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Akram Alfantazi - One of the best experts on this subject based on the ideXlab platform.
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Corrosion behaviour of niobium in Phosphate Buffered Saline solutions with different concentrations of bovine serum albumin
Corrosion Science, 2012Co-Authors: Wei Wang, Farzad Mohammadi, Akram AlfantaziAbstract:Abstract The corrosion behaviour of Nb was studied in Phosphate Buffered Saline (PBS) solutions at a presence of 0–6 g L −1 bovine serum albumin (BSA). Addition of BSA to PBS solutions lowered the open circuit potential (OCP). OCP, polarization resistance and impedance increased over immersion time. The adsorption process of BSA on Nb surface was found to be faster than that of the PO 4 3− . According to X-ray Photoelectron Spectroscopy (XPS) a competitive adsorption between PO 4 3− and BSA was in effect during the immersion process. Based on the analysis of effective capacitances, a surface distribution of time-constants was proposed.
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effects of bovine serum albumin on the corrosion behaviour of aisi 316l co 28cr 6mo and ti 6al 4v alloys in Phosphate Buffered Saline solutions
Corrosion Science, 2011Co-Authors: Shima Karimi, Tirdad Nickchi, Akram AlfantaziAbstract:Abstract The corrosion behaviour of AISI 316L, wrought Co–28Cr–6Mo and Ti–6Al–4V was studied in aerated solutions of Phosphate Buffered Saline (PBS) at various concentrations of bovine serum albumin (BSA) at 37 °C. Open circuit potential, potentiodynamic polarization, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) experiments along with X-ray photoelectron spectroscopy (XPS) on Co–28Cr–6Mo oxide layer were conducted to study the interaction of BSA and passive layers and to measure the corrosion rates. Ti–6Al–4V alloy had the lowest corrosion rate and the highest breakdown potential. It was shown that BSA has enhanced the alloy passive film stability at higher concentrations.
Jeremy L Gilbert - One of the best experts on this subject based on the ideXlab platform.
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in vitro fretting crevice corrosion damage of cocrmo alloys in Phosphate Buffered Saline debris generation chemistry and distribution
Acta Biomaterialia, 2020Co-Authors: Dongkai Zhu, Jeremy L Gilbert, Yangping LiuAbstract:Abstract Fretting crevice corrosion in modular tapers of total hip replacements has become a major concern in orthopedic medical devices. Solid and ionic debris arising from fretting crevice corrosion have been implicated in device failure and revision surgery. This study aims to use a 2D pin-on-disk fretting corrosion test system to visualize damage progression and debris generation during fretting corrosion of CoCrMo alloys in Phosphate Buffered Saline (PBS). The results provide direct evidence of rapid debris generation during fretting corrosion (after only 12 min of testing). Debris was generated and either extruded from the contact region or impacted into adjacent crevice sites as long as fretting continued. After testing, the fretting region consisted of a damaged and plastically deformed contact region surrounded by a halo of fretting debris consisting entirely of oxides and Phosphates within the crevice region. Evidence of pitting corrosion and grain boundary corrosion was observed. Solid debris consisted of chromium (Cr), Phosphate (P) and oxygen (O). X-ray photoelectron spectroscopy analysis of the near-fretted metal surface area showed a thicker oxygen (O1s) containing film with the depth profile of O1s above 10% penetrating up to 5.75 nm while the O1s concentration on the unfretted area fell to below 10% after 1 nm depth. Ion concentration in the PBS, measured using inductively coupled mass spectrometry, showed cobalt (Co) ions were most prevalent (1.46 ppm) compared to chromium (Cr) (0.07 ppm) and molybdenum (Mo) (0.05 ppm) (p Statement of Significance CoCrMo alloys has been widely used as a metallic biomaterial for implant devices and can lose their durability and reliability due to wear, corrosion and tribocorrosion. Debris, as one of the major products of these reactions, is associated with implant device failure. In the first time, we developed a fretting corrosion testing system to visualize the debris generation process in real-time between CoCrMo alloy pin and disk samples. Debris was generated rapidly during fretting corrosion and some of the debris egressed from the crevice site while also accumulating within the crevice area as fretting continued. Our study opens a new method for future studies to advance understanding of debris generation processes during wear and tribocorrosion phenomenon.
