Calcium Phosphate Formation Research Articles

Evolutionary Loss of Acid-Secreting Stomach and Endoskeletal Ossification: A Phosphorus Perspective

Phosphorus is essential for all life forms on Earth, including eukaryotes (animals, plants, fungi, and protists), prokaryotes (bacteria and archaea), and even viruses. Its significance stems primarily from its presence in nucleic acids (DNA and RNA), where it forms a crucial part of the backbone structure. Beyond this, phosphorus plays a pivotal role in countless biological processes, supporting life at its core. In this article, the author explores the possible causes of stomach loss, focusing specifically on phosphorus absorption, vertebral calcification, and reproduction. Large gonads, characteristic of external fertilization, require substantial amounts of phosphorus for gametogenesis in both females and males, particularly in the latter. This demand has driven the evolutionary calcification of vertebrae, which serve as a phosphorus storage organ. Moreover, to efficiently absorb phosphorus from their diets, shellfish-eating fish have evolved to either lose their stomachs or reduce gastric acidity, minimizing the formation of calcium phosphate precipitates in the intestine.

Insights into Calcium Phosphate Formation Induced by the Dissolution of 45S5 Bioactive Glass.

Although models have been proposed to explain the mechanisms of bioglass (BG) dissolution and subsequent calcium phosphate (CaP) mineralization, open questions remain. The processes in which phase transition occurs in aqueous solutions and their dynamics remain underexplored partly because traditional instruments/techniques do not allow for direct observations at the adequate time and length scales at which such phase transformations occur. For instance, given the crucial role of the silica gel in CaP formation during BG dissolution, uncertainty exists about how such a silica gel forms on the BG surface. In the case of CaP formation driven by BG dissolution, questions can also be added, i.e., how CaP develops into an apatitic-like structure, how many transient phases there are, and, in general, phenomena occurring in the solid-liquid interface during BG dissolution. Several approaches were taken to study CaP mineralization driven by BG dissolution, mainly examining the solid-liquid interface and the BG after-reaction surface. This paper focuses on gaining insight into silica gel formation on the BG's surface during dissolution. Electron microscopy techniques were used, including scanning electron microscopy and focused ion beam cross sections. Other analysis techniques, such as time-of-flight secondary ion mass spectrometry, were utilized. Cross sections of reacted BG-blocks gave essential insights into the BG dissolution, particularly its strong dependency on experimental conditions, and tentative evidence has shown that soluble silica from BG dissolution may not reprecipitate/repolymerize on BG blocks' surface; thus, we wonder where it precipitates. Additionally, complementary analysis techniques determined that CaP, during BG dissolution, transitions from amorphous calcium phosphate to a calcium-deficient nanocrystalline apatitic structure with minimal contents of Si4+ and Na+ ions that may be molecularly part of CaP. The Hench model has been the core guide for BG dissolution and subsequent CaP formation for many years. However, this study shows tentative evidence that contributes to and somewhat differs from it.

Unraveling the role of E. coli and calf intestinal alkaline phosphatase in calcium phosphate synthesis.

The enzyme-catalyzed synthesis of calcium phosphate is a promising method for producing calcium-based nanomaterials for biomedical applications. The purpose of this work was to determine the type of phosphate that forms when alkaline phosphatase catalyzes the reaction, and to identify the role of natural biopolymers in calcium phosphate formation. In this research, we analyzed calcium phosphates that were synthesized in the presence of alkaline phosphatase from either E. coli or calf intestinal, analyzed the obtained nanoparticles and compared them by functional composition, elemental ratio, and morphology. Since all syntheses were performed in Tris buffer with the addition of MgCl2, the final depleted hydroxyapatite incorporated magnesium. It was found that in the first 24 h, the reaction product form is determined by the enzyme source as well as the presence of other biopolymers (in particular, humic acid) in the reaction mixture. Hollow nanospheres of the depleted hydroxyapatite were obtained as a final product for both E. coli and calf-intestinal alkaline phosphatase during a 7-day reaction. When humic acid was added into the reaction mixture, separate spheres of the depleted hydroxyapatite were observed during a 24-h reaction. When Mg ions are present in the reaction mixture as a buffer component, they are evenly incorporated into the structure of the resulting calcium phosphate. The data obtained can be useful in understanding the calcification process of bioobjects and in applying the enzymatic method of calcium phosphate synthesis to biomedical applications.

Calcium phosphate formation and deposition in ischemic neurons.

