Calcium Phosphate Deposition Research Articles

Targeting TREM2 signaling shows limited impact on cerebrovascular calcification.

Brain calcification, the ectopic mineral deposits of calcium phosphate, is a frequent radiological finding and a diagnostic criterion for primary familial brain calcification. We previously showed that microglia curtail the growth of small vessel calcification via the triggering receptor expressed in myeloid 2 (TREM2) in the Pdgfb ret/ret mouse model of primary familial brain calcification. Because boosting TREM2 function using activating antibodies has been shown to be beneficial in other disease conditions by aiding in microglial clearance of diverse pathologies, we investigated whether administration of a TREM2-activating antibody could mitigate vascular calcification in Pdgfb ret/ret mice. Single-nucleus RNA-sequencing analysis showed that calcification-associated microglia share transcriptional similarities to disease-associated microglia and exhibited activated TREM2 and TGFβ signaling. Administration of a TREM2-activating antibody increased TREM2-dependent microglial deposition of cathepsin K, a collagen-degrading protease, onto calcifications. However, this did not ameliorate the calcification load or alter the mineral composition and the microglial phenotype around calcification. We therefore conclude that targeting microglia with TREM2 agonistic antibodies is insufficient to demineralize and clear vascular calcifications.

The Remineralization of Enamel from Saliva: A Chemical Perspective

The natural remineralization of enamel is of major importance for oral health. In principle, early erosions (demineralization) induced by acidic beverages and foods as well as initial caries lesions can be covered and remineralized by the deposition of calcium phosphate, i.e., tooth mineral. This remineralization effect is characterized by the presence of calcium and phosphate ions in saliva that form hydroxyapatite on the enamel surface. Although it is apparently a simple crystallization, it turns out that remineralization under in vivo conditions is actually a very complex process. Calcium phosphate can form a number of solid phases of which hydroxyapatite is only one. Precipitation involves the formation of metastable phases like amorphous calcium phosphate that convert into biological apatite in a number of steps. Nanoscopic clusters of calcium phosphate that can attach on the enamel surface are also present in saliva. Thus, remineralization under strictly controlled in vitro conditions (e.g., pH, ion concentrations, no additives) is already complex, but it becomes even more complicated under the actual conditions in the oral cavity. Here, biomolecules are present in saliva, which interact with the forming calcium phosphate mineral. For instance, there are salivary proteins which have the function of inhibiting crystallization to avoid overshooting remineralization. Finally, the presence of bacteria and an extracellular matrix in plaque and the presence of proteins in the pellicle have strong influences on the precipitation on the enamel surface. The current knowledge on the remineralization of the enamel is reviewed from a chemical perspective with a special focus on the underlying crystallization phenomena and the effects of biological compounds that are present in saliva, pellicle, and plaque. Basically, the remineralization of enamel follows the same principles as calculus formation. Notably, both processes are far too complex to be understood on a microscopic basis under in vivo conditions, given the complicated process of mineral formation in the presence of a plethora of foreign ions and biomolecules.

Improving the Bioactivity and Antibiofilm Properties of Metallic Implant Materials via Controlled Surface Microdeformation.

Although metallic implants provide most of the required properties for bone-related applications, especially orthopedic implants, insufficient osseointegration, which may lead to loosening of the implant or prolonged healing time, is still an issue to be resolved. Osseointegration can be improved via application of various surface treatments on the metal surface. The current study focuses on a novel surface microdeformation method, which enables the formation of controlled surface patterns of various parameters. With this purpose, a surface microdeformation procedure was applied on 316L stainless steel surfaces, forming four different patterns which affected various surface parameters such as roughness, surface energy, dislocation activities close to the surface, and wettability. Static immersion tests in a simulated body fluid (SBF) environment showed that modifying the surface parameters via controlled surface patterning promoted the formation of a stable oxide layer and calcium-phosphate (CaP) deposition on the metal surfaces, improving bioactivity. Moreover, the higher amount of CaP deposition and oxide layer formation on the modified surfaces led to reduced ion release, which contributed to improved corrosion resistance. Finally, the effect of the formed surface patterns on antibiofilm formation was investigated via incubation with C. albicans for 24 h, which exhibited that microdeformation patterns remarkably inhibited the biofilm formation. Throughout the experiments, certain patterns yielded outstanding results among the four patterns formed. Overall, it was concluded that forming controlled patterns on stainless steel surfaces via surface microdeformation significantly contributed to the metal's biocompatibility via improving bioactivity, corrosion resistance, and antibiofilm formation properties. Especially, the specific surface properties such as increased surface energy, high surface roughness, and dislocation density close to the metal surface as well as increased hydrophilicity obtained via forming the pattern with relatively deeper and narrowly spaced indents yielded the most promising outcomes. These methodologies constitute novel approaches to be used while designing new methodologies for the surface modification of metallic implant materials for improved osseointegration.

