The Studies On Preparation, Degradation, Release Of Chitosans Membrane With Different Molecular Weight And Chitosans' Antibacterial Effect

[Objective]Dental implants were used in prosthodontics widely,many investigation were focus on enhancing integration between bone tissue and implant.Growth factors were used to accelerate osseous integrations.Usually,growth factors were destroyed easily and fixed difficultly in oral implantology area.It is suggested that drug sustained -release system for the growth factors be initiated.The aim of this study was to produce low weight chitosans and identify the preparation,degradation,release of membrane with different molecular weight chitosans.The antibacterial effects of chitosans were investigated.The result of study will benefit for chitosans using in oral implants.[Material and Methods]1.Water-soluble chitsans of low molecular weight were produced in the system of hydrogen peroxide and used chitosans with 1×10~4 molecular weight as materials.Their corresponding molecular weights were further determined with Ubbelohde viscometer.Chitosans membrane and gelatin-chitosans membrane were prepared with different molecular weight chitosans.The methods of preparing low molecular weight chitosans films were identified.2.This degradation rate was tested to assess time affecting to degradations.Membranes were divided into 4 groups;each group has 7 types of membranes.The membrane was put in a test tube with 30ml buffer solution and kept in 37℃shaking box.The degradation rates were calculated by testing lost weight of membrane.Further more degradation rate was to evaluate the relationship between degradation and quantities of buffer solutions.The chitosan and gelatin-chitosan membranes with 1×10~4 molecular weight were put in the tubes which have the 5,10,15,20,25,30ml buffer solutions and kept in 37℃shaking box one week.The degradation rate was test by same method mentioned above. Finally degradation was tested to investigate the degradation associated with varieties of enzymes.7 types chitosan membranes were placed in tubes which have 20ml buffer solutions and enzyme(there were 4 kinds of enzymes);Kept in 37℃shaking box 4hours then calculated the degradation.3.The antimicrobial activity of chitosans was tested by Kirby-Bauer method using St.aureus to compare activities with different molecular weight.The 2%chitosan's solution were prepared,their molecular weight were 4.5×10~5,2×10~5,1×10~5,3.2×10~4,2.19×10~4,1.26×10~4,6.3×10~3,5.5×10~3,3×10~3 respectively.Gelatins with different concentration(1mg/ml,2mg/ml,3mg/ml,4mg/ml)were added in chitosans' solutions to evaluate the change of antimicrobial activity.[Results]1.Preparation chitosan with low molecular weight:Water-soluble chitsans of were produced in the system of hydrogen peroxide and their molecular weight were lower to 3000.The results of experiment have indicated that 40ml chitosan solution (concentration 2mg/ml) with high molecular weightcould prepare membranes. When preparing low molecular weight chitosan membranes,gelatin and glycerin was needed add.2.Degradation of chitosan membrane with different molecular weight: Gelatin-chitosan membrane was degraded faster than chitosan membrane at same PH. The degradation rates of membrane were increased with molecular weight decrease. All kinds of chitosan membranes were degraded completely in two weeks.Enzyme accelerated the degradation of chitosan membranes,their effect were associated with the types of enzymes.In respect of chitosans membranes' degradation,cellulose was the best and lysozyme was the worst,papain,lipase were between two of them. Gelatin-chitosan membranes suddenly release remarkably.All types of membrane released protein regularly in a period.3.The antimicrobial activity of chitosan with different molecular weight:The antimicrobial activities of chitosans were associated with its molecular weight.The antimicrobial activities were strengthens with the increasing of molecular weight.The antimicrobial activities of chitsan with molecular weight 6300 were the strongest,and then the acitivity decrease gradually.[Conclusion]Different molecular weight chitosans were produced by chemicals methods and different character chitosan membrane was prepared.The result suggest that high molecular weight chitosans(4.5×10~5,2×10~5,1×10~5 molecular weight) prepare membranes without add other materiala.Gelatin and glycerin was added in preparation low weight chitosan membranes.The degradation of chitosans membrane was faster than gelatin-chitosan membrane.Chitosans membrane was degraded in 14 days completely,so it is unsuitable for application in surface treatment.The rate of degradation and release about gelatin-chitosan membrane were optimal.It is suggested that gelatin-chitosan membranes with molecular weight 3000 use in dental implant as a protein release system.