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fretting initiated crevice corrosion of 316lvm stainless steel in physiological Phosphate Buffered Saline potential and cycles to initiation
Acta Biomaterialia, 2019Co-Authors: Yangping Liu, Dongkai Zhu, David Pierre, Jeremy L GilbertAbstract:Abstract Mechanically assisted crevice corrosion (MACC) has been associated with implant failure in vivo and is a serious concern in numerous metallic implant systems. Stainless steel medical devices may be subjected to fretting and crevice corrosion in the human body as are titanium and CoCrMo alloys due to the presence of a passive oxide film on their surface. One mechanism of MACC that has not been clearly identified and studied is fretting-initiated crevice corrosion (FICC) of stainless steel where an initial fretting event can initiate a rapid propagating crevice corrosion process even when fretting has ceased. FICC pin-on-disk experiments were performed at varying potential conditions and duration of fretting to explore the role of potential and fretting duration on the initiation of crevice corrosion. Triggering of a propagating crevice corrosion reaction on stainless steel at 250 mV vs Ag/AgCl/KCl (saturated) in PBS solution required only 2 s (2 cycles at 1 Hz) of fretting. Crevice corrosion continued to propagate under a 1.8 mm diameter pin with only 100 μm of direct contact, dissolving in both the depth and width dimension away from the fretting contact while the currents rose from 0.2 μA to 15 μA within 5 min. Three different potential-dependent FICC regions were identified that included unstable crevice corrosion (50 mV and above), metastable crevice corrosion (−100 mV to 0 mV) and stable fretting corrosion (between −500 mV and −150 mV). Crevice corrosion can be induced by fretting at potentials as low as −100 mV. Below −100 mV, there was no FICC, but rather fretting corrosion stopped immediately after fretting ceased and returned to a stable baseline current. Metastable FICC was shown at potentials between −100 mV and 0 mV, when the crevice corrosion current gradually decreased over several seconds or longer after fretting ceased. Self-sustained, unstable crevice corrosion started at 50 mV, where prior to fretting the currents were low, and after just a few cycles of fretting the crevice current rose rapidly and continued to increase after fretting stopped. Increase of potential increased the susceptibility of stainless steel to FICC. Scanning electron microscopy and digital optical microscopy revealed pitting and crevice corrosion on samples at −100 mV and higher potentials, where FICC was developing. By removing the oxide film, fretting motion significantly facilitates the critical crevice solution development, lowering the critical crevice potential and decreasing the initiation time for crevice corrosion. These results indicate that fretting initiated crevice corrosion may affect the performance of stainless steel in vivo. Statement of Significance AISI 316L stainless steel has been widely used as a metallic biomaterial for orthopaedic, spinal, dental and cardiovascular implants. Crevice corrosion has been a serious concern for stainless steel implants. For the first time we demonstrated and systematically studied the process of fretting-initiated crevice corrosion (FICC) in 316L stainless steel in simulated physiological solution of Phosphate Buffered Saline. By removing the oxide film, fretting motion significantly facilitates the critical crevice solution development, lowering the critical crevice potential and decreasing the initiation time for crevice corrosion. Our findings indicate fundamental differences between the FICC mechanism and conventional crevice corrosion theory, showing that fretting can play a significant role in the initiation of crevice corrosion of stainless steel.
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a time based potential step analysis of electrochemical impedance incorporating a constant phase element a study of commercially pure titanium in Phosphate Buffered Saline
Journal of Biomedical Materials Research Part A, 2009Co-Authors: Mark T Ehrensberger, Jeremy L GilbertAbstract:The measurement of electrochemical impedance is a valuable tool to assess the electrochemical environment that exists at the surface of metallic biomaterials. This article describes the development and validation of a new technique, potential step impedance analysis (PSIA), to assess the electrochemical impedance of materials whose interface with solution can be modeled as a simplified Randles circuit that is modified with a constant phase element. PSIA is based upon applying a step change in voltage to a working electrode and analyzing the subsequent current transient response in a combined time and frequency domain technique. The solution resistance, polarization resistance, and interfacial capacitance are found directly in the time domain. The experimental current transient is numerically transformed to the frequency domain to determine the constant phase exponent, alpha. This combined time and frequency approach was tested using current transients generated from computer simulations, from resistor-capacitor breadboard circuits, and from commercially pure titanium samples immersed in Phosphate Buffered Saline and polarized at -800 mV or +1000 mV versus Ag/AgCl. It was shown that PSIA calculates equivalent admittance and impedance behavior over this range of potentials when compared to standard electrochemical impedance spectroscopy. This current transient approach characterizes the frequency response of the system without the need for expensive frequency response analyzers or software.
Kyong Y Rhee - One of the best experts on this subject based on the ideXlab platform.
