Structure of biomimetic casein micelles: Critical tests of the hydrophobic colloid and multivalent-binding models using recombinant deuterated and phosphorylated β-casein

Milk contains high concentrations of amyloidogenic casein proteins and is supersaturated with respect to crystalline calcium phosphates such as apatite. Nevertheless, the mammary gland normally remains unmineralized and free of amyloid. Unlike κ-casein, β- and αS-caseins are highly effective mineral chaperones that prevent ectopic and pathological calcification of the mammary gland. Milk invariably contains a mixture of two to five different caseins that act on each other as molecular chaperones. Instead of forming amyloid fibrils, several thousand caseins and hundreds of nanoclusters of amorphous calcium phosphate combine to form fuzzy complexes called casein micelles. To understand the biological functions of the casein micelle its structure needs to be understood better than at present. The location in micelles of the highly amyloidogenic κ-casein is disputed. In traditional hydrophobic colloid models, it, alone, forms a stabilizing surface coat that also determines the average size of the micelles. In the recent multivalent-binding model, κ-casein is present throughout the micelle, in intimate contact with the other caseins. To discriminate between these models, a range of biomimetic micelles was prepared using a fixed concentration of the mineral chaperone β-casein and nanoclusters of calcium phosphate, with variable concentrations of κ-casein. A biomimetic micelle was also prepared using a highly deuterated and in vivo phosphorylated recombinant β-casein with calcium phosphate and unlabelled κ-casein. Neutron and X-ray scattering experiments revealed that κ-casein is distributed throughout the micelle, in quantitative agreement with the multivalent-binding model but contrary to the hydrophobic colloid models.

Utilizing waste eggshells as a calcium precursor for contact precipitation of phosphorus from digested sludge centrate

Phosphorus (P) recovery from wastewater is an essential component of the global P cycle. A contact precipitation process using chicken eggshells as a calcium (Ca) precursor was used to recover P from synthetic wastewater and real digested sludge centrate. Up to 96.4 % of P could be recovered from the digested sludge centrate after three repeated cycles of the contact precipitation process. In addition, 36.1 % of total chemical oxygen demand and 37.6 % of total ammonia nitrogen were removed from the centrate. Finally, most of the precipitates could be collected by a simple washing step. Scanning electron microscopy-energy dispersive spectroscopy and x-ray diffraction results indicated that the eggshells played three roles in this process: Ca source, precipitation substrate, and filter medium. Precipitates were mainly brushite. This research provides a new perspective on P recovery from wastewater using waste eggshells, and if further optimized, has a potential for practical future applications.

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.

Hierarchical porous PLLA/ACP fibrous membrane towards bone tissue scaffold

Electrospun fibres have emerged as vital components in developing tissue engineering scaffolds. Calcium phosphate-based materials, renowned for their bioactivity and biocompatibility, have garnered considerable attention in biomedical applications. This study focuses on the incorporation of amorphous calcium phosphate (ACP) nanoparticles into poly(L-lactic acid) (PLLA) to produce electrospun PLLA/ACP fibrous membranes. Subsequent treatment with acetone yielded a hierarchical porous structure, boasting an ultra-high surface area of 94.7753 ± 0.3884 m2/g. The ACP nanoparticles, initially encapsulated by PLLA, were exposed on the fibre surface after acetone treatment. Furthermore, the porous PLLA/ACP fibrous membrane exhibited superior mechanical properties (Young's modulus = 0.148 GPa, tensile strength = 3.05 MPa) and enhanced wettability. In a 7-day in vitro cell culture with human osteoblast-like cells, the porous PLLA/ACP fibrous membrane demonstrated a significant improvement in osteoblast adhesion and proliferation, with a proliferation rate increase of 252.0% and 298.7% at day 4 and day 7, respectively. These findings underscore the potential of the porous PLLA/ACP fibrous membrane as a promising candidate for bone tissue scaffolds.

Dual energy computed tomography cannot effectively differentiate between calcium pyrophosphate and basic calcium phosphate diseases in the clinical setting

Background

Recent reports suggested that dual-energy CT (DECT) may help discriminate between different types of calcium phosphate crystals in vivo, which would have important implications for the characterization of crystal deposition occurring in osteoarthritis.

Purpose

Our aim was to test the hypothesis that DECT can effectively differentiate basic calcium phosphate (BCP) from calcium pyrophosphate (CPP) deposition diseases.

Methods

Discarded tissue after total knee replacement specimens in a 71 year-old patient with knee osteoarthritis and chondrocalcinosis was scanned using DECT at standard clinical parameters. Specimens were then examined on light microscopy which revealed CPP deposition in 4 specimens (medial femoral condyle, lateral tibial plateau and both menisci) without BCP deposition. Regions of interest were placed on post-processed CT images using Rho/Z maps (Syngo.via, Siemens Healthineers, VB10B) in different areas of CPP deposition, trabecular bone BCP (T-BCP) and subchondral bone plate BCP (C-BCP).

Results

Dual Energy Index (DEI) of CPP was 0.12 (SD ​= ​0.02) for reader 1 and 0.09 (SD ​= ​0.03) for reader 2, The effective atomic number (Zeff) of CPP was 10.83 (SD ​= ​0.44) for reader 1 and 10.11 (SD ​= ​0.66) for reader 2. Nearly all DECT parameters of CPP were higher than those of T-BCP, lower than those of C-BCP, and largely overlapping with Aggregate-BCP (aggregate of T-BCP and C-BCP).

Conclusion

Differentiation of different types of calcium crystals using DECT is not feasible in a clinical setting.

Amorphous 1-D nanowires of calcium phosphate/pyrophosphate: A demonstration of oriented self-growth of amorphous minerals

Amorphous inorganic solids are traditionally isotropic, thus, it is believed that they only grow in a non-preferential way without the assistance of regulators, leading to the morphologies of nanospheres or irregular aggregates of nanoparticles. However, in the presence of (ortho)phosphate (Pi) and pyrophosphate ions (PPi) which have synergistic roles in biomineralization, the highly elongated amorphous nanowires (denoted ACPPNs) form in a regulator-free aqueous solution (without templates, additives, organics, etc). Based on thorough characterization and tracking of the formation process (e.g., Cryo-TEM, spherical aberration correction high resolution TEM, solid state NMR, high energy resolution monochromated STEM-EELS), the microstructure and its preferential growth behavior are elucidated. In ACPPNs, amorphous calcium orthophosphate and amorphous calcium pyrophosphate are distributed at separated but close sites. The ACPPNs grow via either the preferential attachment of ∼2 nm nanoclusters in a 1-dimension way, or the transformation of bigger nanoparticles, indicating an inherent driving force-governed process. We propose that the anisotropy of ACPPNs microstructure, which is corroborated experimentally, causes their oriented growth. This study proves that, unlike the conventional view, amorphous minerals can form via oriented growth without external regulation, demonstrating a novel insight into the structures and growth behaviors of amorphous minerals.

A nano-bioconjugate modified with anti-SIRPα antibodies and antisense oligonucleotides of mTOR for anti-atherosclerosis therapy

Atherosclerosis is the main cause of a series of fatal cardiovascular diseases, characterized by pathological accumulation of apoptotic cells and lipids. Pro-phagocytic antibody-based or pro-autophagy gene-based therapies are currently being explored to stimulate the phagocytic clearance of apoptotic cells and lipid metabolism; however, monotherapies are only moderately effective or require high doses with unacceptable side effects. Herein, we engineered a specific nano-bioconjugate loaded with antisense oligonucleotides (ASOs) of mammalian target of rapamycin (mTOR) and modified with anti-signal-regulated protein-α antibody (aSIRPα) for macrophage-mediated atherosclerosis therapy. The specific nano-bioconjugate utilized acid-responsive calcium phosphate (CaP) as a carrier to load mTOR ASOs, coated with lipid on the surface of CaP nanoparticles (ASOs@CaP), and subsequently modified with aSIRPα. The resulting nano-bioconjugates could accumulate within atherosclerotic plaques, target to macrophages and reactivate lesional phagocytosis through blocking the CD47-SIRPα signaling axis. In addition, efficient delivery of mTOR ASOs inhibited mTOR expression, which significantly restored impaired autophagy. The combined action of mTOR ASOs and aSIRPα reduced apoptotic cells and lipids accumulation. This nanotherapy significantly reduced plaque burden and inhibited progression of atherosclerotic lesions. These results show the potential of specific nano-bioconjugates for the prevention of atherosclerotic cardiovascular disease. STATEMENT OF SIGNIFICANCE: Atherosclerosis is the main cause of a series of fatal cardiovascular diseases. Pro-phagocytic antibody-based or pro-autophagy gene-based therapies are currently being explored to stimulate the phagocytic clearance of apoptotic cells and lipid metabolism; however, monotherapies are only moderately effective or require high doses with unacceptable side effects. Herein, we engineered a specific nano-bioconjugate loaded with antisense oligonucleotides (ASOs) of mammalian target of rapamycin (mTOR) and modified with anti-signal-regulated protein-α antibody (aSIRPα) for macrophage-mediated atherosclerosis therapy. Our study demonstrated that the combined action of mTOR ASOs and aSIRPα reduced apoptotic cells and lipids accumulation. This nanotherapy significantly reduced plaque burden and inhibited progression of atherosclerotic lesions. These results show the potential of specific nano-bioconjugates for the prevention of atherosclerotic cardiovascular disease.

