Fast precipitation of uniform CaCO3 nanospheres and their transformation to hollow hydroxyapatite nanospheres

Visualizing the Internal Nanocrystallinity of Calcite Due to Nonclassical Crystallization by 3D Coherent X-Ray Diffraction Imaging

The internal crystallinity of calcite is investigated for samples synthesized using two approaches: precipitation from solution and the ammonium carbonate diffusion method. Scanning electron microscopy (SEM) analyses reveal that the calcite products precipitated using both approaches have a well-defined rhombohedron shape, consistent with the euhedral crystal habit of the mineral. The internal structure of these calcite crystals is characterized using Bragg coherent diffraction imaging (BCDI) to determine the 3D electron density and the atomic displacement field. BCDI reconstructions for crystals synthesized using the ammonium carbonate diffusion approach have the expected euhedral shape, with internal strain fields and few internal defects. In contrast, the crystals synthesized by precipitation from solution have very complex external shapes and defective internal structures, presenting null electron density regions and pronounced displacement field distributions. These heterogeneities are interpreted as multiple crystalline domains, created by a nonclassical crystallization mechanism, where smaller nanoparticles coalescence into the final euhedral particles. The combined use of SEM, X-ray diffraction (XRD), and BCDI allows for structurally differentiating calcite crystals grown with different approaches, opening new opportunities to understand how grain boundaries and internal defects alter calcite reactivity.

Correlation between positron annihilation lifetime and photoluminescence measurements for calcined Hydroxyapatite

Hydroxyapatite (HAp) Ca10(PO4)6(OH)2 is a compound that has stable chemical properties, composition, and an affinity for human bone. As a result, it can be used in odontology, cancer treatment, and orthopedic grafts to repair damaged bone. To produce calcined HAp at 600 °C with different pH values, a wet chemical precipitation method was employed. All synthesized HAp samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL), Zeta potential, and positron annihilation lifetime spectroscopy (PALS). The XRD results revealed that all calcined HAp samples were formed in a hexagonal structure with a preferred (002) orientation at different pH values. The crystal size of the samples was determined using the Scherrer equation, which ranged from 16 to 25 nm. The SEM and TEM results showed that the morphology of the samples varied from nanorods to nanospheres and rice-like structures depending on the pH value of the sample. The PL measurements indicated that the blue and green emission peaks of HAp were due to defects (bulk, surface, and interface) in the samples, which created additional energy levels within the band gap. According to Zeta potential measurements, the charge carrier changed from a positive to negative value, ranging from 3.94 mV to - 2.95 mV. PALS was used to understand the relationship between the defects and the photoluminescence (PL) properties of HAp. Our results suggest that HAp nanoparticles have excellent potential for developing non-toxic biomedical and optical devices for phototherapy.

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.

Investigation of the acicular aragonite growth behavior in AOD stainless steel slag during slurry-phase carbonation

This study presents a novel method for producing acicular aragonite using argon oxygen decarburization (AOD) slag while controlling the reaction temperature, reaction time, stirring speed, and the magnesium-to‑calcium stoichiometric ratio. This approach provides steel plants with an opportunity to decrease their CO2 emissions and promote efficient resource utilization and CO2 storage through the production of high-quality value-added products. The experimental results showed that reaction temperature was the most significant factor affecting the carbonation efficiency of AOD slag, followed by reaction time, stirring speed, CO2 partial pressure, and the liquid-to-solid ratio (L/S). The study also found that elevated temperature and prolonged reaction duration favored the preferential precipitation of aragonite. Additionally, raising the temperature and the magnesium-to‑calcium stoichiometric ratio was shown to enhance the formation of aragonite, affecting its crystal growth orientation and dimensions. The optimal combination of reaction parameters for the preparation of acicular aragonite was found to be the reaction time of 8 h, the magnesium-to‑calcium stoichiometric ratio of 0.8, the reaction temperature of 120 °C, and the stirring speed of 200 r·min-1. Under these conditions, the resulting acicular aragonite exhibited excellent overall uniformity, a large aspect ratio, and a smooth crystal surface, with a content of 91.49 %, a single crystal length ranging from 9.86 to 32.6 μm, and a diameter ranging from 0.63 to 2.15 μm. This study provides valuable insights into the efficient production of acicular aragonite from steel slag while reducing CO2 emissions and promoting the sustainable use of resources.

