pH-sensitive behavior of two-component hydrogels composed of N,O-carboxymethyl chitosan and alginate

Article · February 2005with22 Reads
DOI: 10.1163/156856205774472317 · Source: PubMed
Abstract
A two-component pH-sensitive hydrogel system composed of a water-soluble chitosan derivative (N,O-carboxymethyl chitosan, NOCC) and alginate cross-linked by genipin, glutaraldehyde or Ca2+ was investigated. Preparation and structures of these hydrogels and their swelling characteristics and release profiles of a model protein drug (bovine serum albumin, BSA) in simulated gastrointestinal media are reported. At pH 1.2, the swelling ratios of the hydrogels cross-linked by distinct methods were limited. Of note is that the lowest swelling ratios of test hydrogels were found at pH 4.0. At pH 7.4, the carboxylic acid groups on test hydrogels became progressively ionized and led to a significant swelling. There was barely any BSA released from the glutaraldehyde-cross-linked hydrogel throughout the entire course of the study. The amounts of BSA released at pH 1.2 from the genipin- and Ca(2+)-cross-linked hydrogels were relatively low (approx. 20%). At pH 4.0, there was still significant BSA release from the Ca(2+)-cross-linked hydrogel, while the cumulative BSA released from the genipin-cross-linked hydrogel was limited due to its shrinking behavior. At pH 7.4, the amount of BSA released from the genipin- and Ca(2+)-cross-linked hydrogels increased significantly (approx. 80%) because the swelling of both test hydrogels increased considerably. The aforementioned results indicated that the swelling behaviors and drug-release profiles of these test hydrogels are significantly different due to their distinct cross-linking structures.
    • Co. (Kaohsiung, Taiwan) to develop a special hydrogel for Derinat (D hydrogel). Derinat hydrogel helps skin tissue absorb this drug by tuning the surface charge distribution on the pores of the skin surface [39,40]. The Derinat-containing hydrogel formed a 3-cm diameter circular chip.
    [Show abstract] [Hide abstract] ABSTRACT: Ultraviolet-B (UVB) is one of the most cytotoxic and mutagenic stresses that contribute to skin damage and aging through increasing intracellular Ca(2+) and reactive oxygen species (ROS). Derinat (sodium deoxyribonucleate) has been utilized as an immunomodulator for the treatment of ROS-associated diseases in clinics. However, the molecular mechanism by which Derinat protects skin cells from UVB-induced damage is poorly understood. Here, we show that Derinat significantly attenuated UVB-induced intracellular ROS production and decreased DNA damage in primary skin cells. Furthermore, Derinat reduced intracellular ROS, cyclooxygenase-2 (COX-2) expression and DNA damage in the skin of the BALB/c-nu mice exposed to UVB for seven days in vivo. Importantly, Derinat blocked the transient receptor potential canonical (TRPC) channels (TRPCs), as demonstrated by calcium imaging. Together, our results indicate that Derinat acts as a TRPCs blocker to reduce intracellular ROS production and DNA damage upon UVB irradiation. This mechanism provides a potential new application of Derinat for the protection against UVB-induced skin damage and aging.
    Full-text · Article · Nov 2015
    • This pH value was higher than that of 5.0∼5.7 reported for the strongest interaction between unmodified chitosan and SAL [10, 13]. The pK a value of the –NH 2 groups in chitosan was about 6.2 [16], but the carboxymethyl modification possibly altered this value, and the pK a of the –NH 2 groups in NOCC was reported to be 8.0 [8]. Hence, it was believed that the –NH 2 groups in O-CMC were still protonated in pH 6.5 and could interact with SAL through electrostatic interaction.
