Comprising Chitosan Research Articles

Determination of Gelation Kinetic Parameters for a Chitosan/β-Glycerophosphate Injectable Hydrogel by Means of Rheological Measurement

The aim of the current study was to improve the knowledge of the gelation process of injectable thermosensitive hydrogels comprising chitosan (CS) and β-glycerophosphate disodium salt (β-GP). The sol-gel transition process was precisely tracked by means of rheological measurement, in which the viscosity changed considerably with gelation time and temperature. The zero-order kinetics model was assumed to adequately describe the extent of gelation reaction. The reaction rate constant increased continuously with the increasing temperature and β-GP concentration. According to Arrhenius equation, the activation energies of gelation reaction for the chitosan injectable hydrogels were calculated as 64.38 KJ/mol, 101.68 KJ/mol and 140.92 KJ/mol for the samples containing 4% w/v, 6% w/v and 8% w/v of β-GP, respectively. It could be an effective way to study the gelation dynamics of injectable hydrogels, and provide references for clinical practice.

Wharton's Jelly Mesenchymal Stem Cell Response on Chitosan-graft-poly (ε-caprolactone) Copolymer for Myocardium Tissue Engineering

Cell therapy and tissue engineering attract increasing attention as a potential approach for cardiac repair. Although a plethora of interesting concepts in the emerging field of cardiac stem cell-based tissue engineering are reported, there are still challenges that this field needs to overcome to achieve therapeutic translation into the clinical praxis. Engineering biomaterial scaffolds that facilitate stem cell engraftment, survival and homing are crucial for successful cellular cardiomyoplasty after myocardial infarction (MI). In this study we investigate for the first time the cellular response of Wharton's jelly (WJ) Mesenchymal Stem Cells (MSCs) on a copolymeric material comprising chitosan (CS) and poly(ε-caprolactone) (PCL). First we synthesize a copolymer consisting of poly(ε-caprolactone) grafted on a chemically modified chitosan-backbone (CS-g-PCL). Furthermore, we investigate the morphology, viability and proliferation of WJMSCs on material coatings and examine the cellular response from different donors. Our results show strong cell adhesion on the CS-g- PCL material surface from the first hours in culture, and a proliferation increase after 3 and 7 days. These findings support the potential use of our proposed cell-material combination in myocardium tissue engineering.

Preparation and characterization of biopolymers comprising chitosan-grafted-ENR via acid-induced reaction of ENR50 with chitosan

This paper describes the first detailed tailored-approach for the preparation of biopolymers comprising chitosan (CTS) grafted onto the backbone of epoxidized natural rubber (CTS-g-ENR). In a typical experiment, appropriate amount of CTS and AlCl3·6H2O was added to a specified amount of ENR50 (ENR with about 50% epoxy content) dissolved in a dual-solvent consisting of 1,4-dioxane and water (97.5:2.5% v/v) and the resulting mixture refluxed with continuous stir- ring for 6 hours. Nuclear magnetic resonance (NMR) spectral analysis of a biocomposite, CTS-g-ENR-P1, revealed that its epoxy content is 22.36% which is considerably lower than 44.93% as determined for ENR50-control (ENR50 derivative obtained under similar experimental condition but in the absence of CTS). This means that the grafting of CTS onto the backbone of ENR had occurred. The revelation is affirmed by the presence of the characteristic absorption bands of CTS and ENR, and the appearance of new bands at 1219, 902 and 733 cm -1 in the Fourier transform infrared (FTIR) spectrum of CTS-g-ENR-P1. Further evidence that CTS had been successfully grafted onto the backbone of ENR can be deduced and described in this paper from the data obtained by means of Differential Scanning Calorimetric analysis, Thermogravimetric analysis and Variable Pressure Scanning Electron Microscopy.

Investigation of gelation mechanism of an injectable hydrogel based on chitosan by rheological measurements for a drug delivery application

The aim of the current study was to improve the knowledge of the gelation mechanism of injectable thermosensitive hydrogels comprising chitosan (CS) and β-glycerophosphate (GP). The CS–GP solution was designed to be liquid at room temperature and gelled at 37 °C. The theory initially worked out by Fredrickson and Larson for block copolymers near their order–disorder transition was extended and proposed to precisely determine the gel point in such systems by considering the aggregation of hydrophobic acetylated blocks of chitosan chains and gelation in CS–GP systems as an order–disorder transition of block copolymers. To investigate the possibility of the application of this system for the sustained delivery of meglumine antimoniate (MGA), the effect of incorporation of MGA and MGA-loaded microspheres (CSMs) was also investigated. It was found that a lower molecular weight of chitosan, drug loading and microparticle incorporation into the CS–GP system enhance the temperature of the G′ and G″ crossover point, attributed to the formation of hydrophobic interactions, while decreasing the gel point determined based on the Fredrickson and Larson theory. Moreover, the in vitro release studies showed that the burst release is reduced from 88% in the first 24 hours for drug loaded CS–GP hydrogel to 66% for CSM-loaded hydrogel.

