Magnetic Chitosan Microspheres Research Articles

Adsorption of haem by magnetic chitosan microspheres: Optimal conditions, adsorption mechanisms and density functional theory analyses

Magnetic chitosan microspheres (Al@CTS@Fe3O4) were prepared for haem separation via chemical cross-linking of chitosan, Fe3O4 and AlCl3·6H2O. The properties of the Al@CTS@Fe3O4 microspheres were investigated through techniques including XRD, TEM, FTIR, BET analysis, SEM, TG, VSM, XPS and pHpzc analysis. The haem adsorption of Al@CTS@Fe3O4 was optimized via a Box–Behnken design (BBD) with three operating factors: Fe3O4 dose (0.5–1.3 g), AlCl3·6H2O concentration (0.25–1.25 mol/L) and glutaraldehyde dose (2–6 mL). The optimal haem adsorption effect was achieved with 1.1 g of Fe3O4, 0.75 mol/L AlCl3·6H2O, and 3 mL of glutaraldehyde. The adsorption kinetics and isotherms demonstrated that haem adsorption by the Al@CTS@Fe3O4 microspheres was best described by the pseudo-second-order model. The maximum adsorption capacity is 33.875 mg/g at pH 6. After six adsorption–desorption cycles, the removal of haem still reached 53.83 %. The surface adsorption mechanism of haem on Al@CTS@Fe3O4 can be attributed to electrostatic, hydrogen bonding, and n-π interactions. Thermodynamic calculations indicated that the adsorption process is spontaneous, with the microspheres preferentially accepting electrons and haem preferentially providing electrons. Consequently, the Al@CTS@Fe3O4 microspheres exhibit considerable potential as adsorbents for haem separation.

Preparation, Structural Characterization, and Enzymatic Properties of Alginate Lyase Immobilized on Magnetic Chitosan Microspheres.

Alginate lyase is an enzyme that catalyses the hydrolysis of alginate into alginate oligoalginates. To enhance enzyme stability and recovery, a facile strategy for alginate lyase immobilization was developed. Novel magnetic chitosan microspheres were synthesized and used as carriers to immobilize alginate lyase. The immobilization of alginate lyase on magnetic chitosan microspheres was successful, as proven by Fourier transform infrared spectroscopy and X-ray diffraction spectra. Enzyme immobilization exhibited the best performance at an MCM dosage of 1.5g/L, adsorption time of 2.0h, glutaraldehyde concentration of 0.2%, and immobilization time of 2.0h. The optimal pH of the free alginate lyase was 7.5, and this pH value was shifted to 8.0 after immobilization. No difference was observed at the optimal temperature (45°C) for the immobilized and free enzymes. The immobilized alginate lyase displayed better thermal stability than the free alginate lyase. The Km values of the free and immobilized enzymes were 0.05mol/L and 0.09mol/L, respectively. The immobilized alginate lyase retained 72% of its original activity after 10 batch reactions. This strategy was found to be a promising method for immobilizing alginate lyase.

Preparation of cross-linked chitosan magnetic microspheres and immobilization of pectinase

Abstract In this paper, the kinetic model under the influence of each factor is given by investigating the effects of distribution effect, external diffusion effect and internal diffusion effect on the immobilized pectinase reaction system. The magnetic chitosan microspheres were prepared by the reversed-phase suspension cross-linking method, and the effects of the type and amount of cross-linking agent and the ratio of chitosan to magnetic core incorporation on the performance of the magnetic spheres were investigated. Then, the immobilized pectinase was prepared by using cross-linked chitosan magnetic microspheres as a carrier, and an orthogonal test was used to determine the conditions of immobilized enzyme preparation and to study the enzymatic properties and operational stability of immobilized pectinase. The results showed that the transmittance of the magnetic microspheres of this test increased from 32% to 90.79% in 10 min in a magnetic field, but in a gravity field, the transmittance increased from 32.12% to 46.44% in 50 min. The experimentally prepared microspheres exhibit good magnetic responsiveness. The optimum temperature of immobilized pectinase was 50°C, and the remaining enzyme activity was still 61.24% after 6 repetitions. The immobilized pectinase made by crosslinking glutaraldehyde with chitosan magnetic microspheres has a high recovery of enzyme activity and good operational stability, as indicated by this.

