CS Microspheres Research Articles

Preparing high-performance microspheres based on the chitosan-assisted dispersion of reduced graphene oxide in aqueous solution for bilirubin removal

The removal of excess bilirubin from blood is of great clinical importance. Reduced graphene oxide (rGO) is often used to efficiently remove bilirubin. However, thin rGO pieces tend to aggregate in the aqueous phase because they are hydrophobic. In this context, we propose an effective strategy based on the chitosan-assisted (CS-assisted) dispersion of rGO to produce high-performance bilirubin-adsorbing microspheres. CS possesses a hydrophobic CH structure, which offers strong hydrophobic interactions with rGO that assist its dispersion, and the large number of hydrophilic sites of CS increases the hydrophilicity of rGO. CS serves as a dispersant in a surfactant-like manner to achieve a homogeneous and stable CS/rGO dispersion by simply and gently stirring CS and rGO in a LiOH/KOH/urea/H2O system. Subsequently, CS/rGO hybrid microspheres were prepared by emulsification. CS ensures blood compatibility as a base material, and the entrapped rGO contributes to mechanical strength and a high adsorption capacity. The CS/rGO microspheres exhibited a high bilirubin adsorption capacity (215.56 mg/g), which is significantly higher than those of the rGO and CS microspheres. The determined mass-transfer factors revealed that the rich pores of the CS/rGO microspheres promote mass transfer during bilirubin adsorption (equilibrium is almost achieved within 30 min). The CS/rGO microspheres are promising candidates for bilirubin removal owing to a combination of high strength, blood compatibility, and high adsorption capacity.

A new strategy to prepare n-HA/CS composite scaffolds with surface loading of CS microspheres

A nano-hydroxyapatite/chitosan (n-HA/CS) scaffold loading with CS microspheres was developed in this study. First, CS microspheres with an average diameter of ∼57 μm were prepared by cross-linking, and a three-dimensional (3D) printing technology was used to fabricate n-HA/CS porous scaffolds with an average pore size and porosity of 454 ± 51 μm and 60.71%, respectively. Then, the n-HA/CS scaffolds were immersed in a solution of CS microspheres and cross-linked by vanillin. The structure, porosity, composition, and cellular behavior of the CS-microsphere-loaded scaffolds were investigated. In vitro cell experiments showed that the CS microspheres on the scaffolds could effectively promote the adhesion and growth of cells on the scaffolds, suggesting that the CS microspheres and the scaffolds have good cytocompatibility. The composite scaffolds were implanted in the back muscles of rabbits for 3, 6, and 9 weeks, and the results of subsequent SEM and H&E staining analyses demonstrated that both the n-HA/CS scaffolds and the loaded CS microspheres had good biocompatibility and gradually degraded over time, where the microspheres were gradually released from the scaffolds. The strategy developed in this study for loading microspheres on scaffolds has promising prospects for future clinical applications of enhancing bone defect repair or implant integration.

The Preparation and Medical Applications of Chitosan Microspheres

Background: The microsphere prepared from chitosan, a natural polymeric material, has attracted considerable attentions due to the natural instincts of chitosan and microsphere structure. Objective: In the current review, the recent progress on the preparation and medical applications of chitosan microspheres would be introduced and summarized. Method: The methods for the preparation of CS microspheres were summarized, such as emulsion crosslinking method, coacervation method, precipitation method and polyelectrolyte complexation method, and so on. The tunable chemical properties possessed by CS microsphere, such as easily modified structure, and excellent biological properties including lower cytotoxicity, biocompatibility and biodegradability, would be introduced. Its medical applications based on its amazing properties in the recent years were present in detail with emphasis on the progress and advancement in drug delivery, gene therapy, bone repair, tissue engineering and wound dressing. Conclusion: It was believed that the rapid development of novel preparation technology will bring broader application prospects to CS microspheres. Keywords: Chitosan, microspheres, preparation, medical application, lower cytotoxicity, biocompatibility and biodegradability.