Synthesis of Calcium Carbonate Hollow Microspheres and the Pelletization Mechanism by Electrostatic Attraction of PEG-SDS

Calcium carbonate is a common natural mineral with a wide range of applications. In this study, hollow calcite microspheres were successfully synthesized by using calcium chloride and sodium carbonate as raw materials in an SDS-PEG system. The results suggested that the appropriate concentration of SDS is necessary during the spherical crystallization of calcium carbonate. It was found that the crystals started to aggregate under the effect of SDS, and aggregation was enhanced with an increase in SDS concentration, leading to the transformation from hollow to solid microspheres. However, high temperatures will lead to the transformation from calcite to aragonite, resulting in the collapse of the formed spherical structure. Infrared spectroscopy and conductivity analysis suggested that when the concentration of SDS reached 0.3 g/L in the PEG-SDS system, SDS and PEG formed a spherical supramolecular structure. This structure could act as a template, leading to the aggregation of calcite through electrostatic attraction and finally to the formation of a hollow spherical structure.

Using phenolic polymers to control the size and morphology of calcium carbonate microparticles

Calcium carbonate (CaCO3) is a naturally occurring mineral that occurs in biology and is used industrially. Due to its benign nature, CaCO3 microparticles have found use in the food and medical fields, where the specific size of the microparticles determine their functionality and potential applications. We demonstrate that phenolic polymers with different numbers of hydroxy groups can be used to control the diameter of CaCO3 microparticles in a range of 2-9 μm, and obtained particles were relatively uniform. The largest particles (∼9 μm in diameter) were obtained using poly(2,3,4,5-tetrahydroxystyrene) (P4HS), which showed the highest water solubility among the tested phenolic polymers. The polymer concentration and stirring speed influenced the size of microparticles, where the size of the obtained particles became smaller as the concentrations of phenolic polymers increased and as the stirring speed increased, both likely due to promoting the formation of a large number of individual crystal seeds by shielding seed-seed fusion and increasing the chances for precursor contact, respectively. The preparation time and temperature had a great influence on the morphology of the CaCO3 particles, where vaterite transforms into calcite over time. Specifically, aragonite crystals were observed at preparation temperature of 80 °C and vaterite particles with rough surfaces were obtained at 40 °C. Molecular weight and scale of reaction were also factors which affect the size and morphologies of CaCO3 particles. This research represents a facile method for producing relatively monodisperse CaCO3 microparticles with diameters that have previously proven difficult to access.

Sorption and transport characteristics of europium on sandy soils

Radioactive europium can be released as a fission product during nuclear incidents and pose a threat to the human and surrounding environment because of its biological activity and long decay half-lives. For safe design issues and human health protection demands in construction of the planned nuclear power plants (NPPs) at Al-Dabaa site, it is necessary to study the sorption and transport of different radionuclides as europium within the selected area for predicting their fate at any crisis. Many soil samples were collected from different locations at the area selected along the northwestern coast of Egypt. The samples were transported to the laboratory, preserved, and characterized using X-Ray fluorescence (XRF), Fourier transform infrared spectroscopy (FT-IR), and X-Ray diffraction (XRD). Experiments were performed to study the sorption and transport kinetics of Eu(III) ions on two sandy soil samples from the collected ones. The effect of different parameters (e.g. contact time, pH, initial europium concentration, and temperature) on the sorption behavior europium was explored in a static condition. The maximum sorption capacity was determined and found to be 3.4 and 7.0 mg g^-1 for sorption of Eu(III) ions onto soil-1 and soil-2, respectively. Different models were applied to assess the sorption of europium onto the surface of the investigated soils. Data confirmed that Eu retention was attained through a chemisorption process. Further, the thermodynamic parameters were determined and their values confirmed the endothermic nature of the sorption process. The transport of europium radionuclides, with groundwater, through homogeneous porous media with uniform one-dimensional flow in the geosphere was processed and the relative migration velocity was determined in presence of both distilled and seawater media. The transport of Eu(III) radionuclides was higher in presence of seawater than that in presence of distilled water by about two order of magnitude. This obviously clarified the effect of seawater in accelerating the transport of radionuclides with groundwater in the geosphere of studied area. The role of different competing ions have various valances on the relative migration velocity was explored. Further, the time required for studied radionuclides to reach Mediterranean Sea was determined.

Efficient uranium(VI) adsorbing bioinspired nano-sized hydroxyapatite composites: synthesis, tuning, and adsorption mechanism

The production of large amounts of uranium-containing wastewater and its potential hazards has stimulated green and efficient material removal of uranium (VI). Inspired by the natural mineralization of bone, a facile and eco-friendly biomimetic synthesis of nano-hydroxyapatite (HAP) was carried out using chitosan (CS) as a template. It was found that the reaction temperature and the amount of precursors influence the particle size, crystallinity and specific surface area of the CS/HAP nanorods, and consequently their U(VI) adsorption efficiency. Moreover, the synthesized CS/HAP-40 with smaller particle size, lower crystallinity, and larger specific surface area show a more efficient U(VI) removal compared with CS/HAP-55 and CS/HAP-55-AT. It has a maximum adsorption capacity of 294.12 mg·g^-1 of the CS/HAP-40. Interestingly, the U(VI) removal mechanism of CS/HAP-40 in acidic (pH = 3) and alkaline (pH = 8) aqueous solutions was found to be different. As one of the main results, the U(VI) adsorption mechanisms at pH 8 could be surface complexation and ion exchange. On the contrary, three different mechanisms could be observed at pH 3: dissolution-precipitation to form chernikovite, surface complexation, and ion exchange.

