Facile preparation of monodisperse hollow cross-linked chitosan microspheres (original) (raw)
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Uniform chitosan hollow microspheres prepared with the sulfonated polystyrene particles templates
Colloid and Polymer Science, 2008
Biodegradable chitosan hollow microspheres have been fabricated by employing uniform sulfonated polystyrene (PS) particles as templates. The chitosan was adsorbed onto the surface of the sulfonated polystyrene templates through the electrostatic interaction between the sulfonic acid groups on the templates and the amino groups on the chitosan. Subsequently, the adsorbed chitosan was crosslinked by adding glutaraldehyde. After the removal of the sulfonated polystyrene core, chitosan hollow microspheres were obtained. The longer the sulfonation time used, the smaller the size of the hollow particles and the thicker the chitosan wall obtained. Fourier transform infrared spectrometry was used to characterize the component of the microspheres. The morphologies of the PS templates and the chitosan microspheres were observed by transmission electron microscopy and scanning electron microscopy. The controlled release behavior of the chitosan hollow microspheres was also primarily investigated.
Synthesis and characterization of cross-linked chitosan microspheres for drug delivery applications
Journal of Microencapsulation, 2003
Novel sodium alginate/polyvinyl alcohol/graphene oxide (SA/PVA/GO) nanocomposite ultrafiltration membranes were successfully synthesized via the phase inversion process. Their application in ultrafiltration requires crosslinking. The resulting hydrophilic membranes were in situ crosslinked using glutaraldehyde as a covalent crosslinker and calcium chloride as an ionic crosslinker. The synthesized membranes were characterized using differential scanning calorimetry, X-ray diffraction, water contact angle, scanning electron microscopy and Fourier-transform infrared spectroscopy. Performance tests showed that the sodium alginate membranes have a high affinity for bovine serum albumin and can remove 87% at an optimum transmembrane pressure of 2 bar. The presence of GO improved the cobalt and copper rejection, reaching around 23% (Co) and 34% (Cu) at 2 bar. The prepared membrane showed a higher affinity for Cu 2+ than for Co 2+ due to the size effect. The permeability of the membranes was improved by increasing the PVA concentration up to 3 wt.%. The use of graphene oxide increased the hydrophilic property of the membrane, which yielded a significantly higher flux than the unmodified membrane. The as-prepared membrane with 3 wt.% SA, 9 wt.% PVA, and 0.3 wt.% GO percentages was chosen as the best membrane and was found to have the optimal performance.
A proposed new method for the crosslinking of chitosan microspheres
Drug Delivery, 1998
This work concerns microparticulate drug delivery systems based on the natural polymer, chitosan. A new method for the chemical crosslinking of spray-dried chitosan microspheres containing cetylpyridinium chloride (CPC), as a model of an amphiphilic drug, is here proposed and evaluated. The method consists of the exposure of spray-dried microspheres to the vapor of crosslinking agents that act in gaseous phase and under mild conditions. The novelty and the major advantage of the proposed method is that it does not involve liquid phases coming in contact with the microspheres and in which the drug could dissolve. Three different chemical crosslinking agents, glutaraldehyde, epichlorohydrin, and glyceraldehyde, have been used to evaluate the feasibility of the method. The microparticulate drug delivery systems prepared could find useful pharmaceutical applications as disinfectants and healing powders. The results obtained show that the crosslinking process is effective in promoting modulation of drug release rate from the microspheres. Glyceraldehyde appears to be a good crosslinking agent with the advantage of being nontoxic.
A one-step method for fabricating chitosan microspheres
Journal of Applied Polymer Science, 2004
A simple and in situ method, by using a high-voltage electrostatic system, for the fabrication of chitosan microspheres (in a form of isolatable microgels) by an extrusion process, exhibiting variable sizes and different membrane structures, was presented. The chitosan microspheres exhibited good sphericity and were in the range of 185.8 Ϯ 13.8 to 380.9 Ϯ 11.5 m in diameter. There were two significant factors, the pump flow rate and electrostatic field strength, that affected the chitosan microsphere size. The microsphere size decreased when the flow rate was increased from 0.1 to 0.4 mL/h. Also, the microsphere size decreased when the electrostatic field strength was increased from 5.5 to 6.5 kV/cm. However, when the electrostatic field strength was raised to 7 kV/cm and higher, the microsphere size increased. For the latter case, with other parameters fixed, chitosan microsphere size can be controlled by adjusting the electrostatic field strength and predetermined by a simple linear regression equation: Microsphere Diameter (D, in m) ϭ Ϫ(75.48) ϩ 45.67 ϫ (Electrostatic Field Strength, E, in kV/cm), at [7 Յ (Electrostatic Field Strength) Յ 10] (R 2 ϭ 0.956, P Ͻ 0.001). Following treatment with various ratios of crosslinking/gelating (Na 5 P 3 O 10 /NaOH) agents, the prepared chitosan microspheres exhibited distinct membrane structures that yielded various mechanical strengths. In the Na 5 P 3 O 10 /NaOH ratio of 19, the chitosan microspheres had a distinct two-layer structure. The selection of crosslinking/gelating ratio provided an additional degree of freedom, permitting the simultaneous regulation of mechanical properties and permeability of the microspheres, without extra manipulation, and thus, improved applicability in the biomedical field. When the chitosan microsphere extrusion process was used to encapsulate -tricalcium phosphate powder for application as bony material, we found that the ultra fine -tricalcium phosphate powder was trapped inside of the membrane very well. After appropriate collecting procedures, stored microspheres also retained good spherical shape.
