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Effective healing and regeneration of various bone defects is still a major challenge and concern in modern medicine. Calcium phosphates have emerged as extensively studied bone substitute materials due to their structural and chemical resemblance to the mineral phase of bone, along with their versatile properties. Calcium phosphates present promising biological characteristics that make them suitable for bone substitution, but a critical limitation lies in their low osteoinductivity. To supplement these materials with properties that promote bone regeneration, prevent infections, and cure bone diseases locally, calcium phosphates can be biologically and therapeutically modified. A promising approach involves combining calcium phosphates with drug-containing liposomes, renowned for their high biocompatibility and ability to provide controlled and sustained drug delivery. Surprisingly, there is a lack of research focused on liposome-calcium phosphate composites, where liposomes are dispersed within a calcium phosphate matrix. This raises the question of why such studies are limited. In order to provide a comprehensive overview of existing liposome and calcium phosphate composites as bioactive substance delivery systems, the authors review the literature exploring the interactions between calcium phosphates and liposomes. Additionally, it seeks to identify potential interactions between calcium ions and liposomes, which may impact the feasibility of developing liposome-containing calcium phosphate composite materials. Liposome capacity to protect bioactive compounds and facilitate localized treatment can be particularly valuable in scenarios involving bone regeneration, infection prevention, and the management of bone diseases. This review explores the implications of liposomes and calcium phosphate material containing liposomes on drug delivery, bioavailability, and stability, offering insights into their advantages. [ABSTRACT FROM AUTHOR]

Calcium phosphate (CaP)-based materials are largely explored in orthopedics, to increase osseointegration of the prostheses and specifically in spine surgery, to permit better fusion. To address these aims, nanostructured biogenic apatite coatings are emerging, since they better mimic the characteristics of the host tissue, thus potentially being better candidates compared to their synthetic counterpart. Here, we compare hydroxyapatite (HA) nanostructured coatings, obtained by ionized jet deposition, starting from synthetic and natural sources. The starting materials and the corresponding films are characterized and compared from a compositional and morphological point of view, then their stability is studied after post-treatment annealing. Although all the films are formed by globular aggregates and show morphological features at different scales (from nano to micro), significant differences are found in composition between the synthetic and naturally derived HA in terms of magnesium and sodium content, carbonate substitution and Ca/P ratio, while differences between the coatings obtained by the different natural HA sources are minor. In addition, the shape of the aggregates is also target-dependent. All coatings have a good stability after over 14 days of immersion in medium, with natural apatite coatings showing a better behavior, as no cracking and detachments are observed during immersion. Based on these results, both synthetic and naturally derived apatitic materials appear promising for applications in spine surgery, with coatings from natural sources possessing physiochemical properties more similar to the mineral phase of the human bone tissue. [ABSTRACT FROM AUTHOR]

Objective(s): For safe and effective gene therapy, the ability to deliver the therapeutic nucleic acid to the target sites is crucial. In this study, lactosylated lipid phosphate calcium nanoparticles (lac-LCP) were developed for targeted delivery of pDNA to the hepatocyte cells. The lac-LCP formulation contained lactose-modified cholesterol (CHL), a ligand that binds to the asialoglycoprotein receptor (ASGR) expressed on hepatocytes, and polyethyleneimine (PEI) in the core. Materials and Methods: Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) were used to monitor the chemical modification, and the physicochemical properties of NPs were studied using dynamic light scattering (DLS) and transmission electron microscopy (TEM). To evaluate transfection efficiency, cellular uptake and GFP expression were assessed using fluorescence microscopy and flow cytometry. Results: The results revealed that lactose-targeted particles (lac-LCP) had a significant increase in cellular uptake by hepatocytes. The inclusion of a low molecular weight PEI (1.8 KDa) with a low PEI/pDNA ratio of 1 in the core of LCP, elicited high degrees of GFP protein expression (by 5 and 6-fold), which exhibited significantly higher efficiency than PEI 1.8 KDa and Lipofectamine. Conclusion: The successful functionalization and nuclear delivery of LCP NPs described here indicate its promise as an efficient delivery vector to hepatocyte nuclei. [ABSTRACT FROM AUTHOR]

Objective(s): For safe and effective gene therapy, the ability to deliver the therapeutic nucleic acid to the target sites is crucial. In this study, lactosylated lipid phosphate calcium nanoparticles (lac-LCP) were developed for targeted delivery of pDNA to the hepatocyte cells. The lac-LCP formulation contained lactose-modified cholesterol (CHL), a ligand that binds to the asialoglycoprotein receptor (ASGR) expressed on hepatocytes, and polyethyleneimine (PEI) in the core. Materials and Methods: Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) were used to monitor the chemical modification, and the physicochemical properties of NPs were studied using dynamic light scattering (DLS) and transmission electron microscopy (TEM). To evaluate transfection efficiency, cellular uptake and GFP expression were assessed using fluorescence microscopy and flow cytometry. Results: The results revealed that lactose-targeted particles (lac-LCP) had a significant increase in cellular uptake by hepatocytes. The inclusion of a low molecular weight PEI (1.8 KDa) with a low PEI/pDNA ratio of 1 in the core of LCP, elicited high degrees of GFP protein expression (by 5 and 6-fold), which exhibited significantly higher efficiency than PEI 1.8 KDa and Lipofectamine. Conclusion: The successful functionalization and nuclear delivery of LCP NPs described here indicate its promise as an efficient delivery vector to hepatocyte nuclei.

This review summarises the available results on the effects of cation substitution on the antibacterial and other bioproperties of different phosphates. Attention is given to bulk cation-substituted phosphates (alkali, alkaline earth, transition and lanthanide metals) and to thin films, glasses, and various composite materials. The cationic effects on the biological properties of phosphate bioceramics are also documented. These phosphate-based biomaterials, especially nanostructured ones, show high biocompatibility and enhanced antibacterial behaviour. Numerous articles have concluded that the cationically substituted phosphates are the best candidates for applications in many biomedical fields such as bone repair, tissue engineering, drug and gene delivery, magnetic targeting and hyperthermia treatment for cancer, bioimaging, and theranostics. [ABSTRACT FROM AUTHOR]

The use of scaffolds, three-dimensional porous, biodegradable and biocompatible structures, that can be produced from natural polymers, synthetics, ceramics and metals is crucial in the tissue engineering field. Chitosan is a polysaccharide of natural origin, found in the exoskeleton of marine arthropods and in the cell wall of fungi, with enormous popularity in the production of three-dimensional materials for Tissue Engineering, in particular bone repair. This polymer has several advantages in the production of these structures in bone regeneration and repair: biodegradability, biocompatibility, non-toxicity and antimicrobial properties. This study aimed to prepare porous scaffolds, for bone repair of degenerative diseases in the spine with better performance and less secondary effects, based on chitosan and another biopolymer (sodium alginate) with the incorporation of calcium phosphates (hydroxyapatite and β-tricalcium phosphate), for tissue engineering application. The obtained scaffolds were object of a detailed characterization, namely with regard to their porosity through the ethanol method, degradation, positron annihilation spectroscopy (PAS), mechanical properties, scanning electronic microscope (SEM), thermal stability through thermogravimetric analysis (TGA), chemical composition through X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results obtained showed that the different scaffolds presented pores able to support osteoid matrix growth. The crosslinking of scaffolds was also evaluated and resulted in pores with smaller dimensions and higher regularity in the chitosan-sodium alginate polymer without calcium phosphate scaffold. It was also possible to observe the effect of inorganics on mixed-matrix scaffolds, both morphologically and chemically. These scaffolds showed promising results in terms of mechanical and chemical properties, along with promising porosity for tissue regeneration applications.

