Nanocomplexes of carboxymethyl chitosan/amorphous calcium phosphate reduce oral bacteria adherence and biofilm formation on human enamel surface

Abstract

Objectives: This study investigated the effect of CMC/ACP on oral bacteria adherence and biofilm formation on the enamel surface as well as the underlying mechanism to determine the anti-cariogenic potential of CMC/ACP.

Methods: A mineral solution of CMC/ACP was characterised by transmission electron microscope. The bactericidal activity of CMC/ACP was evaluated with the plate count method. An in vitro biofilm model was established on saliva-coated enamel blocks; the effect of CMC/ACP on the adherence of Streptococcus mutans and Streptococcus gordonii to and biofilm formation on these blocks, as well as co-aggregation of Fusobacterium nucleatum was assessed by scanning electron microscopy, crystal violet staining, and confocal microscopy. Bacterial surface charge was estimated with the cytochrome c binding assay and by zeta potential measurement.

Results: CMC/ACP nanocomplexes inhibited S. mutans and S. gordonii adherence to enamel blocks by 90% and 86% (P < 0.01), respectively, and biofilm formation by 45% and 44% (P < 0.01), respectively, after 24 h without bactericidal activity. CMC/ACP reduced F. nucleatum attachment to streptococcal biofilm by 75% (P < 0.01) while also altering cytochrome c binding to bacteria and reducing the zeta potential of the bacterial suspension.

Conclusions: CMC/ACP nanocomplexes inhibit cariogenic bacterial adherence, co-adhesion, and biofilm formation on the enamel surface, possibly by altering bacterial surface charge and enhancing the flocculation effect. As an agent that promotes remineralisation and has anti-cariogenic effects, CMC/ACP can be used to prevent and treat early caries and white spot lesions.

Keywords: Biofilm formation; Carboxymethyl chitosan/amorphous calcium phosphate; Enamel; Microbial adherence; Nanocomplexes; Oral bacteria.