Suspension Cross-linking Research Articles

Exploring the potent hydrolytic activity of chitosan-cerium complex microspheres resin for organophosphorus pesticide degradation

Chitosan is a biocompatible, non-toxic and renewable natural basic polysaccharide that can be cross-linked and reacted with Ce(IV) to form a physiologically active chitosan-Ce(IV) complex. To investigate this novel complex and its potential to hydrolyze phosphate ester bonds, chitosan-cerium complex microspheres resin (CS-CCMR) was prepared from chitosan and ceric ammonium nitrate by reversed-phase suspension cross-linking polymerization. CS-CCMR was characterized, its ability to hydrolyze disodium p-nitrobenzene phosphate (PNPP2Na) and organophosphorus pesticides was investigated, and the hydrolytic mechanism was explored. CS-CCMR was composed of dark yellow microspheres with smooth surfaces and dense pores. It was found that CS-CCMR contained 4.507 mg/g Ce(IV), indicating that coordination polymerization between Ce(IV) and chitosan was successful. The presence of Ce(IV) in CS-CCMR was confirmed by multiple analytical methods and it was found that coordination of Ce(IV) by chitosan was mediated by the nitrogen atom of the amino group and the oxygen atom of the hydroxyl group of chitosan. It was shown that CS-CCMR efficiently hydrolyzed the phosphate ester bonds of PNPP2Na and five organophosphorus pesticides. Hydrolysis of PNPP2Na is potentially accomplished by charge neutralization and nucleophilic substitution. The mechanism of parathion degradation by CS-CCMR involves modification of the nitro group to give aminoparathion, followed by cleavage of the P–O bond to generate diazinphos. Consequently, the novel chitosan-Ce(IV) complex exhibits great efficiency for hydrolysis of phosphate ester bonds and CS-CCMR is expected to be developed as an agent to reduce the possibility of contamination of fruit and vegetable drinks by organophosphorus pesticides.

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.

Co-adsorption and selective-adsorption of heavy metals and dyes from aqueous solution by bio-based humus/chitosan hydrogels

An eco-friendly adsorbent was prepared by reverse suspension crosslinking method to remove multiple pollutants from aqueous solution. Both raw materials, derived from humus (HS) and chitosan (CS), are biodegradable and low-cost natural biopolymers. After combining HS with CS, the adsorption capacity was significantly improved due to compensation effects between the two components. HS/CS exhibited the features of amphoteric adsorption through pH adjustment, enabling it to adsorb not only anionic pollutants (Methyl Orange (MO) and Cr(VI)), but also cationic ones (Methylene Blue (MB) and Pb(II)). The adsorption capacities were approximately 242 mg/g, 69 mg/g, 188 mg/g and 57 mg/g for MO, Cr(VI), MB and Pb(II), respectively. HS/CS showed a slight preference for MO in MO/Cr(VI) co-adsorption system, whereas strong selectivity for MB over Pb(II) in MB/Pb(II) system under acidic condition (pH<3.0). This selective behavior would allow for potential applications in separating MB/Pb(II) effluents and selectively recycling Pb(II) in acidic environment. The isothermal and kinetic adsorption behaviors followed Langmuir model and pseudo-second-order model, respectively. The density functional theory (DFT) confirmed that the interaction between metal ions and adsorbents was primarily attributed to chelation and electrostatic adsorption, owing to nitric and oxygenic functional groups. Whereas, the adsorption mechanisms for dyes were involved in electrostatic attraction, H-bond and π–π bond, due to available hydrogen, oxygen, nitrogen atoms and aromatic groups on the surface of adsorbent and adsorbates. The adsorbent could be efficiently regenerated and retained over 90% of its adsorption capacity after five cycles, which has a potential for practical applications in water treatment.

