Ca-Si mesoporous nanoparticles with the optimal Ag-Zn ratio inhibit the Enterococcus faecalis infection of teeth through dentinal tubule infiltration: an in vitro and in vivo study

Application of Nanomaterials in Endodontics

Recent advancements in nanotechnology have introduced a myriad of potential applications in dentistry, with nanomaterials playing an increasing role in endodontics. These nanomaterials exhibit distinctive mechanical and chemical properties, rendering them suitable for various dental applications in endodontics, including obturating materials, sealers, retro-filling agents, and root-repair materials. Certain nanomaterials demonstrate versatile functionalities in endodontics, such as antimicrobial properties that bolster the eradication of bacteria within root canals during endodontic procedures. Moreover, they offer promise in drug delivery, facilitating targeted and controlled release of therapeutic agents to enhance tissue regeneration and repair, which can be used for endodontic tissue repair or regeneration. This review outlines the diverse applications of nanomaterials in endodontics, encompassing endodontic medicaments, irrigants, obturating materials, sealers, retro-filling agents, root-repair materials, as well as pulpal repair and regeneration. The integration of nanomaterials into endodontics stands poised to revolutionize treatment methodologies, presenting substantial potential advancements in the field. Our review aims to provide guidance for the effective translation of nanotechnologies into endodontic practice, serving as an invaluable resource for researchers, clinicians, and professionals in the fields of materials science and dentistry.

Vancomycin Resistance in Enterococcus and Staphylococcus aureus

Enterococcus faecalis, Enterococcus faecium and Staphylococcus aureus are both common commensals and major opportunistic human pathogens. In recent decades, these bacteria have acquired broad resistance to several major classes of antibiotics, including commonly employed glycopeptides. Exemplified by resistance to vancomycin, glycopeptide resistance is mediated through intrinsic gene mutations, and/or transferrable van resistance gene cassette-carrying mobile genetic elements. Here, this review will discuss the epidemiology of vancomycin-resistant Enterococcus and S. aureus in healthcare, community, and agricultural settings, explore vancomycin resistance in the context of van and non-van mediated resistance development and provide insights into alternative therapeutic approaches aimed at treating drug-resistant Enterococcus and S. aureus infections.

Mesoporous Calcium-Silicate Nanoparticles Loaded with Prussian Blue Promotes Enterococcus Faecalis Ferroptosis-Like Death by Regulating Bacterial Redox Pathway ROS/GSH

Background

Mesoporous calcium-silicate nanoparticles (MCSNs) are advanced biomaterials that have been used to control drug delivery for many years. Ultrasmall Prussian blue nanoparticles (UPBNPs) showed high peroxidase and catalase-like activities. This study evaluated the antibacterial and antibiofilm properties, mechanism and cytotoxicity of UPBNPs-MCSNs composites synthesized by both as precursors.

Methods

UPBNPs-MCSNs were prepared and characterized. The antibacterial effect of UPBNPs-MCSNs was evaluated by the MTT assay and CFU counting method, and their biosafety was tested by CCK8. Then explore the antibacterial mechanism, including TEM observation of bacterial morphology, and detection of bacterial ROS, LPO and GSH levels. The antibiofilm activity of UPBNPs-MCSNs was tested by E. faecalis biofilm model in human roots. The roots were pretreated with materials and cultured with E. faecalis, and the survival of E. faecalis on the root canal wall was observed by SEM and CLSM.

Results

The results showed that UPBNPs-MCSNs had potent antibacterial and antibiofilm activities. They can aggregate on the dentin surface and significantly inhibit E. faecalis adhesion and colonization. Their antibacterial activity is as effective as NaClO and calcium hydroxide (CH), can significantly prolong the time of bacterial colonization than CH, but have lower cytotoxicity to normal cells. We found that UPBNPs-MCSNs trigger a like classic ferroptosis pathway in bacteria. UPBNPs-MCSNs can induce bacteria to produce ROS and LPO, and reduce GSH level. Moreover, we observed that the metal ions chelator and the antioxidant could block their antibacterial activity.

Conclusion

These results reveal that UPBNPS-MCSNs have high antibacterial and antibiofilm, and can mediate the bacterial redox pathway ROS/GSH like the classical pathway of ferroptosis, providing a theoretical basis for them to develop into a safe and effective novel root canal disinfectant.

