Rapid Antibiofilm Effect of Ag/ZnO Nanocomposites Assisted by Dental LED Curing Light against Facultative Anaerobic Oral Pathogen Streptococcus mutans

Synergistic antibacterial effect and mechanism between Cu2O nanoparticles and quaternary ammonium salt in moisture-curable acrylic coatings

Combining with various antibacterial mechanisms is the preferred strategy to fabricate coatings with effective antibacterial performance. Herein, Cu2O nanoparticles and dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride, a kind of quaternary ammonium salt (QAS), were simultaneously incorporated into a moisture-curable acrylic resin in order to achieve both contact-killing and release-killing abilities for antibacterial coatings. The surface morphology, surface composition and basic properties of the coatings were thoroughly characterized. The antibacterial performance of the coatings was determined by in-vitro bacteriostatic test. Under the constant total mass fraction of antibacterial agents, both Cu2O and QAS content possessed the highest value on the coating surface at Cu2O/QAS mass ratio of 1:1, and correspondingly, the coatings reached sterilizing rate above 99 % against both E. coli and S. loihica, indicating the existence of synergistic effect between Cu2O and QAS. The synergistic antibacterial mechanism of the coatings involved two aspects. Firstly, the combination of contact-killing and release-killing biocides resulted in high bactericidal and antibiofilm activity against different bacteria. Further, the grafting of QAS molecules on the surface of Cu2O particles brought about the spontaneous migration of nanoparticles to the coating surface. The interaction between Cu2O and QAS also inhibited the phase separation of QAS and prolonged the release of Cu2+ at the same time. The coatings, therefore, exhibited stable antibacterial performance at varied service conditions.

Recent updates and feasibility of nanodrugs in the prevention and eradication of dental biofilm and its associated pathogens-A review

OBJECTIVES

Dental biofilm is one of the most prevalent diseases in humans, which is mediated by multiple microorganisms. Globally, half of the human population suffers from dental biofilm and its associated diseases. In recent trends, nano-formulated drugs are highly attractive in the treatment of dental biofilms. However, the impact of different types of nanodrugs on the dental biofilm and its associated pathogens have not been published till date. Thus, this review focuses on the recent updates, feasibility, mechanisms, limitations, and regulations of nanodrugs applications in the prevention and eradication of dental biofilm.

STUDY SELECTION, DATA AND SOURCES

A systematic search was conducted in PubMed/Google Scholar/Scopus over the past five years covering the major keywords "nanodrugs, metallic nanoparticles, metal oxide nanoparticles, natural polymers, synthetic polymers, biomaterials, dental biofilm, antibiofilm mechanism, dental pathogens", are reviewed in this study. Nearly, 100 scientific articles are selected in this relevant topic published between 2019 and 2023. Data from the selected studies dealing with nanodrugs used for biofilm treatment was qualitatively analyzed.

CONCLUSIONS

The nanodrugs such as silver nanoparticles, gold nanoparticles, selenium nanoparticles, zinc oxide nanoparticles, copper oxide nanoparticles, titanium oxide nanoparticles, hydroxyapatite nanoparticles and these inorganic nanoparticles incorporated polymer-based nanocomposites, organic/inorganic nanoparticles mediated antimicrobial photodynamic therapy exhibits an excellent antibacterial and antibiofilm activity towards dental pathogens. Finally, this review highlights that bioinspired nanodrugs will be very useful to control the dental biofilm and its associated diseases.

CLINICAL SIGNIFICANCE

Microbial influence on the oral environment is unavoidable; therefore, curing such dental biofilms and pathogens is essential for the impactful reflection of applying biocompatible treatments. In this direction, the current review explains the demand for the nanodrug in inhibiting biofilms for the effective exploration of employing treatments.

Visible light-activated curcumin-doped zinc oxide nanoparticles integrated into orthodontic adhesive on Micro-tensile bond strength, degree of conversion, and antibacterial effectiveness against Staphylococcus Aureus. An investigation using scanning electron microscopy and energy-dispersive X-ray spectroscopy

AIM

To acquire a thorough comprehension of the photoactivated Cur-doped ZnONPs at different concentrations 0%, 2.5%, and 5% on the physical qualities, antibacterial efficacy, degree of conversion, and μshear bond strength between orthodontic brackets and the enamel surface.