Fe3O4 magnetic nanoparticles-loaded thermoresponsive poly(N-vinylcaprolactam)-g-galactosylated chitosan microparticles: investigation of physicochemical, morphological and magnetic properties

A novel thermoresponsive magnetic hydrogel microparticle system was obtained by magnetic nanoparticles (MNPs) combined with poly(N-vinylcaprolactam)-g-galactosylated chitosan (GC) (PNVCL-g-GC) hybrid hydrogel. Fe3O4@PNVCL-g-GC microparticles (MPs) were synthesized by the suspension crosslinking method and the Fe3O4 MNPs were successfully encapsulated in the hybrid hydrogel with good magnetism. Fe3O4@PNVCL-g-GC MPs were characterized by ATR-FTIR, LCST, SEM-EDAX, particle size, zeta potential, TGA and VSM analyses. The size distribution of the spherical Fe3O4@PNVCL-g-GC MPs at room temperature was in the range of 390-530 nm, while it was measured as ∼220–340 nm above the LCST. The cytocompatibility and hemocompatibility of the Fe3O4@PNVCL-g-GC MPs were confirmed by in vitro ISO analyses. In conclusion, biocompatible, temperature- and magnetic-responsive small-size Fe3O4@PNVCL-g-GC MPs with enhanced mechanical stability were developed which could have the potential for a variety of biomedical applications such as controlled release systems, in situ bioactive agents carrier, and anti-cancer therapy in the future.

Isotherm, Thermodynamics, and Kinetics of Methyl Orange Adsorption onto Magnetic Resin of Chitosan Microspheres.

Severe environmental pollution problems arising from toxic dyestuffs (e.g., methyl orange) are receiving increasing attention. Therefore, dyes' safe removal has become a research hotspot. Among the many physical-chemical removal techniques, adsorption using renewable biological resources has proved to be more advantageous over others due to its effectiveness and economy. Chitosan is a natural, renewable biopolymer obtained by deactivated chitin. Thus, the magnetic resin of chitosan microspheres (MRCM), prepared by reversed-phase suspension cross-linking polymerization, was used to remove methyl orange from a solution in a batch adsorption system. The main results are as follows: (1) The results of physical and swelling properties of MRCM indicated that MRCM was a type of black spherical, porous, water-absorbing, and weak alkali exchange resin, and it had the ability to adsorb methyl orange when it was applied in solutions above pH 2.0. (2) In batch adsorption studies, the maximum adsorption capacity was obtained at pH 5; the adsorption equilibrium time was 140 min; and the maximum adsorption was reached at 450 mg/L initial concentration. (3) Among the three isotherm adsorption models, Langmuir achieved the best fit for the adsorption of methyl orange onto MRCM. (4) The adsorption thermodynamics indicated that the adsorption was spontaneous, with increasing enthalpy, and was driven by the entropy. (5) The pseudo-second-order kinetics equation was most suitable to describe the adsorption kinetics, and the adsorption kinetics was also controlled by the liquid-film diffusion dynamics. Consequently, MRCM with relatively higher methyl orange adsorption exhibited the great efficiency for methyl orange removal as an environment-friendly sorbent. Thus, the findings are useful for methyl orange pollution control in real-life wastewater treatment applications.

Preparation of chitosan-like magnetic composite microspheres and their adsorption properties for Cu (II)

The novel magnetic composite microspheres (Fe3O4/HAD-C) coated with Fe3O4 were fabricated by inverse suspension cross-linking method, where glutaraldehyde was used as a crosslinking agent. Magnetic Fe3O4 particles and Hexamethylene Diamine Cellulose was prepared respectively by the chemical coprecipitation method and grafting amino group onto microcrystalline Cellulose. The scanning electron microscope, laser particle size analyzer, X-ray diffractometer, and thermogravimetric analyzer were used to characterize the magnetic Fe3O4/HAD-C composite microspheres. The findings demonstrate that the Fe3O4/HAD-C composite microspheres were spherical and well dispersed with the size range between 0.3 μm and 1.2 μm, and possessed super paramagnetic property with 39.72 emu·g−1. The mass of Fe3O4 in the composite is about 37.11 %. By using an adsorption study, the removal of Cu (II) from heavy metal wastewater by Fe3O4/HAD-C was examined. The findings showed that the composite microsphere made of Fe3O4/HAD-C effectively absorbed Cu (II). The entire adsorption procedure follows the Langmuir isothermal adsorption model and pseudo-second order kinetics. Fe3O4/HAD-C also had high reusability and stability. Even after 5 cycles of adsorption and desorption, Fe3O4/HAD-C still achieve 32.45 mg g−1. Environmentally friendly and effective, the unique magnetic chitosan-like composite microspheres (Fe3O4/HAD-C) developed in this study.

Promising Methods of Antibacterial Finishing of Textile Materials.

