Spherical CaCO3 Particles Research Articles

Synthesis of High-Precision Sub-Micron CaCO3 Anticancer Drug Carriers from Coral Remains

Calcium carbonate (CaCO3) particles have attracted increasing attention as a promising material for drug delivery systems. In this study, coral remains were utilized as a raw material for a novel drug carrier. A series of pre-treatment and parameter experiments were conducted to synthesize sub-micron spherical CaCO3 particles. The CaCO3 particles exhibited uniform size distribution, with the minimum mean size being only 344 nm. The effects on the CaCO3 crystal phases and particle sizes were also discussed in this study. Drug loading experiments were also conducted to assess the feasibility of the CaCO3 drug carrier. We loaded TRITC-Dextran into CaCO3 particles for the simulation experiments. The loading capacity reached up to 9.6 wt.%, which was as high as common drug carriers such as liposomes. In this study, we aimed not only to tackle the local environmental issues caused by coral remains, but also to synthesize a suitable drug carrier for cancer therapy using the outstanding properties and low cost of CaCO3.

Polyelectrolyte Microcapsules as a Tool to Enhance Photosensitizing Effect of Chlorin E6

Introduction: Photodynamic therapy is a promising method of tumors treatment using photosensitizers and light of a certain wavelength. PS modification improves and enhances the phototoxic effect with decreased dark cytotoxicity. Materials and Methods: We compared the photosensitizing effect of polyelectrolyte microcapsules with chlorin E6 (ClE6) and free ClE6 at equivalent concentrations on murine fibroblast culture L929 using in vitro tests. Microcapsules were prepared layer by layer, sequentially depositing oppositely charged polyelectrolytes onto spherical CaCO3 particles. Cellular uptake of capsules was assessed using confocal microscopy. MTT test was used for a study of cell viability, and the relative amount of ROS was determined by the fluorescent method. Results: Microcapsules with ClE6 (in all tested concentrations) after exposure to red light (660 nm) reduced cell viability from 20% to 5%, while these capsules did not have dark cytotoxicity. Free ClE6 at the same concentrations as in the capsules after irradiation reduced viability from 65% to 35%. The level of ROS in the group of cells with capsules was 2 times higher compared to the group with CLE6. Discussion: The most probable mechanism of toxicity increase is creation of a higher ROS concentration and effect localization in the area of microcapsule interaction with the cell membrane. ROS production activation may stem from capsules providing a higher local PS concentration in the cell or nearby than the drug’s free form. Conclusion: The inclusion of chlorin E6 in polymer capsules reduced dark toxicity and increased the photosensitizing effect compared to the free form of ClE6.

N-(2-hydroxyl)-propyl-3-trimethylammonium chitosan chloride/carboxymethyl cellulose films filled with in-situ crystallized calcium carbonate

The research and development of substitutes for petroleum-based plastics has become a hot topic. The N-(2-hydroxyl)-propyl-3-trimethylammonium chitosan chloride (HTCC, 10 wt%)/sodium carboxymethyl cellulose (CMC) films have showed enhanced mechanical properties, which also provide a potential substitute to petroleum-based plastics. In this paper, calcium carbonate was crystallized (cry-CaCO3) in HTCC/CMC film-forming solutions, and the effects of the cry-CaCO3 particles on HTCC/CMC film properties including microstructures, mechanical properties, thermal stability, whiteness, and wettability were characterized. An HTCC/CMC film with commercially available CaCO3 (com-CaCO3) was used as a control. The results showed that the cry-CaCO3 promoted the homogeneous distribution of the HTCC/CMC matrix and significantly improved mechanical properties, but showed little effect on the thermal stability, whiteness and wettability of the films. To reveal the affecting mechanism of cry-CaCO3 on HTCC/CMC film properties, the cry-CaCO3 particles were isolated from film-forming solutions and characterized by scanning electron microscope (SEM), powder X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA) methods. The results showed that the HTCC/CMC matrix modulated spherical CaCO3 particles, and the macromolecules were encapsulated in cry-CaCO3 particles, decreasing their adhesion to the HTCC/CMC matrix while increasing their distribution in the HTCC/CMC matrix. The strong electrostatic, hydrogen bonding and flexible interaction between CMC and cry-CaCO3 particles played a key role in improving the mechanical properties of HTCC/CMC films.