Preparation and Drug Release of PVA Composite Nanofibers Loaded Chitosan Microsphere

In this paper, we reported the fabrication of poly(vinyl alcohol)-chitosan (PVA-CS) microspheres composite nanofibers by electrospinning technique. The chitosan microspheres were firstly prepared by electrospray with the solution of chitosan and combretastatin A4. The morphology and size distribution of chitosan microspheres were analyzed by scanning electron microscopy. The influencing factors including the concentrations of both PVA and CS microspheres were studied. The physical properties of the composite nanofibers were characterized by X-ray diffraction (XRD). The drug release rate, MTT toxicity test, and cell culture were also investigated in detail. Results indicate that the chitosan microsphere-loaded composite nanofibers can be prepared when the PVA concentration is 120 mg/mL. The continuity of the nanofibers was influenced by the concentration of CS microspheres. The characteristic peaks of CS or PVA were not observed in the diffractograms after the CS and PVA were processed using the high-voltage electrostatic technique. In addition, the drug release rate showed that nanofibers induce an obvious slow-release effect. Composite nanofibers were non-toxic to fibroblasts cells, and the fibroblasts cells could proliferate on the nanofiber mat.

Reinforced chitosan membranes by microspheres for guided bone regeneration.

In order to improve the osteogenic activity and mechanical strength of the guided bone regeneration (GBR) membrane for repairing bone defect, nano-hydroxyapatite/chitosan (nHA/CS) composite microspheres were prepared through in situ biomimetic method, then composite microspheres were incorporated into CS membrane. The morphologies and mechanical properties of the composite membranes were investigated through scanning electronic microscopy (SEM) and universal mechanical testing machine. The results show that the in situ biomimetic nHA/CS microspheres were embedded in CS membrane and were integrated tightly with CS matrix. The mechanical properties of GBR membranes containing in situ nHA/CS microspheres is significantly higher than that of membranes containing pure CS microspheres and blending nHA/CS microspheres. Its elongation rate at break reaches 5.61 ± 0.95%. The elastic modulus and strength of the GBR membranes can reach 766.27 ± 20.68 and 43.32 ± 0.95 MPa, respectively. Further, The work-of-fracture of the membranes with in situ microspheres approaches 2.71 ± 0.25 J/m2, which is about 3 times of the pure CS membrane. The cell culture results display that the GBR membranes containing in situ biomimetic nHA/CS microspheres exhibit good cytocompatibility.

A Green Modified Microsphere of Chitosan Encapsulating Dimethyl Fumarate and Cross-Linked by Vanillin and Its Application for Litchi Preservation

A green sustained delivery biomaterial was prepared to encapsulate dimethyl fumarate (DMF) by an emulsion–cross-linking method for sustained release. The average size of the microspheres was 20–150 μm. The highest encapsulation efficiency and loading efficiency were 85.7 and 13.2%, respectively. The release of DMF in phosphate buffer saline followed a Fickian diffusion. In addition, the results of inhibition zone showed that DMF-loaded microspheres exhibited antimicrobial and antifungal properties much better than those of CS microspheres. Furthermore, weight loss of treated fruit was reduced insignificantly, and storage time was extended with the stable quality of litchi as compared with that of the control group. Thus, the microspheres were synthesized successfully as a sustained delivery system for DMF, which might have broad prospect and development value in preservation of fruits and vegetables.

Preparation of Carboxymethyl Chitosan Microspheres and Their Application in Hemostasis.

Chitosan (CS) is currently used as a hemostatic agent in emergencies and in military settings. However, its application is limited owing to its poor hydrophilia at neutral pH. Carboxymethyl chitosan (CMCS) is an important, water-soluble derivative of CS. In this study, we prepared CS and CMCS microspheres (CSMs and CMCSMs, respectively) and evaluated their hemostatic effect. To prepare the microspheres of various sizes, we used the emulsion cross-linking technique. CMCSMs were also loaded with etamsylate (DIC). Clotting time in vitro and in a hepatic injury model was examined to evaluate the hemostatic effect. CMCSMs swelled more and clotted faster than did CSMs. CMCSMs loaded with DIC had no effect on hemostasis. Both increasing material hydrophilicity and expanding the contact area promoted clotting, whereas chemical cross-linking hampered it because of decreased swelling. CMCSMs are promising candidates for the production of effective hemostatic agents. (Disaster Med Public Health Preparedness. 2017;11:660-667).