A review article, containing information on the options, possibilities, and prospects for the development of antibacterial finishing of textile materials, is presented. A wide range of products designed to impart antibacterial, antimicrobial, and antiviral properties to textile materials is considered. The main factors determining the appropriate decision on the technological and functional choice of the protective composition are presented, including the nature of the fiber-forming polymer, the tasks that the resulting material is designed to solve, and its application options. Compositions providing the required effect of destruction of the pathogenic flora and their application technologies are described. Special attention is paid to antimicrobial agents based on silver nanoparticles. Nanoparticles of this metal have a detrimental effect on antibiotic-resistant strains of bacteria; their effectiveness is higher as compared to a number of well-known antibiotics, for example, penicillin and its analogues. Silver nanoparticles are harmless to the human body. Acting as an inhibitor, they limit the activity of the enzyme responsible for oxygen consumption by single-cell bacteria, viruses, and fungi. In this case, silver ions bind to the outer and inner proteins of the bacterial cell membranes, blocking cellular respiration and reproduction. Various options to apply microencapsulation methods for the implementation of antibacterial finishing are considered, including: phase separation, suspension crosslinking, simple and complex coacervation, spray drying, crystallization from the melt, evaporation of the solvent, co-extrusion, layering, fluidized bed spraying, deposition, emulsion and interphase polymerization, layer-by-layer electrostatic self-assembly etc. All presented technologies are at various development stages—from the laboratory stage to production tests, they all have certain advantages and disadvantages. The accelerated development and implementation of the described methods in production of textile materials is relevant and is related to the existing complex epidemiological situation in the world.

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.

Chitosan-Derived Magnetic Nanomaterials: Synthesis, Characterization, and Nitrite Adsorption in Water

Nitrite is one of the main pollutants in the water worldwide. In this study, we have applied the reverse suspension crosslinking methodology based on chitosan (CS) and Fe3O4 (FeO) to synthesize the novel magnetic nanomaterial of chitosan (CS-FeO). The physical and chemical properties of CS-FeO were further characterized by scanning electron microscopy, particle size distribution, thermogravimetry, fluxgate magnetometer, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and energy dispersive spectroscopy. Results revealed that CS-FeO showed high thermal stability in the temperature ranging from 50 to 200°C. CS-FeO showed high crystallinity and magnetism and was easily and quickly separated from aqueous solution in the presence of an external magnetic field. The molecular structure of CS-FeO showed that the core-shell structure of CS-FeO was established with FeO as the core and CS as the shell. Furthermore, the adsorption rate of nitrite by CS-FeO reached 65.83 ± 0.76 % under optimal conditions. Moreover, CS-FeO showed high regeneration capability with Na2SO4 used as the eluent. Our study demonstrated evidently that CS-FeO can be potentially used to remove nitrite from drinking water sources and industrial wastewater, suggesting the promising future of the application of CS-derived magnetic nanomaterials in the areas of environmental protections.

Development of Chitosan Functionalized Magnetic Nanoparticles with Bioactive Compounds.

In this study, magnetic maghemite nanoparticles, which belong to the group of metal oxides, were functionalized with chitosan, a non-toxic, hydrophilic, biocompatible, biodegradable biopolymer with anti-bacterial effects. This was done using different synthesis methods, and a comparison of the properties of the synthesized chitosan functionalized maghemite nanoparticles was conducted. Characterization was performed using scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). Characterizations of size distribution were performed using dynamic light scattering (DLS) measurements and laser granulometry. A chitosan functionalization layer was confirmed using potentiometric titration on variously synthesized chitosan functionalized maghemite nanoparticles, which is important for further immobilization of bioactive compounds. Furthermore, after activation of chitosan functionalized maghemite nanoparticles with glutaraldehyde (GA) or pentaethylenehexamine (PEHA), immobilization studies of enzyme cholesterol oxidase (ChOx) and horseradish peroxidase (HRP) were conducted. Factors influencing the immobilization of enzymes, such as type and concentration of activating reagent, mass ratio between carrier and enzyme, immobilization time and enzyme concentration, were investigated. Briefly, microparticles made using the chitosan suspension cross-linking process (MC2) proved to be the most suitable for obtaining the highest activity of immobilized enzyme, and nanoparticles functionalized with chitosan using the covalent binding method (MC3) could compete with MC2 for their applications.

