Growth Of Calcium Phosphate Research Articles

Crystallization of smooth amorphous calcium phosphate microspheres to core-shell hydroxyapatite microspheres.

Calcium phosphates (Ca-P) represent a significant class of biological minerals found in natural hard tissues. Crystallization through phase transformation of a metastable precursor is an effective strategy to guide the growth of crystalline Ca-P with exceptional functionality. Despite extensive research on Ca-P, the exact process during the crystallization of amorphous particles to hydroxyapatite (HA) remains elusive. Herein, pure HA microspheres with a core-shell structure are crystallized via dissolution and re-crystallization of smooth amorphous calcium phosphate (ACP) microspheres. The transformation is initiated with the increase of the hydrothermal treatment time in the presence of sodium trimetaphosphate and l-glutamic. The underlying mechanisms along with the kinetics of such transformation are explored. Nanocrystalline areas are formed on the smooth ACP microspheres and crystallization advances via nanometre-sized clusters formed by directional arrangement of nanocrystalline whiskers. Our findings shed light on a crucial but unclear stage in the genesis of HA crystals, specifically under the conditions of hydrothermal synthesis.

Crystallization of Calcium Carbonate and Calcium Phosphate Phases in Silica Hydrogel: Morphological and Compositional Characterization

The present study showcases a series of crystallization experiments using a specially designed double diffusion system to grow crystals belonging to the calcium carbonate–phosphate system. The experimental U-shaped device comprised two vertical solution containers, separated by a horizontal column of silica hydrogel. Each container was filled with 0.5 M CaCl2 and 0.5 M Na2CO3 solutions, which diffused through the gel column over time. Na3PO4 solutions, with 50 and 500 ppm concentrations, were incorporated into the gel in different experiments, resulting in a homogeneous distribution of phosphate concentrations within the diffusion column. After 15- and 30-day incubation periods post-nucleation, the crystals formed in different sections of the gel were carefully extracted and studied with scanning electron microscopy and electron microprobe. Additionally, Raman spectra were collected from the samples using a confocal Raman microscope, providing further insights into their molecular composition and structural properties. The obtained results show that under the induced experimental conditions (i) phosphate incorporates into calcite’s structure, and (ii) the growth of calcium phosphates in the presence of carbonate ions involves the sequential, heterogeneous nucleation of CO3-bearing OCP/HAP-like phases, with Raman spectral characteristics very similar to those of bioapatites.

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

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

The Preparation and Characterization of Chitosan/Calcium Phosphate Composite Microspheres for Biomedical Applications.

In this study, we successfully prepared porous composite microspheres composed of hydroxyapatite (HAp), di-calcium phosphate di-hydrated (DCPD), and chitosan through the hydrothermal method. The chitosan played a crucial role as a chelating agent to facilitate the growth of related calcium phosphates. The synthesized porous composite microspheres exhibit a specific surface area of 38.16 m2/g and a pore volume of 0.24 cm3/g, with the pore size ranging from 4 to 100 nm. Given the unique properties of chitosan and the exceptional porosity of these composite microspheres, they may serve as carriers for pharmaceuticals. After being annealed, the chitosan transforms into a condensed form and the DCPD transforms into Ca2P2O7 at 300 °C. Then, the Ca2P2O7 initially combines with HAp to transform into β tricalcium phosphate (β-TCP) at 500 °C where the chitosan is also completely combusted. Finally, the microspheres are composed of Ca2P2O7, β-TCP, and HAp, also making them suitable for applications such as injectable bone graft materials.

In situ biomimetic mineralization of a paper microfluidic device as a luminescent sensor for nitrite determination

Nucleation and growth of terbium-doped amorphous calcium phosphate (Tb-ACP) on cellulose fibers of a microfluidic paper-based analytical device (μPAD) towards an environmentally friendly design of a sensor for water pollutant.

