Studies In Simulated Body Fluid Research Articles

Hydroxyapatite coating for control degradation and parametric optimization of pure magnesium: an electrophoretic deposition technique for biodegradable implants

Design of orthopedic implants is a challenging task to cope with desired properties, therefore, numerous metal-alloy and coating were utilized in the fabrication of implants as alternative options. Magnesium (Mg)-based alloys are among the unique materials owing to their promising properties to avoid cytotoxicity, genotoxicity, and carcinogenicity; however, the fast degradation of Mg limits its clinical applications. In this study, hydroxyapatite (HA) nano-powder was coated on pure Mg as the compositions of both materials are promising biodegradable bone-compatible materials. The electrophoretic deposition (EPD) technique was used to produce a bioactive coating on pure Mg. The research novelty highlighted for the first time, the EPD parameters were optimized via the full Design of Experiment (DoF) approach during HA coating of Mg, while the weight loss of pure Mg and HA coated Mg were investigated in SBF for 7, 14, 21, and 28 days. The surface morphologies of both materials were investigated before and after coating. The bioactivity of the coated samples was examined in Simulated Body Fluid (SBF) and investigated using SEM. Surface roughness, contact angle measurement, scratch test, wear test, an in-vitro study in SBF, electrochemical corrosion, and cellular studies were conducted according to the standard approaches. The results show that HA coated Mg samples are compatible for orthopedic implants in terms of surface roughness, wettability, adhesion, wear sustainability, HA growth, corrosion rate, and cell viability. Thus, the biological, mechanical, and cellular properties of HA-coated implants are suitable and recommended as alternatives to biodegradable implants.

Formation of nanostructures on magnesium alloy by anodization for potential biomedical applications

In the present work, we have investigated the formation of nanostructures on AZ31 magnesium alloy using electrochemical anodization technique. The formed nanostructures were efficiently showed bone-like apatite formation followed by its gradual increase, when immersed in simulated body fluid (SBF) and it exhibited controlled degradation in 7 days. Cell viability study was performed using MG-63 cells (human osteosarcoma cell lines) and revealed that the nanostructured surface has excellent biocompatibility by enhancing both cell adhesion and cell growth. The detailed characterization of this anodized surface was evaluated by field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS). Furthermore, surface-corrosion before and after anodization was examined by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies in SBF. The in-depth studies bring out the fact that native oxide in the sample is converted to a biocompatible nanostructure, which is created due to anodization in a particular electrolyte solution containing ethylene glycol and hybrid hydrofluoric acid mixture.

Effect of magnesium content on bioactivity of near invert phosphate‐based glasses

AbstractA series of phosphate glasses 40P2O5‐(40−x)CaO‐xMgO‐(20−y)Na2O‐yTiO2 (where 0 ≤ x ≤ 24 and y = 0 or 1) with varying MgO contents were investigated for their in vitro calcium phosphate (CaP) formation. Thermal analysis of these glass compositions was conducted and a significant decrease in glass transition temperature from 448°C to 430°C was seen with reducing MgO content from 24 to 8 mol%. Degradation studies were performed in phosphate buffered saline (PBS) at 37°C, where the 8 mol% MgO glass showed the highest mass loss of around 3.4% after 28 days of immersion. Cation release studies were conducted via ion chromatography, using ultrapure water at 37°C as the degradation medium. The highest release of Ca2+ and Na+ ions was observed with the 8 mol% MgO glass. In vitro CaP formation studies were conducted using glass discs immersed in simulated body fluid (SBF) at 37°C for up to 28 days. The amorphous phase and chemical composition of deposited CaP layers on the glass discs were confirmed via X‐ray diffraction (XRD) and energy‐dispersive X‐ray spectroscopy (EDX) analysis, respectively. CaP layers with Ca/P ratio 0.8‐1.1 were found to be deposited on the lower MgO content (8 to 2 mol%) glass surface after 28 days of SBF study.

Bioactivity of quaternary glass prepared from bentonite clay

Alkoxysilane precursors are the most widely used silica source for sol–gel preparation of silicate-based bioactive glass. However, due to their high cost, alternative sources such as bentonite clay are desirable. In the present work, bentonite clay was reacted with sodium hydroxide (NaOH) to extract sodium metasilicate (Na2SiO3). The obtained Na2SiO3 was converted to gel which was then sintered at 950 ℃ for 3 h to give the bioactive glass in the quaternary composition SiO2–NaO–CaO–P2O5. The resulting glass was incubated in simulated body fluid (SBF) for 0–7 days to evaluate the bioactivity. Furthermore, glass samples were characterized before and after SBF study by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Results obtained showed the presence of Na2Ca2Si3O9 (combeite) crystal as the major crystalline phase and the formation of hydroxyapatite (HA) and hydroxycarbonated apatite (HCA) on the surface of the glass after immersion in SBF. The material showed potentials for application as scaffold in bone tissue repair.