Process optimization for the rapid conversion of calcite into hydroxyapatite microspheres for chromatographic applications

Microsphere hydroxyapatite (HAp) is widely used in various biomedical and chromatographic applications. The work described in this manuscript focuses on a dissolution precipitation method for production of HAp microspheres. This method overcomes certain drawbacks of conventional preparation methods used for HAp preparation, which produce polydisperse particles and are time-consuming and expensive. In the present work, the calcium carbonate (calcite) particles were directly and rapidly converted into HAp microspheres using an inexpensive dissolution precipitation method. The effects of the reaction temperature, time, and mechanical stirring rates were studied, and the reaction parameters were optimized. As confirmed by the XRD studies, the higher reaction temperature and time promote complete HAp conversion, while calcite residues were observed for lower temperatures and times. SEM images show the influence of reaction parameters on the surface microstructure of the microspheres produced. It was observed that the HAp microspheres undergo disintegration at a higher stirring rate. The reaction parameters optimized in this work were ideal for preparing HAp microspheres. The resultant HAp particles were utilized as matrices for chromatographic separation of protein mixtures.

In Situ Synthesis of Fe3O4 Nanoparticles and Wood Composite Properties of Three Tropical Species

Magnetic wood is a composite material that achieves harmony between both woody and magnetic functions through the active addition of magnetic characteristics to the wood itself. In addition to showing magnetic characteristics, magnetic wood offers low specific gravity, humidity control and acoustic absorption ability. It has potential for broad applications in the fields of electromagnetic wave absorption, electromagnetic interference shielding, furniture, etc. This work reports on the synthesis of Fe3O4 nanoparticles (NPs) in wood from three tropical species (Pinus oocarpa, Vochysia ferruginea and Vochysia guatemalensis) using a solution of iron (III) hexahydrate and iron (II) chloride tetrahydrate with a molar ratio of 1.6:1 at a concentration of 1.2 mol/L ferric chlorate under 700 kPa pressure for 2 h. Afterward, the wood samples were impregnated with an ammonia solution with three different immersion times. The treated wood (wood composites) was evaluated for the weight gain percentage (WPG), density, ash content and Fe3O4 content by the Fourier transform infrared spectroscopy (FTIR) spectrum, X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The results show that the species P. oocarpa had the lowest values of WPG, and its density decreased in relation to the untreated wood, with lower ash and Fe3O4 NP content. The XRD and some FTIR signals associated with changes in the wood component showed small differences from the untreated wood. Fe3O4 NPs presented nanoparticles with the smallest diameter of (approx. 7.3 to 8.5 nm), and its saturation magnetization (Ms) parameters were the lowest. On the other hand, V. guatemalensis was the species with the best Ms values, but the wood composite had the lowest density. In relation to the different immersion times, the magnetic properties were not statistically affected. Finally, the magnetization values of the studied species were lower than those of the pure Fe3O4 nanoparticles, since the species only have a certain amount of these nanoparticles (NPs), and this was reflected proportionally in the magnetization of saturation.

Crystal transformation and self-assembly theory of microbially induced calcium carbonate precipitation

Microbially induced calcium carbonate precipitation (MICP) is ubiquitous in the earth's lithosphere and brings the inspiration of bionic cementation technology. Over recent years, MICP has been proposed as a potential solution to address many environmental and engineering issues. However, the stability of cemented precipitations generated via MICP technology, especially the characteristics and change mechanism of crystal forms, is still unclear, which substantially hindered the understanding of biomineralization and prohibited the application and upscaling of MICP technology. Here, Sporosarcina pasteurii was selected as a model microbe to induce calcium carbonate mineralization in a series of standard nutrient solutions. The authors studied the process of precipitation from amorphous calcium carbonate to calcite crystal form and revealed the assembly behavior and mechanism of precipitations by FTIR, SEM, TEM and EDS. In the two crystal forms of induced calcium carbonate, the relative position and content of C, O, N, P and Ca elements were only slightly different. The molecular attachment and structural match of organic matrix made the crystals form change. Finally, a self-assembly theory was proposed to MICP, and it provided a solid theoretical basis for the technical specification of MICP technology in engineering application. KEY POINTS: • Organic matrix is intensively involved in MICP by forming functional groups. • Molecular attachment and structural match cause calcite crystal evolution. • A self-assembly theory is proposed for MICP.