Construction of a PEGDA/chitosan hydrogel incorporating mineralized copper-doped mesoporous silica nanospheres for accelerated bone regeneration

Hydrogels, integrating diverse biocompatible materials, have emerged as promising candidates for bone repair applications. This study presents a double network hydrogel designed for bone tissue engineering, combining poly(ethylene glycol) diacrylate (PEGDA) and chitosan (CS) crosslinked through UV polymerization and ionic crosslinking. Concurrently, copper-doped mesoporous silica nanospheres (Cu-MSNs) were synthesized using a one-pot method. Cu-MSNs underwent additional modification through in-situ biomineralization, resulting in the formation of an apatite layer. Polydopamine was employed to facilitate the deposition of Calcium (Ca) and Phosphate (P) ions on the surface of Cu-MSNs (Cu-MSNs/PDA@CaP). Composite hydrogels were created by integrating varied concentrations of Cu-MSNs/PDA@CaP (25, 50, 100, 150, 200 μg/mL). Characterization unveiled distinctive interconnected porous structures within the composite hydrogel, showcasing a notable 169.6 % enhancement in compressive stress (elevating from 89.01 to 240.19 kPa) compared to pure PEGDA. In vitro biocompatibility experiments illustrated that the composite hydrogel maintained elevated cell viability (up to 106.6 %) and facilitated rapid cell proliferation over 7 days. The hydrogel demonstrated a substantial 57.58 % rise in ALP expression and a surprising 235.27 % increase in ARS staining. Moreover, it significantly enhanced the expression of crucial osteogenic genes, such as run-related transcription factors 2 (RUNX2), collagen 1a1 (Col1a1), and secreted phosphoprotein 1 (Spp1), establishing it as a promising scaffold for bone regeneration. This study shows how Cu-MSNs/PDA@CaP were successfully integrated into a double network hydrogel, resulting in a composite material with good biological responses. Due to its improved characteristics, this composite hydrogel holds the potential for advancing bone regeneration procedures.

Octacalcium phosphate phase forming cements as an injectable bone substitute materials: Preparation and in vitro structural study

In the realm of regenerating damaged or degenerated bones through minimally invasive techniques, injectable materials have emerged as exceptionally promising. Among these, calcium phosphate bone cements (CPCs) have garnered significant interest due to their remarkable bioactivity, setting it apart from non-degradable alternatives such as polymethyl methacrylate cements. α-Tricalcium phosphate (α-TCP) is a widely used solid phase component in CPCs. It can transform into calcium-deficient hydroxyapatite (CDHAp) when it comes in contact with water. In this study, we aimed to create an injectable, self-setting bone cement using low-temperature synthesized α-TCP powder as a single precursor of the powder phase. We found that changes in the pH of the liquid phase (pH 6.0, pH 6.2, pH 7.0 and pH 7.4) significantly altered the cement's setting, handling, and mechanical properties. The formation of the octacalcium phosphate (OCP) phase was identified in our study, which positively affects the osteoblastic cell response. Hardened OCP-forming bone cements prepared using a liquid phase with pH 7.0 and 7.4 showed better osteogenic cell attachment and proliferation than those prepared with pH 6.0 and 6.2. Our study suggests that changes in the pH of the liquid phase can significantly affect the properties of α-TCP-based bone cement, and the presence of the OCP phase is crucial for optimal cement performance.

Calcium phosphate coating enhances osteointegration of melt electrowritten scaffold by regulating macrophage polarization

The osteoimmune microenvironment induced by implants plays a significant role in bone regeneration. It is essential to efficiently and timely switch the macrophage phenotype from M1 to M2 for optimal bone healing. This study examined the impact of a calcium phosphate (CaP) coating on the physiochemical properties of highly ordered polycaprolactone (PCL) scaffolds fabricated using melt electrowritten (MEW). Additionally, it investigated the influence of these scaffolds on macrophage polarization and their immunomodulation on osteogenesis. The results revealed that the CaP coated PCL scaffold exhibited a rougher surface topography and higher hydrophilicity in comparison to the PCL scaffold without coating. Besides, the surface morphology of the coating and the release of Ca2+ from the CaP coating were crucial in regulating the transition of macrophages from M1 to M2 phenotypes. They might activate the PI3K/AKT and cAMP-PKA pathways, respectively, to facilitate M2 polarization. In addition, the osteoimmune microenvironment induced by CaP coated PCL could not only enhance the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) in vitro but also promote the bone regeneration in vivo. Taken together, the CaP coating can be employed to control the phenotypic switching of macrophages, thereby creating a beneficial immunomodulatory microenvironment that promotes bone regeneration.

Guided bone regeneration of calcium phosphate-coated and strontium ranelate-doped titanium mesh in a rat calvarial defect model

PURPOSE

When applied alone, titanium (Ti) mesh may not effectively block the penetration of soft tissues, resulting in insufficient new bone formation. This study aimed to confer bioactivity and improve bone regeneration by doping calcium phosphate (CaP) precipitation and strontium (Sr) ranelate onto a TiO2 nanotube (TNT) layer on the surface of a Ti mesh.

METHODS

The TNT layer was obtained by anodizing on the Ti mesh, and CaP was formed by cyclic pre-calcification. The final specimens were produced by doping with Sr ranelate. The surface properties of the modified Ti mesh were investigated using high-resolution field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. To evaluate the effects of surface treatment on cell viability, osteoblasts were cultured for 1-3 days, and their absorbance was subsequently measured. In an in vivo experiment, critical-size defects were created in rat calvaria (Ф=8 mm). After 5 weeks, the rats were sacrificed (n=4 per group) and bone blocks were taken for micro-computed tomography and histological analysis.

RESULTS

After immersing the Sr ranelate-doped Ti mesh in simulated body fluid, the protrusions observed in the initial stage of hydroxyapatite were precipitated as a dense structure. On day 3 of osteoblast culture, cell viability was significantly higher on the pre-calcified Sr ranelate-doped Ti mesh surface than on the untreated Ti mesh surface (P<0.05). In the in vivo experiment, a bony bridge formed between the surrounding basal bone and the new bone under the Sr ranelate-doped Ti mesh implanted in a rat calvarial defect, closing the defect. New bone mineral density (0.91±0.003 g/mm3) and bone volume (29.35±2.082 mm3) significantly increased compared to the other groups (P<0.05).

CONCLUSIONS

Cyclic pre-calcification of a Ti mesh with a uniform TNT layer increased bioactivity, and subsequent doping with Sr ranelate effectively improved bone regeneration in bone defects.

Material extrusion additive manufacturing of poly(lactic acid)/Ti6Al4V@calcium phosphate core-shell nanocomposite scaffolds for bone tissue applications

The use of porous scaffolds with appropriate mechanical and biological features for the host tissue is one of the challenges in repairing critical-size bone defects. With today's three-dimensional (3D) printing technology, scaffolds can be customized and personalized, thereby eliminating the problems associated with conventional methods. In this work, after preparing Ti6Al4V/Calcium phosphate (Ti64@CaP) core-shell nanocomposite via a solution-based process, by taking advantage of fused deposition modeling (FDM), porous poly(lactic acid) (PLA)-Ti64@CaP nanocomposite scaffolds were fabricated. Scanning electron microscope (SEM) showed that nanostructured calcium phosphate was distributed uniformly on the surface of Ti64 particles. Also, X-ray diffraction (XRD) indicated that calcium phosphate forms an octacalcium phosphate (OCP) phase. As a result of incorporating 6 wt% Ti64@CaP into the PLA, the compressive modulus and ultimate compressive strength values increased from 1.4 GPa and 29.5 MPa to 2.0 GPa and 53.5 MPa, respectively. Furthermore, the differential scanning calorimetry results revealed an increase in the glass transition temperature of PLA, rising from 57.0 to 62.4 °C, due to the addition of 6 wt% Ti64@CaP. However, it is worth noting that there was a moderate decrease in the crystallization and melting temperatures of the nanocomposite filament, which dropped from 97.0 to 89.5 °C and 167 to 162.9 °C, respectively. The scaffolds were seeded with human adipose tissue-derived mesenchymal stem cells (hADSCs) to investigate their biocompatibility and cell proliferation. Calcium deposition, ALP activity, and bone-related proteins and genes were also used to evaluate the bone differentiation potential of hADSCs. The obtained results showed that introducing Ti64@CaP considerably improved in vitro biocompatibility, facilitating the attachment, differentiation, and proliferation of hADSCs. Considering the findings of this study, the 3D-printed nanocomposite scaffold could be considered a promising candidate for bone tissue engineering applications.