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experimental data and modeling of electrical conductivity for polymer carbon nanotubes nanobiosensor during degradation in neutral Phosphate Buffered Saline pbs
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2020Co-Authors: Yasser Zare, Kyong Y RheeAbstract:Abstract This paper studies the conductivity of poly (lactic acid) (PLA)/poly (ethylene oxide) (PEO)/carbon nanotubes (CNT) nanocomposites during degradation in neutral Phosphate-Buffered Saline (PBS) solution by experimental and modeling results. PLA/PEO/CNT nanocomposites are prepared and the conductivity of samples is measured before and during degradation. This system can be applied as a degradation nanobiosensor, because the variation of conductivity expresses the extent of degradation. A simple model is developed to predict the variation of conductivity during hydrolytic degradation. The degradation of polymers improves the effectiveness of CNT networks in the samples growing the conductivity. The proper agreement between experimental and theoretical results approves the validity of the developed model. A longer degradation time destroys more polymer chains shortening the tunneling space between CNT. The percolation threshold increases during degradation, due to the degradation of interphase zones between polymer and CNT. The calculations demonstrate that the fraction of networked CNT decreases during degradation, because PBS solution attacks the CNT networks. These reasonable predictions validate the developed equations representing the variations of conductivity, tunneling distance, percolation threshold and the fraction of networked CNT in the samples during degradation.
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simple model for hydrolytic degradation of poly lactic acid poly ethylene oxide carbon nanotubes nanobiosensor in neutral Phosphate Buffered Saline solution
Journal of Biomedical Materials Research Part A, 2019Co-Authors: Yasser Zare, Kyong Y Rhee, Soojin ParkAbstract:In this study, the hydrolytic degradation of poly(lactic acid) (PLA)/poly(ethylene oxide) (PEO) blend and PLA/PEO/carbon nanotubes (CNTs) nanobiosensors in neutral Phosphate-Buffered Saline (PBS) solution was investigated by experimental and theoretical approaches. A simple model was developed to estimate the degradation fraction by applying the average degradation rate (K) and time exponent. The predictions of the developed model were compared to the experimental results. Moreover, CNT concentration, CNT size, sample thickness, diffusion coefficient, and concentration of the PEO phase influenced the K value. The impacts of the parameters on the degradation rate were studied to confirm the developed equation. All samples were rapidly degraded during the first week, while the degradation slowly progressed in the following weeks. The experimental and theoretical results demonstrate that CNTs quicken the degradation of samples. The degradation fraction of a nanobiosensor depends directly on the values of K and the time exponent. Furthermore, a high concentration of PEO, small thickness of the sample, high concentration of thin CNTs, and high diffusion coefficient desirably improve the degradation rate.
Yasser Zare - One of the best experts on this subject based on the ideXlab platform.
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experimental data and modeling of electrical conductivity for polymer carbon nanotubes nanobiosensor during degradation in neutral Phosphate Buffered Saline pbs
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2020Co-Authors: Yasser Zare, Kyong Y RheeAbstract:Abstract This paper studies the conductivity of poly (lactic acid) (PLA)/poly (ethylene oxide) (PEO)/carbon nanotubes (CNT) nanocomposites during degradation in neutral Phosphate-Buffered Saline (PBS) solution by experimental and modeling results. PLA/PEO/CNT nanocomposites are prepared and the conductivity of samples is measured before and during degradation. This system can be applied as a degradation nanobiosensor, because the variation of conductivity expresses the extent of degradation. A simple model is developed to predict the variation of conductivity during hydrolytic degradation. The degradation of polymers improves the effectiveness of CNT networks in the samples growing the conductivity. The proper agreement between experimental and theoretical results approves the validity of the developed model. A longer degradation time destroys more polymer chains shortening the tunneling space between CNT. The percolation threshold increases during degradation, due to the degradation of interphase zones between polymer and CNT. The calculations demonstrate that the fraction of networked CNT decreases during degradation, because PBS solution attacks the CNT networks. These reasonable predictions validate the developed equations representing the variations of conductivity, tunneling distance, percolation threshold and the fraction of networked CNT in the samples during degradation.
