Antibacterial properties and compressive strength of new one-step preparation silver nanoparticles in glass ionomer cements (NanoAg-GIC).

OBJECTIVES: This work aimed (1) to develop polyacid formulations by the one-step photoreduction of silver nanoparticles (AgNP) in a polyacrylate solution of conventional glass ionomer cement (GIC), imparting antibacterial activity; and (2) to evaluate handling and mechanical properties of experimental ionomers in comparison to a commercially available conventional GIC. METHODS: Formulations with increasing sub-stoichiometric amounts of AgNO3 were monitored during continuous UV light exposure by UV-vis spectroscopy and analyzed by transmission electron microscopy. The resulted synthesis of formulations containing small and disperse spherical nanoparticles (∼6 nm) were used to design the experimental nano-silver glass ionomer cements (NanoAg-GIC). The cements were characterized as to net setting time and compressive strength according to ISO 9917-1:2007 specifications. The antibacterial activity of these cements was assessed by Ag+ diffusion tests on nutritive agar plates (E. coli) and by MTT assay (S. mutans). RESULTS: The higher concentration of silver (0.50% by mass) in the matrix of NanoAg-GIC allowed viable net setting time and increased in 32% compressive strength of the experimental cement. All groups containing AgNP induced statistically significant E. coli growth inhibition zones (p-value <.05), indicating diffusion of Ag+ ions on the material surroundings. Metabolic activity of S. mutans grown on NanoAg-GIG with higher concentration of silver was significantly affected compared to control (p-value <.01). CONCLUSIONS: Silver nanoparticles one-step preparation in polyacrylate solution allowed the production of highly bioactive water-based cements within suitable parameters for clinical use and with large potential of dental and biomedical application.

The interaction of cells and bacteria with surfaces structured at the nanometre scale.

The current development of nanobiotechnologies requires a better understanding of cell-surface interactions on the nanometre scale. Recently, advances in nanoscale patterning and detection have allowed the fabrication of appropriate substrates and the study of cell-substrate interactions. In this review we discuss the methods currently available for nanoscale patterning and their merits, as well as techniques for controlling the surface chemistry of materials at the nanoscale without changing the nanotopography and the possibility of truly characterizing the surface chemistry at the nanoscale. We then discuss the current knowledge of how a cell can interact with a substrate at the nanoscale and the effect of size, morphology, organization and separation of nanofeatures on cell response. Moreover, cell-substrate interactions are mediated by the presence of proteins adsorbed from biological fluids on the substrate. Many questions remain on the effect of nanotopography on protein adsorption. We review papers related to this point. As all these parameters have an influence on cell response, it is important to develop specific studies to point out their relative influence, as well as the biological mechanisms underlying cell responses to nanotopography. This will be the basis for future research in this field. An important topic in tissue engineering is the effect of nanoscale topography on bacteria, since cells have to compete with bacteria in many environments. The limited current knowledge of this topic is also discussed in the light of using topography to encourage cell adhesion while limiting bacterial adhesion. We also discuss current and prospective applications of cell-surface interactions on the nanoscale. Finally, based on questions raised previously that remain to be solved in the field, we propose future directions of research in materials science to help elucidate the relative influence of the physical and chemical aspects of nanotopography on bacteria and cell response with the aim of contributing to the development of nanobiotechnologies.

Opposite responses of cells and bacteria to micro/nanopatterned surfaces prepared by pulsed plasma polymerization and UV-irradiation.

Chemically and topographically patterned surfaces have high potential as model surfaces for studying cell and bacteria responses to surface chemistry and surface topography at a nanoscale level. In this work, we demonstrated the possibility to combine pulsed plasma polymerization and UV-irradiation to obtain topographical patterns and chemical patterns perfectly controlled at microlateral resolution and sub-micrometer depth level. Biological experiments were conducted using human osteoprogenitor cells and Escherichia coli K12. Proliferation and orientation of cells and bacteria were analyzed and discussed according to the size and the chemistry of the features. This work showed interesting opposite behavior of bacteria compared to eukaryotic cells, in response to the surface chemistry and to the surface topography. This result may be particularly useful on medical implants. From a methodological point of view, it highlighted the importance of working with versatile and well-characterized surfaces before and after sterilization. It also points out the relevance and the necessity of analyzing eukaryotic cell and bacteria adhesion in parallel way.

Effect of ultrasounds on the electrochemical synthesis of polypyrrole, application to the adhesion and growth of biological cells.

In this study, a new way to synthesize polypyrrole films is presented. This original way consists in the electropolymerization of polypyrrole under high frequency ultrasonic irradiation on conductive fluorine-doped tin oxide surfaces. The polypyrrole films obtained are then compared, in terms of chemical structure and morphology, to polypyrrole films synthesized by standard electrochemical methodology. Next, these polymer films are tested as an alternative to biomaterials that are commonly used as cell culture substrates. Thus, the adhesion and growth of osteoblastics cells and microbial cells on polymer-modified surfaces are investigated by using qualitative observation and quantitative tests. These studies proved the non-toxicity of the polymer films for osteoblastic and microbial cells but also a different behaviour of osteoblastic cells and microbial cells with polypyrrole films.

In vivo radiolabel quantification in small-animal models.

Current developments in emission tomography especially designed for small-animal imaging are presented. Adaptations of the human tomography principles take advantage of the smaller field of view to achieve about 2-mm usable resolution. Some evaluations in rat tomography are presented, and the problems of limiting resolution of PET and SPECT systems are discussed. Finally, a new approach that more specifically takes into account the parameters induced by in vivo quantification in rodents is presented.