Folate-modified carboxymethyl chitosan-based drug delivery system for breast cancer specific combination therapy via regulating mitochondrial calcium concentration

Although various drug delivery systems that regulated Ca2+ concentration has been developed for tumor therapy, their application still presented significant challenges due to the complex preparation and introduction of a large number of inorganic molecules that might cause serious toxic effects. To solve these problems, a folate-functionalized carboxymethyl chitosan (CMCS)/calcium phosphate hybrid nanoparticle (CF/CaP) with Ca2+ production was designed to treat breast cancer combined with the Ca2+ inhibitory effect of encapsulated curcumin (Cur). It was demonstrated that the optimal CF/CaP nanoparticles loaded with Cur (C@CF/CaP) were spherical nanoparticles, which exhibited a smaller size at about 179 nm than non-targeted nanoparticles with size at about 234 nm. C@CF/CaP had good biocompatibility, high stability and acid responsive drug release. Compared with the neutral environment, the cumulative release of Cur was >70 % after culture for 36 h at pH 5.0. Compared with non-targeted nanoparticles, C@CF/CaP could specifically target tumor tissues and then enter tumor cells through folate receptor-mediated endocytosis. C@CF/CaP could cause mitochondrial Ca2+ overload, trigger the mitochondrial apoptotic pathway, destroy the mitochondrial structure and finally have good anti-tumor efficiency. The results proved that Ca2+ nanomodulators based on CMCS might provide a potential organelle targeting strategy for cancer therapy.

NOVEL HIGH-STRENGTH POLYESTER COMPOSITE SCAFFOLDS FOR BONE REGENERATION

Repair of critical sized bone defects, particularly in load-bearing areas, is a major clinical problem that requires surgical intervention and implantation of biological or engineered grafts. For load-bearing sites, it is essential to use engineered grafts that have both sufficient mechanical strength and appropriate pore properties to support bone repair and tissue regeneration. Unfortunately, the mechanical properties of such grafts are often compromised due to the creation of pores required to facilitate tissue ingrowth following implantation. To overcome the limitations associated with porous scaffolds and their reduced mechanical strength, we have developed a methodology for creating a solid structure that retains its bulk mechanical properties while also evolving into a porous structure in a biological environment through degradation and erosion. In this study, we utilized polyesters that have been approved by the FDA, including poly (lactic acid) (PLA), poly(glycolic acid) (PGA), their copolymer PLGA (PLGA, with a ratio of 85:15 and 50:50 of PLA:PGA), and poly(caprolactone) (PCL). These polymers and their ceramic composites with tricalcium phosphate (TCP) were compression molded into solid forms, which exhibited mechanical properties with compressive modulus as high as 2745 ± 364 MPa within the range of human trabecular bone and in the lower range of human cortical bone. The use of fast-degrading PLGA (50:50) and PGA as porogens allowed the formation of pores within the solid structures due to their degradation, and the TCP acts as a buffering agent to neutralize their acidic degradation byproducts. These scaffolds facilitated the growth of new blood vessels and tissue ingrowth in a subcutaneous implantation model. In addition, in a rat critical-sized mandibular bone defects these scaffolds supported bone growth with 70% of new bone volume fraction. Furthermore, the extent of bone regeneration was found to be higher for the scaffolds with bone morphogenic proteins (BMP2), indicating their suitability for bone repair and regeneration.

Advances and challenges in regenerative dentistry: A systematic review of calcium phosphate and silicate-based materials on human dental pulp stem cells

Conventional dentistry faces limitations in preserving tooth health due to the finite lifespan of restorative materials. Regenerative dentistry, utilizing stem cells and bioactive materials, offers a promising approach for regenerating dental tissues. Human dental pulp stem cells (hDPSCs) and bioactive materials like calcium phosphate (CaP) and silicate-based materials have shown potential for dental tissue regeneration. This systematic review aims to investigate the effects of CaP and silicate-based materials on hDPSCs through in vitro studies published since 2015. Following the PRISMA guidelines, a comprehensive search strategy was implemented in PubMed MedLine, Cochrane, and ScienceDirect databases. Eligibility criteria were established using the PICOS scheme. Data extraction and risk of bias (RoB) assessment were conducted, with the included studies assessed for bias using the Office of Health and Translation (OHAT) RoB tool. The research has been registered at OSF Registries. Ten in vitro studies met the eligibility criteria out of 1088 initial studies. Methodological heterogeneity and the use of self-synthesized biomaterials with limited generalizability were observed in the included study. The findings highlight the positive effect of CaP and silicate-based materials on hDPSCs viability, adhesion, migration, proliferation, and differentiation. While the overall RoB assessment indicated satisfactory credibility of the reviewed studies, the limited number of studies and methodological heterogeneity pose challenges for quantitative research. In conclusion, this systematic review provides valuable insights into the effects of CaP and silicate-based materials on hDPSCs. Further research is awaited to enhance our understanding and optimize regenerative dental treatments using bioactive materials and hDPSCs, which promise to improve patient outcomes.

The mechanism of biomineralization: Progress in mineralization from intracellular generation to extracellular deposition

Biomineralization is a highly regulated process that results in the deposition of minerals in a precise manner, ultimately producing skeletal and dental hard tissues. Recent studies have highlighted the crucial role played by intracellular processes in initiating biomineralization. These processes involve various organelles, such as the endoplasmic reticulum(ER), mitochondria, and lysosomes, in the formation, accumulation, maturation, and secretion of calcium phosphate (CaP) particles. Particularly, the recent in-depth study of the dynamic process of the formation of amorphous calcium phosphate(ACP) precursors among organelles has made great progress in the development of the integrity of the biomineralization chain. However, the precise mechanisms underlying these intracellular processes remain unclear, and they cannot be fully integrated with the extracellular mineralization mechanism and the physicochemical structure development of the mineralization particles. In this review, we aim to focus on the recent progress made in understanding intracellular mineralization organelles' processes and their relationship with the physicochemical structure development of CaP and extracellular deposition of CaP particles.

Assessment of physical/mechanical properties and cytotoxicity of dual-cured resin cements containing Sr-bioactive glass nanoparticles and calcium phosphate

The aim was to develop dual-cured resin cements containing Sr-bioactive glass nanoparticles (Sr-BGNPs; 5 or 10 wt%) and monocalcium phosphate monohydrate (MCPM; 3 or 6 wt%). Effects of additives on degree of monomer conversion (DC), biaxial flexural strength/modulus, shear bond strength (SBS), mass/volume change, color stability, ion release, and cytotoxicity were examined. Controls included material without reactive fillers and Panavia SA Plus (PV). Experimental cements showed higher DC than PV regardless of light activation (p<0.05). Mean SBS and color stability were comparable between experimental cements and PV. Cell viability upon the exposure to sample extracts of experimental cements was 80%-92%. High additive concentrations led to lower strength and modulus than PV (p<0.05). The additives increased mass change, reduced color stability, and promoted ion release. The experimental resin cements demonstrated acceptable mechanical/chemical properties and cytotoxicity. The additives reduced the strength but provided ion release, a desirable action to prevent recurrent caries.

Adsorption-electrochemical mediated precipitation for phosphorus recovery from sludge filter wastewater with a lanthanum-modified cellulose sponge filter

In this study, the sludge filter wastewater is confirmed to investigate the effects of adsorption-electrochemical mediated precipitation (EMP) driven phosphorus recovery on the basis of lanthanum-modified cellulose sponge filter (LCLM) material. The adsorption-EMP method relies on in situ recovery phosphate (P) from the used desorption agent (NaOH-NaCl binary solution) via the formation of Ca5(PO4)3OH all while preserving the alkalinity of the desorption agents which benefited long-term application. The lanthanum content of LCLM was 9.0 mg/g, and the adsorption capacity reached 226.1 ± 15.2 mg P/g La at an equilibrium concentration of 3.9 mg P/L. After adsorption, 55.7 % of P was recovered, and the corresponding alkalinity increased from 1.9 mmol/L to 2.2 mmol/L. Adsorption mechanism analysis revealed that the high lanthanum usage of LCLM was attributed to the synergistic effect of the lattice oxygen of LaO and LaPO4·0.5H2O crystallite formation. Additionally, the Ca5(PO4)3OH was found precipitated in the precipitation in the cathode chamber (P-CC) rather than on the surface/section of cation exchange membrane (CEM) and cathode indicating that the P recovery process was controlled by the saturation of CaP species in the EMP system and the electromigration effect. These findings present a new strategy to promote the effective utilization of rare earth elements for P adsorption and demonstrate the potential application of adsorption-EMP systems in dephosphorization for wastewater treatment.

Garlic extract enhances bioceramic bone scaffolds through upregulating ALP & BGLAP expression in hMSC-monocyte co-culture

Bone homeostasis is predicated by osteoblast and osteoclast cell cycles where gene expressions are responsible for their differentiation from human mesenchymal stem cells (hMSC) and monocytes, respectively. The pro-osteogenic potential of an hMSC-monocyte co-culture can be measured through complementary DNA (mRNA synthesis) within the nucleus, known as quantitative polymerase chain reaction (qPCR). Through this technique, the effects of garlic extract (allicin) release from calcium phosphate bone scaffolds on gene expression of bone forming and bone remodeling cells was explored. Results show this complex biomaterial system enhances hMSC differentiation through the upregulation of bone-forming proteins. Osteoblastic gene markers alkaline phosphatase (ALP) and osteocalcin (BGLAP), are respectively upregulated by 3-fold and 1.6-fold by day 14. These mature osteoblasts then upregulate the receptor activator of nuclear factor-kB ligand (RANKL) which recruits osteoclast cells, as captured by a nearly 2-fold higher osteoclast expression of tartrate-resistance acid-phosphatase (ACP5). This also activates antagonist osteoprotegerin (OPG) expression in osteoblasts, decreasing osteoclast resorption potential and ACP5 expression by day 21. The pro-osteogenic environment with garlic extract release is further quantified by a 4× increase in phosphatase activity and visibly captured in immunofluorescent tagged confocal images. Also corroborated by enhanced collagen formation in a preliminary in vivo rat distal femur model, this work collectively reveals how garlic extract can enhance bioceramic scaffolds for bone tissue regenerative applications.