Inverse Material Search and Synthesis Verification by Hand Drawings via Transfer Learning and Contour Detection

Nano- and micromaterials of various morphologies and compositions have extensive use in many different areas. However, the search for procedures giving custom nanomaterials with the desired structure, shape, and size remains a challenge and is often implemented by manual article screening. Here, for the first time, scanning and transmission electron microscopy inverse image search and hand drawing-based search via transfer learning are developed, namely, VGG16 convolution neural network repurposing for image features extraction and image similarity determination. Moreover, the case use of this platform is demonstrated on the calcium carbonate system, where the data are acquired by random high throughput experimental synthesis, and on Au nanoparticles data extracted from the articles. This approach can be used for advanced nanomaterials search, synthesis procedure verification, and can be further combined with machine learning solutions to provide data-driven nanomaterials discovery.

Perovskite-based solar cells fabricated from TiO2 nanoparticles hybridized with biomaterials from mollusc and diatoms

Perovskite solar cells (PVSCs) convert solar energy into electrical energy. Current study employs fabrication of PVSCs using calcium titanate (CaTiO₃) prepared by co-precipitation of TiO₂ nanoparticle (NP) and CaCO₃ NP with later synthesized from mollusc shell. Furthermore, frustules of diatom, Nitzschia palea were used to prepare silica doped CaTiO₃ (Si-CaTiO₃) nanocomposite. CaTiO₃ NP and Si-CaTiO₃ nanocomposites film were made on fluorine doped tin oxide (FTO) glass plate using spin coater separately for two different kinds of PVSCs tested at different intensities of light. The perovskite materials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray (EDX) spectroscopy. Thickness of the film was measured by profilometer. The maximum power density (PD_max) of CaTiO₃ made PVSCs was 0.235 mW/m² under white LED light and 0.041 mW/m² in broad spectrum light. Whereas, PD_max of PVSCs with Si-CaTiO₃ was higher about 0.0083 mW/m² in broad spectrum light and was 0.0039 mW/m² in white LED light. This is due to the fact that CaTiO₃ allowed blue and red light in broad spectrum to pass through it without being absorbed compared to white LED light which gets reflected. On the offset, in PVSC made of Si-CaTiO₃ since diatoms frustules are made up of nanoporous architecture it increases the overall porosity of PVSC making them potentially more efficient in broad spectrum of light compared to white LED light.

Advanced removal of Reactive Yellow 84 azo dye using functionalised amorphous calcium carbonates as adsorbent

Two environmentally friendly organics (ethylenediaminetetraacetic acid, EDTA and its easier biodegradabe isomer, ethylenediamine-N, N'-disuccinic acid, EDDS) were used to dope calcium carbonate (CC) nanoparticles intending to increase their adsorptive properties and evaluate adsorption performance (uptake capacity and removal efficiency) for the persistent Reactive Yellow 84 azo dye. Easily synthesized nanomaterials were fully characterized (morphology and size, mineralogy, organic content, surface area, pore size and hydrodynamic diameter). RY84 removal was performed using two consecutive processes: photodegradation after adsorption. The CC-EDTA particles were most efficient for dye removal as compared to the plain and CC-EDDS particles. Adsorption kinetics and isotherms were considered for the CC-EDTA system. 99% removal occurred via adsorption on 1 g/L of adsorbent at 5 mg/L dye concentration and pH of 8 and it decreased to 48% at 60 mg/L. Maximum uptake capacity as described by Langmuir is 39.53 mg/g. As post-adsorption, under UVA irradiation, in the presence of 40 mmol/L H₂O₂, at dye concentration of 10 mg/L the highest degradation was 49.11%. Substantial decrease of adsorption (ca. 4 times) and photodegradation (ca. 5 times) efficiencies were observed in wastewater effluent as compared to distilled water. The results have important implications to wastewater treatments and appropriate decisions making for the choice of treatment process, process optimization and scaling up to pilot and industrial levels.

