Abstract
Nanomaterials are revolutionizing the field of medicine to improve the quality of life due to the myriad of applications stemming from their unique properties, including the antimicrobial activity against pathogens. In this study, the antimicrobial and antibiofilm properties of a novel nanomaterial composed by zinc oxide nanorods-decorated graphene nanoplatelets (ZNGs) are investigated. ZNGs were produced by hydrothermal method and characterized through field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) techniques. The antimicrobial activity of ZNGs was evaluated against Streptococcus mutans, the main bacteriological agent in the etiology of dental caries. Cell viability assay demonstrated that ZNGs exerted a strikingly high killing effect on S. mutans cells in a dose-dependent manner. Moreover, FE-SEM analysis revealed relevant mechanical damages exerted by ZNGs at the cell surface of this dental pathogen rather than reactive oxygen species (ROS) generation. In addition, inductively coupled plasma mass spectrometry (ICP-MS) measurements showed negligible zinc dissolution, demonstrating that zinc ion release in the suspension is not associated with the high cell mortality rate. Finally, our data indicated that also S. mutans biofilm formation was affected by the presence of graphene-zinc oxide (ZnO) based material, as witnessed by the safranin staining and growth curve analysis. Therefore, ZNGs can be a remarkable nanobactericide against one of the main dental pathogens. The potential applications in dental care and therapy are very promising.
Highlights
Dental caries represent an increasingly serious health problem for which Streptococcus mutans has been identified as the main etiologic cause
Synthesis of zinc oxide (ZnO) nanorods (ZnO-NRs) via chemical approaches opens the route to low-cost catalyst-free mass-production of ZnO nanostructures [29,30,31,32]. Through both in vitro and in vivo systems, we have demonstrated the very low cytotoxicity of ZnO-NRs [33], together with their great potential as antibacterial material acting as nano-needles against Staphylococcus aureus and Bacillus subtilis [34]
We aim to propose the original use of a novel hybrid material, featured by ZnO-NRs grown on multilayer graphene sheets (i.e., graphene nanoplatelets (GNPs)), as antimicrobial nanomaterial against S. mutans, combining the antimicrobial effect of GNPs with the light color and biocidal properties of ZnO-NRs
Summary
Dental caries represent an increasingly serious health problem for which Streptococcus mutans has been identified as the main etiologic cause (reviewed in [1]). Similar to CNTs, graphene-based materials have received significant attention for their potential applications in the biological/medical field, including bacterial inhibition, drug delivery, and photothermal cancer therapy [17,18,19]. In this context, graphene-related structures like graphene nanoplatelets (GNPs), can represent a valuable tool in the biological/medical field, owing to the fact that their production process is very easy, inexpensive, and scalable [12]. Statistical analysis was performed by Student’s t-test (ns not significant)
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