Synthesis of Chitosan and Ferric-Ion (Fe3+)-Doped Brushite Mineral Cancellous Bone Scaffolds.

Biodegradable scaffolds are needed to repair bone defects. To promote the resorption of scaffolds, a large surface area is required to encourage neo-osteogenesis. Herein, we describe the synthesis and freeze-drying methodologies of ferric-ion (Fe3+) doped Dicalcium Phosphate Dihydrate mineral (DCPD), also known as brushite, which has been known to favour the in situ condition for osteogenesis. In this investigation, the role of chitosan during the synthesis of DCPD was explored to enhance the antimicrobial, scaffold pore distribution, and mechanical properties post freeze-drying. During the synthesis of DCPD, the calcium nitrate solution was hydrolysed with a predetermined stoichiometric concentration of ammonium phosphate. During the hydrolysis reaction, 10 (mol)% iron (Fe3+) nitrate (Fe(NO3)3) was incorporated, and the DCPD minerals were precipitated (Fe3+-DCPD). Chitosan stir-mixed with Fe3+-DCPD minerals was freeze-dried to create scaffolds. The structural, microstructural, and mechanical properties of freeze-dried materials were characterized.

Biological and Mechanical Performance of Dual-Setting Brushite-Silica Gel Cements.

Bone defects resulting from trauma, diseases, or surgical procedures pose significant challenges in the field of oral and maxillofacial surgery. The development of effective bone substitute materials that promote bone healing and regeneration is crucial for successful clinical outcomes. Calcium phosphate cements (CPCs) have emerged as promising candidates for bone replacement due to their biocompatibility, bioactivity, and ability to integrate with host tissues. However, there is a continuous demand for further improvements in the mechanical properties, biodegradability, and bioactivity of these materials. Dual setting of cements is one way to improve the performance of CPCs. Therefore, silicate matrices can be incorporated in these cements. Silicate-based materials have shown great potential in various biomedical applications, including tissue engineering and drug delivery systems. In the context of bone regeneration, silicate matrices offer unique advantages such as improved mechanical stability, controlled release of bioactive ions, and enhanced cellular responses. Comprehensive assessments of both the material properties and biological responses of our samples were conducted. Cytocompatibility was assessed through in vitro testing using osteoblastic (MG-63) and osteoclastic (RAW 264.7) cell lines. Cell activity on the surfaces was quantified, and scanning electron microscopy (SEM) was employed to capture images of the RAW cells. In our study, incorporation of tetraethyl orthosilicate (TEOS) in dual-curing cements significantly enhanced physical properties, attributed to increased crosslinking density and reduced pore size. Higher alkoxysilyl group concentration improved biocompatibility by facilitating greater crosslinking. Additionally, our findings suggest citrate's potential as an alternative retarder due to its positive interaction with the silicate matrix, offering insights for future dental material research. This paper aims to provide an overview of the importance of silicate matrices as modifiers for calcium phosphate cements, focusing on their impact on the mechanical properties, setting behaviour, and biocompatibility of the resulting composites.

Performance of brushite plaster as kidney stone phantoms for laser lithotripsy.

Artificial phantoms used in photothermal near-infrared laser lithotripsy research generally fail to mimic both the chemical and the physical properties of human stones. Though high-energy, 1 J pulses are capable of fracturing hard human stones into several large fragments along natural boundaries, similar behavior has not been observed in commonly used gypsum plasters like BegoStone. We developed a new brushite-based plaster formulation composed of ≈90% brushite that undergoes rapid fracture in the manner of human stones under fragmentation pulse regimes. Single-pulse (1 J) ablation crater volumes for phantoms were not significantly different from those of pure brushite stones. Control over crater volumes was demonstrated by varying phosphorous acid concentration in the plaster formulation. Fragmentation of cylindrical brushite phantoms was filmed using a high-speed camera which demonstrated rapid fragmentation in < 100 µs during the bubble expansion phase of a short pulse from a high-powered Ho:YAG laser (Lumenis Pulse 120 H). The rapid nature of observed fracture suggests increasing laser pulse energy by increasing laser pulse duration will not improve fragmentation performance of laser lithotripters. Brushite plaster phantoms are a superior alternative to gypsum plasters for laser lithotripsy research due to their better mimicry of stone composition, controllable single-pulse crater volumes, and fragmentation behavior.

