The Fluoride-containing Bioactive Glasses With Additional Copper Enhance The Inhibition On Streptococcus Mutans Activity And Biofilm Formation

Background:Dental caries is a multifactorial disease mainly caused by bacteria such as Streptococcus mutans,and seriously threaten oral health.The fluoride-containing bioactive glasses（FBG）are able to degrade in saliva and controllably release F^-,Ca²⁺and PO₄^3-,to facilitate acid-resistant fluorapatite formation and achieve antibacterial effects.However,the formation of fluorapatite in high fluoride-containing BG was inhibited,while the antibacterial performance of low fluoride-containing BG was not ideal.Therefore,the addition of copper into the low fluoride glasses may further improve their antibacterial performance.Objective:To design and synthesize a series of low fluoride-containing BG with varying amount of copper（FCu BG）.To systematically evaluate the effects of additional copper on glass structure,bioactivity,biocompatibility and antibacterial performance against S.mutans.Methods:A series of FCu BG with the addition of Cu O（0-5 mol%）were synthesized by the melt-quench method.The structure of FCu BG were studied by XRD,FTIR,DSC,MAS-NMR.The bioactivity and biocompatibility of FCu BG were evaluated by FTIR,ICP-OES,ISE and CCK-8,respectively.The antibacterial effect and the potential mechanism of FCu BG against S.mutans were investigated by Alamar Blue,CFU counts,SEM,LIVE/DEAD staining,TEM and RT-q PCR.Results:1.The incorporation of copper did not change the Q²structure of the glass,and all the studied glasses were amorphous.The glass transition temperature decreased with increasing copper content in glass compositions.2.The all studied glass showed good bioactivity.3.Glasses with low copper content（≤2 mol%）showed non-cytotoxic to osteoblasts.4.FCu BG had a significant inhibitory effect on S.mutans,and their antibacterial performance increased with an increase in copper content.5.FCu BG also inhibited the formation and dispersion of S.mutans biofilms significantly.6.SEM results showed that the morphology of S.mutans were distorted by the copper-containing glasses.Additionally,TEM showed that the cell wall was dissolved and the cell membrane was damaged.The needle-like fluorapatite entered the cell and deposited,and further destroying the genetic material of S.mutans.7.FCu BG significantly down-regulated the expression of genes related to S.mutans extracellular polysaccharide synthesis（gtf B and gtf C）,quorum-sensing system（com D and com E）and acid production（ldh）.Conclusions:Adding copper into fluoride-containing BG promoted the formation of fluorapatite and significantly improved the antibacterial performance of glasses.FCu BG dissolved the cell wall of S.mutans,and destroy the integrity of cell membrane by a synergetic effect of Cu²⁺and fluorapatite,eventually resulting in bacterial death.FCu2BG demonstrated a good bioactivity,biocompatibility and the best antibacterial performance,which provided tremendous potential to serve as an additive for oral caries prevention drugs or care products.