr2+-substituted β-tricalcium phosphate (β-TCP) powders were synthesized using the mechano-chemical activation method with subsequent pressing and sintering to obtain ceramics. The concentration of Sr2+ in the samples was 0 (non-substituted TCP, as a reference), 3.33 (0.1SrTCP), and 16.67 (0.5SrTCP) mol.% with the expected Ca3(PO4)2, Ca2.9Sr0.1(PO4)2, and Ca2.5Sr0.5(PO4)2 formulas, respectively. The chemical compositions were confirmed by the energy-dispersive X-ray spectrometry (EDX) and the inductively coupled plasma optical emission spectroscopy (ICP-OES) methods. The study of the phase composition of the synthesized powders and ceramics by the powder X-ray diffraction (PXRD) method revealed that β-TCP is the main phase in all compounds except 0.1SrTCP, in which the apatite (Ap)-type phase was predominant. TCP and 0.5SrTCP ceramics were soaked in the standard saline solution for 21 days, and the phase analysis revealed the partial dissolution of the initial β-TCP phase with the formation of the Ap-type phase and changes in the microstructure of the ceramics. The Sr2+ ion release from the ceramic was measured by the ICP-OES. The human osteosarcoma MG-63 cell line was used for viability, adhesion, spreading, and cytocompatibility studies. The results show that the introduction of Sr2+ ions into the β-TCP improved cell adhesion, proliferation, and cytocompatibility of the prepared samples. The obtained results provide a base for the application of the Sr2+-substituted ceramics in model experiments in vivo.

Background: Pathological bone fracturing is an escalating problem driven by increasing aging and obesity. Bioceramics, particularly tricalcium-phosphate-based materials (TCP), are renowned for their exceptional biocompatibility, osteoconductivity, and ability to promote biomineralization. In the present study, we designed and characterized TCP porous granules doped with strontium (Sr) and copper (Cu) (CuSr TCP). Sr2+ ions were selected as Sr plays a crucial role in early bone formation, osteogenesis, and angiogenesis; Cu2+ ions possess antibacterial properties. Materials: The synthesized CuSr TCP granules were characterized by X-ray diffraction. Cytotoxicity and cell proliferation analyses’ assays were performed through the lactate dehydrogenase (LDH) activity and CCK-8 viability tests in rat bone marrow-derived mesenchymal stem cells (BM-MSCs). Hemolytic activity was carried out with human red blood cells (RBCs). Early and late osteogenesis were assessed with alkaline phosphatase (ALP) and Alizarin Red S activity in human osteoblast progenitor cells and rat BM-MSCs. The influence of CuSr TCP on angiogenesis was investigated in human umbilical vein endothelial cells (HUVECs). Results: We have demonstrated that media enriched with CuSr TCP in concentrations ranging from 0.1 mg/mL to 1 mg/mL were not cytotoxic and did not significantly affect cell proliferation rate motility. Moreover, a concentration of 0.5 mg/mL showed a 2.5-fold increase in the migration potential of BM-MSCs. We also found that CuSr TCP-enriched media slightly increased early osteogenesis. We also found that Sr and Cu substitutions in TCP particles significantly enhanced the measured angiogenic parameters compared to control and unsubstituted TCP granules. Conclusion: Our results demonstrate that TCP porous granules doped with Sr and Cu are biocompatible, promote osteodifferentiation and angiogenesis, and could be recommended for further in vivo studies.

