Efeito do processo de esterilização sobre as propriedades de revestimentos híbridos e sobre a diferenciação osteogênica de células-tronco mesenquimais

Revestimentos híbridos silanos têm sido aplicados sobre a liga de Ti6Al4V como forma de melhorar sua resistência à corrosão e sua propriedade de bioatividade. No contexto de funcionalização de superfícies, a introdução de células-tronco em estruturas objetivando o crescimento de novos tecidos tem sido muito estudada, como por exemplo, no processo de osteointegração. No entanto, ao final do desenvolvimento de biomateriais, a escolha do processo de esterilização deve ser cuidadosamente considerada, uma vez que essa pode comprometer as propriedades requeridas para os mesmos. O presente trabalho teve por objetivo avaliar a influência de 3 diferentes processos de esterilização: autoclave a vapor, plasma de peróxido de hidrogênio e óxido de etileno, sobre as propriedades de um revestimento híbrido silano e sobre a diferenciação osteogênica de células-tronco mesenquimais. Para isso, os revestimentos foram obtidos a partir de um sol constituído pelos precursores silanos Tetraetoxisilano (TEOS) e Metiltrietoxisilano (MTES), aplicados sobre o substrato de Ti6Al4V. Para promover a bioatividade, partículas de hidroxiapatita foram dispersas em um segundo revestimento (TEOS/MTES + hidroxiapatita) aplicado sobre o primeiro (TEOS/MTES). Após a esterilização, os revestimentos foram avaliados por microscopia eletrônica de varredura, microscopia de força atômica, perfilometria, molhabilidade e espectroscopia no infravermelho por transformada de Fourier. O comportamento eletroquímico foi avaliado por monitoramento do potencial de circuito aberto e curvas de polarização potenciodinâmicas. A citocompatibilidade para células MG-63 foi avaliada para o revestimento protetivo e a diferenciação osteogênica para o revestimento bioativo aplicado sobre a camada protetiva. Os resultados mostraram que após a esterilização o efeito barreira do revestimento protetivo foi comprometido e isso pode ser associado às modificações superficiais ocasionadas pelos mesmos. Todos os processos de esterilização provocaram modificações morfológicas no revestimento bioativo, aumentando a bioatividade do mesmo. As esterilizações por óxido de etileno e plasma de peróxido de hidrogênio intensificaram a degradação hidrolítica do revestimento bioativo e a partir disso os mesmos apresentaram maiores índices de liberação de silício. Os revestimentos bioativos esterilizados não apresentaram citotoxicidade às células-tronco mesenquimais. O comportamento de adesão, viabilidade e diferenciação osteogênica foi favorecido sobre o revestimento esterilizado por plasma de peróxido de hidrogênio, comportamento oposto ao observado para o revestimento esterilizado por óxido de etileno.Silane hybrid coatings have been applied on the Ti6Al4V alloy as a way to improve their corrosion resistance and their bioactivity properties. In the context of surface functionalization, the introduction of stem cells into structures, aiming at the growth of new tissues, has been much studied as, for example, in the process of osteointegration. However, at the end of the development of biomaterials, the choice of the sterilization process should be carefully considered, once this may compromise the properties required for it. The aim of the present work was to evaluate the influence of three different sterilization processes: steam autoclave, hydrogen peroxide plasma and ethylene oxide, on the protective and bioactive properties of a hybrid silane coating. For this, the coatings were obtained from a sol consisting of the precursor silanes Tetraethoxysilane (TEOS) and precursor Methyltriethoxysilane (MTES), applied on Ti6Al4V. To promote bioactivity, hydroxyapatite particles were dispersed in a second coating (TEOS/MTES + hydroxyapatite) applied on the first (TEOS/MTES). After sterilization, coatings were evaluated by scanning electron microscopy, atomic force microscopy, profilometry, wettability and fourier transform infrared spectroscopy The electrochemical behavior was evaluated by monitoring the open circuit potential and the potentialdynamic polarization curves. The cytocompatibility of MG-63 cells was evaluated for the protective coating and osteogenic differentiation for the bioactive coating applied on the protective layer. The results showed that after sterilization the barrier effect of the protective coating was compromised, and this may be associated with the surface modifications caused by the coating. All sterilization methods caused morphological modifications in the bioactive coating, increasing its bioactivity. Sterilization by ethylene oxide and hydrogen peroxide plasma intensified the hydrolytic degradation of the bioactive coating and from this they showed higher rates of silicon release. Sterilized bioactive coatings did not show cytotoxicity to mesenchymal stem cells. The behavior of adhesion, viability and osteogenic differentiation was favored on the sterilized coating of hydrogen peroxide plasma, behavior opposite to the observed coating sterilized by ethylene oxide