Effect of microstructure and texture of AZ31 magnesium alloy substrate on nucleation and growth of biomimetic calcium phosphate coating

Magnesium has a special place in biomedical applications due to its biocompatibility and biodegradability properties. The high corrosion rate of magnesium in the body environment requires the use of a biocompatible coating such as calcium phosphate. In this paper, the effect of microstructure and crystalline texture of AZ31 magnesium alloy substrate on the morphology of calcium phosphate coating and the corrosion behavior of the material was investigated. The results imply that apatite crystals can form and grow on the surfaces of the biomimetic coating after soaking in simulated body fluid (SBF). The corrosion behavior of the material was investigated using an electrochemical polarization test in SBF solution for 3 days. The results showed that changes in the microstructure and crystalline texture of the substrate changed the coating morphology so that the growth of calcium phosphate changed from a rod-shaped with a diameter of 100–150 nm to a blade-shaped with a thickness of 20–50 nm. An increase in the corrosion resistance of the coated specimens with the corrosion rate of 0.65 mm/year was obtained compared to the uncoated specimen with the corrosion rate of 2.62 mm/year.

Biomimetic mineral layer over layer-by-layer assemblies: Growth mechanism directed by collagen fibrils

In this study, we describe a promising biomimetic method for growing a hybrid calcium phosphate (CaP) – collagen coating designed following the same principles that govern biomineralization of hard tissues. For this purpose, we explore the versatility of layer-by-layer (LbL) method to incorporate type I collagen and alkaline phosphatase (ALP), while controlling their supramolecular organization and bioactivity. This provides a way to generate in situ CaP ion precursors in the vicinity of collagen proteins, which are self-assembled into fibrils at the solid/liquid interface and further crosslinked. The catalytic properties of ALP, including initial activity and operational stability, is evaluated when the enzymes are embedded within the LbL film. Moreover, a systematic study of the intermediate states of the mineralization is performed by means of atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Results show that the presence of collagen fibrils within the LbL film plays a pivotal role in the growth mechanism of the biomimetic mineral layer. The main findings support that the role of fibrils consists in favoring the adsorption of enzymes and providing a suitable environment for CaP nucleation and growth. Interestingly, early-stage AFM observations reveal the preferential formation of colloidal particles of CaP onto the collagen fibrils, followed by a significant increase of their surface coverage, yielding particles onto and in-between the fibrils. Further mineralization leads to a coating fully covering the support and mainly exhibiting flat and continuous layer covered with a dense network of mineralized collagen fibrils. The approach described in this work provides a straightforward way for the design of biomimetic hybrid coatings with the perspective of tuning cell-material interaction in biomedical applications dealing with hard mineralized tissues.

Enhydra fluctuans Lour. aqueous extract inhibited the growth of calcium phosphate crystals: An in vitro study

Enhydra fluctuans Lour. is consumed by various tribes in their ethnomedicinal practices for the treatment of kidney stones and urinary problems. However, no scientific studies were conducted to evaluate its effect on crystal growth. Hence, the present study proposed to investigate the effect of aqueous extract of whole plant of standardized E. fluctuans (AEEF) on the growth of calcium phosphate (brushite) crystals. Attempts were also made to evaluate the effect of in vitro free radical scavenging and antimicrobial activities of AEEF. In vitro studies indicated that AEEF (50, 100, and 200 µg/mL) exhibited an inhibitory role on brushite crystal growth. The average length of the deposited brushite crystals was decreased by citric acid (1molL−1) and AEEF (200, 100, and 50 µg/mL) till day 8. Results showed that AEEF (200 and 100 µg/mL) and citric acid significantly (P<0.001) decreased the crystal bed as compared to the control on day 8 of the study. AEEF showed an antimicrobial effect against Staphylococcus aureus and exhibited antioxidant activity. In conclusion, the aqueous extract of the whole plant of Enhydra fluctuans was found effective in the inhibition of brushite crystals. Further, in vivo studies along with molecular studies and bioactivity-guided fractionation are required to strengthen its antilithiatic effect along with identifying the bioactive compounds and the mechanism of action involved therein.