Relationship between breakthrough curve and adsorption isotherm of Ca(II) imprinted chitosan microspheres for metal adsorption

In this work, an equilibrium-dispersion model was successfully established to describe the breakthrough performance of Ca(II) imprinted chitosan (Ca(II)-CS) microspheres packed column for metal adsorption, and the assumptions of Langmuir isotherms and axial dispersion controlled mass transfer process were confirmed. The axial dispersion coefficient in Ca(II)-CS microspheres packed column was found to be almost proportional to the linear velocity and fit for prediction through single breakthrough test. Sensitivity analysis for breakthrough curve indicated the axial dispersion coefficient as well as Langmuir coefficient was sensitive variable for deep removal requirement. The retrieval of the adsorption isotherms of Ca(II)-CS microspheres from breakthrough curve was fulfilled by modelling calibration. A strategy based on the correlation between adsorption isotherms and breakthrough performance was further proposed to simplify the column adsorption design using absorbents with small/uniform size and fast adsorption kinetics like Ca(II)-CS microspheres to cut down the gap between lab and industry.

In situ Biomimetic Mineralization and Characterization of Carbon Nanotubes/chitosan Composite Microspheres†

Carbon nanotubes / chitosan( CNTs / CS) composite microspheres were prepared by emulsification and cross-linking method. Nano-hydroxyapatite crystals were biomimetically formed on the surface of the composite microspheres. The influence of CNTs on the mineralization of the microspheres was investigated. The morphologies,structurs and stability properties of the microspheres before and after mineralization were studied through scanning electronic microscopy( SEM),X-ray diffraction( XRD),swelling ratio and water content tests. The results show that the formation ability of the nano-hydroxyapatite on the CNTs / CS microspheres is significantly higher than that on pure CS microspheres. And the mineralized CNTs / CS microspheres exhibit better structure stability. After culturing with MG63 cells for 7 d,the proliferation of cells cultured with mineralized CNTs / CS microspheres shows significant difference from that of the cells cultured with mineralized CS microspheres.

Zeolite X/chitosan hybrid microspheres and their adsorption properties for Cu(II) ions in aqueous solutions

The preparation of zeolite X/chitosan (CS) hybrid microspheres for efficient removal of Cu(II) ions by an impregnation-gelation-hydrothermal synthesis technique is reported here. Characterizations by various techniques indicate that the microspheres show porous structures and intimate interaction between zeolite and CS. The adsorption experiments are performed to evaluate the adsorption capacity of zeolite X/CS hybrid microspheres and comparisons are made with binderless zeolite X microspheres, pure CS microspheres and mechanical mixed zeolite X/CS microspheres. The effects of Cu(II) solution concentration and the pH are investigated. The results indicate that zeolite X/CS hybrid microspheres with the zeolite content of 60 wt% show the highest adsorption capacity, which is 90 mg/g at the initial Cu(II) concentration of 10 mg/L and 150.4 mg/g at Cu(II) concentration of 500 mg/L. The adsorption capacity increases with increasing initial pH and reaches a maximum at pH 5.5 in the range of 0–6.0. The equilibrium adsorption data are well described by the Langmuir isotherm model, exhibiting a maximum adsorption capacity of 152.0 mg/g, and the kinetic data are well fitted with the pseudo-second-order equation. Complete removal of Cu(II) ions can be obtained even at very low concentrations. The microspheres show high adsorption capacity and efficiency for Cu(II) ions, exhibiting potential practical application in the treatment of water pollution of heavy metal ions.

Ca(II) imprinted chitosan microspheres: An effective and green adsorbent for the removal of Cu(II), Cd(II) and Pb(II) from aqueous solutions

Abstract Ca(II)–CS microspheres with uniform size and morphology were first synthesized as a green and effective absorbent for the treatment of hazardous wastewater containing heavy metal ions. The adsorption capacities for Pb(II), Cd(II) and Cu(II) reached 47.1 mg, 49.9 mg and 41.5 mg per gram of Ca(II)–CS microsphere within 30 min, respectively. The pseudo-first-order equation and Langmuir isotherm model are fit to describe the adsorption kinetics and equilibrium separately. The orders of Δ G °, Δ H ° and Δ S ° for three metal ions adsorption were in accordance with the theoretical analysis. TGA, FTIR and XPS measurements verified that Ca(II) ions played a role in tuning crosslinking degree by a weak complexation of NH 2 –Ca(II), and only amino groups were well-recognized as active sites for metal ions adsorption. An insight can be gained into the use of Ca(II)–CS microspheres for various heavy metal ions treatment in packed column.