DRY SLIDING FRICTION and WEAR PROPERTIES of CACO3 NANOPARTICLE FILLED EPOXY/CARBON FIBER COMPOSITES

Metal/Fiber reinforced polymer (FRP) composite joints with lower friction coefficients are increasingly replacing metal-metal couples in a variety of fields. The wear performance of metal / FRP tribo-contacts becomes a key design parameter for their service life and the improvement in the wear performance of metal-FRP friction pairs is needed to extend their applications. In this paper, sliding friction and wear characteristics of carbon fiber reinforced epoxy composites against metallic counterparts were investigated. Tests were performed on a ball-on-disk tester at a constant normal load and velocity against chromium steel under dry ambient. Moreover, CaCO3 nano reinforcements were introduced into carbon/epoxy composites to improve their wear performance. The coefficient of friction (65%) and the specific wear rate (75%) were drastically reduced with the addition of CaCO3 nano reinforcements. Worn surfaces were analyzed by scanning electron microscopy (SEM) to evaluate the wear mechanisms. It was concluded that the abrasion dominated wear mechanism of the bare carbon/epoxy composites transformed into adhesion for the multi-scale composites which are responsible for the increased wear performance. This impact was most likely attributed to two main factors: spherical CaCO3 particles facilitate sliding and act as a solid lubricant.

Effect of particle morphology on mechanical properties of liquid marbles

In order to better understand the influence of the shape of solid particles on the stability of liquid marbles, we investigated liquid marbles stabilized by hydrophobized calcium carbonate particles with spherical and rod-shaped morphologies. Static properties, such as the effective surface tension, and the dynamic behavior i.e. the compression-decompression features for several cycles of the liquid marbles were investigated. Liquid marbles stabilized with spherical CaCO3 particles show an elastic response to mechanical deformation almost up to collapse. In contrast, liquid marbles prepared with rod-like particles exhibit a more plastic response to compression. It is concluded that the main differences in behavior of the prepared liquid marbles arise from how the solid particles can arrange/orient at the air/water interface.

Preparation and characterization of calcium carbonate microspheres and their potential application as drug carriers.

The influence of lecithin from egg yolk (LE) on calcium carbonate (CaCO3) biomineralization was investigated. In the present study, spherical CaCO3 particles were synthesized via coprecipitation in the presence of LE. LE multilamellar liposomes were first tuned by sonication to provide better control over the nucleation of CaCO3. Subsequently, monodisperse microspheres ~2µm in size were generated by controlling the aggregation and growth of CaCO3 under appropriate concentrations of LE. In contrast to unstable vaterite, the microspheres generated in aqueous solution remained stable for at least 10days without transforming into calcite, due to the strong interaction between the LE and calcium ions. The microspheres as drug carriers of doxorubicin (DOX) were assessed and were observed to have a good encapsulation efficiency, sustained drug release without a burst release and notable pH sensitivity. In addition, invivo tumor inhibition examination demonstrated that DOX‑loaded CaCO3 microspheres formulation had more superior efficacy to significantly restrain tumor growth. These novel LE/CaCO3 hybrids may provide novel options for various biomedical applications.

Controlled synthesis, characterization and application of hydrophobic calcium carbonate nanoparticles in PVC

Modification of calcium carbonate particles with surfactant significantly improves the properties of polyvinyl chloride (PVC). Hydrophobic spherical CaCO3 particles were prepared in the presence of dodecyl dihydrogen phosphate (DDP) by a carbonation method. In the process, DDP was used as an organic substrate to induce the nucleation and growth of calcium carbonate. The operating parameters such as temperature and the dosage of the organic substrate were varied to study their influences on the active ratio and contact angle of calcium carbonate particles. The surface property of CaCO3 particles was changed from hydrophilic to hydrophobic when the dosage of DDP to CaCO3 changed from 0 to 2%. The contact angle of modified CaCO3 particles was 119.51°. Moreover, X-ray diffraction (XRD), FT-IR spectrums and thermogravimetry analysis (TGA) were employed to characterize the obtained products. The schematic illustration for interaction between the organic substrate and inorganic mineral in aqueous medium was showed in the end. The synthesized CaCO3 was applied to polyvinyl chloride (PVC) to improve its mechanical properties. The properties of PVC/CaCO3 composites have been tested such as tensile strength, impact strength, Young's modulus and SEM.