Flexible And Recyclable PPy‐TiO2@WO3 Photocatalyst Supported By Cellulose Aerogel Beads

AbstractPolypyrrole (PPy)‐TiO2@WO3 catalyst supposed by cellulose aerogel beads was synthesized using inverse suspension crosslinking approach. The resulting particles were small and well‐crystallized according to scanning and transmission electron microscopies. The efficiency of the resulting photocatalysis was tested relative to degradation of tetraethylated rhodamine (RhB), which was judged by solution discoloration and also by RhB content decrease. Excellent photocatalytic activity of cellulose aerogel (CE)‐PPy‐TiO2@WO3 beads was attributed to the synergy between TiO2 and WO3, which widened material absorption bandedge and improved migration efficiency of photogenerated electrons and holes. Presence of black PPy widened absorption band edge further promoting photogenerated electron and hole separation. More importantly, presence of macro‐porous CE increased optical absorption of this composite photocatalyst and helped photocatalyst to retain its structural integrity during repeated recycling. If needed, photocatalyst can be easily removed from the reaction solution to prevent secondary pollution. Our complex CE‐PPy‐TiO2@WO3 bead‐like photocatalyst also demonstrated good mechanical strength and excellent flexibility, which allowed it to be folded and bent. We proposed photocatalytic mechanisms responsible for processes involving CE‐PPy‐TiO2@WO3 beads, understanding of which will help to improve the photocatalytic performance of this material even further. Catalysts based on CE‐PPy‐TiO2@WO3 beads can be used in complex environments and small spaces because of their flexibility and recyclability. It might be especially useful for applications in difficult‐to‐reach places (for example sandy places or narrow openings), in which it is difficult to place or recover a catalyst.

Nitrile hydratase mediated green synthesis of lactamide by immobilizing Rhodococcus pyridinivorans NIT-36 cells on N, N′-Methylene bis-acrylamide activated chitosan

In this paper green synthesis of an important commodity chemical lactamide has been undertaken using chitosan immobilized Rhodococcus pyridinivorans NIT-36 harbouring nitrile hydratase (NHase) enzyme. The cells immobilization (300 mg/g) is based on the partial entrapment of cells by suspension cross-linking technique facilitated by N, N′-Methylene bis-acrylamide. In the repeated-use experiments, the immobilized cells retained 80% of its initial activity when stored at 4 °C for 30 days. NHase activity of free and immobilized cells was studied over temperature ranging from 25 °C to 60 °C. The activity for free cells showed a sharp decline of 70% when the reaction temperature was elevated from 45 °C to 50 °C whereas chitosan immobilized cells retained their activity in the same temperature range. A fed-batch reaction was designed and the immobilized cells showed 100% similar enzymatic pattern for five consecutive rounds which gradually decreased in following cycles. A volumetric productivity of 20 g/L and catalytic productivity of 8.33 g/g dcw/h for lactamide were achieved.

Preparation of magnetic polyethylenimine lignin and its adsorption of Pb(II)

In this paper, magnetic polyethyleneimine lignin (M-Lignin-PEI) was prepared by a reversed-phase suspension crosslinking method to remove Pb (II) form aqueous solutions. SEM, FT-IR, TGA, XRD and VSM technology were employed to explain their structures. Batch adsorption experiments for Pb (II) were carried out to estimate their adsorption performance. Results showed that lignin successfully grafted with polyethyleneimine and coated on the surface of Fe3O4 with a saturation magnetization of 24.08 emu/g, which could achieve good solid-liquid separation. In addition, the experiment results indicated that the adsorption of Pb (II) by M-Lignin-PEI was in line with Langmuir model, and the adsorption process could be described by a pseudo-second-order model, suggesting that Pb (II) adsorption onto sorbents were a chemical process and monolayer adsorption. The maximum adsorption capacity of M-Lignin-PEI for Pb (II) could reach 96.60 mg/g and the removal rate was 99.73%. Moreover，the lead-loading M-Lignin-PEI could be easily regenerated with only 15% decrease of adsorption capacity after five times regeneration.

