Exposure In Simulated Body Fluid Research Articles

Processing of Polyester-Urethane Filament and Characterization of FFF 3D Printed Elastic Porous Structures with Potential in Cancellous Bone Tissue Engineering.

This paper addresses the potential of self-made polyester-urethane filament as a candidate for Fused Filament Fabrication (FFF)-based 3D printing (3DP) in medical applications. Since the industry does not provide many ready-made solutions of medical-grade polyurethane filaments, we undertook research aimed at presenting the process of thermoplastic polyurethane (TPU) filament formation, detailed characteristics, and 3DP of specially designed elastic porous structures as candidates in cancellous tissue engineering. Additionally, we examined whether 3D printing affects the structure and thermal stability of the filament. According to the obtained results, the processing parameters leading to the formation of high-quality TPU filament (TPU_F) were captured. The results showed that TPU_F remains stable under the FFF 3DP conditions. The series of in vitro studies involving long- and short-term degradation (0.1 M phosphate-buffered saline (PBS); 5 M sodium hydroxide (NaOH)), cytotoxicity (ISO 10993:5) and bioactivity (simulated body fluid (SBF) incubation), showed that TPU printouts possessing degradability of long-term degradable tissue constructs, are biocompatible and susceptible to mineralization in terms of hydroxyapatite (HAp) formation during SBF exposure. The formation of HAp on the surface of the specially designed porous tissue structures (PTS) was confirmed by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) studies. The compression test of PTS showed that the samples were strengthened due to SBF exposure and deposited HAp on their surface. Moreover, the determined values of the tensile strength (~30 MPa), Young’s modulus (~0.2 GPa), and compression strength (~1.1 MPa) allowed pre-consideration of TPU_F for FFF 3DP of cancellous bone tissue structures.

The influence of titanate coupling agent on the performance of barium titanate/PMMA denture base nanocomposites after SBF storage

Poly(methyl methacrylate) (PMMA)/nanobarium titanate (NBT) composite has potential application in denture base materials. The denture base materials should be stable in the wet environment and exhibit good mechanical properties. This study aimed to evaluate the effectiveness of titanate coupling agent (TCA) on NBT behavior after soaking in the simulated body fluid (SBF) and to determine the effect of SBF exposure on fracture toughness of the PMMA nanocomposites. Silanated (Si-NBT), titanated (Ti-NBT), and pure NBT (Un-NBT) at 5% concentration (by mass) were incorporated in the PMMA matrix. NBT was sonicated in MMA prior to mixing with PMMA. SBF absorption, solubility, and leaching were measured, and fracture toughness of the PMMA nanocomposites was evaluated after soaking. The results showed that Titanated samples displayed lower SBF absorption capability and solubility values than the silanated ones. Moreover, the leachability of filler elements (Ba and Ti) was substantially reduced by titanation (54% and 61%, respectively), whereas the Si-NBT/PMMA revealed values of 12.3% and 7% respectively. Significant differences in fracture toughness were observed among the tested samples after 6 weeks of aging in SBF ( p < 0.05). Although no notable changes in the KIC of pure PMMA and Un-NBT/PMMA samples were detected, KIC was improved by 20% after titanation. In addition, the fracture toughness of the titanated samples was higher than that of the silanated ones by 26%. In conclusion, TCA exhibited better stability in moisture than silane. Degradation resistance to moisture obtained with titanated NBT could lead to the promotion of clinical longevity of the composites.

