Controlled hydrophobic/hydrophilic chitosan: colloidal phenomena and nanosphere formation (original) (raw)
Related papers
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
Chitosan nanoparticles: Current aspects
GSC biological and pharmaceutical sciences, 2022
Nanoparticles are currently becoming one of the important parts for various segments. Much more process/application becomes effective or more economical and time-saving because of nanoparticles. Polymers with distinct characteristics are widely used but nature-origin polymer has important properties that make a polymeric material for nanoparticles. Many methods were successfully evaluated to prepare chitosan nanoparticles for loading various compounds including ionotropic gelation, micelles, and emulsification methods. In this article, we have reviewed the current aspects madeup of chitosan nanoparticles. Chitosan nanoparticles have an application to improve bioavailability, controlled release of the loaded drug also increases cellular uptake and targeting to cancer cells, stabilization of proteins, and enhanced the effectivity of anti-microbial agents. In agriculture, chitosan nanoparticles are used for herbicides, insecticides, and pesticide loading to improve the cultivation of crops and are used in food packaging. Chitosan nanoparticles also have wide applications as implant and therapeutic agent.
Colloids and Surfaces B: Biointerfaces, 2011
In recent years, chitosan nanocapsules have shown promising results as carriers for oral drug or peptide delivery. The success in their applicability strongly depends on the stability of these colloidal systems passing through the digestive tract. In gastric fluids, clear stability comes from the high surface charge density of the chitosan shell, which is completely charged at acidic pH values. However, in the intestinal fluid (where the pH is almost neutral) the effective charge of these nanocapsules approaches zero, and the electrostatic forces cannot provide any stabilization. Despite the lack of surface charge, chitosan nanocapsules remain stable in simulated intestinal fluids. Recently, we have demonstrated that this anomalous stability (at zero charge) is owed to short-range repulsive forces that appear between hydrophilic particles when immersed in saline media. The present work examines the influence of the chitosan hydrophobicity, as well as molecular weight, in the stability of different chitosan nanocapsules. A study has been made of the size, polydispersity, electrophoretic mobility, and colloidal stability of eight core-shell nanocapsule systems, in which the chitosan-shell properties have been modified using lowmolecular-weight (LMW) and high-molecular-weight (HMW) chitosan chains having different degrees of acetylation (DA). With regard to the stability mediated by repulsive hydration forces, the LMW chitosan provided the best results. In addition, contrary to initial expectations, greater stability (also mediated by hydration forces) was found in the samples formed with chitosan chains of high DA values (i.e. with less hydrophilic chitosan). Finally, a theoretical treatment was also tested to quantify the hydrophilicity of the chitosan shells.
Hystersis of Composites [Working Title]
Since long scientists explored natural/bio-polymers to explicit their innate features to develop certain novel utilities in modernization of prevalent Science & Technology. Consequently biotope derived polysaccharide embrace huge prospective desired functions. Amid, chitosan, the second most ubiquitous polymer after cellulose exists as a β-(1-4)-linked d-glucosamine/N-acetyl-d-glucosamine randomly distributed linear polycationic yield from partial deacetylation of chitin polysaccharide. Chitin's complexity limits its extraction/insolubility in aqueous solution, thus less studied/research until 1980s. As major polysaccharides are either neutral/negatively charged in an acidic environment, instead chitosan is cationic, eventually forms electrostatic complexes/multilayer structures/composites with anionic synthetic dopants/natural polymers. Chitosan own biocompatibility, non-toxicity, low allergy and biodegradability allow utility as in water treatment, wound-healing, pharmaceutical excipient/drug carrier, obesity treatment and scaffold for tissue engineering. It is reflected in the increasing number of related publications throughout in biomedical, environmental and industrials applications. Feeble chitosan solubility limits their applications, yet benign synthetic techniques viz.; sol-gel, encapsulation, chemical grafting are employed to yield composites/ hydrogels/films/granules which generates new functionality, besides enhanced biocompatibility and biodegradability. This chapter presents the R&D, trends and the latest prospects involved in advance synthesis of chitosan supported composites/ hydrogels/films/granules/sheets with special highlighted pharmaceutical/biomedical and environmental applications.
