Magnetic Chitosan Microparticles Research Articles

Immobilized cold-active enzymes onto magnetic chitosan microparticles as a highly stable and reusable carrier for p-xylene biodegradation

Stability and reusability properties are the two most important factors that determine an enzyme’s application in industry. To this end, cold-active crude enzymes from a psychrophile (xylene monooxygenase (XMO) and catechol 1,2-dioxygenase (C1,2D) were immobilized on magnetic chitosan microparticles for the first-time using glutaraldehyde as a linker. The potential application of enzyme-loaded magnetic particles to remove and detoxify dissolved p-xylene from water confirmed the synergistic mechanism of degradation for in-situ bioremediation in soil and water. Immobilization was optimized based on four variables, such as magnetic particle (MPs), chitosan, glutaraldehyde, and enzyme concentrations. The immobilized enzymes were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). The immobilized enzymes showed improved pH tolerance ranging from 4.0 to 9.0, better temperature stability ranging from 5 to 50, higher storage stability (∼70% activity after 30 days of storage), and more importantly, reusability (∼40% activity after 10 repetitive cycles of usage) compared to their free form. Also, the immobilization of enzymes increased the effectiveness of the enzymatic treatment of p-xylene in soil (10,000 mg/kg) and water (200 mg/L) samples. As a result of the superior catalytic properties of immobilized XMO and C1,2D, they offer great potential for in situ or ex-situ bioremediation of pollutants in soil or water.

Functionalization of magnetic chitosan microparticles – Comparison of trione and trithione grafting for enhanced silver sorption and application to metal recovery from waste X-ray photographic films

Magnetic chitosan microparticles (MC) are successfully functionalized by grafting two pyrimidine derivatives (bearing either trione or trithione groups for MC-PYO and MC-PYS, respectively). The sorbents are characterized using SEM, TEM, BET, TGA, FTIR, titration, and elemental analysis. The study focuses on the comparison of the differential effects of functionalized groups on the sorption of silver. FTIR analysis shows the contributions of N-based, carbonyl, hydroxyl for silver binding onto MC-PYO, completed by sulfur contribution in the case of MC-PYS. Maximum sorption capacities at pH 6 reach 1.9 and 2.3 mmol Ag g−1 for MC-PYO and MC-PYS, respectively. The Langmuir and the Sips equations fit sorption isotherms. The reactive groups affect the thermodynamic characteristics: endothermic for MC-PYS against exothermic for MC-PYO. The affinity of S-based soft ligand in MC-PYS for soft metals makes the sorbent selective for Ag(I). On the opposite hand, for MC-PYO the O-based functional groups readily bind hard metals (HSAB principle), meaning less selective for silver recovery (from multi-component solutions). QSAR method (quantitative structure-activity relationships) allows correlating preferentially sorption properties with the covalent index. Nitric acid solutions (0.3 M) are highly efficient for total desorption of silver from metal-loaded sorbents, but soft enough to maintain remarkable sorption and desorption performances for at least five cycles. The sorbents are successfully applied to Ag(I) recovery from acidic leachate of waste photographic films: metal removal is enhanced at pH 5.2; MC-PYS is more efficient and selective than MC-PYO at pH 2.2.

Functionalization of magnetic chitosan microparticles for high-performance removal of chromate from aqueous solutions and tannery effluent