With respect to other fields, bone tissue engineering has significantly expanded in recent years, leading not only to relevant advances in biomedical applications but also to innovative perspectives. Polycaprolactone (PCL), produced in the beginning of the 1930s, is a biocompatible and biodegradable polymer. Due to its mechanical and physicochemical features, as well as being easily shapeable, PCL-based constructs can be produced with different shapes and degradation kinetics. Moreover, due to various development processes, PCL can be made as 3D scaffolds or fibres for bone tissue regeneration applications. This outstanding biopolymer is versatile because it can be modified by adding agents with antimicrobial properties, not only antibiotics/antifungals, but also metal ions or natural compounds. In addition, to ameliorate its osteoproliferative features, it can be blended with calcium phosphates. This review is an overview of the current state of our recent investigation into PCL modifications designed to impair microbial adhesive capability and, in parallel, to allow eukaryotic cell viability and integration, in comparison with previous reviews and excellent research papers. Our recent results demonstrated that the developed 3D constructs had a high interconnected porosity, and the addition of biphasic calcium phosphate improved human cell attachment and proliferation. The incorporation of alternative antimicrobials—for instance, silver and essential oils—at tuneable concentrations counteracted microbial growth and biofilm formation, without affecting eukaryotic cells' viability. Notably, this challenging research area needs the multidisciplinary work of material scientists, biologists, and orthopaedic surgeons to determine the most suitable modifications on biomaterials to design favourable 3D scaffolds based on PCL for the targeted healing of damaged bone tissue. [ABSTRACT FROM AUTHOR]

The use of scaffolds, three-dimensional porous, biodegradable and biocompatible structures, that can be produced from natural polymers, synthetics, ceramics and metals is crucial in the tissue engineering field. Chitosan is a polysaccharide of natural origin, found in the exoskeleton of marine arthropods and in the cell wall of fungi, with enormous popularity in the production of three-dimensional materials for Tissue Engineering, in particular bone repair. This polymer has several advantages in the production of these structures in bone regeneration and repair: biodegradability, biocompatibility, non-toxicity and antimicrobial properties. This study aimed to prepare porous scaffolds, for bone repair of degenerative diseases in the spine with better performance and less secondary effects, based on chitosan and another biopolymer (sodium alginate) with the incorporation of calcium phosphates (hydroxyapatite and β-tricalcium phosphate), for tissue engineering application. The obtained scaffolds were object of a detailed characterization, namely with regard to their porosity through the ethanol method, degradation, positron annihilation spectroscopy (PAS), mechanical properties, scanning electronic microscope (SEM), thermal stability through thermogravimetric analysis (TGA), chemical composition through X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results obtained showed that the different scaffolds presented pores able to support osteoid matrix growth. The crosslinking of scaffolds was also evaluated and resulted in pores with smaller dimensions and higher regularity in the chitosan-sodium alginate polymer without calcium phosphate scaffold. It was also possible to observe the effect of inorganics on mixed-matrix scaffolds, both morphologically and chemically. These scaffolds showed promising results in terms of mechanical and chemical properties, along with promising porosity for tissue regeneration applications. [ABSTRACT FROM AUTHOR]

In this work, a novel series of borophosphate glasses of the system 40B 2 O 3 –25P 2 O 5 –(20-x)Na 2 O–15CaF 2 –xMgO (x = 0, 2.5, 5, 7.5, and 10 mol%) were synthesized using the melt-quenching technique. The effect of replacing Na 2 O with MgO in the glasses was analyzed by the physical and bioactive properties. The glasses were characterized by density, molar volume, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Differential thermal analysis (DTA), bioactivity tests in simulated body fluid (SBF), pH measurements, mass loss, and verification of cellular compatibility in RAW 247 murine macrophages. XRD and FTIR analyses were performed before and after immersion in SBF to verify the bioactivity. Density, molar volume and FTIR results before SBF showed structural changes in the glasses due to the addition of MgO. The pH and mass loss measurements allowed to verify the degradation behavior of the glass series as a function of MgO concentration. The DTA data showed an increase in T g , T x, and thermal stability due to the increase in MgO addition. XRD and FTIR analyses after SBF soaking showed superficial formation of apatites and other calcium phosphates of biological interest in the samples, attesting the bioactivity. Cytotoxicity assessed by MTT assay on the cell line RAW 247 showed that at a concentration of 500 μg/mL all glasses were compatible (non-cytotoxic). The results suggest that the synthesized glasses are bioactive, with the sample containing 5 mol% MgO exhibiting the bioactivity and biocompatibility required for biomaterial applications. [ABSTRACT FROM AUTHOR]

Background: The efficiency of feed calcium phosphates is determined by the presence of phosphorus and calcium, and the quality is determined by the proportion of digestible forms, the concentration of impurities: F, Pb, As, Cd, Hg Purpose. To study the ways of obtaining feed phosphates from desulfated EPA based on the corresponding concentrate and lime. Methodology: The importance of feed phosphates in animal husbandry and the state of their production are given. The processes of obtaining dicalcium phosphate in the recycle mode and tricalcium phosphate in the non-recycle mode were studied using extraction phosphoric acid. Originality. The obtained di- and tricalcium phosphates fully comply with the requirements of GOST 23999-80. Findings. The optimal acid rate was determined when using H3PO4 with a concentration of 50.55% P2O5 to obtain dicalcium phosphate. [ABSTRACT FROM AUTHOR]

This study investigates the profound impact of the ZrO2 inclusion volume on the characteristics of Al2O3/ZrO2 nanocomposites, particularly influencing the formation of calcium phosphates on the surface. This research, aimed at advancing tissue engineering, prepared nanocomposites with 5, 10, and 15 vol% ZrO2, subjecting them to chemical surface treatment for enhanced calcium phosphate deposition sites. Biomimetic coating with Sr-enriched simulated body fluid (SBF) further enhanced the bioactivity of nanocomposites. While the ZrO2 concentration heightened the oxygen availability on nanocomposite surfaces, the quantity of Sr-containing phosphate was comparatively less influenced than the formation of calcium phosphate phases. Notably, the coated nanocomposites exhibited a high cell viability and no toxicity, signifying their potential in bone tissue engineering. Overall, these findings contribute to the development of regenerative biomaterials, holding promise for enhancing bone regeneration therapies. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the influence of cross-linking and reinforcements in gelatin on the physico-mechanical properties of obtained composites. The gelatin-based composites cross-linked with citric acid (CA) were prepared: gelatin type B (GB) and β-tricalcium phosphate (β-TCP) and novel hybrid composite GB with β-TCP and hydroxyapatite (HAp) particles, and their structure, thermal, and mechanical properties were compared with pure gelatin B samples. FTIR analysis revealed that no chemical interaction between the reinforcements and gelatin matrix was established during the processing of hybrid composites by the solution casting method, proving the particles had no influence on GB cross-linking. The morphological investigation of hybrid composites revealed that cross-linking with CA improved the dispersion of particles, which further led to an increase in mechanical performance. The microindentation test showed that the hardness value was increased by up to 449%, which shows the high potential of β-TCP and HAp particle reinforcement combined with CA as a cross-linking agent. Furthermore, the reduced modulus of elasticity was increased by up to 288%. Results of the MTT assay on L929 cells have revealed that the hybrid composite GB-TCP-HA-CA was not cytotoxic. These results showed that GB cross-linked with CA and reinforced with different calcium phosphates presents a valuable novel material with potential applications in dentistry. [ABSTRACT FROM AUTHOR]