MATERIAL AND METHODS

An extensive investigation was carried out utilizing a range of analytical methods, scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy, micro tensile bond strength (μTBS) testing, and evaluation of antibacterial effectiveness. Cur-doped ZnONPs at concentrations of 2.5% and 5% were blended with Transbond XT, a light-curable orthodontic adhesive. A control group without the addition of Cur-doped ZnONPs was also prepared. The tooth samples were categorized into three groups based on the weight percentage of NPs: Group 1 (control) with 0% Cur-doped ZnONPs, Group 2 with 2.5 wt% Cur-doped ZnONPs, and Group 3 with 5 wt% Cur-doped ZnONPs. The SEM technique was employed to analyze the morphological characteristics of Cur-doped ZnONPs and ZnONPs. The composition and elemental distribution of the modified Cur-doped ZnONPs were assessed using energy-dispersive X-ray spectroscopy. The effectiveness of NPs at various concentrations against S.Mutans was gauged through the pour plate method. DC of Cur-doped ZnONPs at a region of 1608 cm-1 to 1636 cm-1 for the cured area, whereas the uncured area spanned the same range of 1608 cm-1 to 1636 cm-1 was assessed. The Adhesive Remnant Index (ARI) approach was utilized to investigate the bond failure of orthodontic brackets, while a Universal Testing Machine (UTM) was utilized to test μTBS. The Kruskal-Wallis test was employed to investigate variations in S.mutans survival rates. To determine the μTBS values, analysis of variance (ANOVA) and the post hoc Tukey multiple comparisons test were used.

RESULTS

The maximum μTBS was given and documented in group 3: 5 wt% Cur-doped ZnONPs (21.21 ± 1.53 MPa). The lowest μTBS was given in group 2: 2.5 wt% Cur-doped ZnONPs (19.58 ± 1.27 MPa). The highest efficacy against S.mutans was documented in group 3 in which 5 wt% Cur-doped ZnONPs (0.39 ± 0.15). The lowest efficacy was seen in group 1 in which no Cur-doped ZnONPs were used (6.47 ± 1.23). The ARI analysis indicated that the predominant failure was between scores 0 and 1 among all experimental groups. Control group 1 which was not modified showed the highest DC (73.11 ± 4.19).

CONCLUSION

Orthodontic adhesive, containing 5% Cur-doped ZnONPs photoactivated with visible light exhibited a favorable impact on μTBS and indicated enhanced antibacterial efficacy against S.mutans. Nevertheless, it was observed that the addition of Cur-doped ZnONPs at different concentrations (2.5%,5%) resulted in a decrease in the monomer-to-polymer ratio compromising DC.

Morinda citrifolia leaf assisted synthesis of ZnO decorated Ag bio-nanocomposites for in-vitro cytotoxicity, antimicrobial and anticancer applications

This study used Morinda citrifolia leaf (MCL) extract to synthesise Zinc oxide nanoparticles (ZnO NPs) and ZnO decorated silver nanocomposites (ZnO/Ag NCs). The synthesized nanomaterials structural morphology and crystallinity were characterized using a Field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) analysis. The antimicrobial activity of ZnO NPs and ZnO/Ag NCs was evaluated using human nosocomial bacterial pathogens. The highest antimicrobial activity was recorded for ZnO/Ag NCs at the minimum inhibitory concentration (MIC) at 80 and 100 μg/mL for Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis, Staphylococcus aureus than ZnO NPs at the MIC of 120 and 140 μg/mL for Bacillus subtilis and Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus. Furthermore, ROS detection, viability assay and bacterial membrane integrity analysis of ZnO/Ag NCs treated P. aeruginosa and S. aureus revealed the fundamental bactericidal mechanism involving cell wall, cell membrane interaction and release of cytoplasmic contents. In addition, ZnO/Ag NCs and ZnO NPs showed higher toxicity towards A549 lung cancer cells than the non-cancerous RAW264 macrophage cells, with IC50 of 242 and 398 µg/mL respectively, compared to IC50 of 402 and 494 µg/mL for the macrophage cells. These results suggest that the ZnO/Ag NCs can be effectively used to develop antimicrobial and anticancer materials.