Lipase-immobilized chitosan-crosslinked magnetic nanoparticle as a biocatalyst for ring opening esterification of itaconic anhydride

Nano-magnetic biocatalyst particles, lipase-immobilized chitosan-crosslinked magnetic nanoparticles (LCMNs) were prepared by a new approach integrated from magnetic nanoparticle preparation, in situ thin layer coating and crosslinking of chitosan, and enzyme immobilization method. Thin layer coating of magnetic (Fe3O4) by crosslinked chitosan nanoparticles were prepared by reacting FeCl3.6H2O and sodium acetate in ethylene glycol, followed by suspension cross-linking using citric acid on the hydroxyl and amine group of chitosan at neutral pH. The resulting nanoparticles were used to immobilize the lipase from Candida antarctica Lipase B by linking using glutaraldehyde. The particles in each step were characterized by Fourier transform infrared spectrometry (FT-IR), vibrating-sample magnetometer measurements (VSM), and transmission electron microscopy (TEM). The magnetic biocatalyst, LCMN was found to have high storage stability and reusability due to the tightly crosslinked structure of chitosan and covalent bond immobilization. LCMNs were used for the oligomerization of itaconic anhydride by ring opening esterification, and the results were compared with those from free lipase and commercial immobilized lipase. The molecular mass of the products obtained with the biocatalysts showed similar Mn profiles with 308–381. This process represents a green approach for the preparation of both biobased magnetic biocatalysts and functional oligo-esters, and can be applied for both the immobilization of other enzymes and the utilization of photo-curable functional esters as biobased functional materials.

Peanut Suspension Crosslinking by Means of Microbial Transglutaminase Studied with the Indentation Technique

This work deals with the ability to get a three dimensional network with a peanut suspension crosslinked with a microbial transglutaminase (mTG) enzyme. Suspensions (made of solid particles suspended in water) composed of grinded white peanut mixed with water (dry extract = 40%) were incubated with_mTG (0.3% w/w) after alteration of the ionic strength. The ionic strengths were adjusted with NaCl on a range from Ic = 0 mol/L to Ic = 1.2 mol/L. The strength of the assembled structure was then assessed using penetrometry in order to evaluate the impact of the ionic strength on the gel strength of the newly‐formed complex. The scope of gel strengths obtained fluctuates between a minimum of 0.25 N for the condition Ic = 0 mol/L and a maximum of 0.80 N for the condition Ic = 0.8 mol/L. It has also been found that other parameters such as the temperature and the time of incubation have a lesser impact on the final strength of the product. The end‐product of this enzymatic catalysis discloses chemical gel‐like properties, such as irreversible liquid–solid transition with a visco‐elastico‐plastic response to indentation assessment.

Preparation and applications of magnetic microspheres

Magnetic microspheres are widely applied in many fields such as biomedicine and separation engineering, such as immobilizing enzyme, targeting drug carrier, nuclear magnetic resonance imaging, cell labeling and isolation, nucleic acid and protein purification, environmental management etc. With the constant update of new nanomaterials preparation technology, much progress has been made in both the preparation and applications of magnetic microspheres. The preparation methods for magnetic microspheres could be divided into four categories. (1) Embedding. Magnetic nanoparticles are embedded in the microsphere matrix while the microspheres are generated, which could be subdivided into heterogeneous polymerization, emulsification-solvent evaporation, membrane emulsification and microfluidic method, reversed phase suspension cross-linking, Stober method, polymer-induced colloidal aggregation, etc. (2) Template-mediated assembly. Magnetic nanoparticles are assembled inside or on the surface of the template microspheres, including swelling method, adsorption method and electrostatic self-assembly method. (3) Template-mediated in situ generation. Magnetic nanoparticles are in situ generated by coprecipitation, precipitation-oxidation and organic precursor thermolysis in the interior or on the surface of the template microspheres. (4) Solvo(hydro)thermal method. Magnetic microspheres are formed in Teflon-lined stainless steel container under high temperature and pressure. The research progress of magnetic microspheres in recent years are reviewed in this paper according to preparation methods. The preparation process, characters, surface modification and applications of magnetic microspheres are also introduced.

