Simulated Body Fluid Conditions Research Articles

Effect of Different Forms of Anionic Nanoclays on Cytotoxicity

Anionic nanoclays, so-called layered double hydroxide (LDH) nanoparticles, have been extensively applied as drug delivery systems, since they efficiently enter cells via endocytosis pathway and possess controlled release property. However, the stability of LDHs varies, depending on the type of interlayer anions, which can also affect their toxicity. In this study, we investigated the effects of two different forms of LDH, carbonate form (MgAl-LDH-CO3) and chloride form (MgAl-LDH-Cl), on cytotoxicity in human lung epithelial cells. The result showed that MgAl-LDH-Cl was more easily dissolved into metal ions under simulated lysosomal (pH 4.5) and body fluid (pH 7.4) conditions than did MgAl-LDH-CO3. According to cytotoxicity evaluation, MgAl-LDH-CO3 exhibited high toxicity compared with MgAl-LDH-Cl in terms of induction of oxidative stress, apoptosis and membrane damage. These results suggest that easily dissoluble MgAl-LDH-Cl has low cytotoxicity, while high stability of MgAl-LDH-CO3 is correlated to elevated cytotoxicity.

Corrosion and tribological properties and impact fatigue behaviors of TiN- and DLC-coated stainless steels in a simulated body fluid environment

In this study, the corrosion and tribological properties of TiN and DLC coatings were investigated in a simulated body fluid (SBF) environment. The ball-on-plate impact tests were conducted on the coatings under a combined force of a 700 N static load and a 700 N dynamic impact load for 10,000 impacting cycles. The results indicated that the TiN and DLC coatings could achieve a higher corrosion polarization resistance and a more stable corrosion potential in the SBF environment than the uncoated stainless steel substrate SS316L. The good corrosion protection performance of TiN could be due to the formation of a Ti–O passive layer on the coating surface, which protected the coating from further corrosion. The superior corrosion property of the DLC coating was likely attributed to its chemical inertness under the SBF condition. The TiN and DLC coatings also exhibited an excellent wear resistance and chemical stability during the sliding tests against a high density polyethylene (HDPE) biomaterial. Compared to the DLC coating, the TiN coating has a better compatibility with the HDPE. However, the impact tests showed that the fatigue cracks and the coating chipping occurred on the TiN coating but not on the DLC coating.

Fretting wear behavior of calcium phosphate-mullite composites in dry and albumin-containing simulated body fluid conditions

In a recent work, it has been shown that it is possible to achieve a better combination of compressive strength, flexural strength and toughness properties in calcium phosphate (CaP) composites containing 20 and 30 wt% mullite (3Al(2)O(3).2SiO(2)). In view of their potential application as load bearing implants, the present work reports the friction and wear properties of the newly developed composites against zirconia under dry ambient as well as in simulated body fluid (SBF) containing bovine serum albumin (BSA) protein. For comparison, experiments were also conducted on monolithic hydroxyapatite (HAp, Ca(10)(PO(4))(6)(OH)(2)) and mullite under identical conditions. Under the investigated fretting conditions, the mullite-containing composites exhibited higher coefficient of friction (COF) of 0.4-0.6, compared to pure HAp (COF approximately 0.25-0.3). Although the wear resistance of the composites containing 20 or 30 wt% mullite was better in dry conditions, higher wear rate was measured in SBF conditions. The difference in tribological properties has been analyzed in reference to the difference in phase assemblage and mechanical properties. A comparison with some competing biomaterials reveals good potential of the investigated CaP-mullite composites for application as wear resistant implants.

Potentiodynamic behaviour of Ti alloys in physiological solution containing lubricant

Ti based alloys are finding wide spread usage in various biomedical applications including joint replacement. The corrosion behaviour of these alloys in simulated body fluid conditions in the presence of lubricant is not reported so far. Thus, present work is undertaken to understand the influence of the lubricant on potentiodynamic behaviour of three types of Ti alloy, namely commercially pure (C.P.) Ti having α structure, Ti-6Al-4Fe having α + β structure and Ti-13Ta-29Nb-4.6Zr having β structure in Ringer's solution. The results show that lubrication does not alter the corrosion rates of single-phase alloys, which have low corrosion rates. However, it significantly reduces the corrosion rates of alloy Ti-6Al-4Fe having α + ß structure.