Recent advances in the use of inorganic nanomaterials as anti caries agents

Caries is the most prevalent and widespread chronic oral disease. Traditional caries filling materials, due to their lack of anti-caries capabilities, can readily develop secondary caries. Nanomaterials proposed as an effective approach for caries treatment can inhibit biofilm formation. It also can not only reduce demineralization but also promote remineralization. In recent years, nanotechnology in anti-caries materials, particularly nano-adhesive and nano-composite resin, has advanced rapidly. Because inorganic nanoparticles (NPs) interfere with bacterial metabolism and inhibit biofilm development, inorganic NPs have emerged as a new trend in dental applications. Metal and metal oxide NPs by releasing metal ions, oxidative stress induction, and non-oxidative mechanisms showed significant antimicrobial activity. For applying metal and metal oxide NPs as anti caries agents, silver, zinc, titanium, copper, and calcium ions have been shown significant attention. Moreover, fluoride functionalized inorganic NPs were also employed to improve their efficacy of them. The fluoride-functionalized NPs can promote remineralization, and inhibit demineralization by enhancing apatite formation. In this review, we have provided an overview and recent advances in the use of inorganic NPs as anti caries agents. Furthermore, their antimicrobial, remineralizing, and mechanical impacts on dental materials were discussed.

Synergistic antibacterial and biofilm eradication activity of quaternary-ammonium compound with copper ion

Antibiotics overuse and misuse increase the emergence of multidrug-resistant bacterial strains, which often leads to the failure of conventional antibiotic therapies. Even worse, the tendency of bacteria to form biofilms further increases the therapeutic difficulty, because the extracellular matrix prevents the penetration of antibiotics and triggers bacterial tolerance. Therefore, developing novel antibacterial agents or therapeutic strategies with diverse antibacterial mechanisms and destruction of bacteria biofilm is a promising way to combat bacterial infections. In the present study, the combination of quaternary ammonium compound poly(diallyl dimethyl ammonium chloride) (PDDA) with Cu²⁺ was screened out to fight common pathogenic Staphylococcus aureus (S. aureus) through multi-mechanisms. This combination appeared strong synergistic antibacterial activity, and the fractional inhibitory concentration index was as low as 0.032. The synergistic antibacterial mechanism involved the destruction of the membrane function, generation of intracellular reactive oxygen, and promotion more Cu²⁺ into the cytoplasm. Further, the combination of PDDA and Cu²⁺ reduced the extracellular polysaccharide matrix, meanwhile killing the bacteria embedded in the biofilm. The biocompatibility study in vitro revealed this combination exhibited low cytotoxicity and hemolysis ratio even at 8 times of minimum bactericidal concentration. This work provides a novel antibacterial agents combination with higher efficiency to fight planktonic and biofilm conditions of S. aureus.

Photodynamic nano hydroxyapatite with biofilm penetration capability for dental plaque eradication and prevention of demineralization

Dental caries represents one of the most prevalent diseases worldwide, characteristic of the growth of dental plaque and demineralization of tooth enamel. Current medications for eradication of dental plaques and prevention of demineralization suffer from several limitations to overcome, calling for novel strategies with great potency in eliminating cariogenic bacteria and dental plaque that forms, as well as in inhibiting the demineralization of enamel, into an integrated system. Considering the potency of photodynamic therapy in bacteria inactivation and the composition of enamel, we herein report that the novel photodynamic nano hydroxyapatite (nHAP), named Ce6 @QCS/nHAP, was useful for this purpose. Ce6 @QCS/nHAP, comprised of quaternary chitosan (QCS)-coated nHAP loaded with chlorin e6 (Ce6), exhibited good biocompatibility and non-compromised photodynamic activity. In vitro studies revealed that Ce6 @QCS/nHAP could effectively associate with cariogenic Streptococcus mutans (S. mutans), leading to a significant antibacterial effect through photodynamic killing and physical inactivation against the planktonic microbe. Three-dimensional fluorescence imaging suggested that Ce6 @QCS/nHAP exhibited a superior S. mutans biofilm penetration capacity to free Ce6, resulting in effective dental plaque eradiation when light irradiation was applied. The number of surviving bacteria in biofilm was at least 2.8 log units lower in the Ce6 @QCS/nHAP group compared to that in the free Ce6 group. Further, in the S. mutans biofilm-infected artificial tooth model, treatment with Ce6 @QCS/nHAP also resulted in the significant prevention of hydroxyapatite disks from demineralization, with lower percentage of fragmentation and weight loss These data suggest that our photodynamic nanosystem can effectively eradicate dental plaque while also significantly protecting artificial tooth from demineralization, opening up new possibilities in treating bacterium-associated dental caries.