Physiologically engineered porous titanium/brushite scaffolds for critical-size bone defects: A design and manufacturing study.

Repairing critical-size bone defects still represents a critical clinical challenge in the field of trauma surgery. This study focuses on a physiological design and manufacturing of porous composite scaffold (titanium Ti with 10 % mole iron doped brushite DCPD-Fe3+) which can mimic the biomechanical properties of natural cortical bone, specifically for the purpose of repairing critical-size defects. To achieve this, the principle of design of experiments (DOE) was applied for investigating the impact of sintering temperature, mineral ratio, and volume fraction of porosity on the mechanical properties of the fabricated scaffolds. The fabricated scaffolds had open porosity up to 60 %, with pore size approximately between 100 µm and 850 µm. The stiffness of the porous composite scaffolds varied between 3.30 GPa and 20.50 GPa, while the compressive strength ranged from approximately 130 MPa-165 MPa at sintering temperatures equal to or exceeding 1000 °C. Scaffolds with higher porosity and mineral content demonstrated lower stiffness values, resembling natural bone. Numerical simulation was employed by Ansys Workbench to investigate the stress and strain distribution of a critical size defect in mid-shaft femur which was designed to be replaced with the fabricated scaffold. The fabricated scaffolds showed flexible biomechanical behaviour at the bone/scaffold interface, generating lower stress levels and indicating a better match with the femoral shaft stiffness. The experimental and numerical findings demonstrated promising applications for manufacturing a patient-specific bone scaffold for critical and potentially large defects for reducing stress shielding and minimizing non-union risk.

Preparation and Characterization of Mono- and Biphasic Ca1-xAgxHPO4·nH2O Compounds for Biomedical Applications.

This study aimed to explore the effects of the full-scale replacement (up to 100%) of Ca2+ ions with Ag1+ ions in the structure of brushite (CaHPO4·2H2O). This substitution has potential benefits for producing monophasic and biphasic Ca1-xAgxHPO4·nH2O compounds. To prepare the starting solutions, (NH4)2HPO4, Ca(NO3)2·4H2O, and AgNO3 at different concentrations were used. The results showed that when the Ag/Ca molar ratio was below 0.25, partial substitution of Ca with Ag reduced the size of the unit cell of brushite. As the Ag/Ca molar ratio increased to 4, a compound with both monoclinic CaHPO4·2H2O and cubic nanostructured Ag3PO4 phases formed. There was a nearly linear relationship between the Ag ion ratio in the starting solutions and the wt% precipitation of the Ag3PO4 phase in the resulting compound. Moreover, when the Ag/Ca molar ratio exceeded 4, a single-phase Ag3PO4 compound formed. Hence, adjusting the Ag/Ca ratio in the starting solution allows the production of biomaterials with customized properties. In summary, this study introduces a novel synthesis method for the mono- and biphasic Ca1-xAgxHPO4·nH2O compounds brushite and silver phosphate. The preparation of these phases in a one-pot synthesis with controlled phase composition resulted in the enhancement of existing bone cement formulations by allowing better mixing of the starting ingredients.

Risk Profile of Patients with Brushite Stone Disease and the Impact of Diet.