Algae-mediated route to biogenic cuprous oxide nanoparticles and spindle-like CaCO3: a comparative study, facile synthesis, and biological properties

Biocompatible syntheses of Cu2O nanoparticles are relatively low compared to some other reported metal oxides due to their low stability and requiring more carefully controlled synthetic conditions. In the present study, the efficiency of three brown algae (Cystoseira myrica, Sargassum latifolium and Padina australis) extracts collected from the Persian Gulf was evaluated in the biosynthesis of Cu2O nanoparticles. A fast and simplified synthesis of Cu2O nanoparticles with average size between 12 and 26 nm was successfully achieved through an eco-friendly method using the aqueous extracts of Sargassum latifolium and Cystoseira myrica. Whereas, under the same reaction conditions using Padina australis extract no Cu2O nanoparticles were produced, and unexpectedly, the results approved the formation of spindle shaped CaCO3 with average sizes of 1-2 μm in length and 300-500 nm in width. Structure, morphology and composition of the as-prepared products were characterized by XRD, FT-IR, UV-vis, TEM and FESEM analysis. This work confirms that the biomolecules present in algae have the ability to affect particle size, morphology, composition, and physicochemical properties of the synthesized particles. The Cu2O nanoparticles prepared in this study were stable and exhibited efficient antibacterial and anticancer activity. This biosynthesis technique can be valuable in environmental, biotechnological, pharmaceutical and medical applications.

Drug Carriers: Classification, Administration, Release Profiles, and Industrial Approach

This work is aimed at providing a description of the complex world of drug carriers, starting from the description of this particular market in terms of revenue. Then, a brief overview of several types of conventional and innovative drug carrier systems has been included. The types of administration routes were also analyzed, with a critical and qualitative comment on drug release kinetics and drug profile shapes. Carriers were classified according to their ability to provide a prolonged and targeted release. The concept of the therapeutic window has been presented, providing advantages of having pulsed drug release to avoid side effects to target tissues. A critical comment on the use of conventional and innovative techniques for the production of drug carriers by large industrial companies has been proposed. As a final attempt for this work, an overall unique schematization of a drug carrier production process has been added, highlighting the necessity to create a strong double link among world-requested versatility of drug carriers for human applications and the newly developed industrial processes.

Enhancement of wastewater treatment by underwater superelastic fiber-penetrated lamellar monolith

During the removal of pollutants from wastewater, the underwater compressibility of three-dimensional biomass materials is the main factor determining their properties and service life. To construct a chitosan (CS)-based material with underwater superelasticity, a bidirectional freezing technique was used to introduce bamboo fibers (BFs) as bridges between CS lamellae to form a biomimetic CS/BFs monolith with an architecture similar to Thalia dealbata stems. BFs completely penetrated CS lamellae from the top down, which served as springs to dampen the elastic deformation during compressive cycles. After 10,000 underwater compressive cycles at 60% strain, the plastic deformation was negligible, and after 100 cycles at 90% strain, the monolith retained 93.8% of the maximum stress. Moreover, the CS/BFs monolith was loaded with CaCO₃ nanoparticles via compression-release-compression to obtain a CS/BFs/CaCO₃ monolith that exhibited excellent water purification capabilities. The CS/BFs/CaCO₃ monolith removed water-soluble dyes, heavy-metal ions, and emulsified oils from water with a high separation efficiency by simple squeezing and pumping methods. The novel pumping technology using the CS/BFs/CaCO₃ monolith provides a facile and rapid method to separate oil-in-water emulsions (maximum water flux of 11,776.9 L m^-2 h^-1). Therefore, the CS/BFs/CaCO₃ monolith with underwater superelasticity has great potential applications for wastewater treatment.

Synthesis and Characterization of Spherical Calcium Carbonate Nanoparticles Derived from Cockle Shells

Cockle shells are a natural reservoir of calcium carbonate (CaCO3), which is widely used in bone repair, tissue scaffolds, and the development of advanced drug delivery systems. Although many studies report on the preparation of CaCO3, the development of a nanosized spherical CaCO3 precursor for calcium oxide (CaO) that is suitable to be incorporated in dental material was scarce. Therefore, this study aimed to synthesize a nanosized spherical CaCO3 precursor for CaO derived from cockle shells using a sol–gel method. Cockle shells were crushed to powder form and mixed with hydrochloric acid, forming calcium chloride (CaCl2). Potassium carbonate (K2CO3) was then fed to the diluted CaCl2 to obtain CaCO3. The effect of experimental parameters on the morphology of CaCO3, such as volume of water, type of solvents, feeding rate of K2CO3, and drying method, were investigated using field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry (XRD), Brunauer–Emmett–Teller surface area analysis, and thermogravimetric analysis. Optimized CaCO3 was then calcined to form CaO. XRD analysis of CaCO3 nanoparticles was indicative of the formation of a calcite phase. The well-structured spherical shape of CaCO3 was obtained by the optimum condition of the addition of 50 mL of water into CaCl2 in ethanolic solution with a 1 h feeding rate of K2CO3. Less agglomeration of CaCO3 was obtained using a freeze-drying technique with the surface area of 26 m2/g and average particle size of 39 nm. Spherical shaped nanosized CaO (22–70 nm) was also synthesized. The reproducibility, low cost, and simplicity of the method suggest its potential applications in the large-scale synthesis of the nanoparticles, with spherical morphology in an industrial setting.