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simple model for hydrolytic degradation of poly lactic acid poly ethylene oxide carbon nanotubes nanobiosensor in neutral Phosphate Buffered Saline solution
Journal of Biomedical Materials Research Part A, 2019Co-Authors: Yasser Zare, Kyong Y Rhee, Soojin ParkAbstract:In this study, the hydrolytic degradation of poly(lactic acid) (PLA)/poly(ethylene oxide) (PEO) blend and PLA/PEO/carbon nanotubes (CNTs) nanobiosensors in neutral Phosphate-Buffered Saline (PBS) solution was investigated by experimental and theoretical approaches. A simple model was developed to estimate the degradation fraction by applying the average degradation rate (K) and time exponent. The predictions of the developed model were compared to the experimental results. Moreover, CNT concentration, CNT size, sample thickness, diffusion coefficient, and concentration of the PEO phase influenced the K value. The impacts of the parameters on the degradation rate were studied to confirm the developed equation. All samples were rapidly degraded during the first week, while the degradation slowly progressed in the following weeks. The experimental and theoretical results demonstrate that CNTs quicken the degradation of samples. The degradation fraction of a nanobiosensor depends directly on the values of K and the time exponent. Furthermore, a high concentration of PEO, small thickness of the sample, high concentration of thin CNTs, and high diffusion coefficient desirably improve the degradation rate.
Youichi Fujii - One of the best experts on this subject based on the ideXlab platform.
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simultaneous liquid chromatographic assay of amantadine and its four related compounds in Phosphate Buffered Saline using 4 fluoro 7 nitro 2 1 3 benzoxadiazole as a fluorescent derivatization reagent
Biomedical Chromatography, 2006Co-Authors: Yasuhiko Higashi, Shota Nakamura, Hiroki Matsumura, Youichi FujiiAbstract:Simultaneous HPLC assay of 1-adamantanamine hydrochloride (amantadine) and its four related compounds [2-adamantanamine hydrochloride (2-ADA), 1-adamantanmethylamine (ADAMA), 1-(1-adamantyl)ethylamine hydrochloride (rimantadine) and 3,5-dimethyl-1-adamantanamine hydrochloride (memantine)] in Phosphate-Buffered Saline (pH 7.4) after pre-column derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) was developed. Phosphate-Buffered Saline samples were mixed with borate buffer and NBD-F solution in acetonitrile at 60°C for 5 min and injected into HPLC. Five derivatives were well separated from each other. The lower limits of detection of amantadine, 2-ADA, ADAMA, rimantadine and memantine were 0.008, 0.001, 0.0008, 0.0015 and 0.01 µg/mL, respectively. The coefficients of variation for intra- and inter-day assay were less than 6.4 and 8.2%, respectively. The method presented was applied to a binding study of these compounds to human α1-acid glycoprotein. While affinity constants and capacities for ADAMA, rimantadine and memantine were calculated by means of Scatchard plots, those for the others were not determined. ADAMA, rimantadine and memantine were bound with different affinities and capacities. These results indicate that NBD-F is a good candidate as a fluorescent reagent to simultaneously determine amantadine and its four related compounds by HPLC after pre-column derivatization. Our method can be applied to binding studies for protein. Copyright © 2005 John Wiley & Sons, Ltd.
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simultaneous liquid chromatographic assay of amantadine and its four related compounds in Phosphate Buffered Saline using 4 fluoro 7 nitro 2 1 3 benzoxadiazole as a fluorescent derivatization reagent
Biomedical Chromatography, 2006Co-Authors: Yasuhiko Higashi, Shota Nakamura, Hiroki Matsumura, Youichi FujiiAbstract:Simultaneous HPLC assay of 1-adamantanamine hydrochloride (amantadine) and its four related compounds [2-adamantanamine hydrochloride (2-ADA), 1-adamantanmethylamine (ADAMA), 1-(1-adamantyl)ethylamine hydrochloride (rimantadine) and 3,5-dimethyl-1-adamantanamine hydrochloride (memantine)] in Phosphate-Buffered Saline (pH 7.4) after pre-column derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) was developed. Phosphate-Buffered Saline samples were mixed with borate buffer and NBD-F solution in acetonitrile at 60 degrees C for 5 min and injected into HPLC. Five derivatives were well separated from each other. The lower limits of detection of amantadine, 2-ADA, ADAMA, rimantadine and memantine were 0.008, 0.001, 0.0008, 0.0015 and 0.01 microg/mL, respectively. The coefficients of variation for intra- and inter-day assay were less than 6.4 and 8.2%, respectively. The method presented was applied to a binding study of these compounds to human alpha(1)-acid glycoprotein. While affinity constants and capacities for ADAMA, rimantadine and memantine were calculated by means of Scatchard plots, those for the others were not determined. ADAMA, rimantadine and memantine were bound with different affinities and capacities. These results indicate that NBD-F is a good candidate as a fluorescent reagent to simultaneously determine amantadine and its four related compounds by HPLC after pre-column derivatization. Our method can be applied to binding studies for protein.