Constructing two bifunctional tooth-targeting antimicrobial peptides for caries management: an in vitro study

Objectives: Caries is a significant public health challenge. Herein, novel tooth-targeting antimicrobial peptides (HABPs@AMPs) were developed by combining the antimicrobial peptide DJK-5 with hydroxyapatite (HA) binding peptides, providing a potential new strategy for caries management.

Materials and methods: The minimal inhibitory concentration (MIC₁₀₀) and minimal biofilm inhibitory concentration (MBIC₁₀₀) values of HABPs@AMPs were determined via micro-broth dilution and crystal violet staining. The affinities of the peptides for HA were measured by mass depletion, and the abilities of peptides to inhibit Streptococcus mutans (S. mutans) biofilm formation and kill 3-day-old S. mutans biofilms were evaluated in HA disk and tooth slice biofilm models through confocal laser scanning microscopy. Biocompatibility with human gingival fibroblasts was evaluated via CCK8 assays.

Results: The best performing peptides, DJK-5@SVA and SVA@DJK-5 exhibited MIC₁₀₀ and MBIC₁₀₀ values of 31.25 µg/mL, similar to DJK-5. DJK-5@linker2@YSL had the highest affinity for HA, followed by YSL@DJK-5, DJK-5@linker1@YSL, and DJK-5@SVA. Moreover, the biofilms on HABPs@DJK-5 coated surfaces had more dead bacteria by volume than those in the DJK-5 and SVA groups (p < 0.05). DJK-5@SVA outperformed SVA@DJK-5 and DJK-5 in killing 3-day-old S. mutans biofilms (p < 0.05). With the exception of established biofilms on tooth slices, DJK-5@SVA exhibited greater killing efficiency in the bottom half of the biofilms than in the top half. The CCK-8 assay results confirmed peptides' biocompatibility.

Conclusions: DJK-5@SVA with good affinity for HA, has excellent biocompatibility and efficacy against S. mutans biofilms.

Clinical relevance: HABPs@AMPs with effective inhibitory effects on the growth of S. mutans and biofilm formation, contributing to intraoral targeted application AMPs and providing a new strategy for caries management.