Sustainable inhibition efficacy of liposome-encapsulated nisin on insoluble glucan-biofilm synthesis by Streptococcus mutans.

CONTEXT

Dental caries are an infectious oral bacterial disease caused by cariogenic streptococci. These streptococci inhabit dental biofilms which comprise insoluble glucans.

OBJECTIVE

To prevent dental caries, nisin, a suitable agent active against Gram-positive bacteria, was examined in vitro for its ability to suppress insoluble glucan-biofilm synthesis by cariogenic streptococci.

MATERIALS AND METHODS

To investigate glucan-biofilm synthesis by a typical cariogenic streptococcus, Streptococcus mutans 10449, the naked form of nisin was loaded onto a 96-well microplate in vitro model. To prolong the efficacy of nisin as a preventive agent, liposome-encapsulated nisin (nisin-liposome) was examined for its ability to inhibit the synthesis of glucan-biofilms on microplates.

RESULTS

Naked nisin (100 pmol) completely suppressed insoluble glucan-biofilm synthesis by S. mutans 10449 following 1 h cultivation in 96-well microplates. The concentration of nisin-liposome required for the efficacious inhibition of glucan-biofilm synthesis was four times lower than that of naked nisin following 2 h cultivation. In particular, nisin-liposome (30 pmol nisin equivalent) prolonged the inhibitory activity of nisin against glucan-biofilm synthesis by S. mutans 10449 for up to 6 h, while naked nisin (30 pmol) gradually lost this inhibitory activity over the same period. In vitro release assay of nisin from the liposome showed that 76% nisin was released within 6 h.

DISCUSSION AND CONCLUSION

The findings indicate the usefulness of nisin-liposome for the sustained release of nisin. Thus, nisin-liposome could play a potential role in preventive medicine as an inhibitor of the glucan-biofilm synthesis.