Material properties and bioactivity of a resin infiltrant functionalized with polyhedral oligomeric silsesquioxanes.

To investigate the effect of methacrylate polyhedral oligomeric silsesquioxanes (POSS-8) on various material properties and mineral precipitation potential of a resin infiltrant. A TEGDMA-based resin infiltrant was mixed with 0.5, 1, 3, 5 or 10wt% POSS-8 or left unchanged (control). Degree of conversion (DC), water sorption (WS), viscosity, elastic modulus (E-modulus), flexural strength (FS), Knoop microhardness (KHN) and softening ratio (SR) were assessed. Growth of calcium phosphate (Ca/P) precipitates infiltrant-treated bovine enamel and dentin specimens immersed in artificial saliva or artificial dentinal fluid, respectively, for 28 days was analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. For viscosity assessment, pure TEGDMA filled with 0-10wt% POSS-8 was used. Statistical analyses were performed using ANOVA and Tukey's post-hoc tests (p<0.05). POSS-8 did not change the flexural strength, water sorption and softening ratio. The apparent degree of conversion was increased at lower concentrations only while E-modulus remained constant in almost all groups. The particles led to a slight decrease of KHN at concentrations below 3%. The effect on viscosity is comparable to the reinforcement effect. Ca/P precipitates formed on dentin specimens treated with POSS-8-filled infiltrant after 4 weeks of immersion, but were not detected on the control infiltrant. The mineral precipitation on enamel was not improved by POSS-8. POSS-8 particles did not worsen the material properties of the resin infiltrant, while the Ca/P precipitation on dentin was stimulated.

Calcification of Indocyanine Green Laden Dendritic Mesoporous Manganese‐Silicon Nanocomposite for Multiple Oxygen Compensation Enhanced Phototherapy

AbstractIncreasing oxygen (O2) content and down‐regulating the concentration of glutathione (GSH) in tumor microenvironment (TME) by multiple approaches remain critical factors for the promotion of phototherapeutic effect, especially for photodynamic therapy (PDT). Herein, indocyanine green (ICG) laden dendritic mesoporous manganese‐silicon nanocomposite (NC) is designed and subsequently managed with calcification through in situ growth of calcium phosphate (IDMMS@CaP NC). As specific response behavior of the mildly acidic and GSH overexpressed TME, the IDMMS@CaP NC can rapidly collapse when accumulated at the tumor site, liberate Mn2+, Ca2+, and ICG, simultaneously reduce the concentration of GSH. Mn2+ can catalyze endogenous hydrogen peroxide to produce O2. Overloaded Ca2+ induces mitochondrial injury, and reduces cellular metabolism and O2 consumption. The photothermal effect from ICG with 808 nm laser irradiation can not only cause tumor cells necrosis but also accelerate blood flow to further improve the O2 content at the tumor site. Consequently, owing to effective GSH depletion and multiple O2 compensation, the PDT efficiency of ICG can be significantly increased. As proof of concept, the designed multifunctional nanocomposite will provide a general strategy for enhancing the role of phototherapy in cancer therapeutic area.

A tattoo-inspired electrosynthesized polypyrrole film: crossing the line toward a highly adherent film for biomedical implant applications

Polypyrrole (PPy) films have demonstrated promising application for implants due to their unique topographical and electronic properties. However, the limited PPy adhesiveness to metallic surfaces remains a challenge. Consequently, we propose a two-step technique for the surface modification of titanium (Ti) via a plasma electrolytic oxidation (PEO) step to serve as mechanical interlocking for the subsequent deposition of a highly adherent PPy film (PEO + PPy). Ti discs with machined and PEO-modified surfaces were used as controls. For the experimental groups, PPy film was deposited onto such surfaces by electrodeposition. Then, the role of machined and PEO surfaces in the synthesis, conductivity, microstructure, mechanical, electrochemical, microbiological, and biological properties of the PPy film was investigated. The results showed that a highly adherent “tattoo-inspired” PPy thin film was successfully achieved when the Ti surface was pretreated via PEO. PEO + PPy enhanced Ti mechanical and tribological properties by inducing a lower friction coefficient and wear loss due to the cushion effect of PPy film, besides promoting higher corrosion resistance. The “cauliflower-like” morphology of the PPy favored protein adsorption, calcium phosphate growth and demonstrated cell biocompatibility. The association between PEO and PPy film can be considered bioactive and is promising for the triggering of superior long-term stability of biomedical implants.

