XRD and FTIR analysis of Ti–Si–C–ON coatings for biomedical applications

Ti–Si–C–ON films were deposited by DC reactive magnetron sputtering using different partial pressure ratio of oxygen (pO2) and nitrogen (pN2). Compositional analysis revealed the existence of three different growth zones for the films; (I) N/Ti = 2.1 (high atomic ratio) and low oxygen content; (II) 0.76 < N/Ti < 2.1 (intermediate atomic ratio) and (III) N/Ti ≤ 0.12 (low ratio) and high oxygen content. For high N/Ti atomic ratio (N/Ti = 2.1) the XRD pattern exhibits reflections that correspond to a mixture of two different phases: a metallic-like Ti and a fcc NaCl type structure. Its electrical resistivity presents a metallic character and, consequently, has high infrared reflectivity. For the intermediate N/Ti ratio (0.76 < N/Ti < 2.1), the films crystallize in a B1-NaCl crystal structure typical for TiC0.2N0.8. Their FTIR spectra present C–N modes, besides the TiN ones, that indicate a progressive substitution of nitrogen by carbon atoms with increasing oxygen content (and lowering N/Ti ratio). For the highest oxygen content (and lower N/Ti ratio) the presence of the Ti–O–Ti stretching mode shows the formation of highly resistive Ti–O compounds consistent with the semiconductor character of this film. Biofilm formation as well as material cytotoxicity seemed to be related with the presence of the Ti

Development of an injectable system based on elastin-like recombinamer particles for tissue engineering applications

An elastin-like recombinamer (ELR) containing the RGD cell adhesion domain was used to fabricate microparticles by an innovative and affordable process based on the use of superhydrophobic surfaces. Two microparticles types with different crosslinking extents were prepared. The biological response was tested using an osteoblast-like cell line (SaOs-2) performing proliferation and alkaline phosphatase (ALP) quantification tests, as well as assessing cytotoxicity, morphology and cell distribution on the particles. The main goal of the work was the assessment of the in vitro formation of cell-induced microparticle aggregates that could provide indications for the possible formation of an in situ-forming scaffold upon implantation. ELR microparticles have been successfully obtained by deposition of a polymeric solution on bioinspired polystyrene superhydrophobic surfaces and two different crosslinking extents were achieved by controlling the time of exposure to the crosslinker. The crosslinking extent affected swelling behavior and the dynamic mechanical properties of the particles. SaOs-2 morphology, ALP expression, spatial distribution and ability to bind the microparticles together were dependent on the physicochemical properties of the microparticles: the more crosslinked condition was the most favorable for cell proliferation and to form a cell-induced aggregation scaffold, making these particles suitable to be applied in bone tissue engineering

Tribocorrosion of commercially pure titanium in oral simulating environments

According to several studies, commercially pure (cp) titanium presents the required properties for dental applications such as mechanical resistance, low density, corrosion resistance and biocompatibility [1-3]. Also, it is widely accepted that the surface properties of the metallic material will play an essential role in the interaction between implanted materials and tissue. Whatever Ti is used in crowns or implants, a relative displacement between the implant and the adjacent material (gum, bone, porcelain…) might occur, always in the presence of an environment constituted by inorganic and organic species. Therefore, a tribocorrosion system may be formed, and the synergistic effect of wear and corrosion may lead to accelerated failure of the system. Nevertheless, few studies have focused on the tribocorrosion behavior of titanium in oral simulating environments, considering the presence of fluoride solutions and/or bacterial biofilms [4-8]. The aim of this work was to study the effect of sliding wear of cp titanium in the presence of artificial saliva containing different amounts of fluoride. Also, the behavior of the tribocorrosion system when a biofilm is present at the surface of the metallic materials was evaluated. Samples of grade 2 Ti were prepared by grinding using SiC sandpapers till 1200 mesh. Tribocorrosion tests were accomplished in Fusayama’s artificial saliva (AS) containing two different fluoride concentrations: 30 and 227 ppmF-. Open-circuit potential (OCP) was monitored during the entire experiment and electrochemical impedance spectroscopy tests (EIS) were carried out at 50 mV above corrosion potential (Ecorr) at frequencies from 100 KHz to 15.8 mHz, before and after sliding. The sliding tests were carried out using an alumina sphere as counterbody under a normal load of 3 N, an amplitude of 2 mm for 20 min. Results were statistically analyzed at significance level of p < 0.05. Samples were inspected by SEM-EDS and AFM. As shown in fig. 1, the addition of 227 ppmF- to the AS resulted in a higher Ecorr during sliding. However, in the same solution, Ti presents a significantly higher passive current density in the absence of mechanical action. During sliding, third-body particles were produced, and chemical analysis of the solution revealed a significant release of Ti ions. The influence of the presence of bacterial cultures of S.mutans on the corrosion and tribocorrosion behavior of titanium is also discussed.Fundação para a Ciência e a Tecnologia (FCT)Programa Alban - Bolsas de Alto Nível da União Europeia para a América LatinaFlemish Science Foundation.Scientific Research Community on Surface Modification of Material