Natural and synthetic solid polymer hybrid dual network membranes as electrolytes for direct methanol fuel cells

Hybrid dual-network membranes comprising chitosan (CS)–polyvinyl alcohol (PVA) networks crosslinked with sulfosuccinic acid (SSA) and glutaraldehyde (GA) and modified with stabilized silicotungstic acid (SWA) are reported for their application in direct methanol fuel cells (DMFCs). Physico-chemical properties of these membranes are evaluated using thermo-gravimetric analysis and scanning electron microscopy in conjunction with their mechanical properties. Based on water sorption and proton conductivity measurements for the membranes, the optimum content of 10 wt.% SWA in the membrane is established. The methanol crossover for these membranes are studied by measuring the mass balance of methanol using density meter and are found to be lower compared to Nafion-117 membrane. The membrane–electrode assembly with 10 wt.% stabilized SWA–CS–PVA hybrid membrane with SSA and GA as crosslinking agent delivers a peak power density of 156 mW cm−2 at a load current density of 400 mA cm−2 and 88 mW cm−2 at a load current density of 300 mA cm−2, respectively, in DMFC at 70 °C.

Bio-Composite Membrane Electrolytes for Direct Methanol Fuel Cells

A new class of bio-composite polymer electrolyte membranes comprising chitosan (CS) and certain biomolecules in particular, plant hormones such as 3-indole acetic acid (IAA), 4-chlorophenoxy acetic acid (CAA) and 1-naphthalene acetic acid (NAA) are explored to realize proton-conducting bio-composite membranes for application in direct methanol fuel cells (DMFCs). The sorption capability, proton conductivity and ion-exchange capacity of the membranes are characterized in conjunction with their thermal and mechanical behaviour. A novel approach to measure the permeability of the membranes to both water and methanol is also reported, employing NMR imaging and volume localized NMR spectroscopy, using a two compartment permeability cell. A DMFC using CS-IAA composite membrane, operating with 2M aqueous methanol and air at 70°C delivers a peak power density of 25 mW/cm2 at a load current density of 150 mA/cm2. The study opens up the use of bio-compatible membranes in polymer-electrolyte-membrane fuel cells.

Characterization and Dissolution Study of Chitosan Freeze-Dried Systems for Drug Controlled Release

Freeze-dried systems (L) comprising chitosan (CS) and caffeine (CAF) have been developed for oral administration. Different proportions of CS and CAF have been used in the preparation of the systems. Hot stage microscopy (HSM), differential scanning calorimetry (DSC) and X-ray diffraction powder have been used to characterize the systems prepared. X-ray diffraction patterns showed that there were no interactions between CAF and CS molecules within the freeze-dried systems and the crystallinity of CAF was decreased. Swelling and dissolution tests were carried out in two different media (demineralized water and pH progressive medium) in order to establish their influence over CAF/CS system behaviour. Characteristic swelling behaviour of freeze-dried CS systems (imbibition and dissolution processes) was influenced by the proportions of CS and CAF in the formulations, and by the nature of the medium due to the pH-dependent solubility of CS. Release of CAF from lyophilized systems was conditioned by the swelling process and it should be possible to obtain a CAF/CS binary system with a specific time for total drug release including concrete proportions of both components. Furthermore, the freeze-drying process allowed us to obtain feasible systems for controlled release of CAF until the total amount of drug was released.

Formulation Variables Influencing Drug Release from Layered Matrix System Comprising Chitosan and Xanthan Gum

The purpose of this study was to investigate the formulation variables influencing the drug release from the layered tablets containing chitosan and xanthan gum as matrix component. Increasing the amount of lactose could diminish pH sensitive release behavior of these matrix tablets. Effect of formulation variables on drug release from the prepared three-layered matrix tablets was investigated. The amount of drug loading did not affect the drug release which was influenced by the hydrodynamic force and the matrix composition. An increase in stirring rate correspondingly increased the release rate. Moreover, incorporation of soluble diluents in core or barrier could enhance the drug release. Least square fitting the experimental dissolution data to the mathematical expressions (power law, first order, Higuchi's and zero order) was carried out to study the drug release mechanism. Most dissolution profiles of the prepared three-layered tablets provided a better fit to zero order kinetic than to first order kinetic and Higuchi's equation.

Sustained-release from Layered Matrix System Comprising Chitosan and Xanthan Gum

ABSTRACTSustained-release tablets of propranolol HCl were prepared by direct compression using chitosan and xanthan gum as matrix materials. The effective prolongation of drug release in acidic environment was achieved for matrix containing chitosan together with xanthan gum which prolonged the drug release more extensive than that containing single polymer. Increasing lactose into matrix could adjust the drug release characteristic by enhancing the drug released. Component containing chitosan and xanthan gum at ratio 1:1 and lactose 75% w/w was selected for preparing the layered matrix by tabletting. Increasing the amount of matrix in barrier or in middle layer resulted in prolongation of drug release. From the investigation of drug release from one planar surface, the lag time for drug release through barrier layer was apparently longer as the amount of barrier was enhanced. Least square fitting the experimental dissolution data to the mathematical expressions (power law, first order, Higuchi's and zero order) was performed to study the drug release mechanism. Layering with polymeric matrix could prolong the drug release and could shift the release pattern approach to zero order. The drug release from chitosan-xanthan gum three-layer tablet was pH dependent due to the difference in charge density in different environmental pH. FT-IR and DSC studies exhibited the charge interaction between of NH3+ of chitosan molecule and COO− of acetate or pyruvate groups of xanthan gum molecule. The SEM images revealed the formation of the loose membranous but porous film that was due to the gel layer formed by the polymer relaxation upon absorption of dissolution medium. The decreased rate of polymer dissolution resulting from the decreased rate of solvent penetration was accompanied by a decrease in drug diffusion due to ionic interaction between chitosan and xanthan gum. This was suggested that the utilization of chitosan and xanthan gum could give rise to layered matrix tablet exhibiting sustained drug release.