Embedding Collagen in Multilayers for Enzyme-Assisted Mineralization: A Promising Way to Direct Crystallization in Confinement.

The biogenic calcium phosphate (CaP) crystallization is a process that offers elegant materials design strategies to achieve bioactive and biomechanical challenges. Indeed, many biomimetic approaches have been developed for this process in order to produce mineralized structures with controlled crystallinity and shape. Herein, we propose an advanced biomimetic approach for the design of ordered hybrid mineralized nano-objects with highly anisotropic features. For this purpose, we explore the combination of three key concepts in biomineralization that provide a unique environment to control CaP nucleation and growth: (i) self-assembly and self-organization of biomacromolecules, (ii) enzymatic heterogeneous catalysis, and (iii) mineralization in confinement. We use track-etched templates that display a high density of aligned monodisperse pores so that each nanopore may serve as a miniaturized mineralization bioreactor. We enhance the control of the crystallization in these systems by coassembling type I collagen and enzymes within the nanopores, which allows us to tune the main characteristics of the mineralized nano-objects. Indeed, the synergy between the gradual release of one of the mineral ion precursors by the enzyme and the role of the collagen in the regulation of the mineralization allowed to control their morphology, chemical composition, crystal phase, and mechanical stability. Moreover, we provide clear insight into the prominent role of collagen in the mineralization process in confinement. In the absence of collagen, the fraction of crystalline nano-objects increases to the detriment of amorphous ones when increasing the degree of confinement. By contrast, the presence of collagen-based multilayers disturbs the influence of confinement on the mineralization: platelet-like crystalline hydroxyapatite form, independently of the degree of confinement. This suggests that the incorporation of collagen is an efficient way to supplement the lack of confinement while reinforcing mechanical stability to the highly anisotropic materials. From a bioengineering perspective, this biomineralization-inspired approach opens up new horizons for the design of anisotropic mineralized nano-objects that are highly sought after to develop biomaterials or tend to replicate the complex structure of native mineralized extracellular matrices.

Vapour Diffusion Sitting Drop Method to Induce Nucleation of Calcium Phosphate on Exfoliated Graphene and Graphene Oxide Flakes

The preparation of graphene/apatite and graphene oxide/apatite hybrid nanocomposites has recently attracted great attention in the biomaterial community. The sitting drop vapor diffusion technique has been assessed as a preparative method for such nanocomposites in this work. The technique has been employed to induce heterogeneous nucleation and growth of calcium phosphate in the presence of exfoliated graphene and commercial graphene oxide flakes, both labeled with L-Alanine. Exfoliated multilayered graphene flakes were produced by sonication-assisted liquid-phase exfoliation of graphite. In both composites, the apatite nanocrystals displayed similar size and shape, but different labile and B-type carbonation contributions. Graphene and graphene oxide flakes also influenced the carbonation degree of the apatite, which was almost half that measured for the apatite blank, as well as the aggregation state of their composites. In this regard, those composites with graphene oxide formed larger aggregates because of their wider size distribution, with a high-volume percentage of nanosheets (of about 4 nm length). Overall, the method is very useful to prepare small amounts of nanocomposite with high reproducibility.