The effect of alendronate on biomineralization at the bone/implant interface.

A recent approach to improve the osseointegration of implants is to utilize local drug administration. The presence of an osteoporosis drug may influence both bone quantity and quality at the bone/implant interface. Despite this, the performance of bone-anchoring implants is traditionally evaluated only by quantitative measurements. In the present study, the osteoporosis drug alendronate (ALN) was administrated from mesoporous titania thin films that were coated onto titanium implants. The effect that the drug had on biomineralization was explored both in vitro using simulated body fluid (SBF) and in vivo in a rat tibia model. The SBF study showed that the apatite formation was completely hindered at a high concentration of ALN (0.1 mg/mL). However, when ALN was administrated from the mesoporous coating the surface became completely covered with apatite. Ex vivo characterization of the bone/implant interface using Raman spectroscopy demonstrated that the presence of ALN enhanced the bone mineralization, and that the chemical signature of newly formed bone in the presence of ALN had a higher resemblance to the pre-existing mature bone than to the bone formed without drug. Taken together, this study demonstrates the importance of evaluating the quality of the formed bone to better understand the performance of implants. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A 104A: 620-629, 2016.

The Controllable Growth of Stereo Reticular Hydroxyapatite Structure on Femtosecond Lasers Micro-Patterned Titanium Surface

The controllable deposition of hydroxyapatite (HA) on femtosecond lasers micro-patterned Titanium (Ti) plates was studied in simulated body fluid (SBF). Energy Dispersive Spectrometer analysis and X-ray Diffraction (XRD) analysis show that the hydroxyapatite deposites on the pattened titanium surface in 1.5 SBF and SEM studies show three growth modes of HA (homogeneous hydroxyapatite layer, needle-like structure, and plate-like structure) deposited at different spots of the Ti plate surface. This stereo reticular structure of hydroxyapatite could be regarded as promising candidate material for metal implantation.

Cobalt-Releasing 1393 Bioactive Glass-Derived Scaffolds for Bone Tissue Engineering Applications

Loading biomaterials with angiogenic therapeutics has emerged as a promising approach for developing superior biomaterials for engineering bone constructs. In this context, cobalt-releasing materials are of interest as Co is a known angiogenic agent. In this study, we report on cobalt-releasing three-dimensional (3D) scaffolds based on a silicate bioactive glass. Novel melt-derived "1393" glass (53 wt % SiO2, 6 wt % Na2O, 12 wt % K2O, 5 wt % MgO, 20 wt % CaO, and 4 wt % P2O5) with CoO substituted for CaO was fabricated and was used to produce a 3D porous scaffold by the foam replica technique. Glass structural and thermal properties as well as scaffold macrostructure, compressive strength, acellular bioactivity, and Co release in simulated body fluid (SBF) were investigated. In particular, detailed insights into the physicochemical reactions occurring at the scaffold-fluid interface were derived from advanced micro-particle-induced X-ray emission/Rutherford backscattering spectrometry analysis. CoO is shown to act in a concentration-dependent manner as both a network former and a network modifier. At a concentration of 5 wt % CoO, the glass transition point (Tg) of the glass was reduced because of the replacement of stronger Si-O bonds with Co-O bonds in the glass network. Compressive strengths of >2 MPa were measured for Co-containing 1393-derived scaffolds, which are comparable to values of human spongy bone. SBF studies showed that all glass scaffolds form a calcium phosphate (CaP) layer, and for 1393-1Co and 1393-5Co, CaP layers with incorporated traces of Co were observed. The highest Co concentrations of ∼12 ppm were released in SBF after reaction for 21 days, which are known to be within therapeutic ranges reported for Co(2+) ions.

