Biosynthesis, Characterization and Antibacterial Efficacy of Silver Nanoparticles Derived from Endophytic Fungi against P. gingivalis

Preparation and antibacterial evaluation of silver-doped zirconia for enhanced dental restoration performance

Because of its superior strength, esthetic properties, and excellent biocompatibility, zirconia is preferred for dental prosthetic such as crowns and bridges. However, zirconia crowns and bridges are susceptible to secondary caries owing to margin leakage. Silver is a well-known antibacterial agent, making it a desirable additive to zirconia crowns and bridges for secondary caries prevention. This study focuses on imparting zirconia composite with antibacterial properties to enhance its protective capacity in dental restorations. We used the sol-gel method to dope Ag into zirconia. Silver-doped zirconia powders were prepared at Zr:Ag molar ratios of 100:0,100:0.1, 100:0.5, 100:1, 100:3, and 100:5 (respective samples denoted as Ag-0, Ag-0.1, Ag-0.5, Ag-1, Ag-3, and Ag-5) and were subjected to firing at various temperatures (400 °C-1000 °C). We performed x-ray diffraction to investigate the crystal phase of these powders and x-ray fluorescence and field emission scanning electron microscopy to analyze their elemental composition and surface morphology, respectively. Moreover, we performed spectrophotometry to determine theL*a*b* color values, conducted dissolution tests, and quantified the Ag content through inductively coupled plasma optical emission spectroscopy. In addition, we studied the antibacterial activity of the samples. Analyses of the samples fired at ⩽600 °C revealed a predominantly white to grayish-white coloration and a tetragonal crystal phase. Firing at ⩾700 °C resulted in gray or dark gray coloration and a monoclinic crystal phase. The Ag content decreased after firing at 900 °C or 1000 °C. Ag-0.5 and above exhibited antibacterial activity against bothEscherichia coliandStaphylococcus aureus. Therefore, the minimum effective silver-doped zirconia sample was found to be Ag-0.5. This study allows the exploration of the antimicrobial potential of silver-doped zirconia materials in dental applications such as prosthdontical lining materials, promoting the development of innovative restorations with protective capacity against secondary caries.

Nanotechnology in tissue engineering: expanding possibilities with nanoparticles

Tissue engineering is a multidisciplinary field that merges engineering, material science, and medical biology in order to develop biological alternatives for repairing, replacing, maintaining, or boosting the functionality of tissues and organs. The ultimate goal of tissue engineering is to create biological alternatives for repairing, replacing, maintaining, or enhancing the functionality of tissues and organs. However, the current landscape of tissue engineering techniques presents several challenges, including a lack of suitable biomaterials, inadequate cell proliferation, limited methodologies for replicating desired physiological structures, and the unstable and insufficient production of growth factors, which are essential for facilitating cell communication and the appropriate cellular responses. Despite these challenges, there has been significant progress made in tissue engineering techniques in recent years. Nanoparticles hold a major role within the realm of nanotechnology due to their unique qualities that change with size. These particles, which provide potential solutions to the issues that are met in tissue engineering, have helped propel nanotechnology to its current state of prominence. Despite substantial breakthroughs in the utilization of nanoparticles over the past two decades, the full range of their potential in addressing the difficulties within tissue engineering remains largely untapped. This is due to the fact that these advancements have occurred in relatively isolated pockets. In the realm of tissue engineering, the purpose of this research is to conduct an in-depth investigation of the several ways in which various types of nanoparticles might be put to use. In addition to this, it sheds light on the challenges that need to be conquered in order to unlock the maximum potential of nanotechnology in this area.

Metal-Based Nanoparticles: Antibacterial Mechanisms and Biomedical Application

The growing increase in antibiotic-resistant bacteria has led to the search for new antibacterial agents capable of overcoming the resistance problem. In recent years, nanoparticles (NPs) have been increasingly used to target bacteria as an alternative to antibiotics. The most promising nanomaterials for biomedical applications are metal and metal oxide NPs, due to their intrinsic antibacterial activity. Although NPs show interesting antibacterial properties, the mechanisms underlying their action are still poorly understood, limiting their use in clinical applications. In this review, an overview of the mechanisms underlying the antibacterial activity of metal and metal oxide NPs will be provided, relating their efficacy to: (i) bacterial strain; (ii) higher microbial organizations (biofilm); (iii) and physico-chemical properties of NPs. In addition, bacterial resistance strategies will be also discussed to better evaluate the feasibility of the different treatments adopted in the clinical safety fields. Finally, a wide analysis on recent biomedical applications of metal and metal oxide NPs with antibacterial activity will be provided.