Ischemic stroke causes acute brain calcium phosphate (CaP) deposition, a process involving primarily the injured neurons. Whereas the adverse impact of CaP deposition on the brain structure and function has been recognized, the underlying mechanisms remain poorly understood. This investigation demonstrated that the neuron-expressed, plasma membrane-associated Ca2+-binding proteins annexin (Anx) A2, AnxA5, AnxA6, and AnxA7 contributed to neuronal CaP deposition in the mouse model of ischemic stroke. These Anxs were released from the degraded plasma membrane of the ischemic neurons and were able to form Anx/CaP complexes, a nanostructure capable of binding to the β actin filaments via Anx-actin interaction to cause neuronal CaP deposition prior to brain infarction. Anx administration to the healthy mouse brain caused brain CaP deposition and infarction. Monomeric β actin was able to block competitively Anx binding to β actin filaments and prevent ischemic stroke- and Anx administration-induced brain CaP deposition and infarction. Administration of siRNAs specific to the four Anx mRNAs alleviated brain CaP deposition and infarction. These observations support the role of Anxs in CaP formation and deposition in ischemic neurons.

Visible light-induced simultaneous bioactive amorphous calcium phosphate mineralization and in situ crosslinking of coacervate-based injectable underwater adhesive hydrogels for enhanced bone regeneration

The field of bone tissue engineering is vital due to increasing bone disorders and limitations of traditional grafts. Injectable hydrogels offer minimally invasive solutions but often lack mechanical integrity and biological functionality, including osteoinductive capacity and structural stability under physiological conditions. To address these issues, we propose a coacervate-based injectable adhesive hydrogel that utilizes the dual functionality of in situ photocrosslinking and osteoinductive amorphous calcium phosphate formation, both of which are activated simultaneously by visible light irradiation. The developed hydrogel formulation integrated a photoreactive agent with calcium ions and phosphonodiol in a matrix of tyramine-conjugated alginate and RGD peptide-fused bioengineered mussel adhesive protein, promoting rapid setting, robust underwater adhesion, and bioactive mineral deposition. The hydrogel also exhibited superior mechanical properties, including enhanced underwater tissue adhesive strength and compressive resistance. In vivo evaluation using a rat femoral tunnel defect model confirmed the efficacy of the developed adhesive hydrogel in facilitating easy application to irregularly shaped defects through injection, rapid bone regeneration without the addition of bone grafts, and integration within the defect sites. This injectable adhesive hydrogel system holds significant potential for advancing bone tissue engineering, providing a versatile, efficient, and biologically favorable alternative to conventional bone repair methodologies.

The Remineralization of Enamel from Saliva: A Chemical Perspective.

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

Microstructural and biological characterization of 3D printed PEEK scaffolds coated with alginate/CNT for bone regeneration applications

The main aim of bone tissue engineering is to develop novel scaffold structures that integrate biological functionality with sufficient mechanical strength and properties. In this study, bone scaffolds were fabricated using polyether ether ketone (PEEK) via 3D printing, resulting in three different porous designs. To enhance their biological attributes, these scaffolds were coated with an alginate and carbon nanotube (CNT) composite using a freeze-drying technique. The biological characteristics of fabricated samples, such as biocompatibility and bioactivity, were evaluated in simulated body fluid (SBF). Field emission scanning electron microscopy (FE-SEM) analysis showed that the 3D-printed PEEK scaffolds had a porous, uniform, and interconnected architecture with pore sizes between 321–378 µm. Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) confirmed the formation of hydroxyapatite (HA) and bioactive calcium phosphate (Ca-P) on the scaffold surfaces, indicating their bioactivity. Cell biocompatibility was assessed using the MTT assay, which revealed a high cell viability rate of approximately 97% and no significant toxicity. Consequently, the 3D-printed PEEK scaffold coated with Alginate/0.3%wt CNT demonstrated promising microstructure, bioactivity, and biocompatibility, making it suitable for bone tissue regeneration.Graphical abstract

Essential oil release from zein particles as modulated by inorganic coating and biopolymeric networking

Zein particles (ZPs) have emerged as a popular delivery carrier for hydrophobic bioactive substances. However, some lipophilic compounds are easily released from ZPs because of the low polarity compatibility between zein and the compounds. The loss of encapsulated substances is particularly evident for citrus essential oil (CEO), an extremely hydrophobic ingredient. The premature release of CEO from ZPs was mitigated by developing a modification approach using ZPs coated with calcium phosphate (CaP) and networked with Ca2+-alginate gel (CaAlg). The approach involved the preparation of ZPs (through the antisolvent addition procedure) in phosphate buffer, and supplementation of the particles consecutively with sodium alginate and Ca2+ ions (as CaCl2). This procedure resulted in retention of up to 28% of CEO within ZPs after the accelerated storage experiment. Under in vitro gastric and intestinal digestion condition, the CaP-coated and CaAlg-networked ZPs had a significantly lower release of CEO compared to their non-coated and non-networked counterparts. The morphology of the particles was investigated by scanning (SEM) and transmission (TEM) electron microscopies, as well as confocal laser scanning microscopy. SEM imaging showed that sodium alginate could facilitate the formation of CaP coating through preventing CaP crystallization. CaP coating also decreased the ZPs fusion/aggregation as evidenced by comparing the ζ-potential and microscopic morphology of the particles. Examination of the infrared spectra of the particles revealed that the formation of CaP coating occurred at Ca2+ ion concentrations ≥ 10 mM.