Metabolomic applications in stem cell research: a review

This review describes the use of metabolomics to study stem cell (SC) characteristics and function, excluding SCs in cancer research, suited to a fully dedicated text. The interest in employing metabolomics in SC research has consistently grown and emphasis is, here, given to developments reported in the past five years. This text informs on the existing methodologies and their complementarity regarding the information provided, comprising untargeted/targeted approaches, which couple mass spectrometry or nuclear magnetic resonance spectroscopy with multivariate analysis (and, in some cases, pathway analysis and integration with other omics), and more specific analytical approaches, namely isotope tracing to highlight particular metabolic pathways, or in tandem microscopic strategies to pinpoint characteristics within a single cell. The bulk of this review covers the existing applications in various aspects of mesenchymal SC behavior, followed by pluripotent and neural SCs, with a few reports addressing other SC types. Some of the central ideas investigated comprise the metabolic/biological impacts of different tissue/donor sources and differentiation conditions, including the importance of considering 3D culture environments, mechanical cues and/or media enrichment to guide differentiation into specific lineages. Metabolomic analysis has considered cell endometabolomes and exometabolomes (fingerprinting and footprinting, respectively), having measured both lipid species and polar metabolites involved in a variety of metabolic pathways. This review clearly demonstrates the current enticing promise of metabolomics in significantly contributing towards a deeper knowledge on SC behavior, and the discovery of new biomarkers of SC function with potential translation to in vivo clinical practice.The authors acknowledge the Portuguese Foundation for Science and Technology (FCT) for co-funding the BIOIMPLANT project (PTDC/BTM-ORG/28835/2017) through the COMPETE2020 program and European Union fund FEDER (POCI-01–0145- FEDER-028835). CSHJ and KR are grateful to the same project for funding their contracts with the University of Aveiro. DSB acknowl- edges the Sociedade Portuguesa de Química and FCT for her PhD grant SFRH/BD/150655/2020. AMG acknowledges the CICECO-Aveiro Institute of Materials project, with references UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Part- nership Agreement. The NMR spectrometer used in this work is part of the National NMR Network (PTNMR) and, partially supported by Infrastructure Project Nº 022161 (co-financed by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC).publishe

An intracellular metabolic signature as a potential donor-independent marker of the osteogenic differentiation of adipose tissue mesenchymal stem cells

This paper describes an untargeted NMR metabolomics study to identify potential intracellular donor-dependent and donor-independent metabolic markers of proliferation and osteogenic differentiation of human adipose mesenchymal stem cells (hAMSCs). The hAMSCs of two donors with distinct proliferating/osteogenic characteristics were fully characterized regarding their polar endometabolome during proliferation and osteogenesis. An 18-metabolites signature (including changes in alanine, aspartate, proline, tyrosine, ATP, and ADP, among others) was suggested to be potentially descriptive of cell proliferation, independently of the donor. In addition, a set of 11 metabolites was proposed to compose a possible donor-independent signature of osteogenesis, mostly involving changes in taurine, glutathione, methylguanidine, adenosine, inosine, uridine, and creatine/phosphocreatine, choline/phosphocholine and ethanolamine/phosphocholine ratios. The proposed signatures were validated for a third donor, although they require further validation in a larger donor cohort. We believe that this proof of concept paves the way to exploit metabolic markers to monitor (and potentially predict) cell proliferation and the osteogenic ability of different donors.publishe

Structural and mechanical properties of Ti–Si–C–ON for biomedical applications

Ti–Si–C–ON films were deposited by DC reactive magnetron sputtering using different partial pressure of oxygen (pO2) and nitrogen (pN2) ratio. Compositional analysis revealed the existence of two different growth zones for the films; one zone deposited under low pO2/pN2 and another zone deposited under high pO2/pN2. The films produced under low pO2/pN2 were deposited at a lower rate and presented a fcc structure, as well as, dense and featureless morphologies. The films deposited with high pO2/pN2, consequently higher oxygen content, were deposited at a higher rate and developed an amorphous structure. The structural changes are consistent with the hardness and Young's modulus evolution, as seen by the significant reduction of the hardness and influence on the Young's modulus by increasing pO2/pN2