HA-hybrid matrix composite coating on Ti-Cp for biomedical application

Calcium phosphate coatings have been applied to titanium metal substrates and their alloys as a synergistic alternative capable of combining the mechanical properties of metals and the excellent bioactive properties provided by ceramic materials. However, the unsatisfactory adhesion of hydroxyapatite coatings on metallic substrates, as well as their limitation when subjected to mechanical stresses have been reported as a limitation. Biofunctional coatings have been proposed as an alternative to single ceramic coatings, aiming at optimizing the long-term clinical success of biomaterials such as Ti. This work aims at evaluating the morphological properties and biological behavior of Ti-cp coated with matrix composite coating hydroxyapatite-containing hybrid. The hybrid matrix was obtained from TEOS and MTES silicon precursors, with dispersed hydroxyapatite suspended by dip coating. For the morphological characterization FTIR, SEM/FEG, AFM and contact angle measurement were used. Biological behavior was evaluated for toxicity, cell viability and the osteogenic differentiation capacity of mesenchymal stem cells. The composite coatings obtained showed regular dispersion of hydroxyapatite particles in the hybrid matrix, with uniform coating adhering to the Ti-Cp substrate. Nevertheless, although they provided similar viability behavior of mesenchymal stem cells to the Ti-Cp substrate, the evaluated coatings did not present osteoinductive properties. This result is probably due to the pronounced hydrophobic behavior caused by the incorporation of HA

Biomaterials for bone regeneration : an orthopedic and dentistry overview

Because bone-associated diseases are increasing, a variety of tissue engineering approaches with bone regeneration purposes have been proposed over the last years. Bone tissue provides a number of important physiological and structural functions in the human body, being essential for hematopoietic maintenance and for providing support and protection of vital organs. Therefore, efforts to develop the ideal scaffold which is able to guide the bone regeneration processes is a relevant target for tissue engineering researchers. Several techniques have been used for scaffolding approaches, such as diverse types of biomaterials. On the other hand, metallic biomaterials are widely used as support devices in dentistry and orthopedics, constituting an important complement for the scaffolds. Hence, the aim of this review is to provide an overview of the degradable biomaterials and metal biomaterials proposed for bone regeneration in the orthopedic and dentistry fields in the last years

TEOS thin films obtained by plasma polymerization on Ti6Al4V alloys : influence of the deposition pressure on surface properties and cellular response

The modification of surfaces by the application of thin films has been used in the regenerative medicine area to increase the biocompatibility of metal implants. Titanium alloy has been recently used as substrate in poly merization for biomedical application. In this context, silane films were obtained by plasma polymerization in favor of the sol-gel method and the influence of different pressures in obtaining these films by argon plasma polymerization was evaluated from the alkoxysilane precursor tetraethoxysilane (TEOS) on the Ti6Al4V alloy. The morphological characterization of the films was performed by AFM, Profilometry and Spectral Ellipsometry and the chemical composition was analyzed by XPS. The biological behavior was evaluated by analyzing the mitochondrial activity and cellular viability of mesenchymal stem cells. The plasma polymerization process resulted in the deposition of a nanometric Si-based film formed, predominantly, by Si-O and organosilane bonds. The films that were applied on a sanded surface, with lower pressures in the plasma polymerization process, presented a lower layer thickness and wettability than the films obtained on nanotextured surfaces. Considering absorbance values, the Ti6Al4V samples mechanically sanded and deposited by plasma polymerization at 230 µatm presented better cell viability than samples with nanotextured surfaces coated with plasma polymerized film, indicating this material has potential to biomedical application

