Iris Xiaoxue Yin,1 John Yun Niu,1 May Lei Mei,2 Jinyao Tang,3 William Ka Kei Wu,4 Chun Hung Chu1 1Faculty of Dentistry, the University of Hong Kong, Hong Kong, People’s Republic of China; 2Department of Oral Rehabilitation, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; 3Department of Chemistry, the University of Hong Kong, Hong Kong, People’s Republic of China; 4Department of Anaesthesia & Intensive Care, The Chinese University of Hong Kong, Hong Kong, People’s Republic of ChinaCorrespondence: May Lei Mei, Department of Oral Rehabilitation, Faculty of Dentistry, University of Otago, Department of Oral Rehabilitation, Faculty of Dentistry, University of Otago, PO Box 56, Dunedin, Otago, 9054, New Zealand, Email may.mei@otago.ac.nz Chun Hung Chu, Faculty of Dentistry, The University of Hong Kong, Restorative Dental Science, Faculty of Dentistry, The University of Hong Kong, 34 hospital Road, Hong Kong, NA, People’s Republic of China, Email chchu@hku.hkObjective: The objectives of this study were to develop a tooth-binding graphene quantum dots silver nanocomposites (ALN-GQDs-Ag) and evaluate their antibacterial, mineralising, and discolouring properties for the prevention of dental caries.Methods: In this study, ALN-GQDs-Ag were developed by synthesising nano silver (Ag) with graphene quantum dots (GQDs) and functionalised GQDs with alendronate (ALN). ALN-GQDs-Ag were characterised by transmission electron microscopy (TEM), zeta potential analysis, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The cytotoxicity of ALN-GQDs-Ag against human gingival fibroblasts (HGF-1) and stem cells from human exfoliated deciduous teeth (SHED) was examined using a colorimetric assay with reference to silver nitrate solution. The affinity of ALN-GQDs-Ag for hydroxyapatite particles was investigated using inductively coupled plasma spectroscopy (ICP). The antibacterial properties of ALN-GQDs-Ag against Streptococcus mutans were evaluated by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and colony-forming units counting (CFUs). The mineralisation properties of ALN-GQDs-Ag on human dentine were assessed using micro-computed tomography (micro-CT), scanning electron microscopy (SEM), and Fourier transform infrared in a biochemical cycling model. The discolouring properties of ALN-GQDs-Ag on artificial dentine caries were determined using spectrophotometry.Results: TEM, Zeta potential, XPS, FTIR, and Raman spectroscopy confirmed the synthesis of stable spherical ALN-GQD-Ag nanocomposites with a 10.3 ± 5.5 nm diameter. The colorimetric assay demonstrated that ALN-GQDs-Ag were less cytotoxic than silver nitrate to HGF-1 and SHED (p< 0.001). ICP showed that ALN-GQDs-Ag were bound to hydroxyapatite. SEM, CLSM, and CFUs showed that ALN-GQDs-Ag was bactericidal and inhibited biofilm growth of Streptococcus mutans. Micro-CT, SEM, and FTIR showed that ALN-GQDs-Ag repressed dentine demineralisation under a cariogenic challenge. Spectrophotometry revealed no significant discolouration of dentine caries in the ALN-GQDs-Ag.Conclusion: This study developed a biocompatible and tooth-binding ALN-GQDs-Ag with promising antibacterial, mineralising, and non-discolouring properties. ALN-GQDs-Ag could be a novel anti-caries agent for preventing dentine caries if translated for clinical use.Keywords: graphene quantum dots, silver nanoparticles, caries prevention, antibacterial, mineralisation