Processing-structure-property relationships of 3D-printed multi-scale porous ceramics were investigated. Direct ink writing (DIW) of oil-templated colloidal pastes produced hierarchically porous beta-tricalcium phosphate (TCP) scaffolds. Print architecture and microporosity within filaments were varied, mimicking bone structure. The scaffolds exhibited 60–70 % porosity with interconnected macropores 300–700 μm and microporosity within the filaments at the 10 micron-scale. Varying surfactant and oil concentrations created two micro-pore morphologies – bubble-like pores (emulsion) and channel-like pores (capillary suspension). Emulsion scaffolds were stronger, stiffer and more reliable than capillary suspension scaffolds under both compression and bending. Reducing nozzle diameter and inter-filament distance improved strength and stiffness, at lower density. Immersed at physiological pH, the hierarchically porous TCP scaffolds' strength and modulus degraded at a moderate rate suitable for bone tissue engineering (BTE). Mechanical behavior can be controlled by manipulating process parameters which influence the material's structure. These properties were comparable with trabecular bone, promising for BTE.

The development of 3D-printed calcium phosphate bone grafts represents a breakthrough for personalized bone tissue engineering. However, their high brittleness is a limiting factor for clinical applications. The present work aims to overcome this drawback by developing a composite ink for direct ink writing using a polycaprolactone solution (20 wt% in pyridine) as binder for a self-hardening α-tricalcium phosphate powder. The ink consolidation results from a two-step process. First, evaporation of the solvent gives rise to a flexible green body, in which the polymer matrix retains the loose ceramic particles. Subsequently, upon contact with water, the hydrolysis of these particles creates a continuous network of biomimetic hydroxyapatite nanocrystals, with the consequent hardening of the ink. The presence of the polymer improves the mechanical properties, increasing the flexural strength from 2 to 4 MPa and the strain energy density from 0.2 to 1.1 kJ/m3. Unlike the inks based on hydrogel binders, where the hardening reaction starts as soon as the liquid and solid components are mixed, the ink prepared with the non-aqueous binder is stable, with over 5 months shelf life, and allows the hardening reaction to be triggered at will by contact with water.

The Posner molecule (calcium phosphate trimer, Ca9(PO4)6) has been hypothesized to function as a biological quantum information processor due to its supposedly long-lived entangled 31P nuclear spin states. This hypothesis was challenged by our recent finding that the molecule lacks a well-defined rotational axis of symmetry─an essential assumption in the proposal for Posner-mediated neural processing─and exists as an asymmetric dynamical ensemble. Following up, we investigate here the spin dynamics of the molecule's entangled 31P nuclear spins within the asymmetric ensemble. Our simulations show that entanglement between two nuclear spins prepared in a Bell state in separate Posner molecules decays on a subsecond time scale─much faster than previously hypothesized, and not long enough for supercellular neuronal processing. Calcium phosphate dimers (Ca6(PO4)4) however, are found to be surprisingly resilient to decoherence and are able to preserve entangled nuclear spins for hundreds of seconds, suggesting that neural processing might occur through them instead.

Candida spp. periprosthetic joint infections are rare but difficult-to-treat events, with a slow onset, unspecific symptoms or signs, and a significant relapse risk. Treatment with antifungals meets with little success, whereas prosthesis removal improves the outcome. In fact, Candida spp. adhere to orthopedic devices and grow forming biofilms that contribute to the persistence of this infection and relapse, and there is insufficient evidence that the use of antifungals has additional benefits for anti-biofilm activity. To date, studies on the direct antifungal activity of silver against Candida spp. are still scanty. Additionally, polycaprolactone (PCL), either pure or blended with calcium phosphate, could be a good candidate for the design of 3D scaffolds as engineered bone graft substitutes. Thus, the present research aimed to assess the antifungal and anti-biofilm activity of PCL-based constructs by the addition of antimicrobials, for instance, silver, against C. albicans and C. auris. The appearance of an inhibition halo around silver-functionalized PCL scaffolds for both C. albicans and C. auris was revealed, and a significant decrease in both adherent and planktonic yeasts further demonstrated the release of Ag+ from the 3D constructs. Due to the combined antifungal, osteoproliferative, and biodegradable properties, PCL-based 3D scaffolds enriched with silver showed good potential for bone tissue engineering and offer a promising strategy as an ideal anti-adhesive and anti-biofilm tool for the reduction in prosthetic joints of infections caused by Candida spp. by using antimicrobial molecule-targeted delivery. [ABSTRACT FROM AUTHOR]

Human mesenchymal stromal cells (hMSCs) seeded on calcium phosphate (CaP) bioceramics are extensively explored in bone tissue engineering and have recently shown effective clinical outcomes. In previous pre-clinical studies, hMSCs-CaP-mediated bone formation was preceded by osteoclastogenesis at the implantation site. The current study evaluates to what extent phase composition of CaPs affects the osteoclast response and ultimately influence bone formation. To this end, four different CaP bioceramics were used, hydroxyapatite (HA), β-tricalcium phosphate (β-TCP) and two biphasic composites of HA/β-TCP ratios of 60/40 and 20/80 respectively, for in vitro osteoclast differentiation and correlation with in vivo osteoclastogenesis and bone formation. All ceramics allowed osteoclast formation in vitro from mouse and human precursors, except for pure HA, which significantly impaired their maturation. Ectopic implantation alongside hMSCs in subcutis sites of nude mice revealed new bone formation at 8 weeks in all conditions with relative amounts for β-TCP > biphasic CaPs > HA. Surprisingly, while hMSCs were essential for osteoinduction, their survival did not correlate with bone formation. By contrast, the degree of early osteoclastogenesis (2 weeks) seemed to define the extent of subsequent bone formation. Together, our findings suggest that the osteoclastic response could be used as a predictive marker in hMSC-CaP-based bone regeneration and strengthens the need to understand the underlying mechanisms for future biomaterial development. The combination of mesenchymal stromal cells (MSCs) and calcium phosphate (CaP) materials has demonstrated its safety and efficacy for bone regeneration in clinical trials, despite our insufficient understanding of the underlying biological mechanisms. Osteoclasts were previously suggested as key mediators between the early inflammatory phase following biomaterial implantation and the subsequent bone formation. Here we compared the affinity of osteoclasts for various CaP materials with different ratios of hydroxyapatite to β-tricalcium phosphate. We found that osteoclast formation, both in vitro and at early stages in vivo, correlates with bone formation when the materials were implanted alongside MSCs in mice. Surprisingly, MSC survival did not correlate with bone formation, suggesting that the number or phenotype of osteoclasts formed was more important. [Display omitted] [ABSTRACT FROM AUTHOR]

