Micro-arc oxidation as a tool to develop multifunctional calcium-rich surfaces for dental implant applications

Titanium (Ti) is commonly used in dental implant applications. Surface modification strategies are being followed in last years in order to build Ti oxide-based surfaces that can fulfill, simultaneously, the following requirements: induced cell attachment and adhesion, while providing a superior corrosion and tribocorrosion performance. In this work micro-arc oxidation (MAO) was used as a tool for the growth of a nanostructured bioactive titanium oxide layer aimed to enhance cell attachment and adhesion for dental implant applications. Characterization of the surfaces was performed, in terms of morphology, topography, chemical composition and crystalline structure. Primary human osteoblast adhesion on the developed surfaces was investigated in detail by electronic and atomic force microscopy as well as immunocytochemistry. Also an investigation on the early cytokine production was performed. Results show that a relatively thick hybrid and graded oxide layer was produced on the Ti surface, being constituted by a mixture of anatase, rutile and amorphous phases where calcium (Ca) and phosphorous (P) were incorporated. An outermost nanometric-thick amorphous oxide layer rich in Ca was present in the film. This amorphous layer, rich in Ca, improved fibroblast viability and metabolic activity as well as osteoblast adhesion. High-resolution techniques allowed to understand that osteoblasts adhered less in the crystalline-rich regions while they preferentially adhere and spread over in the Ca-rich amorphous oxide layer. Also, these surfaces induce higher amounts of IFN-γ cytokine secretion, which is known to regulate inflammatory responses, bone microarchitecture as well as cytoskeleton reorganization and cellular spreading. These surfaces are promising in the context of dental implants, since they might lead to faster osseointegration.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Mechanical Properties of Thin Glassy Polymer Films Filled with Spherical Polymer-Grafted Nanoparticles

It is commonly accepted that the addition of spherical nanoparticles (NPs) cannot simultaneously improve the elastic modulus, the yield stress, and the ductility of an amorphous glassy polymer matrix. In contrast to this conventional wisdom, we show that ductility can be substantially increased, while maintaining gains in the elastic modulus and yield stress, in glassy nanocomposite films composed of spherical silica NPs grafted with polystyrene (PS) chains in a PS matrix. The key to these improvements are (i) uniform NP spatial dispersion and (ii) strong interfacial binding between NPs and the matrix, by making the grafted chains sufficiently long relative to the matrix. Strikingly, the optimal conditions for the mechanical reinforcement of the same nanocomposite material in the melt state is completely different, requiring the presence of spatially extended NP clusters. Evidently, NP spatial dispersions that optimize material properties are crucially sensitive to the state (melt versus glass) of the polymeric material

Polystyrene carbon nanotube nanocomposites

Carbon nanotubes (CNTs) exhibit excellent mechanical, electrical, and magnetic properties as well as nanometer-scale diameter and high aspect ratio, which give them a great deal of attention and have been the focus of extensive research efforts as model systems in nanotechnology. Since CNTs usually agglomerate due to van der Waals forces, it is extremely difficult to disperse and align them in a polymer matrix, which consequently leading to many defect sites in the composites and limiting the efficiency of CNTs on polymer matrices. In this chapter, we focus on recent development in preparation and characterization and also review effective parameters on CNT dispersion in polystyrene carbon nanotube nanocomposites

Development of acrylonitrile-butadiene-styrene composites with enhanced UV stability

Aiming to develop acrylonitrile–butadiene– styrene (ABS) composites with enhanced ultraviolet stability, a series of formulations were prepared by melt compounding and evaluated by different characterization techniques. The influence of rutile titanium dioxide (TiO2) and its combination with furnace carbon black (CB) on the viscoelastic properties of neat ABS was studied by dynamic mechanical analysis. An increase in the glass transition (Tg) dynamics ascribed to the rubbery phase as a function of exposure time was observed. A greater contribution of CB nanoparticles in combination with TiO2 to minimize the modifications on the Tg of the butadienic component was clearly seen. Quasi-static and spectrophotometry results are in good agreement, showing the efficiency of TiO2 submicron particles and CB/TiO2 against photo-oxidative degradation of neat ABS. A different behaviour was observed for modified ABS/TiO2 and ABS/ CB/TiO2 composites with light stabilizers, antioxidants and combinations of them. While the TiO2 efficiency was enhanced by the incorporation of combinations of light stabilizers and antioxidants, poor results were observed for modified ABS/CB/TiO2 composites as a consequence of antagonistic interactions. It was concluded that formulations of ABS/CB/TiO2 with light stabilizers and ultraviolet absorbers are unacceptable for common applications.The authors would like to thank the Portuguese Foundation for the Science and Technology (FCT) and Poliversal-Plasticos e Tecnologia, S.A. for the PhD grant SFRH/BDE/15657/2007

Comparison of fondaparinux with low molecular weight heparin for venous thromboembolism prevention in patients requiring rigid or semi-rigid immobilization for isolated non-surgical below-knee injury

Background: In several small studies, anticoagulant therapy reduced the incidence of venous thromboembolism (VTE) in patients with isolated lower-limb injuries. Objectives: To compare the efficacy and safety of fondaparinux 2.5 mg (1.5 mg in patients with a creatinine clearance between 30 and 50 mL min-1) over nadroparin 2850 anti-factor Xa IU. Patients and Methods: In this international, multicenter, randomized, open-label study, patients with an isolated non-surgical unilateral below-knee injury having at least one additional major risk factor for VTE and requiring, in the Investigator's opinion, rigid or semi-rigid immobilization for 21-45 days with thromboprophylaxis up to complete mobilization received subcutaneously once-daily either fondaparinux or nadroparin. The primary efficacy outcome was the composite of VTE (symptomatic or ultrasonographically detected asymptomatic deep vein thrombosis of the lower limb or symptomatic pulmonary embolism) and death up to complete mobilization. The main safety outcome was major bleeding. Results: We randomized 1349 patients (mean age 46 years): 88.7% had a bone fracture, and 83.8% had a plaster cast fitted (mean duration of immobilization, 34 days). The primary efficacy outcome occurred in 15 of 584 patients (2.6%) in the fondaparinux group and 48 of 586 patients (8.2%) in the nadroparin group (odds ratio, 0.30; 95% confidence interval [CI], 0.15-0.54; P < 0.001). A single major bleed was experienced by fondaparinux-treated patients and none by nadroparin-treated patients. These results were maintained up to the end of follow-up. Conclusions: Fondaparinux 2.5 mg day-1 may be a valuable therapeutic option over nadroparin 2850 anti-FXa IU day-1 for preventing VTE after below-knee injury requiring prolonged immobilization in patients with additional risk factors