The antibacterial effects of silver, titanium dioxide and silica dioxide nanoparticles compared to the dental disinfectant chlorhexidine on Streptococcus mutans using a suite of bioassays.

Metal-containing nanomaterials have the potential to be used in dentistry for infection control, but little is known about their antibacterial properties. This study investigated the toxicity of silver (Ag), titanium dioxide and silica nanoparticles (NPs) against the oral pathogenic species of Streptococcus mutans, compared to the routine disinfectant, chlorhexidine. The bacteria were assessed using the minimum inhibitory concentration assay for growth, fluorescent staining for live/dead cells, and measurements of lactate. All the assays showed that Ag NPs had the strongest antibacterial activity of the NPs tested, with bacterial growth also being 25-fold lower than that in chlorhexidine. The survival rate of bacteria under the effect of 100 mg l(-1) Ag NPs in the media was 2% compared to 60% with chlorhexidine, while the lactate concentration was 0.6 and 4.0 mM, respectively. Silica and titanium dioxide NPs had limited effects. Dialysis experiments showed negligible silver dissolution. Overall, Ag NPs were the best disinfectant and performed better than chlorhexidine. Improvements to the MIC assay are suggested

Antibacterial activity and biofilm inhibition by surface modified titanium alloy medical implants following application of silver, titanium dioxide and hydroxyapatite nanocoatings

peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=inan2

Antifungal properties and biocompatibility of silver nanoparticle coatings on silicone maxillofacial prostheses in vitro

Patients with facial prostheses suffer from yeast, Candida albicans, infections. This study aimed to determine the biocompatibility and antifungal properties of silicone facial prostheses coated with silver nanoparticles (Ag NPs) in vitro. Medical grade silicone discs were coated with 5 and 50 mg L−1 dispersions of either Ag NPs or AgNO3. Coatings were fully characterized using scanning electron microscopy and energy dispersive X‐ray spectroscopy. The biocompatibility was examined using human dermal fibroblasts (Hs68), whereas antifungal efficacy was tested against C. albicans (NCPF‐3179). The fibroblast viability was assessed by measuring lactate dehydrogenase (LDH) activity, protein content and tissue electrolytes. There were no effects on the LDH activity of fibroblast cell homogenates, and leak of LDH activity into external media remained low (0.1–0.2 IU mL−1). Sublethal effects of Ag NP coatings on membrane permeability/ion balance was not observed, as measured by stable homogenate Na+ and K+ concentrations. Some Ag (13 mg L−1) was detected from the AgNO3 coatings in the media, but total Ag remained below detection limit (<1.2 µg L−1) for the Ag NP coatings; indicating the latter were stable. When fibroblasts grown on silver coatings were challenged with C. albicans, the Ag NP coating was effective at preventing fungal growth as measured by ethanol production by the yeast, and without damaging the fibroblasts. Ethanol production decreased from 43.2 ± 25.02 in controls to 3.6 µmol mL−1 in all the silver treatments. Data shows that silicone prosthetic materials coated with Ag NPs are biocompatible with fibroblast cells in vitro and show antifungal properties. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1038–1051, 2018.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142985/1/jbmb33917_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142985/2/jbmb33917.pd

Hospital sink traps as a potential source of the emerging multidrug-resistant pathogen Cupriavidus pauculus: characterization and draft genome sequence of strain MF1

This is the final version. Available on open access from the Microbiology Society via the DOI in this recordData availability: This project has been deposited at DDBJ/ENA/GenBank under the accession JAIQWY000000000 within BioProject PRJNA762702. The version described in this paper is version JAIQWY010000000. The contig sequences can be found under accession numbers JAIQWY010000001–JAIQWY010000005. Raw sequence data have been deposited under accession numbers SRX13365403 and SRX13365404. Four supplementary tables are available with the online version of this article.Introduction. Cupriavidus pauculus is historically found in soil and water but has more recently been reported to cause human infection and death. Hospital sink traps can serve as a niche for bacterial persistence and a platform for horizontal gene transfer, with evidence of dissemination of pathogens in hospital plumbing systems driving nosocomial infection.Gap Statement. This paper presents the first C. pauculus strain isolated from a hospital sink trap. There are only six genome assemblies available on NCBI for C. pauculus; two of these are PacBio/Illumina hybrids. This paper presents the first ONT/Illumina hybrid assembly, with five contigs. The other assemblies available consist of 37, 38, 111 and 227 contigs. This paper also presents data on biofilm formation and lethal dose in Galleria mellonella; there is little published information describing these aspects of virulence.Aim. The aims were to identify the isolate found in a hospital sink trap, characterize its genome, and assess whether it could pose a risk to human health.Methodology. The genome was sequenced, and a hybrid assembly of short and long reads produced. Antimicrobial susceptibility was determined by the broth microdilution method. Virulence was assessed by measuring in vitro biofilm formation compared to Pseudomonas aeruginosa and in vivo lethality in Galleria mellonella larvae.Results. The isolate was confirmed to be a strain of C. pauculus, with a 6.8 Mb genome consisting of 6468 coding sequences and an overall G+C content of 63.9 mol%. The genome was found to contain 12 antibiotic resistance genes, 8 virulence factor genes and 33 metal resistance genes. The isolate can be categorized as resistant to meropenem, amoxicillin, amikacin, gentamicin and colistin, but susceptible to cefotaxime, cefepime, imipenem and ciprofloxacin. Clear biofilm formation was seen in all conditions over 72 h and exceeded that of P. aeruginosa when measured at 37 °C in R2A broth. Lethality in G. mellonella larvae over 48 h was relatively low.Conclusion. The appearance of a multidrug-resistant strain of C. pauculus in a known pathogen reservoir within a clinical setting should be considered concerning. Further work should be completed to compare biofilm formation and in vivo virulence between clinical and environmental strains, to determine how easily environmental strains may establish human infection. Infection control teams and clinicians should be aware of the emerging nature of this pathogen and further work is needed to minimize the impact of contaminated hospital plumbing systems on patient outcomes