Biomimetic Controlling of CaCO3 and BaCO3 Superstructures by Zwitterionic Polymer

In this work, uniform calcium carbonate (CaCO3) and barium carbonate (BaCO3) crystals were synthesized under the control of poly(2-methacryloyloxyethylphosphorylcholine) (PMPC) via a simple gas–liquid diffusion reaction. Spherical CaCO3 particles with six smooth facets symmetrically distributed on the surface were prepared and systemically characterized by means of TEM, SEM, XRD, Raman, TGA, and FTIR. Time-resolved experiments showed the spherical calcite crystals were transformed from amorphous calcium carbonate (ACC) in the early stage and underwent a dissolution–recrystallization process in the later stage. For BaCO3, dumbbell-shaped crystals that were formed by the dendritic aggregation of rod-like subunits with six sides were generated. Both the morphologies of CaCO3 and BaCO3 crystals could be effectively tuned by changing the crystallization time and concentration of PMPC. Finally, a possible crystallization mechanism for the formation of CaCO3 and BaCO3 particles under the control of PMPC was proposed based on the experiments.

Preparation of micro-scaled multilayer capsules of poly-dimethyl-diallyl-ammonium chloride and sodium cellulose sulfate by layer-by-layer self-assembly technique

Novel homogeneous micro-scaled hollow polyelectrolyte capsules were prepared by using alternate adsorption of poly-dimethyl-diallyl-ammonium chloride (PDMDAAC) and cellulose sulfate sodium (NaCS) on calcium carbonate (CaCO3) template particles. The CaCO3 particles with various shapes were prepared by the reaction of potassium carbonate (K2CO3) with calcium chloride (CaCl2) in the presence of carboxylmethyl cellulose (CMC). The results showed that at a CMC concentration of 0.5g/L, smooth spherical CaCO3 particles were obtained, which were used as core templates. Thereafter four bilayers of PDMDAAC and NaCS polymer film were deposited on the CaCO3 cores. The film buildup was characterized by (i) microelectrophoresis; (ii) scanning electron microscopy (SEM); and (iii) thermogravimetric analysis (TGA). Hollow capsules were then prepared by exposing the coated CaCO3 particles to EDTA-Na. Finally the molecular weight cut-off (MWCO) of the microcapsules was determined by exposing the microcapsules to the E. coli cell lysate.

Dispersion of calcite by poly(sodium acrylate) prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization

Calcite is dispersed into nanoparticles with the use of polysodium acrylate, PAANa. The molecular weight distribution of PAANa greatly influences the characteristics of the dispersion. Near-monodisperse PAANa adsorbs irreversibly and totally onto the CaCO3 surface, but for polydisperse PAANa, a mass segregation occurs, where only chains with a selected molecular weight are adsorbed. With polydisperse samples, small spherical CaCO3 particles are generated in addition to calcite crystals. This bimodal dispersion is less viscous than the dispersion containing only calcite crystals.

Russia: Huber & International Paper — precipitated calcium carbonate

Calcium carbonate (CaCO3) crystal growth experiments in the presence of the polystyrene sulfonate were made at ambient temperature. This polyelectrolyte inhibits the crystal growth in all directions and modifies the crystal structure and morphology. Further, the unstable vaterite CaCO3 crystalline structure was stabilized in the precipitation medium in the presence of the polyelectrolyte. Thus, at moderate polyelectrolyte concentration, spherical CaCO3 particles are obtained having a smaller size compared to the rhombohedral particles obtained in the absence of the polyelectrolyte. By increasing the polyelectrolyte concentration, the CaCO3 particles mean size and size-polydispersity index decrease. The microelectrophoresis studies indicate that in the presence of the anionic polyelectrolyte, the CaCO3 particles are negatively surface charged. The results obtained indicate a correlation between the CaCO3 particle sizes, their surface charges and the equilibrium pH of the aqueous CaCO3 dispersion. Finally, the data obtained was used to throw light on the mechanism by which polymeric additives affect the morphology, size and crystalline structure of calcium carbonate CaCO3.

Preparation and microelectrophoresis characterisation of calcium carbonate particles in the presence of anionic polyelectrolyte

Abstract Calcium carbonate (CaCO3) crystal growth experiments in the presence of the polystyrene sulfonate were made at ambient temperature. This polyelectrolyte inhibits the crystal growth in all directions and modifies the crystal structure and morphology. Further, the unstable vaterite CaCO3 crystalline structure was stabilized in the precipitation medium in the presence of the polyelectrolyte. Thus, at moderate polyelectrolyte concentration, spherical CaCO3 particles are obtained having a smaller size compared to the rhombohedral particles obtained in the absence of the polyelectrolyte. By increasing the polyelectrolyte concentration, the CaCO3 particles mean size and size-polydispersity index decrease. The microelectrophoresis studies indicate that in the presence of the anionic polyelectrolyte, the CaCO3 particles are negatively surface charged. The results obtained indicate a correlation between the CaCO3 particle sizes, their surface charges and the equilibrium pH of the aqueous CaCO3 dispersion. Finally, the data obtained was used to throw light on the mechanism by which polymeric additives affect the morphology, size and crystalline structure of calcium carbonate CaCO3.