Antimicrobial Effect of Moringa Oleifera L. and Red Pomegranate against Clinically Isolated Porphyromonas gingivalis: in vitro Study

Moringa oleifera L. and red pomegranate extracts have been reported to inhibit gram-positive facultative anaerobe growth and inhibit the formation of biofilm on tooth surfaces. The current study aimed to assess the antibacterial effect of M. oleifera L. and red pomegranate extracts and their combinations against Porphyromonas gingivalis. The antimicrobial sensitivity, minimum inhibition concentrations (MIC), and minimum bactericidal concentrations after treatment with the aqueous extracts of M. oleifera L. and red pomegranate as well as their combination against clinically isolated P. gingivalis were determined using agar well diffusion and two-fold serial dilution. The anti-biofilm activity of the extracts and their combination was evaluated using the tube adhesion method. The phytochemical analysis was carried out using gas chromatography-mass spectrometry. It was found that P. gingivalis was sensitive to aqueous extract of M. oleifera L. seeds and red pomegranate albedo, however, not to M. oleifera L. leaves and red pomegranate seeds. The MIC value of M. oleifera L. seeds, red pomegranate albedo, and their combination were obtained at 12.5 mg/ml, 6.25 mg/ml, and 3.12 mg/ml against P. gingivalis, respectively. The extract combination had the highest anti-biofilm effect than M. oleifera L. seeds and red pomegranate albedo aqueous extracts at the minimum concentrations of 6.25 mg/ml, 25 mg/ml, and 12.5 mg/ml, respectively. The combination of red pomegranate albedo and M. oleifera L. seeds showed superior antibacterial and anti-biofilm effects against P. gingivalis, followed by red pomegranate albedo and M. oleifera L. seeds. This may highlight a promising alternative to the traditional chemicals that can be used as an adjunct in the treatment of periodontal diseases.

Glutathione-Stabilized Silver Nanoparticles: Antibacterial Activity against Periodontal Bacteria, and Cytotoxicity and Inflammatory Response in Oral Cells

Silver nanoparticles (AgNPs) have been proposed as new alternatives to limit bacterial dental plaque because of their antimicrobial activity. Novel glutathione-stabilized silver nanoparticles (GSH-AgNPs) have proven powerful antibacterial properties in food manufacturing processes. Therefore, this study aimed to evaluate the potentiality of GSH-AgNPs for the prevention/treatment of oral infectious diseases. First, the antimicrobial activity of GSH-AgNPs against three oral pathogens (Porphyromonas gingivalis, Fusobacterium nucleatum, and Streptococcus mutans) was evaluated. Results demonstrated the efficiency of GSH-AgNPs in inhibiting the growth of all bacteria, especially S. mutans (IC50 = 23.64 μg/mL, Ag concentration). Second, GSH-AgNPs were assayed for their cytotoxicity (i.e., cell viability) toward a human gingival fibroblast cell line (HGF-1), as an oral epithelial model. Results indicated no toxic effects of GSH-AgNPs at low concentrations (≤6.16 µg/mL, Ag concentration). Higher concentrations resulted in losing cell viability, which followed the Ag accumulation in cells. Finally, the inflammatory response in the HGF-1 cells after their exposure to GSH-AgNPs was measured as the production of immune markers (interleukins 6 and 8 (IL-6 and IL-8) and tumor necrosis factor-alpha (TNF-α)). GSH-AgNPs activates the inflammatory response in human gingival fibroblasts, increasing the production of cytokines. These findings provide new insights for the use of GSH-AgNPs in dental care and encourage further studies for their application.

Synthesis, In-Vitro and In-Silico Evaluation of Silver Nanoparticles with Root Extract of Withania somnifera for Antibacterial Activity via Binding of Penicillin-Binding Protein-4

BACKGROUND

Metal Nanoparticles (NPs) have been widely used for various applications in biomedical sciences, including in drug delivery, and as therapeutic agents, but limited owing to their toxicity towards the healthy tissue. This warrants an alternative method, which can achieve the desired activity with much reduced or no toxicity. Being a biological product, Withania somnifera (W. somnifera) is environment friendly, besides being less toxic as compared to metal-based NPs. However, the exact mechanism of action of W. somnifera for its antibacterial activities has not been studied so far.

OBJECTIVE

To develop "silver nanoparticles with root extract of W. somnifera (AgNPs-REWS)" for antimicrobial and anticancer activities. Furthermore, the analysis of their mechanism of action will be studied.

