Amorphous Calcium Phosphate Research Articles (Page 1)

Chitin whisker liquid crystal hydrogel embedded with polyacrylic acid templating osteoid-like Bouligand structure for guiding internal mineralization.

Quaternary ammonium chitosan film loading ultrasmall calcium phosphate nanoclusters for biomimetic mineralization with antibacterial ability.

Background/Objectives: Dental caries, one of the most common oral diseases worldwide, represents a major public health concern. Contemporary dentistry has established several non-invasive approaches and resin infiltration, as a micro-invasive path, in the treatment of white spot lesions (WSLs). This study aimed to evaluate the effect of different WSL treatments on enamel surface microhardness. Materials and Methods: Seventy-five intact human premolars extracted upon orthodontic indication and the demineralizing solution composed of acetic acid, monopotassium phosphate and calcium chloride with pH = 4.4 and exposure time 96 h were used. The samples were randomly divided into five groups (n = 15): I—intact enamel (control group); II—artificial white spot lesion; III—artificial WSL treated with fluoride varnish; IV—artificial WSL treated with casein phosphopeptide—amorphous calcium phosphate (CPP-ACP) paste; V—resin-infiltrated artificial WSL. The surface microhardness was determined using the Oliver–Pharr method and a spherical indenter (Shimadzu Indenter, Kyoto, Japan). One-way analysis of variance (ANOVA) followed by a Post Hoc test (Bonferroni) was used with a level of significance set at p < 0.05. Results: Resin-infiltrated white spot lesions showed comparable microhardness mean value as the control group: 68.23 (±21.45) and 63.57 (±18.89), respectively (p > 0.05). Also, resin infiltration increased enamel microhardness compared to WSL values, with a statistically significant difference (p < 0.05). Fluoride varnish and CPP-ACP treatment resulted in equivalent values (50.84 ± 14.35 and 50.99 ± 15.31, respectively). Conclusions: Different WSL treatments (fluoride varnish, CPP-ACP and resin infiltration) produced comparable enamel microhardness values. Among the tested agents, resin infiltration resulted in higher microhardness values, while fluoride varnish and CPP-ACP demonstrated equivalent outcomes.

This study investigates the adsorption efficiency of thermally activated natural opoka, a siliceous–calcareous sedimentary rock, as a low-cost adsorbent for removing phosphorus from aqueous solutions. Comprehensive characterization using XRF, XRD, and STA revealed that raw opoka is primarily composed of quartz, tridymite, and calcite, with a CaO/SiO2 molar ratio of approximately 0.45. After calcination at 850 °C, calcite decomposes and reacts with silica to form wollastonite, enhancing surface reactivity. Adsorption experiments conducted at phosphorus concentrations of 0.2, 2.6, and 5.0 g of P/L demonstrated that the material’s removal efficiency for phosphorus was highest at low concentrations (25.7% at 0.2 g/L) and decreased with an increase in concentration (20.8% at 2.6 g/L and 18.6% at 5.0 g/L). The adsorption process followed pseudo-second-order kinetics (R2 > 0.999), indicating that chemisorption is the dominant mechanism. It is assumed that amorphous calcium phosphate forms at low phosphorus concentrations and an alkaline pH, whereas brushite is more prevalent at higher concentrations under acidic conditions. Potassium adsorption was negligible and reversible in all cases. The findings demonstrate that calcined opoka has promising applications as a reactive calcium silicate material for sustainable phosphorus management in decentralized water treatment systems.

Objective: This in vitro study quantitatively compared the time-dependent remineralization potential of three professional agents on artificially induced enamel lesions using Scanning Electron Microscopy (SEM) and energy-dispersive X-ray analysis (EDX). Methods: Sixty extracted sound molars were randomly assigned to three groups (number = 20): G_CPP-ACP, treated with casein phosphopeptide–amorphous calcium phosphate; G_Zn-HA, treated with zinc-hydroxyapatite; and G_F-ACP, treated with fluoridated amorphous calcium phosphate. The crown of each tooth was divided into three areas: one represented the control (CTRL, sound enamel), one underwent demineralization (DEMIN, demineralized enamel), and the third one was at first demineralized and then treated with a remineralizing agent, allowing intra-sample comparison. Artificial lesions were produced by immersion in 0.1 M lactic acid (72 h). Groups were subdivided according to remineralization time (7, 14, 21, and 28 days). Samples underwent daily treatment under a pH-cycling regimen. Surface morphology and Ca/P ratios were evaluated by SEM-EDX, and data were statistically analyzed (p < 0.05). Results: All agents promoted a progressive increase in Ca/P ratio over time, confirming a time-dependent remineralization effect. At day 7, G_Zn-HA showed higher Ca/P values, but from day 14 onward, G_F-ACP produced significantly greater mineral gain than the other groups (p < 0.05). By day 21, G_F-ACP reached Ca/P values approaching CTRL, while G_CPP-ACP and G_Zn-HA remained at lower levels, reaching a plateau respectively at 21 and 14 days. SEM observations supported these findings: G_CPP-ACP and G_Zn-HA showed partial surface recovery, whereas G_F-ACP exhibited a compact, homogeneous enamel-like structure at 28 days. Conclusions: All tested agents demonstrated time-dependent remineralization, enhanced with prolonged exposure, suggesting that the time of application represents a key factor for clinical success.