Three-dimensional bioprinting is a promising technology for bone tissue engineering. However, most hydrogel bioinks lack the mechanical and post-printing fidelity properties suitable for such hard tissue regeneration. To overcome these weak properties, calcium phosphates can be employed in a bioink to compensate for the lack of certain characteristics. Further, the extracellular matrix of natural bone contains this mineral, resulting in its structural robustness. Thus, calcium phosphates are necessary components of bioink for bone tissue engineering. This review paper examines different recently explored calcium phosphates, as a component of potential bioinks, for the biological, mechanical and structural properties required of 3D bioprinted scaffolds, exploring their distinctive properties that render them favorable biomaterials for bone tissue engineering. The discussion encompasses recent applications and adaptations of 3D-printed scaffolds built with calcium phosphates, delving into the scientific reasons behind the prevalence of certain types of calcium phosphates over others. Additionally, this paper elucidates their interactions with polymer hydrogels for 3D bioprinting applications. Overall, the current status of calcium phosphate/hydrogel bioinks for 3D bioprinting in bone tissue engineering has been investigated. [ABSTRACT FROM AUTHOR]

Heterogeneous and mechanochemical syntheses of new materials based on titanium, calcium, and magnesium phosphates were developed for the first time. The products demonstrated high efficiency as sorbents for the removal of heavy metal cations and radionuclides from solutions. The joint action of the sorption components ensures high sorption capacity towards various cations over a wide pH range. The optimal conditions providing products with a specified phase composition were identified. The use of a solution of a phosphorus-containing agent and solid precursors taken in a stoichiometric ratio, together with mild hydrothermal conditions make it possible to minimize the amount of liquid waste. In the first step of the synthesis, precipitation of titanium phosphate and formation of the precursor needed for the second step (formation of calcium and magnesium phosphates) take place simultaneously. Thus, the synthesis protocol complies with the green chemistry principles. [ABSTRACT FROM AUTHOR]

Creating bioactive materials for bone tissue regeneration and augmentation remains a pertinent challenge. One of the most promising and rapidly advancing approaches involves the use of low-temperature ceramics that closely mimic the natural composition of the extracellular matrix of native bone tissue, such as Hydroxyapatite (HAp) and its phase precursors (Dicalcium Phosphate Dihydrate—DCPD, Octacalcium Phosphate—OCP, etc.). However, despite significant scientific interest, the current knowledge and understanding remain limited regarding the impact of these ceramics not only on reparative histogenesis processes but also on the immunostimulation and initiation of local aseptic inflammation leading to material rejection. Using the stable cell models of monocyte-like (THP-1ATRA) and macrophage-like (THP-1PMA) cells under the conditions of LPS-induced model inflammation in vitro, the influence of DCPD, OCP, and HAp on cell viability, ROS and intracellular NO production, phagocytosis, and the secretion of pro-inflammatory cytokines was assessed. The results demonstrate that all investigated ceramic particles exhibit biological activity toward human macrophage and monocyte cells in vitro, potentially providing conditions necessary for bone tissue restoration/regeneration in the peri-implant environment in vivo. Among the studied ceramics, DCPD appears to be the most preferable for implantation in patients with latent inflammation or unpredictable immune status, as this ceramic had the most favorable overall impact on the investigated cellular models. [ABSTRACT FROM AUTHOR]

The occurrence of bone disorders is steadily increasing worldwide. Bone tissue engineering (BTE) has emerged as a promising alternative to conventional treatments of bone defects, developing bone scaffolds capable of promoting bone regeneration. In this research, biomimetic scaffolds based on ion-substituted calcium phosphates, derived from cuttlefish bone, were prepared using a hydrothermal method. To synthesize Mn2+-substituted scaffolds, three different manganese concentrations (corresponding to 1, 2.5, and 5 mol% Mn substitutions for Ca into hydroxyapatite) were used. Also, syntheses with the simultaneous addition of an equimolar amount (1 mol%) of two (Mg2+ and Sr2+) or three ions (Mn2+, Mg2+, and Sr2+) were performed. A chemical, structural, and morphological characterization was carried out using X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The effects of the ion substitutions on the lattice parameters, crystallite sizes, and fractions of the detected phases were discussed. Multi-substituted (Mn2+, Mg2+, and Sr2+) scaffolds were coated with polycaprolactone (PCL) using simple vacuum impregnation. The differentiation of human mesenchymal stem cells (hMSCs), cultured on the PCL-coated scaffold, was evaluated using histology, immunohistochemistry, and reverse transcription–quantitative polymerase chain reaction analyses. The expression of collagen I, alkaline phosphatase, and dentin matrix protein 1 was detected. The influence of PCL coating on hMSCs behavior is discussed. [ABSTRACT FROM AUTHOR]

ObjectiveTo delineate the role of the urinary metabolome in the genesis of urinary stone disease (USD).MethodsUntargeted metabolomics was utilized in comparative analyses of calcium-based stones (CBS) and spot urine samples from patients with a history of USD with or without urinary stone activity based on radiologic imaging. Stone and urine metabolomes were stratified by composition and radiographic stone-activity, respectively. Additionally, we quantified highly abundant metabolites that were present in either calcium oxalate (CaOx) or calcium phosphate (CaPhos) stones and also significantly enriched in the urine of active stone formers (SF) compared to non-active SF. These data were used to delineate either a direct involvement of urinary metabolites in lithogenesis or the passive uptake of biomolecules within the stone matrix.ResultsUrinary metabolomes were distinct based on radiographic stone-activity and the 2 types of CBS. Stratification by radiologic stone activity was driven by the enrichment of 14 metabolites in the urine of active SF that were also highly abundant in both CaOx and CaPhos stones, indicative of a potential involvement of these metabolites in lithogenesis. Using the combination of these 14 metabolites in total, we generated a model that correctly classified patients as either active vs non-active SF in a prospectively recruited cohort with 73% success.ConclusionCollectively, our data suggest specific urinary metabolites directly contribute to the formation of urinary stones and that active SF may excrete higher levels of lithogenic metabolites than non-active patients. Future studies are needed to confirm these findings and establish the causative mechanisms associated with these metabolites.

Rapid degradation in body fluids is known to be the main shortcoming of the AZ31 magnesium alloy that is aimed to be controlled in this study by chemical conversion of its surface in various phosphate and chloride solutions. Deposited layers on the surface of bare alloy plates were subjected to compositional and morphological analyses to assess their performance as barriers to degradation. Also changes in the mass of the samples and pH of the solutions were monitored during 21 day immersion periods. Formations of prismatic, platelike, needlelike crystals of various compositions including calcium phosphates, magnesium phosphates, magnesium chlorides were observed by scanning electron microscopy and their atomic compositions were determined by EDX and quantitative XRD analyses. The results indicate that a layer of ceramic of various thicknesses can stably form on the base alloy by simple adsorption of the particles suspended in the solution or by nucleation and growth of the products of reactions between dissolved ions and the metal ions released from the surface. These deposition layers that are solely induced by the electrochemical potential of the species in the solution offer facile surface modification methods and novel phases to control the degradation of magnesium alloys in aggressive environments such as body fluids or marine environments.