Wear resistance of plasma electrolytic oxidation coatings on Ti-6Al-4V ELI alloy processed by additive manufacturing

The additive manufacturing (AM) technique can produce Ti-6Al-4V ELI (extra low interstitial) alloy for personalized biomedical devices. However, the Ti-6Al-4V ELI alloy presents poor tribological behavior. Regarding this, coatings are a feasible approach to improve the wear resistance of this alloy. In the literature, the tribological behavior of TiO2 coatings incorporated with Ca and P formed by one-step plasma electrolytic oxidation (PEO) on Ti-6Al-4V ELI alloy processed by AM has not been investigated. Thus, in the present work, it was studied the influence of Ti-6Al-4V ELI alloy processed by AM on the wear resistance and morphologic of the coating obtained by PEO (plasma electrolytic oxidation). In this way, three different voltages (200, 250, and 300 V) were employed for the PEO process and the voltage effect on the properties of the coatings. The coatings were characterized by contact profilometry, scanning electron microscopy, energy-dispersive spectroscopy, the sessile drop method, grazing-incidence X-ray diffraction, and wear tests, on a ball-on-plate tribometer. The increase in applied voltage promoted an increase in roughness, pore area, and a decrease in the pore population of the coatings. In addition, the coatings, mainly composed of anatase and rutile, showed good adhesion to the metallic substrate, and the presence of bioactive elements Ca and P were detected. The thickness of the coatings obtained by PEO increases drastically for voltages higher than 250 V (from 4.50 ± 0.33 to 23.83 ± 1.5 µm). However, coatings obtained with lower voltages presented thin and dense layers, which promoted a superior wear resistance (increase in wear rate from 1.99 × 10−6 to 2.60 × 10−5 mm3/s). Finally, compared to the uncoated substrate, the PEO coatings increased the wear resistance of the titanium alloy obtained by AM, also showing a superior wear resistance compared to the commercial Ti-6Al-4V alloy previously evaluated, being such a positive and promising behavior for application in the area of metallic implants

Overview of sterilization methods for UHMWPE through surface analysis

The sterilization process is essential for the use of biomaterials in the human body in order to avoid contamination. However, the effect of such required pretreatment on the surface must be also evaluated since some modifications may cause a shortened lifespan of this material or changes in properties of interest. Moreover, improvements in sterilization techniques may even enhance properties while the surface is cleaned. The thorough understanding of the effect that the sterilization processes have on the surface of ultra-high molecular weight polyethylene (UHMWPE), widely used biomaterial in orthopedic joint prosthesis, is, therefore, a key study since some modifications during traditional sterilization could be a major problem for patients who have undergone arthroplasty surgery. This work brings a comprehensive study on sterilization techniques already available and extensively used (hydrogen peroxide plasma, ethylene oxide, steam autoclave) and a comparison with results obtained for recently developed cold plasma-based sterilization technique. The effects of the processes have been extensively compiled by data obtained for thermal analysis, nanoscale wear and friction, physicochemical, topographical, wettability, and in vitro cytotoxicity experiments. An overall outlook on the set of samples points out to cold plasma oxidation (CPO) being an adequate and potential candidate for improving wear resistance, while maintaining thermal stability and a restrained adhesion of L929 cells, provoked by its hydrophilicity and larger surface area

Pré-tratamento do aço carbono AISI 1010 com revestimentos nanocerâmicos para pintura eletrostática à base de resina de poliéster

