Exploratory study of nanoparticle interaction with intraorally formed dental biofilms

Abstract

Background The development of nanoparticles offers promising potential for improving biofilm management; however, the biofilm itself acts as a diffusion barrier, limiting effective treatment. This study aimed to investigate the adsorption and diffusion of nanoparticles in an intraorally formed biofilm. Methods Bovine enamel specimens (n=24) were mounted on customized maxillary splints and worn intraorally by two subjects for 24 h to allow biofilm formation. Specimens not exposed to the oral cavity served as controls (n=12). Ex vivo, 20 nm gold nanoparticles with a low-charge polymer outer layer were applied to the biofilm for 10 to 30 min, followed by either a single wash, 20 washes with water, or 24 h of water storage. The outer surface and basal layer of the biofilm were analysed using scanning electron microscopy, while cross-sections were examined using transmission electron microscopy. Results After 24 h of intraoral exposure, enamel was covered by a globular-structured pellicle with bacterial adhesion and occasional biofilm formation, more pronounced in subject 2. Both facilitated nanoparticle adsorption, which increased with exposure time and remained detectable after 20 washes. In subject 2, distinctly more nanoparticles persisted after 24 h of water storage. Transmission electron microscopy confirmed outer surface retention without penetration into deeper biofilm layers. Conclusions The diffusion of 20 nm nanoparticles in dental biofilms appears limited, leaving open questions regarding the optimal nanoparticle size for effective biofilm management and their toxicological implications.