Removal of methyl orange textile dye using magnetic chitosan microspheres adsorbent

Abstract Industrial textile wastewater contains high levels of dyes, which are potentially harmful to aquatic ecosystems by inhibiting sunlight penetration for photosynthesis activities. Adsorption is a simple method for pollutant removal for water treatment. Magnetic Chitosan Microspheres (MCM) has been developed as a natural adsorbent for dye removal. This study aimed to compare the properties of the raw adsorbent and after adsorption by FT-IR, BET, DLS, and SQUID Magnetometry. The adsorption behaviours were investigated by the influence of pH, contact time, and initial concentration on Methyl Orange removal. The result was MCM could eliminate MO until 93.60% at pH 7 with C0 100 mg L−1 in 5 min with an adsorption capacity of 187.21 mg g−1. Adsorption processes were also studied through the isotherm and kinetic. The isotherm showed a closer fit to the Langmuir model than the Freundlich model. The kinetic result showed the PSO model was more suitable than PFO. The research data using MCM for adsorption demonstrated excellent adsorption capability in terms of dye removal percentage and high adsorption capacity. Therefore, this material could be an effective adsorbent for the treatment of dye-containing wastewater.

Study on the polypeptide-functionalized magnetic chitosan microspheres that specifically adsorb Hg (II) ions

Here, we present an effective and environmentally friendly approach for fabricating polypeptide functionalized magnetic chitosan microspheres (Fe3O4@CTS@PS) based on the effective binding of polypeptide (GCTCWCSGE) with mercury ions (Hg (II)). The morphology and component of the prepared Fe3O4@CTS@PS was characterized via scanning electronic microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and vibrating sample magnetometer. Effects of the polypeptide sequence, pH, adsorption time, initial concentration, temperature on the adsorption performance and anti-interference ability and reusability were studied. The Fe3O4@CTS@PS had excellent adsorption selectivity for Hg (II) and the adsorption capacity can reach to 218.8 mg·g−1 at 318 K and pH5.0. Kinetic data was correlated well with the pseudo-second-order model and adsorption isotherm agreed well with the Langmuir isotherm model. The reusability of Fe3O4@CTS@PS was also investigated and the adsorption capacity of Fe3O4@CTS@PS for Hg(II) still remained 92% of the initial values after four adsorption-elution cycles (eluting agent was Na2S2O3). The prepared Fe3O4@CTS@PS showed excellent adsorption performance for Hg (II) in real samples (lake water, milk and nori) and was a promising adsorbent in practical applications.

Microfluidic preparation of magnetic chitosan microsphere and its adsorption towards Congo red

Microfluidic preparation of magnetic chitosan microsphere and its adsorption towards Congo red

Preparation and characterization of PEGDE-EDTA-modified magnetic chitosan microsphere as an eco-friendly adsorbent for methylene blue removal

Chitosan has been acknowledged as the emerging prominent pollutant remover with environmentally friendly properties. Herein, we have developed magnetic chitosan (MC) microsphere with functional group enrichment using polyethylene glycol diglycidyl ether (PEGDE) and ethylenediaminetetraacetic acid (EDTA) to remove aqueous methylene blue. The success of the functional group enrichment was proven by the characterization carried out in Fourier transform-infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and Scanning Electron Microscope (SEM) analyses. The adsorption capacity of methylene blue onto the prepared MC increased as much as 37.62% after the addition of EDTA. The optimum adsorption parameters recorded in this study were 30minutes contact time and pH level of 10. At such optimum conditions, the adsorption capacity and removal percentage reached 5.04±0.03 mg/g and 80.64±0.12%, respectively. Adsorption studies using various models revealed that the best fit of experimental data with that of theoretical was generated by the Freundlich model equation (R2 = 0.95283; root-mean-square-errors = 27.22). Exothermic adsorption was observed according to the thermodynamic study (∆H = -124.43 kJ/mol). In conclusion, our adsorbent prepared from green materials and methods could effectively remove the methylene blue from water medium.