Ag(Pt) nanoparticles-decorated bioactive yet antibacterial Ca- and P-doped TiO2 coatings produced by plasma electrolytic oxidation and ion implantation

Plasma electrolytic oxidation (PEO) of Ti alloys was carried out in three different electrolytes based on Ca and P compounds. For the first time, the PEO TiO2-based coatings were subjected to ion implantation with Ag and Pt ions to form Ag(Pt) nanoparticles (NPs) on their surface. The PEO coatings released a high amount of Ca and P ions resulting in fast mineralization during their exposure in simulated body fluid. The TiO2, Ag/TiO2, and Pt/TiO2 samples generated reactive oxygen species (ROS) after being exposed to various irradiation conditions (UV, visible light, and storage in the dark). The Ag-doped TiO2 coating exhibited a strong bactericidal effect against E. coli U20 (antibiotic-sensitive), E. coli K261 (antibiotic-resistant), S. aureus 839, and S. aureus 224/228 (methicillin-resistant) strains and inhibited the early stage of their biofilm formation. The Pt/TiO2 sample was effective toward E. coli U20 and antiadhesive for S. aureus 224/228 strains. The surface of TiO2-based coatings was adhesive for osteoblastic cells and able to maintain a high level of MC3T3-E1 cell proliferation. Cytocompatibility of the TiO2, Ag/TiO2, and Pt/TiO2 coatings was also confirmed by MTT assay. Good in vitro mineralization ability and high antibacterial efficiency of the Ag/TiO2 coatings were achieved with only short-term reduction in the osteoblastic cell proliferation and ALP activity.

Surface properties of calcium aluminate cement blends for bone repair applications

Surface composition and its roughness affect the interactions that induce bone tissue growth in a biomaterial. Irregular surfaces result in better bone fixation than smoother ones, indicating that this feature might have a direct influence on osteoblast adhesion. In this paper, some surface properties of calcium aluminate cement (CAC)-based blends were evaluated, compared to commercial products as mineral trioxide aggregate (MTA) and polimetylmethacrylate (PMMA) as a reference. Roughness was measured by profilometry using samples without or with SBF (simulated body fluid) treatment for 21 days. The collagen samples, MTA and PMMA, presented higher roughness values before SBF treatment. After SBF exposure, all samples except those with PMMA showed an increase in roughness, especially the MTA ones. Cell adhesion was observed by SEM after contact with mesenchymal cell cultures. The latter adhered to the sample's surface pointing out their biocompatibility. Finally, the interactions of samples with culture medium (Dulbecco's Modified Eagle Medium = DMEM) were measured for periods of 1, 3, 7, 14, and 21 days. The sample surfaces were evaluated by SEM, EDX, FTIR and XRD. After the contact of samples with culture medium, the calcium concentration was measured by atomic absorption spectroscopy. All CAC-based blends and mainly MTA presented precipitation after treatment with DMEM, which was characterized as calcium phosphate and mainly calcium carbonate.

Facile Preparative Access to Bioactive Silicon Oxycarbides with Tunable Porosity.

In the present work, Ca-containing silicon oxycarbides (SiCaOC) with varying Ca content have been synthesized via sol-gel processing and thermal treatment in inert gas atmosphere (pyrolysis). It has been shown that the as-prepared SiCaOC materials with low Ca loadings (Ca/Si molar ratios = 0.05 or 0.12) were X-ray amorphous; their glassy network contains Q3 sites, indicating the presence of Ca2+ at non-bridging-oxygen sites. SiCaOC with high Ca content (i.e., Ca/Si molar ratio = 0.50) exhibits the presence of crystalline calcium silicate (mainly pseudowollastonite). Furthermore, it has been shown that the incorporation of Ca into the SiOC glassy network has a significant effect on its porosity and specific surface area. Thus, the as-prepared Ca-free SiOC material is shown to be non-porous and having a specific surface area (SSA) of 22.5 m2/g; whereas SiCaOC with Ca/Si molar ratio of 0.05 exhibits mesoporosity and a SSA value of 123.4 m2/g. The further increase of Ca content leads to a decrease of the SSA and the generation of macroporosity in SiCaOC; thus, SiCaOC with Ca/Si molar ratio of 0.12 is macroporous and exhibits a SSA value of 39.5 m2/g. Bioactivity assessment in simulated body fluid (SBF) confirms the hydroxyapatite formation on all SiCaOC samples after seven days soaking, unlike the relatively inert ternary silicon oxycarbide reference. In particular, SiCaOC with a Ca/Si molar ratio of 0.05 shows an increased apatite forming ability compared to that of SiCaOC with Ca/Si molar ratio of 0.12; this difference is considered to be a direct consequence of the significantly higher SSA of the sample with the Ca/Si ratio of 0.05. The present work indicates two effects of Ca incorporation into the silicon oxycarbide glassy network on its bioactivity: Firstly, Ca2+ is shown to contribute to the slight depolymerization of the network, which clearly triggers the hydroxyapatite formation (compare the bioactive behavior of SiOC to that of SiCaOC with Ca/Si molar ratio 0.12 upon SBF exposure); secondly, the Ca2+ incorporation seems to strongly affect the porosity and SSA in the prepared SiCaOC materials. There is an optimum of Ca loading into the silicon oxycarbide glassy network (at a Ca/Si molar ration of 0.05), which provides mesoporosity and reaches maximum SSA, both highly beneficial for the bioactive behavior of the materials. An increase of the Ca loading leads, in addition to the crystallization of calcium silicates, to a coarsening of the pores (i.e., macroporosity) and a significant decrease of the SSA, both negatively affecting the bioactivity.