Objective: To assess the influence of the combination of the antibacterial monomer dimethylaminohexadecyl methacrylate (DMAHDM) and amorphous calcium phosphate nanoparticles (NACP) on the antibacterial and ion release potentials, as well as the physical properties of experimental resin infiltrants. Methodology: The study comprised the following groups: ERI (Pure Experimental Resin Infiltrant [ERI]: 75% TEGDMA + 25% BisEMA, 0.5% camphorquinone [CQ], and 1% ethyl 4-dimethylaminobenzoate [EDMAB]); ERIDM (ERI + 3% DMAHDM), ERINACP (ERI + 1.5% NACP), and ERIDM_NACP (ERI + 3% DMAHDM + 1.5% NACP). From samples of each group, Degree of Conversion (DC; n=6) and Sorption and Solubility (SO/SOL; n=8) were assessed. The antibacterial potential was evaluated through biomass accumulation (BA; n=6) and bacterial metabolism (BM; n=6) assays after cultivating Streptococcus mutans biofilm on the materials. Ionic release (IR; n=3) of Ca2+ and PO4 (3-) from the groups after 7, 14, and 28 days of immersion was also analyzed. Data were analyzed for normality and homoscedasticity, and statistical analysis was performed using appropriate tests with a significance level of 5%. Results: For DC, ERIDM showed no statistical difference from ERI. ERI had the lowest means of SO/SOL, and ERIDM_NACP had the highest. ERIDM exhibited no statistical difference from ERI. For BM, ERIDM and ERIDM_ NACP had the lowest means. ERINACP and ERIDM_NACP exhibited ionic release during the analyzed period. Conclusions: The resin infiltrant containing DMAHDM and NACP exhibits potent antibacterial activity against S. mutans and Ca2+ and PO4 (3-) ionic release.

Modified casein-stabilized amorphous calcium phosphate nanoparticles prevent dental caries by inhibiting the growth of Streptococcus mutans and promoting the remineralization of tooth enamel.

Vivianite recovery from anaerobic groundwater reverse osmosis concentrate.

In this study, we investigated the hydration and aggregation dynamics of Ca2+ and phosphate species, as well as the structural characteristics of calcium phosphate clusters, within a two-dimensional (2D) nanochannel using molecular dynamics simulations with a deep learning potential. Our findings show that ion dynamics are markedly enhanced under confinement, primarily due to accelerated water dynamics. Ion hydration within the 2D nanochannel is reduced as a result of layered water distribution and frequent water exchange around ions compared to the bulk phase solution, thereby facilitating coordination between Ca2+ and phosphate species despite observed polarization effects. However, an increased energy barrier for association between Ca2+ and phosphate species can slow their aggregation within the 2D nanochannel. Since protonated phosphate species exhibit a stronger preference for interfacial water layers than PO43-, fewer protons are present in cluster of Ca2+ and phosphate species in the bulk-like region, which facilitates the association of Ca2+ and phosphate species. The interfacial enrichment of protonated species can also promote the transformation of amorphous calcium phosphate (ACP) to hydroxyapatite. Our results presented here elucidate the influence of nanoconfinement and interfacial interactions on calcium phosphate aggregation within 2D nanochannels, offering valuable insights into biological and biomimetic mineralization processes.