Powder Technology, 2013
Combined precipitation and spherical agglomeration was carried out in the non-miscible region of ethyl acetate-ethanol-water ternary solvent system. At first, w/o type quasi emulsion was prepared by sequential introduction of aqueous solutions of human serum albumin (HSA), chitosan (CS), and poly(4-styrenesulfonate) (PSS) into an ethyl acetate-ethanol solvent mixture. HSA was used to model a protein type drug, while CS and PSS served as matrix material in the obtained composite particles. PSS also served as chemical precipitation agent for both of the HSA and CS. The solubility of all these substances was reduced by introduction of additional amounts of ethyl acetate-ethanol mixture and/or ethanol as poor solvents. Due to the counter-diffusion of the good and poor solvents between the water rich droplets and the ethyl acetate-ethanol rich continuous phase, the aqueous phase gradually disappeared and partial agglomeration of the precipitated solids and their transfer to the continuous organic phase took place. The paper gives a report on the effect of several process variables on the quality of the obtained microparticles, such as their shape and stability against disintegration. The effects of the composition of the ternary solvent mixture, the route of its variation, the feeding method and composition of the added poor solvents, the stirring rate and the duration of agitation were studied.
Preparation and characterization of chitosan-based nanoparticles
Biomacromolecules
The present investigation describes the synthesis and characterization of novel biodegradable nanoparticles based on chitosan for biomedical applications. Natural di- and tricarboxylic acids were used for intramolecular cross-linking of the chitosan linear chains. The condensation reaction of carboxylic groups and pendant amino groups of chitosan was performed by using water-soluble carbodiimide. This method allows the formation of polycations, polyanions, and polyampholyte nanoparticles. The prepared nanosystems were stable in aqueous media at low pH, neutral, and mild alkaline conditions. The structure of products was determined by NMR spectroscopy, and the particle size was identified by laser light scattering (DLS) and transmission electron microscopy (TEM) measurements. It was found that particle size depends on the pH, but at a given pH, it was independent of the ratio of cross-linking and the cross-linking agent. Particle size measured by TEM varied in the range 60-280 nm. In...
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.
Polymer, 2009
Chitosan grafted with hydrophobic and hydrophilic groups initiates the formation of amphiphilic chitosan nanospheres. The molecular weight of mPEG plays an important role to control the particle size. As compared to mPEG 2000, which gives a bimodal nanosphere (w200, and w300 nm), mPEG 5000 initiates a monodispersed nanosphere with the smaller size (150 nm). In aqueous solution, the nanosphere surface is negatively charged resulting in a well dispersion in neutral to high pH but a significant precipitation in low pH. A model drug incorporation using lidocaine is successful when amphiphilic chitosan nanospheres were dissolved in good solvent followed by allowing mixing with drug solution before dialysis. The particle size of the drug incorporated chitosan is significantly increased, that is, from 100-150 nm to approximately 400-500 nm when the amount of incorporated lidocaine was about 0.68 mg per mg of lidocaine-loaded nanosphere.
Chitosan-based nanocapsules of core-shell architecture
Polimery, 2017
N-dodecyl derivative of cationically modified chitosan was used to prepare core-shell nanocapsules templated on liquid cores. Surfactant-free method based on ultrasound-assisted direct emulsification of aqueous solution of polysaccharide with oleic acid was applied. Formation of spherical capsules was confirmed by scanning and transmission electron microscopies. Dynamic light scattering measurements were used to determine physicochemical parameters of the obtained particles as well as to follow the process of multilayer shell formation. Confocal microscopy was applied to examine the ability of encapsulation of hydrophobic compounds inside the cores of the nanocapsules. Performed studies confirmed that hydrophobically modified cationic chitosan provides long-term stabilization of oil-in-water emulsion for biomedical applications as no toxic effect was observed in acute oral toxicity studies.
Facile preparation of monodisperse hollow cross-linked chitosan microspheres
Journal of Polymer Science Part A: Polymer Chemistry, 2008
We have successfully prepared biocompatible and biodegradable hollow microspheres using carboxyl-functionalized polystyrene particles as core template and the chitosan cross-linked with glutaraldehyde as the shell. The monodisperse carboxyl-functionalized polystyrene particles were made by emulsifier-free emulsion polymerization. The structure, morphology, and constitution of the carboxyl-functionalized polystyrene particles were characterized by FTIR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The structure, morphology, and formation process of the hollow crosslinked chitosan microspheres were characterized by FTIR, SEM, and TEM. The results revealed that the latex particles were removed by exposed to solvent and the microspheres exhibited the hollow structure. This work confirmed that the hollow microspheres were accomplished by fabricating on the basis of chemical cross-linking on the surface of the carboxyl-functionalized polystyrene particles and then removing off the cores of particles. Moreover, with the increase of carboxyl-functionalization degree at the surface of latexes and the increase of cross-linking period, the thicker and firmer monodisperse hollow microspheres were obtained. In addition, a watersoluble drug, salicylic acid, encapsulated in the microcapsules slowly released at pH 1.2. V