    [Show abstract] [Hide abstract] ABSTRACT: O-carboxymethyl chitosan (O-CMC) is a water-soluble derivative of chitosan. In this work, the formation of polyelectrolyte complex (PEC) between O-CMC and sodium alginate (SAL) was explored by investigating the effects of medium pH, polyelectrolytes mixing ratio, and ionic strength on the yield of O-CMC-SAL PECs. Meanwhile, the rheological, thermal, and microstructural properties of the PECs prepared at various medium acidities were characterized as well. The results indicated that the strongest complexation between O-CMC and SAL occurred in medium pH 6.5 and biopolymer ratio (R O-CMC/SAL) 1.5:1 (w/w) in the absence of added NaCl. Fourier transform infrared (FTIR) spectroscopy analysis revealed that both electrostatic interaction and hydrogen bonding were involved in PEC formation. The PECs possessed the porous structure and displayed predominately the elastic property with the highest moduli values being recorded at medium pH 3.5. It was concluded that the O-CMC-SAL PECs have potential biomedical applications due to the nearly neutral complexation pH and the porous structure for drug inclusion.
    Full-text · Article · Feb 2014
    • The solution was casted onto a Petri dish and dried at room temperature. To prepare SA crosslinked membranes (SA/CaCl 2 ), the dry SA membranes were removed off the Petri dish and immersed in 20 % CaCl 2 solution for 5 minutes [9, 10, 11]. The membranes were washed with methanol to eliminate the remaining CaCl 2 , and dried at room temperature.
    [Show abstract] [Hide abstract] ABSTRACT: Parkinson’s Disease (PD) is the second most common progressive neurodegenerative disorder and is referred as a leading cause of neurologic disability. The symptoms and signs of PD result from a decrease of dopamine’s level in the basal ganglia. Accordingly to this, exogenous substitution with dopamine agonists like levodopa, is used to correct the mechanical disorders at the early stages of the disease. Levodopa is referred as a standard in the treatment of PD. The modern studies of PD drug development and experimental therapeutics focuses on the concept of slowing and targeting the release of levodopa to prolong the therapeutic effect and reduce the number of administrations. The transdermal route was thought to be the best route for providing a progressive supply of levodopa to the systemic circulation. Alginate was chosen as a drug carrier because of its biocompatible and biodegradable properties and also because it has been widely used in drug delivery systems (DDS). The aim of this research work was to produce alginate membranes with and without levodopa. A solvent casting based methodology was used. Calcium chloride was assayed as crosslinking agent. Membranes were characterized using Differential Scanning Calorimetry (DSC) techniques. Drug release was evaluated using UV Spectrophotometry.
    Article · Aug 2013
    • After curing in calcium chloride solutions, NOCC was physically crosslinked with calcium ions therefore became water-insoluble. After cross-linking, molecular chain mobility of MC in the homogeneously blend composites (CaN 2 M 0.5 and CaN 2 M 2 ) was limited due to the formation of semiinterpenetrated networks (Chen et al., 2004; Mi et al., 2005). In contrast, in the phase-separated composite film, MC was readily dissolved from the film even NOCC had been crosslinked with calcium ions.
    [Show abstract] [Hide abstract] ABSTRACT: In this study, antimicrobial and antioxidant active packaging films were prepared from water-soluble chitosan (N,O-carboxymethyl chitosan, NOCC) and cellulose (methylcellulose, MC). Composite films were prepared by directly blending NOCC and MC in water, followed by cross-linking the NOCC/MC composite films with calcium ions. The microstructure, water vapor permeability and mechanical strength of the composite films could be modulated via adjusting the NOCC/MC blending ratio and subsequently cross-linking the films with calcium ions. To prepare active packaging films, a natural phenolic antioxidant, caffeic acid, was incorporated into the composite films in fixed and releasable types. The caffeic acid-incorporated films showed 20-fold increases in antioxidant activity and 6-fold increases in antibacterial activity as compared to the caffeic acid-free composite films. The releasable caffeic acid could be continuously released from the composite films and showed significant inhibitory effect on lipid oxidation of menhaden oil-in-water emulsion. The caffeic acid-based active packaging may be a potential alternative approach to reduced lipid oxidation in fish oil.
