Dextranase enhances nanoparticle penetration of S. mutans biofilms.

BACKGROUND/OBJECTIVE: Cariogenic biofilms possess a rich extracellular polysaccharide (EPS) matrix, which can reduce the penetration of anticaries agents such as nanoparticle-based technologies. The aim of this study was to assess the potential of dextranase, an EPS-degrading enzyme, to enhance nanoparticle penetration into Streptococcus mutans in vitro biofilms. METHODS: Commercially available fluorescent nanoparticles (nanospheres, average diameter around 200 nm) were used as a proxy for nanoparticle treatments. Biofilms of fluorescent S. mutans 3209/pVMCherry were developed over 48 h in 24-well glass bottom microplates, simulating daily feast (tryptic soy broth (TSB) supplemented with 1% sucrose) and famine periods (TSB supplemented with 0.1 mM glucose). Nanoparticles were co-administered to biofilms with either dextranase (10 U/mL) or pH 6.5 phosphate buffer (placebo). Time-lapse confocal laser scanning microscopy was used to capture six image stacks over approximately 60 minutes of nanoparticle movement through the biofilm. In-house-developed quantitative image analysis methods assessed nanoparticle penetration. RESULTS: Nanoparticle signal intensity and overlapping signal with cells increased in the presence of dextranase, being significantly higher in the last two CLSM scans compared with the initial one (p < 0.05). Biofilm architecture changed under dextranase, increasing the interaction of nanoparticles with biofilm components. CONCLUSION: Dextranase showed potential to enhance nanoparticle-based anticaries therapies. KEY MESSAGES: Dextranase increases the penetration of nanoparticles in cariogenic, extracellular polysaccharide-rich dental biofilms.