Calcium phosphate (CaP)-based materials are largely explored in orthopedics, to increase osseointegration of the prostheses and specifically in spine surgery, to permit better fusion. To address these aims, nanostructured biogenic apatite coatings are emerging, since they better mimic the characteristics of the host tissue, thus potentially being better candidates compared to their synthetic counterpart. Here, we compare hydroxyapatite (HA) nanostructured coatings, obtained by ionized jet deposition, starting from synthetic and natural sources. The starting materials and the corresponding films are characterized and compared from a compositional and morphological point of view, then their stability is studied after post-treatment annealing. Although all the films are formed by globular aggregates and show morphological features at different scales (from nano to micro), significant differences are found in composition between the synthetic and naturally derived HA in terms of magnesium and sodium content, carbonate substitution and Ca/P ratio, while differences between the coatings obtained by the different natural HA sources are minor. In addition, the shape of the aggregates is also target-dependent. All coatings have a good stability after over 14 days of immersion in medium, with natural apatite coatings showing a better behavior, as no cracking and detachments are observed during immersion. Based on these results, both synthetic and naturally derived apatitic materials appear promising for applications in spine surgery, with coatings from natural sources possessing physiochemical properties more similar to the mineral phase of the human bone tissue.

The increasing use of TiO2 nanomaterials (TiNMs) in bone tissue engineering raises concerns about their biocompatibility. To date, majority of biological testing was focused on the cytotoxicity of TiO2 nanoparticles and their composites. However, evaluation of immunocompatibility and effects on hemostasis is crucial for successful clinical applications of bone regeneration materials. Such data are scarce for TiNMs. To fill this gap, this study aimed to investigate impact of TiNMs with different morphologies and their composites with calcium deficient hydroxyapatite (CaDHA/TiNMs) on hemostasis, as well as the cell viability and inflammatory response of Jurkat T cells. Four different TiNMs, nanoparticles (TiNPs), nanoplates (TiNPls), nanotubes (TiNTs), nanowires (TiNWs), and their composites with CaDHA were studied. Among investigated materials, the least effect was observed for CaDHA. Effect on plasma coagulation was observed only for TiNPs, which shortened the prothrombin time. All TiNMs affected global hemostasis, especially the elongated TiNWs. Coating TiNMs with CaDHA resulted in a less pronounced effect compared to TiNMs. No significant effect on the viability of Jurkat T cells was observed for TiNMs, while composites increased it. Analysis of the expression of pro-inflammatory (IL-6, IL-8 and TNFα) and anti-inflammatory (IL-10) cytokines indicated inflammatory potential of investigated materials. Among TiNMs, TiNWs had the most pronounced pro-inflammatory effect, while CaDHA/TiNTs and CaDHA/TiNWs showed the most pronounced effect among composites. The obtained results confirm the potential of investigated materials for biomedical applications. However, further studies are needed to establish a more precise relationship between the materials' physico-chemical properties and their biological effects, thus ensuring their safe application. [ABSTRACT FROM AUTHOR]

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The behavior of primarily isolated human stromal cells including dermal fibroblasts and mesenchymal stem/stromal cells (MSCs) upon interaction with ceramic materials based on tricalcium phosphate (TCP) with different pore sizes is studied. The effect of the emulsifier on the rheological characteristics of photosensitive emulsions based on calcium phosphate is investigated. The dependence of the conditions of preparation of photosensitive emulsions on the pore size in ceramic materials based on Ca3(PO4)2 is demonstrated. Studies of the biocompatibility of macroporous bioceramics upon cultivation of human stromal cells and effect of the samples of the material with different pore sizes on the in vitro transcriptional activity of MSCs are carried out. [ABSTRACT FROM AUTHOR]

The dependence of (Zn, Cu, Co, Ni, Mn)-substituted calcium phosphates on the synthesis method was studied. The phosphates were synthesized by precipitation from aqueous solution and by mechanoactivation-assisted heterophase synthesis. Phosphates with metal : phosphorus ratios of 1.5 and 1.67 were obtained, which are precursors of tricalcium phosphate and hydroxyapatite, respectively. The obtained samples were studied by AES-ICP and flame AAS. The contents of Zn, Cu, Co, Ni, and Mn in the samples and the mother liquors were quantitatively determined. It was found that the contents of Cu2+, Zn2+, Co2+, and Ni2+ ions in the phosphates are greatly underestimated in comparison with the calculated amounts introduced in the synthesis. Meanwhile, for tricalcium phosphate, precipitation from solution and the heterophase synthesis gave comparable values of the contents of the dopant ions. At the same time, the heterophase synthesis of substituted hydroxyapatites increases the content of the dopant ion in the product by ~48%. [ABSTRACT FROM AUTHOR]

Hyaline articular cartilage has unique physiological, biological, and biomechanical properties with very limited self-healing ability, which makes the process of cartilage regeneration extremely difficult. Therefore, research is currently focused on finding new and potentially better treatment options. The main objective of this in vivo study was to evaluate a novel biocement CX consisting of tetracalcium phosphate–monetit biocement hardened with a phytic acid–phytase mixture for the regeneration of osteochondral defects in sheep. The results were compared with tetracalcium phosphate–monetit biocement with classic fast-setting cement systems and untreated defects. After 6 months, the animals were sacrificed, and the samples were evaluated using macroscopic and histologic methods as well as X-ray, CT, and MR-imaging techniques. In contrast to the formation of fibrous or fibrocartilaginous tissue on the untreated side, treatment with biocements resulted in the formation of tissue with a dominant hyaline cartilage structure, although fine fibres were present (p < 0.001). There were no signs of pathomorphological changes or inflammation. Continuous formation of subchondral bone and hyaline cartilage layers was present even though residual biocement was observed in the trabecular bone. We consider biocement CX to be highly biocompatible and suitable for the treatment of osteochondral defects. [ABSTRACT FROM AUTHOR]

Composite hydrogels containing apatite-like particles can act as scaffolds for osteoblast proliferation, with applications in bone tissue engineering. In this respect, porous biocompatible hydrogels were obtained from chitosan, oxidized pullulan, and PVA in different ratios. The stability of the hydrogels was ensured both by covalent bonds between aldehyde groups of oxidized pullulan and free amino groups of chitosan, and by physical bonds formed during freeze–thaw cycles and lyophilization. The deposition of calcium phosphates was performed by alternate soaking of the porous hydrogels into solutions with calcium and phosphate ions, assuring a basic pH required for hydroxyapatite formation. The mineralized hydrogels were characterized using FTIR spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis, showing that inorganic particles containing between 80 and 92% hydroxyapatite were deposited in a high amount on the pore walls of the polymeric matrix. The composition of the organic matrix influenced the crystallization of calcium phosphates and the mechanical properties of the composite hydrogels. In vitro biological tests showed that mineralized hydrogels support the proliferation of MG-63 osteoblast-like cells to a greater extent compared to pristine hydrogels. [ABSTRACT FROM AUTHOR]