METHODS

Using the in-silico approach, the molecular docking study was performed to evaluate the possible antibacterial mechanism of W. somnifera phytochemicals such as Anaferine, Somniferine, Stigmasterol, Withaferin A, Withanolide- A, G, M, and Withanone by the inhibition of Penicillin- Binding Protein 4 (PBP4). Next, we utilized a bottom-up approach for the green synthesis of AgNPs- REWS, performed an in-detail phytochemical analysis, confirmed the AgNPs-REWS by SEM, UVvisible spectroscopy, XRD, FT-IR, and HPLC. Eventually, we examined their antibacterial activity.

RESULTS

The result of molecular docking suggests that WS phytochemicals (Somniferine, Withaferin A, Withanolide A, Withanolide G, Withanolide M, and Withanone) possess the higher binding affinity toward the active site of PBP4 as compared to the Ampicillin (-6.39 kcal/mol) reference molecule. These phytochemicals predicted as potent inhibitors of PBP4. Next, as a proof-of-concept, AgNPs- REWS showed significant antibacterial effect as compared to crude, and control; against Xanthomonas and Ralstonia species.

CONCLUSION

The in-silico and molecular docking analysis showed that active constituents of W. somnifera such as Somniferine, Withaferin A, Withanolide A, Withanolide G, Withanolide M, and Withanone possess inhibition potential for PBP4 and are responsible for the anti-bacterial property of W. somnifera extract. This study also establishes that AgNPs via the green synthesis with REWS showed enhanced antibacterial activity towards pathogenic bacteria.

The Antibacterial Mechanism of Silver Nanoparticles and Its Application in Dentistry

Nanotechnology has recently emerged as a rapidly growing field with numerous biomedical science applications. At the same time, silver has been adopted as an antimicrobial material and disinfectant that is relatively free of adverse effects. Silver nanoparticles possess a broad spectrum of antibacterial, antifungal and antiviral properties. Silver nanoparticles have the ability to penetrate bacterial cell walls, changing the structure of cell membranes and even resulting in cell death. Their efficacy is due not only to their nanoscale size but also to their large ratio of surface area to volume. They can increase the permeability of cell membranes, produce reactive oxygen species, and interrupt replication of deoxyribonucleic acid by releasing silver ions. Researchers have studied silver nanoparticles as antimicrobial agents in dentistry. For instance, silver nanoparticles can be incorporated into acrylic resins for fabrication of removable dentures in prosthetic treatment, composite resin in restorative treatment, irrigating solution and obturation material in endodontic treatment, adhesive materials in orthodontic treatment, membrane for guided tissue regeneration in periodontal treatment, and titanium coating in dental implant treatment. Although not all authorities have acknowledged the safety of silver nanoparticles, no systemic toxicity of ingested silver nanoparticles has been reported. A broad concern is their potential hazard if they are released into the environment. However, the interaction of nanoparticles with toxic materials and organic compounds can either increase or reduce their toxicity. This paper provides an overview of the antibacterial use of silver nanoparticles in dentistry, highlighting their antibacterial mechanism, potential applications and safety in clinical treatment.

Application of Antimicrobial Nanoparticles in Dentistry

Oral cavity incessantly encounters a plethora of microorganisms. Plaque biofilm-a major cause of caries, periodontitis and other dental diseases-is a complex community of bacteria or fungi that causes infection by protecting pathogenic microorganisms from external drug agents and escaping the host defense mechanisms. Antimicrobial nanoparticles are promising because of several advantages such as ultra-small sizes, large surface-area-to-mass ratio and special physical and chemical properties. To better summarize explorations of antimicrobial nanoparticles and provide directions for future studies, we present the following critical review. The keywords "nanoparticle," "anti-infective or antibacterial or antimicrobial" and "dentistry" were retrieved from Pubmed, Scopus, Embase and Web of Science databases in the last five years. A total of 172 articles met the requirements were included and discussed in this review. The results show that superior antibacterial properties of nanoparticle biomaterials bring broad prospects in the oral field. This review presents the development, applications and underneath mechanisms of antibacterial nanoparticles in dentistry including restorative dentistry, endodontics, implantology, orthodontics, dental prostheses and periodontal field.

Cytotoxicity evaluation of fungal-derived silver nanoparticles on human gingival fibroblast cell line: An in vitro study

Background:

Biosynthesized silver nanoparticles (AgNPs) have been proposed as effective antimicrobial agents against endo–perio pathogens. Determination of cytotoxicity is important for effective clinical use.

Aim:

The aim is to determine the cytotoxicity of fungal-derived AgNPs on human gingival fibroblast (HGF) cell line using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.

