Simulated Physiological Solution Research Articles

The Effect of Metallographic Preparation on the Surface Characteristics and Corrosion Behaviour of Ti-6Al-4V Alloy in Simulated Physiological Solutions

Abstract This study aimed to determine the effect of surface metallographic preparation (grinding, diamond polishing, and chemo-mechanical polishing using silica and hydrogen peroxide) on the surface roughness, morphology, chemical composition, and electrochemical behaviour of Ti-6Al-4V alloy. Roughness decreases from ca. 0.2 m to 0.02 m from grinding to polishing. A typical + microstructure can be observed only after chemo-mechanical polishing. The average composition of ca. 6 wt.% Al, 4 wt.% V, and rest Ti was determined regardless of the surface preparation. X-ray phtotoelectron spectroscopy revealed that the thickness of the oxide layer formed on chemo-mechanical polished samples is half that of ground samples. The metallographic preparation largely affects the corrosion behaviour of Ti-6Al-4V, which was investigated using electrochemical impedance spectroscopy and potentiodynamic polarisation in 0.9 wt.% NaCl and artificial saliva at 37C. At the open circuit potential, the chemo-mechanically polished Ti-6Al-4 samples showed superior corrosion resistance over ground samples. At potentials over 2.5 V vs. Ag/AgCl, increased current densities were noted for chemo-mechanically polished samples, presumably related to the oxidation to a thicker oxide.

Surface treatments on 3D printed Ti6Al4V biomedical plates to enhance corrosion resistance in simulated physiological solutions and under inflammatory conditions

Ti6Al4V biomedical plates were fabricated by Laser Powder Bed Fusion using different process parameters. A slight influence of the laser energy density on mechanical properties and microstructure was revealed. Chemical etching allowed to make the surface of 3D samples uniform removing also spheres of unfused material. After etching some samples were anodized in calcium acetate and β-glycerolphosphate containing solution to grow a Ca and P containing porous TiO2 layers. The chemical etching improved the corrosion resistance of the alloy in simulated body fluid, while only after anodizing the alloys resulted to be corrosion resistant under inflammatory and severe inflammatory conditions.

Corrosion protection and antibacterial performance of a chitosan/salicylate coating electrogenerated on a magnesium alloy

In this work, chitosan and chitosan/salicylate coatings were prepared by EPD on AZ91D Mg alloy to improve the corrosion resistance of the substrate in a simulated physiological solution. The effect of two concentrations of salicylate on the morphology and anticorrosive behaviour of the coatings was evaluated. The results showed that the addition of 0.50 g/L sodium salicylate to the chitosan formulation decreased the corrosion rate of the chitosan coating from 0.0025 ± 0.0003 to 0.0007 ± 0.0004 mA cm−2. From the results of electrochemical impedance spectroscopy (EIS) and Fourier Transform Infrared (FTIR) analysis, it can be concluded that the presence of salicylate in the coating leads to a self-healing effect that contributes to an improved corrosion protection. In addition, the presence of salicylate in the coating has been shown to increase antibacterial activity against both Gram-positive and Gram-negative bacteria. It has been demonstrated that salicylate can be released from the coating, which has an anti-inflammatory effect. In this way, a novel chitosan/salicylate coating was developed for the first time on a Mg alloy for bactericidal effect, release of salicylate and corrosion protection in simulated physiological solution. So far, chitosan and salicylate have not been investigated as a combination for the development of multifunctional coatings on Mg alloys. In addition, the self-healing effect of salicylate ions in a chitosan coating was established for the first time.

Comparative Study on Passive Film Formation Mechanism of Cast and PBF-LB/M-TC4 in Simulated Physiological Solution.

