Chitin Films Research Articles

医療と膜 膜の医療への応用

Modified natural and synthetic polymers and phospholipids have been studied as membrane materials in medical and pharmaceutical fields. Chitin prepared from the carapace of carb and shrimp is biodegradable polymer of acetylglucosamine and easily forms a film and fiber from solution. The chitin film protects from an attack of bacteria, when covered on the wounded site and accelerates the recovery. Polymer membranes have been used as materials of microcapsules containing drugs inside, through oral, subcantaneous and intramuscular administrations. These microcapsules administred orally are capable to release drugs at tageting organ in time-dependent manner. Biodegradable polymer microcapsule implanted in muscle through injection, releases drugs for over 4 weeks at a constant rate.Biodegradable and biocompatible phospholipids has been applied for the preparations of intraveneous administrations as a liposome and a microsphere. Liposomes and microspheres accumlate generally in reticuloendotherial system (RES). Recently RES-avoiding liposome has been developed by the modification of liposomal surface with polyethylene glycol and applied for an artificial red blood cell with undated hemoglobin. Lipid microsphere containing prostaglandin E1 and anti-inflammation drug had been applied for the cure of inflammation deseases, because the inflammation sites are macropharge-rich.

Specific induction of encystment ofLagenidium giganteum zoospores by concanavalin A and derivatives of chitin and chitosan

Zoospores of the mosquito pathogenic fungusLagenidium giganteum preferentially attach to and encyst on the cuticular surface of the immature stages of many species of mosquitoes as the initial step in the infection process. Recognition by zoospores of specific chemical or physical signals on the cuticular surface triggers attachment. A number of compounds likely to be present on the surface of mosquito larvae were evaluated for efficacy in eliciting zoospore encystment. Free amino acids and oligomers, a number of phenolic and polyphenolic compounds and most carbohydrates did not induce encystment at concentrations less than 500 μg/ml. Colloidal chitin and chitin films were also ineffective as was O-carboxy-methylchitin; however, glycol chitin and glycol chitosan induced rapid encystment at concentrations at or below 1 μg/ml. Zoospores also attached to and encysted in great numbers on fibers of oxycellulose, but not on cellulose. Concanavalin A was the only lectin which induced encystment at concentrations less than 10 μg/ml, which suggests that a glycoprotein with terminal mannose and/or glucose residues is involved in encystment. A number of phenols were metabolized by peroxidase on the zoospore surface. Addition of hydrogen peroxide to zoospore suspensions reduced the time needed to induce zoospore encystment by some phenols; however, there was no consistent relationship between the presence or absence of this synergistic effect and the ability ofL. giganteum peroxidase to metabolize a given substrate. The sterol-binding compound amphotericin B induced immediate encystment at 3.5 μg/ml, suggesting that sterols, which are required for the induction of zoosporogenesis, were present on the zoospore membrane.

Ｎ，Ｎ′‐ジアセチルキトビオース醗酵生産においてコロイド状キチンの代替えとなるキチンの形態

Colloidal chitin is the most suitable form of chitin for the production of N, N'-diacetylchitobiose _??_(G1cNAc)2_??_ by Bacillus licheniformis X-7u, but it is unsuitable for use in mass production because it is prepared with difficulty. We therefore sought forms of chitin that are easily prepared and that can be used instead of colloidal chitin. Chitin prepared by the soaking of chitin film from prawn pleon cuticle in 25% HCI at 20°C for 1 hr gave satisfactory results. When strain X-7u was cultivated with the HCl-swollen chitin, 5.1 g/l (GlcNAc)2 accumulated within 4 days. The (GIcNAc)2 yields based on the starting material, the chitin film, when HCI-swollen chitin and colloidal chitin were used were 32% and 35%, respectively.

Studies of Molecular Motions in Acylchitin Films by Means of Spin-Probe Technique

The molecular motions in acylated chitins, including acetyl, propionyl, butyryl, caproyl, capryl, lauroyl, and benzoylchitin, were investigated by ESR measurements with 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl (TEMPO) as a spin-probe. Introduction of a longer side chain into the chitin molecule resulted in a remarkable lowering of the temperature at which the separation between the outer two extrema of the ESR spectrum decreases adruptly (TN). Below and above TN, two kinds of motional process were observed, one at a lower temperature having a smaller activation energy and the other at a higher temperature with a larger activation energy. These processes are a small scale motion such as rotational oscillation and a large scale motion such as rotation, respectively. The activation energy of the latter process decreased with increasing chain length, except for acetylchitin. Fully acetylated chitin films were anomalous with respect to the value of the activation energy.

Studies on Chitin. IV. Preparation of Acetylchitin Fibers

Solutions of variously acetylated chitin in formic acid were prepared by freezing with addition of dicholoroacetic acid or organic solvent, and spun into diisopropyl ether to give acetylchitin fibers. 1.0 Acetylchitin fiber was also obtained by the direct acetylation of chitin fiber in a perchloric acid–acetic anhydride mixture. 1.1 Acetylated chitin fiber showed the maximum tenacity, elongation, and knot strength among the variously acetylated chitin fibers, while a maximum Young’s modulus was shown by the 1.6 acetylchitin fiber. Acetylchitin fibers have the advantage of greater tenacity and elongation in comparison with chitin fiber. These advantages contribute to the practical usefulness of chitin in spite of its poor solubility in most solvents and poor reactivity toward chemical reagents. Also the acetylchitin film prepared from formic acid–dichloroacetic acid mixture is softer and thus more pleasing to the touch than chitin film.

Studies on Chitin. III. Preparation of Chitin Fibers

The chitin fiber was obtained from a chitin-formic acid solution which was found to be spinnable. This solution was prepared through repeated freezing process by the addition of dichloroacetic acid and isopropyl ether. Dichloroacetic acid and methanesulfonic acid were also found to be solvents for chitin, though the spinnability could not be observed owing to rapid reduction of viscosity even at low temperature. Chitin fibers were successfully prepared from formic acid solution, and better qualities were found for these than for the fibers prepared through the chitin viscose. X-Ray diffraction analysis suggested that the regenerated chitin would have a similar structure to the natural chitin. The clear and flexible chitin film was prepared from formic acid–dichloroacetic acid or formic acid–urea solution by casting on a glass plate and solidifying in ethanol.

Observations on regenerated chitin films

Chitin films regenerated from shrimp shell waste were studied in order to determine stress-strain behaviour and tensile strengths as related to preferential chain orientation.

Observations on regenerated chitin films

Observations on regenerated chitin films

Infrared spectra of crystalline polysaccharides: VI. Effect of orientation on the tilting spectra of chitin films

The tilting spectra of doubly oriented crab chitin crystallites and blowfly larval cuticle chitin were observed. It has been noted that in addition to the uniaxial orientation, these samples posses different selective uniplanar orientations. For the crab chitin crystallites the 100 crystallographic planes are parallel to the film surface while for the blowfly larval chitin the 001 planes are parallel to the film surface. Based on these orientations and the observed tilting effects, a number of previously made band-assignments were confirmed and new suggestions were made for interpreting the bands at 3106, 2962 and 1619 cm −1.