Materials and Methods:

HGF cell cultures were trypsinized and adjusted to 5 × 10³ cells/ml and 100-μl cell suspension (50,000 cells/well) and were added to 96-well plate. After 24 h, 100 μl of AgNPs (8–512-μg/ml concentrations) was added and incubated at 37°C for 24 h in 5% CO₂ atmosphere. Controls were used without AgNPs. MTT (1 mg/ml) was added and incubated for 4 h at 37°C in 5% CO₂ atmosphere. Microscopic examination was done, and absorbance was measured using a microplate reader at a wavelength of 540 nm. Percentage growth inhibition was calculated, and the concentration of AgNPs needed to inhibit cell growth by 50% (CTC₅₀) was generated.

Results:

CTC₅₀ was found at a concentration of 260 μg/ml. AgNPs exerted less cytotoxicity against HGF cell line and increased with increase in the concentration of AgNPs.

Conclusion:

Fungal-derived AgNPs are safe to healthy cells at a concentration <260 μg/ml. Therefore, they can be effectively used for the treatment of endo–perio lesions.

Antibiofilm efficacy of biosynthesized silver nanoparticles against endodontic-periodontal pathogens: An in vitro study

Background:

Endodontic-periodontal pathogens exist as biofilms which are difficult to eliminate. Biosynthesized silver nanoparticles (AgNPs) emerged as newer antimicrobial agents with potential benefits.

Aim:

The aim of this study is to determine the minimum inhibitory concentration (MIC); evaluate the antibiofilm efficacy of fungal-derived AgNPs against Porphyromonas gingivalis, Bacillus pumilus, and Enterococcus faecalis.

Materials and Methods:

MIC of AgNPs against test pathogens was determined using micro broth dilution method. Serial dilutions of AgNPs ranging from 80 to 1 μg/ml concentration were added to wells containing 10 μl of bacterial inoculum in culture media and control group without AgNPs. For biofilm models, 120 dentin blocks were prepared, sterilized, and contaminated for 2 weeks with (n = 40 each). Group 1: B. pumilus, Group 2: E. faecalis, and Group 3: P. gingivalis and each group is divided into four subgroups (n = 10 each) and treated with distilled water, AgNPs, 2% and 0.2% chlorhexidine (CHX). Colonies counted after 24 h of incubation and statistically analyzed using one-way ANOVA and post hoc Tukey tests.

Results:

MIC for B. pumilus was determined as 20 μg/ml and 30 μg/ml for E. faecalis and P. gingivalis. AgNPs were effective as 2% CHX against all biofilms compared to control group. Post hoc Tukey test (P < 0.0001) shows no significant difference between groups.

Conclusion:

Fungal-derived AgNPs are effective against endo-perio pathogens.

Antibacterial Efficacy of Biosynthesized Silver Nanoparticles against Enterococcus faecalis Biofilm: An in vitro Study

Aim

This study aims to evaluate the antibacterial efficacy of biosynthesized silver nanoparticles (AgNPs) produced using the fungi against Enterococcus faecalis biofilm model on root dentin.

Materials and Methods

AgNPs were biosynthesized using the fungi Fusarium semitectum isolated from healthy leaves of Withania somnifera. Minimum inhibitory concentration (MIC) of AgNPs was determined by microbroth dilution method using series of dilutions. MIC dose was standardized to evaluate the antibacterial efficacy. For biofilm model, thirty root dentin blocks prepared using human extracted single-rooted teeth were inoculated with E. faecalis in Trypticase soy agar broth for 2 weeks with alternate day replenishment and randomly divided into three groups (n = 10 each) and treated as: Group I: Sterile distilled water, Group II: AgNPs, and Group III: 2% chlorhexidine gluconate (CHX) and incubated at 37°C for 24 h. Each dentin block was rinsed in saline, vortex shaken for 60 s, and serial decimal dilutions were prepared and plated on trypticase soy agar plates and incubated for 24 h followed by CFU colony counting and statistically analyzed using one-way ANOVA followed by post hoc Tukey honestly significant difference test.

Results

MIC of AgNPs for E. faecalis was determined as 30 mg/ml. No significant difference was seen between AgNPs and 2% CHX when compared to the control group with mean colony counts being 2.4, 2.5, and 6.77 CFU/ml (10⁷), respectively (P < 0.0001), against E. faecalis biofilm.

Conclusion

Biosynthesized AgNPs exhibit effective antimicrobial activity against E. faecalis biofilm on root dentin. Therefore, it can be employed as antimicrobial agent for root canal disinfection.