Nano-porous surface states of Ti–Y–Al–Co phase separated metallic glass

A novel nano-porous state was fabricated at the surface of the Ti-based metallic glass by selective etching technique. By transforming the surface of the Ti 45Y 11Al 24Co 20 phase separated alloy from smooth towards rough with nano-pores in an oxidised state, the passivation behaviour of the glassy alloy in simulated body fluid condition was remarkably improved leading to corrosion resistance significantly higher than that of the Ti–6Al–4V alloy, one of the favourite candidate materials for implant applications.

A study on the in vitro degradation properties of poly( l-lactic acid)/β-tricalcuim phosphate(PLLA/β-TCP) scaffold under dynamic loading

The objective of this study was to investigate the effects of dynamic loading on the in vitro degradation properties of poly( l-lactic acid)/β-tricalcuim phosphate(PLLA/β-TCP) composite scaffolds. These scaffolds were prepared by a technique, namely solvent self-proliferating/model compressing/particulate leaching, and they were incubated in a customized simulated body fluid (SBF) flow system under dynamic loading conditions for 6 weeks. The bioactivity and the degradation behaviors of the composite scaffolds were systematically investigated through the formation of apatite, the mass and porosity changes, the molecular weight changes of PLLA, the compressive strength changes, etc. Results show a high level of apatite deposition on the scaffolds, suggesting their good bioactivity in the SBF. Changes in mass, porosity, molecular weight and compressive strength of the scaffolds happened more under dynamic loading conditions than that under flow only SBF conditions. Dynamic loading with the investigated frequency promoted the degradation of the scaffolds, but did not markedly deteriorate the mechanical properties of the scaffolds. All the results suggest that the composite scaffolds have great potential to be applied in bone replacements or repairs under the in vivo load-bearing conditions.

Tribological investigation of novel HDPE‐HAp‐Al2O3 hybrid biocomposites against steel under dry and simulated body fluid condition

Among various biocompatible polymers, polyethylene based materials have received wider attention because of its excellent stability in body fluid, inertness, and easy formability. Attempts have been made to improve their physical properties (modulus/strength) to enable them to be used as load bearing hard tissue replacement applications. Among such attempts, high density polyethylene (HDPE)-hydroxyapatite (HAp) composite (HAPEX), has already been developed for total hip replacement (THR) acetabular cup and low load bearing bone tissue replacement. In the present work, alumina has been added as a partial replacement of HAp phase to improve the mechanical and tribological properties of the HAPEX composite. In an attempt to assess the suitability of the developed composite in THR application, the tribological properties against steel counterbody under both in air and simulated body fluid (SBF), have been investigated and efforts have been made to understand the wear mechanisms. The fretting wear study indicates the possibility of achieving extremely low COF (Coefficient of Friction approximately 0.09) as well as higher wear resistance (order of 10(-6) mm(3)/N m) with the newly developed composites in SBF. A low wear depth of approximately 4.6-5.3 microm is recorded, irrespective of fretting environment. The implication of the work is that optimal and combined addition of bioactive and bioinert ceramic filler to HDPE can provide a good opportunity to obtain hybrid biocomposites with better combination of physical properties (modulus, hardness) as well as low friction and high wear resistance.

A comparative study of the in vitro degradation of poly( l-lactic acid)/β-tricalcium phosphate scaffold in static and dynamic simulated body fluid

Porous poly( l-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) composite is a new promising scaffold for bone tissue engineering. Porous scaffolds fabricated by liquid anti-solvent precipitation principle were subjected to degradation in dynamic simulated body fluid (DSBF) and in static simulated body fluid (SSBF) at 37 °C for 24 weeks, respectively. Results indicated that a large number of apatite layer were formed on the scaffolds. The results further indicated that SBF flow decreased the degradation rate of molecular weight and compressive strength significantly. The porosity and mass changes were related to the apatite formation and SBF flow. All the results might be owed to the mutual effects of the flow of SBF and the addition of β-TCP. The degradation rate of scaffolds could be adjusted by the additional fraction of β-TCP to meet the requirements of application in vivo.

