Rodrigo França

Bio: Rodrigo França is an academic researcher from University of Manitoba. The author has contributed to research in topics: Materials science & Medicine. The author has an hindex of 10, co-authored 27 publications receiving 398 citations. Previous affiliations of Rodrigo França include École Polytechnique & University of Brasília.

Confirmation of X-ray Photoelectron Spectroscopy Peak Attributions of Nanoparticulate Iron Oxides, Using Symmetric Peak Component Line Shapes

Abstract: We use high purity Fe oxide nanoparticles to confirm the Fe 2p X-ray photoemission peak attributions made in our previous study of Fe nanoparticles and the initial stage of their oxidation. To acco...

Use of polyphenols as a strategy to prevent bond degradation in the dentin–resin interface

Abstract: This study evaluated the effect of dentin pretreatment with the polyphenols quercetin and resveratrol on the resin-dentin microtensile bonding strength (μTBS) and collagen fibrils stability of the adhesive interface. Different concentrations (100, 250, 500, or 1,000 μg ml-1 ) of quercetin or resveratrol, or a mixture of quercetin and resveratrol (3:1, 1:1, 1:3; vol:vol), as well as distilled water or 2% chlorhexidine digluconate, were applied to etched dentin. Then, a two-step etch-and-rinse adhesive was applied followed by composite restoration. Measurements of resin-dentin μTBS were made after 1 and 120 d. The stability of collagen fibrils in the hybrid layer was evaluated using transmission electron microscopy. The Student's t-test and two-way factorial anova with Tukey's test were used to analyze the effects of dentin pretreatment and storage time on μTBS values. Comparisons between μTBS measurements made on 1 and 120 d showed that resveratrol had the best performance, with significantly higher μTBS values after 120 d for all concentrations of resveratrol tested. Quercetin pretreatment resulted in a significant rise of μTBS when used at concentrations of 100 and 500 μg ml-1 . Quercetin + resveratrol at the ratio of 1:1 performed better than when used at ratios of either 3:1 or 1:3. Resveratrol might represent a potential approach to achieve desirable bonding stability and reduce the frequent replacement of composite restorations.

Nanoscale surface characterization of biphasic calcium phosphate, with comparisons to calcium hydroxyapatite and β-tricalcium phosphate bioceramics.

Abstract: Objectives It is our aim to understand the mechanisms that make calcium phosphates, such as bioactive calcium hydroxyapatite (HA), and biphasic calcium (BCP) and β-tricalcium (β-TCP) phosphates, desirable for a variety of biological applications, such as the filling of bone defects. Methods Here, we have characterized these materials by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and laser granulometry. Results SEM shows clearly that BCP is a matrix made of macro-organized microstructure, giving insight to the specially chosen composition of the BCP that offers both an adequate scaffold and good porosity for further bone growth. As revealed by laser granulometry, the particles exhibit a homogeneous size distribution, centered at a value somewhat larger than the expected 500 μm. XPS has revealed the presence of adventitious carbon at all sample surfaces, and has shown that Ca/P and O/Ca ratios in the outer layers of all the samples differ significantly from those expected. A peak-by-peak XPS comparison for all samples has revealed that TCP and BCP are distinct from one another in the relative intensities of their oxygen peaks. The PO 3 - / PO 2 - and CaOH+/Ca+ TOF-SIMS intensity ratios were used to distinguish among the samples, and to demonstrate that the OH- fragment, present in all the samples, is not formed during fragmentation but exists at the sample surface, probably as a contaminant. Conclusions This study provides substantial insight into the nanoscale surface properties of BCP, HA and β-TCP. Further research is required to help identify the effect of surfaces of these bioceramics with proteins and several biological fluids. Clinical relevance The biological performance of implanted synthetic graft bone biomaterials is strongly influenced by their nanosurface characteristics, the structures and properties of the outer layer of the biomaterial.

In vitro biocompatibility assessment of functionalized magnetite nanoparticles: Biological and cytotoxicological effects

Abstract: In the biomedical field, nanomaterials have the potential for use in the targeted delivery of drugs in the human body and in the diagnosis and therapy of certain dis- eases. In the category of targeted delivery, magnetite (Fe3O4) nanoparticles have received much attention. As with any sim- ilar new therapy, when such nanoparticles are functionalized with chemical groups designed to permit the specific attach- ment of drugs, cytotoxicological testing is necessary before moving to animal models. Here, we consider several vari- ously functionalized magnetite nanoparticles, including those prepared with (1) a monolayer of oleic acid (Fe3O4@OA), which is subsequently converted to (2) a shell of amine-con- taining silane (Fe3O4@NH2), (3) a shell of silica (Fe3O4@SiO2), and (4) a shell of amine-containing silane over a shell of silica (Fe3O4@SiO2@NH2). These latter three functionalities

The effect of ethylene oxide sterilization on the surface chemistry and in vitro cytotoxicity of several kinds of chitosan

Abstract: The surfaces of three chitosan samples, differing only in their degrees of deacetylation and of carboxyethyl chitosan were chemically characterized by X-ray photoelec- tron spectroscopy, time-of-flight secondary ion mass spec- troscopy, X-ray diffraction, and Fourier transform infrared, both before and after sterilization with ethylene oxide. Unex- pected elemental ratios suggest that surface chemical modifi- cation occurred during the processing of the original chitin, with further surface modification on subsequent sterilization, despite previous reports to the contrary. Cell viability was evaluated by direct contact methyl thiazole tetrazolium and lactate dehydrogenase assays between the chitosan particles and A549 human epithelial cells, which demonstrated that the modifications incurred on sterilization are reflected in bio- compatibility changes. All the samples were found to be bio- compatible and nontoxic before sterilization and remained so subsequently. V C

Stability of chitosan-a challenge for pharmaceutical and biomedical applications.

Abstract: Chitosan—one of the natural multifunctional polymers—due to its unique and versatile biological properties is regarded as a useful compound in medical and pharmaceutical technology. Recently, considerable research effort has been made in order to develop safe and efficient chitosan products. However, the problem of poor stability of chitosan-based systems restricts its practical applicability; thus, it has become a great challenge to establish sufficient shelf-life for chitosan formulations. Improved stability can be assessed by controlling the environmental factors, manipulating processing conditions (e.g., temperature), introducing a proper stabilizing compound, developing chitosan blends with another polymer, or modifying the chitosan structure using chemical or ionic agents. This review covers the influence of internal, environmental, and processing factors on the long-term stability of chitosan products. The aim of this paper is also to highlight the latest developments which enable the physicochemical properties of chitosan-based applications to be preserved upon storage.

Unification of catalytic water oxidation and oxygen reduction reactions: amorphous beat crystalline cobalt iron oxides.

Abstract: Catalytic water splitting to hydrogen and oxygen is considered as one of the convenient routes for the sustainable energy conversion. Bifunctional catalysts for the electrocatalytic oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are pivotal for the energy conversion and storage, and alternatively, the photochemical water oxidation in biomimetic fashion is also considered as the most useful way to convert solar energy into chemical energy. Here we present a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and further utilize these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction. Notably, the amorphous cobalt iron oxide produces superior catalytic activity over the crystalline one under photochemical and electrochemical water oxidation and oxygen reduction conditions.