7984 A Challenging Case Of Hyperphosphatemic Familial Tumoral Calcinosis

Abstract Disclosure: T.G. de Souza: None. T.J. Weber: None. Introduction: Hyperphosphatemic Familial Tumoral Calcinosis (hFTC) is a rare, autosomal recessive metabolic disorder characterized by elevated serum phosphate levels and the accumulation of calcium phosphate deposits in soft tissues. There are fewer that 150 genetically confirmed cases in the literature. There are no consensus guidelines; therapeutic approaches are guided by case reports or series. This case serves to heighten awareness of therapeutic strategies including global health considerations for the disabled adult with a rare bone disorder. Case: A 32-year-old African-American woman presented to establish care for hFTC, for which she takes ibuprofen for disabling bilateral hip pain. hFTC was diagnosed in early childhood and managed at a large children’s hospital. Therapeutic modalities relied on operative resection of skin lesions on eruption. She describes cosanguinous parentage, consignment to foster care as a child and homelessness as an adult. She has not had adult endocrine care for her hFTC. Her medical comorbidities include major depressive disorder, PTSD and suicide attempt. She reports one uncle with hFTC noting that his phenotype was not significantly disabling and apparent recession of his lesions with age. Her parents did not have symptoms of hFTC. Radiographically, she had amorphous calcium deposits over both hips (her primary sites of severe pain), upper back (site of painless spontaneous eruptions), and left elbow without pain or skin penetration, as well as hyperostosis of the ilium bilaterally. She noticed waxing and waning of her eruptions with her menstrual cycle, such that lesions worsen in the luteal phase. Megestrol acetate also induced new eruptions. Examination shows brown staining to all teeth with several missing teeth. She had a marked lower extremity limb length discrepancy with severe restriction of hip abduction. Blood chemistries were grossly normal, including renal function, calcium, uric acid and PTH. Serum phosphorous was elevated at 5.2 (2.3 - 4.5 mg/dL). CT showed bilateral nephrocalcinosis. We instituted treatment with a low phosphorous diet, sevelamer to reduce intestinal phosphate absorption and acetazolamide to increase urinary phosphate excretion. For her pain and functional disability, we recommended continued NSAIDs, physical therapy and social work consultation to facilitate continued access to care. Conclusions: This case uniquely describes hFTC symptom fluctuation with the menstrual cycle, worsening with increased progesterone, suggesting a possible role of gonadal hormones on FGF-23 biology. It also highlights the socioeconomic burdens that can accompany rare bone disease, which become more pronounced as the patient achieves adulthood. Successful transition of care from pediatric to adult endocrinologist, in addition to engaging multi-disciplinary support, is essential in optimizing life-long care in hFTC. Presentation: 6/1/2024

The Effect of SiO<sub>2</sub> Addition to the Hydroxyapatite/Curcumin Composite Properties

Hydroxyapatite/curcumin composites have been studied as a calcium phosphate cement candidate. In this research, the effects of adding SiO2 to the hydroxyapatite/curcumin composite on the characteristics of the cement, such as the crystal and surface properties, as well as the release behavior of curcumin in Ringer's solution media, were studied. The composite preparation with and without SiO2 was carried out using a Na2HPO4 2.5% solution. The results showed that the addition of 25% SiO2 to the hydroxyapatite/curcumin composite did not change the crystal properties of hydroxyapatite but produced a more homogenous distribution of the ingredients. The behavior of the composite in Ringer's solution also changes, which is proven by the change in the crystal growth direction and Ca/P ratio. Adding SiO2 produced a composite with a platter and larger particles, as well as a higher Ca/P ratio on the surface. The presence of SiO2 inhibited the release of curcumin in which the ratio of HA: curcumin changed from 77.7%:22.3% to 69.6%:30.4% after 5 d of immersion in Ringer's solution. Thus, besides increasing calcium phosphate deposition on the cement surface, SiO2 also prevents curcumin from being released from the composite.