Tribological investigation of tantalum boride coating under dry and simulated body fluid conditions

Tantalum is known to be a highly corrosion resistant refractory metal. Boronized tantalum has potential use in machinery components, structures and as a bearing material in joint implants due to its high corrosive resistance and hardness. In this research, the friction and wear characteristics of boronized tantalum were studied against bearing steel E52100 under dry and simulated body fluid (SBF) conditions. Results showed that SBF caused tribochemical reactions leading to an increase in friction corresponding with amorphous debris. Fatigue cracks formed under dry conditions and tribochemical wear cracks formed under SBF conditions.

A Study of Bone-Like Apatite Formation on β-TCP/PLLA Scaffold in Static and Dynamic Simulated Body Fluid

The ability of apatite to form on the surface of biomaterials in simulated body fluid (SBF) has been widely used to predict the bone-bonding ability of bioceramic and bioceramic/polymer composites in vivo. Porous β-tricalcium phosphate/poly(L-lactic acid) (β-TCP/PLLA) composite scaffold was synthesized by new method. The ability of inducing calcium phosphate (Ca-P) formation was compared in static simulated body fluid(sSBF) and dynamic simulated body fluid (dSBF). The Ca-P morphology and crystal structures were identified using SEM, X-ray diffraction and Fourier transform infrared (FT-IR) spectroscopy. The results showed that the typical features of bone-like apatite formation on the surface and the inner pore wall of β-TCP/PLLA. Ca-P formation on scaffold surfaces in dSBF occurred slower than in sSBF and was more difficult with increasing flow rate of dSBF. The ability of apatite to form on β-TCP/PLLA was enhanced by effect of each other that has different degradable mechanism. Porous β-TCP/PLLA composite scaffold indicates good ability of Ca-P formation in vitro.

Corrosion behaviour of Ti–6Al–7Nb and Ti–6Al–4V ELI alloys in the simulated body fluid solution by electrochemical impedance spectroscopy

The corrosion behaviour of Ti–6Al–7Nb and Ti–6Al–4V ELI (extra low interstitial) was investigated as a function of immersion hours in simulated body fluid (SBF) condition, utilizing potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) techniques. Polarisation experiments were conducted after 0, 120, 240 and 360 h of immersion in SBF solution. From the polarisation curves, very low current densities were obtained for Ti–6Al–7Nb alloy compared to Ti–6Al–4V ELI, indicating a formation of stable passive layer. Impedance spectra were represented in the form of Bode plots and it was fitted using a non-linear least square (NLLS) fitting procedure, in which it exhibited a two time constant system suggesting the formation of two layers. The surface morphology of the titanium alloys have been characterized by SEM and EDAX measurements.

A Tribological Comparison of Pure and Boronized Chromium

Boronized metals are potential candidate materials for various industrial applications as well as for joint arthroplasty. This is due to their high hardness and corrosion resistance. In the present research, we investigated the tribological performance of boronized chromium when worn against bearing steel E52100. Pure chromium was used as a control material and tested under similar conditions. Three test conditions were used—dry sliding, with water, and with simulated body fluid (SBF). The highest coefficient of friction obtained was for chromium boride under dry sliding conditions. Water and SBF acted as lubricants and lowered the coefficient of friction. The friction coefficient for Cr and chromium boride was lowest under SBF conditions. SEM analysis showed that the wear modes were different under different test conditions. TEM analysis showed a layered-like structure of debris that could have acted as a lubricant and caused a very low friction coefficient as the tests progressed.