Trichoderma-Mediated ZnO Nanoparticles and Their Antibiofilm and Antibacterial Activities

Antimicrobial resistance is a major global health concern and one of the gravest challenges to humanity today. Antibiotic resistance has been acquired by certain bacterial strains. As a result, new antibacterial drugs are urgently required to combat resistant microorganisms. Species of Trichoderma are known to produce a wide range of enzymes and secondary metabolites that can be exploited for the synthesis of nanoparticles. In the present study, Trichoderma asperellum was isolated from rhizosphere soil and used for the biosynthesis of ZnO NPs. To examine the antibacterial activity of ZnO NPs against human pathogens, Escherichia coli and Staphylococcus aureus were used. The obtained antibacterial results show that the biosynthesized ZnO NPs were efficient antibacterial agents against the pathogens E. coli and S. aureus, with an inhibition zone of 3-9 mm. The ZnO NPs were also effective in the prevention of S. aureus biofilm formation and adherence. The current work shows that the MIC dosages of ZnO NPs (25, 50, and 75 μg/mL) have effective antibacterial activity and antibiofilm action against S. aureus. As a result, ZnO NPs can be used as a part of combination therapy for drug-resistant S. aureus infections, where biofilm development is critical for disease progression.

Exploring the Physicochemical, Mechanical, and Photocatalytic Antibacterial Properties of a Methacrylate-Based Dental Material Loaded with ZnO Nanoparticles

While resin-based materials meet the many requirements of a restorative material, they lack adequate, long-lasting antimicrobial power. This study investigated a zinc oxide nanoparticle (ZnO NP)-loaded resin-blend (RB) toward a new antimicrobial photodynamic therapy (aPDT)-based approach for managing dental caries. The results confirmed that up to 20 wt% ZnO NPs could be added without compromising the degree of conversion (DC) of the original blend. The DC achieved for the 20 wt% ZnO NP blend has been the highest reported. The effects on flexural strength (FS), shear bond strength to dentin (SBS), water sorption (WS), solubility (SL), and viability of Streptococcus mutans under 1.35 J/cm² blue light or dark conditions were limited to ≤20 wt% ZnO NP loading. The addition of up to 20 wt% ZnO NPs had a minimal impact on FS or SBS, while a reduction in the bacteria count was observed. The maximum loading resulted in an increase in SL. Furthermore, 28-day aging in 37 °C water increased the FS for all groups, while it sustained the reduction in bacteria count for the 20 wt% resin blends. Overall, the ZnO NP-loaded resin-based restorative material presents significant potential for use in aPDT.

Nanomaterials enabling clinical translation of antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy (aPDT) has emerged as a promising approach to aid the fight against looming antibiotic resistance. aPDT harnesses the energy of light through photosenstizers to generate highly reactive oxygen species that can inactivate bacteria and fungi with no resistance. To date aPDT has shown great efficacy against microbes causing localized infections in the skin and the oral cavity. However, its wide application in clinical settings has been limited due to both physicochemical and biological challenges. Over the past decade nanomaterials have contributed to promoting photosensitizer performance and aPDT efficiency, yet further developments are required to establish accredited treatment options. In this review we discuss the challenges facing the clinical application of aPDT and the opportunities that nanotechnology may offer to promote the safety and efficiency of aPDT.

Te-Cefotaxime Nanocomposites with Restored Antibiotic Susceptibility and LED Light Activated Photothermal Effect for Rapid MRSA Eradication

The ever-growing antibiotic-resistant bacteria pose a huge threat to public health. Restoring the susceptibility of ineffective antibiotics by inorganic nanomaterials and combining of photothermal and antibiotic synergistic therapy could be...