Severe bone injuries often lead to elevated concentrations of reactive oxygen species (ROS), resulting in oxidative stress that can disrupt cellular repair mechanisms, induce cell death, or even trigger malignant transformations. Addressing oxidative stress in the defect microenvironment is thus pivotal for effective bone tissue regeneration. This study explores the multifunctional potential of bioactive glass co-releasing manganese ions and gallic acid (GA) as a strategy to mitigate oxidative damage. Two bioactive glasses, 58S and manganese-doped 58S-5Mn, were synthesized via the sol-gel method. Structural characterization revealed that 58S partially crystallized during calcination, forming apatite crystals within the glassy matrix. On the other hand, 58S-5Mn exhibited an amorphous structure, confirming successful manganese integration as a network modifier. Adsorption kinetics and isotherms demonstrated rapid GA uptake in both samples during the initial hours of contact. The kinetic profile fitting indicated that the pseudo-second-order model yielded the best fits, suggesting a retention process driven by the availability of active sites on the samples' surface. Besides, the adsorption isotherms revealed that the maximum loading capacity of the sorbents 58S and 58S-5Mn reached 45 mg/g and 40 mg/g, respectively. The functionalized samples were then denoted 58S-GA and 58S-5Mn-GA for the reference and manganese-doped, respectively. In vitro bioactivity tests in Simulated Body Fluid (SBF) showed that GA functionalization preserved the apatite-forming capability of the glasses. Within one day of immersion, 58S and 58S-GA induced apatite formation, likely due to their higher calcium content and pre-existing apatite crystals acting as nucleation sites. For Mn-doped samples, an amorphous calcium phosphate layer formed initially, with crystallization commencing after seven days, resulting in more apatite crystals in 58S-5Mn compared to 58S-5Mn-GA. Antioxidant assessments revealed significant ROS scavenging properties for the functionalized and manganese-doped samples. Manganese doping enabled 58S-5Mn and 58S-5Mn-GA to scavenge over 80% of hydrogen peroxide after 72 hours, while non-doped samples remained inactive. Similarly, DPPH radical scavenging assays highlighted the synergistic antioxidant effects of GA functionalization. Functionalized samples achieved DPPH scavenging rates of 80–90%, with 58S-5Mn-GA exhibiting an IC50 of 1 mg/ml, compared to 2 mg/ml for 58S-GA. These findings underscore the complementary roles of manganese doping and GA functionalization in enhancing the antioxidant properties of bioactive glasses, offering distinct mechanisms to stabilize various ROS and highlighting their potential for improving bone regeneration outcomes.

Biomineralisation is a remarkable biological process in which living organisms exert precise control over the nucleation and growth of inorganic crystalline phases, resulting in the formation of hierarchically structured biocomposites that exhibit exceptional mechanical and functional properties. Since damage to bone and teeth directly affect everyday life, various biomimetic mineralised materials have been engineered for use in biomedical applications. While bioinspired materials typically demonstrate superior mechanical properties and biological functions, significant disparities remain between biomimetic constructs and their natural counterparts, especially concerning mechanical performance and multiscale structural organisation. This review initially describes the dynamic reciprocity between type I collagen fibrils, amorphous calcium phosphate phases and multifunctional non-collagenous protein within mineralisation microenvironments. Furthermore, it evaluates recent progress in advanced biomaterials based on biomimetic mineralisation strategies and seeks to spark innovative and promising solutions for investigators exploring biomineralisation principles in regenerative medicine and hard tissue reconstruction. Existing problems and future directions are discussed.

Rationale: Osteoarthritis (OA) is increasingly understood as a disease involving not only cartilage degeneration but also pathological subchondral bone remodeling. The contribution of osteoblast (OB) heterogeneity and their secreted extracellular vesicles (EVs) to this process remains poorly characterized. This study aims to investigate how EVs from distinct OB subtypes modulate subchondral bone remodeling and contribute to OA progression.Methods: OB subtypes representing endothelial (EnOBs), stromal (StOBs), and mineralizing (MinOBs) stages were generated by time-controlled osteogenic induction of BMSCs. EVs were isolated from each OB subtype and characterized by TEM, Western blot, DLS, and miRNA profiling. Functional assays included osteogenic induction, angiogenesis, and cartilage degradation analyses in vitro. RNA-seq and qRT-PCR were used to identify relevant signaling pathways and miRNAs. In vivo effects of EVs were tested in a DMM-induced OA mouse model using intravenous injections, followed by histology, micro-CT, and immunostaining.Results: EVs derived from different OB subtypes exhibited distinct pro-osteogenic, pro-angiogenic, and cartilage-degrading effects. MinOB-derived EVs significantly enhanced osteogenic differentiation and mineralization, correlated with enrichment of calcium phosphate content and specific pro-osteogenic miRNAs. These EVs also carried amorphous calcium phosphate and mitochondrial content, linked to activated mitophagy. Wnt signaling dynamically regulated mitophagy and EV composition, particularly in MinOBs. In vivo, tail vein administration of OB-derived EVs exacerbated subchondral bone sclerosis and cartilage degradation in a time-dependent manner, with MinOB-EVs inducing the most pronounced pathological changes.Conclusions: OB-derived EVs exhibit subtype-dependent regulatory functions in subchondral bone remodeling, mediated by distinct miRNA profiles and mineral cargo shaped by Wnt-regulated mitophagy. These EVs actively participate in OA progression, and their effects vary with disease stage and route of administration. Targeting specific OB subtypes or modulating Wnt-mitophagy signaling may offer novel therapeutic strategies for stage-specific OA intervention.

