Cross-linked Microspheres Research Articles

Effectiveness of a new green technology for metal removal from contaminated water

Water pollution by heavy metals is a matter of growing concern due to their potential toxicity for biota. The development of new and cost-effective remediation strategies is a priority in this field. For this purpose, a green technology, consisting of organic waste made up of a composite of water hyacinth dry matter and sodium alginate in microsphere form, was tested for its potential to adsorb lead and cadmium in river water samples.The water hyacinth‑sodium alginate composite molecular conformation was analysed first in order to obtain the potential energy surfaces. A high dipole moment, useful for the adsorption of heavy metals, was found. Accordingly, the cross-linked microspheres were prepared by combining water hyacinth dry matter and sodium alginate in a 1:1 ratio. Their metal adsorption and any effect on the natural microbial river community were verified with laboratory microcosm experiments lasting 11 days, using river water spiked with lead and cadmium (1 mg/L each). For this purpose, chemical (metal concentrations) and microbial (microbial abundance, viability and taxonomic composition) analyses were performed. Moreover, the ecotoxicity (with Vibrio fischeri - ISO 11348-3:2007) of water samples from microcosms in the presence/absence of the microspheres and metals was assessed. Effective concentrations (EC20 and EC50) of Pb and Cd were also determined. Finally, electron microscopy analyses were performed with a Field Emission Scanning Electron Microscope (FE-SEM) to visualize the metal adsorption capacity of the microspheres and investigate the metal distribution on the spheres (adsorbed on the surface or inside).The overall results showed that the microspheres were able to remove high heavy metal concentrations (about 1 mg/L) from river water in a short time (at 96 h just 1.3% and 5.8% of the Pb and Cd initial concentrations were detected) and no ecotoxicological effects were recorded. Moreover, the microspheres had a positive effect on the microbial community by promoting an increase in live cell numbers, probably through the release of organic carbon. Further analyses (at about four months) showed that the microspheres were able to keep metals adsorbed for a long time.These results show that the green technology proposed is an effective remediation method for Pb and Cd removal from river water and is very promising, not least because of its low cost.

Stability studies of collagen-based microspheres with Calendula officinalis flower extract

Controlled drug delivery technology represents the more rapidly advancing area in recent years. Gelatin and collagen-gelatin microspheres were produced by emulsion technique using distilled water and paraffin oil containing 1% Span 85. Then microspheres were cross-linked by ethyl-3(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) mixture. Microspheres have been also cross-linked using dehydrothermaltreatment (DHT) to compare chemical cross-linking with physical cross-linking. Collected microspheres were loaded with Calendula officinalis flower extract, as drug model. Morphological analysis revealed homogeneous microspheres characterized by an average diameter 21 μm and 26 μm for gelatin and collagen-gelatin microspheres, respectively. The largest amount of Calendula officinalis flower extract was entrapped in DHT cross-linked microspheres. Active substance contained in collagen-gelatin microspheres was released much faster than that released from gelatin microspheres. Finally, after incubation of microspheres in acetate buffer, their sizes were 9.77- and 5.76-fold smaller reduced in the case of gelatin and collagen-gelatin samples, respectively.

PREPARATION AND CHARACTERIZATION OF NITRENDIPINE LOADED GRAFTED COPOLYMER MICROSPHERES: A PRELIMINARY STUDY

Objectives: Developing countries like India suffers mostly from cardiovascular problems and kidney failure. An antihypertensive drug is mainly used to avoid the cardiovascular problems and kidney failure. Nitrendipine is a calcium antagonist widely used in the treatment of hypertension. The bioavailability of drug, when administered orally, is low. Sustained drug delivery systems are using microspheres emerging as an effective method to increase the bioavailability of the drug. The current work involves the encapsulation of nitrendipine - acrylamide grafted chitosan which helps to overcome poor solubility and hydrophobic nature of the nitrendipine. This will enhance the drug dissolution and reduce the side effects of the antihypertensive drug.Methods: By emulsion cross-linking method, grafted copolymers were prepared. The physicochemical interactions between the drug and grafted copolymer were analyzed by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC).Results: Encapsulated drug and grafted copolymer were characterized by FTIR to understand the chemical interactions and to identify the functional groups present. Morphology and particle size of the grafted copolymer with drug and without drug were assessed by SEM. DSC was used to identify the melting endotherms of a drug, copolymer cross-linked microspheres, and drug encapsulated microspheres.Conclusion: Thus, the drug encapsulated grafted copolymer increases the hydrophilic character and thereby making the polymers feasible for functioning as drug carriers for sustained drug delivery system.