A calcium delivery system fabricated by poly-γ-glutamic acid: Preparation, characterization, and delivery mechanism studies

Calcium has limited bioavailability owing to the formation of calcium phosphate deposits in the gastrointestinal tract. In this study, a polyglutamic acid (PGA)-Ca complex of calcium chelate was prepared using γ-PGA. The binding constant between γ-PGA and calcium was determined to be 6.50 ± 2.47 × 104 mol/L, where 3.6 units of glutamate was capable of binding one Ca2+. The structure of PGA-Ca was characterized, revealing that Ca2+ chelation promoted the aggregation of γ-PGA molecules, disrupting the network structure and forming a mineralized β-sheet-rich structure. In vitro digestion experiments demonstrated that PGA-Ca better maintained the soluble state of Ca2+ in the intestine compared with CaCl2. Cell absorption experiments showed that PGA-Ca exhibited 20% higher permeability through Caco-2 cell monolayers than CaCl2, indicating its higher bioavailability. Notably, PGA-Ca demonstrated improved absorption in the presence of dietary inhibitors, such as oxalate, tannin, and phytate, which compete with Ca2+. Finally, the molecular mechanism underlying the promotion of calcium absorption by PGA-Ca was investigated using RNA sequencing. The results reveal that PGA-Ca enhanced Ca2+ active transport by upregulating CACNA2D3 and downregulating CBARP, while enhancing paracellular Ca2+ transport by downregulating JAM2. This comprehensive study highlights the potential of PGA-Ca as a highly beneficial calcium-delivery system.

Development of hydroxyapatite/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/gelatin composite nanofibers to improve bone‐forming cell proliferation and mineral deposition

AbstractCalcium phosphate hydroxyapatite (HA) was successfully incorporated into poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/gelatin (PHBV/GEL) nanofibers through an electrospinning process in a hexafluoroisopropanol solvent (HFIP). The PHBV/GEL was electrospun and collected using a rotating metallic network to develop highly ordered nonwoven mats. The effects of HA addition on the morphologies of the obtained fibers were investigated using SEM. The average diameter of the fibers ranged around 700–900 nm, depending on the HA content. From a mechanical perspective, the addition of HA nanoparticles showed variations in tensile strength and elastic modulus values. The lowest tensile strength measured for neat PHBV/GEL was 0.37 ± 0.08 MPa with an elastic modulus of 9.45 ± 0.65 MPa, whereas the highest tensile strength reported for 5% HA‐loaded PHBV/GEL mats was 1.1 ± 0.4 MPa with an elastic modulus of 16.9 ± 0.39 MPa. In addition, cell viability, and mineral deposition were also studied using MC3T3‐E1 pre‐osteoblasts. The in vitro experiment results showed that the HA loaded‐PHBV/GEL mats provide optimal conditions for cell growth and osteogenic differentiation of MC3T3‐E1 cells. This study reveals the potential of PHBV/GEL/HA matrices in the development of novel guided bone‐regeneration (GBR) membranes for orthopedic and craniomaxillofacial surgery, by providing favorable structural features for attachment, growth, and differentiation of osteoblast cells.Highlights Simple and cheap electrospinning strategy toward network‐like fibrous mats. Microstructure, mechanical, and biological features were evaluated. Electrospun PHBV/GEL/HA promoted calcium phosphate deposition by MC3T3‐E1 cells.

Systematic literature review to inform the EULAR recommendations for the use of imaging in crystal-induced arthropathies in clinical practice

ObjectiveTo summarise current data regarding the use of imaging in crystal-induced arthropathies (CiAs) informing a European Alliance of Associations for Rheumatology task force.MethodsWe performed four systematic searches in Embase, Medline...

Laser-induced three-dimensional deposition of calcium phosphate on porous Ti6Al4V

This study developed a 3D deposition technology to form calcium phosphate compounds on the top, interior, and bottom surfaces of a porous Ti6Al4V. The deposition was achieved by laser irradiation of a porous Ti6Al4V in a solution containing Ca and P. The effects of the laser power and specimen thickness on the distribution of deposits were investigated. Under laser irradiation, many petal-like deposits formed directly on the top, interior, and bottom surfaces of the porous Ti6Al4V. Increasing the laser power increased the uniformity of the deposits. The deposits fully covered the porous Ti6Al4V when the laser power was 70 %.