This study examined the profile of patients and the impact of diet on the risk of brushite stone formation under controlled, standardized conditions. Sixty-five patients with brushite nephrolithiasis were enrolled in the study. Metabolic, dietary, and 24 h urinary parameters were collected under the habitual, self-selected diet of the patients and the balanced mixed, standardized diet. The [13C2]oxalate absorption, ammonium chloride, and calcium loading tests were conducted. All patients had at least one abnormality on the usual diet, with hypercalciuria (84.6%), increased urine pH (61.5%), and hyperphosphaturia (43.1%) being the most common. Absorptive hypercalciuria was present in 32.1% and hyperabsorption of oxalate in 41.2%, while distal renal tubular acidosis (dRTA) was noted in 50% of brushite stone formers. The relative supersaturation of brushite did not differ between patients with and without dRTA. Among all recent brushite-containing calculi, 61.5% were mixed with calcium oxalate and/or carbonate apatite. The relative supersaturation of brushite, apatite, and calcium oxalate decreased significantly under the balanced diet, mainly due to the significant decline in urinary calcium, phosphate, and oxalate excretion. Dietary intervention was shown to be effective and should be an integral part of the treatment of brushite stone disease. Further research on the role of dRTA in brushite stone formation is needed.

The Effect of Full-Scale Exchange of Ca2+ with Zn2+ Ions on the Crystal Structure of Brushite and Its Phase Composition.

This study was carried out to investigate the effect of a complete exchange of Ca2+ with Zn2+ ions on the structure of brushite (CaHPO4·2H2O), which might be advantageous in the production process of CaxZn1-xHPO4·nH2O. To acquire the starting solutions needed for the current study, (NH4)2HPO4, Ca(NO3)2·4H2O, and Zn(NO3)2·6H2O were utilized in several molar concentrations. The findings indicate that Ca is partly substituted by Zn when the Zn/Ca molar ratio is below 0.25 and that Zn doping hinders the crystallization of brushite. A continued increase in the Zn/Ca molar ratio to 1 (at which point the supersaturation of the Zn solution rises) led to a biphasic compound of monoclinic brushite and parascholzite precipitate. Elevating the Zn/Ca molar ratio to 1.5 resulted in a precipitate of a parascholzite-like mineral. Finally, increasing the Zn/Ca molar ratio to 4 and above resulted in the formation of the hopeite mineral. Future biomaterial production with specific and bespoke characteristics can be achieved by adjusting the Zn/Ca ratio in the starting solution. It Rhas been established that the Zn/Ca ratio in the starting solution can be adjusted to obtain minerals with specific compositions. Thus, new synthesis methods for parascholzite and hopeite were introduced for the first time in this manuscript.

Efficient low-concentration phosphate removal from sub-healthy surface water by adsorbent prepared based on functional complementary strategy.

The remediation of low-concentration phosphorus polluted surface water (LP-SW) is one of most challenging environmental issues worldwide. Adsorption is more suitable for LP-SW remediation due to its low cost and operability. Based on the strategy of functional complementation among industrial solid wastes (ISWs), ISW-based phosphate absorbent material (PAM) was prepared from coal ash (CA, binder), rich­calcium (Ca) carbide slag (CS, active component) and iron salt (functional reagent) by optimizing materials ratios and roasting conditions. PAM prepared under optimal conditions (Fe/CC-2opt) had good phosphate adsorption efficiency. Notably, Fe/CC-2opt not only ensured that the effluent met Environmental Quality Standards for Surface Water (pH = 6.0-9.0), but also facilitated the formation of brushite instead of hydroxyapatite due to FeSO4 addition. Compared with hydroxyapatite, brushite had greater potential application value as fertilizer due to its solubility and high P/Ca ratio. The possible mechanisms of phosphate adsorption by PAM included surface precipitation, surface complexation, electrostatic adsorption and release of Ca2+/OH-. Preparation cost of PAM was 80 US$/ton, and treatment cost was 0.07 US$/g P. Regeneration efficiency of PAM was still above 80 % after five cycles. The design idea and result of this study provide theoretical basis and technical support for the preparation of PAM with low cost, commercial production and great adsorption capacity.

Fiber support prevents colloid-facilitated contamination induced by dissolution-precipitation of a calcium phosphate adsorbent.

