Treatment of dental biofilm-forming bacterium Streptococcus mutans using tannic acid-mediated gold nanoparticles

Comprehensive strategies for overcoming dental biofilms: Microbial dynamics and innovative methods

Dental biofilm develops through a complex process initiated by the attachment of early colonising bacteria to the surface of teeth. These bacteria use specific adhesion molecules to bind to the enamel, after which they proliferate and secrete an extracellular polymeric substance. As a result, the early colonisers eventually form a resilient, multispecies community encased in an extracellular polymeric matrix, reinforcing the biofilm structure. This matrix enables microbes to withstand the mechanical disruption, evade host immune defences and resist many antimicrobials. Diseases associated with dental biofilm are among the most prevalent oral health issues, highlighting the importance of effective biofilm management in maintaining oral health. This review explores the progression of biofilm development and evaluates various strategies, from conventional antibiotics and herbal medicine to advanced strategies like antimicrobial peptides, nanoparticles, probiotics, cold atmospheric plasma, quorum sensing inhibitors and enzymes. In particular, enzymatic agents such as Dispersin B, DNAases, and glucanohydrolases, including mutanase and dextranase, have shown promise in disrupting the biofilm structure, thereby offering potential avenues for managing dental biofilm.

Simultaneous electrochemical detection of heavy metal ions using a sol-gel synthesized BiVO4 nanosphere modified electrode and its antimicrobial activity

This study explores the development of an advanced electrochemical sensor designed for the simultaneous detection of Cd2+, Pb2+, Cu2+, and Hg2+ ions. The sensor utilizes sol-gel-synthesized bismuth vanadate (BiVO4) nanospheres, which are integrated onto a glassy carbon electrode (GCE), and employs square wave anodic stripping voltammetry (SWASV) for electrochemical determination of heavy metal ions. The as-prepared sensor demonstrated exceptional analytical performance and offered a wide linear detection range from 0 μM to 110 μM, along with low detection limits of 2.75 μM for Cd2+, 2.32 μM for Pb2+, 2.72 μM for Cu2+, and 1.20 μM for Hg2+ ions. These characteristics made the sensor highly suitable for precise monitoring of heavy metal contamination in both environmental and industrial samples. Beyond their sensing capabilities, the BiVO4 nanospheres also exhibited significant antimicrobial activity against bacterial strains such as E. coli and S. aureus, as well as fungal strains like C. albicans and C. parapsilosis. This antimicrobial effect was attributed to the enhanced surface reactivity and the generation of reactive oxygen species (ROS), which disrupt microbial cellular functions. This dual-functional approach highlighted the substantial progress in both electrochemical sensing and antimicrobial applications. This research presents a strong platform for tackling urgent challenges in environmental monitoring and microbial control.

Biosynthesis of titanium dioxide nanoparticles using Sargassum tenerrimum as reductant and deciphering its antibiofilm role against cariogenic Candida albicans

The present study aimed to biosynthesize titanium dioxide nanoparticles (TiO2NPs) using marine macroalgae Sargassum tenerrimum (ST) and ascertain its ability to impede biofilm formation, exopolysaccharide production and induce protein leakage in dental caries-forming Candida albicans. Characterization of ST-TiO2NPs by UV-Vis spectra recorded a sharp peak at 365 nm. FT-IR results showed active functional groups involved in stabilizing the ST-TiO2NPs. XRD results confirmed the nano-crystalline nature with a mean grain size of 65.8 nm. FE-SEM results revealed that ST-TiO2NPs were spherical and square-shaped, and EDX affirmed titanium. Zeta potential analysis affirmed the stability of the ST-TiO2 nanoparticles. TiO2NPs efficiently impeded biofilm formation (32 %-97 %) by C. albicans in a dose-dependent manner. Antibiofilm assay by Confocal Laser Scanning Microscope (CLSM) study showed that at 150 μg/ml, the ST-TiO2NPs strongly disrupted the biofilm architecture of C. albicans. This was further substantiated by a notable reduction in exopolysaccharide and a rise in protein leakage with the increase in concentration (50-150 μg/ml) of ST-TiO2NPs and time interval (12 h-60 h). This is the first study emphasizing that S.tenerrimum-mediated TiO2NPs strongly deterred and distorted C. albicans biofilms and further suggested that it could be effectively utilized as nano-antibiotics by coating the surface of dental implants to mitigate biofilm formation by oral pathogens.