Bioinspired mineralization of engineered living materials to promote osteogenic differentiation

In this work, Engineered Living Materials (ELMs), based on the combination of genetically-modified bacteria and mineral-reinforced organic matrices, and endowed with self-healing or regenerative properties and adaptation to specific biological environments were developed. Concretely, we produced ELMs combining human mesenchymal stem cells (hMSCs) and Lactococcus lactis (L. lactis), which was specifically programmed to deliver bone morphogenetic protein (BMP-2) upon external stimulation using nisin, into mineralized alginate matrices. The hybrid organic/inorganic matrix was built through a protocol, inspired by bone mineralization, in which alginate (Alg) assembly and apatite (HA) mineralization occurred simultaneously driven by calcium ions. Chemical composition, structure and reologhical properties of the hybrid 3D matrices were dedicately optimized prior the incorportation of the living entities. Then, the same protocol was reproduced in the presence of hMSC and engineered L. lactis that secrete BMP-2 resulting in 3D hybrid living hydrogels. hMSC viability and osteogenic differentiation in the absence and presence of the bacteria were evaluated by live/dead and quantitative real-time polymerase chain reaction (qPCR) and immunofluorescence assays, respectively. Results demonstrate that these 3D engineered living material support osteogenic differentiation of hMSCs due to the synergistic effect between HA and the growth factors BMP-2 delivered by L. lactis.

Flow-through electrochemical organophosphorus degradation and phosphorus recovery: The essential role of chlorine radical

Phosphorus scarcity and the deleterious ecological impact of the release of organophosphorus pesticides have emerged as critical global issues. Previous research has shown the ability of electrochemistry to induce the precipitation of calcium phosphate from phosphorus-laden wastewater to recover the phosphorus. The current study presents a flow-through electrochemical system consisting of a column-shaped electrochemical reactor, a tubular stainless-steel (SS) cathode, and a titanium suboxides (TiSO) anode. This system simultaneously oxidizes tetrakis (hydroxymethyl) phosphonium sulfate (THPS) and recycles phosphates. The influence of current density, flow rate, and initial calcium ions concentration were examined under continuous flow operation. To enhance the electrochemical reactor's performance, we elevated the current density from 5 to 30 mA cm-2, which caused the phosphorus recovery efficiency to increase from 37% to 72% within 120 min, accompanied by an enhancement of the THPS mineralization efficiency from 57% to 90%. These improvements were likely due to the higher yield of reactive species chloride species (Cl•) formed at the TiSO anode and the higher local pH at the cathode. By investigating the formation of Cl• at the TiSO anode, we found that THPS mineralization exceeded 75% in the presence of NaCl at a current density of 20 mA cm-2. The demonstrated performance of the flow-through electrochemical system should enable the utilization of anodic oxidation-cathodic precipitation for the recovery of phosphorus from organophosphorus-contaminated wastewater.

Multiscale multimodal characterization and simulation of structural alterations in failed bioprosthetic heart valves

Calcific degeneration is the most frequent type of heart valve failure, with rising incidence due to the ageing population. The gold standard treatment to date is valve replacement. Unfortunately, calcification oftentimes re-occurs in bioprosthetic substitutes, with the governing processes remaining poorly understood. Here, we present a multiscale, multimodal analysis of disturbances and extensive mineralisation of the collagen network in failed bioprosthetic bovine pericardium valve explants with full histoanatomical context. In addition to highly abundant mineralized collagen fibres and fibrils, calcified micron-sized particles previously discovered in native valves were also prevalent on the aortic as well as the ventricular surface of bioprosthetic valves. The two mineral types (fibres and particles) were detectable even in early-stage mineralisation, prior to any macroscopic calcification. Based on multiscale multimodal characterisation and high-fidelity simulations, we demonstrate that mineral occurrence coincides with regions exposed to high haemodynamic and biomechanical indicators. These insights obtained by multiscale analysis of failed bioprosthetic valves serve as groundwork for the evidence-based development of more durable alternatives. STATEMENT OF SIGNIFICANCE: Bioprosthetic valve calcification is a well-known clinically significant phenomenon, leading to valve failure. The nanoanalytical characterisation of bioprosthetic valves gives insights into the highly abundant, extensive calcification and disorganization of the collagen network and the presence of calcium phosphate particles previously reported in native cardiovascular tissues. While the collagen matrix mineralisation can be primarily attributed to a combination of chemical and mechanical alterations, the calcified particles are likely of host cellular origin. This work presents a straightforward route to mineral identification and characterization at high resolution and sensitivity, and with full histoanatomical context and correlation to hemodynamic and biomechanical indicators, hence providing design cues for improved bioprosthetic valve alternatives.

Multifunctional polydopamine - Zn2+-curcumin coated additively manufactured ceramic bone grafts with enhanced biological properties

The lack of site-specific chemotherapeutic agents after osteosarcoma surgeries often induces severe side effects. We propose the utilization of curcumin as an alternative natural chemo-preventive drug for tumor-specific delivery systems with 3D printed tricalcium phosphate (TCP) based artificial bone grafts. The poor bioavailability and hydrophobic nature of curcumin restrict its clinical use. We have used polydopamine (PDA) coating with Zn2+ functionalization to enhance the curcumin release in the biological medium. The obtained PDA-Zn2+ complex is characterized by X-ray photoelectron spectroscopy (XPS). The presence of PDA-Zn2+ coating leads to ~2 times enhancement in curcumin release. We have computationally predicted and validated the optimized surface composition by a novel multi-objective optimization method. The experimental validation of the predicted compositions indicates that the PDA-Zn2+ coated curcumin immobilized delivery system leads to a ~12 folds decrease in osteosarcoma viability on day 11 as compared to only TCP. The osteoblast viability shows ~1.4 folds enhancement. The designed surface shows the highest ~90 % antibacterial efficacy against gram-positive and gram-negative bacteria. This unique strategy of curcumin delivery with PDA-Zn2+ coating is expected to find application in low-load bearing critical-sized tumor-resection sites.

Fabrication of water-dispersible and cell-stimulating calcium phosphate nanoparticles immobilizing basic fibroblast growth factor

Basic fibroblast growth factor (bFGF) is a therapeutic protein that can enhance angiogenesis, wound healing, and tissue regeneration; however, it is extremely unstable even under a normal physiological environment. Biocompatible calcium phosphate (CaP) nanoparticles (NPs) co-immobilizing bFGF, heparin, and ferucarbotran would be useful as a multifunctional delivery carrier of bFGF. In this study, such NPs were successfully fabricated by a coprecipitation process, using a labile supersaturated CaP solution containing bFGF, heparin, and ferucarbotran. The NPs showed relatively high negative zeta potential (-12 mV) because of the negatively charged heparin, which enabled their stable dispersion in water. The hydrodynamic diameter of the NPs was around 200 nm. Immunoreactive bFGF was released from the NPs in an acellular medium dose-dependently. The NPs promoted proliferation of baby hamster kidney fibroblasts (BHK-21 cells) and mouse osteoblastic MC3T3-E1 cells at a certain dose range, although they inhibited proliferation of rat pheochromocytoma (PC-12) cells. These results demonstrated that the effect of the NPs on cell proliferation was dependent on the cell type and dose, the details of which should be investigated in a future study.

Influence of the sintering atmosphere on the physico-chemical properties and the osteoclastic resorption of β-tricalcium phosphate cylinders

One of the most widely used materials for bone graft substitution is β-Tricalcium phosphate (β-TCP; β-Ca3(PO4)2). β-TCP is typically produced by sintering in air or vacuum. During this process, evaporation of phosphorus (P) species occurs, leading to the formation of a calcium-rich alkaline layer. It was recently shown that the evaporation of P species could be prevented by co-sintering β-TCP with dicalcium phosphate (DCPA; CaHPO4; mineral name: monetite). The aim of this study was to see how a change of sintering atmosphere could affect the physico-chemical and biological properties of β-TCP. For this purpose, three experimental groups were considered: β-TCP cylinders sintered in air and subsequently polished to remove the surface layer (control group); the same polished cylinders after subsequent annealing at 500 °C in air to generate a calcium-rich alkaline layer (annealed group); and finally, β-TCP cylinders sintered in a monetite-rich atmosphere and subsequently polished (monetite group). XPS analysis confirmed that cylinders from the annealed group had a significantly higher Ca/P molar ratio at their surface than that of the control group while this ratio was significantly lower for the cylinders from the monetite group. Sintering β-TCP in the monetite-rich atmosphere significantly reduced the grain size and increased the density. Changes of surface composition affected the activity of osteoclasts seeded onto the surfaces, since annealed β-TCP cylinders were significantly less resorbed than β-TCP cylinders sintered in the monetite-rich atmosphere. This suggests that an increase of the surface Ca/P molar ratio leads to a decrease of osteoclastic resorption. STATEMENT OF SIGNIFICANCE: Minimal changes of surface and bulk (< 1%) composition have major effects on the ability of osteoclasts to resorb β-tricalcium phosphate (β-TCP), one of the most widely used ceramics for bone substitution. The results presented in this study are thus important for the calcium phosphate community because (i) β-TCP may have up to 5% impurities according to ISO and ASTM standards and still be considered to be "pure β-TCP", (ii) β-TCP surface properties are generally not considered during biocompatibility assessment and (iii) a rationale can be proposed to explain the various inconsistencies reported in the literature on the biological properties of β-TCP.