Bionanocomposites in caries prevention and treatment: A systematic review

Objective:

The aim of this systematic review was to assess the therapeutic effect of remineralizing and antibacterial potential of resin-based nanocomposites compared with conventional composite with/without fluoride release in naturally occurring and post-orthodontic carious lesions.

Data Sources:

The literature search covered the electronic databases, such as PubMed, EBSCO, and Google scholar, from 2012 to 2021. Only articles published in English were included. Randomized controlled trials (RCT) and in-vitro studies were included. All studies which met eligibility criteria were reviewed by two independent reviewers.

Study Selection:

The processes involved in the selection of studies were presented in Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines for study screening. Finally, based on the eligibility criteria, 13 studies were selected. The remineralizing effects of nanocomposites were compared with conventional composites in clinical trials and in-vitro studies.

Conclusion:

Nanotechnological interventions could be used to improve the therapeutic efficiency in reducing demineralization and growth of the biofilm. Further well-designed clinical trials with long-term follow-up are essential to elucidate the clinical relevance of remineralizing agents.

Proteomics of Streptococcus mutans to Reveal the Antibiofilm Formation Mechanism of Ag/ZnO Nanocomposites with Light-Emitting Diode Radiation

Introduction

As a biofilm-associated disease, dental caries benefits from nanoparticle (NP)-based therapies. Streptococcus mutans (S. mutans) is a primary aetiologic agent for dental caries development. We successfully applied a synergistic therapy of Ag/ZnO nanocomposites combined with light-emitting diode (LED) radiation to inhibit S. mutans biofilms. However, the antibiofilm mechanism has not been fully elucidated, and little is known about the biofilm formation ability of bacteria that survive NP-based therapies.

Methods

This study explored the antibiofilm formation mechanism of this synergistic therapy by an integrated approach based upon proteomics.

Results

Synergistic therapy killed 99.8% of bacteria, while the biofilm formation ability of 0.2% surviving bacteria was inhibited. The proteomic responses of S. mutans to synergistic therapy were comprehensively characterized to unveil the mechanism of bacterial death and biofilm formation inhibition of the surviving bacteria. In total, 55 differentially expressed proteins (12 upregulated and 43 downregulated) were recorded. The bioinformatic analysis demonstrated that cellular integrity damage and regulated expression of structure-associated proteins were the main reasons for bacterial death. In addition, the proteomic study indicated the potential inhibition of metabolism in surviving bacteria and provided a biofilm-related network consisting of 17 differentially expressed proteins, explaining the multiantibiofilm formation actions. Finally, we reported and verified the inhibitory effects of synergistic therapy on sucrose metabolism and D-alanine metabolism, which disturbed the biofilm formation of surviving bacteria.

Conclusion

Our findings demonstrated that synergistic therapy killed most bacteria and inhibited the surviving bacteria from forming biofilms. Furthermore, the antibiofilm formation mechanism was revealed by proteomics analysis of S. mutans after synergistic therapy and subsequent metabolic studies. Our success may provide a showcase to explore the antibiofilm formation mechanism of NP-based therapies using proteomic studies.

Study of Titanium-Silver Monolayer and Multilayer Films for Protective Applications in Biomedical Devices

The search for coatings that extend the useful life of biomedical devices has been of great interest, and titanium has been of great relevance due to its innocuousness and low reactivity. This study contributes to the investigation of Ti/Ag films in different configurations (monolayer and multilayer) deposited by magnetron sputtering. The sessile droplet technique was applied to study wettability; greater film penetrability was obtained when Ag is the external layer, conferring high efficiency in cell adhesion. The morphological properties were characterized by SEM, which showed porous nuclei on the surface in the Ag coating and crystals embedded in the Ti film. The structural properties were studied by XRD, revealing the presence of TiO2 in the anatase crystalline phase in a proportion of 49.9% and the formation of a silver cubic network centered on the faces. Tafel polarization curves demonstrated improvements in the corrosion current densities of Ag/Ti/Ag/Ti/Ag/Ti/Ag/Ti and Ti/Ag compared to the Ag coating, with values of 0.1749, 0.4802, and 2.044 nA.m-2, respectively. Antimicrobial activity was evaluated against the bacteria Pseudomonas aeruginosa and Bacillus subtilis and the yeasts Candida krusei and Candida albicans, revealing that the Ti/Ag and Ag/Ti/Ag/Ti/Ag/Ti/Ag/Ti coatings exhibit promise in biomedical material applications.

