Electrochemical study of the influence of H

The stability of the oxide layer at the surface of stainless steel is very important to protect medical implants, knowing that chemical product like hydrogen peroxide can change its behaviour. When used medical implants go through various steps in which hydrogen peroxide is involved. Corrosion of 316L stainless steel implant in Hank’s solution at body temperatures was evaluated for different concentrations of hydrogen peroxide. Open circuit potential (OCP) and potentiodynamic tests were carried out. According to the results, when the concentration of H2O2 is increased, the potential becomes more positive but the passive layer formed at the surface of the implant remains unstable. Independently of hydrogen peroxide concentration, the corrosion potential shifts to more negative values proportionally to the increase of immersion times from 0 to 72 h. When immersions are superior to 72 h, in the presence of high hydrogen peroxide concentrations, the breakdown potential increase positively with the increase of the immersion time (ennoblement occurs). Rising Hank’s solution temperature containing H2O2 from 37 °C to 42 °C increased pitting corrosion of 316L SS implant. Micrographs taken after polarization, showed a particular layout of pits which may explain the stainless steel implants rupture and lead to the improvement of their elaboration

Electrochemical study of the influence of H 2

The stability of the oxide layer at the surface of stainless steel is very important to protect medical implants, knowing that chemical product like hydrogen peroxide can change its behaviour. When used medical implants go through various steps in which hydrogen peroxide is involved. Corrosion of 316L stainless steel implant in Hank’s solution at body temperatures was evaluated for different concentrations of hydrogen peroxide. Open circuit potential (OCP) and potentiodynamic tests were carried out. According to the results, when the concentration of H2O2 is increased, the potential becomes more positive but the passive layer formed at the surface of the implant remains unstable. Independently of hydrogen peroxide concentration, the corrosion potential shifts to more negative values proportionally to the increase of immersion times from 0 to 72 h. When immersions are superior to 72 h, in the presence of high hydrogen peroxide concentrations, the breakdown potential increase positively with the increase of the immersion time (ennoblement occurs). Rising Hank’s solution temperature containing H2O2 from 37 °C to 42 °C increased pitting corrosion of 316L SS implant. Micrographs taken after polarization, showed a particular layout of pits which may explain the stainless steel implants rupture and lead to the improvement of their elaboration

Механічна характеристика електроосадженого покриття із сплаву Ni-P

Процес електроосадження відіграє вирішальну роль у формуванні тонких плівок на інших матеріалах, зокрема, електроосадження сплаву нікель-фосфору, через його важливі властивості. У дослідженні покриття Ni-P були нанесені на сталеві (Х52) підкладки методом електроосадження з розчину, що містить сульфат нікелю, гіпофосфіт натрію (NaH2PO2). Склад, морфологія поверхні та механічні властивості покриттів Ni-P вивчалися за допомогою методів SEM, EDAX, методу Віккерса, методів вагових втрат та потенціодинамічної поляризації. Досліджували вплив густини струму на морфологію поверхні, вміст фосфору, мікротвердість та корозію покриттів. Було помічено, що як вміст фосфору, так і мікротвердість залежать від густини струму. Результати морфології електроосаджених сплавів Ni-P показують, що зерна мають сферичну форму для усіх зразків. Було виявлено, що вплив густини струму на вміст фосфору в покриттях зв’язаний зворотним співвідношенням. Крім того, сформовані покриття при густині струму 5 А∙м − 4 виявляють гарну мікротвердість. Корозійні випробування показують, що величина 5 А∙м − 4 є найкращим значенням густини струму, яке дає найкраще захисне покриття від корозії.The electrodeposition process plays a crucial role in the formation of thin films on materials, in particular, the electrodeposition of nickel-phosphorus because of its important properties. In this study, Ni-P coatings were deposited on X52 steel substrates by electrodeposition technique from a solution containing nickel sulfate, sodium hypophosphite (NaH2PO2). Composition, surface morphology, and mechanical properties of the Ni-P deposits were studied using SEM, EDAX, the Vickers method, weight loss and potentiodynamic polarization techniques. The effects of the current density were investigated on the surface morphology, phosphorus content, microhardness and corrosion of the coatings. It was observed that both the phosphorus content and microhardness are dependent on the current density. Results demonstrate that the morphology of the electrodeposited Ni-P alloys shows that the grains are spherical in nature for all the samples. It has been observed that the influence of current density on the P content of the deposit is an inverse relation with phosphorous content and also the as-plated coatings at current density of 5 A∙m − 4 exhibit the superior microhardness. Corrosion tests show that 5 A∙m − 4 is the best current density value which gives the best protection coating against corrosion