During the adsorptive removal of hazardous metal contaminants, dissolution-precipitation of sparingly soluble adsorbents may result in the formation of toxic colloidal suspensions, triggering secondary pollution. Therefore, we studied the prevention of colloid-facilitated contamination in a model adsorption system of dicalcium phosphate dihydrate (DCPD, CaHPO4·2H2O) and Cd2+ as an adsorbent and adsorbate. Upon adding pure DCPD powder into a 500 mg L-1 Cd2+ solution of pH â‰Œ 7.0, aggregates of spheroidal Cd-bearing primary particles, within 0.040-0.95 µm size range, were generated via dissolution-precipitation. The accumulated volume of these submicron particles (10.8%) was greater than that of the submicron particles from the exposure of DCPD to deionized water (4.48%). While the Cd-carrying submicron particles, which are responsible for colloidal recontamination, appeared to form via homogeneous nucleation, their formation was suppressed using polyacrylonitrile fibers (PANFs) as supporting substrates. Thus, heterogeneous nucleation on PANFs formed hexagonal columnar microparticles of a new phase, pentacadmium dihydrogen tetrakis (phosphate) tetrahydrate (Cd5H2(PO4)4·4H2O). Together with dissolution-precipitation on the native DCPD, nucleation and growth on the PANFs accelerated the depletion of the dissolved species, reducing the degree of supersaturation along the DCPD-water interface. Although the PANFs decreased the Cd adsorption capacity to 56.7% of that of DCPD, they prevented the formation of small aggregates of Cd-bearing particles. Other sparingly soluble adsorbents can be compounded with PANF to prevent the generation of toxic colloids.

Ionized Jet Deposition of Calcium Phosphates-Based Nanocoatings: Tuning Coating Properties and Cell Behavior by Target Composition and Substrate Heating.

Calcium phosphate-based coatings are widely studied in orthopedics and dentistry for their similarity to the mineral component of bone and their capability to promote osseointegration. Different calcium phosphates have tunable properties that result in different behaviors in vitro, but the majority of studies focus only on hydroxyapatite. Here, different calcium phosphate-based nanostructured coatings are obtained by ionized jet deposition, starting with hydroxyapatite, brushite and beta-tricalcium phosphate targets. The properties of the coatings obtained from different precursors are systematically compared by assessing their composition, morphology, physical and mechanical properties, dissolution, and in vitro behavior. In addition, for the first time, depositions at high temperature are investigated for the further tuning of the coatings mechanical properties and stability. Results show that different phosphates can be deposited with good composition fidelity even if not in a crystalline phase. All coatings are nanostructured and non-cytotoxic and display variable surface roughness and wettability. Upon heating, higher adhesion and hydrophilicity are obtained as well as higher stability, resulting in better cell viability. Interestingly, different phosphates show very different in vitro behavior, with brushite being the most suitable for promoting cell viability and beta-tricalcium phosphate having a higher impact on cell morphology at the early timepoints.

Calcium Phosphate Cements as Carriers of Functional Substances for the Treatment of Bone Tissue.

Interest in calcium phosphate cements as materials for the restoration and treatment of bone tissue defects is still high. Despite commercialization and use in the clinic, the calcium phosphate cements have great potential for development. Existing approaches to the production of calcium phosphate cements as drugs are analyzed. A description of the pathogenesis of the main diseases of bone tissue (trauma, osteomyelitis, osteoporosis and tumor) and effective common treatment strategies are presented in the review. An analysis of the modern understanding of the complex action of the cement matrix and the additives and drugs distributed in it in relation to the successful treatment of bone defects is given. The mechanisms of biological action of functional substances determine the effectiveness of use in certain clinical cases. An important direction of using calcium phosphate cements as a carrier of functional substances is the volumetric incorporation of anti-inflammatory, antitumor, antiresorptive and osteogenic functional substances. The main functionalization requirement for carrier materials is prolonged elution. Various release factors related to the matrix, functional substances and elution conditions are considered in the work. It is shown that cements are a complex system. Changing one of the many initial parameters in a wide range changes the final characteristics of the matrix and, accordingly, the kinetics. The main approaches to the effective functionalization of calcium phosphate cements are considered in the review.