The preparation of specially doped calcium phosphates (CaPs) is receiving a great deal of attention from researchers due to CaPs' enhanced capabilities for application in medicine. Complexation and precipitation in a complicated electrolyte system including simulated body fluids that are enriched with Mg2+ and Zn2+ ions and modified with glycine, alanine and valine were first evaluated using a thermodynamic equilibrium model. The influence of the type and concentration of amino acid on the incorporation degree of Mg and Zn into the solid phases was predicted. Experimental studies, designed on the basis of thermodynamic calculations, confirmed the predictions. Amorphous calcium phosphates double-doped with Mg and Zn were biomimetically precipitated and transformed into Mg, Zn-β—tricalcium phosphates (TCP) upon calcination. The Rietveld refinement confirmed that Mg2+ and Zn2+ substituted Ca2+ only at the octahedral sites of β-TCP, and in some cases, fully displacing the Ca2+ from them. The resulting Mg, Zn-β–TCP can serve as a reservoir for Mg and Zn ions when included in the formulation of a biomaterial for bone remodeling. The research conducted reveals the effect of combining mathematical models with experimental studies to pre-evaluate the influence of various additives in the design of materials with predetermined properties. [ABSTRACT FROM AUTHOR]

The possibility of regulating the structure and morphology of precipitates forming in the CaO–P2O5–H2O system in the low concentration region during neutralization of acidic solutions with lime milk is studied. The effect of the main technological parameters (temperature and pH) on the crystallization of calcium phosphates from dilute CaO–P2O5–H2O solutions, other conditions being equal, is determined. The formation of dicalcium phosphate under neutralization of the model acidic solutions in the range of pH 4.5–6.5 is reported; at higher pH values, the formation of tricalcium phosphate crystalline hydrate is observed. The formation of hydroxyapatite crystals is not established. It is demonstrated by the physicochemical analysis of the forming precipitates that an increase in the neutralization temperature facilitates an increase in the tricalcium phosphate crystallization rate at lower pH values. [ABSTRACT FROM AUTHOR]

The aim of this work is to review the application of bioceramic materials in the context of current regenerative dentistry therapies, focusing on the latest advances in the synthesis of advanced materials using the sol–gel methodology. Chemical synthesis, processing and therapeutic possibilities are discussed in a structured way, according to the three main types of ceramic materials used in regenerative dentistry: bioactive glasses and glass ceramics, calcium phosphates and calcium silicates. The morphology and chemical composition of these bioceramics play a crucial role in their biological properties and effectiveness in dental therapeutics. The goal is to understand their chemical, surface, mechanical and biological properties better and develop strategies to control their pore structure, shape, size and compositions. Over the past decades, bioceramic materials have provided excellent results in a wide variety of clinical applications related to hard tissue repair and regeneration. Characteristics, such as their similarity to the chemical composition of the mineral phase of bones and teeth, as well as the possibilities offered by the advances in nanotechnology, are driving the development of new biomimetic materials that are required in regenerative dentistry. The sol–gel technique is a method for producing synthetic bioceramics with high purity and homogeneity at the molecular scale and to control the surfaces, interfaces and porosity at the nanometric scale. The intrinsic nanoporosity of materials produced by the sol–gel technique correlates with the high specific surface area, reactivity and bioactivity of advanced bioceramics. [ABSTRACT FROM AUTHOR]

Continuous microwave-assisted flow synthesis has been used as a simple, more efficient, and low-cost route to fabricate a range of nanosized (<100 nm) strontium-substituted calcium phosphates. In this study, fine nanopowder was synthesized via a continuous flow synthesis with microwave assistance from the solutions of calcium nitrate tetrahydrate (with strontium nitrate as Sr2+ ion source) and diammonium hydrogen phosphate at pH 10 with a time duration of 5 min. The morphological characterization of the obtained powder has been carried out by employing techniques such as transmission electron microscopy, X-ray diffraction, and Brunauer–Emmett–Teller surface area analysis. The chemical structural analysis to evaluate the surface properties was made by using X-ray photoelectron spectroscopy. Zeta potential analysis was performed to evaluate the colloidal stability of the particles. Antimicrobial studies were performed for all the compositions using four bacterial strains and an opportunistic human fungal pathogen Macrophomina phaseolina. It was found that the nanoproduct with high strontium content (15 wt% of strontium) showed pronounced antibacterial potential against M. luteus while it completely arrested the fungal growth after 48 h by all of its concentrations. Thus the synthesis strategy described herein facilitated the rapid production of nanosized Sr-substituted CaPs with excellent biological performance suitable for a bone replacement application. [ABSTRACT FROM AUTHOR]

Background: Calcium phosphate-based systems have been introduced as promising bio-mimetic materials due to their close resemblance to the enamel. Chitosan and its derivatives have been an emerging biomaterial due to their additional antibacterial effect and promising re-mineralizing ability. Aim: The aim of this study is to evaluate the effect of chitosan nanoparticles on the remineralization of the demineralized enamel surface after being added to nano-hydroxyapatite and nano-calcium phosphate materials. Setting and Design: This was in vitro study. Materials and Methods: Twenty specimens of extracted permanent molars were collected, and then immersed in demineralizing solution, then distributed into four groups according to the remineralizing material. Group 1: Treated with Nano-beta-tricalcium phosphate (Nβ-TCP) gel, Group 2: Treated with Nβ-TCP with chitosan gel, Group 3: Treated with Nanohydroxyapatite (NHA) gel, and Group 4: Treated with NHA with chitosan gel. The surface hardness of the teeth was measured at baseline, after demineralization, and after remineralization. The structural changes in each group were analyzed using the scanning electron microscopy. Statistical Analysis: Shapiro–Wilk's test, one-way ANOVA followed by Tukey's post hoc test was used. Results: In all groups, there was a significant difference in mean Vickers hardness number (VHN) at different intervals, with the highest value found after treatment (301.64–395.65) VHN, followed by the baseline (236.97–276.15) VHN, while the lowest value was detected after demineralization (121.23–124.39) VHN. It was also indicated that baseline treatment, the Hardness percentage change (%) of the nano NHA + Chitosan group showed the highest significant value (55.10%), while the Nβ-TCP group exhibited the lowest significant value (9.56%). Conclusions: It can be concluded that NHA and NB-TCP modified by chitosan NPs as remineralizing agents of enamel surface hold promising results. [ABSTRACT FROM AUTHOR]

Calcium phosphate (CaP) biomaterials are amongst the most widely used synthetic bone graft substitutes, owing to their chemical similarities to the mineral part of bone matrix and off-the-shelf availability. However, their ability to regenerate bone in critical-sized bone defects has remained inferior to the gold standard autologous bone. Hence, there is a need for methods that can be employed to efficiently produce CaPs with different properties, enabling the screening and consequent fine-tuning of the properties of CaPs towards effective bone regeneration. To this end, we propose the use of droplet microfluidics for rapid production of a variety of CaP microparticles. Particularly, this study aims to optimize the steps of a droplet microfluidic-based production process, including droplet generation, in-droplet CaP synthesis, purification and sintering, in order to obtain a library of CaP microparticles with fine-tuned properties. The results showed that size-controlled, monodisperse water-in-oil microdroplets containing calcium- and phosphate-rich solutions can be produced using a flow-focusing droplet-generator microfluidic chip. We optimized synthesis protocols based on in-droplet mineralization to obtain a range of CaP microparticles without and with inorganic additives. This was achieved by adjusting synthesis parameters, such as precursor concentration, pH value, and aging time, and applying heat treatment. In addition, our results indicated that the synthesis and fabrication parameters of CaPs in this method can alter the microstructure and the degradation behavior of CaPs. Overall, the results highlight the potential of the droplet microfluidic platform for engineering CaP microparticle biomaterials with fine-tuned properties.