Promotion effect of proanthocyanidin on dentin remineralization via the polymer induced liquid precursor process

Proanthocyanidin (PA) has demonstrated promise as a dental biomodifier for maintaining dentin collagen integrity, yet there is limited evidence regarding its efficacy in dentin repair. The aim of this study was to investigate the effect of PA on dentin remineralization through the polymer induced liquid precursor (PILP) process, as well as to assess the mechanical properties of the restored dentin. Demineralized dentin was treated with a PA-contained remineralization medium, resulting in the formation of PA-amorphous calcium phosphate (ACP) nanoparticles via the PILP process. The kinetics and microstructure of remineralized dentin were examined through the use of Fourier transform infrared spectroscopy(FTIR), attenuated total reflectance-FTIR, scanning electron microscopy, transmission electron microscopy. The results showed that the application of PA facilitated the process of dentin remineralization, achieving completion within 48 h, demonstrating a notable reduction in time required. Following remineralization, the mechanical properties of the dentin exhibited an elastic modulus of 15.89 ± 1.70 GPa and a hardness of 0.47 ± 0.08 GPa, which were similar to those of natural dentin. These findings suggest that combining PA with the PILP process can promote dentin remineralization and improve its mechanical properties, offering a promising new approach for dentin repair in clinical practice.

Branched Polymeric Prenucleation Assemblies Initiate Calcium Phosphate Precipitation.

The formation of crystalline calcium phosphate (CaP) has recently gained ample attention as it does not follow the classic nucleation-and-growth mechanism of solid formation. Instead, the precipitation mechanisms can involve numerous intermediates, including soluble prenucleation species. However, structural features, stability, and transformation of such solution-state precursors remain largely undisclosed. Herein, we report a detailed and comprehensive characterization of the sequential events involved in calcium phosphate crystallization starting from the very early prenucleation stage. We integrated an extensive set of time-resolved methods, including NMR, turbidimetry, SAXS, cryo-TEM, and calcium-potentiometry to show that CaP nucleation is initiated by the transformation of "branched" polymeric prenucleation assemblies into amorphous calcium phosphate spheres. Such a mineralization process starts with the spontaneous formation of so-called nanometric prenucleation clusters (PNCs) that later assemble into those branched polymeric assemblies without calcium ion uptake from the solution. Importantly, the branched macromolecular species are invisible to many techniques (NMR, turbidity, calcium-potentiometry) but can readily be evidenced by time-resolved SAXS. We find that these polymeric assemblies constitute the origin of amorphous calcium phosphate (ACP) precipitation through an unexpected process: spontaneous dissolution is followed by local densification of 100-200 nm wide domains leading to ACP spheres of similar size. Finally, we demonstrate that the timing of the successive events involved in the CaP mineralization pathway can be kinetically controlled by the Ca2+/Pi molar ratio, such that the lifetime of the soluble transient species can be increased up to hours when decreasing it.

Biomimetic Calcium Phosphate Nanoparticles: Biomineralization Models and Precursors for Composite Materials.

The formation of calcium phosphate under the control of water-soluble polymers is important for understanding bone growth in living organisms. These experiments also have spin-offs in the creation of composite materials, including for regenerative medicine applications. The formation of calcium phosphate (hydroxyapatite) from calcium chloride and diammonium phosphate was studied in the presence of polymers containing carboxyl, amine, and imidazole groups. Depending on the polymer composition, solid products and stable dispersions of positively or negatively charged nanoparticles were obtained. Oppositely charged nanoparticles can interact with each other to form a macroporous composite material, which holds promise as a filler for bone defects. The formation of a calcium phosphate layer around a living cell (dinoflagellate Gymnodinium corollarium A. M. Sundström, Kremp et Daugbjerg) using positive composite nanoparticles is a one-step approach to cell mineralization.