Hydroxyapatite (HAp, Ca 10 (PO 4 ) 6 (OH) 2 ) is the major inorganic component of bones, with high bioactivity and biocompatibility, and pores in the 50–200 μm range can facilitate cell anchorage and proliferation. HAp was synthesised through a rapid sol-gel method, avoiding the usual long aging process typically required for sol-gel HAp. Acetate and nitrate precursor salts were compared, to produce bioceramics having different porosities induced via the addition of hydrogen peroxide (H 2 O 2 ) pore-forming agent. 3–10 wt% H 2 O 2 was added, and the resulting bioceramics calcined at 400 and 700 °C. Microstructure, composition, specific surface area and macro/mesoporosity were analysed, and bioactivity and cytotoxicity/biocompatibility evaluated by immersion in simulated body fluid (SBF) and MTT assays on MG63 osteoblast cell lines. When heated to 400 °C HAp was the only calcium phosphate phase present, but after heating to 700 °C they were a mixture of HAp and β-tricalcium phosphate (β-TCP, Ca 3 (PO 4 ) 2 ). The bioceramics exhibit high bioactivity, crystallising HAp from SBF, and most were biocompatible, with cell viabilities of 110–139% for samples with 3 wt% H 2 O 2 derived from nitrates, or from acetates heated to 700 °C. This is the first time that HAp-based bioceramics derived from a rapid sol-gel process have been produced with such induced porosity.

Beta-tricalcium phosphate (β-TCP) scaffolds manufactured through the foam replication method are widely employed in bone tissue regeneration. The mechanical strength of these scaffolds is a significant challenge, partly due to the rheological properties of the original suspension. Various strategies have been explored to enhance the mechanical properties. In this research, β-TCP scaffolds containing varying concentrations (0.25–1.00 wt%) of multi-walled carbon nanotubes (MWCNT) were developed. The findings indicate that the addition of MWCNTs led to a concentration-dependent improvement in the viscosity of β-TCP suspensions. All the prepared slurries exhibited viscoelastic behavior, with the storage modulus surpassing the loss modulus. The three time interval tests revealed that MWCNT-incorporated β-TCP suspensions exhibited faster structural recovery compared to pure β-TCP slurries. Introducing MWCNT modified compressive strength, and the optimal improvement was obtained using 0.75 wt% MWCNT. The in vitro degradation of β-TCP was also reduced by incorporating MWCNT. While the inclusion of carbon nanotubes had a marginal negative impact on the viability and attachment of MC3T3-E1 cells, the number of viable cells remained above 70% of the control group. Additionally, the results demonstrated that the scaffold increased the expression level of osteocalcin, osteoponthin, and alkaline phosphatase genes of adiposed-derived stem cells; however, higher levels of gene expersion were obtained by using MWCNT. The suitability of MWCNT-modified β-TCP suspensions for the foam replication method can be assessed by evaluating their rheological behavior, aiding in determining the critical additive concentration necessary for a successful coating process.

Several alternative techniques exist to reconstruct skull defects. The complication rate of the cranioplasty procedure is high and the search for optimal materials and techniques continues. To report long‐term results of patients who have received a cranioplasty using autologous adipose‐derived stem cells (ASCs) seeded on beta‐tricalcium phosphate (betaTCP) granules. Between 10/2008 and 3/2010, five cranioplasties were performed (four females, one male; average age 62.0 years) using ASCs, betaTCP granules and titanium or resorbable meshes. The average defect size was 8.1 × 6.7 cm2. Patients were followed both clinically and radiologically. The initial results were promising, with no serious complications. Nevertheless, in the long‐term follow‐up, three of the five patients were re‐operated due to graft related problems. Two patients showed marked resorption of the graft, which led to revision surgery. One patient developed a late infection (7.3 years post‐operative) that required revision surgery and removal of the graft. One patient had a successfully ossified graft, but was re‐operated due to recurrence of the meningioma 2.2 years post‐operatively. One patient had an uneventful clinical follow‐up, and the cosmetic result is satisfactory, even though skull x‐rays show hypodensity in the borders of the graft. Albeit no serious adverse events occurred, the 6‐year follow‐up results of the five cases are unsatisfactory. The clinical results are not superior to results achieved by conventional cranial repair methods. The use of stem cells in combination with betaTCP granules and supporting meshes in cranial defect reconstruction need to be studied further before continuing with clinical trials. Stem Cells Translational Medicine 2017;6:1576–1582 Reformatted CT image 13 months after reconstruction of the skull with autologous adipose stem cells, beta‐tricalcium phosphate granules and supporting mesh.