Comminuted fractures, characterized by multiple irregular bone fragments, present significant challenges for traditional fixation methods like plates and screws, often resulting in complex surgeries and delayed healing. Injectable hydrogel adhesives have been applied for comminuted fractures, but face challenges such as excessive fluidity before curing and curing processes that involve high temperatures or ionic release, which can result in material leakage, localized inflammation and reduced adhesion. To address these challenges, we developed a humidity-responsive hydrogel adhesive system, comprised of tannic acid (TA), silk fibroin (SF), amorphous calcium phosphate (ACP), and guanidine hydrochloride (GuCl). GuCl acts as a hydrogen bond disruptor, which enables faster and more complete penetration of the hydrogels into bone fragments. Upon exposure to body fluids, GuCl diffuses out, allowing hydrogen bonds to reform. This process enabled the hydrogel to dynamically transition from a low-modulus, injectable state to a high-modulus, adhesive gel. Moreover, the presence of ACP enhanced the mechanical and mineralization properties of the hydrogel. The resultant hydrogel showed desirable biocompatibility and osteogenic properties, both in vitro and in vivo. Collectively, this research addressed the critical issue of the difficulty of injectable bone bonding materials to penetrate irregular bone fragments and maintain good biocompatibility while rapidly solidifying in situ. This system demonstrates significant potential for clinical application in the effectively treatment of complex bone injuries, especially for in situ repair of comminuted fractures. STATEMENT OF SIGNIFICANCE: Comminuted fractures involve multiple irregular bone fragments, posing serious challenges for fixation using traditional hardware. Existing injectable adhesives often suffer from poor cohesion, inflammatory side effects, and inadequate curing control. We present a moisture-responsive hydrogel adhesive (rTSA-G), composed of tannic acid, silk fibroin, amorphous calcium phosphate, and guanidine hydrochloride. This system exhibits high injectability, transitions rapidly to a solid upon contact with water, and provides strong adhesion, mechanical support, and osteoinductive properties. By addressing the key limitations of current bone adhesives, this strategy offers a promising alternative for minimally invasive treatment of complex fractures and advances the development of next-generation stimulus-responsive biomaterials.

Intrafibrillar mineralization plays an important role in dentin repair. Current research on intrafibrillar mineralization primarily focuses on the precise positioning of mineral precursors within collagen and the reduction of mineralization time. Inspired by the multifunctionality of noncollagenous proteins (NCPs), we developed a dual-analogue system, 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) followed by 3-(3,4-dihydroxyphenyl)-l-alanine (l-DOPA)-stabilized amorphous calcium phosphate (M + LA), which integrated a nucleation inhibitor l-DOPA and inducer 10-MDP. In this study, we investigated the impact of a preinfiltration strategy using the M + LA system on intrafibrillar mineralization. l-DOPA with a concentration of 250 μg mL-1, acting as a mussel-inspired nucleation inhibitor, was demonstrated to stabilize amorphous calcium phosphate (ACP) precursors within 2 h at 37 °C, with the formed precursors termed "LACP" (l-DOPA-stabilized amorphous calcium phosphate). Numerous LACP precursors were immobilized within collagen via the M + LA system, referred to as "preinfiltration." The M + LA system exhibited no significant cytotoxicity, as evidenced by the biocompatibility evaluation through a modified trans-dentin disk model. Notably, the M + LA preinfiltration strategy significantly reduced intrafibrillar mineralization time to 3 h, superior to that of bare collagen and MDP-modified collagen. Furthermore, the resulting mineralized M + LA-modified collagen achieved functional mechanical properties. Moreover, 10-MDP-Ca nanolayering was generated via a bottom-up approach during the preinfiltration process. This study introduces a preinfiltration strategy for promoting intrafibrillar mineralization, which provides a reference for understanding the mechanism of intrafibrillar mineralization and shows promising clinical application prospects for dentin repair.