Antibacterial Photodynamic Inactivation of Fagopyrin F from Tartary Buckwheat (Fagopyrum tataricum) Flower against Streptococcus mutans and Its Biofilm

The objective of this study was to determine reactive oxygen species (ROS) produced by fagopyrin F-rich fraction (FFF) separated from Tartary buckwheat flower extract exposed to lights and to investigate its antibacterial photodynamic inactivation (PDI) against Streptococcus mutans and its biofilm. ROS producing mechanisms involving FFF with light exposure were determined using a spectrophotometer and a fluorometer. S. mutans and its biofilm inactivation after PDI treatment of FFF using blue light (BL; 450 nm) were determined by plate count method and crystal violet assay, respectively. The biofilm destruction by ROS produced from FFF after exposure to BL was visualized using confocal laser scanning microscopy (CLSM) and field emission scanning electron microscope (FE-SEM). BL among 3 light sources produced type 1 ROS the most when applying FFF as a photosensitizer. FFF exposed to BL (5 and 10 J/cm2) significantly more inhibited S. mutans viability and biofilm formation than FFF without the light exposure (p < 0.05). In the PDI of FFF exposed to BL (10 J/cm2), an apparent destruction of S. mutans and its biofilm were observed by the CLSM and FE-SEM. Antibacterial PDI effect of FFF was determined for the first time in this study.

Shining light on transition metal sulfides: New choices as highly efficient antibacterial agents

Globally, millions of people die of microbial infection-related diseases every year. The more terrible situation is that due to the overuse of antibiotics, especially in developing countries, people are struggling to fight with the bacteria variation. The emergence of super-bacteria will be an intractable environmental and health hazard in the future unless novel bactericidal weapons are mounted. Consequently, it is critical to develop viable antibacterial approaches to sustain the prosperous development of human society. Recent researches indicate that transition metal sulfides (TMSs) represent prominent bactericidal application potential owing to the meritorious antibacterial performance, acceptable biocompatibility, high solar energy utilization efficiency, and excellent photo-to-thermal conversion characteristics, and thus, a comprehensive review on the recent advances in this area would be beneficial for the future development. In this review article, we start with the antibacterial mechanisms of TMSs to provide a preliminary understanding. Thereafter, the state-of-the-art research progresses on the strategies for TMSs materials engineering so as to promote their antibacterial properties are systematically surveyed and summarized, followed by a summary of the practical application scenarios of TMSs-based antibacterial platforms. Finally, based on the thorough survey and analysis, we emphasize the challenges and future development trends in this area.

Selective Inhibition of Streptococci Biofilm Growth via a Hydroxylated Azobenzene Coating

Strategies to engineer surfaces that can enable the selective inhibition of bacterial pathogens while preserving beneficial microbes can serve as tools to precisely edit the microbiome. In the oral microbiome, this selectivity is crucial in preventing the proliferation of cariogenic species such as Streptococcus mutans (S. mutans). In this communication, coatings consisting of a covalently tethered hydroxylated azobenzene (OH-AAZO) on glassy acrylic resins are studied and characterized for their ability to selectively prevent the attachment and growth of oral Streptococci biofilms. The coating applied on the surface of glassy resins inhibits the growth and proliferation of cariogenic S. mutans and S. oralis biofilms while A. actinomycetemcomitans, S. aureus, and E. coli biofilms are unaffected by the coating . The antibacterial effect is characterized as a function of both the OH-AAZO concentration in the coatings (≥50 mg mL-1) and the structure of the monomer in the coating. Preliminary mechanistic results suggest that the targeted bactericidal effect against Streptococci species is caused by a disruption of membrane ion potential, inducing cell death.