Effects of amino acids on conversion of calcium carbonate to hydroxyapatite

Conversion of calcium carbonate (calcite; CC) to hydroxyapatite (HAp) was examined when the CC particles of sub μm size were soaked at 37 °C for up to 10 d in 0.15 M K2HPO4 (20 ml), whose pH was set to 3-12. Here, the solution contained amino acids, such as glutamine (Glu), arginine (Arg), and glycine (Gly), and their content varied from 0-1.0 g per ml of solution. From the X-ray diffraction (XRD) intensity of the 104 and 211 diffractions of calcite and apatite, respectively, it was seen that the presence of the amino acids promoted the conversion. This was supported by the thermogravimetry (TG) results. The highest promotion was observed at 0.5 g addition of amino acids to the phosphate solution, while Glu showed the highest promotion among the amino acids and Gly the lowest. A scanning electron microscopy study indicated that petal-like HAp nano-crystallites covered the entire surface of the CC particles when they were soaked in the phosphate solution with 0.1 g or more of amino acid for 10 d. The XRD intensity ratio 104(CC)/211(HAp) indicated greater CC to HAp conversion in the solutions at pH 3 and 6 than in the more alkaline solutions. This was attributed to the dissolution of CC in the acidic solutions, which was confirmed by bubbling in these solutions.

A selected bacterial strain for the self-healing process in cementitious specimens without cell immobilization steps

The use of microorganisms capable of mediating the bioprecipitation process can be an important application in the self-healing processes of cement specimens. Thus, the present study identified and evaluated five Bacillus strains for potential application in the protocol of self-healing via bioprecipitation. Cell growth, enzyme production, and kinetic parameters conditions were evaluated during the fermentation process. Based on the analysis of 16S rDNA in conjunction with biochemical testing, results demonstrate that the strains are either Bacillus cereus or Bacillus thuringiensis. Strategically it was found that the addition of glycerol to fermentative medium was essential to increase the bacterial concentration (≈ 4.2 × 10⁷ cells mL^-1) and production of the enzyme urease (≈ 3.623,2 U.mL^-1). The addition of this medium after 40 days of fermentation promoted the self-healing of cracks and increased compressive strength in ≈ 14.2% of the cementitious specimens; therefore, increasing the sustainability and engineering properties of cement-based materials.

CaCO3 crystals as versatile carriers for controlled delivery of antimicrobials

CaCO₃ crystals have been known for a long time as naturally derived and simply fabricated nano(micro)-sized materials able to effectively host and release various molecules. This review summarises the use of CaCO₃ crystals as versatile carriers to host, protect and release antimicrobials, offering a strong tool to tackle antimicrobial resistance, a serious global health problem. The main methods for the synthesis of CaCO₃ crystals with different properties, as well as the approaches for the loading and release of antimicrobials are presented. Finally, prospects to utilize the crystals in order to improve the therapeutic outcome and combat antimicrobial resistance are highlighted. Ultimately, this review intends to provide an in-depth overview of the application of CaCO₃ crystals for the smart and controlled delivery of antimicrobial agents and aims at identifying the advantages and drawbacks as well as guiding future works, research directions and industrial applications.

ROS-responsive capsules engineered from EGCG-Zinc networks improve therapeutic angiogenesis in mouse limb ischemia

The successful treatment of limb ischemia requires that promote angiogenesis along with microenvironment improvement. Zinc ions have been reported to stimulate angiogenesis, but application was limited to the toxicity concerns. We hypothesized that zinc based metal-EGCG capsule (EGCG/Zn Ps) can achieve sustained release Zn²⁺ resulting in reduced toxicity and improve angiogenesis as well as the improvement of microenvironment by ROS scavenging of EGCG. The surface morphology, zeta potential, infrared absorbance peaks and zinc ion release profile of the EGCG/Zn Ps were measured. In vitro, EGCG/Zn showed significantly antioxidant, anti-inflammatory and induced cell migration effect. In addition, EGCG/Zn Ps enabled the sustained release of zinc ions, which reduced cytotoxicity and enhanced the secretion of vascular endothelial growth factor (VEGF) in vitro and in vivo. In mouse models of limb ischemia, EGCG/Zn Ps promoted angiogenesis and cell proliferation in ischemic tissues. Moreover, EGCG/Zn Ps group exhibited the most significant recovery of limb ischemic score, limb temperature and blood flow than other groups. In conclusion, EGCG/Zn Ps is a safe and promising approach to combine the merit of Zn²⁺ and EGCG, thus enabling the direct application to limb ischemia.

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Metal-polyphenol networks have been firstly applied in the Limb ischemic disease.

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EGCG improve the microenvironment of ischemic whereas Zinc exerts angiogenic property.

