Graphene Oxide Quantum Dots Enhance Antibacterial Efficacy of Sodium Hypochlorite and Mitigate Cytotoxicity to Stem Cells From the Apical Papilla: An in Vitro Study

AIM: Sodium hypochlorite (NaOCl) is considered the gold standard irrigant in regenerative endodontic therapy (RET) due to its potent antimicrobial activity. However, its clinical application presents a significant paradox: the concentrations required for effective debridement can cause irreversible cytotoxicity to stem cells from the apical papilla (SCAPs), while lower concentrations often fail to eliminate biofilms within the complex root canal system. Graphene oxide quantum dots (GOQDs) are zero-dimensional carbon-based nanomaterials with intrinsic peroxidase-like activity and reactive oxygen species (ROS) scavenging capabilities. This study investigated whether GOQDs could simultaneously enhance the antibacterial efficacy of NaOCl while mitigating its cytotoxic effects on SCAPs. METHODOLOGY: The antibacterial effect of GOQDs (50 μg/mL) combined with NaOCl (1.5%) was evaluated against planktonic bacteria and single-/multi-species biofilms of Enterococcus faecalis and Streptococcus gordonii using growth curve monitoring, colony-forming unit counting, crystal violet staining, CCK-8 assay and confocal laser scanning microscopy. The underlying mechanisms were investigated via scanning electron microscopy, SYTO 9/propidium iodide membrane integrity assay, DCFH-DA intracellular ROS detection and methylene blue decolorization assay. The cytoprotective effect of GOQDs on NaOCl-exposed SCAPs was assessed using CCK-8, live/dead staining and DCFH-DA ROS staining. RESULTS: GOQDs enhanced the antibacterial and anti-biofilm activity of NaOCl against both planktonic bacteria and biofilms. Mechanistically, GOQDs physically disrupted bacterial cell membranes and augmented NaOCl-mediated oxidative degradation via peroxidase-like catalytic activity, as evidenced by methylene blue decolorization (catalytic enhancement rate: 55.9%). Notably, GOQDs did not elevate bacterial intracellular ROS levels; instead, they enabled a transient ROS burst followed by rapid consumption. Furthermore, GOQDs significantly mitigated NaOCl-induced cytotoxicity in SCAPs, restoring cell viability from approximately 3% (NaOCl alone) to 15% (combination group) and reducing ROS overproduction. CONCLUSIONS: GOQDs offer a potential strategy to address the disinfection-regeneration conflict in RET by enhancing NaOCl-mediated biofilm eradication while simultaneously scavenging ROS to protect SCAPs from oxidative damage. This concentration-dependent dual functionality positions GOQDs as a promising adjunctive agent to optimise irrigation protocols and advance clinical outcomes in regenerative endodontic therapies.