Research On The Preparation Of Gallic Acid Poly(Propylene Carbonate)Film And Its In Vitro Antibacterial Property And Cytotoxicity

Objective:Caries is a kind of the widespread chronic diseases in the world and is characterized by high incidence and low treatment rate in China.It is not only the main disease harmful to oral health,but also an important factor affecting the whole body health.Therefore,the prevention and early treatment of caries are of great significance.In recent years,nature‐based plant extracts have become the research focus in the field of caries prevention.Among them,gallic acid（GA）,the extract of Chinese gallnut,has been proved to have effects of killing and inhibiting the growth and producing acid of cariogenic bacteria,demineralization and promoting the remineralization on the surface of demineralized dental enamel,and its biosafety is high.Poly（propylene carbonate）（PPC）,a copolymer of carbon dioxide（CO₂）and propylene oxide（PO）,is a biocompatible and biodegradable polymer that has been widely studied in the field of biomedical materials.However,its application to the prevention and treatment of oral diseases has rarely been reported.This study aims to synthesize a kind of anticarious GA-PPC film that can play the roles of slow-release antibacterial and remineralization and is safe and easy to be pasting on the teeth surfaces by patients themselves,providing new ideas for future anti-caries methods.Methods:1.GA-PPC films（GA content was 0wt%,1.25wt%,2.5wt%,5wt%,10wt%and15wt%,respectively）were developed by melt blending method as the experimental groups,and 5wt%Na F-PPC strips were developed as the positive control group.The cross-sectional morphology,mechanical and thermal properties were characterized by scanning electron microscopy（SEM）,electron universal testing machine,thermogravimetry（TG）and differential scanning calorimetry（DSC）.The drug release was determined by ferrous tartrate assays method.2.Explored the killing or inhibiting effect through analyzing the growth trend of Streptococcus mutans（S.mutans）,crystal violet staining,phenol sulfuric acid method,live/dead bacteria staining and plate counting to verify its bioavailability.3.The toxicity of GA-PPC film on L-929 cells was measured by cell counting kit-8（CCK-8）to test its biocompatibility.Results:1.GA-PPC films with molecular weight of 40,000 and thickness of 0.2 mm were synthesized successfully.GA was successfully loaded into the PPC and evenly dispersed in it.Except the 15wt%GA group,the tensile strength of the other groups had no obvious change compared with the pure PPC,which were greater than 3 MPa,with better mechanical properties.GA-PPC films had better thermal stability than Na F-PPC strips.The glass transition temperature（T_g）of GA-PPC films was not much different from that of pure PPC film.When at oral temperature,GA could be slowly and continuously released from PPC.2.GA-PPC films could inhibit the growth of S.mutans and the formation of cariogenic biofilm,and the inhibitory effect was enhanced with the increase of GA content.When the content of GA exceeded 5wt%,it showed good antibacterial effect,and when the content of GA reached 10wt%,the antibacterial effect was comparable to that of PPC containing 5wt%Na F.3.Pure PPC had no cytotoxicity.When the content of GA in GA-PPC films did not exceed 10wt%,the cytotoxicity was within the safety range,whereas GA content between 10wt%and15wt%,the cytotoxicity was high.Conclusions:The synthetic GA-PPC films had good mechanical and thermal properties,and GA could be continuously and slowly released from PPC.The 5～10wt%GA-PPC films exhibited both antibacterial activity and good biocompatibility,which were promising to be used for early prevention of caries.