Preparation of quaternary ammonium magnetic chitosan microspheres and their application for Congo red adsorption

In this study, novel green in situ quaternary-ammonium-functionalized magnetic chitosan microspheres (IQMCM) were synthesised. The resulting adsorbent was characterised by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometry, X-ray photoelectron spectroscopy, and zeta potential analysis. The characterization results indicated that the IQMCMs possessed spherical morphology and superior specific thermal stability, magnetic properties, and surface charges. Batch adsorption experiments revealed that the adsorption capacities of the IQMCM microspheres to Congo red (CR) was 630.21 mg/g at a dosage of 0.15 g/L, temperature of 333 K, pH of 5.0, and initial dye concentration of 100 mg/L, and the corresponding removal rate reached 94.53 %. According to the kinetics, adsorption isotherms, and thermodynamics experiment results, the adsorption of CR dye coincided with a spontaneous endothermic monolayer chemisorption process. After saturated adsorption, this magnetic adsorbent could be rapidly separated from water and reused with little adsorption capacity loss. Overall, these results show that IQMCMs are potentially applicable in wastewater treatment.

Preparation, Characterization and Adsorption Study of PEDGE-Cross-linked Magnetic Chitosan (PEDGE-MCh) Microspheres for Cd2+ Removal

Preparation, Characterization and Adsorption Study of PEDGE-Cross-linked Magnetic Chitosan (PEDGE-MCh) Microspheres for Cd2+ Removal

Co-immobilization of glucose oxidase and catalase in porous magnetic chitosan microspheres for production of sodium gluconate

Abstract In the process of immobilizing the enzyme, the overflow of enzyme and the decrease of enzyme activity are very serious. In order to improve the stable binding between enzyme and carrier, a kind of porous magnetic chitosan microsphere with appropriate pore size was successfully prepared by adjusting the size of pore-forming agent in this paper. The rough porous structure is favorable for the adsorption of enzyme and the catalytic action of enzyme on substrate. The results showed that when the pore size of the microspheres was at 790.15 ± 250.91 nm, the protein loading and enzyme activity of GOD could be increased effectively, which could reach 58.28 ± 2.64 mg/g and 16.93 ± 0.14 U, respectively. The co-immobilization of CAT and GOD eliminated the harmful by-product H2O2 in time and effectively solved the problem of continuous deactivation of GOD in the reaction process. When the mass ratio of PMCSM/GOD/CAT was 100/6.02/10.96 (mg/mg/mg), the relative enzyme activity of GOD reached the highest (133.32 ± 0.68%). The thermal stability and pH stability of the enzyme were greatly improved after co-immobilization. The relative enzyme activity of PMCSM@GOD@CAT was 57.27 ± 3.04% at 60 °C, while that of free GOD was only 28.76 ± 4.10%. The relative enzyme activity of PMCSM@GOD@CAT was above 63% at pH 5–10, while the relative enzyme activity of free GOD was only 4.98 ± 0.72% at pH 10. The yield of sodium gluconate from 50 mL 250 mg/mL glucose catalyzed by PMCSM@GOD@CAT loading 60.2 mg GOD was 96.19 ± 0.79% at pH 6.0 and 30 °C, and the reaction lasted 6 h. The relative enzyme activity of PMCSM@GOD@CAT remained 69.77 ± 0.78% after repeated use for 10 times. After 30 days of storage, PMCSM@GOD@CAT maintained its initial activity of 76.52 ± 1.41%. The immobilized process studied in this paper provides a theoretical basis for the production of sodium gluconate by double enzyme directly catalyzing and lays a certain foundation for the application of immobilized enzyme in the future chemical industry and food industry.

