The MATH test. A three-phase assay?

This study aimed to investigating the possible interference caused by glass test tubes on the quantification of bacterial adhesion to hydrocarbons by the MATH test. The adhesion of four bacteria to hexadecane and to glass test tubes was evaluated employing different suspending polar phases. The role of the ionic strength of the polar phase regarding adhesion to glassware was investigated. Within the conditions studied, Gram-positive bacteria adhered to both the test tube and the hydrocarbon regardless of the polar phase employed; meanwhile, Escherichia coli ATCC 25922 did not attach to either one. The capacity of the studied microorganisms to adhere to glassware was associated with their electron-donor properties. The ionic strength of the suspending media altered the patterns of adhesion to glass in a strain-specific manner by defining the magnitude of electrostatic repulsion observed between bacteria and the glass surface. This research demonstrated that glass test tubes may interact with suspended bacterial cells during the MATH test under specific conditions, which may lead to overestimating the percentage of adhesion to hydrocarbons and, thus, to erroneous values of cell surface hydrophobicity.

Surface treatments of the zirconia-reinforced lithium disilicate ceramic in the adhesion to the resin cement

Abstract This study verified the effect of surface treatments of the zirconia-reinforced lithium disilicate ceramic bonded to resin cement. Ceramic blocks were divided according to treatments (n=10): FA+SRX (Fluoric acid + silane RX), FA+MDP (Fluoric acid + MDP), FA+SCF+MDP (Fluoric acid + silane CF + MDP), FA+MEP (Fluoric acid + MEP), and MEP (Self-etch primer). Resin cement cylinders were made in the ceramic blocks, photoactivated with 1,200 mW/cm² for 40s, stored in water at 37°C for 24h, and evaluated by the microshear strength test, optical failure descriptive analysis (%), surface characterization (SEM) and contact angle (Goniometer). Other samples were submitted to 10,000 thermocycles between 5°C and 55°C. Bond strength data were submitted to two-way ANOVA and Tukey's test. Contact angle to one-way ANOVA and Games-Howell's test (5%). At 24h, MEP showed higher bond strength, and FA+SRX the lower. FA+MDP and FA+SCF+MDP showed similar values and FA+MEP was intermediate. After thermocycling, FA+SCF+MDP, FA+MEP, and MEP showed higher values, and FA+SRX the lower while FA+MDP was intermediate. When the periods were compared, FA+MDP, FA+SCF+MDP, FA+MEP, and MEP showed higher values for 24h while FA+SRX was similar. SEM showed retentive surface and crystal exposure when treated with FA+SCF+MDP. The less retentive surface was obtained with MEP, and the other treatments promoted intermediate irregularities. In conclusion, surface treatment and thermocycling promoted different values of adhesive strength and contact angle in a zirconia-reinforced lithium silicate ceramic. Failures were predominantly adhesive, and the ceramic surface was characterized by different levels of roughness and selective exposure of crystals.