Screening of in vitro cytotoxicity, antioxidant potential and bioactivity of nano- and micro-ZrO2 and -TiO2 particles

Nanometal oxides are used in tissue engineering and implants. The increased use of nanoparticles suggests the need to study their adverse effects on biological systems. The present investigation explores in vitro cytotoxicity, antioxidant potential, and bioactivity of nano- and micro-particles such as zirconia (ZrO2) and titania (TiO2) on biological systems such as National Institute of Health (NIH) 3T3 mouse embryonic fibroblasts cell line, di(phenyl)-(2,4,6-trinitrophenyl) iminoazanium (DPPH) and simulated body fluid (SBF). The cell line viability % indicated that nano ZrO2 and TiO2 were less toxic than microparticles up to 200µgml−1. DPPH assay revealed that the free radical scavenging potential of tested particles were higher for nano ZrO2 (76.9%) and nano TiO2 (73.3%) at 100mg than that for micron size particles. Calcium deposition percentage of micro- and nano-ZrO2 particles, after SBF study, showed 0.066% and 0.094% respectively, whereas for micro- and nano-TiO2, it was 0.251% and 0.615% respectively. FTIR results showed a good bioactivity through hydroxyapatite formation. The present investigation clearly shows that nanoparticles possess good antioxidant potential and better biocompatibility under in vitro conditions which are dose and size dependent. Hence, cytotoxicity itself is not promising evaluation method for toxicity rather than particles individual characterisation using antioxidant and bioactivity analysis.

Cell culture medium as an alternative to conventional simulated body fluid

Simulated body fluid (SBF) has been widely used for bioactivity assessment of biomaterials. Many different recipes have been developed, but there is still room for improvement. We have suggested the use of cell culture medium to overcome the drawbacks of conventional SBF. Compared with conventional SBF, cell culture medium is easy to prepare. The normal practices in cell culturing, such as filtering, can eliminate insoluble precipitates in the medium and incubation at 37 °C in an atmosphere with 5% CO 2 also better simulates the in vivo environment. After 4 days immersion in carbonate buffered Dulbecco’s modified Eagle’s medium (DMEM), precipitates were found to have formed on the surfaces of hydroxyapatite (HA), α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP). In order to further verify the use of cell culture medium for SBF studies, we carried out computational thermodynamic and kinetic analyses of the precipitation reaction to reveal the effect of pH and ion concentrations on the driving force and nucleation rate of precipitation of different calcium phosphates (CaP). In general, a slight increase in pH of the cell culture medium from physiological pH (pH 7.4) would favor CaP precipitation thermodynamically and increase the rate, as in the case of r-SBF reported previously. [Ca] and [P] have more impact on precipitation compared with other ions, but the effect is consistent among different materials, indicating that other cell culture media with slightly different compositions may also be used. This study also shows that matching the buffer with the environment is required and fetal bovine serum (FBS) slows down surface CaP precipitation on HA.

Nucleation and growth of calcium phosphates in the presence of fibrinogen on titanium implants with four potentially bioactive surface preparations. An in vitro study

The aim of this study was to compare the nucleating and crystal growth behaviour of calcium phosphates on four types of potentially bioactive surfaces, using the simulated body fluid (SBF) model with added fibrinogen. Blasted titanium discs were modified by alkali and heat treatment, anodic oxidation, fluoride treatment, or hydroxyapatite coating. The discs were immersed in SBF with fibrinogen for periods of 3 days and 1, 2, 3 and 4 weeks. The topography, morphology, and chemistry of the surfaces were evaluated with optical interferometry, scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX), and x-ray photoelectron spectroscopy (XPS), respectively. All surface modifications showed early calcium phosphate formation after 3 days, and were almost completely covered by calcium phosphates after 2 weeks. After 4 weeks, the Ca/P ratio was approximately 2.0 for all surface groups except the fluoride modified surface, which had a Ca/P ratio of 1.0-1.5. XPS measurements of the nitrogen concentration, which can be interpreted as an indirect measure of the protein content, reached a peak value after 3 days immersion and decreased thereafter. In conclusion, the results in the present study, when compared to earlier SBF studies without proteins, showed that fibrinogen stimulates calcium phosphates formation. Furthermore, no pronounced differences could be detected between blasted controls and the potentially bioactive specimens.

Electrosprayed Nanoapatite: A New Generation of Bioactive Material

Fine nanoapatite relics were deposited on glass substrates by electrohydrodynamic atomisation, using nanohydroxyapatite (nHA), nano-carbonated hydroxyapatite (nCHA) and nanosilicon- substituted hydroxyapatite (nSiHA) suspensions. These electrosprayed nanoapatites were evaluated in-vitro using simulated body fluid (SBF) and human osteoblast (HOB) cells. The SBF study revealed that newly-formed apatite layers were observed on the surface of the relics. Furthermore, enhanced HOB cell growth was observed on each of the nanoapatites at all time points. Hence, this work demonstrated that electrosprayed nanoapatites offer considerable potential as biomaterials.