Polysaccharide-bioceramic composites for bone tissue engineering: A review

Limitations associated with conventional bone substitutes such as autografts, increasing demand for bone grafts, and growing elderly population worldwide necessitate development of unique materials as bone graft substitutes. Bone tissue engineering (BTE) would ensure therapy advancement, efficiency, and cost-effective treatment modalities of bone defects. One way of engineering bone tissue scaffolds by mimicking natural bone tissue composed of organic and inorganic phases is to utilize polysaccharide-bioceramic hybrid composites. Polysaccharides are abundant in nature, and present in human body. Biominerals, like hydroxyapatite are present in natural bone and some of them possess osteoconductive and osteoinductive properties. Ion doped bioceramics could substitute protein-based biosignal molecules to achieve osteogenesis, vasculogenesis, angiogenesis, and stress shielding. This review is a systemic summary on properties, advantages, and limitations of polysaccharide-bioceramic/ion doped bioceramic composites along with their recent advancements in BTE.

Sargassum macroalgae from Quintana Roo as raw material for the preparation of high-performance phosphate adsorbent from aqueous solutions

Currently, the large volumes of Sargassum biomass (Sgs) arriving on Caribbean coasts are a problem that must be solved quickly. One alternative is to obtain value-added products from Sgs. In this work, Sgs is demonstrated to be a high-performance Ca - bioadsorbent for phosphate removal by a heat pretreatment at 800 °C that produces biochar. According to XRD analysis, calcined Sgs (CSgs) have a composition of 43.68%, 40.51%, and 8.69% of Ca(OH)2, CaCO3, and CaO, making CSgs a promising material for phosphate removal and recovery. Results demonstrated that CSgs have a high capacity to adsorb P over a wide range of concentrations (25-1000 mg P/L). After P removal, at low P concentration, the adsorbent material is rich in apatite (Ca5(PO4)3OH), and at high P concentration, brushite (CaHPO4•2H2O) was the main P compound. The CSg reached a Qmax of 224.58 mg P/g, which is higher than other high-performance adsorbents reported in the literature. The phosphate adsorption mechanism was dominated by chemisorption, followed by precipitation according to the pseudo-second-order kinetic model. The solubility of P (74.5 wt%) in formic acid solution and the water-soluble P (24.8 wt%) for CSgs after P adsorption indicated that the final product presents the potential to be used as fertilizer for acid soils. This biomass's processability and high phosphate adsorption performance for P removal make CSgs a potential material for wastewater treatment, and subsequent use of these residues as fertilizer offers a circular economy solution to this problem.

Spectroscopic characterization of calcium phosphate precipitated under human eye conditions: An in vitro study

Calcification is a well-known process of calcium phosphate mineralization observed in intraocular lenses. Despite the many works conducted in this field, there is no strict explanation of the mechanisms of this process. In order to better understand the phenomenon, i.e., the mechanisms and structural conditions that promote calcification, any research observations should be conducted under conditions that best reflect those of the human eye. Taking into account the specific anatomy and physicochemical conditions of the human eye, the problem under discussion becomes difficult to solve in vitro. In the present study, calcium phosphates formed under conditions similar to those in the human eye were characterized using SEM/EDS and infrared spectroscopy. Conducted study showed the formation of white spherical precipitates, which are unstable when extracted from solution. Such precipitates were characteristic of solutions containing 1.5-3.0 mM² of solutes. Elemental analysis showed a Ca/P ratio of 1.64-1.65, which is similar to the ratio for hydroxyapatite (1.67). Chemical structure analysis revealed the presence of broad bending and stretching bands at 475-830 cm^-1 and 880-1250 cm^-1, respectively, which are characteristic of PO₄^3- groups in apatite calcium phosphates. In further analysis involving numerical fitting the bands corresponding to apatitic PO₄^3- and indicating the presence of calcium phosphates hydration were found. The results allow the selection of immersion media for further studies involving the incubation of hydrogel intraocular lenses.

Fabrication of 3D printed Ca3Mg3(PO4)4-based bioceramic scaffolds with tailorable high mechanical strength and osteostimulation effect

Calcium, magnesium and phosphate are predominant constituents in the human bone. In this study, magnesium-calcium phosphate composite bioceramic scaffolds were fabricated utilizing Mg3(PO4)2 and β-Ca3(PO4)2 as starting materials, and their pore structure was constructed by 3D printing. The porosity and compressive strength of the composite bioceramic scaffolds could be adjusted by altering the sintering temperature and the formula of starting materials. The composite bioceramic scaffolds prepared from 60 wt% Mg3(PO4)2 and 40 wt% β-Ca3(PO4)2 were dominated by the Ca3Mg3(PO4)4 phase, and this Ca3Mg3(PO4)4-based bioceramic scaffolds possessed the highest compressive strength (12.7 - 92.4 MPa). Moreover, the Ca3Mg3(PO4)4-based bioceramic scaffolds stimulated cellular growth and osteoblastic differentiation of bone marrow stromal cells. The Ca3Mg3(PO4)4-based bioceramic scaffolds as bone regenerative biomaterials are flexible to the requirement of bone defects at various sites.

New Research Progress of Modified Bone Cement Applied to Vertebroplasty

Percutaneous vertebroplasty and percutaneous kyphoplasty are effective methods to treat acute osteoporotic vertebral compression fractures that can quickly provide patients with pain relief, prevent further height loss of the vertebral body, and help correct kyphosis. Many clinical studies have investigated the characteristics of bone cement. Bone cement is a biomaterial injected into the vertebral body that must have good biocompatibility and biosafety. The optimization of the characteristics of bone cement has become of great interest. Bone cement can be mainly divided into 3 types: polymethyl methacrylate, calcium phosphate cement, and calcium sulfate cement. Each type of cement has its own advantages and disadvantages. In the past 10 years, the performance of bone cement has been greatly improved via different methods. The aim of our review is to provide an overview of the current progress in the types of modified bone cement and summarize the key clinical findings.

Preparation, characterisation and applications of bone char, a food waste-derived sustainable material: A review

The production of increasing quantities of by-products is a key challenge for modern society; their valorisation - turning them into valuable compounds with technological applications - is the way forward, in line with circular economy principles. In this review, the conversion of bones (by-products of the agro-food industry) into bone char is described. Bone char is obtained with a process of pyrolysis, which converts the organic carbon into an inorganic graphitic one. Differently from standard biochar of plant origin, however, bone char also contains calcium phosphates, the main component of bone (often hydroxyapatite). The combination of calcium phosphate and graphitic carbon makes bone char a unique material, with different possible uses. Here bone chars' applications in environmental remediation, sustainable agriculture, catalysis and electrochemistry are discussed; several aspects are considered, including the bones used to prepare bone char, the preparation conditions, how these affect the properties of the materials (i.e. porosity, surface area) and its functional properties. The advantages and limitations of bone chars in comparison to traditional biochar are discussed, highlighting the directions the research should take for bone chars' performances to improve. Moreover, an analysis on the sustainability of bone chars' preparation and use is also included.

Management of Subchondral Lesions in the Foot and Ankle

The treatment of subchondral lesions is an area with limited focus within the foot and ankle literature. The literature has shown an association between disruption of the subchondral bone plate and the formation of subchondral cysts. The primary causes of subchondral lesions are acute trauma, repetitive microtrauma, as well as idiopathic means. Evaluation of these injuries should be done carefully and often requires advanced imaging including MRI and computed tomography. Treatment does vary depending on the presentation of the subchondral lesion with or without the presence of an osteochondral lesion.

Phosphorus recovery from wastewater via calcium phosphate precipitation: A critical review of methods, progress, and insights

Phosphorus (P) is one of the important elements for human, animal, and plant life. Due to the development of the circular economy in recent years, the recovery of P from wastewater has received more attention. Recovery of P from domestic, industrial, and agricultural wastewater in the form of calcium phosphate (CaP) by precipitation/crystallization process presents a low-cost and effective method. Recovered CaP could be used as P fertilizer and for other industrial applications. This review summarizes the effects of supersaturation, pH, seed materials, calcium (Ca) source, and wastewater composition, on the precipitation/crystallization process. The recovery efficiency and value proposition of recovered CaP were assessed. This in-depth analysis of the literature reports identified the process parameters that are worth further optimization. The review also provides perspectives on future research needs on expanding the application field of recovered CaP and finding other more economical and environmentally friendly Ca sources.