Resumo O objetivo neste estudo foi verificar o efeito de tratamentos de superfície da cerâmica de dissilicato de lítio reforçada com zircônia fixada ao cimento resinoso. Os blocos cerâmicos foram separados de acordo com os tratamentos (n=10): AF+SRX (ácido fluorídrico + silano), AF+MDP (ácido fluorídrico + MDP), AF+SCF+MDP (ácido fluorídrico + silano + MDP), AF+MEP (Ácido fluorídrico + MEP) e MEP (Primer auto condicionante). Cilindros de cimento resinoso foram confeccionados em cada bloco cerâmico, foto ativados com 1.200 mW/cm² por 40 segundos, armazenados em água a 37°C por 24 horas e avaliados pelo teste de resistência ao micro cisalhamento, falha por análise descritiva em microscopia óptica (%), caracterização da superfície por imagens MEV e ângulo de contato (Goniômetro). Outras amostras foram submetidas a 10.000 ciclos térmicos (5° e 55°C). Os dados de resistência de união foram submetidos a ANOVA dois fatores e teste de Tukey (5%). Ângulo de contato com ANOVA um fator e teste de Games-Howell (5%). Em 24 horas, MEP apresentou maior resistência de união e AF+S a menor. AF+MDP e AF+SCF+MDP apresentaram valores similares e AF+MEP foi intermediário. Após a ciclagem térmica, AF+SCF+MDP, AF+MEP e MEP apresentaram valores maiores e AF+SRX o menor enquanto AF+MDP foi intermediário. Quando comparados os períodos, AF+MDP, AF+SCF+MDP, AF+MEP e MEP apresentaram valores maiores em 24 horas enquanto AF+SRX foi similar. MEV mostrou superfície mais retentiva e exposição de cristais quando tratada com AF+SCF+MDP. A superfície menos retentiva foi obtida com MEP, e os demais tratamentos promoveram irregularidades de superfície intermediárias. Conclui-se que o tratamento superficial e a termociclagem promoveram diferentes valores de resistência adesiva e ângulo de contato em cerâmica de silicato de lítio reforçada com zircônia. As falhas foram predominantemente adesivas, e a superfície cerâmica foi caracterizada com diferentes níveis de rugosidade e exposição seletiva de cristais.

The use of pracaxi oil collector in the selective flotation of xenotime from silicates.

Rare earth elements have played a key role in technological advancement, attracting great visibility in the global commodity market. Xenotime, a heavy rare earth resource (YPO4), can be found associated with granitic rocks, as in the Pitinga deposit, located in the Brazilian Amazon region, where the main gangue minerals are quartz, microcline and albite. This research investigates the application of a new collector produced from pracaxi oil, an Amazon oil abundant in Brazil, in the selective flotation between xenotime and its main gangue minerals. The study conducted the synthesis and characterization of the collector, the chemical, mineralogical and surface characterization of minerals, as well as the evaluation of collector adsorption and flotability via microflotation tests, zeta potential measurements, surface tension determination and XRD, WDXRF, ICP-MS, FTIR and XPS analyses. The pracaxi collector was found to be mainly composed of oleic acid (56.2%), linoleic acid (14.1%) and behenic acid (10.6%), in addition to exhibiting a critical micelle concentration (CMC) of approximately 150 mg/L. Microflotation tests indicated that the best condition for selective recovery of xenotime occur at alkaline condition (pH 9.0), presenting selectivity of approximately 90% with collector concentration of 10.0 mg/L. The zeta potential data confirmed a selective adsorption of pracaxi collector onto xenotime, with an increase in the surface charge from -30 mV to -68 mV, whereas no significant changes were detected in the silicates. The FTIR spectra showed the appearance of a band at 1545 cm-1 on the surface of the xenotime after collector adsorption, which indicates, along with the zeta potential data, the chemical nature of the adsorption. The presence of small amounts of iron in the lattice structure of silicate gangues can act as an activator, and therefore, may be responsible for the small flotability of these minerals. The performance of the pracaxi oil collector presented in this study indicates the great potential of this Amazonian oil for application in the selective flotation of xenotime ores found in the region.

Surface and Electrical Characterization of Bilayers Based on BiFeO3 and VO2.

Thin films of BiFeO3, VO2, and BiFeO3/VO2 were grown on SrTiO3(100) and Al2O3(0001) monocrystalline substrates using radio frequency and direct current sputtering techniques. To observe the effect of the coupling between these materials, the surface of the films was characterized by profilometry, atomic force microscopy, and X-ray photoelectron spectroscopy. The heterostructures, monolayers, and bilayers based on BiFeO3 and VO2 grew with good adhesion and without delamination or signs of incompatibility between the layers. A good granular arrangement and RMS roughness between 1 and 5 nm for the individual layers (VO2 and BiFeO3) and between 6 and 18 nm for the bilayers (BiFeO3/VO2) were observed. Their grain size is between 20 nm and 26 nm for the individual layers and between 63 nm and 67 nm for the bilayers. X-ray photoelectron spectroscopy measurements show a higher proportion of V4+, Bi3+, and Fe3+ in the films obtained. The homogeneous ordering, low roughness, and oxidation states on the obtained surface show a good coupling in these films. The I-V curves show ohmic behavior at room temperature and change with increasing temperature. The effect of coupling these materials in a thin film shows the appearance of hysteresis cycles, I-V and R-T, which is typical of materials with high potential in applications, such as resistive memories and solar cells.