Textile and tannery industries are highly contaminating with discharge of high Cr concentrations. Developing bio-based sorbents with strong affinity for chromate, fast kinetics, and high recyclability is strategic for better reuse of industrial wastewater. Magnetic chitosan micro-particles (MC, for enhancing mass transfer) may constitute a solution for chromate removal from acidic solutions. The functionalization of this support with aminothiazole groups (ATA@MC) or imidazole carboxamide (AIC@MC) significantly improves chromate removal, with sorption capacities close to 6 mmol Cr g−1, at pH 2. The Langmuir and the Sips equations finely fit sorption isotherms, while the pseudo-first order rate equation fits well uptake kinetics (equilibrium within 60 min). Sorption and desorption properties are remarkably stable: sorption efficiency decreases by less than 6% at the fifth cycle (while the desorption efficiency maintains above 99%). The sorbents are highly selective for chromate removal from acidic tannery wastewater (against base metals). FTIR and XPS analyses are used for characterizing the materials and for identifying the binding mechanisms (including chromate reduction into Cr(III)). The sorbents are both showing promising performances for Cr(VI) removal in acidic solutions, including in very complex solutions such as tannery wastewater. AIC@MC is more selective for Cr(VI) removal, while ATA@MC has a broader reactivity for a wider family of metal ions. The antimicrobial properties of the functionalized sorbents are characterized by the determination of the zone of inhibition (ZOI) against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli and Candida albicans: the inhibition is slightly improved compared with magnetite chitosan microparticles. More generally, the Gram- bacteria are slightly more sensitive to the functionalized sorbents than Gram+ bacteria and Candida fungus.

Magnetic Biocatalysts of Pectinase: Synthesis by Macromolecular Cross-Linker for Application in Apple Juice Clarification

SUMMARYResearch backgroundPectinase enzyme has become a valuable compound in beverage industry. One of the most significant concepts to overcome the drawbacks of using industrial enzymes is their immobilization. In the present study, magnetic chitosan microparticles were utilized as a substrate for pectinase immobilization. New methods of enzyme immobilization involve the use of non-chemical cross-linkers between the enzyme and the substrate. The aim of this study is to immobilize the pectinase enzyme using polyaldehyde kefiran as a macromolecular cross-linker on magnetic particles.Experimental approachPectinase was immobilized in four steps: relative oxidation of kefiran and its application as a cross-linker, production of magnetic iron(II) iron(III) oxide (Fe3O4) microparticles, coating of magnetic Fe3O4 microparticles with chitosan, and immobilization of the enzyme on the substrate, prepared by the use of oxidized kefiran cross-linker. Parameters such as cross-linking concentration, time and ratio of chitosan magnetic microparticles to enzyme were optimized. Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering, transmission electron microscopy, and vibrating sample magnetometer were used to identify the groups and investigate the structures. The biochemical properties (stability of enzyme activity at different pH, temperature and time), enzyme reusability, kinetic parameters (Km and νmax) and apple juice turbidity, using free and immobilized pectinase enzymes, were also measured.Results and conclusionsCross-linker concentration, cross-linking time and the ratio of magnetic Fe3O4 microparticles with chitosan to enzyme were important factors in activity recovery of pectinase. FTIR analysis correctly identified functional groups in the structures. The results showed that after enzyme stabilization, the particle size and molecular mass, respectively, increased and decreased the magnetic saturation strength. According to the thermal kinetic study, the activity of the immobilized pectinase was higher than of its free form. The findings of this study indicate excellent stability and durability of the immobilized pectinase. Finally, a magnetic pectinase micro-biocatalyst was used to clarify apple juice, which reduced turbidity during processing.Novelty and scientific contributionThis study investigates the usage of kefiran oxidized as a new cross-linker for the immobilization of pectinase enzyme. Magnetic pectinase micro-biocatalyst has a good potential for industrial applications in the food industry, with high thermal stability.

Efficient removal of uranium, cadmium and mercury from aqueous solutions using grafted hydrazide-micro-magnetite chitosan derivative

Magnetic chitosan microparticles are functionalized by grafting a new hydrazide derivative to produce HAHZ-MG-CH, which is applied to the sorption of metal cations. The functionalization (appearance of new groups) and synthesis mechanisms are confirmed using elemental analyses, FTIR and XPS spectrometry, TGA and EDX analysis, SEM observation and titration. HAHZ-MG-CH bears high nitrogen content (≈ 10.9 mmol N g−1). Maximum sorption capacities at pH 5 reach up to 1.55 mmol U g−1, 1.82 mmol Hg g−1 and 2.67 mmol Cd g−1. Sorption isotherms are preferentially fitted by the Langmuir model. In acidic solutions, the sorbent has a marked preference for Hg(II) over U(VI) and Cd(II), while at mild pH uranyl species are preferentially bound. The sorbent has a lower affinity for Cd(II) in multicomponent solutions. Sorption occurs within 60 min of contact. The pseudo-first-order rate equation fits well kinetic profiles. HCl solutions (0.5 M) successfully desorb all the metal ions (yield exceeds 97% at the first cycle). The sorbent can be recycled for 5 cycles of sorption and desorption: the loss in efficiencies does not exceed 8%. The sorbent removes Hg(II), Cd(II) and Pb(II) from local contaminated groundwater at levels compatible with irrigation and livestock uses but not enough to reach the levels for drinking water regulations.