Antimicrobial hydrogel microspheres for protein capture and wound healing

Growth factors are vital to regulate cellular responses for wound healing process. Engineered microspheres provide a promising tool for developing effective growth factor-loaded matrix for regenerative medicine therapy. Here, we report a novel multifunctional chitosan microsphere that enables facile one-step capture and efficient growth factor delivery for enhanced wound repair. The microfluidic technique was used to fabricate magnetic chitosan (MCS) microspheres. By immobilization with Zn2+ ions, the biohybrid MCS allowed for the flexible operation to capture histidine-tagged vascular endothelial growth factor (VEGF) produced in Escherichia coli (E. coli). The VEGF-conjugated MCS were then applied onto the wounds to examine their capabilities in promoting wound healing. Zn2+ and chitosan in MCS exhibited a synergetic antibacterial effect towards both Gram-positive and Gram-negative bacteria. Using a rat model, we further demonstrated that the microspheres significantly promoted wound healing process, as evidenced by rapid wound closure, induced epithelialization and angiogenesis, and reduced inflammation response. Together, our data indicated the presented MCS as a versatile tool for capturing and locally delivering growth factors, which can be applied to wound repair. Moreover, with the functional flexibility, this biohybrid MCS could be empolyed in a wide range of biomedical applications by conjugating proteins of interest.

An effective and recyclable decolorization method for polysaccharides from Isaria cicadae Miquel by magnetic chitosan microspheres.

The purpose of this research was to develop an efficient and non-destructive method for decolorizing of polysaccharides extracted from Isaria cicadae Miquel by magnetic chitosan microspheres (MCM). The optimum decolorization parameters were achieved by response surface methodology as follows: the MCM amount was 8.0%, the adsorption temperature was 48 °C, the adsorption time was 82 min and the pH was 7. Under these optimal conditions, the Dr%, Rr%, and Kc were 90.31 ± 0.12%, 95.40 ± 0.11% and 19.66 ± 0.49, respectively. MCM adsorption of pigment molecules was a spontaneous and endothermic process that could be fitted with the pseudo-second-order equation and the Freundlich equation. Besides, the adsorption mechanism could be controlled by multiple-diffusion steps, including film diffusion and intra-particle diffusion. Furthermore, MCM is a recyclable material. Adsorption with MCM is a promising method to remove pigment molecules of polysaccharide, it may replace the traditional decolorization method.

Artificial naringinase system for cooperative enzymatic synthesis of naringenin

Naringinase is a kind of glycosidase that catalyzes the biotransformation of naringin into naringenin. It is a multi-compound enzyme that provides the activity of α-L-rhamnosidase and β-glucosidase. In this study, an artificial naringinase system was constructed by co-immobilizing α-L-rhamnosidase (Aspergillus oryzae FJ0123, Ao-rha) and β-glucosidase (Thermotoga maritima MSB8, Tm-glu) on magnetic silica-based chitosan microspheres (MSC). The molar ratio of enzymes and the preparation conditions were optimized for improving synergistic effect and immobilization efficiency. Under optimized conditions (the molar ratio of Ao-rha and Tm-glu, 3:1; temperature, 25 °C; glutaraldehyde concentration, 2.0%; pH, 3.0; time, 9 h), the immobilization yield and activity recovery were 61.4% and 37.3% for Ao-rha and 90.1% and 56.3% for Tm-glu, respectively. Biochemical characterization indicated that MSC-naringinase had better adaptability and stability than free enzymes. The activity of MSC-naringinase was maintained at 58.7% after 10 times of recycling. The catalytic conditions were also investigated. The cascade reactions of naringin to prunin and prunin to naringenin by using MSC-naringinase resulted in a yield of 0.62 mg/mL and a conversion rate of 96.9%, respectively, without prunin accumulation. These results indicated the great potential of MSC-naringinase as an efficient artificial naringinase system for cooperative enzymatic synthesis of naringenin.

Magnetic chitosan microspheres for the removal of methyl violet 2B from aqueous solutions