A global pollutant (PVC-polyvinyl chloride) applied as heavy metal binder from aqueous samples: green principles from synthesis to application.

We have developed a clean route for the modification of polyvinylchloride surface (PVC) with 4-amino-5-hydrazino-1,2,4-triazole-3-thiol molecule. The modification reaction was investigated through Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) analysis. According to our findings, S-H groups are responsible to the molecule attachment and nitrogen atoms are directly involved in metal ion coordination. These results are in agreement with the pseudo-second-order kinetic model, which infers that chemisorption is the main mechanism for metal removal. Adsorption isotherms of Cd(II), Cu(II) and Pb(II) follow the Langmuir model and the results indicated that Ns values are 0.39, 0.52 and 0.15 mmol g-1, respectively. The calculated Ømax values for Cu(II), Pb(II) and Cd(II) were 3.93, 2.95 and 1.13, respectively, indicating that three types of complex are formed depending on the adsorbed species. Therefore, it can be concluded that PVC use as adsorbent is feasible since it requires a simple modification reaction with nontoxic and low-cost solvents.

A Tribological and Ion Released Research of Ti-Materials for Medical Devices.

The increase in longevity worldwide has intensified the use of different types of prostheses for the human body, such as those used in dental work as well as in hip and knee replacements. Currently, Ti-6Al-4V is widely used as a joint implant due to its good mechanical properties and durability. However, studies have revealed that this alloy can release metal ions or particles harmful to human health. The mechanisms are not well understood yet and may involve wear and/or corrosion. Therefore, in this work, commercial pure titanium and a Ti-6Al-4V alloy were investigated before and after being exposed to a simulated biological fluid through tribological tests, surface analysis, and ionic dissolution characterization by ICP-AES. Before exposure, X-ray diffraction and optical microscopy revealed equiaxed α-Ti in both materials and ß-Ti in Ti-6Al-4V. Scratch tests exhibited a lower coefficient of friction for Ti-6Al-4V alloy than commercially pure titanium. After exposure, X-ray photoelectron spectroscopy and surface-enhanced Raman spectroscopy results showed an oxide film formed by TiO2, both in commercially pure titanium and in Ti-6Al-4V, and by TiO and Al2O3 associated with the presence of the alloys. Furthermore, inductively coupled plasma atomic emission spectroscopy revealed that aluminum was the main ion released for Ti-6Al-4V, giving negligible values for the other metal ions.

Production and Characterization of Glutathione-Chitosan Conjugate Films as Systems for Localized Release of Methotrexate.

Cancer is one of the most serious public health problems that affect humanity. Diverse delivery systems of anticancer drugs have been developed to enhance the treatment effectiveness and patient compliance. Thus, drug delivery systems from polymeric films could be an interesting and promising alternative, especially for skin chemotherapeutics. In this work, polymeric films based on glutathione-chitosan conjugates with degrees of thiolation of 4.4%, 5.1% and 7.0% were synthetized by casting-evaporation method and subsequent loading with methotrexate. The surface properties of these films were evaluated by contact angle and spreading rate measurements. The sessile drop methods along with the thermodynamic parameter of work of adhesion were determined using the Young-Dupré semi-empirical model. The in vitro methotrexate release was assessed at a pH of 4.5 and 7.4 simulating physiological conditions. Data from the resulting profiles were fitted to the order one, Higuchi, Peppas-Sahlin and Korsmeyer-Peppas kinetic models. The results suggest a strong relationship between the thiolation degree and hydrophilic surface properties such as contact angle and water spreading rate, whereas the work of adhesion was not significantly affected. Further, these polymer films could control the methotrexate release through diverse mechanisms such as diffusion and relaxation depending on the thiolation degree and the aqueous medium employed. In fact, as thiolation degree increased, the release mechanism shifted from a primary diffusional type towards a predominant relaxation-driven mechanism. These polymer films could be used as modified systems for anticancer local delivery.