Processos de pré-tratamento são amplamente utilizados em aços carbono com o intuito de aumentar a resistência à corrosão e também atuam como camadas de conversão conferindo a adesão de tintas ao substrato. Desenvolvimentos alternativos ao processo convencional de fosfatização vêm sendo estudados a fim de se obter revestimentos menos agressivos ao meio ambiente. Diante disso, os processos de pré-tratamentos baseados em nanotecnologia ganham êxito neste contexto, considerando que possuem como principal característica serem ambientalmente corretos, além disso, são promissores na redução de tempos e custos de processo. O presente trabalho tem por objetivo efetuar um estudo comparativo entre o desempenho de um processo convencional de fosfatização e três processos de pré-tratamentos nanocerâmicos comerciais de diferentes formulações sobre o substrato de aço AISI 1010, associados ou não a pintura a pó com a aplicação de tinta à base de resina poliéster. A caracterização das camadas de conversão foi avaliada quanto à topografia do filme formado (rugosidade), molhabilidade (determinação do ângulo de contato), microscopia eletrônica de varredura (MEV) e quanto ao comportamento eletroquímico (potencial de circuito aberto e polarização potenciodinâmica). A influência dos pré-tratamentos no processo de pintura eletrostática foi avaliada pela exposição do substrato pintado ao ensaio acelerado de corrosão em câmara de névoa salina e ensaios mecânicos de aderência, flexibilidade e impacto. A partir do estudo realizado foi possível observar que os três revestimentos nanocerâmicos avaliados apresentaram-se mais hidrofóbicos que o revestimento obtido por fosfatização (à base de fosfato de zinco). No entanto, o revestimento obtido por fosfatização apresentou potencial de corrosão menos ativo e desenvolveu menores valores de densidade de corrente, exibindo o melhor desempenho à corrosão seguido pelo revestimento nanocerâmico à base de cromo trivalente. Para as amostras cujos pré-tratamentos foram combinados com a pintura a pó à base de resina poliéster, o pré-tratamento com revestimentos nanocerâmicos promoveu o melhor desempenho quanto à resistência à corrosão, comparativamente às amostras pré-tratadas com fosfatização. Porém todos os sistemas estudados, independente do pré-tratamento empregado apresentaram comportamento mecânico e adesão similar e satisfatória.Pretreatment processes are widely used on carbon steels in order to increase the corrosion resistance and also act as conversion layers giving the adhesion of coatings to the substrate. Alternative developments to conventional phosphating process have been studied in order to obtain coatings which are less harmful to the environment. Thus, the pretreatment processes based on nanotechnology are successfully employed in this context, in which the nanoceramic coatings have as their main characteristic to be environmentally friendly, moreover, are promising for the reduction of the process time and costs. The present work aims to make a comparative study between the performance of a conventional phosphating process and three commercial nanoceramic pretreatment processes with different formulations on the substrate of AISI 1010 steel, associate or not to a polyester resin powder painting. The characterization of the conversion coatings was evaluated regarding the formed film topography (roughness), wettability (contact angle determination), scanning electron microscopy (SEM) and the electrochemical behavior (open circuit potential and polarization). The influence of pretreatments in the process of electrostatic paint was evaluated by exposure of the coated subtract to accelerated corrosion tests and mechanical adhesion test, flexibility and impact. From the study realized it was possible to observe that the three nanoceramic coatings evaluated presented higher hydrophobic behavior than the coating produced by the phosphating process (zinc phosphate based). However, the coating obtained by phosphating process showed a less active corrosion potential and developed lower values of current density, resulting in better corrosion performance followed by the nanoceramic coating based on trivalent chromium. For samples for which pretreatments were combined with the powder coating, nanoceramic coatings showed a better performance against corrosion when compared to the samples pretreated with phosphating process. All systems studied independent of the pretreatment used, showed similar and satisfactory adhesion and mechanical behavior

Efeito do processo de esterilização sobre as propriedades de revestimentos híbridos e sobre a diferenciação osteogênica de células-tronco mesenquimais

