Effects of nano-hydroxyapatite on the formation of biofilms by Streptococcus mutans in two different media.

OBJECTIVES

The aim of this study was to examine the effect of nano-hydroxyapatite (nHA) on biofilm formation by Streptococcus mutans, which is actively involved in the initiation of dental caries.

DESIGN

The effects of nHA on growth and biofilm formation by S. mutans were investigated in two media: a saliva analog medium, basal medium mucin (BMM); and a nutrient-rich medium, brain heart infusion (BHI); in the presence and absence of sucrose.

RESULTS

Sucrose enhanced the growth of S. mutans in both media. In the presence of sucrose, nHA enhanced bacterial growth and biofilm formation more in BMM medium than in BHI. nHA also affected the transcription of glucosyltransferase (gtf) genes and production of polysaccharide differently in the two media. In BHI medium, the transcription of all three gtf genes, coding for enzymes that synthesize soluble and insoluble glucans from sucrose, was increased more than 3-fold by nHA. However, in BMM medium, only the transcription of gtfB and gtfC, coding for insoluble glucans, was substantially enhanced by nHA.

CONCLUSIONS

nHA appeared to enhance biofilm formation by increasing glucosyltransferase transcription, which resulted in an increase in production of insoluble glucans. This effect was influenced by the growth conditions.