Characterization of Enamel After the Use of Oral Hygiene Auxiliaries with Whiteners / Caracterización del esmalte después del uso de auxiliares de higiene bucal con blanqueadores

ABSTRACT The purpose of this study was to evaluate the effect of the use of the combined auxiliaries of oral hygiene with whitening agents on the micro-hardness and micro-morphology of dental enamel. Materials and Methods. 40 human incisors were used and sectioned to obtain 4x4mm samples and divided into four study groups. Group 1: Electric brushing with Toothpaste (BTP); Group 2: Electric brushing with Toothpaste+mouthwash (BTP+MW); Group 3: Electric brushing with Toothpaste+whitening pen (BTP+WP); Group 4: Electric brushing with Toothpaste+mouth wash+whitening pen (BTP+MW+WP). Samples were submitted toVickers micro-hardness test and visualized using scanning electron microscopy (SEM). Results. All groups, with the exception of group 1, showed a decrease in micro- hardness values after applying the treatments (p<0.05). Likewise, when comparing the values after the treatments between the groups, significant statistical differences were found in all of comparisons except for those of groups 2 and 4. SEM images showed changes in the morphology in all the study groups with the exception of group 1. Conclusion. Significant changes such as decrease in micro-hardness as well as in the topography of the enamel surface such as elevations, craters, porosities and etching patterns were founded after the use of the combination of auxiliaries of oral hygiene with whitening agents.

RESUMEN El propósito de este estudio fue evaluar el efecto del uso de los auxiliares de higiene oral combinados con agentes blanqueadores sobre la microdureza y la micro-morfología del esmalte dental. Materiales y métodos. Se utilizaron 40 incisivos humanos y se seccionaron para obtener muestras de 4x4 mm los cuales se dividieron en cuatro grupos de estudio. Grupo 1: cepillado eléctrico con pasta de dientes (BTP); Grupo 2: cepillado eléctrico con pasta dental+enjuague bucal (BTP+MW); Grupo 3: cepillado eléctrico con pasta dental+pluma blanqueadora (BTP+WP); Grupo 4: cepillado eléctrico con pasta dental+enjuague bucal+pluma blanqueadora (BTP+MW+WP). Las muestras fueron analizadas por medio de microdurezaVickers y microscopía electronica de barrido (SEM). Resultados. Todos los grupos, con la excepción del grupo 1, mostraron una disminución en los valores de microdureza después de aplicar los tratamientos (p<0.05). Del mismo modo, al comparar los valores después de los tratamientos entre los grupos, se encontraron diferencias estadísticamente significativas en todas las comparaciones, excepto en las de los grupos 2 y 4. Las imágenes de SEM nos muestran cambios en la morfología en todos los grupos de estudio con la excepción del grupo 1 Conclusión. Cambios significativos como la disminución de la microdureza y los cambios en la topografía de la superficie del esmalte, como elevaciones, cráteres, porosidades y patrones de grabado, se encontraron después del uso de la combinación de auxiliares de la higiene oral con agentes blanqueadores.

Effect of extrinsic pigmentation and surface treatments on biaxial flexure strength after cyclic loading of a translucent ZrO2 ceramic.