Revestimentos híbridos silanos têm sido aplicados sobre a liga de Ti6Al4V como forma de melhorar sua resistência à corrosão e sua propriedade de bioatividade. No contexto de funcionalização de superfícies, a introdução de células-tronco em estruturas objetivando o crescimento de novos tecidos tem sido muito estudada, como por exemplo, no processo de osteointegração. No entanto, ao final do desenvolvimento de biomateriais, a escolha do processo de esterilização deve ser cuidadosamente considerada, uma vez que essa pode comprometer as propriedades requeridas para os mesmos. O presente trabalho teve por objetivo avaliar a influência de 3 diferentes processos de esterilização: autoclave a vapor, plasma de peróxido de hidrogênio e óxido de etileno, sobre as propriedades de um revestimento híbrido silano e sobre a diferenciação osteogênica de células-tronco mesenquimais. Para isso, os revestimentos foram obtidos a partir de um sol constituído pelos precursores silanos Tetraetoxisilano (TEOS) e Metiltrietoxisilano (MTES), aplicados sobre o substrato de Ti6Al4V. Para promover a bioatividade, partículas de hidroxiapatita foram dispersas em um segundo revestimento (TEOS/MTES + hidroxiapatita) aplicado sobre o primeiro (TEOS/MTES). Após a esterilização, os revestimentos foram avaliados por microscopia eletrônica de varredura, microscopia de força atômica, perfilometria, molhabilidade e espectroscopia no infravermelho por transformada de Fourier. O comportamento eletroquímico foi avaliado por monitoramento do potencial de circuito aberto e curvas de polarização potenciodinâmicas. A citocompatibilidade para células MG-63 foi avaliada para o revestimento protetivo e a diferenciação osteogênica para o revestimento bioativo aplicado sobre a camada protetiva. Os resultados mostraram que após a esterilização o efeito barreira do revestimento protetivo foi comprometido e isso pode ser associado às modificações superficiais ocasionadas pelos mesmos. Todos os processos de esterilização provocaram modificações morfológicas no revestimento bioativo, aumentando a bioatividade do mesmo. As esterilizações por óxido de etileno e plasma de peróxido de hidrogênio intensificaram a degradação hidrolítica do revestimento bioativo e a partir disso os mesmos apresentaram maiores índices de liberação de silício. Os revestimentos bioativos esterilizados não apresentaram citotoxicidade às células-tronco mesenquimais. O comportamento de adesão, viabilidade e diferenciação osteogênica foi favorecido sobre o revestimento esterilizado por plasma de peróxido de hidrogênio, comportamento oposto ao observado para o revestimento esterilizado por óxido de etileno.Silane hybrid coatings have been applied on the Ti6Al4V alloy as a way to improve their corrosion resistance and their bioactivity properties. In the context of surface functionalization, the introduction of stem cells into structures, aiming at the growth of new tissues, has been much studied as, for example, in the process of osteointegration. However, at the end of the development of biomaterials, the choice of the sterilization process should be carefully considered, once this may compromise the properties required for it. The aim of the present work was to evaluate the influence of three different sterilization processes: steam autoclave, hydrogen peroxide plasma and ethylene oxide, on the protective and bioactive properties of a hybrid silane coating. For this, the coatings were obtained from a sol consisting of the precursor silanes Tetraethoxysilane (TEOS) and precursor Methyltriethoxysilane (MTES), applied on Ti6Al4V. To promote bioactivity, hydroxyapatite particles were dispersed in a second coating (TEOS/MTES + hydroxyapatite) applied on the first (TEOS/MTES). After sterilization, coatings were evaluated by scanning electron microscopy, atomic force microscopy, profilometry, wettability and fourier transform infrared spectroscopy The electrochemical behavior was evaluated by monitoring the open circuit potential and the potentialdynamic polarization curves. The cytocompatibility of MG-63 cells was evaluated for the protective coating and osteogenic differentiation for the bioactive coating applied on the protective layer. The results showed that after sterilization the barrier effect of the protective coating was compromised, and this may be associated with the surface modifications caused by the coating. All sterilization methods caused morphological modifications in the bioactive coating, increasing its bioactivity. Sterilization by ethylene oxide and hydrogen peroxide plasma intensified the hydrolytic degradation of the bioactive coating and from this they showed higher rates of silicon release. Sterilized bioactive coatings did not show cytotoxicity to mesenchymal stem cells. The behavior of adhesion, viability and osteogenic differentiation was favored on the sterilized coating of hydrogen peroxide plasma, behavior opposite to the observed coating sterilized by ethylene oxide