Multilayered composite coatings of titanium dioxide nanotubes decorated with zinc oxide and hydroxyapatite nanoparticles: Controlled release of Zn and antimicrobial properties against staphylococcus aureus

This study aimed to decorate the surface of TiO2 nanotubes (TiO2 NTs) grown on medical grade Ti-6Al-4V alloy with an antimicrobial layer of nano zinc oxide particles (nZnO) and then determine if the antimicrobial properties were maintained with a final layer of nano-hydroxyapatite (HA) on the composite. The additions of nZnO were attempted at three different annealing temperatures: 350, 450 and 550 °C. Of these temperatures, 350°C provided the most uniform and nanoporous coating and was selected for antimicrobial testing. The LIVE/DEAD assay showed that ZnCl2 and nZnO alone were >90% biocidal to the attached bacteria, and nZnO as a coating on the nanotubes resulted in around 70% biocidal activity. The lactate production assay agreed with the LIVE/DEAD assay. The concentrations of lactate produced by the attached bacteria on the surface of nZnO-coated TiO2 NTs and ZnO/HA-coated TiO2 NTs were 0.13±0.03 mM and 0.37±0.1 mM, respectively, which was significantly lower than that produced by the bacteria on TiO2 NTs alone, 1.09±0.30 mM (Kruskal–Wallis, P<0.05, n=6). These biochemical measurements were correlated with electron micrographs of cell morphology and cell coverage on the coatings. nZnO on TiO2 NTs was a stable and antimicrobial coating, and most of the biocidal properties remained in the presence of nano-HA on the coating.Plymouth University; University of Derb

Antibacterial properties of silver nanoparticles grown in situ and anchored to titanium dioxide nanotubes on titanium implant against Staphylococcus aureus

Medical grade titanium alloy, Ti-6Al-4V, with TiO2 nanotubes (TiO2-NTs) grown on the surface and then decorated with silver nanoparticles (Ag NPs) is proposed to enhance the antimicrobial properties of the bone/dental implants. However, the decoration with Ag NPs is not consistent and there are concerns about the direct contact of Ag NPs with human tissue. The aim of this study was to achieve a more even coverage of Ag NPs on TiO2-NTs and determine their biocidal properties against Staphylococcus aureus, with and without a top coat of nano hydroxyapatite (nHA). The decoration with Ag NPs was optimised by adjusting the incubation time of the TiO2-NTs in a silver ammonia solution, and using biocompatible δ-gluconolactone as a reducing agent. The optimum incubation in silver ammonia was 7 min, and resulted in evenly distributed Ag NPs with an average diameter of 47.5 ± 1.7 nm attached to the surface of the nanotubes. The addition of nHA did not compromise the antimicrobial properties of the materials; high-resolution electron microscopy showed S. aureus did not grow on the composite with nHA and with >80% biocidal activity measured by the LIVE/DEAD assay, also limited lactate production. Dialysis experiment confirmed the stability of the coatings, and showed a slow release of dissolved silver (3.27 ± 0.15 μg/L over 24 h) through the top coat of nHA.Plymouth Universit

Zinc-modified nanopolymers improve the quality of resin-dentin bonded interfaces

Introduction: Demineralized collagen fibers at the hybrid layer are susceptible to degradation. Remineralization may aid to improve bond longevity. Objectives: The aim of the present study was to infiltrate zinc and calcium-loaded polymeric nanoparticles into demineralized dentin to facilitate hybrid layer remineralization. Materials and methods: Zinc or calcium-loaded polymeric nanoparticles were infiltrated into etched dentin, and Single Bond Adhesive was applied. Bond strength was tested after 24 h and 6 months storage. Nanomechanical properties, dyeassisted confocal laser microscopy, and Masson’s trichrome staining evaluation were performed to assess for the hybrid layer morphology, permeability, and remineralization ability after 24 h and 3 months. Data were analyzed by ANOVA and Student–Newman–Keuls multiple comparisons tests (p < 0.05). Results: Immediate bond strength was not affected by nanoparticles infiltration (25 to 30 MPa), while after 6 months, bond strengths were maintained (22 to 24 MPa). After 3 months, permeability occurred only in specimens in which nanoparticles were not infiltrated. Dentin remineralization, at the bottom of the hybrid layer, was observed in all groups. After microscopy analysis, zinc-loaded nanoparticles were shown to facilitate calcium deposition throughout the entire hybrid layer. Young’s modulus at the hybrid layer increased from 2.09 to 3.25 GPa after 3 months, in specimens with zinc nanoparticles; meanwhile, these values were reduced from 1.66 to 0.49 GPa, in the control group. Conclusion: Infiltration of polymeric nanoparticles into demineralized dentin increased long-term bond strengths. Zinc-loaded nanoparticles facilitate dentin remineralization within the complete resin–dentin interface. Clinical relevance: Resin–dentin bond longevity and dentin remineralization at the hybrid layer were facilitated by zincloaded nanoparticles.This work was supported by a grant, MINECO/FEDER MAT2014-52036-P