Reversible imine crosslinking in waterborne self-healing polymer coatings

Waterborne polymer coatings have the potential to address the environmental concerns associated with solvent based systems. To improve their performance without using volatile organic compounds, we propose a new approach based on reconfigurable covalent crosslinking that provides mechanical resistance and self-healing properties. The new waterborne polymer coatings are based on mixtures of aldehyde- and amine-functionalized polymer nanoparticles (PNPs) that take advantage of the reversibility of imine bonds in the presence of water. Different degrees of functional monomer incorporation (10 % to 40 %) allowed us to balance crosslinking and interdiffusion during film formation, to obtain mechanically robust and solvent resistant films. A clear structure-properties relation was assessed by following the formation of water resulting from amine-aldehyde condensation crosslinking, measured by differential scanning calorimetry. The resulting polymer coatings further show self-healing properties at room temperature, triggered with residual amounts of water and featuring high recovery rates of the mechanical properties. Our mechanically robust waterborne polymer coatings based in imine reversible crosslinking, featuring self-healing in mild conditions, offer excellent prospects for application in smart coating materials.publishe

Nanopartículas de prata : análise dos efeitos anti-biofilme e anti-adesão sobre Candida albicans e Candida glabrata

Os objetivos deste trabalho foram: (1) avaliar o efeito sinergístico de nanopartículas de prata (NP) com Nistatina e Clorexidina contra biofilmes de Candida albicans e Candida glabrata; (2) verificar o efeito das NP na composição da matriz destes biofilmes e (3) investigar a capacidade de adesão a células epiteliais HeLa e a poliestireno de leveduras tratadas com NP. As drogas sozinhas ou em combinação com NP (5 nm) foram aplicadas sobre biofilmes maduros (48 h) e após 24 h de contato a atividade sinergística foi avaliada através da quantificação da biomassa total e por meio da contagem do número de colônias. Após o tratamento com NP, as matrizes dos biofilmes foram extraídas e analisadas em termos de proteínas, carboidratos e DNA. Ainda, leveduras viáveis foram recuperadas e adicionadas tanto às células HeLa quanto aos poços vazios de placas de poliestireno e, após 2 horas de contato, a adesão foi determinada usando violeta cristal. NP combinadas com Nistatina e Clorexidina exibiram atividade anti-biofilme sinergística dependente das espécies e concentrações de drogas usadas. Ainda, NP interferiram na composição da matriz extracelular dos biofilmes e a capacidade de adesão das leveduras viáveis foi significativamente reduzida após tratamento prévio com NP. Esses achados permitem concluir que NP podem contribuir na prevenção ou tratamento da estomatite protética associada à Candida. Entretanto, estudos adicionais são necessários para que estas NP sejam usadas com segurança

Hypercholesterolemia promotes early renal dysfunction in apolipoprotein E-deficient mice

<p>Abstract</p> <p>Background</p> <p>Aging and dyslipidemia are processes which can lead to deleterious consequences to renal function. Therefore, the aim of this study was to determine the effects of both hypercholesterolemia and aging on renal function in mice.</p> <p>Methods</p> <p>Male hypercholesterolemic apolipoprotein E-deficient mice (ApoE, n = 13) and age-matched C57BL/6 control mice (C57, n = 15) were studied at 2 (young) and 8 (adult) month-old. At each time point, animals were placed in metabolic cages for 24 hours to urine volume and urinary creatinine quantification. Blood samples were collected for serum cholesterol, urea and creatinine measurements. Glomerular filtration rate (GFR) was estimated through creatinine clearance determination. Mesangial expansion was evaluated by Periodic Acid Schiff staining, renal fibrosis was determined through Masson's trichrome staining and neuronal nitric oxide synthase (nNOS) expression in the kidney was performed by Western Blotting. To statistical analysis two-way ANOVA followed by Fisher's <it>post hoc </it>test was used.</p> <p>Results</p> <p>Total plasma cholesterol was increased about 5-fold in ApoE mice at both time points compared to C57 animals. At 2-month-old, GFR was already markedly reduced in ApoE compared to C57 mice (187 ± 28 vs 358 ± 92 μL/min, p < 0.05). Adult C57 (-77%) and ApoE (-50%) mice also presented a significant reduction of GFR. In addition, serum urea was significantly increased in young ApoE animals compared to C57 mice (11 ± 1.3 vs 7 ± 0.9 mmol/L, p < 0.01). A significant mesangial expansion was observed at 2-month old ApoE mice compared to C57 mice (35 ± 0.6 vs 30 ± 0.9%, respectively, p < 0.05), which was aggravated at 8-month old animals (40 ± 3 and 35 ± 3%, respectively). Tubulointersticial fibrosis was augmented at both young (17 ± 2%, p < 0.05) and adult (20 ± 1%, p < 0.05) ApoE mice compared to respective C57 age controls (8 ± 1 and 12 ± 2%, respectively). The expression of nNOS was markedly reduced in a time-dependent manner in both strains.</p> <p>Conclusions</p> <p>These data show that both hypercholesterolemia and aging contribute to the loss of renal function in mice.</p