New Sustainable Ionic Polysaccharides Fibers Assist Calcium Phosphate Mineralization as Efficient Adsorbents

Polysaccharides containing active sites allow the incorporation of chemical moieties that may improve the adsorption properties of contaminants. The current article describes the bioactivity and adsorption properties of new sustainable ionic fibers prepared from polysaccharides. The TEMPO-oxidized cellulose nanofibers (CNF) and N-guanidinuim chitosan acetate (GC) were prepared from neat cellulose and chitosan, respectively. The prepared ionic fibers, CNF/GC, enhanced the deposition of calcium phosphate (CaP) nanoparticles. The analysis showed that the ionic fibers initiate the growth of calcium phosphate to form a hybrid with high inorganic ratio, 42.6%. The mineralized calcium phosphate showed sponge-like morphology consisting of spherical to flake-like particles. The potential of the prepared materials for removal methylene blue (MB) was calculated. The prepared CNF/GC/CaP exhibited high removal efficiency for MB (531.9 mg/g) compared to CNF/GC which is 384.6 mg/g. Langmuir and pseudo second-order models are the appropriate models for the equilibrium isotherm and kinetic studies. The CNF/GC/CaP hybrid, thus, provides a sustainable adsorbent for dye removal applications.

Influence of adding Pluronic F127 in the electrolyte on the morphology, structure and biofilm adhesion of calcium phosphate coatings

In this work, we have investigated the addition of Pluronic F127 (PF127) into the electrolyte solution on the structure, morphology and antibacterial growth of calcium phosphate (CaP) coatings synthesized by an electrochemical method on Ti substrate. Different parameters of the deposition process were investigated, which were temperature, time and PF127 wt%. The coatings were characterized by X-ray diffraction (XRD), gravimetric analysis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In vitro antimicrobial assays against S. aureus were performed. XRD analysis confirmed the formation of dicalcium phosphate dihydrate (DCPD) or anhydrous dicalcium phosphate (DCPA) and octacalcium phosphate (OCP). The structure and morphology depended mainly on PF127 wt% and deposition temperature in lower deposition time. Interestingly, structure and morphology were not influenced by adding PF127 at higher deposition time using higher PF127 concentrations. The morphology by SEM changed from plate-like to fiber by varying the PF127 concentration as well as blocks at higher temperatures. Moreover, all coatings were crystalline, uniform and crack-free. Antibacterial assays showed that biofilm formation was prevented when a coating of PF127 is deposited on the surface. Bacterial growth depended on the phase and morphology of washed coatings. Thus, the structure, morphology and consequently bacterial growth resistance can be tailored by the use of PF127 in the electrochemical processing at shorter deposition times.

The Influence of Different Classes of Amino Acids on Calcium Phosphates Seeded Growth

Amino acids (AAs) attract attention for elucidating the role of proteins in biomineralization and the preparation of functionalized biomaterials. The influence that AAs exert on calcium phosphate (CaP) mineralization is still not completely understood, as contradictory results have been reported. In this paper, the influence of the addition of different classes of AAs, charged (L-aspartic acid, Asp; L-lysine, Lys), polar (L-asparagine, Asn; L-serine, Ser; L-tyrosine, Tyr), and non-polar (L-phenylalanine, Phe), on CaP growth in the presence of octacalcium phosphate (OCP) and calcium hydrogenphosphate dihydrate (DCPD) seeds was investigated. In control systems (without AAs), a calcium-deficient apatite (CaDHA) layer was formed on the surface of OCP, while a mixture of CaDHA and OCP in the form of spherical aggregates was formed on the surface of DCPD crystals. Charged and non-polar promoted, while polar AAs inhibited CaDHA formation on the OCP seeds. In the case of DCPD, Lys, Asp, and Phe promoted CaP formation, while the influence of other AAs was negligible. The most efficient promotor of precipitation in both cases was non-polar Phe. No significant influence of AAs on the composition and morphology of precipitates was observed. The obtained results are of interest for understanding biomineralization processes and additive controlled material synthesis.