Structure and Properties of Bioactive Titanium Dioxide Surface Layers Produced on NiTi Shape Memory Alloy in Low-Temperature Plasma.

The NiTi alloy, known for its shape memory and superelasticity, is increasingly used in medicine. However, its high nickel content requires enhanced biocompatibility for long-term implants. Low-temperature plasma treatments under glow-discharge conditions can improve surface properties without compromising mechanical integrity. This study explores the surface modification of a NiTi alloy by oxidizing it in low-temperature plasma. We examine the impact of process temperatures and sample preparation (mechanical grinding and polishing) on the structure of the produced titanium oxide layers. Surface properties, including topography, morphology, chemical composition, and bioactivity, were analyzed using TEM, SEM, EDS, and an optical profilometer. Bioactivity was assessed through the deposition of calcium phosphate in simulated body fluid (SBF). The low-temperature plasma oxidization produced titanium dioxide layers (29-55 nm thick) with a predominantly nanocrystalline rutile structure. Layer thickness increased with extended processing time and higher temperatures (up to 390 °C), though the relationship was not linear. Higher temperatures led to thicker layers with more precipitates and inhomogeneities. The oxidized layers showed increased bioactivity after 14 and 30 days in SBF. Low-temperature plasma oxidation produces bioactive titanium oxide layers on NiTi alloys, with a structure and properties that can be tuned through process parameters. This method could enhance the biocompatibility of NiTi alloys for medical implants.

Preparing novel polylactic acid based bone scaffold composites with enhanced calcium phosphate deposition behavior and bioactivity via simple one‐step melt extrusion

AbstractPolylactic acid (PLA) is regarded as the most representative biomedical polymer materials. However, some problems, that is, its big brittleness, high hydrophobicity, and poor bioactivity, limit its application. Here, using poly(butylene adipate‐co‐terephthalate) (PBAT) as toughening agent, and incorporating ethylene diamine tetra(methylene phosphonic acid) (EDTMPA) for the first time with nano‐hydroxyapatite (nHA) as reinforcement filler, series of PLA/PBAT/nHA/EDTMPA as novel bone scaffold composites are successfully prepared via simple one‐step melt extrusion. The chemical composition, microstructures, thermodynamic properties, mechanical properties, hydrophilicity, and bioactivities of PLA/PBAT/nHA/EDTMPA were characterized. The test results show that these developed PLA‐based composites from safe biosources are greatly potential raw materials for bone scaffold because the existence of EDTMPA can chelate with calcium ions to promote calcium phosphate (CaP) deposition on the surface of bone scaffold composites. Especially, when the content of EDTMPA is 6 wt%, the comprehensive performance of the bone scaffold composite is the best. The research results indicate that these developed PLA‐based materials are greatly potential raw materials for bone scaffold composites.

Branched polymer grafted graphene oxide (GO) as a 2D template for calcium phosphate growth

HypothesisGraphene Oxide (GO)-templated deposition of inorganic materials through synthesis on dispersed single sheets of GO is often complicated by the loss of the desired 2D morphology owing to the coagulation of GO sheets at high salt concentrations and non-templated homogenous nucleation. Modifying GO with anionic polymer is expected to solve both problems by i) enhancing electrostatic(steric) stabilization upon exposure to high concentrations of the ionic precursors, and ii) offering additional nucleation sites at the grafted anionic moieties to avoid homogeneous secondary nucleation. ExperimentsGO was grafted with branched copolymers of poly(ethylene glycol) methacrylate (PEGMA 500) and diethylene glycol dimethacrylate (DEGDMA) and ω-vinyl terminated methacrylic acid macromonomer (P(MAA)), the latter serving as an addition-fragmentation chain transfer agent. The colloidal stability of GO dispersions in water toward salt was evaluated before and after modification. Precipitation of calcium phosphate (CaP) was performed by incubating modified GO in the precursor solutions. The conditions were optimized to maximize the nucleation selectively onto GO without homogeneous CaP nucleation and coagulation of the GO-sheets. FindingsThe copolymer grafted GO-sheets shows superior colloidal stability when dispersed in water. No aggregation occurs in the incubating ionic CaP precursor solutions. The optimum templated deposition of CaP onto the GO sheets by precipitation is to add a second shot of precursors after the nucleation stage to obtain GO sheets fully decorated with calcium phosphate nanorods without self-nucleation. Via the careful design on the GO modification and incubation process, the growth of calcium phosphate nanorods were confined in the desired 2D order exclusively, hereby achieving the goal of an efficient GO-templated synthesis.