Synergistic effect of drug/antibiotic-impregnated micro/nanohybrid mesoporous bioactive glass/calcium phosphate composite bone cement on antibacterial and osteoconductive activities

Calcium phosphate bone cements (CPC) can be used in minimally invasive surgery because of their injectability, and they can also be used to repair small and irregular bone defects. This study aimed to release the antibiotic gentamicin sulfate (Genta) to reduce tissue inflammation and prevent infection in the early stages of bone recovery. Subsequently, the sustained release of the bone-promoting drug ferulic acid (FA) mimicked the response of osteoprogenitor D1 cells interaction, thereby accelerating the healing process of the overall bone repair. Accordingly, the different particle properties of micro-nano hybrid mesoporous bioactive glass (MBG), namely, micro-sized MBG (mMBG) and nano-sized MBG (nMBG), were explored separately to generate different dose releases in MBG/CPC composite bone cement. Results show that nMBG had better sustained-release ability than mMBG when impregnated with the same dose. When 10 wt% of mMBG hybrid nMBG and composite CPC were used, the amount of MBG slightly shortened the working/setting time and lowered the strength but did not hinder the biocompatibility, injectability, anti-disintegration, and phase transformation of the composite bone cement. Furthermore, compared with 2.5wt%Genta@mMBG/7.5 wt% FA@nMBG/CPC, 5wt.%Genta@mMBG/5wt.%FA@nMBG/CPC exhibited better antibacterial activity, better compressive strength, stronger mineralization of osteoprogenitor cell, and similar 14-day slow-release trend of FA. The MBG/CPC composite bone cement developed can be used in clinical surgery to achieve the synergistic sustained release of antibacterial and osteoconductive activities.

The synthesis of Tween80/calcium phosphate nanocomposite bioactive gelatine-based gels as a proof of concept for tooth sensitivity home-treatment

Dentine hypersensitivity interferes with the lifestyle owing to pain arising from exposed dentine surfaces in response to stimuli. One common way to treat this problem is to occlude the exposed tubules. In this work, we have proposed a home-based treatment gel for tooth sensitivity. The gel was prepared using the emulsion method and contained Tween80/calcium phosphate nanocomposite that could occlude the tubules after 10 h of application. In preparation, Tween80 was used as a surfactant, and oleic acid was used as an oil phase to form a water-in-oil nanoreactor for calcium phosphate synthesis. Finally, different concentrations of gelatine were used to transform the emulsion into a stable gel. The nanoparticles had a uniform spherical shape and a diameter of approximately 300 nm. The nanocomposite gel containing the lowest amount of gelatine (Gel-T80-5%GE) exhibited the best liquid-like property and the highest occlusion rate of 95%.

Antimicrobial activity of ion-substituted calcium phosphates: A systematic review

In this systematic review, the antimicrobial effect of ion-substituted calcium phosphate biomaterials was quantitatively assessed. The literature was systematically searched up to the 6th of December 2021. Study selection and data extraction was performed in duplo by two independent reviewers with a modified version of the OHAT tool for risk of bias assessment. Any differences were resolved by consensus or by a referee. A mixed effects model was used to investigate the relation between the degree of ionic substitution and bacterial reduction. Of 1016 identified studies, 108 were included in the analysis. The methodological quality of included studies ranged from 6 to 16 out of 18 (average 11.4). Selenite, copper, zinc, rubidium, gadolinium, silver and samarium had a clear antimicrobial effect, with a log reduction in bacteria count of 0.23, 1.8, 2.1, 3.6, 5.8, 7.4 and 10 per atomic% of substitution, respectively. There was considerable between-study variation, which could partially be explained by differences in material formulation, study quality and microbial strain. Future research should focus on clinically relevant scenarios in vitro and the translation to in vivo prevention of PJI.

Support-less ceramic 3D printing of bioceramic structures using a hydrogel bath

Volumetric bone tissue defects are difficult to address with intrinsic regenerative capacity. With the recent development of ceramic 3D printing, various types of bioceramic scaffolds that can induce bone regeneration are being actively developed. However, hierarchical bone is complex with overhanging structures that are unfavorable to ceramic 3D printing, requiring additional sacrificial supports that may increase the overall process time and material consumption. Additionally, breaks and cracks may occur when sacrificial supports are removed from fabricated ceramic structures. In this study, a support-less ceramic printing (SLCP) process using a hydrogel bath was developed to facilitate the manufacturing of complex bone substitutes. A hydrogel bath, consisting of Pluronic P123 with temperature-sensitive properties, mechanically supported the fabricated structure when the bioceramic ink was extruded into the bath and promoted the cement reaction to cure the bioceramic. SLCP enables the fabrication of complex bone constructs with overhanging structures that cannot be fabricated without sacrificial supports, such as the mandible and maxillofacial bones, with reduced overall processing time and material consumption. Scaffolds fabricated with SLCP showed more cell adhesion, higher cell growth rate, and osteogenic protein expression due to their rougher surface than conventionally printed scaffolds. Hybrid scaffolds were fabricated with SLCP to co-print cells and bioceramics, and SLCP provided a cell-friendly environment, exhibiting high cell viability. SLCP enables control of the shape of various cells, bioactive substances, and bioceramics, which can be used as an innovative 3D bioprinting technique to manufacture complex hierarchical bone structures.

Toward osteomimetic formation of calcium phosphate coatings with carbonated hydroxyapatite

Biomimetic production of coatings on various types of scaffolds is based mainly on simulated body fluid precipitation (SBF) of apatites, or, if the HCO₃^- is present, carbonated apatites. Recently, we proposed formation of calcium phosphates (CaP) precipitates by alkaline phosphatase (ALP) hydrolysing glycerophosphate in presence of calcium ions as an alternative to SBF. Since apatites synthesized in bone by the ALP activity contain carbonate anions, it was tempting to investigate whether the phosphatase method could be advanced into osteomimetic one. Therefore, taking example from the SBF studies, phosphatase incubation medium was enriched with carbonate ions at 4.2 and 27 mM concentration. X-ray diffraction of the precipitates disclosed peaks typical for hydroxyapatite (HAP). FTIR analysis showed that at both concentration of carbonate ions, apatites underwent both B and A substitution, more extensive at higher concentration. Thus, osteomimetic approach produced carbonated hydroxyapatites of the type encountered in bone tissue even at HCO₃^- concentration as low as 4.2 mM. Composite plates made of poly(ε-caprolactone) and mixture of β-tricalcium phosphate and hydroxyapatite at mass ratio of 1:0.5:0.5, respectively, were covered by CaP coatings, i.e., CaP-0, CaP-4.2, CaP-27, by incubation in phosphatase medium containing 0, 4.2 or 27 mM of NaHCO₃, respectively. Pristine or coated PCL50 plates were used to study release of calcium and adsorption/desorption of proteins, or seeded with human bone marrow mesenchymal stem cells (hMSC) for study of cell adhesion, spreading and osteogenic differentiation. Introduction of carbonate into the CaP coatings significantly increased release of Ca²⁺ in a carbonate concentration-dependent manner; the release was up to 4 times higher, when compared to CaP-0 coating, and reached 0.41 ± 0.01 mM for CaP-27 after first 24 h. Coating CaP-4.2 yielded significantly higher adsorption of bovine serum albumin and cytochrome C than CaP-0. All of the CaP coatings improved significantly hMSC adhesion, however, only CaP-4.2 provided 2 times higher cell number than PCL50 after 2 weeks of culture. Interestingly, ALP activity calculated per cell number was the highest on pristine plates, presumably because hMSC differentiate preferentially into osteoblasts at lower seeding densities. It appears, therefore, that the osteomimetic approach may be useful for production of carbonated hydroxyapatite coatings, but requires further studies and replacing intestinal phosphatase used in this work with one originating from bone.

Utilization of carbonated calcium phosphate cement for contouring cranioplasty in patients with syndromic craniosynostosis

PURPOSE

Carbonated calcium phosphate (CCP) cement is an alloplastic material which has been increasingly utilized for cranioplasty reconstruction; however, there is a paucity of data investigating its use in patients with syndromic craniosynostosis. The purpose of this study was to characterize our institutional experience with CCP cement for secondary contouring cranioplasty in these patients to establish safety and aesthetic efficacy.

METHODS

Patients with syndromic craniosynostosis undergoing cranioplasty with CCP cement from 2009 to 2022 were retrospectively reviewed for prior medical and surgical history, cranioplasty size, cement usage, and postoperative complications. Aesthetic ratings of the forehead region were quantified using the Whitaker scoring system at three timepoints: preoperative (T1), < 6 months postoperative (T2), and > 1 year postoperative (T3).

RESULTS

Twenty-one patients were included. Age at surgery was 16.2 ± 2.8 years, forehead cranioplasty area was 135 ± 112 cm², and mass of cement was 17.2 ± 7.8 g. Patients were followed for 3.0 ± 3.1 years. Whitaker scores decreased from 1.9 ± 0.4 at T1 to 1.4 ± 0.5 at T2 (p = 0.005). Whitaker scores at T2 and T3 were not significantly different (p = 0.720). Two infectious complications (9.5%) were noted, one at 4.5 months postoperatively and the other at 23 months, both requiring operative removal of CCP cement.