International Journal of Molecular Sciences
Chitosan (CH)–carboxymethyl cellulose sodium salt (NaCMC) microcapsules containing paraffin oil were synthesized by complex formation, and crosslinked with glutaraldehyde (GTA). The electrostatic deposition of NaCMC onto the CH-coated paraffin oil emulsion droplets was demonstrated by zeta potential and optical microscopy. The optimal process conditions were identified in terms of pH of the aqueous solution (5.5) and CH/NaCMC mass ratio (1:1). Encapsulation of paraffin oil and microcapsule morphology were analyzed by ATR-FTIR and SEM, respectively. The effect of GTA crosslinking on paraffin oil latent heat was investigated by DSC and combined with the values of encapsulation efficiency and core content, supporting the compact shell formation.
Hollow Chitosan/Alginate Nanocapsules for Bioactive Compound delivery
International journal of biological macromolecules, 2015
This work aimed at the development of biodegradable nanocapsules as carriers of two bioactive compounds, 5-aminosalycilic acid and glycomacropeptide. Nanocapsules were produced through Layer-by-Layer (LbL) deposition of chitosan (CH) and alginate (ALG) layers on polystyrene nanoparticles. The bioactive compounds were incorporated on the third layer of the nanocapsules being its encapsulation efficiency and release behaviour evaluated. The LbL deposition process, stability, morphology and size of the multilayer nanocapsules were monitored by means of zeta potential and transmission electron microscopy (TEM). The bioactive compounds release from the CH/ALG nanocapsules was successfully described by a mathematical model (Linear Superimposition Model-LSM), which allowed concluding that bioactive compounds release is due to both brownian motion and the polymer relaxation of the CH/ALG layers. Final results demonstrated that the synthesized LbL hollow nanocapsules presented spherical morp...
Review on micro-encapsulation with Chitosan for pharmaceuticals applications (2).pdf
There is evidence that several systematic researches recognized the importance of using polymers in drugs manufacturing. Natural polymers are usually biocompatible, biodegradable and non-expensive like chitosan. Chitosan is one of the natural biodegradable groups of polymers that have been extensively used for microencapsulation of drugs like isoniazid, propranolol and aspirin. This natural polysaccharide has many pharmaceuticals applications, such as oral and parenteral delivery of drugs. It is important for a wide range of scientific and industrial processes to know the applications of chitosan microparticles loaded drugs in pharmaceuticals fields. Recently, this issue was the objective of many research papers in the literature. Chitosan can also be combined with other polymer to encapsulate many drugs in order to achieve targets with performance delivery. Recent advances in microencapsulation methods have facilitated investigation of chitosan usage to load drugs. This review about the preparation of chitosan-based-micro and particles by many fabrications methods of pharmaceutical applications including coacervation, drying techniques, ionic cross-linking, ionotropic gelation and emulsion solvent diffusion method.
xhitosan microspheres having good spherical geometry and a smooth surface were prepared by the glutaraldehyde cross-linking of an aqueous acetic acid dispersion of chitosan in paraffin oil using dioctyl sulphosuccinate as the stabilizing agent. Microspheres having different degrees of swelling were made by varying the cross-linking density. Microspheres were prepared by incorporating theophylline, aspirin or griseofulvin. Drug incorporation efficiencies exceeding 80% could be achieved for these drugs. In-vitro release studies of these drugs were carried out in simulated gastric and intestinal fluids at 37°C. It was observed that the drug release rates were influenced by the cross-linking density, particle size and initial drug loading in the microspheres.
International Journal of Biological Macromolecules, 2019
This work emphazises the importance of the solubilizing conditions for the elaboration of chitosan hydrogel beads, which were produced using electromagnetic laminar jet breakup technology, resulting in dried porous beads by further freeze-drying. Paramaters such as the acid nature and concentration (acetic, formic, citric, lactic, maleic and malic, 0.1 to 0.5 mol.L-1), the chitosan concentration (2 to 5 wt %) and composition of the gelation bath (NaOH, with or without EtOH) were studied. Viscosity versus strain rate measurements were carried out on chitosan acidic solutions and the viscoelastic behaviour was studied on hydrogels. The solutions exhibiting the highest viscosities led to the stiffest macrohydrogels, as a result of chitosan carboxylate interactions. Specific surface areas of the freeze-dried beads were determined in the range from 12 to 107 m².g-1. Their internal texture was observed by Scanning Electron Microscopy. Water uptake was also measured for further use in the field of water purification. 1. Introduction Chitosan (CS) is an aminated linear copolysaccharide of N-acetyl D-glucosamine and Dglucosamine, mainly produced dy deacetylation of chitin. Chitin is itself a by-product of see food industry, composing crustaceans' cuticles and can also be found in insects' cuticles and in fungi cell walls as a non animal source [1,2]. Solid-state heterogeneous N-deacetylation of chitin leads to chitosan of different acetylation degrees (DA), deacetylation pattern (DP) and molecular mass, depending on chitin source and N-deacetylation process [3-5]. Reacetylation of chitosan of low DA can also yield series of polymers of various DAs [6]. During the last decades, the use of CS has been envisioned in many applications, due to its interesting intrinsic physico-chemical and biological