Uranium(VI) and zirconium(IV) sorption on magnetic chitosan derivatives – effect of different functional groups on separation properties

AbstractBACKGROUNDThe recovery of metal ions from aqueous solutions for environmental preservation or resource saving requires the development of new sorbents with enhanced separation properties. A new process has been designed for the functionalization of magnetic chitosan microparticles with grafting of either amidoxime (AO‐AHC) or hydrazinyl amine (HZ‐AHC). Their sorption properties have been tested for the recovery of uranium(VI) and zirconium(IV) from aqueous solutions.RESULTSA wide range of analytical tools is used for characterizing not only the chemical modifications but also the interaction mode between the sorbent and target metal ions; including elemental analysis and titration, Fourier‐transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS) characterizations, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations, energy‐dispersive X‐ray spectroscopy (EDX) analysis and textural characterization. The optimum pH values were found in the range 4–5. The maximum sorption capacities depend on the metal and the kind of functionalization: up to 1.38 mmol U g−1 for AO‐AHC and up to 1.96 mmol Zr g−1 for HZ‐AHC. The small size of magnetic particles limits the contribution of diffusion mechanisms in the overall control of uptake kinetics and the equilibrium is reached within 40–60 min. Metal desorption is highly effective (almost quantitative over five successive cycles of sorption and desorption) using 0.3 M hydrochloric acid solutions.CONCLUSIONAO‐AHC sorbent is more selective than HZ‐AHC in terms of separation of uranium(VI) from zirconium(IV), especially at pH close to 4. The results obtained in the treatment of acidic ore leachates confirm these trends. © 2019 Society of Chemical Industry

Magnetic immobilisation of phospholipase C and its hydrolysis of phospholipids in crude soybean oil

In this study, free phospholipase C (PLC) was immobilised onto magnetic carriers, including sodium alginate (MPCSA), magnetic chitosan microparticles (MCM), Fe3O4/P (glycidyl methacrylate (GMA)-EDG...

Modified magnetic chitosan microparticles as novel superior adsorbents with huge "force field" for capturing food dyes.

In this study, modified magnetic chitosan microparticles (MCDs) were fabricated and used as adsorbents for the removal of Food Yellow 3 (FY3) and Acid Yellow 23 (AY23) from aqueous solution. The magnetic microparticles were characterized by scanning electronic microscope, Brunauer-Emmett-Teller specific surface area, elemental analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetry analysis, differential scanning calorimetry, and vibrating-sample magnetometer. Then, the effects of pH value, initial dye concentration, and contact time on the adsorption of FY3 and AY23 by MCDs were investigated. Evidently, MCDs showed excellent adsorption performance for both food dyes, and their adsorption capacities (833.33 mg/g for FY3 and 666.67 mg/g for AY23) were considerably higher than those of unmodified adsorbents, which could be attributed to the electrostatic interaction and ion exchange between the grafted cationic polymer and food dyes. Adsorption isotherm and kinetic data of the magnetic microparticles were well fitted by Langmuir isotherm and pseudo-second-order kinetic model, respectively. The regeneration and reusability of MCDs were also explored. Results showed that more than 80% adsorption capacities of MCDs for FY3 and AY23 remained after five adsorption-desorption cycles.

Fabrication of methyl acrylate and tetraethylenepentamine grafted magnetic chitosan microparticles for capture of Cd(II) from aqueous solutions.