Durability of AZ31 magnesium biodegradable alloys polydopamine aided. Part 2: Ageing in Hank's solution

Abstract Magnesium alloys are candidates as biodegradable medical materials due to their biocompatibility and favorable mechanical properties. Unfortunately, the high corrosion rate in physiological media and the release of hydrogen, limit their widespread use in biomedical applications. In this work, an intermediate coating based on polydopamine (PDOPA), between Mg substrate and an organic coating, was used to decreasing the degradation rate of AZ31 magnesium alloy, during the long-term exposure in simulated body fluid. Electrochemical Impedance Spectroscopy measurements were carried out to study the corrosion resistance of samples. Results demonstrated that the PDOPA interlayer determined the reduction of the substrate degradation rate. The results were interpreted supposing a synergistic effect which occurred when PDOPA and the organic coating were used together.

In-vitro corrosion of AZ31 magnesium alloys by using a polydopamine coating

Magnesium alloys are candidates to be used as biodegradable biomaterials for producing medical device. Their use is restricted due to the high degradation rate in physiological media. To contribute to solving this problem, a polydopamine (PDOPA) layer could be used to increase adhesion between the metallic substrate and external organic coating. In this paper, the corrosion behaviour of samples was investigated to determine their performance during the long-term exposure in simulated body fluid. Electrochemical methods including Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) were used to investigate the corrosion resistance of samples. The results demonstrated a decreasing of the substrate degradation rate when PDOPA was used as interlayer supposing a synergistic effect when it was used together with the organic coating.

Electrochemical Corrosion and In vitro Biocompatibility Performance of AZ31Mg/Al2O3 Nanocomposite in Simulated Body Fluid

In this present investigation, AZ31 alloy nanocomposite was prepared with the inclusion of Al2O3 nanoparticles using innovative disintegrated melt deposition (DMD) process followed by hot extrusion to improve the corrosion resistance and in vitro biocompatibility in simulated body fluid (SBF). This investigation systematically inspected the degradation performances of AZ31 alloy with Al2O3 nanoparticles through hydrogen evolution, weight loss and electrochemical methods in SBF. Further, the surface microstructure with the in vitro mineralization of the alloys in SBF was characterized by XRD, XPS, and SEM/EDS analysis. It was seen that the addition of Al2O3 nanoparticles significantly decreased the weight loss of AZ31 alloy substrates after 336 h of exposure in SBF. The corrosion resistance of the monolithic and nanocomposite samples was evaluated using potentiodynamic polarization tests, electrochemical impedance spectroscopy measurements in short- and long-term periods. Accordingly, the electrochemical analysis in SBF showed that the corrosion resistance performance of the AZ31 alloy enhanced considerably due to the incorporation of Al2O3 nanoparticles as reinforcement. Moreover, the rapid formation of bone-like apatite layer on the surface of the nanocomposite substrate demonstrated a good bioactivity of the nanocomposite samples in SBF.