•The slowly release of zinc ions were achieved, resulting in better biocompatibility.

Investigation of calcium carbonate synthesized by steamed ammonia liquid waste without use of additives

The aim of this work is to study the effect of reaction conditions using steamed ammonia liquid waste without the use of additives on the crystallization of calcium carbonate. CaCO₃ was prepared by steamed ammonia liquid waste (CaCl₂) and (NH₄)₂CO₃ solution. The produced crystals were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR) and X-ray diffraction (XRD). We have investigated the effect of the concentration of reactants, stirring speed, Ca²⁺ : CO₃²⁻ ratio, aging time and adding mode on the particle size and size distribution, final morphology and polymorph of calcium carbonate crystals during precipitation. The influence of concentration of reactants, stirring speed, Ca²⁺ : CO₃²⁻ ratio, aging time and adding mode on the morphology, size and polymorph of CaCO₃ particles and possible formation mechanism were discussed. The exploration provides the possibility for large-scale synthesis of CaCO₃ materials with controllable morphology and crystallographic structure by steamed ammonia liquid waste without use of additives at room temperature.

The aim of this work is to study the effect of reaction conditions using steamed ammonia liquid waste without the use of additives on the crystallization of calcium carbonate.

Magnetically modified hydroxyapatite nanoparticles for the removal of uranium (VI): Preparation, characterization and adsorption optimization

Recently, magnetically modified nanomaterials have gained a great interest in the field of wastewater remediation. In this regard, the present work introduces a facile microwave-assisted pathway for the preparation of magnetically modified hydroxyapatite nanoparticles (MNHA) and evaluates its adsorption capability towards the removal of uranium (VI) ions from wastewaters. The prepared magnetic nanocomposite went through a full characterization procedure using different techniques, such as transmission electron microscope (TEM), X-ray diffraction (XRD), FT-IR, Brunauer-Emmett-Teller (BET) surface area measurements and magnetization curve. Involvement of the prepared MNHA in the remediation of wastewater containing U(VI) ions was investigated and the factors that influence the adsorption capacity were considered and optimized. The adsorption's optimum pH was found to be 5.0 and equilibrium was attended after 120 min. A maximum adsorption capacity of 310 mg/g was achieved after 120 min at 25 °C. The experimental data were well explained by Langmuir adsorption isotherm model. Kinetically, the adsorption process follows the pseudo-second order model. Thermodynamically, it is endothermic, irreversible and spontaneous adsorption process. Removal of U(VI) ions was found to take place via complex formation between the phosphate groups on the adsorbent and uranyl ions. The recovery of U(VI) ions from MNHA beads and the reusability of the spent beads were also explored. It was concluded that the prepared MNHA nanocomposite is simple, fast, ecofriendly adsorbent for the removal of U(VI) ions from water with excellent adsorption capacity.

HAp@GO drug delivery vehicle with dual-stimuli-triggered drug release property and efficient synergistic therapy function against cancer

Nanoscale hydroxyapatite (HAp) is an optimal candidate material in biomedical area for its good biocompatibility and bioactivity. In this study, HAp nanorods are prepared via hydrothermal method and combined with monolayered graphene oxide (GO). The obtained HAp@GO with excellent biocompatibility is revealed to have high drug loading capacity (698.7 μg/mg) for anticancer drug doxorubicin (DOX) and efficient photothermal conversion property. And the drug release property of DOX loaded HAp@GO (HAp@GO-DOX) is demonstrated to be controlled by pH and near-infrared light, which is favorable for cancer therapy. in vitro studies on cancer therapy demonstrate that the combined treatment, compared with either chemotherapy or photothermal therapy alone, has better synergistic therapeutic effect. These findings prove the great potential application of the nanocomposites for cancer therapy.

Stimuli-Responsive DNA Microcapsules for SERS Sensing of Trace MicroRNA

In this work, one stimuli-responsive DNA microcapsule was designed to combine duplex-specific nuclease (DSN) amplification strategy and surface-enhanced Raman spectroscopy (SERS) technology for sensitive detection of microRNA 155 (miRNA 155). First, toluidine blue (TB) as Raman dye and CaCO₃ as core templates co-precipitated to form TB@CaCO₃ composite. Then, DNA networks were layer by layer constructed with oligonucleotide layers cross-linked by linker ssDNA L to lock TB@CaCO₃ inside. In the presence of ethylenediaminetetraacetic acid, the core CaCO₃ would be dissolved to form TB-loading DNA microcapsule. With target miRNA 155-induced DSN signal amplification, a large amount of simulative target ssDNA D was obtained, which can completely complement with the linker L on the DNA networks, destroying the microcapsule to release TB and obtain a strong Raman signal. So by this smart design, a SERS platform was fabricated on the basis of the stimuli-responsive DNA microcapsule to detect miRNA 155 from 1 fM to 10 nM with a detection limit of 0.67 fM. In the present study, the programmable property and rapid response speed of DNA microcapsule, which helped in fabrication of a new potential biosensing technology for miRNA detection that is anticipated to be applied for clinical diagnosis.