OBJECTIVE: To evaluate the influence of extrinsic pigmentation on the biaxial flexural strength and surface topographic of translucent Y-TZP (InCoris TZI - Sirona - USA) subjected to several surface treatments. METHODS: Sintered zirconia discs-shaped specimens (n=120) (ø:12mm; thickness:1.2mm; ISO 6872) were prepared and divided (n=15) according to various factors: "extrinsic pigmentation" (n: without; p: with) and "surface treatments" (C: control - as sintered; A: abraded with silica-coated alumina particles (30µm); G: glazed with a thin film of low-fusing porcelain glaze; GH: glazed and etched with 10% hydrofluoridric acid for 60s. Mechanical cycling (1.2×106 cycles, 200N, 3.8Hz) and flexural strength test (1mm/min - 1000kg cell) were performed. Two-way ANOVA and Tukey's were used for statistical test (α=0.05). Weibull analysis was used to evaluate the strength reliability. Samples were analyzed via (1) an optical profilometer to determine the surface roughness (Ra); (2) an X-ray diffraction (XRD) to evaluate phase transformations; and (3) a SEM equipped with an energy dispersive X-ray spectroscopy (EDX) to elucidate morphological properties and chemical compositions. RESULTS: Regardless of the surface treatment (p=0.5459) (Cn: 560.16MPa; Gn: 573.36MPa; An: 643.51MPa; GHn: 542.94MPa; Cp: 628.04MPa; Gp: 641.90MPa; Ap: 554.47MPa; GHp :602.84MPa) and extrinsic pigmentation (p=0.1280) there was no difference in the flexural strength among the experimental groups. According to the XRD analysis, phase transformations occurred in the An group (t→m) and in Ap group (t→c). Surface roughness was affected by surface treatments (An - p=0.001) and extrinsic pigmentation (Gp - p=0.001). SIGNIFICANCE: The biaxial flexural strength of the tested samples was not affected neither by surface treatments nor by pigmentation, although it can cause phase transformation and promote surface roughness.

Monitoring the Surface Chemistry of Functionalized Nanomaterials with a Microfluidic Electronic Tongue.

Advances in nanomaterials have led to tremendous progress in different areas with the development of high performance and multifunctional platforms. However, a relevant gap remains in providing the mass-production of these nanomaterials with reproducible surfaces. Accordingly, the monitoring of such materials across their entire life cycle becomes mandatory to both industry and academy. In this paper, we use a microfluidic electronic tongue (e-tongue) as a user-friendly and cost-effective method to classify nanomaterials according to their surface chemistry. The chip relies on a new single response e-tongue with association of capacitors in parallel, which consisted of stainless steel microwires coated with SiO2, NiO2, Al2O3, and Fe2O3 thin films. Utilizing impedance spectroscopy and a multidimensional projection technique, the chip was sufficiently sensitive to distinguish silica nanoparticles and multiwalled carbon nanotubes dispersed in water in spite of the very small surface modifications induced by distinct functionalization and oxidation extents, respectively. Flow analyses were made acquiring the analytical readouts in a label-free mode. The device also allowed for multiplex monitoring in an unprecedented way to speed up the tests. Our goal is not to replace the traditional techniques of surface analysis, but rather propose the use of libraries from e-tongue data as benchmark for routine screening of modified nanomaterials in industry and academy.

Poly(lactic acid) composites based on graphene oxide particles with antibacterial behavior enhanced by electrical stimulus and biocompatibility.

Poly(lactic acid) (PLA) is a biodegradable and biocompatible polyester widely used in biomedical applications. Unfortunately, this biomaterial suffers from some shortcomings related with the absence of both bioactivity and antibacterial capacity. In this work, composites of PLA with either graphene oxide (GO) or thermally reduced graphene oxide (TrGO) were prepared by melt mixing to overcome these limitations. PLA composites with both GO and TrGO inhibited the attachment and proliferation of Escherichia coli and Staphylococcus aureus bacteria depending on the kind and amount of filler. Noteworthy, it is shown that by applying an electrical stimulus to the percolated PLA/TrGO, the antibacterial behavior can be dramatically increased. MTT analysis showed that while all the PLA/GO composites were more cytocompatible to osteoblast-like cells (SaOS-2) than pure PLA, only low content of TrGO was able to increase this property. These tendencies were related with changes in the surface properties of the resulting polymer composites, such as polarity and roughness. In this way, the addition of GO and TrGO into a PLA matrix allows the development of multifunctional composites for potential applications in biomedicine. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1051-1060, 2018.