Unleashing the Potential of Tannic Acid in Dentistry: A Scoping Review of Applications

(1) Background: Tannic acid (TA), a water-soluble polyphenol extensively found in numerous plant species, possesses antimicrobial, anti-inflammatory, antioxidant, and adhesive properties. This scoping review aims to synthesize existing knowledge on TA applications and unveil its potential uses in dentistry. (2) Methods: A comprehensive search across six electronic databases (PubMed, Cochrane, Embase, Scopus, Web of Science, and Opengrey) was conducted in October 2024. Two reviewers performed the screening and risk of bias analysis independently following the PRISMA-ScR guidelines. The findings are presented in a narrative summary. (3) Results: Five hundred and twelve records were identified from the electronic databases. After removing duplicates and applying eligibility criteria, ninety-six studies were ultimately included in this review. Results indicate that TA has been employed in managing dentin hypersensitivity, dental caries, periodontal and mucosal diseases, as well as dentition defects with prostheses. Furthermore, TA displays potential in enhancing the performance of bonding adhesives, root canal irrigants, and root canal filling materials. However, it is noteworthy that the included studies exhibit varied experimental settings, inconsistent outcome measures, a lack of extensive clinical research, and insufficient observation periods. (4) Conclusions: TA is a promising biomaterial with applications to various dental fields, such as endodontics, periodontology, prosthodontics, and dental public health. Its antimicrobial, anti-inflammatory, antioxidant, and adhesive properties warrant future exploration to unleash these potentials and provide robust scientific evidence that guides clinical practice and advances oral healthcare.

Biofilm associated growth inhibition of XDR Escherichia fergusonii strain ACE12 isolated from soil

Biofilm formation by bacteria is highly recognized for virulence factors resulting in their resistance to antimicrobials that lead to biofilm-associated infections. In this study, we isolated Escherichia fergusonii from soil, characterized its biofilm-associated growth, and evaluated the inhibitory potential of anti-biofilm compounds. Test isolate ACE12 was precisely identified as E. fergusonii based on the morphological and 16S rRNA gene sequence analysis. The antibiotic susceptibility pattern of ACE12 showed its resistance to β-Lactams, Aminoglycosides, Macrolides, Tetracycline, Trimethoprim, Vancomycin, & Nitrofurans and on the basis of its resistant pattern the isolate was categorized as extensively drug-resistant (XDR) bacteria. In addition, the research isolate ACE12 was found to harbor four distinct antibiotic resistant genes including dfrA1, blaTem-1, tetC, and sul1, encoding the resistant determinants for trimethoprim, β-lactam, tetracycline, and sulfonamide antibiotics, respectively. Initial screening of biofilm formation by Congo-Red Agar (CRA) and Tube method demonstrated that E. fergusonii ACE12 is a biofilm-forming bacterium. The respective biofilm was characterized by estimating the optical density (OD595) of crystal violet (CV)-stained biofilm by Microtiter plate assay, confirming E. fergusonii as a strong biofilm former. Evaluation of anti-biofilm activity of metal salt of zinc (ZnSO4.7H2O), 1,1-Diphenyl-2-Picrylhydrazyl (DPPH), and two phenolic acids including tannic acid (TA) and trans-cinnamic acid (trans-CA) showed that ≥80 % of biofilm was inhibited at their minimum inhibitory concentrations of 15-100 μg/ml for ZnSO4.7H2O, 250-500 μg/ml for DPPH, 40-50 μg/ml for TA, and 500-1000 μg/ml for Trans-CA. Additionally, at a concentration of 2500 μg/ml, ZnO-1 exhibited approximately 80 % biofilm reduction whereas 70 % biofilm was inhibited by ZnO-6. These findings exhibit that, the studied anti-biofilm compounds can effectively inhibit the biofilm associated growth of E. fergusonii.

Therapeutic efficacy of chitosan-based hybrid nanomaterials to treat microbial biofilms and their infections - A review

Antimicrobial resistance, the biggest issue facing the global healthcare sector, quickly emerged and spread due to the frequent use of antibiotics in regular treatments. The investigation of polymer-based nanomaterials as possible antibiofilm treatment agents is prompted by the growing ineffectiveness of conventional therapeutic techniques against these resistant bacteria species. So far, several articles have been published on microbial biofilm eradication using various polymer-based nanomaterials due to their therapeutic efficacy and biocompatibility nature. Despite their potential, a comprehensive review of the chitosan-based hybrid nanomaterials to treat microbial biofilms and their infections is lacking. This review provides a comprehensive investigation of the current state of therapeutic efficacy, various nanoformulations, advantages, limitations, and regulations of chitosan-based hybrid nanomaterials for biofilm treatment. Special attention is given to the application of chitosan-based nanomaterials in wound care, urinary tract infections, and dental biofilms are discussed, highlighting their role in managing biofilm-associated complications. Researchers will be better able to comprehend and develop unique, marketable chitosan-based nanomaterials with increased activity to treat biofilm infections in near future with the aid of this review.