A comparative study on the performance of dye removal, from aqueous suspension, using (2-hydroxypropyl)-β-cyclodextrin-CS, PVP-PVA-CS, PVA-CS, PVP-CS and plain CS microspheres

This paper reports the results of the study on the performance of the removal of Cibacron Brilliant Yellow 3G-P and Calmagite, from aqueous solution, using either prepared 2-hydroxypropyl-β-cyclodextrin-chitosan [HPβCD-CS], poly(vinylalcohol)-polyvinylpyrrolidone-chitosan [PVA-PVP-CS], Poly(vinylalcohol)-chitosan [PVA-CS], polyvinylpyrrolidone-chitosan [PVP-CS] or plain chitosan microspheres [CS]. Modified CS molecules were analysed using FT-IR and TG-DTA techniques. Adsorption experiments were carried out and compared through varying mass ratio, contact time, initial dye concentration and temperature. Among the five studied adsorbents, the highest adsorption capacity was reached using HPβCD-CS. Kinetic equations were applied and the first-order model was shown to fit the adsorption phenomenon. The applicability of Langmuir, Freundlich, Temkin and Dubinin–Radushkevich equations was tested and the Langmuir isotherm exhibited the best fit with the experimental data. Data gleaned from both modelling and thermodynamic results indicate that the adsorption follows a physical and exothermic process.

Fabrication and characterization of bioactive calcium silicate microspheres for drug delivery

The calcium silicate (CaSiO3, CS) microspheres with diameter of 75–100μm were fabricated by a spray-drying method. A new bone-like apatite layer fully covered the surface of the fabricated CS microspheres after soaking in simulated body fluid (SBF), suggesting the excellent activity of the material in inducing apatite deposition. The ionic extracts of CS microspheres promoted the proliferation of human osteoblast-like cells (MC3T3-E1). In addition, the porous structures of the CS microspheres resulted in favorable drug loading and sustained release property. Our study indicates that the fabricated multifunctional CS microspheres are a promising drug delivery system as an injectable bioactive filling material for bone-regeneration.

Reversible immobilization of glucoamylase onto magnetic chitosan nanocarriers

A simple preparation process for the monodispersed pH-sensitive core-shell magnetic microspheres was carried out consisting of chitosan self-assembled on magnetic iron oxide nanoparticles. Meanwhile, glucoamylase was immobilized as a model enzyme on this carrier of Fe(3)O(4)/CS microspheres by ionic adsorption. The morphology, inner structure, and high magnetic sensitivity of the resulting magnetic chitosan microspheres were studied, respectively, with a field emission scanning electron microscope (SEM), transmission electron microscope (TEM), FT-IR spectroscopy, thermogravimetric analysis (TGA), and a vibrating sample magnetometer (VSM). Subsequently, the properties of glucoamylase immobilized on the regenerated supports were also investigated by determining storage stability, pH stability, reusability, magnetic response, and regeneration of supports. The results from characterization and determination remarkably indicated that the immobilized glucoamylase obtained presents excellent storage stability, pH stability, reusability, magnetic response, and regeneration of supports. Therefore, this kind of magnetic Fe(3)O(4)/CS microspheres with perfect monodispersity should be an ideal support for enzyme immobilization.

Effect of proteolytic enzymes in gastrointestinal fluids on drug release from polyelectrolyte complex microspheres based on partially phosphorylated chitosan

AbstractThis study investigated the effect of proteolytic enzymes on in vitro release of ibuprofen from phosphorylated chitosan (PCS) microspheres in simulated gastric fluid (SGF) (pH 1.4) and simulated intestinal fluid (SIF) (pH 7.4). To reduce the enzymatic degradability and to enhance the sustained release property, polyelectrolyte complex microspheres based on PCS were developed and characterized. The ibuprofen release from PCS microspheres was found to be sustained more effectively than that from CS microspheres in the medium containing proteolytic enzymes. It was concluded that the PCS microspheres can be used more successfully as sustained oral drug‐delivery vehicles than CS microspheres due to their lesser enzymatic degradability. Copyright © 2004 Society of Chemical Industry