MCS-MA-TEPA microparticles, with 251.22 mg g-1 of adsorption capacity for Cd(II), higher than most of the counterparts, were first fabricated by chemical coprecipitation, spray drying, and Michael addition reaction, without any cross-linker participation. These Fe3O4-nanoparticle-embedded microparticles of 5.95 μm in size, derived from modifications by methyl acrylate (MA) and tetraethylenepentamine (TEPA) on magnetic chitosan (MCS) microparticles, were of plum-pudding-like and wrinkle-like topography portrayed by TEM and SEM. Such features were beneficial to adsorbent recycling and Cd(II) capture. BET examinations illustrated 6.084 m2 g-1 of specific surface area, 0.015 mL g-1 of pore volume, and 6.536 nm of pore diameter. FTIR, VSM, XRD, TEM-SAED, TG, and DTG characterizations were indicative of successful synthesis, satisfactory magnetism, well-defined architecture, and good thermostability. Optimal adsorption parameters for Cd(II) were determined via batch experiments. Thermodynamic parameters and adsorption data fitting implied an exothermic, spontaneous, monolayer, and chemisorption process. XPS analyses confirmed a potential adsorption mechanism that N and O atoms on microparticles chelated with Cd(II) ions in solutions. Additionally, MCS-MA-TEPA-Cd(II) microparticles were magnetically separated easily and had outstanding reusability even after five-time recycling, with a slight adsorption capability loss (< 12%). Altogether, MCS-MA-TEPA microparticles might serve as a promising adsorbent for contaminated water scavenging.

Uranium and europium sorption on amidoxime-functionalized magnetic chitosan micro-particles

Magnetic chitosan particles were successfully modified by amidoxime-grafting (as evidenced by FTIR analysis, SEM-EDX analysis, elemental analysis, X-ray diffraction (XRD), thermogravimetric analysis and titration). The effect of pH was investigated showing optimum sorption at pH 4 for U(VI) and pH 5 for Eu(III). Uptake kinetics are relatively fast: the equilibrium was reached within 60–90 min; and the kinetic profiles were preferentially fitted by the pseudo-second order rate equation. Sorption isotherms are equally fitted by the Langmuir and the Sips equations; under optimal conditions maximum sorption capacity reaches 1.5 mmol U g−1 and 2.47 mmol Eu g−1. In bi-component solution, at pH close to 4.9, uranyl is enriched on the sorbent (higher selectivity coefficient) while maintaining high sorption capacities. The selectivity for Eu(III) sorption is higher at pH 2.3 but at the expense of a decrease in sorption capacities. Metal ions can be readily and fast desorbed using 0.5 M HCl solutions: 30–90 min are sufficient for achieving the complete desorption of U(VI) and about 95% of Eu(III) desorption. Sorption and desorption performances are maintained almost constant over 5 cycles of sorption/desorption: the sorbent can be efficiently recycled. Uranium was successfully recovered from alkaline leachate of a sedimentary dolostone ore material.

Rhein functionalized magnetic chitosan as a selective solid phase extraction for determination isoflavones in soymilk

A new solid-phase extraction mode was developed for separation some flavones from the complex interference system. In the experiment, rhein anchored on magnetic chitosan microparticles, prepared facilely without removal of the template molecule, was used as sorbents for the extraction of target analytes; after completion of the extraction process, Fe3O4 particles acted as carrier to retrieve rhein functionalized magnetic chitosan microparticles (RMCMPs) from the sample solution. RMCMPs showed excellent selective adsorption capacity of isoflavones. The result suggested that the method was useful for fast determination and quantification of isoflavones in soymilk. The RMCMPs were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transforms infrared spectrometer (FTIR).