Magnetic Fe3O4-chitosan micro- and nanoparticles for wastewater treatment

ABSTRACTIn this study, first, magnetic nanoparticles (MNP) were synthesized using a coprecipitation method and the synthesized particles were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and vibrating sample magnetometry (VSM). According to DLS and VSM analyses results, it was seen that the size of the MNP was smaller than 10 nm and they exhibited superparamagnetic properties, respectively. Then, magnetic Fe3O4-chitosan micro/nanoparticles were synthesized using a suspension cross-linking method in the presence of the MNP. Fe3O4-chitosan microparticles (Fe3O4-CMs) and Fe3O4-chitosan nanoparticles (Fe3O4-CNs), which have different structural, morphological, and magnetic properties, were obtained. All of the particles were characterized using transmission electron microscopy (TEM), FTIR, TGA, DLS, and VSM. In the second part of the study, the dye adsorption properties of the two different adsorbents from aqueous solution were investigated. For these purposes, Bromothymol Blue (BB) was used as a dye and the parameters affecting adsorption of BB (contact time, initial dye concentration, temperature and pH) were investigated. When the optimum adsorption conditions were provided for each adsorbent, the adsorption capacities of Fe3O4-CNs and Fe3O4-CMs were 82.2 and 193.3 mg/g, respectively.

Preparations and properties of drug-eluting embolization microspheres based on modified gelatin

ABSTRACTEmbolization using microspheres plays an important role in interventional cancer therapy. The drug-eluting embolization microspheres were prepared via reverse suspension crosslinking of gelatin, followed by modification of the cross-linked microspheres. The microspheres displayed regular spherical shapes with size distribution ranging from 180 μm to 350 μm. The negatively charged groups (COO−) were introduced into the microspheres which could load positively charged doxorubicin with loading rates as high as 26.1% and 34.0% in 1 and 12 h, respectively. The high drug-loading rates were ascribed to ionic interaction between carboxyl groups and doxorubicin. The drug release profile showed the modified microspheres (MMS) have a sustained release manner compared with non-MMS in phosphate buffered saline (PBS). The MMS were almost completely degradated after 20 days. Cytotoxicity assay certified that the MMS were non-cytotoxic, and could be potentially used as biocompatible materials.

Facile Preparation of Ion-Imprinted Chitosan Microspheres Enwrapping Fe3O4 and Graphene Oxide by Inverse Suspension Cross-Linking for Highly Selective Removal of Copper(II)

A novel magnetic copper imprinted chitosan/graphene oxide composite biomaterial was prepared by the combination of ion imprinting and inverse suspension cross-linking for selective adsorption of Cu(II) from aqueous solution. High adsorption capacity for copper was obtained with a low level cross-linking and the addition of graphene oxide and triglycine in the preparing process. The prepared ion-imprinted magnetic chitosan polymer microsphere (CS-IIP) was characterized by FT-IR, TGA, SEM, and EDX. The results indicated that the CS-IIP was prepared successfully and showed good thermostability. Effects of different experimental conditions like pH value, contact time, and Cu(II) concentration on the adsorption capacity were investigated. The adsorption process follows the Freundlich isotherm equation and the pseudo-second-order kinetic model. The highest adsorption capacity of CS-IIP was 132 mg g–1. The calculation of selective factors and relative selectivity factors of CS-IIP for Cu2+/M2+ (M = Zn, Ni, Co, o...

Development of reusable magnetic chitosan microspheres adsorbent for selective extraction of trace level silver nanoparticles in environmental waters prior to ICP-MS analysis

Solid-phase extraction (SPE) based on reusable magnetic chitosan microspheres was coupled with ICP-MS for separation and quantification of silver nanoparticles (AgNPs) in the presence of silver ions in environmental water samples. The monodisperse magnetic chitosan microspheres with an average size of 2µm were engineered using suspension cross-linking technique, and characterized and investigated for its application as SPE adsorbent. Parameters affecting the SPE were optimized, and the best performance was achieved by extracting a 20mL sample (pH 4.5) with 10mg adsorbent for 90min, followed by elution with 1mL 1% (w/v) thiourea in 10% (v/v) nitric acid for 10min. The detection limit, calculated as 3s (s, standard deviation for 11 blank readings), for three AgNPs coated with polyvinyl pyrrolidone (PVP), citrate and polyvinyl alcohol (PVA) and sizes of 31, 40, 46nm, respectively, were in the range of 0.016‒0.023μg/L. The repeatability and reproducibility (RSD, n=7) at a spiking level of 0.1μg/L AgNPs were 4.2% and 8.1%, respectively. The developed method has been applied in the analysis of AgNPs in river, lake and wastewater samples, with excellent extraction efficiencies (84.9‒98.8%) for AgNPs at spiking levels of 0.86 and 8.70μg/L. The cationic chitosan microspheres showed good species selectivity and reusability for extraction of AgNPs in the presence of Ag+, and hence the proposed method is simple, cost effective and environmentally friendly.