Preparation of Porous Cross-linked Microsphere through Electrospraying combined with Photopolymerization

Preparation of Porous Cross-linked Microsphere through Electrospraying combined with Photopolymerization

Research on the rheological properties of cross-linked polymer microspheres with different microstructures

Polyacrylamide is widely used in various fields as the controlled releasing of medicines, paper and other basic fields. For purposes of enhancing oil recovery, polymer microspheres are utilized as in-depth flooding agent for their excellent performance of water shutoff and deep profile control. To explain the thickening properties of copolymer intermolecular, study of the interaction between solution properties and microspheres structure is necessary. Cross-linked polymer microspheres with different microstructures were synthesized by changing the crosslink ratio Nx. When the mass concentration was sufficiently high, the aggregated microspheres would be broken up under the shear stress; therefore, the dispersed system exhibited shear-thinning behavior. At lower mass concentrations, the rheological properties were markedly different. With an increase of Nx(0.5%-10%), the microspheres behaved as pseudoplastic fluid, Newtonian fluid and dilatant fluid in turn with the increase of shear rate. Additionally, the critical mass concentration (above the mass concentration, the cross-linked microspheres displayed shear-thinning, thixotropic behavior, a sol-gel transition and creep-recovery behavior) increased with the increasing crosslink ratio.

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.

Novel ferrocene-containing organosilicon polymers and uniform microspheres prepared by free radical copolymerization: Precursors for magnetic Si-C-Fe-(O) nanomaterials

Ferrocene-containing organosilicon polymers demonstrate wide applications in catalysts, redox sensors, ceramic nanomaterials and nanolithography fields. However, most synthesis methods for ferrocene-containing organosilicon polymers require either strict water-free and oxygen-free conditions or the presence of platinum complex catalysts. In this contribution, the free radical copolymerization of 1, 1′‑bis(dimethylvinylsilyl)ferrocene (DVFc) and trimethylolpropane trimethacrylate (TMPTMA) was achieved to construct either soluble branched ferrocene-containing organosilicon polymers or uniform cross-linked microspheres only through the feed ratio tuning of the two monomers. The structures of copolymer and cross-linked microspheres have been characterized by one-dimensional nuclear magnetic resonance (1D NMR) and two-dimensional (2D) NMR measurements. Furthermore, the novel organosilicon polymers could be employed as preceramic precursors to prepare magnetic Si-C-Fe-(O) ceramics with favorable ceramic yield at high temperature. The nanocrystals-containing ceramics magnetism could be tuned through copolymer nature or pyrolysis condition variations.

Preparation and characterization of monodisperse porous cross-linked PGMA microspheres with controllable morphology and structure

ABSTRACTIn this study, we prepared a porous poly (glycidyl methacrylate) (PGMA) microsphere by modified seed-swelling emulsion polymerization. The structure and morphology of the porous microspheres were characterized by SEM. We discussed the effect of the ratio of crosslinker and monomer on microsphere formation and micropores, and found the most favorable conditions for the preparation of porous PGMA microspheres. The great structure and specific surface area of the porous microspheres and the active functional groups on the surface indicate a wide range of applications.