Personalized laser powder bed fusion (PBF-LB/M) Ti-6Al-4V (TC4) has a broader application prospect than that of traditional casting. In this paper, the composition and corrosion resistance of the passive film formation mechanism of TC4 prepared by optimization of PBF-LB/M techniques and traditional casting were systematically studied in 0.9 wt.% NaCl at 37 °C by electrochemical technique and surface analysis. The rates of the passive film formation process, corrosion resistance and composition of TC4 show different characteristics for the different preparation processes. Although the rate of passive film formation of cast-TC4 was higher at the initial immersion, the open circuit potential was more positive, and the film thickness was larger after stabilization, those facts show no positive correlation with corrosion resistance. On the contrary, with no obvious defects on the optimized PBF-LB/M-TC4, the passive film resistance is 2.5 times more, the defect concentration is reduced by 30%, and the TiO2 content is higher than that of the cast-TC4, making the martensitic-based PBF-LB/M-TC4 exhibit excellent corrosion resistance. This also provides good technical support for the further clinical application of PBF-LB/M-TC4.

Electrochemical Surface Nanostructuring of Ti47Cu38Fe2.5Zr7.5Sn2Si1Ag2 Metallic Glass for Improved Pitting Corrosion Resistance

Ti‐based bulk metallic glasses are envisioned for human implant applications. Yet, while their elevated Cu content is essential for a high glass‐forming ability, it poses biocompatibility issues, necessitating a reduction in near‐surface regions. To address this, surface treatments that simultaneously generate protective and bioactive states, based on nanostructured Ti and Zr‐oxide layers are proposed. An electrochemical pseudo‐dealloying process using the bulk glass‐forming Ti47Cu38Fe2.5Zr7.5Sn2Si1Ag2 alloy is defined. Melt‐spun ribbons are immersed in hot concentrated nitric acid solution, monitoring the anodic polarization behavior. From the current density transient measurements, together with surface studies (field‐emission scanning electron microscopy, transmission electron microscopy, and Auger electron spectroscopy), the surface reactions are described. This nanostructuring process is divided into three stages: passivation, Cu dissolution, and slow oxide growth, leading to homogenous nanoporous and ligament structures. By tuning the applied potential, the pore and ligament sizes, and thickness values are adjusted. According to X‐ray photoelectron spectroscopy, these nanoporous structures are Ti and Zr‐oxides rich in hydrous and nonhydrous states. In a simulated physiological solution, for those treated glassy alloy samples, complete suppression of chloride‐induced pitting corrosion in the anodic regime of water stability is achieved. This high corrosion resistance is similar to that of clinically used cp‐Ti.

Shot peening of AZ31 magnesium alloy: role of surface microstructure and iron diffusion on corrosion behaviour

ABSTRACT In the present work, surface grain refined AZ31 magnesium (Mg) alloy was produced by shot peening (SP). X-ray diffraction analysis demonstrated iron diffusion into the surface of AZ31 Mg alloy during SP. Higher hardness, increased surface energy and decreased corrosion resistance were observed for the shot-peened surface due to nanostructured grains resulted from SP. From the immersion studies in a simulated physiological solution carried out for 3 days, higher level of biomineralization was observed for the shot peened AZ31 compared with the base alloy that dominated the adverse effect of iron diffusion in resisting the biocorrosion. The results suggest that the nano-structuring of AZ31 Mg alloy surface helps to enhance the biomineralization to control the degradation. However, the selection of processing medium is crucial to eliminate the effect of chemical composition change during the process in tailoring the corrosion behaviour of AZ31 Mg alloy for biomedical implant applications.

Sliding and Fretting Wear Behavior of Biomedical Ultrafine-Grained TiNbZrTaFe/Si Alloys in Simulated Physiological Solution.

This work investigated the wear behavior of ultrafine-grained Ti65Nb23.33Zr5Ta1.67Fe5 (at.%, TNZTF) and Ti65Nb23.33Zr5Ta1.67Si5 (at.%, TNZTS) alloys fabricated by high-energy ball milling and spark plasma sintering. Wear tests were conducted in a simulated physiological solution under both reciprocating sliding and fretting wear conditions with different loads, frequencies, and stroke lengths. The microstructures, mechanical properties, and anti-wear properties of the investigated alloys were characterized. The results showed that the TNZTF and TNZTS alloys had much less wear volume than the commonly used Ti-6Al-4V (TC4) alloy and commercially pure titanium (CP-Ti). The TNZTF and TNZTS alloys exhibited much more smooth wear surfaces and shallower wear scars compared with TC4 and CP-Ti. The investigated alloys exhibited different wear mechanisms under the reciprocating sliding wear conditions, while they were similar under the fretting wear conditions. Compared with TC4 and CP-Ti, the fabricated TNZTF and TNZTS alloys showed a substantially higher wear resistance, owing to their ultrafine-grained microstructure and superior hardness. Additionally, the addition of Nb and Zr further enhanced the wear resistance by forming a protective Nb2O5 and ZrO2 oxide film. This work provides guidance for designing new biomedical titanium alloys with excellent wear resistance.