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

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

Thermally modified sepiolite integrated with aluminum chloride for phosphorus loading management of heavily polluted urban waters

Phosphorus (P) is one of the characteristic pollutants in urban heavily polluted river waters. How to control P enrichment and manage the P loading by a green and efficient adsorbent is an important challenge to control polluted waters. Modified sepiolite is often utilized for the regulation of phosphate in contaminated urban aquatic environments due to its excellent adsorption capacity. In the research, the modification of natural sepiolite with chloride at high temperature (C/Al-Sep) was conducted to enhance its P adsorption capacity and effectively manage the P loading in polluted waters. Batch adsorption experiments demonstrated that the capacity of phosphate adsorbed by C/Al-Sep was significantly improved after composite modification. Adsorption isotherm results indicated that the maximum phosphate adsorption capacity was approximately 13.75 mg/g. Furthermore, the modified sepiolite maintained a stable adsorption capacity over a wide pH range, except CO32- and HCO3-. The adsorption capacity of these common anions in water was almost unaffected. The characterization and adsorption experiments showed that the phosphate adsorption by C/Al-Sep was primarily driven by chemisorption. Additionally, the modification treatment increased the specific surface area of the sepiolite. The main mechanism of phosphate adsorption by the modified sepiolite was the formation of calcium-phosphate precipitates with the inner layer of Al-OP complexes. The results of the research indicate that the use of thermally modified sepiolite in combination with aluminum chloride provides an all-purpose, environmentally friendly material for the subsequent in-situ coverage of contaminated substrates and for the remediation of phosphates in heavily polluted urban waters.

Comparative study of calcium phosphate formation on sol-gel and solid-state synthesized calcium titanate surfaces

Comparative study of calcium phosphate formation on sol-gel and solid-state synthesized calcium titanate surfaces

Evaluation of baghdadite (Ca3ZrSi2O9) cements for the application as novel endodontic filling materials

ObjectivesBaghdadite (Ca3ZrSi2O9) cements of various composition have been investigated in this study regarding an application as endodontic filling materials. MethodsCements were either obtained by mixing mechanically activated baghdadite powder with water (maBag) or by subsequently substituting the ß-tricalcium phosphate (ß-TCP) component in a brushite forming calcium phosphate cement. The cements were analyzed for their mechanical performance, injectability, radiopacity, phase composition and antimicrobial properties. ResultsThe cements demonstrated sufficient mechanical performance with a compressive strength of ∼1 MPa (maBag) and 2.3 – 17.4 MPa (substituted calcium phosphate cement), good injectability > 80 % depending on the powder to liquid ratio and an intrinsic radiopacity of 1.13 – 2.05 mm aluminum equivalent. Immersion in artificial saliva proved their bioactivity by the formation of calcium phosphate and calcium silicate precipitates on the cement surface. The bacterial activity of Staphylococcus aureus cultured on the surface of the cements was found to be similar compared to clinical standard ProRoot MTA cement or even reduced by a factor of 3 for Streptococcus mutans. SignificanceIn combination with their antibacterial properties, baghdadite cements are thought to have the potential to fulfil the clinical requirements for endodontic filling materials.

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

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

Electron Microscopy for the Stability Assessment of Parenteral Nutrition Admixtures: Focus on Precipitation.

(1) Background: parenteral nutrition (PN) is indispensable for patients unable to receive oral or enteral feeding. However, the complexity of PN solutions presents challenges regarding stability and compatibility. Precipitation reactions may occur. The most frequent is the formation of calcium phosphate (Ca-P). The different factors influencing these reactions must be considered to ensure patient safety. (2) Methods: eight paediatric PN solutions were prepared, following standard protocols. Samples were stored at room temperature and in a refrigerator. Electron microscopy, coupled with energy dispersive X-ray spectroscopy (EDS), was employed. Precipitates were analysed for composition and morphology. (3) Results: precipitates were observed in all samples, even at day 0. Crystalline structures, predominantly composed of calcium or magnesium, sometimes associated with chlorine or phosphorus, were detected. Additionally, amorphous precipitates, contained heterogeneous compositions, including unexpected elements, were identified. (4) Conclusions: various precipitates, primarily calcium- or magnesium-based, can form in PN solutions, although it is not expected that they can form under the real conditions of use. Calcium oxalate precipitation has been characterised, but the use of organic calcium and phosphate salts appears to mitigate calcium phosphate precipitation. Electron microscopy provides interesting results on NP precipitation, but sample preparation may present technical limitations that affect the interpretation of the results.

The Rise in Tubular pH during Hypercalciuria Exacerbates Calcium Stone Formation.