Synthesis and characterization of injectable chitosan cryogel microsphere scaffolds

ABSTRACTTreatment of tissue defects involves invasive processes such as implanting the tissue engineered scaffold to the defected area. Injectable scaffolds are increasingly being developed to achieve tissue regeneration in a less invasive manner. In this study, injectable chitosan cryogels in the form of microspheres were synthesized combining the water in oil emulsification method with the crosslinking of microspheres during cryogelation. The effects of polymer ratio, crosslinker concentration, cryogelation temperature, and stirring speed on the resulting cryogels’ chemistry, pore morphology, microsphere size, swelling ratio, degree of crosslinking, and degradation rate were examined for a possible noninvasive tissue engineering application. Microspheres with optimized properties were developed with an average pore and particle size of 5.50 ± 0.63 and 220.11 ± 25.58 µm at a chitosan ratio of 1%, glutaraldehyde concentration of 3%, reaction temperature of −16°C, and stirring rate of 1,000 rpm.

Preparation and Properties of Cross-Linked Polysiloxane Microspheres for Light-Scattering

The narrow particle size distribution of poly (vinyl silicone) microspheres were prepared by the hydrolysis-polycondensation method with vinyl silane (VTMS) as raw materials. And the influences of pH value, oil/water ratio on the morphology, particle size and distribution of the microspheres were studied. The results shows that the particle size of microspheres decrease with the increasing of the PH value of polymerization, and the particle size has no specific linear relationship with the PH value of hydrolysis reaction, while the oil-water ratio is smaller, single particle size distribution is more narrow, more uniform distribution.

Co-delivery of zinc and 5-aminosalicylic acid from alginate/N-succinyl-chitosan blend microspheres for synergistic therapy of colitis

The present study developed novel zinc ion cross-linked alginate/N-succinyl-chitosan (NSC) blend microspheres (MS) for co-delivery of zinc and 5-aminosalicylic acid (5-ASA) for synergistic therapy of colitis. Physicochemical characterization of blend MS was assessed using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and energy dispersive X-ray spectrometer (EDS). In vitro release studies demonstrated that blend MS has a pH-dependent release property. Both 5-ASA and zinc have lower release in acid medium and higher release in colonic environment. The therapeutic efficacy of zinc cross-linked blend MS was evaluated using induced-colitis rat models, and showed a superior treatment effect in alleviating inflammation of colitis rats. No systemic toxicity was observed after oral administration of blend MS. Therefore, zinc ion cross-linked alginate/N-succinyl-chitosan blend MS appeared to be a good candidate for co-delivery of zinc and 5-ASA to colon, and had great potential application in inflammatory bowel diseases (IBD) treatment.

Formulation and In Vitro Evaluation of Mupirocin-loaded Alginate Microspheres

Introduction: Mupirocin (pseudomonic acid A) is a topical antibiotic used for the treatment of impetigo a superficial infection of the skin. Aim: The goal of this study was to evaluate the technological feasibility of delivering antibiotic using alginate microspheres. Materials and Methods: Microspheres were prepared by emulsification method using sodium alginate as a polymer and calcium chloride (CaCl2) as a cross-linking agent. In this investigation, a novel method was used to investigate the joint influence concentration of alginate and CaCl2 in a blend of liquid paraffin in the dispersion medium. Potential variables such as the concentration of drug and sodium alginate: Drug ratios were kept constant in the experimental design. Different concentrations of the cross-linking agent and different time periods of the cross-linking process were used to change the extent of cross-linking. The cross-linked microspheres were characterized by evaluating the extent of cross-linking, the morphology, and drug loading and in vitro studies of drug release. Results and Discussion: The particle size of the drug loaded microspheres was 75 μm, and they have narrow size distribution. Total drug loading was determined to be 15.10 ± 0.01. Preparation process gave a yield production of nearly 80% for the prepared batches. The microspheres released 71.3% of mupirocin at 72 h. Conclusion: The study revealed that for obtaining controlled delivery of mupirocin; the microspheres should be prepared using relatively an optimum concentration of sodium alginate and CaCl2 and in the dispersion medium.

