The Antibacterial Activity And Application Of Chitosan/Carboxymethyl Chitosan In Dentelcaries And Peridontitis

Chitosan, the dcacelylatcd derivative of chitin, is the only basic polysaccharide in nature. Special chemical structure brings it interesting bioactivities, such as antimicrobial, antitumor, immune enhancing effect and tissue regenerative activities. It has been widely used in medical field due to its additional biocompatibilily and biodegradability. Because it can be easily formed into film, gel and microparticlc, so it can meet the necessities of various drug delivery methods. In addition, its special bioadhesive property helps to prevent the rapid elimination caused by the Hushing action of saliva. So chitosan has great application potential in dcntalcaries and peridontitisAs an important derivative of chitosan, carboxymethyl chitosan (CMCS) has good water solubility besides the characteristic bioactivities and biocompatibility of chitosan. Because of its potential stimulatory effect on the proliferation of periodontal ligament cells (PDLCs), it can be formulated into excellent guided tissue regeneration (GTR) membrane if its degradability and strength can be appropriately controlled by blending with other macromolecular substances or additives.The contents of this study are divided into the following parts:1. Selection of the pH value and molecular parameter in the application of chitosan in dctcnalcariesThe effect of pH value, degree of dcacetylation (DD) and molecular weight (Mw) on the antibacterial activity of chitosan against S. mutatis GS-5 was evaluated in vitro, and the factors suited for clinical application were determined based on the results and the questions important for the preparation and application of chitosan formulations. In addition, the antibacterial effect of chitosan against other key pathogenic bacteria was studied to verify the feasibility. At the concentration of 5 mg/ml, chitosan with 50% DD could not inhibit the growth of S. mutatis GS-5 at pH 6.5 and 7.0, but can at pH 6.0 and 5.5 without difference. When the concentration is 2 mg/ml and the pH value is 6.0, chitosan with 50% DD did not demonstrate antibacterial activity but chitosan with 81% and 95% DD both had good effect; and chitosan with Mw above 23 kD all can inhibit the growth of S. mutatis GS-5 effectively, but chitosan with a Mw of 6 kD had not antibacterial activity.2. The anticariogenic effect of chitosan and its mcchenismTo evaluate the anticariogenic effect of chitosan, the effect of chitosan (DD 81%, Mw 210 kD) on the growth, adherence and glycolytic pH-drop properties of 5. mutans GS-5 were studied in vitro, chitosan made the glass surface adherence invalid, hydrophobicity decreased, but could not inhibit the activity of glucosyl transfcrase (GTF) to synthesize water insoluble glucan. Compared to the low glycolytic pH (3.52) of the control group, the high pH value (5.73) of the group with 1/2 MIC chitosan, indicate that chitosan can effectly inhibit the glycolytic pH-drop caused by excess glucose..3. The application of chitosan in drug controlled release system to be used in periodontitisFilms containing metronidazole (MTZ) with different ratio of chitosan and polyvinylpyrrolidinc (PVP) were prepared using glycerol phosphate as cross-link agent. Each formulation was characterized in terms of surface morphology, swelling behavior and drug release. When the proportion of PVP is less than 30%, MTZ were secreted in needle crystal or particle and released significantly within short time, but the swelling ratio of the films arc comparable to the chitosan film. When the proportion of PVP is above 30%, MTZ was well homogenized in the film and released at higher speed, and the films swelling significantly. With 30% PVP, MTZ was well composed in the film and released nearly at zero speed 24 h later, and the swelling ratio is the lowest among the films.4. The effect of CMCS on the proliferation and cell cycle of PDLCsVarious CMCS with different DD and degree of substitution (DS) were prepared from chitosan by changing the agents used in the reaction. The effect of these samples on the proliferation of PDLCs was examined in vitro by MTT method. Within the concentration of 200-12. 5 w g/ml, all the samples demonstrate stimulatory effect on the proliferation of PDLCs, and the effect increased when the concentration improved. The sample with relatively high DD and low DS have great stimulatory effect on the proliferation of PDLCs, whose effect on the cell cycle of PDLCs was further studied by How cytomctry using PI as DNA stain. After being treated with this sample at aconcentration of 200 n g/ml lor 48 h, the percentage of S-phase cells and PrI in the sample group were higher than that in the control group, but the percentage of Gpphase cells decreased. In summary, CMCS demonstrated stimulatory effect on PDLCs which appears to be dependent on it being highly deacetylatcd and by stimulating the d to S transition.