Електроосадження та механічні характеристики композитних покриттів Ni/SiC

Необхідність вдосконалення покриттів для поліпшення їх властивостей призводить до розробки композитного електролітичного осадження шляхом додавання до електроліту нерозчинних твердих частинок. Ці покриття зазвичай містять керамічні частинки в електроосадженій матриці, такі як нікель. Метою даної роботи є отримання електролітичної нікелевої матриці (з’єднувальної) із та без додавання мікрочастинок карбіду кремнію SiC (середній діаметр 0.8 мкм), які мають високу твердість і гарну хімічну стабільність. Структурні (Ni-SiC) композитні і чисті нікелеві покриття готували шляхом нанесення гальванопластики на сталь у ванні Ваттса з гальванічним хлоридом. Вивчено морфологію поверхні, мікроструктуру та склад отриманих покриттів методом атомно-силової мікроскопії (AFM), наноіндентації, скануючої електронної мікроскопії (SEM) та рентгенівського дифрактометра. Характеристики нанесених шарів проводять у 3.5 % розчині NaCl. Втрата ваги та результати поляризації підкреслили, що швидкість корозії зменшується зі збільшенням концентрації SiC до 15 gl – 1. Це зменшення, ймовірно, пояснюється присутністю частинок SiC, що призводять до поліпшення корозійної стійкості. Ці властивості в основному обумовлені однорідним розподілом складових SiC, визначеним методом АСМ, та можливостями поєднання характеристик основних металів та їх покриттів. Більш того, включення мікрочастинок мало значний вплив на мікротвердість композитних нанесень Ni-SiC.The need to improve coatings for better properties leads to the development of composite electrolytic deposition, by adding insoluble solid particles to the electrolyte. These coatings typically contain ceramic particles in an electrodeposited matrix such as nickel. The aim of this work is to obtain an electrolytic nickel matrix (binder) with and without adding silicon carbide SiC microparticles (mean diameter 0.8 µm) which have a high hardness and a good chemical stability. The structural (Ni-SiC) composite and pure nickel coatings were prepared by electroplating deposition on steel in a Watts bath of electroplating chloride. The surface morphology, microstructure, and composition were studied by atomic force microscopy (AFM), nanoindentation, scanning electron microscopy (SEM) and X-ray diffractometer. The characterizations of the deposited layers are carried out in 3.5 % NaCl solution. The weight loss and the polarization results highlighted that the corrosion rate decreases with the increase of SiC concentration up to 15 gl – 1. This decrease is probably due to the presence of SiC particles leading to improved corrosion resistance. These properties are mainly due to the homogeneous distribution of the constituents SiC as determined by AFM technique and the possibilities of combining the characteristics of base metals and their coatings. Moreover, the incorporation of the microparticles had a significant impact on the microhardness of the composite deposits Ni-SiC

Структурна, механічна та корозійна поведінка композитних покриттів Ni-P-TiO2: вплив густини струму

Композитні покриття Ni-P-TiO2 важливі для техніки завдяки таким властивостям, як стійкість до зносу та корозії, електро- та теплопровідність, магнітним властивостям. У роботі вперше досліджено вплив густини струму на електроосаджені композитні покриття Ni-P-TiO2. Композитні покриття Ni-PTiO2 осаджувалися на мідні підкладки з густинами прикладеного струму, рівними 1, 3, 5, 7 та 9 А·дм – 2. Для дослідження морфологічних, мікроструктурних та механічних властивостей використовували рентгеноструктурний аналіз (XRD), скануючу електронну мікроскопію (SEM), енергодисперсійну спектроскопію (EDS) та аналіз мікротвердості. З іншого боку, корозійні властивості покриттів оцінювали за допомогою поляризаційної та електрохімічної імпедансної спектроскопії (EIS). Результати XRD показують, що включення наночастинок TiO2 в покриття змінює відносну інтенсивність піку Ni, а також його ширину. Крім того, мікротвердість покриттів помітно збільшується з густиною струму. Найкращу мікротвердість і корозійну стійкість демонструє композитне покриття Ni-P-TiO2, нанесене електроосадженням при 3 А·дм – 2.Ni-P-TiO2 composite coatings are important in engineering due to their properties such as good resistance to wear and corrosion, magnetic properties, electrical and thermal conductivity. In this paper, the effect of current density on electrodeposited Ni-P-TiO2 composite coatings was investigated for the first time. Ni-P-TiO2 composite coatings were deposited with applied current densities (1, 3, 5, 7 and 9 A·dm – 2) on copper substrates. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and microhardness analysis were used to study the morphological, microstructural and mechanical properties. On the other hand, the corrosion performance of the coatings was evaluated using Tafel polarization and electrochemical impedance spectroscopy (EIS). XRD results indicate that the inclusion of TiO2 nanoparticles into the coatings alters the relative intensity of Ni peak as well as peak breadth. In addition, microhardness of the coatings noticeably increased with current densities. Ni-P-TiO2 composite coating electrodeposited at 3 A·dm – 2 exhibits the best microhardness and corrosion resistance

Increased phagolysosomal fusion during CREB inhibition requires RIPK3 activity.