With respect to other fields, bone tissue engineering has significantly expanded in recent years, leading not only to relevant advances in biomedical applications but also to innovative perspectives. Polycaprolactone (PCL), produced in the beginning of the 1930s, is a biocompatible and biodegradable polymer. Due to its mechanical and physicochemical features, as well as being easily shapeable, PCL-based constructs can be produced with different shapes and degradation kinetics. Moreover, due to various development processes, PCL can be made as 3D scaffolds or fibres for bone tissue regeneration applications. This outstanding biopolymer is versatile because it can be modified by adding agents with antimicrobial properties, not only antibiotics/antifungals, but also metal ions or natural compounds. In addition, to ameliorate its osteoproliferative features, it can be blended with calcium phosphates. This review is an overview of the current state of our recent investigation into PCL modifications designed to impair microbial adhesive capability and, in parallel, to allow eukaryotic cell viability and integration, in comparison with previous reviews and excellent research papers. Our recent results demonstrated that the developed 3D constructs had a high interconnected porosity, and the addition of biphasic calcium phosphate improved human cell attachment and proliferation. The incorporation of alternative antimicrobials—for instance, silver and essential oils—at tuneable concentrations counteracted microbial growth and biofilm formation, without affecting eukaryotic cells’ viability. Notably, this challenging research area needs the multidisciplinary work of material scientists, biologists, and orthopaedic surgeons to determine the most suitable modifications on biomaterials to design favourable 3D scaffolds based on PCL for the targeted healing of damaged bone tissue.

This study investigates the profound impact of the ZrO2 inclusion volume on the characteristics of Al2O3/ZrO2 nanocomposites, particularly influencing the formation of calcium phosphates on the surface. This research, aimed at advancing tissue engineering, prepared nanocomposites with 5, 10, and 15 vol% ZrO2, subjecting them to chemical surface treatment for enhanced calcium phosphate deposition sites. Biomimetic coating with Sr-enriched simulated body fluid (SBF) further enhanced the bioactivity of nanocomposites. While the ZrO2 concentration heightened the oxygen availability on nanocomposite surfaces, the quantity of Sr-containing phosphate was comparatively less influenced than the formation of calcium phosphate phases. Notably, the coated nanocomposites exhibited a high cell viability and no toxicity, signifying their potential in bone tissue engineering. Overall, these findings contribute to the development of regenerative biomaterials, holding promise for enhancing bone regeneration therapies.

The aim of this study is to investigate the influence of cross-linking and reinforcements in gelatin on the physico-mechanical properties of obtained composites. The gelatin-based composites cross-linked with citric acid (CA) were prepared: gelatin type B (GB) and β-tricalcium phosphate (β-TCP) and novel hybrid composite GB with β-TCP and hydroxyapatite (HAp) particles, and their structure, thermal, and mechanical properties were compared with pure gelatin B samples. FTIR analysis revealed that no chemical interaction between the reinforcements and gelatin matrix was established during the processing of hybrid composites by the solution casting method, proving the particles had no influence on GB cross-linking. The morphological investigation of hybrid composites revealed that cross-linking with CA improved the dispersion of particles, which further led to an increase in mechanical performance. The microindentation test showed that the hardness value was increased by up to 449%, which shows the high potential of β-TCP and HAp particle reinforcement combined with CA as a cross-linking agent. Furthermore, the reduced modulus of elasticity was increased by up to 288%. Results of the MTT assay on L929 cells have revealed that the hybrid composite GB-TCP-HA-CA was not cytotoxic. These results showed that GB cross-linked with CA and reinforced with different calcium phosphates presents a valuable novel material with potential applications in dentistry.

Male patients often experience increased bone and muscle loss after traumatic fractures. This study aims to compare the treatment outcomes of male and female patients with large bone defects. A total of 345 trauma patients underwent surgery, with participants divided into two groups: one receiving bone substitute material (BSM) for augmented defects (n = 192) and the other without augmentation (empty defects = ED, n = 153). Outcome parameters were assessed among female (n = 184) and male (n = 161) patients. Descriptive statistics revealed no significant differences between male and female patients. Approximately one-half of the fractures resulted from high-energy trauma (n = 187). The BSM group experienced fewer complications (p = 0.004), including pseudarthrosis (BSM: n = 1, ED: n = 7; p = 0.02). Among female patients over 65, the incidence of pseudarthrosis was lower in the BSM group (p = 0.01), while younger females showed no significant differences (p = 0.4). Radiologically, we observed premature bone healing with subsequent harmonization. Post hoc power analysis demonstrated a power of 0.99. Augmenting bone defects, especially with bone substitute material, may reduce complications, including pseudarthrosis, in female patients. Additionally, this material accelerates bone healing. Further prospective studies are necessary for confirmation. [ABSTRACT FROM AUTHOR]

The current study reports on the fabrication of composite scaffolds based on polycaprolactone (PCL) and cerium (Ce)-containing powders, followed by their characterization from compositional, structural, morphological, optical and biological points of view. First, CeO2, Ce-doped calcium phosphates and Ce-substituted bioglass were synthesized by wet-chemistry methods (precipitation/coprecipitation and sol-gel) and subsequently loaded on PCL fibres processed by electrospinning. The powders were proven to be nanometric or micrometric, while the investigation of their phase composition showed that Ce was present as a dopant within the crystal lattice of the obtained calcium phosphates or as crystalline domains inside the glassy matrix. The best bioactivity was attained in the case of Ce-containing bioglass, while the most pronounced antibacterial effect was visible for Ce-doped calcium phosphates calcined at a lower temperature. The scaffolds were composed of either dimensionally homogeneous fibres or mixtures of fibres with a wide size distribution and beads of different shapes. In most cases, the increase in polymer concentration in the precursor solution ensured the achievement of more ordered fibre mats. The immersion in SBF for 28 days triggered an incipient degradation of PCL, evidenced mostly through cracks and gaps. In terms of biological properties, the composite scaffolds displayed a very good biocompatibility when tested with human osteoblast cells, with a superior response for the samples consisting of the polymer and Ce-doped calcium phosphates. [ABSTRACT FROM AUTHOR]