Clindamycin-Loaded Nanosized Calcium Phosphates Powders as a Carrier of Active Substances.

Bioactive calcium phosphate ceramics (CaPs) are one of the building components of the inorganic part of bones. Synthetic CaPs are frequently used as materials for filling bone defects in the form of pastes or composites; however, their porous structure allows modification with active substances and, thus, subsequent use as a drug carrier for the controlled release of active substances. In this study, four different ceramic powders were compared: commercial hydroxyapatite (HA), TCP, brushite, as well as HA obtained by wet precipitation methods. The ceramic powders were subjected to physicochemical analysis, including FTIR, XRD, and determination of Ca/P molar ratio or porosity. These techniques confirmed that the materials were phase-pure, and the molar ratios of calcium and phosphorus elements were in accordance with the literature. This confirmed the validity of the selected synthesis methods. CaPs were then modified with the antibiotic clindamycin. Drug release was determined on HPLC, and antimicrobial properties were tested against Staphylococcus aureus. The specific surface area of the ceramic has been demonstrated to be a factor in drug release efficiency.

Antibacterial Composite Material Based on Polyhydroxybutyrate and Zn-Doped Brushite Cement.

A composite material based on electrospinning printed polyhydroxybutyrate fibers impregnated with brushite cement containing Zn substitution was developed for bone implant applications. Powder X-ray Diffraction (PXRD), Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy were applied for materials characterization. Soaking the composite in Ringer's solution led to the transformation of brushite into apatite phase, accompanied by the morphology changes of the material. The bending strength of the composite material was measured to be 3.1 ± 0.5 MPa. NCTC mouse fibroblast cells were used to demonstrate by means of the MTT test that the developed material was not cytotoxic. The behavior of the human dental pulp stem cells on the surface of the composite material investigated by the direct contact method was similar to the control. It was found that the developed Zn containing composite material possessed antibacterial properties, as testified by microbiology investigations against bacteria strains of Escherichia coli and Staphylococcus aureus. Thus, the developed composite material is promising for the treatment of damaged tissues with bacterial infection complications.

Effect of L-Glutamic Acid on the Composition and Morphology of Nanostructured Calcium Phosphate as Biomaterial.

Calcium phosphate (CaP) with several chemical compositions and morphologies was prepared by precipitation using aqueous solutions of L-Glutamic acid (H2G) and calcium hydroxide, both mixed together with an aqueous solution (0.15 M) of phosphoric acid. Plate-shaped dicalcium phosphate dihydrate (brushite) particles were obtained and identified at a lower concentration of the solution of the reactants. The Ca/P ratio deduced by EDS was ~1, as expected. The nanoscale dimension of carbonate apatite and amorphous calcium phosphate, with variable Ca/P ratios, were revealed by X-ray diffraction (XRD) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). They were characterized in medium and high concentrations of calcium hydroxide (0.15 M and 0.20 M). The equilibria involved in all the reactions in aqueous solution were determined. The thermodynamic calculations showed a decrease in the amount of chelate complexes with an increase in pH, being the opposite of [CaPO4-] and [CaHG+]. This fluctuation showed an evident influence on the morphology and polymorphism of CaP particles obtained under the present experimental conditions, with potential use as a biomaterial.

The fate of Cd during the replacement of Cd-bearing calcite by calcium phosphate minerals.