Effect of The Heat Treatment on The Bioactivity of Nanostructured Surfaces

Titanium and its alloys are widely used materials in implantology due to their high corrosion resistance and biocompatibility. The bioactivity and the osseointegration of these surfaces could be enhanced by several processes. One of them is the formation of nanostructure by the combination of electrochemical and chemical reactions. The nanotubular oxidic structure has positive influence on the precipitation of hydroxyapatite from the body environment and on the cell proliferation. Directly created layer has amorphous character, but it is possible to transform it to crystalline form by heat treatment. This could have another positive influence on bioactivity. The influence of surfaces nanostructuring of commercially pure titanium and experimental beta alloy Ti-39Nb and their subsequent heat treatment on bioactivity will be presented in this work. This has been evaluated by Ca-P based compounds precipitation on the surface during the in vitro exposure in simulated body fluid. It was found that heat treatment has considerable influence on surface bioactivity.

Impedance technique for monitoring of apatite precipitation from simulated body fluid

In vitro testing of bioactivity of metallic materials is frequently executed in simulated body fluid. Measurements are usually used as yes/no test. Samples are removed after some time of exposure from the environment and the level of bone-like apatite precipitation is evaluated. The goal of the presented study was to determine the ability of electrochemical techniques to detect changes on the phase boundary with sufficient sensitivity. The behaviour of Ti-35Nb-2Zr-0.2O alloy with modified surfaces was studied in this work. Nanotubes with three different diameters were prepared by anodic oxidation. Modified surfaces were described in the terms of morphology and chemical composition. Specimens were exposed to simulated body fluid and apatite precipitation was monitored. The electrochemical impedance spectroscopy was used for the nanotubes – electrolyte phase boundary changes description. Measurement at constant frequency was used for determination of the apatite precipitation. The surface analysis indicated enrichment of the nanotubular layer by niobium. The exposure in simulated body fluid resulted in apatite layer creation on the nanotubes with the largest diameter only. The changes on phase boundary were clearly detected by electrochemical impedance spectroscopy in a broad range of frequencies, constant frequency impedance measurement allowed for the determination of incubation period.

Effect of Alumina Incorporation on the Surface Mineralization and Degradation of a Bioactive Glass (CaO-MgO-SiO₂-Na₂O-P₂O₅-CaF₂)-Glycerol Paste.

This study investigates the dissolution behavior as well as the surface biomineralization in simulated body fluid (SBF) of a paste composed of glycerol (gly) and a bioactive glass in the system CaO-MgO-SiO2-Na2O-P2O5-CaF2 (BG). The synthesis of the bioactive glass in an alumina crucible has been shown to significantly affect its bioactivity due to the incorporation of aluminum (ca. 1.3–1.4 wt %) into the glass network. Thus, the kinetics of the hydroxyapatite (HA) mineralization on the glass prepared in the alumina crucible was found to be slower than that reported for the same glass composition prepared in a Pt crucible. It is considered that the synthesis conditions lead to the incorporation of small amount of aluminum into the BG network and thus delay the HA mineralization. Interestingly, the BG-gly paste was shown to have significantly higher bioactivity than that of the as-prepared BG. Structural analysis of the paste indicate that glycerol chemically interacts with the glass surface and strongly alter the glass network architecture, thus generating a more depolymerized network, as well as an increased amount of silanol groups at the surface of the glass. In particular, BG-gly paste features early intermediate calcite precipitation during immersion in SBF, followed by hydroxyapatite formation after ca. seven days of SBF exposure; whereas the HA mineralization seems to be suppressed in BG, probably a consequence of the incorporation of aluminum into the glass network. The results obtained within the present study reveal the positive effect of using pastes based on bioactive glasses and organic carriers (here alcohols) which may be of interest not only due to their advantageous visco-elastic properties, but also due to the possibility of enhancing the glass bioactivity upon surface interactions with the organic carrier.