In calcium nephrolithiasis (CaNL), most calcium kidney stones are identified as calcium oxalate (CaOx) with variable amounts of calcium phosphate (CaP), where CaP is found as the core component. The nucleation of CaP could be the first step of CaP+CaOx (mixed) stone formation. High urinary supersaturation of CaP due to hypercalciuria and an elevated urine pH have been described as the two main factors in the nucleation of CaP crystals. Our previous in vivo findings (in mice) show that transient receptor potential canonical type 3 (TRPC3)-mediated Ca2+ entry triggers a transepithelial Ca2+ flux to regulate proximal tubular (PT) luminal [Ca2+], and TRPC3-knockout (KO; -/-) mice exhibited moderate hypercalciuria and microcrystal formation at the loop of Henle (LOH). Therefore, we utilized TRPC3 KO mice and exposed them to both hypercalciuric [2% calcium gluconate (CaG) treatment] and alkalineuric conditions [0.08% acetazolamide (ACZ) treatment] to generate a CaNL phenotype. Our results revealed a significant CaP and mixed crystal formation in those treated KO mice (KOT) compared to their WT counterparts (WTT). Importantly, prolonged exposure to CaG and ACZ resulted in a further increase in crystal size for both treated groups (WTT and KOT), but the KOT mice crystal sizes were markedly larger. Moreover, kidney tissue sections of the KOT mice displayed a greater CaP and mixed microcrystal formation than the kidney sections of the WTT group, specifically in the outer and inner medullary and calyceal region; thus, a higher degree of calcifications and mixed calcium lithiasis in the kidneys of the KOT group was displayed. In our effort to find the Ca2+ signaling pathophysiology of PT cells, we found that PT cells from both treated groups (WTT and KOT) elicited a larger Ca2+ entry compared to the WT counterparts because of significant inhibition by the store-operated Ca2+ entry (SOCE) inhibitor, Pyr6. In the presence of both SOCE (Pyr6) and ROCE (receptor-operated Ca2+ entry) inhibitors (Pyr10), Ca2+ entry by WTT cells was moderately inhibited, suggesting that the Ca2+ and pH levels exerted sensitivity changes in response to ROCE and SOCE. An assessment of the gene expression profiles in the PT cells of WTT and KOT mice revealed a safeguarding effect of TRPC3 against detrimental processes (calcification, fibrosis, inflammation, and apoptosis) in the presence of higher pH and hypercalciuric conditions in mice. Together, these findings show that compromise in both the ROCE and SOCE mechanisms in the absence of TRPC3 under hypercalciuric plus higher tubular pH conditions results in higher CaP and mixed crystal formation and that TRPC3 is protective against those adverse effects.

Impact of ZrO2 Content on the Formation of Sr-Enriched Phosphates in Al2O3/ZrO2 Nanocomposites for Bone Tissue Engineering.

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.

Inhibiting Pathological Calcium Phosphate Mineralization: Implications for Disease Progression.

Pathological calcifications, especially calcium phosphate microcalcifications (MCs), appear in most early breast cancer lesions, and their formation correlates with more aggressive tumors and a poorer prognosis. Hydroxyapatite (HA) is a key MC component that crystallizes in the tumor microenvironment. It is often associated with malignant breast cancer lesions and can trigger tumorigenesis in vitro. Here, we investigate the impact of additives on HA crystallization and inhibition, and how precancerous breast cells respond to minerals that are deposited in the presence of these additives. We show that nonstoichiometric HA spontaneously crystallizes in a solution simulating the tumor microenvironmental fluids and exhibits lump-like morphology similar to breast cancer MCs. In this system, the effectiveness of poly(aspartic acid) and poly(acrylic acid) (PAA) to inhibit HA is examined as a potential route to improve cancer prognosis. In the presence of additives, the formation of HA lumps is associated with the promotion or only minimal inhibition of mineralization, whereas the formation of amorphous calcium phosphate (ACP) lumps is followed by inhibition of mineralization. PAA emerges as a robust HA inhibitor by forming spherical ACP particles. When precancerous breast cells are exposed to various HA and ACP minerals, the most influential factors on cell proliferation are the mineral phase and whether the mineral is in the form of discrete particles or particle aggregates. The tumorigenic effects on cells, ranging from cytotoxicity and suppression of proliferation to triggering of proliferation, can be summarized as HA particles < HA aggregates < ACP particles < ACP aggregates. The cellular response to minerals can be attributed to a combination of factors, including mineral phase, crystallinity, morphology, surface texture, aggregation state, and surface potential. These findings have implications for understanding mineral-cell interactions within the tumor microenvironment and suggest that, in some cases, the byproducts of HA inhibition can contribute to disease progression more than HA itself.