CaCO3 Core Research Articles

Calcium-containing disk pattern from microspheres of chitosan with alginate

Microstructures bridge the molecular and the macroscopic scales. Disk-patterned microstructures obtained from microcapsules in this work are assembled through layer-by-layer which allowed depositing the natural polysaccharides chitosan (CS) and sodium alginate (SA) on porous CaCO3 microparticles. Besides CS and SA assembled outside CaCO3 microparticles, some CS and SA were also encapsulated by permeation in the pores of CaCO3. During the dissolution of CaCO3, the Ca2+ cations from decomposed CaCO3 were found to interact with alginate (AL) anions and to form Ca2+–AL scaffolds. The adhesion arising from the OH groups in polysaccharides to solid surfaces was attributed to the disk-patterned microstructures. The calcium content (2.290×10−10mg) in each (CS/SA)4 microstructure amounts to about 1% of the total mass of the CaCO3 core. This work thus demonstrates the interaction between the decomposed core elements and the polysaccharides existing both inside and outside the porous cores. Such microstructures containing both Ca2+ and natural polysaccharides have potential applications in biological and medical systems.

Avidin/PSS membrane microcapsules with biotin-binding activity

Polyelectrolyte microcapsules with avidin-poly(styrene sulfonate) (PSS) membrane were prepared by a layer-by-layer deposition technique. The uptake and release of biotin-labeled fluorescein (b-FITC) as well as immobilization of biotin-labeled glucose oxidase (b-GOx) to the microcapsule were studied. The polyelectrolyte microcapsules were prepared by coating the surface of calcium carbonate (CaCO3) microparticles with an avidin/PSS multilayer membrane, followed by dissolution of CaCO3 core in an ethylenediaminetetraacetic acid solution. Inner and outer poly(allylamine)/PSS films were required to isolate the microcapsules, whereas microcapsules could not be formed without the support. The uptake of b-FITC into the microcapsule was highly enhanced through a strong binding of b-FITC to avidin as compared with the uptake of biotin-free FITC. Release of b-FITC from the microcapsule was accelerated upon addition of biotin due to a competitive binding of the added biotin to the binding site of avidin. Similarly, the surface of microcapsule was modified with b-GOx with retaining its catalytic activity.

Templated Ultrathin Polyelectrolyte Microreservoir for Delivery of Bovine Serum Albumin: Fabrication and Performance Evaluation

The aim of the study was to develop ultrathin polyelectrolyte microreservoir (UPM) using two combinations of synthetic/synthetic (S/s; poly(allylamine hydrochloride) (PAH)/sodium poly(styrenesulfonate)) and synthetic/natural (S/n; PAH/sodium alginate) polyelectrolytes over spherical porous CaCO(3) core particles (CP) followed by core removal and to evaluate its biocompatibility and integrity of loaded model protein bovine serum albumin (BSA). A novel process for synthesis of CP was developed to obtain maximum yield of monodisperse vaterite (spherical) polymorph. The prepared UPM was characterized for surface morphology, layer-by-layer growth, pay load efficiency, integrity of BSA, as well as viability and cell adhesion using murine J 774 macrophages (Φ). In vitro release profile revealed that both S/s and S/n UPM were able to provide sufficient diffusion barrier to release protein at physiological pH. It has been observed that S/n UPM are fully biocompatible due to obvious reason of using natural polymer. In a separate experiment, the S/s UPM surface was modified with pluronic F-68 to tune biocompatibility which provides evidences for safety and tolerability of the S/s UPM as well. In nutshell, the proposed system could successfully be used for the delivery of proteins, and moreover, the system can be tailored to impart desired properties at any stage of layering especially in terms of drug release and to retain the integrity of proteins.

Preparation of avidin-containing polyelectrolyte microcapsules and their uptake and release properties

Avidin-containing polyelectrolyte microcapsules were prepared by a layer-by-layer deposition technique and uptake and release of biotin-labelled fluorescein (b-FITC) was studied. The polyelectrolyte microcapsules were prepared by coating the surface of calcium carbonate (CaCO3) microparticles containing avidin-poly(styrene sulfonate) (PSS) conjugate, followed by dissolution of CaCO3 core in an ethylenediaminetetraacetic acid solution. Release of avidin from the microcapsules was markedly suppressed due to formation of a high molecular weight of avidin-PSS conjugate in the microcapsules. The uptake of b-FITC into the microcapsules was highly enhanced through a strong binding of b-FITC to avidin, as compared to the uptake into avidin-free microcapsules. Release of b-FITC from the microcapsules was accelerated upon addition of biotin, 2-iminobiotin, or lipoic acid in the solution due to the competitive binding of the additives to the binding site of avidin.