In vitro bioactivity study of TiCaPCO(N) and Ag-doped TiCaPCO(N) films in simulated body fluid.

Bioactivity of multicomponent TiCaPCO(N) and Ag-doped TiCaPCO(N) films was evaluated in vitro using simulated body fluid (SBF) and compared with that of bioactive glass Biogran. The first group of films was fabricated by magnetron sputtering of composite TiС0.5 -Ti3 POx -CaO target produced via the self-propagating high-temperature synthesis (SHS) method (TiCaPCON films), after which their surface was implanted with Ag+ ions to obtain Ag-doped TiCaPCON films. The second group of films was fabricated by pulsed electrospark deposition (PED) using SHS-produced composite TiС0.5 -Ti3 POx -CaO and TiС0.5 -Ti3 POx -CaO-Ag electrodes. After immersion in SBF, the structure and chemistry of surface were well characterized using a combination of various microanalytical techniques, such as scanning electron microscopy, X-ray diffractometry (both in conventional and grazing incidence mode), Fourier transform infrared spectroscopy, Raman spectroscopy, and glow discharge optical emission spectroscopy. The results showed that the surfaces of the TiCaPCO(N) and Ag-doped TiCaPCO(N) films were bioactive in vitro and induced the formation of an apatite layer during exposure in SBF. In the case of the magnetron-sputtered films, the apatite layer was formed over 14days, while 28days were needed to form CaP phase on the surface of PED-modified samples. Various factors (film structure, surface roughness, surface functional groups, surface charge, and composition, supersaturation, and near-surface local supersaturation of SBF) affecting the kinetics of bone-like apatite formation on a bioactive surface are discussed. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 193-203, 2017.

The increase of apatite layer formation by the poly(3-hydroxybutyrate) surface modification of hydroxyapatite and β-tricalcium phosphate

The aim of this study was the surface modification of hydroxyapatite and β-tricalcium phosphate by poly(3-hydroxybutyrate) grafting and characterization of modificates. The bioactivity examination was carried out by the determination to grow an apatite layer on modified materials during incubation in simulated body fluid at 37°C. The additional issue taken up in this paper was to investigate the influence of fluid replacement.The process of the surface modification of biomaterials was evaluated by means of infrared and Raman spectroscopy. Formation of the apatite layer was assessed by means of scanning electron microscopy and confirmed by energy dispersive, Raman and Fourier transformed infrared spectroscopy. During exposure in simulated body fluid, the variation of the zeta potential, pH measurement and relative weight was monitored.Examination of scanning electron microscopy micrographs suggests that modification of hydroxyapatite and β-tricalcium phosphate by poly(3-hydroxybutyrate) significantly increases apatite layer formation. Raman spectroscopy evaluation revealed that the formation of the apatite layer was more significant in the case of hydroxyapatite modificate, when compared to the β-tricalcium phosphate modificate. Both modificates were characterized by stable pH, close to the natural pH of human body fluids. Furthermore, we have shown that a weekly changed, simulated body fluid solution increases apatite layer formation.

Hybrid coating on a magnesium alloy for minimizing the localized degradation for load-bearing biodegradable mini-implant applications

The effect of a hybrid coating, calcium phosphate (CaP) + polylactic acid (PLA), on a magnesium alloy on its in vitro degradation (general and localized) behaviour was studied for potential load-bearing biodegradable mini-implant applications. CaP was coated on a magnesium alloy, AZ91, using an electrochemical deposition method. A spin coating method was used to coat PLA on the CaP coated alloy. In vitro degradation performance of the alloy with hybrid coating was evaluated using electrochemical impedance spectroscopy (EIS) in simulated body fluid (SBF). The EIS results showed that the hybrid coating enhanced the degradation resistance of the alloy by more than two-order of magnitude as compared to the bare alloy and one-order of magnitude higher than that of the CaP coated alloy, after 1 h exposure in simulated body fluid (SBF). Long-term (48 h) EIS results also confirmed that the hybrid coating performed better than the bare alloy and the CaP coated alloy. Importantly, the hybrid coating improved the localized degradation resistance of the alloy significantly, which is critical for better in service mechanical integrity.

