Avaliação do uso de filme híbrido com deposição de titânio em substrato de aço inoxidável AISI 316L para potencial aplicação como biomaterial

Os biomateriais metálicos são os materiais mais utilizados, devido às excelentes propriedades mecânicas quando comparados a outros materiais, como os cerâmicos e poliméricos. Dentre os metais mais aplicados em implantes, destacam-se os aços inoxidáveis ASTM F138, AISI 316L e o AISI 304L, além do titânio puro e suas ligas. Quando em contato com fluidos corpóreos, os biomateriais devem apresentar biocompatibilidade, especificamente para os biomateriais metálicos, além de não sofrerem degradação precipitadamente, e que não haja liberação de íons e desgaste a tal ponto de induzir processos inflamatórios patológicos. O aço inoxidável usualmente denominado AISI 316L apresenta boas propriedades mecânicas e características de material inerte, sendo amplamente utilizado como biomaterial. Entretanto, a presença do cromo e níquel na liga pode desencadear processos alérgicos e inflamatórios no corpo humano. Além disso, implantes de aço inoxidável podem sofrer o crescimento de uma película de tecido fibroso, já existente devido a micromovimentos que ocorrem na interface biomaterial-tecido e que aumentam o risco de afrouxamento do implante. Revestimentos híbridos orgânicoinorgânicos têm sido utilizados nessa área com intuito de solucionar os problemas de corrosão ocorridos em materiais metálicos. Além de não serem tóxicos para o corpo humano, os filmes orgânicos formados promovem uma excelente adesão sobre substratos metálicos, podendo atuar efetivamente como um agente de acoplamento de partículas bioativas. Torna-se promissor o emprego de revestimentos híbridos orgânicos-inorgânicos, não somente pela proteção anticorrosiva, mas também para favorecer a adesão e proliferação celular, aprimorando a biocompatibilidade do metal, podendo, deste modo, minimizar efeitos negativos de implantes cirúrgicos em seres humanos. A utilização de revestimentos híbridos orgânico-inorgânicos obtidos por sol-gel, bem como a deposição de filmes finos por magnetron sputtering para a proteção superficial e melhora de propriedades biocompatíveis de substratos metálicos, mostrou-se uma alternativa eficaz. Nesse contexto, o objetivo deste estudo é obter e caracterizar diferentes filmes híbridos à base dos precursores alcóxidos 3-(trimetóxisililpropil)metacrilato (MAP) e tetraetóxisilano (TEOS) com deposição de titânio por magnetron sputtering em substrato de aço inoxidável AISI 316L para potencial aplicação como biomaterial. As amostras foram preparadas em quatro variações: sendo FH a amostra com uma aplicação e FH_2 a amostra contendo duas aplicações superficiais de filme híbrido a base de MAP e TEOS, as amostras FH_Ti10 e FH_Ti20 receberam uma aplicação de filme híbrido e posterior deposição de titânio por magnetron sputtering por 10 e 20 minutos respectivamente. Dessa forma, as superfícies das amostras foram estudadas por meio de microscopia eletrônica de varredura (MEV) com mapeamento por espectroscopia de energia dispersiva (EDS) e análise da rugosidade. Também foi avaliada a molhabilidade dos filmes por medidas do ângulo de contato, além do comportamento eletroquímico das amostras em solução de fluido corpóreo simulado (SBF) por potencial de circuito aberto (OCP), polarização potenciodinâmica e espectroscopia de impedância eletroquímica (EIE). As propriedades biocompatíveis foram analisadas por ensaios de viabilidade celular e citotoxicidade, utilizando os resultados obtidos por redução de Tetrazólio (MTT), liberação da enzima Lactato Desidrogenase (LDH), além da avaliação qualitativa da adesão celular por MEV e microscopia de fluorescência. Constatou-se que as amostras contendo uma aplicação de filme híbrido tiveram suas propriedades melhoradas em todos os quesitos quando comparadas à amostra sem revestimento. A amostra FH se mostrou bem aderido ao substrato e com desempenho eletroquímico significativamente superior às demais amostras.Além disso, baseado nos resultados obtidos nesta pesquisa, pode-se afirmar que o revestimento MAP e TEOS, nos parâmetros da amostra FH, ofereceram um ambiente biocompatível para células-tronco mesenquimais. Portanto, a utilização de filmes híbridos a base de MAP e TEOS aplicados em substratos de aço