Effects of chitin and chitosan particles on BALB/c mice by oral and parenteral administration.

Chitin and chitosan were administered orally and parenterally into mice and their toxicity was investigated. When 5 mg of chitin were injected intraperitoneally every 2 weeks over a 12-week period, the mice were apparently normal, but histologically, many macrophages with hyperplasia were observed in the mesenterium and foreign-body giant-cell-type polykaryocytes were observed in the spleen. The polykaryocytes were also observed in the spleen of the mice injected subcutaneously with 5 mg of chitin, but no other changes were observed. When 5 mg of chitosan were injected intraperitoneally, the body weights of the mice decreased significantly and inactivity was observed in the fifth week. Histologically, many macrophages with hyperplasia were observed in the mesenterium. Subcutaneous injection of 5 mg of chitosan did not evoke the general and cellular abnormalities. Oral administration of 5% chitosan via a casein diet caused mouse body weights to decrease and also decreased the number of Bifidobacterium and Lactobacillus in normal flora of the intestinal tract. These results indicate that special care should be taken in the clinical use of chitin and chitosan over a long time period.

Evaluation of chitin and chitosan on open would healing in dogs.

Analysis on the accelerating effects of open wound healing by chitin and chitosan were carried out in dogs. Two, square, full-thickness wounds of skin (2 x 2 cm2) were created on the each dog's both sides of dorsal midline at 0, 14, 21, and 24 days. In one dog, one wound (left side) was treated with chitin (chitin group) and the other wound (right side) was not treated (control group). In another dog, one wound (left side) was treated with chitosan (chitosan group) and the other wound (right side) was not treated (control group). At 28 days after initial wounding, each wound site including surrounding tissue was taken for macroscopic and histological observations. Reepithelialization tended to be greater in chitin and chitosan groups than in the control group. However, when the scores of reepithelialization and granulation tissue were evaluated statistically, there was no significant differences in three groups during experimental period. Number of inflammatory cells was greater statistically in level in the control group than those in chitin and chitosan groups at 28 days after wounding. Many rete ridges were observed in the control group but very few in the another groups.

Effects of chitosan on experimental abscess with Staphylococcus aureus in dogs.

An abscess was developed experimentally by a subcutaneous inoculation of Stapylococcus (S.) aureus T-6 with a 4-cm silk suture in dogs. After draining the pus, the abscess was treated with a suspension of finely granulated chitosan (chitosan group), ampicillin (ampicillin group), or saline (control group) (Day 0). The chitosan group was further divided into 3 subgroups (0.01, 0.1, and 1.0 mg/subgroups). Similar treatment was repeated after 4 days (Day 4), followed by euthanasia on Day 8. The wound cavity contraction rate was calculated by measuring the wound cavity diameter by a sound on Days 0, 4 and 8. The wound cavity contraction rate was significantly higher in the ampicillin, 0.1 mg chitosan, and 1.0 mg chitosan groups than in the 0.01 mg chitosan and control groups on Days 4 and 8 (p < 0.05). In the 0.1 and 1.0 mg chitosan groups, the abscess healed completely in 6 out of 11 (55%), and 9 out of 10 cases (90%), respectively, by Day 8. In the ampicillin group, 4 out of 10 cases (40%) healed completely by Day 8. No healing occurred in the 0.01 mg chitosan and control groups. Histologically, the granulation tissue formed had abundant vascularization in the 0.1 and 1.0 mg chitosan groups on Day 8.

Polymeric N-acetyl-D-glucosamine (chitin) induces prostaglandin E2 in dogs.

The level of prostaglandin E2 (PGE2) in the exudate induced by subcutaneous implantation of a complex formed from non-woven fabric of polyester (NWF) and polymeric N-acetyl-D-glucosamine (chitin) (chitin/NWF) or by implantation of NWF in dogs was measured by radioimmunoassay. The amount of PGE2 in the exudate induced by chitin/NWF was about five times as high as that in the exudate induced by NWF (p < 0.05), while the level of PGE2 in the exudate was similar to that in serum.

Migration of canine neutrophils to chitin and chitosan.

Suspension of chitin and chitosan particles (mean size of 1 micron) were found to attract canine neutrophils chemotactically as determined by a checkerboard assay through polycarbonate filter with 5 microns pore size in Blind well chamber. Suspension of chitin induced chemokinetic migrations of the neutrophils. These evidences might reflect accumulation of neutrophils to chitin- and chitosan-implanted regions in dogs.

Behaviour of mouse macrophage cell line and mouse fibroblast on copolymers containing cellulose triacetate.

Copolymers containing cellulose triacetate were prepared under various conditions. A bacteriological plastic dish was coated with the copolymer (HCTA-MDI copolymer) composed of hydrolysed cellulose triacetate (HCTA) and diphenylmethane diisocyanate (MDI). The deacetylated copolymer (DA-copolymer) was prepared by the deacetylation of HCTA-MDI copolymer. The behaviour of animal cells such as a mouse macrophage cell line (A640-BB-2 cells) and a mouse fibroblast (3T6 cells) on prepared dishes was investigated morphologically. A640-BB-2 cells showed good adhesion and smooth spreading, and 3T6 cells also showed good adhesion and sufficient cell growth on the dish coated with HCTA-MDI copolymer. These results suggest that these copolymers are useful for biomedical materials.