Morphological and structural analysis of Penaeus vannamei mandibles and an attempt at real-time cannibalism monitoring based on passive acoustics

Cannibalism is a significant factor contributing to individual disability, mortality, and reduced shrimp production in commercial culture. The primary challenge of controlling cannibalism is the real-time and efficient monitoring of its occurrence. Here, we simultaneously captured high-speed video and feeding acoustics to match sound signals to feeding behaviors in Penaeus vannamei. Building upon a feeding acoustics signal acquisition system, passive acoustic monitoring (PAM) was utilized to detect differences in the acoustic signals produced when shrimps fed on broken feed, pellet feed, and meat fragments of P. vannamei (cannibalism). The morphological and structural characteristics of P. vannamei mandibles were analyzed using micro-CT, nano-indentation, and Raman testing. The main findings were: (1) Feeding on meat fragments resulted in a distinct high-frequency impulse train signal that may serve as an effective indicator for monitoring cannibalistic behavior during culture. (2) Shrimps produced similar and stable acoustic signals while consuming pellet feed, broken feed, or meat fragments; however, there were significant differences in the numbers of generated pulses (P < 0.05), with broken feed < pellet feed < meat fragments. (3) The mandibles consisted of thin anterior incisors and flat thick posterior molar processes, both with stratified structures; the mandibles exhibited greater elastic modulus and hardness values in their outer layers than inner layers, and calcium phosphate deposits were present in both incisors and molar processes. The collisions between incisors showed patterns that were highly synchronized with the acoustic feeding signals. This study has expanded research on passive acoustics monitoring in crustaceans and provided crucial data for the development of precious feeding technology in crustaceans.

Alendronate as Bioactive Coating on Titanium Surfaces: An Investigation of CaP-Alendronate Interactions.

The surface modification of dental implants plays an important role in establishing a successful interaction of the implant with the surrounding tissue, as the bioactivity and osseointegration properties are strongly dependent on the physicochemical properties of the implant surface. A surface coating with bioactive molecules that stimulate the formation of a mineral calcium phosphate (CaP) layer has a positive effect on the bone bonding process, as biomineralization is crucial for improving the osseointegration process and rapid bone ingrowth. In this work, the spontaneous deposition of calcium phosphate on the titanium surface covered with chemically stable and covalently bound alendronate molecules was investigated using an integrated experimental and theoretical approach. The initial nucleation of CaP was investigated using quantum chemical calculations at the density functional theory (DFT) level. Negative Gibbs free energies show a spontaneous nucleation of CaP on the biomolecule-covered titanium oxide surface. The deposition of calcium and phosphate ions on the alendronate-modified titanium oxide surface is governed by Ca2+-phosphonate (-PO3H) interactions and supported by hydrogen bonding between the phosphate group of CaP and the amino group of the alendronate molecule. The morphological and structural properties of CaP deposit were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and attenuated total reflectance Fourier transform infrared spectroscopy. This integrated experimental-theoretical study highlights the spontaneous formation of CaP on the alendronate-coated titanium surface, confirming the bioactivity ability of the alendronate coating. The results provide valuable guidance for the promising forthcoming advancements in the development of biomaterials and surface modification of dental implants.

Epigallocatechin-3-gallate inhibits osteogenic differentiation of vascular smooth muscle cells through the transcription factor JunB.

Medial arterial calcification (MAC) accompanying chronic kidney disease (CKD) leads to increased vessel wall stiffness, myocardial ischemia, heart failure, and increased cardiovascular morbidity and mortality. Unfortunately, there are currently no drugs available to treat MAC. The natural polyphenol epigallocatechin-3-gallate (EGCG) has been demonstrated to protect against cardiovascular disease; however, whether EGCG supplementation inhibits MAC in CKD remains unclear. In this study, we utilize a CKD-associated MAC model to investigate the effects of EGCG on vascular calcification and elucidate the underlying mechanisms involved. Our findings demonstrate that EGCG treatment significantly reduces calcium phosphate deposition and osteogenic differentiation of VSMCs in vivo and in vitro in a dose-dependent manner. In addition, through RNA sequencing (RNA-seq) analysis, we show a significant activation of the transcription factor JunB both in CKD mouse arteries and in osteoblast-like VSMCs. Notably, EGCG effectively suppresses CKD-associated MAC by inhibiting the activity of JunB. In addition, overexpression of JunB can abolish while knockdown of JunB can enhance the inhibitory effect of EGCG on the osteogenic differentiation of VSMCs. Furthermore, EGCG supplementation inhibits MAC in CKD via modulation of the JunB-dependent Ras/Raf/MEK/ERK signaling pathway. In conclusion, our study highlights the potential therapeutic value of EGCG for managing CKD-associated MAC, as it mitigates this pathological process through targeted inactivation of JunB.