Cellulose/silk fibroin assisted calcium phosphate growth: Novel biocomposite for dye adsorption

Cellulose and silk fibroin were dissolved in 1-Butyl-3-methylimidazolium chloride [Bmim][Cl] and regenerated with ethanol to form homogenous blend of regenerated cellulose/silk fibroin. The bioactivity of regenerated cellulose/silk matrix to assist calcium phosphate mineralization was studied in the current article. Cellulose/silk fibroin/calcium phosphate biocomposite was investigated by different characterization methods such as FT-IR, XRD, TGA, SEM and EDX. The potential of the prepared composite for removal of organic dyes, such as methylene blue (MB), was calculated. The prepared biocomposite exhibited high removal efficiency for MB (172.4 mg/g) compared to regenerated cellulose/silk fibrin blend which is 120.4 mg/g. The kinetic study and the isotherm results for the examined materials followed pseudo second order and Langmuir models, respectively. The regenerated cellulose/silk/calcium phosphate biocomposite, thus providing prospects for further research and application in the remediation of water from dye pollution.

Combinatorial effects of coral addition and plasma treatment on the properties of chitosan/polyethylene oxide nanofibers intended for bone tissue engineering

Given the complex calcified nature of the fibrous bone tissue, a combinatorial approach merging specific topographical/biochemical cues was adopted to design bone tissue-engineered scaffolds. Coral having a Ca-enriched structure was added to electrospun chitosan (CS)/polyethylene oxide (PEO) nanofibers that were subjected to plasma surface modifications using a medium pressure Ar, air or N2 dielectric barrier discharge. Plasma incorporated oxygen- and nitrogen-containing functionalities onto the nanofibers surface thus enhancing their wettability. Plasma treatment enhanced the performance of osteoblasts and the interplay between plasma treatment and coral was shown to boost initial cell adhesion. The fibers capacity to trigger calcium phosphate growth was predicted via immersion in simulated body fluid. Globular carbonate apatite nanocrystals were deposited on plasma-treated CS/PEO NFs while thicker layers of flake-like nanocrystals were covering plasma-treated Coral/CS/PEO fibers without blocking the interfibrous pores. Overall, the exclusive multifaceted plasma-treated Coral/CS/PEO nanofibers are believed to revolutionize the bone tissue engineering field.

Hydroxyapatite (HA)-based hybrid bionanocomposite hydrogels: Ciprofloxacin delivery, release kinetics and antibacterial activity

The current study developed a series of novel biomaterials based on the growth of calcium phosphate (HA) within the polyvinyl alcohol/κ-carrageenan (PVACar) hydrogels to assess their potential as drug delivery system. All synthesized samples were analyzed by using common techniques e.g. Fouriertransform infrared spectroscopy (FT-IR), transmission electronmicroscopy (TEM), scanningelectron microscopy(SEM)with an energy-dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD). Ciprofloxacin (as a drug model) encapsulation efficiency and release performance of the samples were investigated. Experimental results showed that the incorporation of HA led to sustain release of ciprofloxacin, whereas about ~ 70% of ciprofloxacin was diffused from pristine PVACar sample during 30 h. The kinetic investigations showed the best fit with Korsmeyer-Peppas model with Fick's diffusion as the drug release mechanism.Moreover, the performance of ciprofloxacin-loaded hydrogels as antibacterial hydrogels was tested, which showed good antibacterial activity against Gram-positiveStaphylococcus aureus and Gram-negative Escherichia coli bacteria.

Effect of Convection on Crystal Growth of Calcium Phosphate in a Thermostat under Terrestrial and Space Conditions

Mass transfer in the process of crystal growth of octacalcium phosphate Ca8H2(PO4)6 and hydroxyapatite Ca10(OH)2(PO4)6 during mixing aqueous solutions of CaCl2 and KH2PO4 + K2HPO4 in a buffer solution KCl is simulated mathematically with regard to the stoichiometric relationship. The investigations are carried out for the weightlessness, microgravity, and normal gravity conditions. The effect of gravity (convection) on the nature of reaction component transfer in the process of crystal growth of calcium phosphate under the temperature–controlled conditions is considered. It is shown that the reaction component transfer times are less under convection mixing as compared with the purely diffusive regime, but the rate and mass of formation of calcium phosphate depend not only on the convection time and intensity but also on the convection mixing structure.