This work aimed to evaluate the adsorption capacity of magnetic chitosan microspheres for the removal of methyl violet (MV) 2B dye. For this purpose, magnetite was prepared by chemical precipitation of iron salts in alkaline medium and incorporated to chitosan microspheres which were obtained by the suspension cross-linking technique. The influence of the experimental parameters, such as adsorbent dosage (0.05 to 0.25 g), stirring frequency (100 to 800 rpm), pH (2.0 to 12.0), initial dye concentration (30 to 90 mg L−1), and contact time (5 to 480 min), as well as the equilibrium, kinetics and thermodynamics were also evaluated. Furthermore, five isotherm models and three kinetic models were tested to analyze the experimental data. The results evidenced that the equilibrium was better described by the Langmuir isotherm (qm = 128.84 mg g−1), although the statistical Fisher's test showed that other models could also be applied to describe the experimental results. Kinetics studies showed that the adsorption followed the pseudo-second order model with a significant difference between the tested models and that the adsorption process involves more than one sorption rate. It was also found that the adsorption of MV 2B dye onto magnetic chitosan microspheres was an exothermic (ΔH°ads = −1.70 kJ mol−1) and spontaneous (ΔG°ads = −3.96 kJ mol−1) process. Finally, it can be concluded that the magnetic chitosan microspheres constituted an efficient and inexpensive material for the removal of the MV 2B dye from aqueous solutions.

Adsorption of tetracycline antibiotics by nitrilotriacetic acid modified magnetic chitosan-based microspheres from aqueous solutions

With the abuse of tetracycline antibiotics and their high detection rate in the water environment, causing non-negligible environmental hazards and health risks, the treatment of tetracycline wastewater has been paid much attention. Herein, a noval magnetic adsorbent, nitrilotriacetic acid-modified magnetic chitosan microspheres (NDMCMs) was successfully prepared and applied to remove tetracycline antibiotics (TC) from wastewater. The results found that the solution pH and ion strength greatly affected the adsorption capacity of TC by NDMCMs. Additionally, the adsorption capacity of NDMCMs (373.5 mg g −1 ) was four times higher than that of MCMs (92 mg g −1 ) at pH 8.0, attributed to the various amino and carboxyl groups in the grafted chain. The experiment data were better correlated with the Freundlich isotherm model and the pseudo-second-order kinetic model, indicating that the adsorption between TC and adsorbent surfaces occurred as multilayer adsorption, and the chemical interaction played as a rate-limiting step in the adsorption process. The thermodynamic parameter calculation results demonstrated that the adsorption of TC by NDMCMs followed a spontaneous, endothermic, and orderly process. Besides, the regeneration performance of NDMCMs showed that it is fully qualified for practical application of TC adsorption. The adsorption mechanism proposed by the FT-IR spectroscopic analysis of the adsorbent before and after the adsorption of TC was mainly through π - π interaction, cation- π bond, hydrogen bond, and amidation reaction. Based on all experimental results, NDMCMs is an efficient and sustainable magnetic adsorbent, which can be used to remove TC from wastewater. • Chitosan-based magnetic adsorbent with NTA modified are synthesized. • NDMCMs showed excellent adsorption capacities for tetracycline. • NDMCMs could be efficiently separated from aqueous solutions with magnetic force. • TC-loaded NDMCMs could be easily regenerated and reused more than five-times. • The good reusability of adsorbent indicated its practical application.

Magnetic chitosan microspheres: An efficient and recyclable adsorbent for the removal of iodide from simulated nuclear wastewater

The efficient and recyclable magnetic chitosan microspheres (MCMs) were successfully synthesized to remove iodide from nuclear wastewater and characterized through XRD, FTIR, SEM, EDS, VSM, TGA and XPS. The characterization results indicated that the MCMs exhibited smooth spherical morphology and good magnetic properties. The removal potential of MCMs was investigated for iodide (I−) anions at different conditions. From pH 3 to pH 9, MCMs performed the high I− removal efficiency (>90%). The maximum I− removal capacity of MCMs was up to 0.8087 mmol g−1 at 298 K, well-fitting with the pseudo-second-order and Sips models. Furthermore, the I− removal efficiency of MCMs still maintained more than 91% after five adsorption-desorption cycles, performing good regeneration and reusability. This study is expected to prompt the MCMs to become an efficient and recyclable biosorbent for iodide removal from nuclear wastewater.

Degradation-Dependent Controlled Delivery of Doxorubicin by Glyoxal Cross-Linked Magnetic and Porous Chitosan Microspheres.

