Biofunctionalized zinc peroxide nanoparticles inhibit peri-implantitis associated anaerobes and Aggregatibacter actinomycetemcomitans pH-dependent

Abstract

For dental implants the accumulation of anaerobic bacteria is a main reason for peri-implant inflammation, which untreated can lead to implant loss. Oxygen releasing substances may act as antibacterial agents. In this study glucose-1-phosphate (Glc-1P) biofunctionalized zinc peroxide (ZnO₂) nanoparticles of four different synthesis ratio (1–10:1) and sizes (4–5 nm) were tested against the anaerobes Fusobacterium nucleatum, Porphyromonas gingivalis, and Prevotella intermedia, as well as against Aggregatibacter actinomycetemcomitans, Enterococcus faecalis, Staphylococcus aureus, Lactobacillus paracasei, and the yeast Candida albicans. Nanoparticles stabilized with o-phosphorylethanolamine, bis[2-(methacryloyloxy)ethyl] phosphate, or dioctyl sulfosuccinate instead of glucose were used as controls. For every combination of test strain and nanoparticle both, the minimal inhibitory (MIC) and minimal microbicidal concentration (MBC or MFC) were determined under different pH conditions in microtiter plates. Furthermore, transmission electron (TEM) and fluorescence microscopy after live-dead-staining was performed on selected combinations of pathogen and nanoparticle in order to visualize the interactions. The ZnO2/Glc-1P nanoparticles had an inhibitory effect on gram-negative anaerobes and on A. actinomycetemcomitans with a pH-dependent MIC ≥25 μg/ml and MBC ≥50 μg/ml, while the gram-positive species tested and C. albicans were not inhibited. In TEM images, attachment of nanoparticle-chains to the bacterial outer membrane and subsequent penetration was found together with an intracellular oxygen release. For nanoparticles with other stabilizers than glucose an invasion was only seen in elongated, dividing cells, possibly because of the more porous cell wall in the parting layer. Decorating ZnO2 by glucose-1-phosphate is a Trojan horse approach to permit their uptake in gram-negative oxygen-sensitive bacterial cells.