Formation and Growth of Amorphous Colloidal CaCO3 Precursor Particles as Detected by Time-Resolved SAXS

Time-resolved synchrotron small-angle X-ray scattering (SAXS) studies were performed to investigate the unseeded formation and growth of colloidal calcium carbonate particles. Equimolar aqueous solutions of CaCl2·2H2O and Na2CO3 were rapidly mixed in a stopped-flow apparatus, and SAXS data were recorded using an image-intensified CCD detector. It is shown that SAXS allows studying those processes in situ, with a very good time resolution. It can provide unsurpassed real-time information about the particle size, shape, polydispersity, inner structure, and density. In these studies, well-defined, spherical CaCO3 particles with colloidal dimensions up to ca. 270 nm and a remarkable uniformity in size could be observed. After a short nucleation period, the number density of the growing spheres remains constant. From the evaluation of the absolute scattering intensities, the particle mass density could be determined to be ca. 1.62 g/cm3, which is considerably lower than the density of the crystalline modificat...

Smooth and rough spherical calcium carbonate particles

Several studies dealing with crystallization of calcium carbonate (CaCO3) on solid surface [1] or in solution [2] have shown that the morphology and the growth of the crystal may be affected by the presence of foreign compounds or additives. Almost all such additives, which are organic or inorganic in nature, prevent or reduce the rate of CaCO3 crystallization from supersaturated solutions. Such studies are useful for many industrial applications, such as the production at large-scale of spherical CaCO3 particles with uniform size, and in preventing the precipitation of calcium carbonate in steam boilers. Furthermore in the biological mineralization, the calcium containing salts are the major constituents of mollusk shells. In these mineralized tissues, precipitation of oriented aragonite and calcite CaCO3 forms occur within polymeric tissues matrices. Acidic protein [3] which are located at the surfaces of the matrix interact from the solution with the growing CaCO3 crystals and are responsible for both nucleation and inhibition of crystallization. In the present work crystallisation of calcium carbonate (CaCO3) from supersaturated solutions and in the presence of polystyrene sulfonate (PSS1) and/or polystyrene-polyethylene oxide (SE10-30) copolymer has been investigated. The polyelectrolyte (PSS1) purchased from Aldrich and the copolymer (SE10-30), have molecular weights values equal to, respectively, 7×104 and 4000. The polystyrene and the polyethylene blocks of the copolymer SE 10-30 have molecular weights equal to, respectively, 1000 and 3000, and the sample is the same as used elsewhere [4]. Supersaturated solutions for crystal growth experiments were prepared by rapid addition of equal volumes of sodium carbonate (Na2CO3) to calcium nitrate (Ca(NO3)2 4H2O) solutions. In the case of the additives, the polymers aqueous solutions of PSS1 and/or SE10-30 were first added to calcium nitrate solution and the mixtures were stirred for about 15 min prior the rapid addition of Na2CO3 solutions. The crystal growth experiments were made at ambient temperature in a water-jacketed Pyrex glass vessel of 300-ml capacity. The precipitated CaCO3 crystals were recovered by filtration and the dried crystals were gold coated in vacuum and examined by scanning electron microscope at magnifications from ×2000 to 30 000. The crystallization of the calcium carbonate in the presence of SE10-30 additive, Fig. 1, results into agglomerates of primary particles with a size of few microns and rhombohedral morphologies. In the presence of the PSS1, Fig. 2, we obtain CaCO3 crystal having smooth spherical shape. Rough spherical particles, Fig. 3, were obtained in the presence of the PSS1/SE1030 polymer-copolymer mixture. The CaCO3 crystal structures obtained by the X-ray analyses were calcite when the additive is the SE10-30 copolymer and vaterite in the presence of the PSS1. The crystal structure obtained in the presence of the mixture PSS1/SE10-30 was vaterite. Further, the measurements of the time dependence of the conductivity indicates that the polyelectrolyte PSS1 has a retarding while the copolymer SE10-30 has an