This paper reports the mechanical properties of graded macroporous β-Ca3(PO4)2-based ceramic materials produced by stereolithographic 3D printing. We demonstrate the feasibility of using photocurable emulsions for the preparation of ceramic materials with porosity above 80% and controlling the pore size distribution. Graded-porosity ceramic materials with tailored pore size are produced using 3D printing of photocurable tricalcium phosphate-based emulsions. We examine the effect of emulsifier content on the average pore size in ceramic scaffolds with tailored architecture and the effects of porosity, average pore size, and 3D architecture on the strength characteristics of the macroporous ceramic materials. [ABSTRACT FROM AUTHOR]

Calcium phosphate materials and materials based on silicon dioxide have been actively studied for more than 50 years due to their high biocompatibility and bioactivity. Hydroxyapatite and tricalcium phosphate are the most known among calcium phosphate materials, and Bioglass 45S5 is the most known material in the Na2O–CaO–SiO2–P2O5 system. Each of these materials has its application limits; however, some of them can be eliminated by obtaining composites based on calcium phosphate and bioglass. In this article, we provide an overview of the role of silicon and its compounds, including Bioglass 45S5, consider calcium phosphate materials, talk about the limits of each material, demonstrate the potential of the composites based on them, and show the other ways of obtaining composite ceramics in the Na2O–CaO–SiO2–P2O5 system. [ABSTRACT FROM AUTHOR]

There is a growing interest in tissue engineering, in which biomaterials play a pivotal role in promoting bone regeneration. Furthermore, smart functionalization can provide biomaterials with the additional role of preventing orthopedic infections. Due to the growing microbial resistance to antimicrobials used to treat those infections, metal ions, such as silver, thanks to their known wide range of bactericidal properties, are believed to be promising additives in developing antibacterial biomaterials. In this work, novel poly(ε-caprolactone) (PCL)-based 3D scaffolds have been designed and developed, where the polymer matrix was modified with both silver (Ag), to supply antibacterial behavior, and calcium phosphates (biphasic calcium phosphate, BCP) particles to impart bioactive/bioresorbable properties. The microstructural analysis showed that constructs were characterized by square-shaped macropores, in line with the morphology and size of the templating salts used as pore formers. Degradation tests demonstrated the important role of calcium phosphates in improving PCL hydrophilicity, leading to a higher degradation degree for BCP/PCL composites compared to the neat polymer after 18 days of soaking. The appearance of an inhibition halo around the silver-functionalized PCL scaffolds for assayed microorganisms and a significant (p < 0.05) decrease in both adherent and planktonic bacteria demonstrate the Ag+ release from the 3D constructs. Furthermore, the PCL scaffolds enriched with the lowest silver percentages did not hamper the viability and proliferation of Saos-2 cells. A synergic combination of antimicrobial, osteoproliferative and biodegradable features provided to 3D scaffolds the required potential for bone tissue engineering, beside anti-microbial properties for reduction in prosthetic joints infections. [ABSTRACT FROM AUTHOR]

Calcium phosphates are materials of wide interest in the medical and agricultural industries. Advanced in the standardization of protocols to obtain them by combustion in solution in a single step is highly desirable. This is particularly so for the alpha-tricalcium phosphate (α-TCP) phase, widely used in the development of bone cement. In this research, citrulline was used as a fuel for the first time in the one-step synthesis of calcium phosphates, and the effect of adding 0–15 g of ammonium nitrate (AN) as an extra oxidizer agent was studied, allowing the temperature of the reaction to increase from 648 to 950°C. The temperature was measured using low-cost equipment with infrared and type-K thermocouple and contrasted with the estimated theoretical values of adiabatic flame temperature. X-ray diffraction analysis showed the formation of a mixture of α-TCP and hydroxyapatite phases at the lowest combustion temperature, corresponding to 0 g of AN. When the amount of AN was increased, the XRD showed that α-TCP was obtained as a metastable phase, while the amount of hydroxyapatite decreased considerably. At higher combustion temperatures, the crystallite size estimated by Scherrer equation, in turn, increased to a value of 51.61 nm. The SEM images showed the presence of necks between particles in the powders that coincide with the estimation of high reaction temperatures. [ABSTRACT FROM AUTHOR]

The paper considers the method of materials of various natures for medical purposes. When determining the physical and mechanical properties of the samples, it was found that with an increase in temperature, the density of the obtained ceramics increases, which is due to a decrease in the number of large pores, which opens up the possibility of using these materials as implants that carry significant mechanical loads during implantation (for example, replacement of the cortical bone of the jaw). It was found for the first time that, in addition to the filler in composite materials, the synthesized FA mixture can be used to create dense ceramics. The samples are represented by TCP and PFC phases, with an increase in the sintering temperature from 900 to 1100°C, the density and strength of the resulting ceramics increase, and the dissolution rate in various media decreases. Thus, the range of use of synthesized materials is expanding. [ABSTRACT FROM AUTHOR]

Pathological calcifications may consist of calcium oxalate (CaOx), hydroxyapatite (HAP), and brushite (BRU). The objective of this study was to evaluate the effect of phytate (inositol hexakisphosphate, InsP6), InsP6 hydrolysates, and individual lower InsPs (InsP5, InsP4, InsP3, and InsP2) on the crystallization of CaOx, HAP and BRU in artificial urine. All of the lower InsPs seem to inhibit the crystallization of calcium salts in biological fluids, although our in vitro results showed that InsP6 and InsP5 were stronger inhibitors of CaOx crystallization, and InsP5 and InsP4 were stronger inhibitors of BRU crystallization. For the specific in vitro experimental conditions we examined, the InsPs had very weak effects on HAP crystallization, although it is likely that a different mechanism is responsible for HAP crystallization in vivo. For example, calciprotein particles seem to have an important role in the formation of cardiovascular calcifications in vivo. The experimental conditions that we examined partially reproduced the in vivo conditions of CaOx and BRU crystallization, but not the in vivo conditions of HAP crystallization. [ABSTRACT FROM AUTHOR]

Bovine bone is a natural resource having valuable calcium phosphate compounds as a potential bioceramics powder feedstock. This study manipulated the calcium phosphates via hydrothermal processes after calcium phosphatecontaining bone was calcined and extracted. Here the resulting powder precursors obtained after calcining at 900 °C for 5 hours were hydrothermally processed for varying times at 110°C (1-5 h), yielding mainly biphasic calcium phosphates (β-tricalcium phosphate and hydroxyapatite) formation with a minute lime according to XRD analysis. Calcination and hydrothermal processing can effectively produce a high amount of hydroxyapatite proportion (> 99 wt.%) with nano crystallite sizes (30-50 nm). After 5-hour calcination, the SEM images revealed the powder product with size uniformity (1 µm) and plate-like morphology. The powdered bovine bone was then subjected to DTA, DTG, and TG analyses to determine its thermal behavior. Calcination temperatures from 300 to 600 OC removed organic compounds and other impurities from powder matrices. Instead, the calcination of bovine bone at temperatures from 800 to 1000 OC supported the result of the stabilized microstructure of calcium-phosphate-bearing minerals, which would make valuable powder feedstock for hydrothermal synthesis. Results of the study demonstrated that simple calcination and subsequent hydrothermal processing of bovine bone providing major hydroxyapatite and minor β-tricalcium phosphate would get a depth insight into calcium phosphate resource recovery and recycling. [ABSTRACT FROM AUTHOR]