Abstract: By measuring the minimal inhibitory concentration (MIC) of various antibacterial drugs commonly used in toothpaste,it is found that both cetylpyridinium chloride (CPC) and chlorhexidine have strong bacteriostatic effect on Streptococcus mutans and Porphyromonas gingivalis with the MIC below 1 mg/L.The CPC was coated with triacetyl-β-cyclodextrin (TA-CD) and ethyl cellulose (EC) and particles were prepared by spray drying.The drug-loaded particles had obvious “burst release” phenomenon,and it showed better sustained release effect after adding stearic acid (SA).In addition,the adhesion rate of the drug-loaded particles can be significantly improved after brushing,when certain amount of polyvinyl alcohol (PVA) was added.When the mass fraction of PVA is 20%,the adhesion rate of the drug-loaded particles is the highest,reaching 19.1%.The mixed bacterium biofilm was used to evaluate the bacteriostasis of drug-loaded particle (DLP-7) and CPC.The results show that the relative inhibition rate of drug-loaded particles increases continuously over time.After 4 h,the relative inhibition rate of DLP-7 is higher than CPC,which means that DLP-7 shows long-acting bacteriostasis.

Key words: long-acting bacteriostasis, spray drying, sustained release, biofilm