Formulate Adaptive Biphasic Scaffold via Sequential Protein-Instructed Peptide Co-Assembly.

To ensure compositional consistency while mitigating potential immunogenicity for stem cell therapy, synthetic scaffolds have emerged as compelling alternatives to native extracellular matrix (ECM). Substantial progress has been made in emulating specific natural traits featuring consistent chemical compositions and physical structures. However, recapitulating the dynamic responsiveness of the native ECM involving chemical transitions and physical remodeling during differentiation, remains a challenging endeavor. Here, the creation of adaptive scaffolds is demonstrated through sequential protein-instructed molecular assembly, utilizing stage-specific proteins, and incorporating in situ assembly technique. The procedure is commenced by introducing a dual-targeting peptide at the onset of stem cell differentiation. In response to highly expressed integrins and heparan sulfate proteoglycans (HSPGs) on human mesenchymal stem cell (hMSC), the peptides assembled in situ, creating customized extracellular scaffolds that adhered to hMSCs promoting osteoblast differentiation. As the expression of alkaline phosphatase (ALP) and collagen (COL-1) increased in osteoblasts, an additional peptide is introduced that interacts with ALP, initiating peptide assembly and facilitating calcium phosphate (CaP) deposition. The growth and entanglement of peptide assemblies with collagen fibers efficiently incorporated CaP into the network resulting in an adaptive biphasic scaffold that enhanced healing of bone injuries.

Surface modification of titanium implants via PLLA/HA fibrous composite coating to improve piezoelectric properties

Titanium (Ti)-based implants are among the most advantageous biomaterials in both orthopedic and dental applications, owing to their excellent properties and biocompatibility. However, their bioinert surface poses challenges to osteointegrity, raising concerns about implant loosening. The present study examines the effect of surface modification of Ti by applying a bioactive piezoelectric fibrous coating comprised of electrospun poly(L-lactide) (PLLA) as a biodegradable piezopolymer and varying amounts of hydroxyapatite (HA) filler (5−20 wt%) as an osteoconductive piezoceramic. According to SEM micrographs, adding HA increased the fiber diameter, porosity, and pore size of the fibrous structure. Furthermore, peeling test of the fibrous coating demonstrated that applying a polydopamine (PDA) coating before electrospinning onto the Ti substrate effectively enhanced the adhesion strength of the coating. Additionally, the PLLA/HA composite coating exhibited increased piezoelectric properties, with piezoresponse rising from 2.41 ± 0.192 mV/N (5 wt% HA) to 5.42 ± 0.192 mV/N (20 wt% HA). Similarly, PLLA/HA coatings showed superior apatite-forming ability in simulated body fluid (SBF) at 7 and 28 days, with significantly higher calcium-phosphate deposition and a Ca/P ratio close to natural bone, surpassing the neat PLLA coating and bare Ti substrate. Finally, testing with MG-63 cell lines indicated that fibrous composite coatings enhance cell support, demonstrating optimal alkaline phosphatase (ALP) secretion levels and positive cell attachment. Consequently, the surface-modified Ti with fibrous PLLA/HA coating emerges as a promising strategy for the clinical treatment of bone defects.