インスリンを含有する高分子ミクロカプセルの調製および糖応答性

Sugar-sensitive microcapsules containing insulin were prepared by a layer-by-layer (LbL) deposition of alginic acid (AGA) and phenylboronic acid-modified poly(allylamine) (PBA-PAH) on the surface of a calcium carbonate (CaCO3) microparticle in which insulin had been embedded, followed by dissolution of the CaCO3 core. The microcapsules thus prepared were stable at pH 7.0-9.0. In the presence of 10-100 mM fructose or glucose, the release of insulin was significantly enhanced depending on solution pH and sugar concentration. The sugar-triggered release of insulin was explained on the basis of decomposition of the microcapsules, which in turn was caused by competitive binding of added sugar to the phenylboronic acid moieties in the LbL film.

Mechanism of calcium accumulation in acetate-fed aerobic granule

High calcium content has been widely reported in acetate-fed aerobic granules, but the reason behind this is unclear yet. By SEM-energy dispersive X-ray mapping analysis, this study showed that the majority of calcium was presented in the central part of the acetate-fed aerobic granule, and the granule shell part was nearly calcium-free. The elemental analysis of calcium ions coupled with the chemical titration of carbonate further revealed that the calcium ions that accumulated in the acetate-fed aerobic granule mainly existed in the form of calcium carbonate (CaCO3). The formation of the CaCO3 appeared to be highly dependent on the size of the aerobic granule, i.e., the CaCO3 precipitation was found only in aerobic granules with radiuses larger than 0.5 mm. These experimental observations with regard to the formation of CaCO3 in the acetate-fed aerobic granule were further confirmed by the model simulation, which was based on the principles of mass diffusion and carbonate dissociation in liquid phase. This study for the first time showed that the size of the acetate-fed aerobic granule would indeed play an essential role in the CaCO3 formation, and provided experimental evidence that a crystal CaCO3 core was not necessarily required for granulation.

Stimuli‐Responsive Multilayered Hybrid Nanoparticle/Polyelectrolyte Capsules

AbstractGold nanoparticles (AuNP) with carboxyl groups on their surface were used in combination with PAH for the layer‐by‐layer coating of CaCO3 microparticles, followed by the dissolution of the CaCO3 core. SEM, TEM, and confocal microscopy are used to characterize the hybrid nanoparticles/polyelectrolyte capsules. As the AuNP have carboxyl groups on their surface, their charge density is pH dependent; therefore, the capsules exhibit a pH‐dependent swelling and can be deconstructed both at low and high pH. By covalent cross‐linking of the carboxyl groups of the AuNP and the amino groups of the PAH, it is possible to suppress the pH‐responsive behavior. AuNP are used as activation centers using IR light and this ability is used to release encapsulated material from the nanoparticles/polyelectrolyte capsules as well as for the enhancement of detection and imaging of such capsules by Raman microspectrosopy.magnified image

Equilibrium Distribution of Permeants in Polyelectrolyte Microcapsules Filled with Negatively Charged Polyelectrolyte: The Influence of Ionic Strength and Solvent Polarity

The effects of ionic strength and solvent polarity on the equilibrium distribution of fluorescein (FL) and FITC-dextran between the interior of polyelectrolyte multilayer microcapsules filled with negatively charged strong polyelectrolyte and the bulk solution were systematically investigated. A negatively charged strong polyelectrolyte, poly(styrene sulfonate) (PSS), used for CaCO3 core fabrication, was entrapped inside the capsules. Due to the semipermeability of the capsule wall, a Donnan equilibrium between the inner solution within the capsules and the bulk solution was created. The equilibrium distribution of the negatively charged permeants was investigated by means of confocal laser scanning microscopy as a function of ionic strength and solvent polarity. The equilibrium distribution of the negatively charged permeants could be tuned by increasing the bulk ionic strength to decrease the Donnan potential. Decreasing the solvent polarity also could enhance the permeation of FL, which induces a sudden increase of permeation when the ethanol volume fraction was higher than 0.7. This is mainly attributed to the precipitation of PSS. A theoretical model combining the Donnan equilibrium and Manning counterion condensation was employed to discuss the results.