Current research in bone tissue engineering is focused not only on basic parameters of the materials, such as biocompatibility and degradation rate but also on intrinsic osteogenic and antimicrobial properties, essential to provide a rapid tissue regeneration without negative effects due to periprosthetic infections, that may result in revision surgeries. One of the major strategies to enhance the osteogenic and antimicrobial performance of calcium phosphates is the ionic substitution, in particular, with magnesium and borates. In this study, we focused on the synthesis of boron-substituted tricalcium phosphate (B-TCP) with a target of 5 mol.% substitution via the solid-state synthesis with mechano-activation. Synthesis from raw precursors, without the preliminary brushite wet precipitation, led to the primary phase of β-TCP, which was proved by the XRD analysis. According to the IR-spectroscopy and 31P NMR analysis, boron substitution occurred in the synthesized sample. The developed material showed a modest antibacterial performance against E. coli, with 13.5 ± 5.0% growth inhibition, and E. faecalis, with 16.7 ± 5.5% inhibition. The biocompatibility of β-TCP and B-TCP was tested through the MTT assay and osteogenic differentiation of the mesenchymal stromal cells. The proposed synthesis approach can be useful for the fabrication of B-TCP ceramics for bone tissue engineering.

The current stem cell tissue engineering always requires in vitro cell culture. To solve this problem, the bone mesenchymal stem cells (MSCs) screen-enrich-combine circulating system (SECCS) was created to rapidly enrich stem cells and combined with β-tricalcium phosphate (β-TCP) to immediately produce bioactive MSCs/β-TCP composites. 37 patients who underwent transforaminal lumbar interbody fusion (TLIF) surgery were included in this study and randomly divided into two groups. One group uses laminal bone grafts (LBG) for intervertebral fusion, and another group uses MSCs/β-TCP composites. The new technique could quickly and selectively enrich stem cells from the bone marrow and simultaneously implant them into the intervertebral space during operation. The cells eluted from the β-tricalcium phosphate were confirmed to be stem cells based on their characteristics. Higher early fusion rates, similar intervertebral height decreases, and functional improvement tendencies were observed in the SECCS group when compared to the LBG group. The bioactive scaffold prepared by SECCS showed better osteogenic efficiency at the early stage of intervertebral fusion compared to autologous LBG, which provided a new bone scaffold substitute for autologous bone.

The authors especially acknowledge financial support from Coordenaç˜ao de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES)—Finance Code 001 and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)—PVE/Project 407035/2013-3. This work was also financially sup ported by Portuguese FCT (PD/BD/135247/2017, SFRH/BPD/93697/2013, SFRH/BPD/100760/2014), PhD programme in Advanced Therapies for Health (PATH) (PD/00169/2013), FCT R&D&I projects with references PTDC/BII-BIO/31570/2017, PTDC/CTM-CTM//29813/2017, PTDC/BII-BIO/28870/2017 and R&D&I Structured Projects with reference NORTE-01-0145-FEDER-000021.

Allogeneic bone grafts are used to treat bone defects in orthopedic surgery, but the osteogenic potential of artificial bones remains a challenge. In this study, we developed a β-tricalcium phosphate (β-TCP) formulation containing MgO, ZnO, SrO, and SiO 2 and compared its bone-forming ability with that of β-TCP without biological elements. We prepared β-TCP discs with 60% porosity containing 1.0 wt% of these biological elements. β-TCP scaffolds were loaded with bone marrow-derived mesenchymal stem cells (BMSC) from 7-week-old male rats and cultured for 2 weeks. ALP activity and mRNA expression of osteogenic markers were evaluated. In addition, scaffolds were implanted subcutaneously in rats and analyzed after 7 weeks. In vitro, the MgO group showed lower Ca concentrations and higher osteogenic marker expression compared to controls. In vivo, the MgO group showed higher ALP activity compared to controls, and RT-qPCR analysis showed significant expression of BMP2 and VEGF . Histopathology, fluorescent immunostaining, and micro-CT also showed relatively better bone formation in the MgO group. β-TCP with MgO may enhance bone morphology in vitro and in vivo and improve the prognosis of patients with substantial and refractory bone defects.