Chitosan Poly Research Articles

Selected properties of pH‐sensitive, biodegradable chitosan–poly(vinyl alcohol) hydrogel

AbstractChitosan and poly(vinyl alcohol) (PVA) were used to form a semi‐interpenetrating polymeric network with glutaraldehyde as the cross‐linker. The molecular weight and degree of deacetylation of the chitosan were 612 kDa and 72 %, respectively. The chemical bonds formed by the cross‐linking reaction and transition of these bonds in different pH media were investigated. The gelation property of the chitosan–PVA pregel solution and mechanical properties of the hydrogel were studied. The FTIR spectra of the hydrogel before and after swelling at pH 3 and pH 7 indicated formation of Schiff's base (CN) and NH3+. They also showed pH‐induced transition of CN to CN, and NH3+ to NH2, as well as the instability of the Schiff's base. The chitosan is essential for hydrogel formation through Schiff's base reaction between the amino groups of the chitosan and the aldehyde groups of the glutaraldehyde. The addition of PVA improved the mechanical properties of the hydrogel. However, PVA tends to leach out at longer swelling times in the acidic medium due to hydrolysis of the gel networks, Schiff's base. Copyright © 2004 Society of Chemical Industry

Water state characterization, swelling behavior, thermal and mechanical properties of chitosan based networks

Two kinds of chitosan-based hydrogels, a crosslinked chitosan reference gel and a chitosan–poly(ethylene oxide) semi-interpenetrating network (semi-IPN), with potential pH-sensitive swelling and drug delivery properties are characterized. Swelling studies were performed on the two kinds of hydrogels by differential scanning calorimetry (DSC) at pH 1.2 and by the gravimetric method at pH 1.2 and pH 7.2. Both methods lead to similar results. If pH-dependent swelling properties were observed with both hydrogels, they were however improved for the semi-IPN. The amount of bound water in the xerogels could be determined from DSC measurements and a thermogravimetric analysis. The results obtained by both techniques were in good agreement and indicated that the semi-IPN contained more bound water than the reference gel probably due to the presence of the hydrophilic poly(ethylene oxide) chains. Young modulus of the swollen hydrogels was determined by indentation analysis. The semi-IPN displayed improved mechanical properties compared to the reference gel.

Synthesis and characterization of chitosan–poly(acrylic acid) nanoparticles

Chitosan (CS)–poly(acrylic acid) (PAA) complex nanoparticles, which are well dispersed and stable in aqueous solution, have been prepared by template polymerization of acrylic acid (AA) in chitosan solution. The physicochemical properties of nanoparticles were investigated by using size exclusion chromatography, FT-IR, dynamic light scattering, transmission electron microscope and zeta potential. It was found that the molecular weight of PAA in nanoparticles increased with the increase of molecular weight of CS, indicating that the polymerization of acrylic acid in the chitosan solution was a template polymerization. It was also found that the prepared nanoparticles carried a positive charge and showed the size in the range from 50 to 400 nm. The surface structure and zeta potential of nanoparticles can be controlled by different preparation processes. The experiment of in vitro silk peptide (SP) release showed that these nanoparticles provided a continuous release of the entrapped SP for 10 days, and the release behavior was influenced by the pH value of the medium.

Enhanced bone formation by controlled growth factor delivery from chitosan-based biomaterials

For the purpose of obtaining high bone forming efficacy, development of chitosan was attempted as a tool useful as a scaffolding device. Porous chitosan matrices, chitosan–poly(l-lactide) (PLLA) composite matrices and chitosan coated on PLLA matrices were dealt with in this research. Porous chitosan matrix was fabricated by freeze-drying and cross-linking aqueous chitosan solution. Porous chitosan matrix combined with ceramics and constituents of extracellular matrices were prepared and examined for their bone regenerative potential. Composite porous matrix of chitosan–PLLA was prepared by mixing polylactide with chitosan and freeze-drying. All chitosan based devices demonstrated improved bone forming capacity by increasing mechanical stability and biocompatibility. Release of platelet-derived growth factor-BB (PDGF-BB) from these matrices exerted significant osteoinductive effect in addition to the high osteoconducting capacity of the porous chitosan matrices. The hydrophobic surface of PLLA matrices was modified by chitosan to enhance cell affinity and wettability. The chitosan coated PLLA matrix induced increased osteoblast attachment as compared with intact PLLA surface. Overall results in this study demonstrated the usefulness of chitosan as drug releasing scaffolds and as modification tools for currently used biomaterials to enhance tissue regeneration efficacy. These results may expand the feasibility of combinative strategy of controlled local drug delivery concept and tissue engineered bone formation in reconstructive therapy in the field of periodontics, orthopedics and plastic surgery.