Synthesis and characterization of magnetic chitosan microspheres as low-density and low-biotoxicity adsorbents for lake restoration

We propose a novel magnetic adsorbent for optimal Phosphorus (P) removal from the upper sediment layers. For this aim, magnetic chitosan microparticles were prepared using a reverse-phase suspension cross-linking technique. The resulting particles and suspensions were characterized using scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, magnetometry, thermogravimetric analysis, electrophoretic mobility and turbidity measurements. The hybrids are multicore particles consisting of well dispersed magnetite nanoparticles (approx. 10% w/w) homogeneously distributed within the biopolymer matrix. These microparticles can be easily separated from the water column and sediment using magnetic field gradients. Their P adsorption capacity is evaluated in batch conditions resulting in a maximum P adsorption capacity of ML = 4.84 mg g−1 at pH = 7. We demonstrate that these particles are excellent candidates to remove P from water column and also P mobile from the upper sediment layers due to two main reasons: they sediment slower and present lower potential toxicity (due to a their larger size) than conventional iron/iron oxide microparticles previously proposed for lake restoration.

Enzymatic degumming of soybean oil with magnetic immobilized phospholipase A2

In this study, magnetic immobilized phospholipase A2 (PLA2) was used to degum soybean oil such as magnetic particles crosslinked with sodium alginate PLA2 (PLA2-MPCSA), Magnetic chitosan microparticles containing PLA2 (PLA2-MCM), Fe3O4/P(GMA-EDGM-St) PLA2, and Fe3O4/SiOx-g-P(GMA) PLA2, successfully improving the recycling aspect of the degumming process. The highest enzyme loading and enzymatic activity (122.60 mg/g and 1289 U/g, respectively) were obtained using the magnetic immobilized PLA2-Fe3O4/SiOx-g-P(GMA) system. Compared to free PLA2, magnetic immobilized PLA2 had a broader pH-activity profile (pH 4.0–5.5) and activity remained stable between 50 and 70 °C. Enzymatic degumming with PLA2-Fe3O4/SiOx-g-P(GMA) was carried out over 5.0 h with an enzyme dosage of 0.24 g/kg, a pH of 5.0, and a temperature of 55 °C, resulting in residual phosphorus and free fatty acid contents of 9.8 mg/kg and 0.84 g/100 g, respectively. Moreover, magnetic immobilized PLA2 retained more than 80% of its initial activity even after 5 cycles of soybean oil degumming.

Capture and Direct Amplification of DNA on Chitosan Microparticles in a Single PCR-Optimal Solution.

While nucleic acid amplification tests have great potential as tools for rapid diagnostics, complicated sample preparation requirements inhibit their use in near-patient diagnostics and low-resource-setting applications. Recent advancements in nucleic acid purification have leveraged pH-modulated charge switching polymers to reduce the number of steps required for sample preparation. The polycation chitosan (pKa 6.4) has been used to efficiently purify DNA by binding nucleic acids in acidic buffers and then eluting them at a pH higher than 8.0. Though it is an improvement over conventional methods, this multistep procedure has not transformed the application of nucleic acid amplification assays. Here we describe a simpler approach using magnetic chitosan microparticles that interact with DNA in a manner that has not been reported before. The microparticles capture DNA at a pH optimal for PCR (8.5) just as efficiently as at low pH. Importantly, the captured DNA is still accessible by polymerase, enabling direct amplification from the microparticles. We demonstrate quantitative PCR from DNA captured on the microparticles, thus eliminating nearly all of the sample preparation steps. We anticipate that this new streamlined method for preparing DNA for amplification will greatly expand the diagnostic applications of nucleic acid amplification tests.

Removal of Reactive Blue 21 onto magnetic chitosan microparticles functionalized with polyamidoamine dendrimers

Chitosan/poly(amidoamine) (MCS/PAMAM) microparticles were prepared as magnetic adsorbents for removal of Reactive Blue 21 (RB 21) dye from aqueous solution. Characterization of these particles was carried out using scanning electron microscopy, Fourier transform-infrared spectroscopy, X-ray diffractometry and vibrating sample magnetometry. The results indicate that the magnetic chitosan microparticles (MCS) were functionalized with PAMAM dendrimers and maintained its intrinsic magnetic properties. The effects of initial pH, adsorbent dose, initial concentration, contact time and temperature on adsorption were investigated. Kinetic studies showed that the dye adsorption process followed a pseudo-second-order kinetic model but that the adsorption rate was also influenced by intraparticle diffusion. Equilibrium adsorption isotherm data indicated a good fit to the Langmuir isotherm. The maximum adsorption capacities obtained from the Langmuir model were 555.56, 588.24, 625.00 and 666.67mgg−1 at 303, 313, 323 and 333K, respectively. The thermodynamic parameters revealed the feasibility, spontaneity and endothermic nature of the adsorption. Recycling experiments confirmed the relative reusability of the adsorbent.