Leveraging bacteria-inspired nanomaterials for targeted controlling biofilm and virulence properties of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen designated as a high-priority pathogen because of its role in major healthcare-associated and nosocomial infections. Biofilm production by these bacteria is one of the adaptive resistance mechanisms to traditional antibiotics, making treatment challenging, especially for immunocompromised patients. P. aeruginosa also produces a variety of virulence factors, which aid in invasion, adhesion, persistence, and immune system protection. Recent advances in nanotechnology-based therapy, notably the application of bioinspired metal and metal-oxide nanomaterials, have been seen as a viable way to control P. aeruginosa biofilm and virulence. Because of its ease of growth and culture, synthesizing metal and metal-oxide nanomaterials using bacterial species has become one of the most environmentally benign green synthesis options. The application of bacterial-inspired nanomaterials is particularly successful for targeted control of P. aeruginosa infection due to interactions with cell membrane components and transport systems. This paper delves into and provides a complete overview of the application of bacterial-inspired metal and metal-oxide nanomaterials to treat P. aeruginosa infection by targeting biofilm and virulence characteristics. The review focused on synthesizing and applying gold, silver, copper, iron, magnetite, and zinc oxide nanomaterials to mitigate P. aeruginosa biofilm and virulence. The underlying mechanism of these metal and metal-oxide nanoparticles in relation to biofilm and virulence features has also been thoroughly discussed. The current review introduces novel approaches to treating and controlling drug-resistant P. aeruginosa using bacterial-inspired nanomaterials as a targeted therapeutic strategy.

Eco-friendly synthesis of betanin-conjugated zinc oxide nanoparticles: antimicrobial efficacy and apoptotic pathway activation in oral cancer cells

BACKGROUND

Phytochemical-based synthesis of nanoparticles (NPs) is an eco-friendly approach with various biomedical applications. Betanin, a natural pigment in beetroot, has antioxidant, anti-inflammatory, and antimicrobial properties. When conjugated with zinc oxide nanoparticles (ZnO NPs), these properties are enhanced. This study aimed to synthesize betanin-ZnO nanoparticles (BE-ZnO-NPs) and evaluate their biological potential.

METHODS

BE-ZnO-NPs were synthesized and characterized using UV-Visible spectroscopy, FTIR, FE-SEM, HR-TEM, EDX, XRD, DLS, and zeta potential analysis. In silico studies assessed interactions with oral pathogen proteins, and antibacterial activity was tested against Enterococcus faecalis, Candida albicans, Staphylococcus aureus and Streptococcus mutans. Antioxidant potential and cytotoxicity on KB cells were evaluated through scavenging assays, MTT assay, and qRT-PCR.

RESULTS

Betanin synthesized ZnO NPs UV-Vis results showed surface plasmon resonance at 388 nm, and FTIR confirmed betanin role as a capping agent. FE-SEM and TEM revealed particles of 37 nm. EDX confirmed zinc content, and XRD showed a hexagonal structure. Zeta potential was - 3.3 mV, and DLS indicated a size of 38.73 nm. In silico analysis showed strong binding to E. faecalis (- 8.0 Kcal/mol). BE-ZnO-NPs demonstrated antibacterial activity at 100 µg/mL, with inhibition zones of 18 ± 0.14 mm for E. faecalis and 14 ± 0.18 mm for S. mutans. In contrast, BE demonstrated antibacterial activity at 100 µg/mL, with zone of inhibition of 10.6 ± 0.14 mm for E. faecalisand 11.4 ± 0.18 mm for S. mutans.Antioxidant assays revealed dose-dependent scavenging activity. Cytotoxicity showed an IC50 of 24.29 µg/mL, with qRT-PCR indicating apoptosis through the BCL2/BAX/P53 pathway.