Antibacterial activity of the micro and nanostructures of the optical material tris(8-hydroxyquinoline)aluminum and its application as an antimicrobial coating

Although tris(8-hydroxyquinoline)aluminum (Alq3), a fluorescent optical organometallic material, is known for its applications in optoelectronics, it has only few and limited applications in the biological field. In this study, the antibacterial activity of Alq3 micro and nanostructures was investigated. We prepared Alq3 nanostructures. We prepared nanosized Alq3 as rice-like structures that assembled into flower shapes with an α-crystal phase. Then, Alq3 micro and nanostructure antibacterial activities were estimated against seven human pathogenic bacterial strains. Besides, we compared their antibacterial activities with those of standard antibiotics. The minimal inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and IC50 were evaluated. Alq3 micro and nanostructure antibacterial activity showed considerable values compared to standard antibiotics. Besides, the obtained data revealed that the antibacterial activity of Alq3 in nanostructures with a new morphology is more than that in microstructures. The antibacterial activity of Alq3 nanostructures was attributed to their more surface interactions with the bacterial cell wall. The molecules of 8-hydroxyquinoline in the Alq3 structure could play crucial roles in its antibacterial activity. To apply the achieved results, Alq3 was incorporated with polystyrene (PS) in a ratio of 2% to fabricate a PS/Alq3 composite and used to coat glass beakers, which showed inhibition in the bacterial growth reduced to 65% compared with non-coated beakers. The finding of this study showed that Alq3 could be used as a promising antimicrobial coating.

A Self-Supplying H2O2 Modified Nanozyme-Loaded Hydrogel for Root Canal Biofilm Eradication

The success of root canal therapy depends mainly on the complete elimination of the root canal bacterial biofilm. The validity and biocompatibility of root canal disinfectant materials are imperative for the success of root canal treatment. However, the insufficiency of the currently available root canal disinfectant materials highlights that more advanced materials are still needed. In this study, a nanozyme-loaded hydrogel (Fe3O4-CaO2-Hydrogel) was modified and analyzed as a root canal disinfectant material. Fe3O4-CaO2-Hydrogel was fabricated and examined for its release profile, biocompatibility, and antibacterial activity against E. faecalis and S. sanguis biofilms in vitro. Furthermore, its efficiency in eliminating the root canal bacterial biofilm removal in SD rat teeth was also evaluated. The results in vitro showed that Fe3O4-CaO2-Hydrogel could release reactive oxygen species (ROS). Moreover, it showed good biocompatibility, disrupting bacterial cell membranes, and inhibiting exopolysaccharide production (p < 0.0001). In addition, in vivo results showed that Fe3O4-CaO2-Hydrogel strongly scavenged on root canal biofilm infection and prevented further inflammation expansion (p < 0.05). Altogether, suggesting that Fe3O4-CaO2-Hydrogel can be used as a new effective biocompatible root canal disinfectant material. Our research provides a broad prospect for clinical root canal disinfection, even extended to other refractory infections in deep sites.

Mesoporous Calcium-Silicate Nanoparticles Loaded with Low-Dose Triton-100+Ag+ to Achieve Both Enhanced Antibacterial Properties and Low Cytotoxicity for Dentin Disinfection of Human Teeth

Mesoporous calcium-silicate nanoparticles (MCSNs) are excellent biomaterials for controlled drug delivery and mineralization induction. In this study, MCSNs were loaded with low-dose silver ion (Ag⁺) and Triton X-100 (TX-100) as the M-AgTX to achieve both enhanced antibacterial properties and low cytotoxicity for dentin disinfection. The physicochemical property, biocompatibility, infiltration ability into dentinal tubules, anti-bacterial ability against both planktonic Enterococcusfaecalis (E. faecalis) and its biofilm on dentin, effects on dentin microhardness and in vitro mineralization property were systematically investigated. Results confirmed that the MCSNs and M-AgTX nanoparticles showed typical morphology of mesoporous materials and exhibited sustained release of chemicals with an alkaline pH value over time. M-AgTX also exhibited excellent biocompatibility on MC3T3-E1 cells and could eliminate 100% planktonic E. faecalis after 48-h treatment. On dentin slices, it could enter dentinal tubules by ultrasonic activation and inhibit the growth of E. faecalis on dentin. M-AgTX could completely inactive 28-day E. faecalis biofilm. TEM confirmed the destruction of cell membrane integrity and Ag⁺ infiltration into bacteria by M-AgTX. Besides, dentin slices medicated with M-AgTX nanoparticles displayed an increased microhardness. After being immersed in SBF for 7 days, apatite crystals could be observed on the surface of the material tablets. M-AgTX could be developed into a new multifunctional intra-canal medication or bone defect filling material for infected bone defects due to its sustained release profile, low cytotoxicity, infiltration ability, enhanced anti-bacterial and mineralization features.