Pré-tratamento do aço carbono AISI 1010 com revestimentos nanocerâmicos para pintura eletrostática à base de resina de poliéster

Processos de pré-tratamento são amplamente utilizados em aços carbono com o intuito de aumentar a resistência à corrosão e também atuam como camadas de conversão conferindo a adesão de tintas ao substrato. Desenvolvimentos alternativos ao processo convencional de fosfatização vêm sendo estudados a fim de se obter revestimentos menos agressivos ao meio ambiente. Diante disso, os processos de pré-tratamentos baseados em nanotecnologia ganham êxito neste contexto, considerando que possuem como principal característica serem ambientalmente corretos, além disso, são promissores na redução de tempos e custos de processo. O presente trabalho tem por objetivo efetuar um estudo comparativo entre o desempenho de um processo convencional de fosfatização e três processos de pré-tratamentos nanocerâmicos comerciais de diferentes formulações sobre o substrato de aço AISI 1010, associados ou não a pintura a pó com a aplicação de tinta à base de resina poliéster. A caracterização das camadas de conversão foi avaliada quanto à topografia do filme formado (rugosidade), molhabilidade (determinação do ângulo de contato), microscopia eletrônica de varredura (MEV) e quanto ao comportamento eletroquímico (potencial de circuito aberto e polarização potenciodinâmica). A influência dos pré-tratamentos no processo de pintura eletrostática foi avaliada pela exposição do substrato pintado ao ensaio acelerado de corrosão em câmara de névoa salina e ensaios mecânicos de aderência, flexibilidade e impacto. A partir do estudo realizado foi possível observar que os três revestimentos nanocerâmicos avaliados apresentaram-se mais hidrofóbicos que o revestimento obtido por fosfatização (à base de fosfato de zinco). No entanto, o revestimento obtido por fosfatização apresentou potencial de corrosão menos ativo e desenvolveu menores valores de densidade de corrente, exibindo o melhor desempenho à corrosão seguido pelo revestimento nanocerâmico à base de cromo trivalente. Para as amostras cujos pré-tratamentos foram combinados com a pintura a pó à base de resina poliéster, o pré-tratamento com revestimentos nanocerâmicos promoveu o melhor desempenho quanto à resistência à corrosão, comparativamente às amostras pré-tratadas com fosfatização. Porém todos os sistemas estudados, independente do pré-tratamento empregado apresentaram comportamento mecânico e adesão similar e satisfatória.Pretreatment processes are widely used on carbon steels in order to increase the corrosion resistance and also act as conversion layers giving the adhesion of coatings to the substrate. Alternative developments to conventional phosphating process have been studied in order to obtain coatings which are less harmful to the environment. Thus, the pretreatment processes based on nanotechnology are successfully employed in this context, in which the nanoceramic coatings have as their main characteristic to be environmentally friendly, moreover, are promising for the reduction of the process time and costs. The present work aims to make a comparative study between the performance of a conventional phosphating process and three commercial nanoceramic pretreatment processes with different formulations on the substrate of AISI 1010 steel, associate or not to a polyester resin powder painting. The characterization of the conversion coatings was evaluated regarding the formed film topography (roughness), wettability (contact angle determination), scanning electron microscopy (SEM) and the electrochemical behavior (open circuit potential and polarization). The influence of pretreatments in the process of electrostatic paint was evaluated by exposure of the coated subtract to accelerated corrosion tests and mechanical adhesion test, flexibility and impact. From the study realized it was possible to observe that the three nanoceramic coatings evaluated presented higher hydrophobic behavior than the coating produced by the phosphating process (zinc phosphate based). However, the coating obtained by phosphating process showed a less active corrosion potential and developed lower values of current density, resulting in better corrosion performance followed by the nanoceramic coating based on trivalent chromium. For samples for which pretreatments were combined with the powder coating, nanoceramic coatings showed a better performance against corrosion when compared to the samples pretreated with phosphating process. All systems studied independent of the pretreatment used, showed similar and satisfactory adhesion and mechanical behavior