Albumin Protein Impact on Early-Stage In Vitro Biodegradation of Magnesium Alloy (WE43).

Mg and its alloys are promising biodegradable materials for orthopedic implants and cardiovascular stents. The first interactions of protein molecules with Mg alloy surfaces have a substantial impact on their biocompatibility and biodegradation. We investigate the early-stage electrochemical, chemical, morphological, and electrical surface potential changes of alloy WE43 in either 154 mM NaCl or Hanks' simulated physiological solutions in the absence or presence of bovine serum albumin (BSA) protein. WE43 had the lowest electrochemical current noise (ECN) fluctuations, the highest noise resistance (Zn = 1774 Ω·cm2), and the highest total impedance (|Z| = 332 Ω·cm2) when immersed for 30 min in Hanks' solution. The highest ECN, lowest Zn (1430 Ω·cm2), and |Z| (49 Ω·cm2) were observed in the NaCl solution. In the solutions containing BSA, a unique dual-mode biodegradation was observed. Adding BSA to a NaCl solution increased |Z| from 49 to 97 Ω·cm2 and decreased the ECN signal of the alloy, i.e., the BSA inhibited corrosion. On the other hand, the presence of BSA in Hanks' solution increased the rate of biodegradation by decreasing both Zn and |Z| while increasing ECN. Finally, using scanning Kelvin probe force microscopy (SKPFM), we observed an adsorbed nanolayer of BSA with aggregated and fibrillar morphology only in Hanks' solution, where the electrical surface potential was 52 mV lower than that of the Mg oxide layer.

Pit initiation on biomedical alloys-A review.

Biomedical alloys, like many engineering alloys, have chemical or physical heterogeneities at the surface, and such heterogeneities can potentially act as sites for pit initiation. Alloys of particular interest are 316/316L (and 316LVM) stainless steel, nitinol, and CoCr alloys. This review focuses on the sites-generally inclusions-that have been associated with pitting in various studies of biomedical alloys in simulated physiological solutions. The effect of these sites is discussed in relation to factors such as type and size. For both 316/316L stainless steel and nitinol, pitting has been found to initiate at two different types of inclusions: sulfide and oxide inclusions in stainless steel, and carbide and oxide inclusions in nitinol. Sulfide inclusions tend to be the predominant sites for pitting on 316/316L stainless steel, while there is some evidence to suggest that carbide inclusions may be more effective than oxide inclusions for pitting on nitinol. CoCrMo alloys differ from the other two alloys in that, although particles can be present in the form of carbides, the carbides typically do not provide sites for pit initiation except possibly for alloys with a high-C content, certain heat treatments, and when anodically polarized to high potentials. CoNiCrMo differs further in that TiN inclusions can be present in the vicinity of pits and might be associated with them, but irrespective of the initiation site, any pits are unlikely to grow because of repassivation.

Comparison of colorimetric, spectroscopic and electrochemical techniques for quantification of hydrogen sulfide.

Background: Hydrogen sulfide (H2S), an endogenous gasotransmitter, has potential applications in several conditions. However, its quantification in simulated physiological solutions is a major challenge due to its gaseous nature and other physicochemical properties. Aim: This study was designed tocomparefour commonly used H2S detection and quantification methods in aqueous solutions. Methods: The four techniques compared were one colorimetric, one chromatographicand two electrochemical methods. Results: Colorimetric and chromatographic methodsquantified H2S in millimolar and micromole ranges, respectively. The electrochemical methods quantified H2S in the nanomole and picomole ranges and were less time-consuming. Conclusion: The H2S quantification method should be selected based on the specific requirements of a research project in terms ofsensitivity, response timeand cost-effectiveness.