Synthesis of highly carboxylated monodisperse polystyrene microspheres by dispersion polymerization in fluorinated alcohol

Fluorinated alcohol is demonstrated as a suitable medium for the preparation of monodisperse carboxylfunctionalized microspheres by dispersion polymerization. In the presence of polyvinylpyrrolidone as stabilizer, coagulum-free monodisperse micrometer-sized copolymers containing up to 30 wt% acrylic acid could be produced via one-stage batch dispersion polymerization with 2,2,2-trifluoroethanol as the medium. The coefficient of variation for the particle size distribution decreased as the acrylic acid content in the monomers increased and stabilized at approximately 3% when the acrylic acid content was 15 wt% or higher. The resulting microspheres exhibited pHsensitive behavior. Dissolution of the copolymer chains in alkaline solution could be reduced by incorporating a cross-linkable comonomer. The monodispersity and colloidal stability of the carboxyl-functionalized microspheres were preserved until the amount of divinylbenzene reached 2 wt% based on the monomer. It was found that two-stage semi-continuous dispersion polymerization was an effective method for the synthesis of cross-linked carboxyl-functionalized microspheres.

Biobased Microspheres Consisting of Poly(trans-anethole-co-maleic anhydride) Prepared by Precipitation Polymerization and Adsorption Performance

This paper reports the first biobased microspheres derived from phenylpropenic resources. To explore the potentials of biomass derived trans-anethole (ANE) and to develop new biobased polymeric materials, ANE was used for preparing an unprecedented kind of polymeric microspheres constructed by poly(trans-ANE-co-maleic anhydride) [poly(ANE-co-MAH)] through free radical precipitation polymerization in methyl ethyl ketone/n-heptane mixed solvent with 2,2′-azobis(isobutyronitrile) as the initiator. Microspheres (about 1 μm in size) with spherical morphology and narrow size distribution were obtained under appropriate conditions. Following the same preparative strategy, cross-linked microspheres were further prepared with divinylbenzene as a cross-linking agent and then subjected to hydrolyzation of the surface anhydride groups into carboxyl groups, aiming at developing microsphere adsorbents. The hydrolyzed microspheres exhibited considerable adsorption ability toward trivalent chromic ion [Cr(III)] and an or...

Fabrication of a thermo-responsive membrane with cross-linked smart gates via a ‘grafting-to’ method

A novel thermo-responsive membrane with the cross-linked microspheres as smart gates is fabricated by the “grafting to” technique, which exhibits excellent thermo-responsive characteristics with satisfactory reversibility and stability.

Chitosan-Glycine Cross-Linked Microspheres for Controlled Release of Isoniazid

Semi-interpenetrating polymer network microspheres of chitosan with glycine have been prepared for encapsulation and controlled release of isoniazid (INH) as a model drug. The method involved the exposure of microspheres to the vapor of cross-linking agent to effect the cross-linking under mild conditions. The swelling behavior, hydrolytic degradation and loading capacity of microspheres for INH have been investigated. The prepared microspheres have shown 96% drug loading capacity, which suggested that these semi-interpenetrating polymer network microspheres are suitable to controlled release of drugs in an oral sustained delivery system. Cite this Article K. C. Gupta, M. N. V. Ravikumar, Fawzi Habeeb Jabrail. Chitosan-Glycine Cross-Linked microspheres for controlled release of isoniazid. Journal of Modern Chemistry & Chemical Technology. 2015; 6(3): 7–12p.

Synthesis of Thiourea-Formaldehyde Resin for Cr<sup>3+</sup> Removal

The thiourea (T) -formaldehyde (F) resins with different lamellar crystal structures were synthesized by varying the relative T/F molar ratio in acidic aqueous solution at 55°C. By maintaining the amount of formaldehyde more than that of thiourea, the polymerization reaction allows one to transform the lamellar crystal fragments into cross-linked microspheres, TF resin that has a somewhat high absorption capability to Cr3+.