Yolk @ cage-Shell Hollow Mesoporous Monodispersion Nanospheres of Amorphous Calcium Phosphate for Drug Delivery with High Loading Capacity

In this paper, yolk-shell hollow nanospheres of amorphous calcium phosphate (ACP) are prepared, and its loading capacity is investigated by comparing with that of solid-shell hollow structure ACP and cage-shell hollow structure ACP. Results show that the products are yolk @ cage-shell of ACP with large shell's pores size (15-40 nm) and large cavity volume. Adsorption results show that the loading capacity of yolk @ cage-shell hollow spherical ACP is very high, which is more than twice that of hollow ACP and 1.5 times of cage-like ACP. The main reasons are that the big shell's pore size contributes the large molecular doxorubicin hydrochloride (DOX · HCl) to enter the inner of hollow spheres easier, and the yolk-shell structure provides larger interior space and more adsorption sites for loading drugs.

Synthesis, characterization, and cytocompatibility of potential cockle shell aragonite nanocrystals for osteoporosis therapy and hormonal delivery

Calcium carbonate is a porous inorganic nanomaterial with huge potential in biomedical applications and controlled drug delivery. This study aimed at evaluating the physicochemical properties and in vitro efficacy and safety of cockle shell aragonite calcium carbonate nanocrystals (ANC) as a potential therapeutic and hormonal delivery vehicle for osteoporosis management. Free and human recombinant parathyroid hormone 1-34 (PTH 1-34)-loaded cockle shell aragonite calcium carbonate nanocrystals (PTH-ANC) were synthesized and evaluated using standard procedures. Transmission electron microscopy and field emission scanning electron microscopy results demonstrated highly homogenized spherical-shaped aragonite nanocrystals of 30±5 nm diameter. PTH-ANC had a zeta potential of -27.6±8.9 mV. The encapsulation efficiency of the formulation was found to be directly proportional to the concentrations of the drug fed. The X-ray diffraction patterns revealed strong crystallizations with no positional change of peaks before and after PTH-ANC synthesis. Fourier transform infrared spectroscopy demonstrated no detectable interactions between micron-sized aragonite and surfactant at molecular level. PTH-ANC formulation was stabilized at pH 7.5, enabling sustained slow release of PTH 1-34 for 168 h (1 week). A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytocompatibility assay in Human Foetal Osteoblast Cell Line hFOB 1.19 showed that ANC can safely support osteoblast proliferation up to 48 h whereas PTH-ANC can safely support the proliferation at 72 h and beyond due to the sustained slow release of PTH 1-34. It was concluded that due to its biogenic nature, ANC is a cytocompatible antiosteoporotic agent. It doubles as a nanocarrier for the enhancement of efficacy and safety of the bone anabolic PTH 1-34. ANC is expected to reduce the cost, dosage, and dose frequency associated with the use of PTH 1-34 management of primary and secondary forms of osteoporosis.

Improving Targeting of Metal-Phenolic Capsules by the Presence of Protein Coronas

Particles adsorb proteins when they enter a physiological environment; this results in a surface coating termed a "protein corona". A protein corona can affect both the properties and functionalities of engineered particles. Here, we prepared hyaluronic acid (HA)-based capsules through the assembly of metal-phenolic networks (MPNs) and engineered their targeting ability in the absence and presence of protein coronas by varying the HA molecular weight. The targeting ability of the capsules was HA molecular weight dependent, and a high HA molecular weight (>50 kDa) was required for efficient targeting. The specific interactions between high molecular weight HA capsules and receptor-expressing cancer cells were negligibly affected by the presence of protein coronas, whereas nonspecific capsule-cell interactions were significantly reduced in the presence of a protein corona derived from human serum. Consequently, the targeting specificity of HA-based MPN capsules was enhanced due to the formation of a protein corona. This study highlights the significant and complex roles of a protein corona in biointeractions and demonstrates how protein coronas can be used to improve the targeting specificity of engineered particles.

Polymer Capsules for Plaque-Targeted In Vivo Delivery

Targeted polymer capsules can selectively bind to unstable plaques in mice after intravenous injection. Different formulations of the capsules are explored with a synthetic/biopolymer hybrid capsule showing the best stability and small-molecule drug retention. The synthetic polymer is composed of pH-sensitive blocks (PDPA), low-binding blocks (PEG), and click-groups for postfunctionalization with targeting peptides specific to plaques.