Diffusion of macromolecules through nature dental plaque biofilm in vivo

Objectives:To observe the intact structure of an in vivo nature biofilm,and examine the diffusion of macromolecules with different molecular weight through this biofilm. Methods:A healthy volunteer wore special plastic slabs allowing for growth of dental plaque biofilm. After 24h,the specimens were removed and biofilms were stained using SYTO-9 fluorescent dyes which stain vital bacteria green.an intact nature biofilm structure was observed by confocal laser scanning microscopy(CLSM),then macromolecules with different molecular weights ranging from 10,000 to 2000,000(10KD,40KD,70KD,2000KD Dextran)were dripped on biofilm,the macromolecules diffusion through biofilm were dynamically recorded by CLSM.Results:An impression of intact biofilm at 24h and the distribution of cells,EPS and voids were seen,the biofilm thickness was about 24±5μ.After 1~2s,macromolecules appear within the upper layer of the biofilm,the progressive migration of the mass to greater depth through biofilm were seen,the diffusion velocity of 10KD Dextran was faster than 40KD and 70KD Dextran,within 11 seconds 10KD mass transport throughout biofilm,while 40KD and 70KD Dextran penetrate nearly 2/3 depth of biofilm.However,only slight penetration was observed for 2000KD Dextran ,Even after 120s there is no apparently diffusion through biofilm.Conclusion:An intact structure of nature dental plaque biofilm is successfully acquired,and the observation of Dextran diffusion showed that the diffusion rate of lower molecular weight Dextran is faster than that of the higher.