CONCLUSIONS

BE-ZnO-NPs exhibited significant antibacterial and antioxidant activities and demonstrated the ability to induce apoptosis in oral cancer cells via the BCL-2/BAX/P53 signalling pathway. These findings highlight the potential of BE-ZnO-NPs as promising antimicrobial agents for tooth infections and as therapeutic agents for oral tumour treatment.

Impact of acidic and alkaline conditions on Staphylococcus aureus and Acinetobacter baumannii interactions and their biofilms

Bacterial biofilms pose significant challenges due to their association with antibiotic resistance, metabolic adaptation, and survival under harsh conditions. Among notable pathogens forming biofilms, Staphylococcus aureus and Acinetobacter baumannii are concerning pathogens in nosocomial settings. However, their behaviour under acidic (pH 4.5) and alkaline (pH10.5) conditions, especially in co-culture setups, remains insufficiently understood. This study investigates these aspects, by examining growth rates, biofilm formation, pH shifts, phenotypic analysis, and gene expression profiles. The results showed A. baumannii exhibited reduced  growth and biofilm formation at pH 4.5, while S. aureus showed slow growth and low biofilm formation at pH10.5 in mono-cultures. S. aureus leaned towards an acidic pH (6-6.5), whereas A. baumannii shifted towards an alkaline pH (8-9). In co-culture environments, growth rates and biofilm formation increased across all pH conditions, converging towards a neutral pH over time. Phenotypic motility assays indicated that A. baumannii exhibited greater motility in alkaline conditions, while S. aureus showed increased staphyloxanthin production under acidic conditions. Gene expression analyses revealed that the fibronectin-binding protein A (FnbA) and N-acetylglucosaminyl-transferase (icaA) genes, responsible for initial attachment during biofilm formation, were highly expressed in acidic co-culture condition but poorly expressed in alkaline condition. In A. baumannii, the outer membrane protein A (OmpA) gene associated with adhesion and virulence, was upregulated in co-culture. The LuxR gene involved in quorum sensing was upregulated in acidic conditions and poorly expressed at pH 10.5. This study elucidates the metabolic adaptability and biofilm formation tendencies of S. aureus towards acidic conditions and A. baumannii towards alkaline conditions, providing insights for better management of biofilm-related infections.

Nanoemulsions of essential oils against multi-resistant microorganisms: An integrative review

Microbial resistance to drugs continues to be a global public health issue that demands substantial investment in research and development of new antimicrobial agents. Essential oils (EO) have demonstrated satisfactory and safe antimicrobial action, being used in pharmaceutical, cosmetic, and food formulations. In order to improve solubility, availability, and biological action, EO have been converted into nanoemulsions (NE). This review identified scientific evidence corroborating the antimicrobial action of nanoemulsions of essential oils (NEEO) against antibiotic-resistant pathogens. Using integrative review methodology, eleven scientific articles evaluating the antibacterial or antifungal assessment of NEEO were selected. The synthesis of evidence indicates that NEEO are effective in combating multidrug-resistant microorganisms and in the formation of their biofilms. Factors such as NE droplet size, chemical composition of essential oils, and the association of NE with antibiotics are discussed. Furthermore, NEEO showed satisfactory results in vitro and in vivo evaluations against resistant clinical isolates, making them promising for the development of new antimicrobial and antivirulence drugs.

Ecofriendly biosynthesis of copper nanoparticles from novel marine S. rhizophila species for enhanced antibiofilm, antimicrobial and antioxidant potential

Marine microorganisms offer a promising avenue for the eco-friendly synthesis of nanoparticles due to their unique biochemical capabilities and adaptability to various environments. This study focuses on exploring the potential of a marine bacterial species, Stenotrophomonas rhizophila BGNAK1, for the synthesis of biocompatible copper nanoparticles and their application for hindering biofilms formed by monomicrobial species. The study begins with the isolation of the novel marine S. rhizophila species from marine soil samples collected from the West coast region of Kerala, India. The isolated strain is identified through 16S rRNA gene sequencing and confirmed to be S. rhizophila species. Biosynthesis of copper nanoparticles using S. rhizophila results in the formation of nanoparticles with size of range 10-50 nm. The nanoparticles exhibit a face-centered cubic crystal structure of copper, as confirmed by X-Ray Diffraction analysis. Furthermore, the synthesized nanoparticles display significant antimicrobial activity against various pathogenic bacteria and yeast. The highest inhibitory activity was against Staphylococcus aureus with a zone of 27 ± 1.00 mm and the least activity was against Pseudomonas aeruginosa with a zone of 22 ± 0.50 mm. The zone of inhibition against Candida albicans was 16 ± 0.60 mm. The antibiofilm activity against biofilm-forming clinical pathogens was evidenced by the antibiofilm assay and SEM images. Additionally, the copper nanoparticles exhibit antioxidant activity, as evidenced by their scavenging ability against DPPH, hydroxyl, nitric oxide, and superoxide radicals, as well as their reducing power in the FRAP assay. The study highlights the potential of the marine bacterium S. rhizophila BGNAK1 for the eco-friendly biosynthesis of copper nanoparticles with diverse applications. Synthesized nanoparticles exhibit promising antibiofilm, antimicrobial, and antioxidant properties, suggesting their potential utility in various fields such as medicine, wastewater treatment, and environmental remediation.