Development of a novel NiCu nanoparticle-loaded polysaccharide-based hydrogel for 3D printing of customizable dressings with promising cytotoxicity against melanoma cells.

Polysaccharide hydrogels and metal alloy nanoparticles have already found use in a range of biomedical applications. Nickel-copper nanoparticles (NiCu NPs) are particularly promising due to their tunable properties, such as ferromagnetism, biocompatibility, and antimicrobial activity. At the same time, polysaccharide hydrogels made of polymer mixtures such as alginate and methylcellulose with incorporated metal alloy nanoparticles are reported in the scientific literature. In view of this, in this work, NiCu NPs are combined with polysaccharide hydrogels and 3D printed to construct geometrically customizable dressings with tailorable properties for melanoma treatment. This novel combination exploits the intrinsic magnetic properties of NiCu NPs and the same time builds on their less known properties to improve the mechanic stability of 3D printed materials, both contributing to a previously not reported application as potent cytotoxic dressing against melanoma cells. The dressings were evaluated in terms of their physico-chemical characteristics, and their potential application, namely melanoma cell cytotoxicity. While all dressings exhibited similar degradation profiles regardless of composition, the addition of NiCu NPs had an effect on the hydrophilicity, swelling rates, and topographical properties of the dressings. Compression results showed that the presence of NPs increased the stiffness of the dressings, while the ultimate tensile strength was highest at 0.31MPa for the dressings with 0.5wt% NPs. We show that although the base formulation of the dressings is biocompatible with skin-derived cells, dressings loaded with NPs exhibit promising antimelanoma activity. Extracts obtained from dressings containing 0.5wt% NPs reduced melanoma cell viability to 61%±11% and 40%±2% after 24h and 72h of soaking, respectively. Furthermore, extracts of dressings with 1wt% NPs reduced melanoma cell viability to less than 15% within the first 24h. By adjusting the NP content, the mechanical properties, surface roughness, and wettability can be tuned so that the dressings can be functionally customized. In addition, by using 3D printing as a fabrication process, the shape and composition of the dressings can be tailored to the patient's needs. The dressings also remained intact after soaking in simulated physiological solution for 14 days, indicating their suitability for long-term topical application.

Effect of Mo content on the passivation and localized corrosion behavior of laser engineered net shaped (LENS) Co-Cr-Mo alloys in a simulated physiological solution

Effect of Mo content on the passivation and localized corrosion behavior of laser engineered net shaped (LENS) Co-Cr-Mo alloys in a simulated physiological solution

Silk Fibroin/ZnO Coated TiO2 Nanotubes for Improved Antimicrobial Effect of Ti Dental Implants.

The aim of the present research is to develop a novel hybrid coating for a Ti dental implant that combines nature-inspired biomimetic polymers and TiO2 nanostructures with an entrapped ZnO antimicrobial agent. ZnO was used in other studies to cover the surface of Ti or Ti-Zr to reduce the need of clinical antibiotics, prevent the onset of peri-implantitis, and increase the success rate of oral clinical implantation. We developed an original coating that represents a promising approach in clinical dentistry. The titanium surface was first anodized to obtain TiO2 nanotubes (NT). Subsequently, on the NT surface, silk fibroin isolated from Bombyx mori cocoons was deposited as nanofibers using the electrospun technique. For an improved antibacterial effect, ZnO nanoparticles were incorporated in this biopolymer using three different methods. The surface properties of the newly created coatings were assessed to establish how they are influenced by the most important features: morphology, wettability, topography. The evaluation of stability by electrochemical methods in simulated physiological solutions was discussed more in detail, considering that it could bring necessary information related to the behavior of the implant material. All samples had improved roughness and hydrophilicity, as well as corrosion stability (with protection efficiency over 80%). The antibacterial test shows that the functional hybrid coating has good antibacterial activity because it can inhibit the proliferation of Staphylococcus aureus up to 53% and Enterococcus faecalis up to 55%. All Ti samples with the modified surface have proven superior properties compared with unmodified TiNT, which proved that they have the potential to be used as implant material in dentistry.