A Comparative Study Between Dynamic and Static Simulated Body Fluid Methods

In vitro method has often been used in the biodegradation/bioactivity evaluation of bioactive ceramics for its convenience and saving in time and outlay. The simulated body fluid (SBF) suggested by Kokubo was a good simulation of the osteoproduction environment in osseous tissue and has been proved to be a good method to study the bioactivity of biomaterials and the mechanism of bone bonding. But SBF is not a suitable method to research the osteoinduction of biomaterials. The results from SBF were not consistent with that from in vivo in muscle. The local ion concentration is the key factors to affect the nucleation and growth of apatite. In muscle the effect of body fluid flowing on local ion concentration cannot be ignored. A dynamic SBF suggested by these authors of this paper not only simulated the ion concentration of body fluid, but also simulated the effect of body fluid flowing on the local ion concentration near the surface or in biomaterials in muscle. The results from the dynamic SBF were in good agreement with that of the implantation experiments in muscle. The results from dynamic SBF showed that apatite only formed on the walls of macropores of the porous CaP, no apatite formed on the surface of both dense and porous CaP. The new bone only formed on the walls of macropores of porous CaP implanted in muscles, no apatite or osseous tissue could be found on the surfaces of both porous and dense CaP. The dynamic SBF preferably simulated the osteoinduction environment in non-osseous tissue and can be used in osteoinductivity evaluation of bioceramics.

Static and Dynamic Mechanical Behavior of Hydroxyapatite-Polyacrylic Acid Composites Under Simulated Body Fluid

In this work, we have investigated mechanical response of hydroxyapatite/polyacrylic composites under dry, wet and simulated body fluid conditions. Hydroxyapatite (HAP) is mineralized under two conditions; one, in presence of polyacrylic acid (in situ HAP), second, in absence of polyacrylic acid (ex situ HAP). Further, in situ and ex situ HAP are mixed with polyacrylic acid to make HAP/PAAc composites. Interfacial interactions between PAAc and HAP have been studied using photoacoustic Fourier transform infrared spectroscopy (PAS-FTIR). The mechanical response of the composites under wet condition is studied by soaking composite samples in simulated body fluid (SBF). Under wet conditions, SBF and water weaken the HAP-HAP interface significantly. PAS-FTIR data suggests that PAAc attaches to HAP through the dissociated carboxylate groups. The water and SBF soaked samples showed creep-like behavior and exhibit large residual strain after unloading. Loading under different strain rates has significant effect on mechanical properties of these composites. Both in situ and ex situ 70:30 composites exhibit highest elastic modulus at strain rate of 0.01 sec-1. XRD study indicates formation of Ca2P2O7 phase in ex situ composite after soaking in SBF and water for 3 hours, whereas in situ composites showed presence of only hydroxyapatite phase after soaking in SBF and water for same duration of time.

Dynamic study of calcium phosphate formation on porous HA/TCP ceramics

Bone-like apatite formation on porous calcium phosphate ceramics was investigated in static simulated body fluid (SBF) and dynamic SBF at different flowing rates. The results of a 14-day immersion in static SBF showed that the formation of bone-like apatite occurred both on the surface and in the pores of the samples. When SBF flowed at the physiological flow rate in muscle (2 ml/100 ml.min), bone-like apatite could be detected only in internal surface of the pores of samples. The result that bone-like apatite formation could only be found in the pores when SBF flowed at physiological flow rate was consistent with that of porous calcium phosphate ceramics implanted in vivo: osteoinduction was only detected inside the pores of the porous calcium phosphate ceramics. This result implicates that the bone-like apatite may play an important role in the osteoinduction of Ca-P materials. The dynamic model used in this study may be better than usually used static immersion model in imitating the physiological condition of bone-like apatite formation. Dynamic SBF method is very useful to understand bone-like apatite formation in vivo and the mechanism of ectopic bone formation in calcium phosphate ceramics.

Electrochemical and corrosion behavior of Ti– xAl– yFe alloys prepared by direct metal deposition method

The electrochemical and corrosion behavior of Ti-based alloys was investigated. The direct metal deposition technique was used to fabricate 21 alloys with different ratio of metals (0 ≤ Al ≤ 27 wt.%, 0 ≤ Fe ≤ 25 wt.%). Corrosion resistance of each alloy was evaluated both qualitatively and quantitatively by voltammetric measurements in the simulated human body fluid conditions (Hank's solution). The corrosion rates of the materials were compared in Hank's solution using Tafel extrapolation method. Among the Ti– xAl– yFe alloys the Ti–7Al–4Fe alloy exhibited the slowest corrosion rate of 7.7 × 10 −4 mm/year and the least value of passive current density (6.3 × 10 −3 A/m 2). The alloy is resistant to pitting corrosion as well.