Antibacterial Properties of Bilayer Biomimetic Nano-ZnO for Dental Implants

Dental implant surgery has a relatively high incidence of peri-implantitis. In this research, ZnO nanorods and ZnO nanospheres were synthesized by a hydrothermal method. ZnO nanorods first covered the surface of Ti or Ti-Zr, and ZnO nanospheres were then modified as the outermost layer. By these means a dual antibacterial effect could be realized by the rapid release of ZnO nanospheres and the sustained release of ZnO nanorods. Subsequent studies implied that this ZnO nanorods-nanospheres hierarchical structure (NRS) could be stably loaded on the surface of roughened Ti and Ti-Zr slices. The modified materials not only showed excellent antibacterial activities against both Escherichia coli and Staphylococcus aureus but also showed low cellular cytotoxicity. This ZnO NRS structure is thus expected to be used as a general antimicrobial coating on the surface of Ti (Ti-Zr) in dental implant surgery.

Effects of Ag/ZnO nanocomposite at sub-minimum inhibitory concentrations on virulence factors of Streptococcus mutans

OBJECTIVE

Streptococcus mutans (S. mutans), the main pathogen of dental caries, could be well killed by Ag/ZnO nanocomposite. However, effects on virulence factors remain to be elucidated. This study investigated effects of Ag/ZnO at sub-minimum inhibitory concentrations (sub-MICs) on virulence factors of S. mutans and related genes expressions.

DESIGN

Effects of Ag/ZnO on the growth of S. mutans was investigated by growth curves and MTT staining method. The influence of Ag/ZnO at sub-MICs on biofilm formation was measured by the crystal violet staining method and observed by a scanning electron microscopy. Adherence, cell-surface hydrophobicity, acidogenicity and extracellular polysaccharides (EPS) of S. mutans after treatment by Ag/ZnO at sub-MICs were also investigated. Virulence factors related genes expressions after treated by Ag/ZnO at 1/2 MIC was conducted by the quantitative real-time PCR (qRT-PCR) method.

RESULTS

Sub-MICs of Ag/ZnO exhibited a dose-dependent inhibition on the virulence factors of S. mutans. Specially, Ag/ZnO at 1/2 MIC decreased 69.00 % biofilm formation, 31.78 % sucrose-independent and 48.08 % sucrose-dependent adherence, 69.44 % cell-surface hydrophobicity and 72.45 % water-soluble and 90.60 % water-insoluble EPS. Furthermore, the expression of virulence factors related genes was significantly suppressed by Ag/ZnO at 1/2 MIC.

CONCLUSIONS

Ag/ZnO at sub-MICs inhibited multiple virulence factors of S. mutans through downregulating the related genes. Ag/ZnO nanocomposite could be used for prevention of dental caries at low dosage.

Antibacterial, Antibiofilm, Antiquorum Sensing, Antimotility, and Antioxidant Activities of Green Fabricated Ag, Cu, TiO2, ZnO, and Fe3O4 NPs via Protoparmeliopsis muralis Lichen Aqueous Extract against Multi-Drug-Resistant Bacteria

Consideration of lichen organisms as the ecofriendly source of metal nanoparticles (MNPs) and metal oxide NPs (MONPs) synthesis is seldom. In this study, Ag and Cu MNPs as well as TiO₂, ZnO, and Fe₃O₄ MONPs were green synthesized by Protoparmeliopsis muralis lichen aqueous extract. First, physicochemical characterization by UV-vis spectroscopy, XRD, FT-IR, FESEM, and TEM techniques demonstrated the presence possibility of secondary metabolites around formed MNPs/MONPs with different diameters and shapes (spherical, triangular, polyhedral, and cubic). The antibacterial, antibiofilm, antiquorum sensing, and antioxidant abilities of these MNPs/MONPs against multi drug resistant (MDR) bacterium (Staphylococcus aureus ATCC 43300) and reference bacteria (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853) were then evaluated by in vitro tests. Results of disc diffusion and MIC/MBC assays of Ag NPs as an effective antibacterial agent illustrated a higher sensitivity of the P. aeruginosa pathogen than E. coli and S. aureus. In next steps, a significant reduction was observed in the biofilm formation of each bacterium and pyocyanin synthesis by P. aeruginosa under Ag NPs. This investigation presents novel clean production of five MNPs/MONPs with prominent advantages of being ecofriendly and cost-effective and having antipathogen properties.