scholarly journals Hydroxyapatite and Silicon-Modified Hydroxyapatite as Drug Carriers for 4-Aminopyridine

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1124
Author(s):  
Laura Marincaș ◽  
Graziella Liana Turdean ◽  
Monica Toșa ◽  
Zsolt Kovács ◽  
Béla Kovács ◽  
...  

Adsorption and desorption properties of nano-hydroxyapatite (HAP) and silicon-modified hydroxyapatite (Si–HAP) were investigated with 4-aminopyridine (fampridine-4AP). The novelty of this research is the investigation of the suitability of the previously mentioned carriers for drug-delivery of 4AP. UV-VIS spectrophotometric results showed that the presence of silicon in the carrier did not significantly affect its adsorption capacity. The success of the adsorption was confirmed by thermal analysis (TG/DTA), scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), Fourier transform infrared (FTIR) spectroscopy, and X-ray powder diffraction (XRPD). Drug release experiments, performed in simulated body fluid (SBF), revealed a drug release from Si–HAP that was five times slower than HAP, explained by the good chemical bonding between the silanol groups of the carrier and the 4AP functional groups. The electrochemical measurements showed a value of the polarization resistance of the charge transfer (Rct) more than five times smaller in the case of Si–HAP coating loaded with 4AP, so the charge transfer process was hindered. The electrochemical impedance results revealed that electron transfer was inhibited in the presence of 4AP, in concordance with the previously mentioned strong bonds. The silicon substitution in HAP leads to good chemical bonding with the drug and a slow release, respectively.

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 903 ◽  
Author(s):  
El-Sayed M. Sherif ◽  
Sameh A. Ragab ◽  
Hany S. Abdo

The manufacturing of different Ti-6Al-xV (x = 2, 4, 6, and 8 wt.%) alloys using a mechanical alloying technique was reported. The corrosion behaviors of these newly fabricated alloys after 1, 24, and 48 h exposure to a simulated body fluid (SBF) were assessed using cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, and chronoamperometric measurements. Surface morphology and elemental analyses after corrosion for 48 h in SBF were reported using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) examinations. An X-ray diffraction investigation characterized the phase analyses. All results indicated that the increase of V content significantly decreases both uniform and pitting corrosion. This effect also increases with prolonging the immersion time to 48 h before measurement.


2015 ◽  
Vol 6 (1) ◽  
pp. 33 ◽  
Author(s):  
L. J. Reyes Jaimes ◽  
H. A. González Romero ◽  
A. Sandoval Amadora ◽  
D. Y. Peña Ballesteros ◽  
H. A. Estupiñán Durán

ResumenSe evaluó el efecto del pH de fluido corporal simulado en la formación de apatitas y en la degradación de superficies de la aleación Ti6Al4V recubiertas con Fosfato de Calcio mediante la técnica de lectrodeposición catódica. Como variables de estudio se tomaron el pH del fluido corporal simulado y el tiempo de inmersión de los recubrimientos. Mediante microscopia electrónica de barrido, espectroscopia de energía dispersiva, difracción de rayos X y absorción atómica se pudo corroborar la formación de apatitas, y la degradación de los recubrimientos se evaluó mediante Espectroscopia de impedancia electroquímica y curvas de polarización potenciodinámicas. Los resultados obtenidos muestran que los recubrimientos tenían altas concentraciones de Fluorapatita (Ca5(PO4)3F) y que su formación se ve favorecida a medida que el pH del fluido corporal simulado y el tiempo de inmersión aumenta. Por otra parte, se obtuvo que las muestras evaluadas a pH de 7,2 son menos estables termodinámicamente, sin embargo, las evaluadas a 7,6 presentan una superficie más activa, por lo que se obtiene una mayor velocidad de degradación. AbstractThe pH eect of a Simulated Body Fluid in the apatite formation and the degradation of the Ti6Al4V alloy surfaces, coated by calcium phosphate obtained through cathodic electrodeposition was evaluated. The simulated body fluid pH and the coating immersion time were taken as variables. The formation of apatite was corroborated by Scanning Electron Microscopy, Energy Dispersive Spectroscopy, X Ray Diraction and Atomic Absorption Techniques. The coating degradation was assessed by the Electrochemical Impedance Spectroscopy and the Potential Dynamic Polarization Curves. The results have shown that the coatings had high concentrations of fluorapatite (Ca5(PO4)3F) and its formation was favored as the simulated body fluid pH and the immersion time increases. Moreover, it was found that the coatings samples evaluated at pH 7.2 were less thermodynamically steady, however, the evaluated coating at pH 7.6 exhibited a more active surface, so that a higher rate of degradation is obtained.


2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
El-Sayed M. Sherif ◽  
Asiful H. Seikh

The effect of exposure time and 5-phenyl-1H-tetrazole on the corrosion and corrosion mitigation of cobalt free maraging steel in 0.5 M H2SO4pickling solutions has been reported using electrochemical and spectroscopic investigations. Potentiodynamic polarization data showed that the increase of immersion time from 0 min to 120 min increases the corrosion rate and decreases the polarization resistance of the maraging steel. On the other hand, the addition of PHTA and the increase of its concentration decrease all the corrosion parameters of the steel at all exposure test periods. Electrochemical impedance spectroscopy measurements agreed with the obtained polarization data. Scanning electron spectroscopy and energy dispersive X-ray investigations confirmed that the inhibition of the steel corrosion is achieved via the adsorption of the PHTA molecules onto the steel precluding its surface from being dissolved.