Electrochemical Investigation of the Corrosion Resistance of Ti20Mo Alloys in Simulated Physiological Solution with Added Proteins for Biomaterial Application

Electrochemical Investigation of the Corrosion Resistance of Ti20Mo Alloys in Simulated Physiological Solution with Added Proteins for Biomaterial Application

In vitro and in vivo removal efficacy of insoluble Prussian blue in combination with calcium polystyrene sulfonate for thallium.

The similarities between thallium and potassium have suggested the use of calcium polystyrene sulfonate (CPS), an oral ion exchange resin, as a potential agent against thallium intoxication. Therefore, the study was an attempt to evaluate the efficacy of CPS and Prussian blue when given alone or in combination against thallium toxicity. The effect on binding capacity was investigated in terms of contact time, amount of CPS, influence of pH, simulated physiological solutions and interference of potassium ions. Also, rats were given single dose of thallium chloride (20mgkg-1) and the treatment with PB and CPS was given for 28days as CPS 30gkg-1, orally, twice a day, PB 3gkg-1, orally, twice a day and their combination. The effect of antidotal treatment was evaluated by calculating the thallium levels in various organs, blood, urine and feces. The results of the in vitro study indicated exceedingly quick binding in the combination of CPS and PB as compared to PB alone. Also, it was found that the binding capacity at pH 2.0 was considerably increased for PB with CPS (184.656mgg-1) as compared to PB (37.771mgg-1). Furthermore, statistically significant results were obtained in the in vivo study as after 7th day, thallium levels in blood of rats treated with combination were reduced by 64% as compared to control group and 52% as compared to alone PB treated group. Also, Tl retention in liver, kidney, stomach, colon and small intestine of combination treated rats was significantly reduced to 46%, 28%, 41%, 32% and 33% respectively, as compared to alone PB treated group. These findings demonstrate this as a good antidotal option against thallium intoxication.

Synthesis of hydroxyapatite from eggshell and its electrochemical characterization as a coating on titanium

This work reports the surface modification of titanium through the deposition of a hydroxyapatite coating synthesized from natural sources. Hydroxyapatite was synthesized from eggshell using a wet precipitation method. It was deposited as a coating on a Ti surface using electrophoretic deposition (EPD) at different electrophoretic deposition times and voltages. The electrochemical evaluation of the obtained coatings was performed through potentiodynamic polarization curves in a simulated physiological solution. The results showed that the eggshell is an excellent alternative for the synthesis of hydroxyapatite, and that its heat treatment at 700 °C shows the best crystallinity conditions. The optimum conditions for deposition of the hydroxyapatite coatings were 30 V and 18 min. Potentiodynamic polarization tests showed that hydroxyapatite coatings improve the chemical stability of the Ti surface when subjected to the corrosive action of simulated physiological solutions at 37 °C.

Titanium Implant Alloy Modified by Electrochemically Deposited Functional Bioactive Calcium Phosphate Coatings

Calcium phosphate-based (CaP) bioceramic materials are widely used in the field of bone regeneration, both in orthopaedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The formation of CaP coatings on high-strength implant materials such as titanium alloys combines the superior mechanical properties of metals with the osteoconductive properties of CaP materials. In this work, the electrochemically assisted deposition of CaP coatings on the titanium alloy, TiAlNb, which is commonly used commercially as an implant material in orthopaedic devices, was examined. The barrier properties (electronic properties) of unmodified and CaP-modified titanium alloy were tested in situ in a simulated physiological solution, Hanks’ solution, under in vitro conditions of real implant applications using electrochemical impedance spectroscopy (EIS). The morphology and microstructure of the obtained CaP deposit were characterised by scanning electron microscopy (SEM) and chemical composition was assessed by energy dispersive X-ray spectroscopy (EDS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The aim was to investigate the effect of calcium phosphate CaP coating on the corrosion resistance of the titanium TiAlNb alloy and to understand better the deposition process in the production of bioactive functional coatings on metallic implant materials.