In Vitro Cytotoxicity Test and Surface Characterization of CoCrW Alloy in Artificial Saliva Solution for Dental Applications

Abstract In order to evaluate its application as a dental prosthesis material, a CoCrW alloy was subjected to in vitro cytotoxicity test, surface characterization and electrochemical studies performed in artificial saliva and 0.15 mol.L-1 NaCl medium. The used techniques were: anodic polarization curves, chronoamperometric measurements, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) analysis and X-ray photoelectron spectroscopy (XPS). Cytotoxicity test was also performed. The electrochemical behavior of CoCrW alloy was compared in both studied media, from corrosion potential (Ecorr) to a 600 mV anodic overvoltage. From the electrochemical measurements it was observed that the CoCrW alloy in both media presents only generalized corrosion. SEM and EDS analysis showed that the alloy presents carbide niobium and silicon and manganese oxides as nonmetallic inclusions. XPS results indicated that cobalt does not significantly contribute to the passivating film formation. Cytotoxicity test showed no cytotoxic character of CoCrW alloy. These results suggest that the CoCrW alloy can be used as biomaterial to be applied as prosthesis in dental implants.

Resumo Estudos eletroquímicos, caracterização de superfície e teste de citotoxicidade in vitro foram realizados da liga CoCrW em meios de saliva artificial e NaCl 0,15 mol.L-1, com o objetivo de avaliar a sua aplicação como material de prótese dentária. Foram usadas como técnicas, curvas de polarização anódica, medidas cronoamperométricas, espectroscopia de impedância eletroquímica (EIE), microscopia eletrônica de varredura (MEV), espectroscopia por energia dispersiva de raios X (EDS) e espectroscopia fotoeletrônica de raios X (XPS). O teste de citotoxicidade também foi realizado. O comportamento eletroquímico da liga CoCrW foi comparado nos dois meios estudados desde o potencial de corrosão (Ecorr) até uma sobretensão anódica de 600 mV. Foi observado, a partir de medidas eletroquímicas, que a liga CoCrW se encontra passivada em uma ampla faixa de potencial e que a sobretensões mais elevadas apresenta apenas corrosão generalizada nos dois meios. Análises por MEV e EDS mostraram que a liga apresenta inclusões não metálicas de carbeto de nióbio, de óxidos de silício e de manganês. Os resultados de XPS indicaram que o cobalto não contribui significativamente para a formação do filme passivo. O teste de citotoxicidade mostrou que a liga CoCrW não se apresenta citotóxica. Estes resultados sugerem que a liga estudada pode ser usada como biomaterial a ser aplicado como prótese sobre implantes dentários.

Effects of chemical composition on the corrosion of dental alloys

The aim of this study was to determine the effect of the oral environment on the corrosion of dental alloys with different compositions, using electrochemical methods. The corrosion rates were obtained from the current-potential curves and electrochemical impedance spectroscopy (EIS). The effect of artificial saliva on the corrosion of dental alloys was dependent on alloy composition. Dissolution of the ions occurred in all tested dental alloys and the results were strongly dependent on the general alloy composition. Regarding the alloys containing nickel, the Ni-Cr and Ni-Cr-Ti alloys released 0.62 mg/L of Ni on average, while the Co-Cr dental alloy released ions between 0.01 and 0.03 mg/L of Co and Cr, respectively.The open-circuit potential stabilized at a higher level with lower deviation (standard deviation: Ni-Cr-6Ti = 32 mV/SCE and Co-Cr = 54 mV/SCE). The potenciodynamic curves of the dental alloys showed that the Ni-based dental alloy with >70 wt% of Ni had a similar curve and the Co-Cr dental alloy showed a low current density and hence a high resistance to corrosion compared with the Ni-based dental alloys. Some changes in microstructure were observed and this fact influenced the corrosion behavior for the alloys. The lower corrosion resistance also led to greater release of nickel ions to the medium. The quantity of Co ions released from the Co-Cr-Mo alloy was relatively small in the solutions. In addition, the quantity of Cr ions released into the artificial saliva from the Co-Cr alloy was lower than Cr release from the Ni-based dental alloys.