    Full-text · Article · Jul 2013
    • The swelling ratio of test beads with a 2% CaCl 2 concentration was lower than the group with a 1% CaCl 2 concentration at pH 1.5 (p50.05). At pH 7.4, after decreasing the 2% CaCl 2 concentration to 1%, the crosslinks between Ca 2+ and carboxylate ions became slower, a larger swelling force created by the electrostatic repulsion between the ionized carboxyl groups leads to higher swelling ratio [7,24,25]. Two groups of 2% and 3% CaCl 2 showed no statistical difference (p>0.05), indicating the carboxyl groups of N-succinyl-chitosan and alginate are limited, when the CaCl 2 concentration increased to a certain extent, the ionic crosslinking of Suc-Chi/alginate with Ca 2+ was complete, the swelling of hydrogel beads was not obviously.
    [Show abstract] [Hide abstract] ABSTRACT: A novel N-succinyl chitosan(Suc-Chi)/alginate hydrogel bead was prepared by the ionic gelation method for the controlled delivery of nifedipine. The structure and surface morphology of the hydrogel were characterized by FTIR and SEM, respectively. Factors influencing the swelling ability of the hydrogel bead were also investigated, such as the ratio of Suc-Chi and alginate (X(1)), the weight ratio of drug to polymer (X(2)), the volume ratio of alginate/Suc-Chi to CaCl(2) (X(3)), crosslinking time (X(4)), CaCl(2) concentration (X(5)). In addition, the delivery behavior of nifedipine from the hydrogel bead was studied. The amount of nifedipine released from the hydrogel bead at pH 1.5 was relatively low (11.6%), while this value approached 76% at pH 7.4. The results clearly suggested that the Suc-Chi/alginate hydrogel bead may be a potential polymeric carrier for drug delivery in the intestinal tract. The release of nifedipine from the hydrogel bead at various pH values was analysed by a semi-empirical equation and it was found that the drug release mechanisms were either 'anomalous transport' or 'case-II transport'.
    Full-text · Article · Apr 2008
    • Similarly, semi-interpenetrating networks of cross-linked copolymer acrylamide/acrylic acid polyallylamine can serve as effective pH-stimulated drug delivery system [33]. Two-component crosslinked chitosan derivatives show swelling at pH 7.4 and above due to ionization of the carboxylic acid groups in the gel [34]. A strong temperature dependence of pH triggered hydrogels composed of poly(2-ethyl-2-oxazoline) and chitosan was reported [35].
    [Show abstract] [Hide abstract] ABSTRACT: Changes in the chemical environment can trigger large motions in chemomechanical polymers. The unique feature of such intelligent materials, mostly in the form of hydrogels, is therefore, that they serve as sensors and actuators at the same time, and do not require any measuring devices, transducers or power supplies. Until recently the most often used of these materials responded to changes in pH. Chemists are now increasingly using supramolecular recognition sites in materials, which are covalently bound to the polymer backbone. This allows one to use a nearly unlimited variety of guest (or effector) compounds in the environment for a selective response by automatically triggered size changes. This is illustrated with non-covalent interactions of effectors comprising of metal ions, isomeric organic compounds, including enantiomers, nucleotides, aminoacids, and peptides. Two different effector molecules can induce motions as functions of their concentration, thus representing a logical AND gate. This concept is particularly fruitful with effector compounds such as peptides, which only trigger size changes if, e.g. copper ions are present in the surroundings. Another principle relies on the fast formation of covalent bonds between an effector and the chemomechanical polymer. The most promising application is the selective interaction of covalently fixed boronic acid residues with glucose, which renders itself not only for sensing, but eventually also for delivery of drugs such as insulin. The speed of the responses can significantly increase by increasing the surface to volume ratio of the polymer particles. Of particular interest is the sensitivity increase which can be reached by downsizing the particle volume.
    Full-text · Article · Feb 2007
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