Dynamic study of calcium phosphate formation on porous HA/TCP ceramics

Bone-like apatite formation on porous calcium phosphate ceramics was investigated in static simulated body fluid (SBF) and dynamic SBF at different flowing rates. The results of a 14-day immersion in static SBF showed that the formation of bone-like apatite occurred both on the surface and in the pores of the samples. When SBF flow at the physiological flow rate in muscle (2 ml/100 ml min1), bone-like apatite could be detected only in internal surface of the pores of samples. The result that bone-like apatite formation could only be found in the pores when SBF flown at physiological flow rate was consistent with that of porous calcium phosphate ceramics implanted in vivo: osteoinduction was only detected inside the pores of the porous calcium phosphate ceramics. This result implicates that the bone-like apatite may play an important role in the osteoinduction of Ca-P materials. The dynamic model used in this study may be better than usually used static immersion model in imitating the physiological condition of bone-like apatite formation. Dynamic SBF method is very useful to understand bone-like apatite formation in vivo and the mechanism of ectopic bone formation in calcium phosphate ceramics.

Effect of replacement of V by Fe and Nb on passive film behavior of Ti–6Al–4V in simulated body fluid conditions

The effect of replacing V in the alloy Ti–6Al–4V by Fe and Nb on the electrochemical behavior in simulated body fluid conditions has been addressed in the present study. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used to study the passivation behavior of Ti alloys (Ti–6Al–4V, Ti–6Al–4Fe and Ti–6Al–4Nb) as a function of immersion time in Hank's solution. The Fe and Nb containing alloys exhibited higher passive film resistance after immersion in Hank's solution as compared to Ti–6Al–4V alloy. The mechanical behavior of cast Ti–6Al–4Fe and Ti–6Al–4Nb was also evaluated. The cast Ti–6Al–4Nb alloy exhibited improved ductility compared to Ti–6Al–4Fe alloy. The fracture mode in Ti–6Al–4Fe was essentially brittle while Ti–6Al–4Nb exhibited mixed mode failure.

Surface characterization of passive film formed on nitrogen ion implanted Ti–6Al–4V and Ti–6Al–7Nb alloys using SIMS

The aim of this paper is to study the effect of N + ion implantation on corrosion and phase formation on the implanted surfaces of Ti–6Al–4V and Ti–6Al–7Nb alloys. Nitrogen ion was implanted on Ti–6Al–4V and Ti–6Al–7Nb alloys at an energy of 70 and 100 keV, respectively using a 150 keV accelerator at different doses ranging from 5 × 10 15 to 2.5 × 10 17 ions/cm 2. Electrochemical studies have been carried out in Ringer’s solution in order to determine the optimum dose that can give good corrosion resistance in a simulated body fluid condition. The implanted surfaces of such modified doses were electrochemically passivated at 1.0 V for an hour. Secondary ion mass spectroscopy was used to study and characterize titanium oxide and titanium nitride layers produced on implanted surface and to correlate them with the corrosion resistance. The nature of the passive film of the implanted–passivated specimen was compared with the unimplanted–passivated as well as as-implanted specimens.

Characterization of different materials for corrosion resistance under simulated body fluid conditions

A systematic characterization study has been carried out on different materials such as commercial purity titanium, Ti–6Al–4V, 316L stainless steel, and a cobalt-based alloy under simulated body fluid conditions at 37 °C. Breakdown potential, corrosion rates, pitting/crevice corrosion resistance, and the ability to form protective oxide scales were evaluated and compared. The advantages of the titanium alloy over other materials were highlighted. An attempt has also been made to study the suitability of titanium alloy, IMI 834, for biomedical applications. AC impedance measurements were also carried out in order to provide supportive evidence for the above results.