Studies on semi‐interpenetrating polymer network beads of chitosan–poly(ethylene glycol) for the controlled release of drugs

Semi-interpenetrating polymer network beads of chitosan and poly(ethylene glycol) were prepared and characterized for controlled release of drugs. A viscous solution of chitosan and poly(ethylene glycol) in 2% acetic acid was extruded as droplets with the help of a syringe and crosslinked using glutaraldehyde. The structural studies of the beads were performed by using a Fourier transform infrared spectrophotometer and scanning electron microscope. The swelling behavior, solubility, hydrolytic degradation, and loading capacity of the beads for isoniazid were investigated. The structural changes of the beads at pH 2.0 and 7.4 were put forward using the data obtained by infrared and ultraviolet spectroscopy. The prepared beads showed 82% drug-loading capacity, which suggested that these semi-interpenetrating polymer network beads are suitable for controlled release of drugs in an oral sustained delivery system. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 639–649, 2001

UV-cured natural polymer-based membrane for biosensor application

Chitosan, a natural product, is inherently biodegradable, biocompatible, and nontoxic. These properties make chitosan ideal for inclusion in matrices designed for use in enzyme immobilization for clinical analysis. This study demonstrates the feasibility of using chitosan in electrochemical biosensor fabrication. The enzyme sulfite oxidase (SOX) was covalently immobilized onto the matrix of chitosan–poly(hydroxyethyl methacrylate) (chitosan–pHEMA), a natural/synthetic polymer hybrid obtainable via UV curing. p-Benzoquinone, which served as an electron transfer mediator, was coupled onto the polymer network for activation of the chitosan–pHEMA copolymer, after completion of the photo-induced polymerization reaction. The biological activity of the immobilized SOX and the electroactivity of the coupled p-benzoquinone were investigated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 466–472, 2001

The interactions of chitosan–poly(ethylene glycol) in the presence of added salt in water: viscosity effect

The chitosan (CS) dissolved in an acid solution displays a polyelectrolyte behavior. It was found that the viscosity behavior of CS solutions could be described by the theoretical viscosity expression, proposed by Hess and Klein. Phenomenologically, on the basis of this viscosity theory and Huggins viscosity equation for non-ionic polymer solutions, a new viscosity theoretical expression was developed to describe the viscosity behavior of binary system CS–poly(ethylene glycol) (PEG) in the presence of added salt. It was found that the observed viscosity data were in good agreement with the new viscosity expression. Meanwhile the parameter λ of the new equation was proposed to characterize the interactions between CS and PEG chains in CS–PEG aqueous solutions. From the change of the calculated values of λ with the added salt and PEG concentration, the interaction between CS and PEG and the structure of the formed CS–PEG complex were discussed.

Synthesis and in vitro evaluation of chitosan-EDTA-protease-inhibitor conjugates which might be useful in oral delivery of peptides and proteins.

To develop a novel mucoadhesive polymer that protects peptide drugs from degradation by secreted as well as membrane-bound proteases in the intestine, and to evaluate this polymer in vitro. The serine protease inhibitors antipain, chymostatin and elastatinal were covalently linked to chitosan (poly-[1-->4]-beta-D-glucosamine). Thereafter, the complexing agent ethylenediaminetetraacetic acid (EDTA) was bound to the remaining primary amino groups of the polymer. The inhibitory effect of the resulting polymer-conjugate towards trypsin (EC 3.4.21.4), chymotrypsin (EC 3.4.21.1), elastase (3.4.21.36), carboxypeptidase A (EC 3.4.17.1), carboxypeptidase B (EC 3.4.17.2) and aminopeptidase N (EC 3.4.11.2) as well as its mucoadhesive properties were evaluated in vitro. Whereas the novel polymer-conjugate exhibited excellent swelling properties, its adhesive force was under our assay conditions 42% lower than that of unmodified chitosan. However, the polymer-conjugate showed a strong inhibitory activity towards all tested serine proteases. Due to its additional high binding affinity towards bivalent metal ions, it also inhibited the Zn(2+)-dependent exopeptidases carboxypeptidase A, B and aminopeptidase N. The novel mucoadhesive polymer-conjugate described in this study seems to be a useful tool in overcoming the enzymatic barrier to perorally administered therapeutic peptides and proteins.

Studies on modified chitosan membranes. II. Dialysis of low molecular weight metabolites

AbstractThe permeabilities of low molecular weight metabolites were determined through chitosan and a series of chitosan—poly(vinyl pyrrolidone) (PVP) membranes. The dialysis studies were carried out in vitro using a diaphragm‐type test cell. The basic metabolites (urea, creatinine, and glucose) show higher permeation rates than do the acidic metabolites (uric acid and phosphate) through all the modified membranes. The hydrophilicity of the membranes, molecular weight, and chemical nature of the metabolites were important parameters in determining transport properties of the membranes. It was observed that higher permeation rates can be obtained by manipulating the amount of PVP in the blended membranes. The PVP weight loss in the aqueous medium was negligible.

メチルグリコールキトサン，（カルボキシメチル）デキストランおよび硫酸エステル化ポリビニルアルコールからなる高分子電解質複合体膜の透過性 ＩＩ 標題複合体膜によるアルカリ金属イオンの能動輸送と選択透過

多糖類であるメチルグリコールキトザンと(カルボキシメチル)デキストラン,そして合成高分子である硫酸エステル化ポリピニルアルコールの3種類の高分子電解質から合成した水に難溶性な高分子電解質複合体を,キャスト法により成膜した。得られた高分子電解質複合体膜について,アルカリ金属イオンのNa+およびK+に対する能動輸送ならびに選択透過性を検討した。その結果,この膜は,能動輸送および選択透過機能をもっていることが明らかとなった。これは,水素イオン濃度差を騒動力とし,水素イオン濃度の変化にともなう膜の化学的性質の変化,およびキャリヤーの親和性に起因するものと推論される。