Microstructural, mechanical, and biocompatibility properties of Ti–Cu/B4C composites for biomedical applications

This study investigated the effects of B4C on the microstructural, mechanical, and biocompatibility properties of Ti–Cu/B4C composites produced by powder metallurgy. Different amounts of B4C (3, 6, 9, and 12 %) were added to the Ti–Cu matrix. XRD results showed that Ti2Cu, α-Ti, TiB, and B4C phases formed in the microstructure. The addition of B4C and the phases forming in the microstructure resulted in significant increases in the hardness and wear resistance of the composites. SEM images of the wear surfaces showed that the abrasive wear mechanism was dominant. Biodegradability analyses showed that sodium, found in trace amounts in the structure of the alloys, and calcium, released from the structure of B4C into the medium, were the least at the addition of 6 % B4C. Considering the reduced amount of phosphate in the medium, it was found that the mass gain observed in the specimens was due to the deposition of calcium-phosphate precipitates on the surface of the composites. This result suggested that Ti–Cu/B4C alloys were bioactive for bone and may provide osteointegration. Indirect MTT analysis with bone marrow mesenchymal stem cells showed that the specimens were cytotoxic at an acute dose on the first day. However, the cytotoxic effect diminished when they were kept in the PBS medium and replaced every other day for 28 days. Notably, the composite specimen with the addition of 6 % B4C demonstrated maximum cytocompatibility. Consequently, it indicated that adding B4C to the alloy improved osteogenic properties, although it partially increased copper release into the medium.

Fabrication and characterization of β-TCP/Zn-1Mg composite scaffolds for orthopedic applications

Bone tissue defects have emerged as a significant health concern, impacting individuals' overall well-being and daily functionality. The implantation of scaffold materials for bone repair is crucial to structurally replace the damaged bone area, providing essential mechanical support and fulfilling other functional requirements. In this study, in order to develop bone repair scaffold materials with enhanced mechanical properties, moderate corrosion behavior, favorable cytocompatibility, and notable antibacterial activity, xβ-TCP/Zn-1Mg composite scaffolds with varying β-TCP concentrations (x = 0, 0.5, 1, 3) were fabricated using an atmospheric pressure infiltration molding method. The resulting scaffolds featured interconnected and uniformly distributed pores, with an average pore size of approximately 250 μm and a porosity of around 60 %. The xβ-TCP/Zn-1Mg composite scaffolds exhibited a plateau stress ranging from 13.22 to 16.89 MPa and an elastic modulus between 0.62 and 0.82 GPa, closely resembling the mechanical properties of human cancellous bone. The incorporation of β-TCP accelerated the degradation process and promoted calcium phosphate deposition on the specimen's surface. Additionally, the β-TCP/Zn-1Mg composite scaffolds demonstrated significant antibacterial activity against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Furthermore, 2-fold diluted extracts derived from xβ-TCP/Zn-1Mg composite scaffolds were found to enhance the proliferation of MC3T3-E1 pre-osteoblast cells, indicating good cytocompatibility. Therefore, the xβ-TCP/Zn-1Mg scaffold materials hold promise as a compelling candidate for orthopedic applications.

Biomineralization of Polyelectrolyte-Functionalized Electrospun Fibers: Optimization and In Vitro Validation for Bone Applications.

In recent years, polyelectrolytes have been successfully used as an alternative to non-collagenous proteins to promote interfibrillar biomineralization, to reproduce the spatial intercalation of mineral phases among collagen fibrils, and to design bioinspired scaffolds for hard tissue regeneration. Herein, hybrid nanofibers were fabricated via electrospinning, by using a mixture of Poly ɛ-caprolactone (PCL) and cationic cellulose derivatives, i.e., cellulose-bearing imidazolium tosylate (CIMD). The obtained fibers were self-assembled with Sodium Alginate (SA) by polyelectrolyte interactions with CIMD onto the fiber surface and, then, treated with simulated body fluid (SBF) to promote the precipitation of calcium phosphate (CaP) deposits. FTIR analysis confirmed the presence of SA and CaP, while SEM equipped with EDX analysis mapped the calcium phosphate constituent elements, estimating an average Ca/P ratio of about 1.33-falling in the range of biological apatites. Moreover, in vitro studies have confirmed the good response of mesenchymal cells (hMSCs) on biomineralized samples, since day 3, with a significant improvement in the presence of SA, due to the interaction of SA with CaP deposits. More interestingly, after a decay of metabolic activity on day 7, a relevant increase in cell proliferation can be recognized, in agreement with the beginning of the differentiation phase, confirmed by ALP results. Antibacterial tests performed by using different bacteria populations confirmed that nanofibers with an SA-CIMD complex show an optimal inhibitory response against S. mutans, S. aureus, and E. coli, with no significant decay due to the effect of CaP, in comparison with non-biomineralized controls. All these data suggest a promising use of these biomineralized fibers as bioinspired membranes with efficient antimicrobial and osteoconductive cues suitable to support bone healing/regeneration.