Carbonate-bound speciation is a critical sink of potentially toxic elements (PTEs) like cadmium (Cd) in soil and sediment. In a phosphate-rich environment, carbonate minerals could be replaced by phosphate minerals such as dicalcium phosphate dihydrate (DCPD, also known as brushite), octacalcium phosphate (OCP), and hydroxylapatite (HAP). Currently, it is unclear the migration and fate of PTEs during the replacement of PTEs-bearing carbonates by HAP and related intermediate minerals. Therefore, we synthesized Cd-bearing calcite by the coprecipitation method and converted it to DCPD, OCP, and HAP to investigate the redistribution and fate of Cd. The results showed that Cd incorporation in calcite significantly inhibited their replacement by DCPD and OCP, respectively. 1.26% of Cd in calcite was released into the solution when DCPD replaced calcite, and subsequently, most of the released Cd was recaptured by OCP. Significantly, the released Cd was below 0.05‰ when all the solid converted to HAP. These results suggested that with the application of phosphate fertilizer in alkaline soil, the secondary calcium phosphate minerals could control the environmental behavior of Cd.

Development and evaluation of local regenerative biomimetic bone-extracellular matrix scaffold loaded with nano-formulated quercetin for orthopedic fractures.

The prevalence of bone injuries is greatly increasing each year and the proper healing of fractures without any complications is very challenging. Self-setting calcium phosphate cements (CPCs) have attracted great attention as bioactive synthetic bone substitutes. Quercetin (QT) is a multipurposed drug with reported bone-conserving properties. The loading of QT and QT-phospholipid complex within nanostructured lipid carriers (NLC) was proposed to overcome the poor physical properties of the drug and to introduce the use of bioactive excipients as phospholipids and olive oil. The aim of this work was to formulate a regenerative scaffold loaded with nano-formulated QT for local treatment of orthopedic fractures. For the first time, scaffolds composed of brushite CPC were prepared and loaded with quercetin lipid nano-systems. In vitro tests proved that the addition of lipid nano-systems did not deteriorate the properties of CPC where QT-NLC/CPC showed an adequate setting time, appropriate compressive strength, and porosity. The scanning electron microscope confirmed maintenance of nanoparticles integrity within the cement. Using a rat femur bone defect animal model, the histological results showed that the QT-NLC/CPC had a superior bone healing potential compared to crude unformulated QT/CPC. In conclusion, QT-NLC /CPC are promising lipid nano-composite materials that could enhance bone regeneration.

In vivo biocompatibility of SrO and MgO doped brushite cements.

The addition of dopants in biomaterials has emerged as a critical regulator of bone formation and regeneration due to their imminent role in the biological process. The present work evaluated the role of strontium (Sr) and magnesium (Mg) dopants in brushite cement (BrC) on in vivo bone healing performance in a rabbit model. Pure, 1 wt% SrO (Sr-BrC), 1 wt% MgO (Mg-BrC), and a binary composition of 1.0 wt% SrO + 1.0 wt% MgO (Sr + Mg-BrC) BrCs were implanted into critical-sized tibial defects in rabbits for up to 4 months. The in vivo bone healing of three doped and pure BrC samples was examined and compared using sequential radiological examination, histological evaluations, and fluorochrome labeling studies. The results indicated excellent osseous tissue formation for Sr-BrC and Sr + Mg-BrC and moderate bone regeneration for Mg-BrC compared to pure BrC. Our findings indicated that adding small amounts of SrO, MgO, and binary dopants to the BrC can significantly influence new bone formation for bone tissue engineering.

Hybrid Polymer-Inorganic Materials with Hyaluronic Acid as Controlled Antibiotic Release Systems.