A) MDMs were plated on glass coverslips and pretreated with for 60 min with DMSO or CREB inhibitor 666–15 +/- Nec-1, GSK’872, or NSA, then infected with mCherry M.tb H37Rv (red) MOI 10. MDMs were fixed, permeabilized, and stained for LAMP-1 (green) and DAPI (blue). A representative experiment is shown of n = 4–5 donors. B) At the indicated time points, the percent of M.tb colocalizing with LAMP-1 was calculated following manual counting. White arrows indicate colocalization. Data are cumulative ± SEM of n = 4–5 donors. One-way ANOVA with Tukey’s post-test; *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.</p

<i>M</i>.<i>tb</i>-induced CREB activation is important for induction of immediate early genes in human macrophages.

MDMs were pretreated with DMSO or 666–15 for 60 min and subsequently infected with M.tb H37Rv at the MOI 10 (A-F,H) by synchronized phagocytosis or MOI 5(E). RNA or protein lysates were collected at the indicated time points. A-D) Gene expression of COX2, MCL-1, CCL8 and c-FOS was determined by qRT-PCR and data are shown as fold change ± SEM compared to uninfected MDMs. Data are cumulative of n = 3–5 donors. One-way ANOVA with Tukey’s post-test. E) Cell lysates were probed by WB for COX2, MCL-1 and β-actin. A representative experiment is shown of n = 3–4 donors. F,H) Densitometry at 3h post infection compared to M.tb-infected MDMs. Data are cumulative ± SEM of n = 3–4 donors. Unpaired t test. G) PGE2 production was measured by competitive binding ELISA at 6h post infection. Data are cumulative ± SEM of n = 4 donors. Unpaired t test; *p < 0.05. **p < 0.01, ****p < 0.0001.</p

Reagents and Antibodies.

Macrophages are a first line of defense against pathogens. However, certain invading microbes modify macrophage responses to promote their own survival and growth. Mycobacterium tuberculosis (M.tb) is a human-adapted intracellular pathogen that exploits macrophages as an intracellular niche. It was previously reported that M.tb rapidly activates cAMP Response Element Binding Protein (CREB), a transcription factor that regulates diverse cellular responses in macrophages. However, the mechanism(s) underlying CREB activation and its downstream roles in human macrophage responses to M.tb are largely unknown. Herein we determined that M.tb-induced CREB activation is dependent on signaling through MAPK p38 in human monocyte-derived macrophages (MDMs). Using a CREB-specific inhibitor, we determined that M.tb-induced CREB activation leads to expression of immediate early genes including COX2, MCL-1, CCL8 and c-FOS, as well as inhibition of NF-kB p65 nuclear localization. These early CREB-mediated signaling events predicted that CREB inhibition would lead to enhanced macrophage control of M.tb growth, which we observed over days in culture. CREB inhibition also led to phosphorylation of RIPK3 and MLKL, hallmarks of necroptosis. However, this was unaccompanied by cell death at the time points tested. Instead, bacterial control corresponded with increased colocalization of M.tb with the late endosome/lysosome marker LAMP-1. Increased phagolysosomal fusion detected during CREB inhibition was dependent on RIPK3-induced pMLKL, indicating that M.tb-induced CREB signaling limits phagolysosomal fusion through inhibition of the necroptotic signaling pathway. Altogether, our data show that M.tb induces CREB activation in human macrophages early post-infection to create an environment conducive to bacterial growth. Targeting certain aspects of the CREB-induced signaling pathway may represent an innovative approach for development of host-directed therapeutics to combat TB.</div

Effect of <i>M</i>.<i>tb</i> infection and CREB inhibition on expression of select genes and c-FOS protein.

MDMs were pretreated with DMSO or 666–15 for 60 min and subsequently infected with M.tb H37Rv at the MOI 10 by synchronized phagocytosis. A) RNA was collected at the indicated time points and gene expression of the indicated genes was determined by qRT-PCR. Data are shown as fold change ± SEM compared to uninfected MDMs. Data are cumulative of n = 3–5 donors. One-way ANOVA with Tukey’s post-test. B) Cell lysates were probed by WB for c-FOS and β-actin. Shown is a representative experiment of n = 3. C) Densitometry at 3h post infection compared to M.tb-infected MDMs. Data are cumulative ± SEM of n = 3 donors. Unpaired t test; *p (TIF)</p

MLKL is essential for phagolysosomal fusion in the absence of CREB signaling in <i>M</i>.<i>tb</i>-infected human macrophages.

MDMs were plated on glass coverslips and transfected with siRNA targeting MLKL or scrambled control siRNA for 48h. MDMs were then pretreated for 60 min with CREB inhibitor 666–15 and infected with mCherry M.tb H37Rv (red) MOI 10. A) Knockdown of MLKL was verified by WB and percent signal quantified relative to scrambled control. A representative experiment is shown and graphed data are cumulative of n = 3 donors. Unpaired t test. B) MDMs were fixed, permeabilized, and stained for LAMP-1 (green) and DAPI (blue). A representative experiment is shown of n = 3 donors. C) At the indicated time points, the percent of M.tb colocalizing with LAMP-1 was calculated following manual counting. Data are shown as fold change of percent colocalization compared to scrambled control for each time point. White arrows indicate colocalization. Data are cumulative ± SEM of n = 3 donors. Unpaired t test *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.</p