2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
El-Sayed M. Sherif ◽  
Adel Taha Abbas ◽  
D. Gopi ◽  
A. M. El-Shamy

The corrosion and corrosion inhibition of high strength low alloy (HSLA) steel after 10 min and 60 min immersion in 2.0 M H2SO4solution by 3-amino-1,2,4-triazole (ATA) were reported. Several electrochemical techniques along with scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) were employed. Electrochemical impedance spectroscopy indicated that the increase of immersion time from 10 min to 60 min significantly decreased both the solution and polarization resistance for the steel in the sulfuric acid solution. The increase of immersion time increased the anodic, cathodic, and corrosion currents, while it decreased the polarization resistance as indicated by the potentiodynamic polarization measurements. The addition of 1.0 mM ATA remarkably decreased the corrosion of the steel and this effect was found to increase with increasing its concentration to 5.0 mM. SEM and EDS investigations confirmed that the inhibition of the HSLA steel in the 2.0 M H2SO4solutions is achieved via the adsorption of the ATA molecules onto the steel protecting its surface from being dissolved easily.


Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 659
Author(s):  
Rebeka Rudolf ◽  
Aleš Stambolić ◽  
Aleksandra Kocijan

Nitinol is a group of nearly equiatomic alloys composed of nickel and titanium, which was developed in the 1970s. Its properties, such as superelasticity and Shape Memory Effect, have enabled its use, especially for biomedical purposes. Due to the fact that Nitinol exhibits good corrosion resistance in a chloride environment, an unusual combination of strength and ductility, a high tendency for self-passivation, high fatigue strength, low Young’s modulus and excellent biocompatibility, its use is still increasing. In this research, Atomic Layer Deposition (ALD) experiments were performed on a continuous vertical cast (CVC) NiTi rod (made in-house) and on commercial Nitinol as the control material, which was already in the rolled state. The ALD deposition of the TiO2 layer was accomplished in a Beneq TFS 200 system at 250 °C. The pulsing times for TiCl4 and H2O were 250 ms and 180 ms, followed by appropriate purge cycles with nitrogen (3 s after the TiCl4 and 2 s after the H2O pulses). After 1100 repeated cycles of ALD depositing, the average thickness of the TiO2 layer for the CVC NiTi rod was 52.2 nm and for the commercial Nitinol, it was 51.7 nm, which was confirmed by X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscope (SEM) using Energy-dispersive X-ray (EDX) spectroscopy. The behaviour of the CVC NiTi and commercial Nitinol with and without the TiO2 layer was investigated in a simulated body fluid at body temperature (37 °C) to explain their corrosion resistance. Potentiodynamic polarisation measurements showed that the lowest corrosion current density (0.16 μA/cm2) and the wider passive region were achieved by the commercial NiTi with TiO2. Electrochemical Impedance Spectroscopy measurements revealed that the CVC NiTi rod and the commercial Nitinol have, for the first 48 h of immersion, only resistance through the oxide layer, as a consequence of the thin and compact layer. On the other hand, the TiO2/CVC NiTi rod and TiO2/commercial Nitinol had resistances through the oxide and porous layers the entire immersion time since the TiO2 layer was formatted on the surfaces.


1991 ◽  
Vol 69 (6) ◽  
pp. 720-725 ◽  
Author(s):  
D. C. Khan ◽  
P. K. Khowash

The aim of this work is to study theoretically the electronic structure of a number of ionic and covalent solids. The charges within each atomic region are calculated and a charge-transfer diagram is introduced to define a measure of the chemical bonding (ionic and (or) covalent) in these systems. The crystal-field splitting, 10 Dq, is determined for crystals with a 3d cation from the one-electron energy spectra and compared with available experiments. The transition between two of the valence levels is calculated wherever the corresponding X-ray photoelectron spectrometry or optical spectroscopic experimental data exist in the literature. Finally, the Mössbauer isomer shifts are calculated for iron containing samples.


Author(s):  
S. L. Hill ◽  
K. Krishnan ◽  
J. R. Ferraro

Certain classes of organic charge-transfer salts demonstrate superconducting behavior at liquid helium temperatures. Single crystal x-ray diffraction and infrared microreflectance analysis have been performed on several conducting systems to associate the nature of the crystalline structure with the electrical conductivity. The infrared spectrum for a single crystal salt exhibits absorptions which correlate with superconducting behavior.Discussion Williams and coworkers have performed x-ray Crystallography experiments to demonstrate the presence of an anion cavity between radical cation stacks- of bis(ethylenedithio)- tetrathiafulvalene (ET). The sulfur…sulfur interstack distance in a beta or kappa phase salt assumes a value less than the Vanderwaals distance and exhibit a superconducting (two dimensional) metal behavior (verified by Fermi surface calculations) at 1-20K. The structures of alpha and beta phase ET2I3 suggest the potential for several potential intermolecular interaction modes. It may be observed that the beta phase permits both interstack as well as H … X anionic interactions, whereas these interactions are less likely to occur in the alpha phase.


Author(s):  
Hayette Faid

AbstractIn this work, Zn-Ni alloys have been deposited on steel from sulfate bath, by electrodeposition method. The effect of Zn content on deposits properties was studied by cyclic voltammetry (CV), chronoaperometry (CA), linear stripping voltammetry (ALSV) and diffraction (XRD) and scanning electronic microscopy (SEM). The corrosion behavior in 3.5 wt. NaCl solution was examined using anodic polarization test and electrochemical impedance spectroscopy. X-ray diffraction of show that Zn-Ni alloys structure is composed of δ phase and γ phase, which increase with the decrease of Zn content in deposits. Results show that deposits obtained from bath less Zn2+ concentration exhibited better corrosion resistance.


Sign in / Sign up

Export Citation Format

Share Document