Inhibition of Oral Biofilm Formation by Zwitterionic Non-fouling Coating

Objectives: Inhibition of oral biofilm formation is critical to prevent caries and periodontitis. Biofilm formation is initiated by adhesion of salivary pellicle (composed of salivary proteins and glycoproteins) to the tooth surfaces, followed by bacterial adhesion and proliferation. Our previous studies have demonstrated that ultra-hydrophilic zwitterionic polymer, poly(carboxybetaine) (pCB) could resist non-specific protein adsorption. Therefore, we hypothesized that pCB coated on the tooth surface could resist salivary pellicle and subsequent bacterial adhesion. The objectives of this study were to develop a specific zwitterionic polymer that can be stably coated on the tooth surfaces and to test its non-fouling effectiveness.
Methods: A catechol derived L-3,4-dihydroxyphenylalanine (DOPA) was conjugated to pCB to serve as a surface anchoring group. The pCB-DOPA polymer was coated on the hydroxyapatite (HA) and enamel discs by immersion and confirmed by Raman Spectroscopy. The discs were incubated in 1 mg/ml fibrinogen from human plasma at 37°C for 90 min and non-fouling effectiveness was determined by protein adsorption assay (ELISA). Bacterial adhesion assay was performed by fluorescence microscopy and images were quantitatively analyzed by ImageJ software.
Results: The coating of pCB-DOPA was confirmed by Raman Spectroscopy with a characteristic peak of the catechol group. The protein adsorption was significantly reduced (p<0.05) to 15.2% and 10.1%, respectively on pCB-DOPA coated HA and enamel discs. The coated samples demonstrated significantly fewer (p<0.05) adhered Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus mutants compared to uncoated samples.
Conclusions: A zwitterionic non-fouling polymer (pCB-DOPA) was successfully coated on HA and enamel surfaces. The protein adsorption and bacterial adhesion were significantly reduced on these coated surfaces. This method provides a novel approach to resist biofilm formation and could be potentially applied in the prevention of caries and periodontal diseases.