High-Velocity Microsprays Enhance Antimicrobial Activity in Streptococcus mutans Biofilms

Area of Science:

• Oral microbiology
• Biomaterials science
• Biofluid dynamics

Background:

• Streptococcus mutans biofilms contribute to dental caries development.
• Biofilm structure impedes antimicrobial agent penetration.
• Novel delivery methods are needed to overcome biofilm resistance.

Purpose of the Study:

• To assess high-velocity water microsprays for enhanced antimicrobial delivery into S. mutans biofilms.
• To compare microspray delivery with diffusive transport and mouthwash methods.
• To investigate the effect of impact angle on delivery efficiency.

Main Methods:

• Exposed 3-day-old S. mutans biofilms to microsprays with 90° or 30° impact angles.
• Used 1-µm tracer beads and antimicrobial solutions (chlorhexidine/cetylpyridinium chloride).
• Analyzed bead penetration depth and bacterial killing zones using confocal microscopy and viability staining.

Main Results:

• Microsprays delivered significantly more microbeads deeper into biofilms than diffusion or mouthwash.
• Microsprays achieved greater antimicrobial penetration and bacterial killing depth.
• A 30° impact angle delivered 16x more microbeads and increased bacterial killing by ~20% compared to a 90° angle.

Conclusions:

• High-velocity water microsprays are effective for delivering microparticles and antimicrobials into S. mutans biofilms.
• Shear stresses and physical restructuring enhance delivery, suggesting a novel therapeutic approach.
• Optimizing impact angle is crucial for maximizing biofilm disruption and antimicrobial efficacy.