Development of Dipeptide N-acetyl-L-cysteine Loaded Nanostructured Carriers Based on Inorganic Layered Hydroxides.

N-acetyl-L-cysteine (NAC), a derivative of the L-cysteine amino acid, presents antioxidant and mucolytic properties of pharmaceutical interest. This work reports the preparation of organic-inorganic nanophases aiming for the development of drug delivery systems based on NAC intercalation into layered double hydroxides (LDH) of zinc-aluminum (Zn2Al-NAC) and magnesium-aluminum (Mg2Al-NAC) compositions. A detailed characterization of the synthesized hybrid materials was performed, including X-ray diffraction (XRD) and pair distribution function (PDF) analysis, infrared and Raman spectroscopies, solid-state 13carbon and 27aluminum nuclear magnetic resonance (NMR), simultaneous thermogravimetric and differential scanning calorimetry coupled to mass spectrometry (TG/DSC-MS), scanning electron microscopy (SEM), and elemental chemical analysis to assess both chemical composition and structure of the samples. The experimental conditions allowed to isolate Zn2Al-NAC nanomaterial with good crystallinity and a loading capacity of 27.3 (m/m)%. On the other hand, NAC intercalation was not successful into Mg2Al-LDH, being oxidized instead. In vitro drug delivery kinetic studies were performed using cylindrical tablets of Zn2Al-NAC in a simulated physiological solution (extracellular matrix) to investigate the release profile. After 96 h, the tablet was analyzed by micro-Raman spectroscopy. NAC was replaced by anions such as hydrogen phosphate by a slow diffusion-controlled ion exchange process. Zn2Al-NAC fulfil basic requirements to be employed as a drug delivery system with a defined microscopic structure, appreciable loading capacity, and allowing a controlled release of NAC.

Role of copper in tribological properties of hydrogenated amorphous carbon films in simulated physiological solution

The properties and tribological behaviors of a-C:H:Cu films with different copper contents in various simulated body fluids (deionized water, saline solution and bovine serum albumin solution (BSA), respectively) were studied. After copper incorporation, the unsaturated sp2-CH2 content in the film increased, resulting in declining wear resistance in deionized water. Nonetheless, as the copper content increased, the wear resistance of the a-C:H:Cu film in saline solution was enhanced compared with that in water, which was attributed to the obvious graphitization of wear debris promoted by copper. In BSA solution, copper incorporation improved the protein adsorption capacity of the film and facilitated the formation of denatured albumin with non-native β-sheet structures during friction, significantly improving the wear resistance of the film.

Corrosion Behavior of Different Types of Stainless Steel in PBS Solution

Anodic and spontaneous corrosion of different types of stainless steel (AISI 304L, AISI 316L and 2205 DSS) in phosphate-buffered saline solution (PBS, pH = 7.4) at 37 °C (i.e., in simulated physiological solution in the human body) were examined using open circuit potential measurements, linear and cyclic polarization, and electrochemical impedance spectroscopy methods. After the anodic and spontaneous corrosion, the surface of the tested samples was investigated by light and scanning electron microscopy (SEM) with EDS analysis. It has been established that the tendency of the examined steel materials towards local corrosion decreases in the order: AISI 304L < AISI 316L < 2205 DSS. Namely, the possibility of repassivation and the resistance to local corrosion increases in the same order. The corrosion resistance of steel samples at open circuit potential is a consequence of forming a natural oxide film with a bi-layer structure and consists of an inner barrier and an outer porous film. The inner barrier film has a small thickness and extremely high resistance, while the outer porous film is much thicker but also has significantly lower resistance. The inner barrier layer mainly prevents corrosion of examined steel samples in order: AISI 304L < AISI 316L < 2205 DSS. Light microscopy and SEM/EDS analysis after pitting and spontaneous corrosion showed damage on the AISI 304L and AISI 316L surface, while the surface of 2205 DSS was almost undamaged by corrosion.