CONCLUSION

Our results suggest that aesthetic forehead ratings improve after CCP contouring cranioplasty and that the improvement is sustained in medium-term follow-up. Complications were uncommon, suggesting that CCP is relatively safe though longer-term follow-up is needed before reaching definitive conclusions.

Bone formation beyond the skeletal envelope using calcium phosphate granules packed into a collagen pouch - a pilot study

In this proof-of-concept, bone neoformation beyond the skeletal envelope is explored by using a collagen pouch (n = 6) packed with calcium phosphate (CaP) granules placed over the frontal bone in sheep (n=3). At 13 weeks, macroscopic examination showed specimens covered by an adherent fibrinous envelope with slight vascularization. Histology revealed colonization of the implant by newly formed woven bone and fibrous connective tissue. Surface osteoblasts as well as material-filled macrophages, lymphocytes, polymorphonuclear cells and giant cells were also found in large quantities surrounding the newly formed bone tissue inside the collagen pouch. On the side facing the recipient bone, the collagen membrane had to a large extent been resorbed and bridging bone formation was clearly visible between the test article and recipient bone. On the other side facing soft tissue, the collagen pouch remained intact with a visible fibrous capsule. This study demonstrated that the use of a collagen sleeve as a container for CaP granules allows for good neoformation beyond the skeletal envelope with bridging bone formation clearly visible between the test article and recipient bone. Additionally, in this model, macrophages rather than osteoclasts appear to modulate CaP granule resorption and remodelling into new bone. This construct opens new perspectives for treatment methods that could be used for bone augmentation and restoration of cranio-maxillofacial defects and malformations.

Calcium-to-phosphorus releasing ratio affects osteoinductivity and osteoconductivity of calcium phosphate bioceramics in bone tissue engineering

Calcium phosphate (Ca-P) bioceramics, including hydroxyapatite (HA), biphasic calcium phosphate (BCP), and beta-tricalcium phosphate (β-TCP), have been widely used in bone reconstruction. Many studies have focused on the osteoconductivity or osteoinductivity of Ca-P bioceramics, but the association between osteoconductivity and osteoinductivity is not well understood. In our study, the osteoconductivity of HA, BCP, and β-TCP was investigated based on the osteoblastic differentiation in vitro and in situ as well as calvarial defect repair in vivo, and osteoinductivity was evaluated by using pluripotent mesenchymal stem cells (MSCs) in vitro and heterotopic ossification in muscles in vivo. Our results showed that the cell viability, alkaline phosphatase activity, and expression of osteogenesis-related genes, including osteocalcin (Ocn), bone sialoprotein (Bsp), alpha-1 type I collagen (Col1a1), and runt-related transcription factor 2 (Runx2), of osteoblasts each ranked as BCP > β-TCP > HA, but the alkaline phosphatase activity and expression of osteogenic differentiation genes of MSCs each ranked as β-TCP > BCP > HA. Calvarial defect implantation of Ca-P bioceramics ranked as BCP > β-TCP ≥ HA, but intramuscular implantation ranked as β-TCP ≥ BCP > HA in vivo. Further investigation indicated that osteoconductivity and osteoinductivity are affected by the Ca/P ratio surrounding the Ca-P bioceramics. Thus, manipulating the appropriate calcium-to-phosphorus releasing ratio is a critical factor for determining the osteoinductivity of Ca-P bioceramics in bone tissue engineering.

Biomimetic calcium phosphate coating on medical grade stainless steel improves surface properties and serves as a drug carrier for orthodontic applications

OBJECTIVE

Recently, stainless steel (SSL) miniscrew implants have been used in orthodontic clinics as temporary anchorage devices. Although they have excellent physical properties, their biocompatibility is relatively poor. Previously, our group developed a two-phase biomimetic calcium phosphate (BioCaP) coating that can significantly improve the biocompatibility of medical devices. This study aimed to improve the biocompatibility of SSL by coating SSL surface with the BioCaP coating.

METHODS

Titanium (Ti) discs and SSL discs (diameter: 5 mm, thickness: 1 mm) were used in this study. To form an amorphous layer, the Ti discs were immersed in a biomimetic modified Tyrode solution (BMT) for 24 h. The SSL discs were immersed in the same solution for 0 h, 12 h, 24 h, 36 h and 48 h. To form a crystalline layer, the discs were then immersed in a supersaturated calcium phosphate solution (CPS) for 48 h. The surface properties of the BioCaP coatings were analysed. In addition, bovine serum albumin (BSA) was incorporated into the crystalline layer during biomimetic mineralisation as a model protein.

RESULTS

The morphology, chemical composition and drug loading capacity of the BioCaP coating on smooth SSL were confirmed. This coating improved roughness and wettability of SSL surface. In vitro, with the extension of BMT coating period, the cell seeding efficiency, cell spreading area and cell proliferation on the BioCaP coating were increased.

SIGNIFICANCE

These in vitro results show that the BioCaP coating can improve surface properties of smooth medical grade SSL and serve as a carrier system for bioactive agents.

Fabrication of polycaprolactone/calcium phosphates hybrid scaffolds impregnated with plant extracts using 3D printing for potential bone regeneration

The increase in critical bone diseases and defects in the world's population increases the need for bone substitutes to restore form and function. Organic and inorganic scaffolds with antibacterial properties could provide advantages for bone regeneration. In this study, we obtained scaffolds of polycaprolactone (PCL) charged with calcium phosphates nanoparticles and impregnated with extracts of Colombian plants as an alternative for potential bone regeneration. Calcium phosphate nanoparticles were obtained via auto-combustion synthesis. The nanoparticles were incorporated into the PCL with a chemical dissolution-disperse process. The composite obtained was used to produce a filament to print Triply Periodic Minimal Surface (TPMS) based scaffolds. Such geometry facilitates cellular growth thanks to its interconnected porosity. The scaffolds were impregnated with extracts of Justicia cf colorifera (Acanthaceae), and Billia rosea (Sapindaceae) due to their ancestral medical applications. A physical and biological characterization was conducted. The process to print scaffolds with an enhanced geometry to facilitate the flux of biological fluids was successful. The scaffolds loaded with B. rosea showed strong antibacterial behavior, suggesting the presence of reported terpenoids with antibacterial properties. The approach used in this study evidenced promising prospects for bone defect repair.

Introduction of tenomodulin by gene transfection vectors for rat bone tissue regeneration

Introduction

Periodontal ligament is regenerated in association with hard tissue regeneration. Tenomodulin (Tnmd) expression has been confirmed in periodontal ligament and it reportedly inhibits angiogenesis or is involved in collagen fibril maturation. The introduction of Tnmd by gene transfection in bone tissue regeneration therapy might inhibit topical hard tissue formation and induce the formation of dense fibrous tissue. Therefore, the effect of Tnmd introduction by gene transfection technique in vitro and in vivo was investigated in this study.

Methods

Osteogenesis- and chondrogenesis-related gene expression levels in osteoblastic cells (MC3T3E1) and rat bone marrow derived cells were detected using qPCR three days after gene transfection with plasmid DNA (Tnmd) using non-viral gene transfection vectors: a calcium phosphate-based gene transfection vector (CaP(Tnmd)) or a cationic polymer-based reagent (JetPEI (Tnmd)). Next, an atelocollagen scaffold with or without CaP (Tnmd) or JetPEI (Tnmd) was implanted into a rat calvaria bone defect, and the remaining bone defect volume and the tissue reaction at 28 days after surgery were evaluated.

Results

Runx 2 and SP7 mRNA was reduced by JetPEI (Tnmd) in both cells, but not in CaP(Tnmd). The volume of expressed Tnmd was at 9 ng/mL in both gene transfection vector. The remaining bone defect volume of JetPEI (Tnmd) was significantly bigger than that of the other groups and CaP (EGFP), and that of CaP (Tnmd) was significantly bigger than that of CaP (EGFP).

Conclusions

Tnmd introduction treatment inhibits bone formation in artificial bone defect, however, the effect of that was dependent on non-viral gene transfection vector.

An integrated strategy for nutrient harvesting from hydrolyzed human urine as high-purity products: Tracking of precipitation transformation and precise regulation

The nutrient recovery from source-separated urine is of great significance for a sustainable and closed nutrient loop. However, common urine-processing techniques have several constraints, including inefficient recovery, low product purity and incapability of simultaneously harvesting multiple nutrients. In this study, an integrated strategy of P precipitation and N stripping was first proposed to harvest nutrients from hydrolyzed human urine as high-purity products via precisely regulating Ca/P dosing ratio. Ca(OH)2 was utilized to trigger Ca-P precipitation and elevate pH level. Different from the previously reported conventional struvite method, P recovery was oriented to calcium phosphate. P harvesting behavior was investigated as a function of key factors including initial P concentration and the dosing ratio. A thermodynamic model was constructed to unveil the precipitation transformation mechanism and visualize P recovery for an enhanced controllability. For N harvesting, Ca(OH)2 was dosed to increase the pH of the urine to converts ammonium to ammonia. The resulting ammonia was stripped and then adsorbed by H2SO4 as high-purity ammonium sulfate. Moreover, the sulfate derived from acidification treatment was recovered as calcium sulfate in the interests of material recycling and mitigating secondary contaminations. Results exhibited P recovery efficiency could reach 100 % and purity for calcium phosphate could be above 90 % within a Ca/P ratio range of 1.67-2.0. Further boosting pH to 12, over 85 % of S and 95 % of N was retrieved. The comprehensive scheme provides an efficient approach towards the precise P and N harvesting from hydrolyzed urine and advances the knowledge of precipitation transformation mechanism.

