Anti-biofilm and antibacterial activities of zinc oxide nanoparticles against the oral opportunistic pathogens Rothia dentocariosa and Rothia mucilaginosa.

Species of the genus Rothia that inhabit the oral cavity have recently been implicated in a number of diseases. To minimize their role in oral infections, it is imperative to reduce and/or control the growth and biofilm formation activity of Rothia spp. In this study, two bacterial isolates, Ora-7 and Ora-16, were obtained from the oral cavity of a healthy male subject and identified as Rothia dentocariosa and Rothia mucilaginosa, respectively, using a polyphasic taxonomic approach. Antimicrobial and anti-biofilm formation activities of zinc oxide nanoparticles (ZnO-NPs), of average size 35 nm, were assessed in in vitro assays using Crystal Violet and live and dead staining techniques. The ZnO-NPs exhibited an IC50 value of 53 and 76 µg ml(-1) against R. dentocariosa and R. mucilaginosa, respectively. Biofilm-formation assays, performed on the surfaces of polystyrene plates, artificial teeth, and dental prostheses, revealed the efficacy of ZnO-NPs as a potential antibacterial agent for controlling the growth of Rothia isolates in both planktonic form and biofilm.

Mesoporous multi-silica layer-coated Y2O3:Eu core-shell nanoparticles: Synthesis, luminescent properties and cytotoxicity evaluation.

Mesoporous multi-layered silica-coated luminescent Y2O3:Eu nanoparticles (NPs) were prepared by a urea-based decomposition process, and their surfaces were gradually modified with nanoporous and mesoporous silica layers using modified sol-gel methods. The synthesized luminescent core-shell NPs were characterized thoroughly to investigate their structural, morphological, thermal, optical, photo luminescent properties and their surface chemistry. The morphology of the core NPs were nearly spherical in shape and were nano-sized grains. The observed luminescent efficiency of the mesoporous multi-layered silica-coated luminescent core NPs was gradually reduced because of bond formation between the Y2O3:Eu core and the amorphous silica shell via YOSiOH bridges on the surface of the NPs; the bonds suppressed the non-radiative transition pathways. Biocompatibility tests on Human breast cancer cells using the 3­(4,5­Dimethylthiazol­2­yl)­2,5­diphenyltetrazolium bromide and lactate dehydrogenase assays indicated that the core-shell NPs were non-toxic even at high concentrations. The mesoporous SiO2 layer played a key role in perfecting the solubility, biocompatibility, and non-toxicity of the NPs. The zeta potential, surface chemistry (Fourier transform infrared spectroscopy), and optical absorption spectral analyses revealed the high hydrophilicity of the as-prepared core-shell NPs because of the active surface-functionalized silanol (SiOH) groups, which could potentially offer many exciting opportunities in photonic-based biomedical applications.

Highly biocompatible, monodispersed and mesoporous La(OH)3:Eu@mSiO2 core-shell nanospheres: Synthesis and luminescent properties.

Monodispersed La(OH)3:Eu nanospheres(core-NSs) were synthesized by urea-based homogeneous co-precipitation process, where mesoporous silica layer was coated over the surface of luminescent La(OH)3:Eu core-NSs. The XRD data exhibit the high crystalline, single hexagonal-shaped La(OH)3:Eu core and silica modified La(OH)3:Eu@mSiO2 (core-shell) NSs. Monodispersibility, spherical shaped, high surface area and mesoporosity were identified by TEM analysis and were further confirmed by BET analysis. The as-synthesized samples are highly soluble in aqueous media at ambient conditions. Spectroscopic analyses were also carried out to examine the impact of surface modification on structural, surface chemistry, optical and luminescence behavior of the as-designed silica coated core-shell NSs. The emission spectral study revealed that the luminescence intensity of magnetic-dipole transition (590 nm, 5D0 → 7F1) is dominant with respect to electric-dipole (614 nm, 5D0 → 7F2) transition. The high crystallinity of the hydroxide products supports the existence of good photoluminescence intensity, a good indication for their future use in detection of biomacromolecules through hypersensitive emission (614 nm, 5D0 → 7F2) transition. Excellent biocompatibility, cell viability and good luminescence properties suggested that the as-prepared core-shell NSs are an ideal candidate for luminescence biolabeling/bioimaging and as an optical bio-probe.

Environmental lead toxicity and nutritional factors.

Environmental lead toxicity is an old but persistent public health problem throughout the world and children are more susceptible to lead than adults because of their hand to mouth activity, increased respiratory rates and higher gastrointestinal absorption per unit body weight. In the last decade children's blood lead levels have fallen significantly in a number of countries. Despite this reduction, childhood lead toxicity continues to be a major public health problem for certain at-risk groups of children, and concern remains over the effects of lead on intellectual development. The currently approved clinical intervention method is to give chelating agents, which bind and removed lead from lead burdened tissues. Studies indicate, however, that there is a lack of safety and efficacy when conventional chelating agents are used. Several studies are underway to determine the beneficial effect of nutrients supplementation following exposure to lead. Data suggest that nutrients may play an important role in abating some toxic effects of lead. To explain the importance of using exogenous nutrients in treating environmental lead toxicity the following topics are addressed: (i) different sources of lead exposure/current blood lead levels and (ii) protective effects of nutrients supplementation (some essential elements and vitamins) in lead toxicity.

Comparative effectiveness of NiCl2, Ni- and NiO-NPs in controlling oral bacterial growth and biofilm formation on oral surfaces.

OBJECTIVE: Oral ailments are often treated with antibiotics, which are rendered ineffective as bacteria continue to develop resistance against them. It has been suggested that the nanoparticles (NPs) approach may provide a safer and viable alternative to traditional antibacterial agents. Therefore, nickel (Ni)- and nickel oxide (NiO)-NPs were synthesized, characterized and assessed for their efficacy in reducing oral bacterial load in vitro. Also, the effects of bulk compound NiCl2 (Ni ions), along with the Ni- and NiO-NPs on bacterial exopolysaccharide (EPS) production and biofilm formation on the surface of artificial teeth, and acrylic dentures, were investigated. METHODS: Total bacteria from a healthy male were collected and adjusted to 4×109cells/ml for all the tests. Effect of the NPs on growth, biofilm formation, EPS production and acid production from glucose was tested using standard protocols. RESULTS: Data revealed that the Ni-NPs (average size 41.23nm) exhibited an IC50 value of 73.37µg/ml against total oral bacteria. While, NiO-NPs (average size 35.67nm) were found less effective with much higher IC50 value of 197.18µg/ml. Indeed, the Ni ions exhibited greater biocidal activity with an IC50 value of 70µg/ml. Similar results were obtained with biofilm inhibition on the surfaces of dental prostheses. The results explicitly suggested the effectiveness of tested Ni compounds on the growth of oral bacteria and biofilm formation in the order as NiCl2>Ni-NPs>NiO-NPs. CONCLUSION: The results elucidated that Ni-NPs could serve as effective nanoantibiotics against oral bacteria.