In recent years, significant developments have taken place in scientific fields such as tissue and materials engineering, which allow for the development of new, intelligent biomaterials. An example of such biomaterials is drug delivery systems that release the active substance directly at the site where the therapeutic effect is required. In this research, polymeric materials and ceramic-polymer composites were developed as carriers for the antibiotic clindamycin. The preparation and characterization of biomaterials based on hyaluronic acid, collagen, and nano brushite obtained using the photocrosslinking technique under UV (ultraviolet) light are described. Physical and chemical analyses of the materials obtained were carried out using Fourier transform infrared spectroscopy (FT-IR) and optical microscopy. The sorption capacities were determined and subjected to in vitro incubation in simulated biological environments such as Ringer's solution, simulated body fluid (SBF), phosphate-buffered saline (PBS), and distilled water. The antibiotic release rate was also measured. The study confirmed higher swelling capacity for materials with no addition of a ceramic phase, thus it can be concluded that brushite inhibits the penetration of the liquid medium into the interior of the samples, leading to faster absorption of the liquid medium. In addition, incubation tests confirmed preliminary biocompatibility. No drastic changes in pH values were observed, which suggests that the materials are stable under these conditions. The release rate of the antibiotic from the biomaterial into the incubation medium was determined using high-pressure liquid chromatography (HPLC). The concentration of the antibiotic in the incubation fluid increased steadily following a 14-day incubation in PBS, indicating continuous antibiotic release. Based on the results, it can be concluded that the developed polymeric material demonstrates potential for use as a carrier for the active substance.

Fabrication and mechanical properties of newly developed triphasic blocks composed of gypsum-brushite-monetite for bone graft applications.

Objective: A triphasic bone graft block composed of gypsum, brushite, and monetite is expected to be better for regenerating bone than a gypsum-hydroxyapatite-tricalcium phosphate block. Therefore, the aim of this study was to fabricate and evaluate the mechanical properties of a newly developed triphasic block composed of gypsum, brushite, and monetite. Materials and method: Triphasic blocks were prepared by mixing calcium sulfate hemihydrate, brushite, and monetite powders with distilled water at a powder-to-liquid ratio of 0.5. The content of calcium sulfate hemihydrate was fixed at 50%, and the contents of brushite and monetite powders were varied. After molding and setting, the obtained blocks were characterized, and their mechanical properties were evaluated. Results: The triphasic blocks were prepared and could maintain their shape without collapsing. The XRD characterization of the obtained triphasic blocks showed that only three phases existed in the block. Calcium sulfate hemihydrate was transformed into its dihydrate form and provided mechanical strength to the block through a setting mechanism. The transformation of calcium sulfate hemihydrate into its dihydrate crystals formed an interlocked structure that was disrupted in triphasic blocks, as observed in SEM images. The disruption of the interlocked structure resulted in lower mechanical strength of the obtained triphasic blocks compared to the set gypsum control. The variation in brushite and monetite composition did not affect the mechanical properties of the triphasic blocks. Conclusion: The triphasic gypsum-brushite-monetite block was successfully prepared, and no other crystal phases were found. The triphasic blocks could maintain their shape after setting. The addition of brushite and monetite powders disrupted the interlocked structure of the set gypsum crystal, resulting in a decrease in mechanical strength. Furthermore, the variation in brushite and monetite powders did not affect the mechanical properties of the triphasic blocks.

Brushite nanoparticles based electrochemical sensor for detection of uric acid, xanthine, hypoxanthine and caffeine.

The research in the field of biosensors has recently been focused on the design and development of functional electrode materials that can respond to changes in their biochemical environment. Here, we report the synthesis of dicalcium phosphate dihydrate (DCPD), also known as brushite (CaHPO4·2H2O) by soft chemical method and its application for electrochemical sensing of four different analytes. Phase purity, structure, chemical composition and surface morphology of the synthesized nanoparticles have been investigated using powder XRD, FTIR, SEM, XPS and HRTEM methods. Electrochemical sensor was prepared by modifying GCE with brushite and the modified electrodes were successfully used for either independent or simultaneous determination of uric acid, xanthine, hypoxanthine and caffeine in their mixture. The brushite/GCE exhibited four strong well-defined separate peaks corresponding to the oxidation of UA, XN, HXN and CF in phosphate buffer saline (PBS) at pH 7.4. The fabricated electrode showed low detection limits (S/N = 3) of 0.576, 1.0, 0.076 and 1.26 µM for UA, XN, HXN and CF respectively. Practical application of the fabricated electrode has been demonstrated by determining UA, XN, HXN and CF in human urine and coffee samples by direct method. The brushite offers scope for fabrication of sensor systems for implantable medical applications.