Antibacterial and antibiofilm efficacy of Solanum lasiocarpum root extract synthesized silver/silver chloride nanoparticles against Staphylococcus haemolyticus associated with bovine mastitis

Staphylococcus haemolyticus is a cause of bovine mastitis, leading to inflammation in the mammary gland. This bacterial infection adversely affects animal health, reducing milk quality and yield. Its emergence has been widely reported, representing a significant economic loss for dairy farms. Interestingly, S. haemolyticus exhibits higher levels of antimicrobial resistance than other coagulase-negative Staphylococci. In this study, we synthesized silver/silver chloride nanoparticles (Ag/AgCl-NPs) using Solanum lasiocarpum root extract and evaluated their antibacterial and antibiofilm activities against S. haemolyticus. The formation of the Ag/AgCl-NPs was confirmed using UV-visible spectroscopy, which revealed maximum absorption at 419 nm. X-ray diffraction (XRD) analysis demonstrated the crystalline nature of the Ag/AgCl-NPs, exhibiting a face-centered cubic lattice. Fourier transform infrared (FT-IR) spectroscopy elucidated the functional groups potentially involved in the Ag/AgCl-NPs synthesis. Transmission electron microscopy (TEM) analysis revealed that the average particle size of the Ag/AgCl-NPs was 10 nm. Antimicrobial activity results indicated that the minimum inhibitory concentration (MIC) and maximum bactericidal concentration (MBC) of the Ag/AgCl-NPs treatment were 7.82-15.63 μg/mL towards S. haemolyticus. Morphological changes in bacterial cells treated with the Ag/AgCl-NPs were observed under scanning electron microscopy (SEM). The Ag/AgCl-NPs reduced both the biomass of biofilm formation and preformed biofilm by approximately 20.24-94.66 % and 13.67-88.48 %. Bacterial viability within biofilm formation and preformed biofilm was reduced by approximately 21.56-77.54 % and 18.9-71.48 %, respectively. This study provides evidence of the potential of the synthesized Ag/AgCl-NPs as an antibacterial and antibiofilm agent against S. haemolyticus.

Tannic acid inhibits Escherichia coli biofilm formation and underlying molecular mechanisms: Biofilm regulator CsgD

Biofilms often engender persistent infections, heightened antibiotic resistance, and the recurrence of infections. Therefor, infections related to bacterial biofilms are often chronic and pose challenges in terms of treatment. The main transcription regulatory factor, CsgD, activates csgABC-encoded curli to participate in the composition of extracellular matrix, which is an important skeleton for biofilm development in enterobacteriaceae. In our previous study, a wide range of natural bioactive compounds that exhibit strong affinity to CsgD were screened and identified via molecular docking. Tannic acid (TA) was subsequently chosen, based on its potent biofilm inhibition effect as observed in crystal violet staining. Therefore, the aim of this study was to investigate the specific effects of TA on the biofilm formation of clinically isolated Escherichia coli (E. coli). Results demonstrated a significant inhibition of E. coli Ec032 biofilm formation by TA, while not substantially affecting the biofilm of the ΔcsgD strain. Moreover, deletion of the csgD gene led to a reduction in Ec032 biofilm formation, alongside diminished bacterial motility and curli synthesis inhibition. Transcriptomic analysis and RT-qPCR revealed that TA repressed genes associated with the csg operon and other biofilm-related genes. In conclusion, our results suggest that CsgD is one of the key targets for TA to inhibit E. coli biofilm formation. This work preliminarily elucidates the molecular mechanisms of TA inhibiting E. coli biofilm formation, which could provide a lead structure for the development of future antibiofilm drugs.