Low-cost, easy-to-prepare magnetic chitosan microparticles for enzymes immobilization

Extremely simple procedures for the preparation of magnetic chitosan enzyme carriers have been developed and used for the immobilization of lipase and β-galactosidase as model enzymes. In the first case commercially available magnetite microparticles were entrapped in chitosan gel, while in the second case magnetic iron oxides microparticles were synthesized in chitosan matrix from ferrous sulfate using microwave irradiation. Immobilized enzymes showed long-term stability without leaching of enzyme from the support and enabled their repeated use without significant loss of activity.

Removal of lead(II) from aqueous solution with ethylenediamine-modified yeast biomass coated with magnetic chitosan microparticles: Kinetic and equilibrium modeling

The adsorption of Pb(II) ions from aqueous solution with ethylenediamine-modified yeast biomass coated with magnetic chitosan microparticles (EYMC) was studied in batch adsorption system. The adsorption of Pb(II) ions increased with the rising pH and a higher adsorption capacity was achieved at the pH 4.0–6.0. The experiment data was well matched by Langmuir model and Freundlich model, while Langmuir model showed the best description. The maximum adsorption capacities obtained by Langmuir model were 121.26, 127.37 and 134.90mgg−1 at 20, 30 and 40°C, respectively. Kinetic studies indicated that the pseudo-second-order model was appropriate to describe the adsorption process and film diffusion maybe governed the rate of the adsorption. Thermodynamic studies revealed that a spontaneous and endothermic adsorption process. The adsorbents, EYMC can be well recovered by 0.1M EDTA.

Study on Magnetic Chitosan Microparticles for Rapid Removal of Heavy Metals

The magnetic chitosan microparticles were prepared by microemulsion method and raid removal of Cd(Ⅱ) and Pb(Ⅱ). Batch tests were carried out to investigate the adsorption performance. It was found that adsorption of Pb2+ and Cd2+ was dependent on pH, and increasing the pH is favorable for heavy metal ions removal. The sorption isotherms of the adsorbent for these metals fitted better with Freundlich model than the Langmuir model, with maximum adsorption capacities of 69.83 mg/g and 18.03 mg/g for Pb2+ and Cd2+, respectively. The adsorption equilibrium was reached within 15 min. The temperature effects revealed that the adsorption capacity increased significantly with increasing temperature, and the adsorption process was endothermic in nature at 25°C to 75°C.

Significant delivery of tacrine into the brain using magnetic chitosan microparticles for treating Alzheimer's disease

Alzheimer's disease (AD) is a progressive degenerative disorder of the brain characterized by a slow, progressive decline in cognitive function and behavior. As the disease advances, persons have a tough time with daily tasks like using the phone, cooking, handling money or driving the car. AD affects 15 million people worldwide and it has been estimated that AD affects 4.5 million Americans. Tacrine is a reversible cholinesterase inhibitor used for treating mild to moderate AD. In the present study, an attempt was made to target the anti-Alzheimer's drug tacrine in the brain by using magnetic chitosan microparticles. The magnetic chitosan microparticles were prepared by emulsion cross-linking. The formulated microparticles were characterized for process yield, drug loading capacity, particle size, in vitro release, release kinetics and magnetite content. The particle size was analyzed by scanning electron microscope. The magnetite content of the microparticles was determined by atomic absorption spectroscopy. For animal testing, the microparticles were injected intravenously after keeping a suitable magnet at the target region. The concentrations of tacrine at the target and non-target organs were analyzed by HPLC. The magnetic chitosan microparticles significantly increased the concentration of tacrine in the brain in comparison with the free drug.