Plant growth-promoting properties of the phosphate-solubilizing red yeast Rhodosporidium paludigenum

Phosphorus (P) is one of the essential elements that are necessary for plant development and growth. However, the availability of soluble forms of P for plants in the soils is limited, because a large proportion of it is bound to soil constituents. Thus, the concentration of P available to plants at any time is very low and, moreover, its availability depends on the soil pH. As a solution, phosphate-solubilizing microorganisms (PSMs) are employed that render inorganic P available to plants in soluble form. Thus far, research into PSMs has been insufficient, and only few such organisms have been considered for exploitation as microbial fertilizer strains. The characteristics of plant growth promotion with the plant-PSMs coculture system remain to be elucidated. In the current study, we report on the isolate Rhodosporidium paludigenum JYC100 that exhibits good performance for solubilizing calcium phosphate. We found that it can be regulated by the amount of soluble phosphate. Furthermore, R. paludigenum JYC100 promotes plant growth under specific conditions (P deficiency, but with insoluble phosphate) in different media and soil pots. In contrast, the yeast Aureobasidium pullulans JYC104 exhibited weak phosphate-solubilizing capacities and no plant growth-promoting ability. Compared to control plants, the biomass, shoot height, and cellular inorganic P content of plants increased in plants cocultivated with R. paludigenum JYC100. In addition, histochemical GUS and qRT-PCR assays of phosphate starvation-induced (PSI) genes showed that the transcript levels of these PSI genes are decreased in the plants cocultured with R. paludigenum JYC100. These findings reflect the unique ability of R. paludigenum JYC100 to convert insoluble P compounds to plant-available P, thereby leading to growth promotion. Our study results highlight the use of yeasts as potential substitutes for inorganic phosphate fertilizers to meet the P demands of plants, which may eventually improve yields in sustainable agricultures.

CTAB enabled microwave-hydrothermal assisted mesoporous Zn-doped hydroxyapatite nanorods synthesis using bio-waste Nodipecten nodosus scallop for biomedical implant applications

In biomedical exploration, the predominant characteristic is synthesizing and fabricating multifunctional nanostructure with intensified biocompatibility and excellent antibacterial applications to avoid post-surgical implant failure. The objective of the current study is to examine ideal mesoporous zinc-doped hydroxyapatite (HAp) for future use in the field of biomedical research. In the present investigation, we synthesized mesoporous Zn-doped HAp nanorods with varied mole concentrations using a profound microwave hydrothermal method utilizing bio-waste Nodipecten nodosus scallop as a calcium source and CTAB as an organic modifier. Bio-waste Nodipecten nodosus scallop is a widely available cheap calcium precursor which is converted into pure and zinc-doped hydroxyapatite nanorods with the help of the microwave hydrothermal method. Different analytical techniques like spectroscopy and electron microscopy were employed to evaluate and precisely characterize the structural and morphological characteristics in synthesized pure and mesoporous Zn-doped HAp nanorods. CTAB and microwave hydrothermal methods successfully create mesoporous Zn-doped hydroxyapatite nanorods with different sizes and morphology. Mesoporous Zinc-doped HAp nanorods show excellent antibacterial activity against Klebsiella pneumoniae (MTCC 7407) and Bacillus subtilis (MTCC 1133), compared to other nanorods. ZnHAp-3 shows notable excellent results of antibacterial effect towards K. pneumoniae and B. subtilis, by exhibiting 12.36 ± 0.12 and 13.12 ± 0.16 mm zone of inhibition. Furthermore, ZnHAp-1 shows the lower zone of inhibition, while the ZnHAp-3 sample shows the highest zone of inhibition. A foremost study performed was toxicity assays to validate safe attributes of mesoporous zinc-doped HAp intensified with the proliferation function of the zebrafish model. The results reveal the non-toxic behavior of pure and mesoporous zinc-doped HAp samples. Thus, our studies provide evidence for the synthesis technique for the mesoporous zinc-doped HAp nanorods using a novel CTAB-enabled microwave hydrothermal method utilizing bio-waste Nodipecten nodosus scallop as a calcium source will be alternative affordable biocidal antibacterial materials for controlling post-surgical implant failures.

Phosphorus harvesting from fresh human urine: A strategy of precisely recovering high-purity calcium phosphate and insights into the precipitation conversion mechanism

Phosphorus (P) harvesting from source-separated urine to optimize the overall nutrient loop is one of the most appealing benefits and is a global research interest in wastewater management and treatment. However, current P precipitation is mainly oriented to struvite, which is limited by the issues such as relatively low product purity and high cost of Mg source. Distinguished from previous conventional struvite precipitation, the strategy of precisely harvesting P from fresh human urine as high-purity calcium phosphate was first proposed in this study. This enhanced strategy can optimize P harvesting performance and product purity by simply regulating the consumption of calcium-based materials via model simulation and experimental validation. The thermodynamic model was constructed to probe the precipitation conversion mechanism, and visually predict the component and yield for products under various operating conditions. Batch experiments were conducted to investigate P recovery performance as a function of initial Mg²⁺ concentration, initial pH level, as well as degree of urine hydrolysis. Moreover, the alternative dosing scheme with different calcium salts and alkali was presented, diversifying the options for efficient P recovery. The results showed that, from the perspective of acidic storage for fresh urine, P recovery can be boosted along with eliminating urine hydrolysis. In urine with an initial pH=2.0, P can be completely recovered and purity for calcium phosphate can be optimized to 100% within a Ca/P ratio range of 1.67-2.3. Overall, this work is of great significance for precisely and efficiently harvesting P from urine and provides an integrated strategy for P resource recovery from urine.

Physical, mechanical, and biological characterization of robocasted carbon nanotube reinforced microwave sintered calcium phosphate scaffolds for bone tissue engineering

This study analyses the influence of the addition of Multi Walled Carbon Nanotubes (MWCNT) on the physical, mechanical, and biological behaviour of Calcium Phosphate (CP) bone scaffolds developed using the robocasting technique for bone regeneration. Three different mass percentages (0.5, 1, and 2 wt%) of MWCNT are added to the CP powder and a slurry is prepared using a CMC binder for printing the scaffolds. The scaffolds were printed in 2 infill ratios, 50 and 100%, and were sintered under an inert atmosphere in a microwave furnace which was then taken for various characterization studies. Physical characterisation studies revealed that the shrinkage rate of scaffolds is very low compared to other additive manufacturing techniques. The incorporation of 0.5 wt% of MWCNT produced the best results in mechanical characterization studies with a compressive strength of 10.38 MPa and 11.89 MPa for 50% and 100% infill ratios respectively. In Vitro Biocompatibility studies also proved that 0.5 wt% MWCNT samples are the most suitable for cell growth while the hemocompatibility tests showed that the samples are blood compatible. . The 100% infill samples fared better than the 50% samples in physical and mechanical properties. The results suggest that the MWCNT incorporated CP scaffolds can be used to treat critical size bone defects.

Comparison of synthetic ceramic products formulated with autologous blood coagulum containing rhBMP6 for induction of bone formation

PURPOSE

Osteogrow, an osteoinductive device containing recombinant human Bone Morphogenetic Protein 6 (rhBMP6) in autologous blood coagulum, is a novel therapeutic solution for bone regeneration. This study aimed to evaluate different commercially available calcium phosphate synthetic ceramic particles as a compression-resistant matrix (CRM) added to Osteogrow implants to enhance their biomechanical properties.

METHODS

Osteogrow implants with the addition of Vitoss, ChronOs, BAM, and Dongbo ceramics (Osteogrow-C, where C stands for ceramics) were evaluated in the rodent subcutaneous ectopic bone formation assay. Osteogrow-C device was prepared as follows: rhBMP6 was added to blood, and blood was mixed with ceramics and left to coagulate. Osteogrow-C was implanted subcutaneously in the axillary region of Sprague-Dawley rats and the outcome was analyzed 21 days following implantation using microCT, histology, morphometric analyses, and immunohistochemistry.

RESULTS

Osteogrow-C implants with all tested ceramic particles induced the formation of the bone-ceramic structure containing cortical bone, the bone between the particles, and bone at the ceramic surfaces. The amount of newly formed bone was significant in all experimental groups; however, the highest bone volume was measured in Osteogrow-C implants with highly porous Vitoss ceramics. The trabecular number was highest in Osteogrow-C implants with Vitoss and ChronOs ceramics while trabeculae were thicker in implants containing BAM and Dongbo ceramics. The immunological response and inflammation were comparable among ceramic particles evaluated in this study.

CONCLUSION

Osteogrow-C bone regenerative device was effective with a broad range of commercially available synthetic ceramics providing a promising therapeutic solution for the regeneration of long bone fracture nonunion, large segmental defects, and spinal fusion surgeries.