O objetivo deste estudo foi determinar o efeito do ambiente bucal na corrosão de diferentes ligas odontológicas, utilizando métodos eletroquímicos. Os índices de corrosão foram obtidos por meio das curvas de corrente-potencial e impedância eletroquímica (EIS). O efeito de saliva artificial na corrosão de ligas odontológicas foi dependente da composição. A dissolução dos íons ocorreu em todas as amostras e os resultados foram dependentes da composição da liga. Algumas mudanças na microestrutura foram observadas durante o estudo e influenciou o comportamento corrosivo das ligas investigadas. As ligas de Ni-Cr e Ni-Cr-Ti libertaram quantidade de 0,62 mg/L de íons Ni enquanto a liga de Co-Cr liberou entre 0,01 e 0,03 mg/L. As curvas potenciodinâmicas das ligas odontológicas mostraram que as ligas a base >70 wt% de Ni obtiveram curvas similares e a liga de Co-Cr apresentou a menor densidade de corrente e em consequência uma resistência alta a corrosão quando comparada as ligas à base de Ni. A baixa resistência à corrosão também levou a maior libertação de íons de níquel para o meio e a quantidade de Co liberado pela liga de Co-Cr-Mo foi relativamente pequena nas soluções. As quantidades de Cr liberada na saliva artificial pela liga de Co-Cr foi menor que a libertação de Cr pela liga à base de Ni.

Estudo das características físico-químicas e biológicas pela adesão de osteoblastos em superfícies de titânio modificadas pela nitretação em plasma / Study of physical-chemical and osteoblast adhesion characteristics of titanium surfaces modified by plasma nitriding

INTRODUÇÃO: Superfícies de titânio modificadas por diferentes métodos foram estudadas com base nos parâmetros físicos e químicos de caracterização superficial e sua influência no comportamento de células pré-osteoblásticas (MC3T3) in vitro. MÉTODOS: Discos de titânio comercialmente puro grau II foram submetidos a três métodos de modificação de superfície (polimento, nitretados em plasma em configuração planar e gaiola catódica). As diferentes superfícies foram caracterizadas para observar o efeito do processamento na estrutura da camada superficial, na rugosidade e molhabilidade. Ensaios de adesão e proliferação celular usando linhagens de células pré-osteoblásticas MC3T3 foram realizados para avaliar o efeito das novas superfícies no comportamento celular in vitro. RESULTADOS: Os resultados demonstraram que a nitretação em plasma na configuração de gaiola catódica produz superfícies mais rugosas (p<0,02) e com menores ângulos de contato com a água. CONCLUSÕES: A adesão celular é maior nas superfícies mais rugosas do que nas superfícies polidas (p<0,05) e reagem de modo diferente a composição química do substrato e à topografia da superfície.

PURPOSE: The aim of this study was to evaluated the physico-chemical properties of different titanium surfaces modified by means of low temperature plasma nitridind on rat osteoblast cell adhesion and proliferation. METHODS: Pure Titanium discs grade II was submitted to three different surface preparations (polishing, glow discharge plasma nitriding in planar and cathodic cage configurations). Surface parameters as roughness, wettability and chemichal composition was determined to compare influency of gas mixture on the modified surface material properties. Cellular morphology was observed by scanning electron microscopy. To evaluate the effect of the surface on cellular response, osteoblast cells (MC3T3) adhesion and proliferation was quantified and data analised by Kruskal-Wallis and Friedman statistical tests. RESULTS: plasma nitriding discs shows rougher surfaces( p<0,02) in cathodic cage configuration and lower contact angle values. MC3T3 cells attached on rough surfaces produced by cathodic cage configuration was statistically significant p<0,05 compared to polished discs. CONCLUSIONS: Glow discharge plasma nitriding improve titanium surface roughness and wettability. MC3T3 cell adhesion behavior is related to substrate chemical composition and topography.