Glyoxal cross-linked porous magnetic chitosan microspheres, GMS (∼170 μm size), with a tunable degradation profile were synthesized by a water-in-oil emulsion technique to accomplish controlled delivery of doxorubicin (DOX), a chemotherapeutic drug, to ensure prolonged chemotherapeutic effects. The GMS exhibit superparamagnetism with saturation magnetization, Ms = 7.2 emu g–1. The in vitro swelling and degradation results demonstrate that a swelling plateau of GMS is reached at 24 h, while degradation can be modulated to begin at 96–120 h by formulating the cross-linked network using glyoxal. MTT assay, live/dead staining, and F-actin staining (actin/DAPI) validated the cytocompatibility of GMS, which further assured good drug loading capacity (35.8%). The release mechanism has two stages, initiated by diffusion-inspired release of DOX through the swollen polymer network (72 h), which is followed by a disintegration-tuned release profile (>96 h) conferring GMS a potential candidate for DOX delivery.

Facile synthesis of magnetic CS-g-SPSS microspheres via electron beam radiation for efficient removal of methylene blue

Efficient adsorption and separation of organic dyes in the wastewater is highly desirable for environmental protection. A facile synthesis of magnetic bio-based chitosan (CS) microspheres grafted with sodium polystyrene sulfonate (SPSS) via electron beam radiation is described. The obtained microspheres were characterized by FTIR, SEM, TG and VSM, which demonstrated millimetric magnetic CS-g-SPSS microspheres were obtained with enhanced thermal stability. Experimental parameters such as absorbed dosage, mass ratio, initial pH, initial concentration and contact time for the adsorption were thoroughly investigated. To investigate the adsorption rate and recyclability, evaluation of adsorption kinetic model and adsorption/desorption experiment were conducted.

High specific immobilization of His-tagged recombinant Microbacterium esterase by Ni-NTA magnetic chitosan microspheres for efficient synthesis of key chiral intermediate of d-biotin.

The novel Ni-NTA-functionalized magnetic chitosan microspheres (MCS-NTA-Ni) were prepared via amino functionalization of MCS with epichlorohydrin and ethylenediamine, followed by the introduction of the aldehyde groups and NTA in turn, and nickel (II) ions were chelated in the end. MCS-NTA-Ni contained numerous long-armed NTA-Ni surface groups, ensuring high enzyme loading and providing more space and flexibility to attach enzymes and maintain their activity. This microsphere can have highly selective adsorption of his-tagged recombinant protein. The his-tagged recombinant Microbacterium esterase of E. coli BL21 (DE3)/pET21a-EstSIT01 was first immobilized on MCS-NTA-Ni by affinity fixation, giving high immobilization yield (90.1%) and enzyme loading (120mg/g). Compared with free esterase, the immobilized esterase was found to exhibit higher pH stability and thermal stability. In addition, the immobilized esterase had excellent reusability for the synthesis of key chiral intermediate of d-biotin and the substrate conversion could still keep 100% after 8 cycles continuously.

Preparation of poly(sodium 4-styrene sulfonate) grafted magnetic chitosan microspheres for adsorption of cationic dyes

A novel adsorbent with high adsorption capacity to remove cationic dyes was synthesized. Sodium 4-styrene sulfonate (SSS) was grafted polymerization on the surface of magnetic chitosan microspheres via -NH2/S2O82− surface initiating system, obtaining MCS-g-PSSS microspheres. The grafted microsphere was characterized by Fourier transforms infrared spectroscopy, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, vibration sample magnetometer and the Brunauer-Emmett-Teller. Cationic dyes were adsorbed by MCS-g-PSSS and methylene blue(MB) was acted as a typical example. The adsorption performance was explored by varying experimental conditions. The results showed the maximal adsorption capacity was 989 mg/g at pH 1 at 25 °C. The pseudo-second order model was found to be applicable for the adsorption kinetics. The adsorption capacity increased with rising temperature and it decreased owing to adding of ions. The adsorption isotherms were the best fitted by Langmuir. MCS-g-PSSS for MB showed high adsorption capacity due to the strong electrostatic interactions and π-π stacking, which was explained by FTIR and XPS and was verified by DFT calculations. The degree of adsorption spontaneity increased with rising the temperature. The grafted MCS-g-PSSS microspheres had high adsorption capacity for various kinds of cationic dyes and excellent for remove MB in the aqueous solution.