Investigation on the Stability of the Dispersion System of Cross-Linked Polyacrylamide Microspheres

The salt resistance, temperature resistance, and shear stability of a cross-linked polyacrylamide microsphere system are studied by microfiltration, light diffraction analysis, and optical microscopy. The results show that other conditions being equal, the particle diameter of cross-linked polyacrylamide microspheres decreases with increased NaCl concentration. When NaCl concentration is lower than 10,000 mg/L, its effect on the plugging performance of a cross-linked polyacrylamide microsphere system in regard to the nuclear pore membrane is weak in comparison with a linked polymer solution, but the former system has better salt tolerance. Particle diameter decreases with increased swelling temperature. When the swelling temperature is below 90°C, its effect on the plugging performance of the cross-linked polyacrylamide microsphere system in regard to nuclear pore membrane is weak in comparison with the linked polymer solution, but has better temperature tolerance. Particle size shows little change, with shearing rate being increased, while the shape remains about the same and the effect of shearing on the plugging performance of the cross-linked polyacrylamide microsphere dispersion system in regard to the nuclear pore membrane is weak in comparison with the linked polymer solution, but has better shear stability. The salt tolerance, temperature tolerance, and shear stability of microspheres are associated with a particular cross-linked structure.

Adsorption of Cd(II), Cu(II) and Ni(II) ions by cross-linking chitosan/rectorite nano-hybrid composite microspheres

Chitosan/rectorie (CTS/REC) nano-hybrid composite microsphere was prepared by changing the proportion of CTS/REC with 2:1, 3:1 and 4:1. Compared with the pure cross-linking chitosan microsphere, the nano-hybrid composite microsphere was proved to have better sorption capacity of Cd(II), Cu(II) and Ni(II), especially 2:1(CTS/REC-1). The adsorption behavior of the microsphere of Cd(II), Cu(II) and Ni(II) was investigated in single and binary metal systems. In single system, the equilibrium studies showed that the adsorption of Cd(II), Cu(II) and Ni(II) followed the Langmuir model and the pseudo-second-order kinetic model. The negative values of (ΔG) suggested that the adsorption process was spontaneous. In binary system, the combined action of the metals was found to be antagonistic and the metal sorption followed the order of Cu(II)>Cd(II)>Ni(II). The regeneration studies indicated that EDTA desorbed Cd(II), Cu(II) and Ni(II) from cross-linking microspheres better than HCl. The FT-IR and XPS spectra showed that coordination bonds were formed between Cd(II), Cu(II) and Ni(II) and the nitrogen atoms of cross-linking CTS/REC nano-hybrid composite microspheres.

Effects of preparation methods on the bone formation potential of apatite-coated chitosan microspheres

To investigate the effects of preparation methods on the bone formation potential of apatite-coated chitosan microspheres, coacervate precipitation method and emulsion cross-linking method were chosen to prepare chitosan microspheres, and then apatite coatings were deposited using simulated body fluid. Rat bone marrow-derived mesenchymal stem cells (BMSCs) were seeded on these microspheres. Cell adhesion, proliferation, and differentiation potential were monitored. For in vivo analysis, some cell/microsphere constructs were implanted in the subcutaneous pockets of male Wistar rats. After 3, 6, 12 weeks, the samples were retrieved and stained with hematoxylin and eosin (HE). Some cell/microsphere constructs were implanted in the calvarial defects of rats. Micro-CT and HE analysis were performed to analyze the new bone formation. It was found that BMSCs on apatite-coated emulsion cross-linked microspheres (EM1) exhibited better proliferation and differentiation than cells on apatite-coated coacervate-precipitated microspheres. The in vivo results showed that no bone was observed in ectopic areas. While in calvarial defects, both histological slices and Micro-CT images demonstrated that a substantial amount of new bone was formed in the EM1/BMSCs construct. These data suggest that preparation methods do exert great influence on the in vitro cell behaviors and in vivo orthotopic bone regeneration of apatite-coated chitosan microspheres. Appropriate method should be considered when preparing chitosan microspheres for bone tissue engineering scaffold.