This study evaluated a biomimetic filler strategy for two-step universal dental adhesives by integrating amine-functionalized mesoporous silica nanoparticles (MSNs) loaded with polyacrylic acid-stabilized amorphous calcium phosphate (PA–ACP) into the primer phase. MSNs were synthesized and characterized by FTIR, N2 sorption (BET), and HRTEM to confirm structural integrity and effective PA–ACP loading. Two commercial adhesives (G2 Bond and OptiBond eXTRa) were modified by incorporating different volumes fractions (10, 15, 20 vol%) of PA–ACP/MSN. Wettability (contact angle), microtensile bond strength (μTBS), and cytotoxicity (indirect MTT assay using human periodontal ligament fibroblasts, HPLFs) were assessed. The results demonstrated that incorporating up to 15 vol% PA–ACP/MSN maintained favorable wettability and bond strength, comparable to those of the unmodified controls. At 20 vol%, significant increases in contact angles and reductions in bond strength indicated impaired primer infiltration. Cytotoxicity testing confirmed high fibroblast viability (>70%) across all tested concentrations, verifying the biocompatibility of PA–ACP/MSN-filled primers. This work confirms the feasibility of a biomimetic adhesive design using PA–ACP/MSN in the primer phase without compromising immediate wettability and immediate μTBS up to 15 vol%. Remineralization is a potential capability that requires verification in future studies.

Nature organizes the extracellular matrix into hierarchical structures, inspiring the design of biomimetic mineralization scaffolds. Silk fibroin, a noncollagenous structural protein, is a potential template for biomineralization. Here, we show the mineralization behavior of silk nanofibril (SNF) and demonstrate tunable biomineralization through the SNF assembly. We demonstrate the deposition of amorphous calcium phosphate and its transformation into flower-like hydroxyapatite crystals on the SNF interface by exploiting individual SNFs as a model. On two-dimensional (2D) films and three-dimensional (3D) scaffolds, SNF assembly influences the mineralization process. The dense nanofibrils in the SNF film and scaffold undergo mineralization through the anchoring and deposition of hydroxyapatite, whereas the modified 3D scaffolds with fluffy SNF are comparable to individual SNF. Consequently, silk nanotechnology makes use of a controllable assembly to build one-dimensional, 2D, and 3D nanostructures. These results offer new insights into the mineralization mechanisms of silk mesoscopic units and provide pathways for the synthesis of biomineralized scaffolds.

ABSTRACTBackground:The prevalence of dental caries requires pediatric dentistry to pursue efficient preventive methods to tackle the problem. Multiple research has explored the fluoride varnish effectiveness for remineralization, yet the results show contrasting findings. The proposed research evaluates the effectiveness by which different fluoride varnishes can remineralize primary teeth with demineralized enamel.Materials and Methods:A total of sixty extracted primary teeth received artificial enamel lesions under randomized selection that split them into four groups numbering fifteen specimens each for Groups A and B and C and D. The pH cycling procedure was applied to the samples for 14 days. Metabolic testing of surface microhardness took place using a Vickers hardness tester before initiating treatment and after completion. The research used ANOVA statistical analysis together with posthoc tests while setting the significance threshold at P < 0.05.Results:The application of fluoride varnishes in all test groups produced substantial increases in surface microhardness values than those observed in the control group. The highest level of tooth remineralization occurred in Group A where the restoration increased by 45%, while Group B achieved 38% and Group C gained 30%. The control group experienced inferior dental improvements compared with the experimental groups having only a 5% hard tissue increase. The results demonstrated that Group A obtained superior values compared with other groups, while statistical findings indicated a significant group variation with P < 0.001.Conclusion:The highest level of primary tooth remineralization occurs when using 5% sodium fluoride varnish as an effective preventive treatment. Tricalcium phosphate and amorphous calcium phosphate fluoride varnishes demonstrated strong effectiveness in addition to 5% sodium fluoride varnish. Research findings demonstrate that fluoride varnishes need to be considered a fundamental approach for handling young children’s early enamel lesion management.

Dental adhesive loaded with amorphous calcium phosphate for occlusion of dentinal tubules

Dose-dependent osteoimmunomodulatory effects of amorphous calcium phosphate nanoparticles promote 3D-printed scaffold-mediated bone regeneration.

In situ construction of ossification micro-units for critical bone regeneration via sustained lifting of epigenetic suppression.