inoxidável 316L pode ser indicada para a aplicação em biomateriais. Em contrapartida, as amostras contendo a deposição de titânio por magnetron sputtering não apresentaram variações expressivas em relação ao substrato e as demais amostras estudadas. Não foi observado melhora nas propriedades do material após deposição de titânio.Metallic biomaterials are the most used due to their excellent mechanical properties when compared to other materials, such as ceramic and polymeric ones. ASTM F138, AISI 316L and AISI 304L stainless steels are among the most used metals in implants, in addition to pure titanium and its ligands. Biomaterials, specifically metallic ones, must be biocompatible and not degrade hastily when in contact with bodily fluids, in addition to not releasing ions and wearing out , which may induce pathological inflammatory processes. Stainless steel so called AISI 316L has good mechanical properties and characteristics of inert material, which is widely used as biomaterial. However, the presence of chromium and nickel in the alloy can trigger allergic and inflammatory processes in the human body. Further, stainless steel implants can undergo the growth of a thin film of fibrous tissue, which already exists due to micromovements that occur at the biomaterial-tissue interface and increase the risk of loosening the implant. Hybrid organic-inorganic coatings have been used in this area in order to solve the corrosion problems that occur in metallic materials. Besides not being toxic to the human body, formed organic films promote excellent adhesion on metallic substrates, and can act effectively as a coupling agent for bioactive particles. The use of organic-inorganic hybrid coatings is promising, not only for anti-corrosion protection, but also to favor cell adhesion and proliferation, because they improve the biocompatibility of the metal and minimize the negative effects of surgical implants in humans. The use of organic-inorganic hybrid coatings obtained by sol-gel, as well as the deposition of thin films by magnetron sputtering for surface protection and improvement of biocompatible properties of metallic substrates, proved to be an effective alternative. Within this context, the aim of this study is to obtain and characterize different hybrid films based on the alkoxide precursors 3-(trimethoxysilylpropyl)methacrylate (MAP) and tetraetoxysilane (TEOS), with titanium deposition by magnetron sputtering on AISI 316L stainless steel substrate for potential application as biomaterial. The samples were prepared in four variations: the sample with one application (FH) and the sample containing two superficial applications of hybrid film based on MAP and TEOS (FH_2), samples FH_Ti10 and FH_Ti20 received an application of hybrid film and later deposition of titanium by magnetron sputtering for 10 and 20 minutes respectively. Thus, the surfaces of the samples were studied using scanning electron microscopy (SEM) with mapping by energy-dispersive X-ray spectroscopy (EDS) and the evaluation of surface roughness. The hydrophobicity of the films was also evaluated by contact angle measurements. Electrochemical behavior of the samples in simulated body fluid solution (SBF) was performed by open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Biocompatible properties were analyzed by cell viability and cytotoxicity tests, using the results obtained by reducing Tetrazolium (MTT) and release of Lactate Dehydrogenase (LDH). Cell adhesion was qualitatively assessed by SEM and fluorescence microscopy. The samples containing a hybrid film application had improved properties in all aspects when compared to the sample without coating. The film proved to be well adhered to the substrate and its electrochemical performance is significantly superior to the other samples. An excellent behavior was observed in terms of cell viability and adhesion. Therefore, the use of hybrid films based on MAP and TEOS applied on 316L stainless steel substrates can be indicated for application in biomaterials. However, the samples containing the titanium deposition by magnetron sputtering did not show significant variations in relation to the substrate and the other studied samples. There was no improvement in the properties of the material after titanium deposition

Obtainment and characterization of a silicon alkoxides-based coating applied to a substrate of stainless steel 316L for use in biomaterials

The silicon alkoxides-based coating is an alternative to control the release of cytotoxic ions through metal implants. This study evaluated the influence of the number of layers of a hybrid coating on the surface of austenitic stainless steel AISI 316L on the corrosion resistance. This coating was produced from the precursors of silicon alkoxides 3-(trimethoxysilyl)propyl methacrylate (MAP) and tetraethoxisylane (TEOS) obtained by sol-gel process, and easily applied by dip-coating. Results indicated that a single layer of coating in the substrate showed a better protection than two layers. This single layer developed by the combination of the precursors TEOS-MAP was enough to create a compact and uniform film with good adherence to AISI 316L and higher electrochemical development. A single layer of TEOS-MAP coating is more adequate as a protective coating for the AISI 361L than the sample subjected to two layers and the non-coated substrate, because this film ensures its integrity in an aggressive environment

Effect of tetraethoxy-silane (TEOS) amounts on the corrosion prevention properties of siloxane-poly(methyl methacrylate) hybrid coatings on galvanized steel substrates

Siloxane-poly(methyl methacrylate) (PMMA) organic-inorganic hybrid coatings were deposited on galvanized steel by the dip-coating sol-gel technique. Anticorrosion properties, as well as the morphological, surface and structural features were studied. Hybrid coatings were synthesized from tetraethoxy-silane (TEOS) and methyl methacrylate (MMA) as inorganic and organic phases, respectively, linked by 3-metacriloxypropyl-trimethoxysilane (TMSM) as a coupling agent. The MMA/TMSM ratio was kept constant, whereas the four TEOS/TMSM ratios were varied. The characterization of coatings was assessed using several techniques such as Scanning Electronic Microscopy (SEM), Contact Angle, Fourier Transform Infrared (FT-IR), Open Circuit Polarization (OCP), Atomic Force Microscopy (AFM) and Electrochemical Impedance Spectroscopy measurements (EIS). The EIS results, which were obtained for the hybrid coatings, were discussed based on an electrical equivalent circuit used to adjust the experimental data. The results showed that the increasing the TEOS content caused increase in coating thickness, increased in the surface roughness and increased in the surface hydrophobicity. The film with the highest TEOS content presented the best electrochemical performance, more effective in protecting against corrosion

Effect of concentrations of plasticizers on the sol-gel properties developed from alkoxides precursors

Coatings developed through sol-gel method is presented as an interesting replacement to chromium coating. Sol-gel method present advantages as high purity and excellent distribution of the components. The objective of this work is to synthesize and characterize a film obtained by sol-gel route. The film was prepared with 3-(trimethoxysilylpropyl) methacrylate (TMSPMA), tetraethoxysilane (TEOS) and cerium nitrate, using water and ethanol as solvents. Polyethyleneglycol (PEG) plasticizer was added at four different concentrations. The sol was characterized by techniques of viscosity, thermogravimetric analysis (TGA), X-ray diffraction (XRD) nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR). The results showed that tetrafunctional alkoxides condensation was retarded by the plasticizer, forming a compact film. The film with 20 g.L-1 of PEG showed the best electrochemical behavior

Effect of tetraethoxy-silane (TEOS) amounts on the corrosion prevention properties of siloxane-poly(methyl methacrylate) hybrid coatings on galvanized steel substrates

Siloxane-poly(methyl methacrylate) (PMMA) organic-inorganic hybrid coatings were deposited on galvanized steel by the dip-coating sol-gel technique. Anticorrosion properties, as well as the morphological, surface and structural features were studied. Hybrid coatings were synthesized from tetraethoxy-silane (TEOS) and methyl methacrylate (MMA) as inorganic and organic phases, respectively, linked by 3-metacriloxypropyl-trimethoxysilane (TMSM) as a coupling agent. The MMA/TMSM ratio was kept constant, whereas the four TEOS/TMSM ratios were varied. The characterization of coatings was assessed using several techniques such as Scanning Electronic Microscopy (SEM), Contact Angle, Fourier Transform Infrared (FT-IR), Open Circuit Polarization (OCP), Atomic Force Microscopy (AFM) and Electrochemical Impedance Spectroscopy measurements (EIS). The EIS results, which were obtained for the hybrid coatings, were discussed based on an electrical equivalent circuit used to adjust the experimental data. The results showed that the increasing the TEOS content caused increase in coating thickness, increased in the surface roughness and increased in the surface hydrophobicity. The film with the highest TEOS content presented the best electrochemical performance, more effective in protecting against corrosion

Effect of concentrations of plasticizers on the sol-gel properties developed from alkoxides precursors

Abstract Coatings developed through sol-gel method is presented as an interesting replacement to chromium coating. Sol-gel method present advantages as high purity and excellent distribution of the components. The objective of this work is to synthesize and characterize a film obtained by sol-gel route. The film was prepared with 3-(trimethoxysilylpropyl) methacrylate (TMSPMA), tetraethoxysilane (TEOS) and cerium nitrate, using water and ethanol as solvents. Polyethyleneglycol (PEG) plasticizer was added at four different concentrations. The sol was characterized by techniques of viscosity, thermogravimetric analysis (TGA), X-ray diffraction (XRD) nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR). The results showed that tetrafunctional alkoxides condensation was retarded by the plasticizer, forming a compact film. The film with 20 g.L-1 of PEG showed the best electrochemical behavior