Effect of plasma electrolytic oxidation in the solutions containing Ca, P, Si, Na on the properties of titanium

The surface layers were formed on titanium by plasma electrolytic oxidation (PEO) in the solutions which contain various amounts of Na(2)SiO(3)x5H(2)O, Na(3)PO(4) x12H(2)O and Ca(CH(3)COO)(2) xH(2)O. The layers were characterized using a scanning electron microscope (SEM) coupled with an energy dispersive spectrometer (EDS) and an X-ray diffractometer (XRD). The titanium/oxide surface layer interface was analyzed by X-ray photoelectron spectroscopy (XPS). The adhesive strength of the oxide layers was evaluated by the scratch-test. The bioactivity of the surface was determined by soaking in a simulated body fluid (SBF) for 7 and 30 days. The corrosion resistance was determined by electrochemical methods after 13, 181, and 733 h exposure in SBF at a temperature of 37°C. The oxide layers obtained were rough and porous and enriched with Ca, P, Si, and Na and their properties depended on the concentration of the components of the electrolyte. The results of the electrochemical examinations, after a 13 h exposure in SBF, show that the surface modification by PEO improves the corrosion resistance of titanium and it is not degraded after a long-term exposure in SBF. The electrochemical impedance spectroscopy (EIS) results indicate that the surface layers have a complex structure.

Polylactic acid coating on a biodegradable magnesium alloy: An in vitro degradation study by electrochemical impedance spectroscopy

Polylactic acid (PLA) was coated on a biodegradable magnesium alloy, AZ91, using spin coating technique for temporary implant applications. The degradation behaviour of the coated alloy samples was evaluated using electrochemical impedance spectroscopy (EIS) method in simulated body fluid (SBF). EIS results suggested that the PLA coating enhanced the degradation resistance of the alloy significantly. Increase in the PLA coating thickness was found to increase the degradation resistance, but resulted in poor adhesion. Long-term EIS experiments of the PLA coated samples suggested that their degradation resistance gradually decreased with increase in SBF exposure time. However, the degradation resistance of the PLA coated samples was significantly higher than that of the bare metal even after a 48h exposure to SBF.

Neutron diffraction residual strain measurements in nanostructured hydroxyapatite coatings for orthopaedic implants

The failure of an orthopaedic implant can be initiated by residual strain inherent to the hydroxyapatite coating (HAC). Knowledge of the through-thickness residual strain profile in the thermally sprayed hydroxyapatite coating/substrate system is therefore important in the development of a new generation of orthopaedic implants. As the coating microstructure is complex, non-destructive characterization of residual strain, e.g. using neutron diffraction, provides a useful measure of through thickness strain profile without altering the stress field. This first detailed study using a neutron diffraction technique, non-destructively evaluates the through thickness strain measurement in nanostructured hydroxyapatite plasma sprayed coatings on a titanium alloy substrate (as-sprayed, heat treated, and heat treated then soaked in simulated body fluid (SBF)). The influence of crystallographic plane orientation on the residual strain measurement is shown to indicate texturing in the coating. This texturing is expected to influence both the biological and fracture response of HA coatings. Results are discussed in terms of the influence of heat-treatment and SBF on the residual stress profile for these biomedical coatings. The results show that the through thickness residual strain in all three coatings was different for different crystallographic planes but was on average tensile. It is also concluded that the heat-treatment and simulated body fluid exposure had a significant effect on the residual strain profile in the top layers of HAC.

Biomimetic Apatite Mineralization Mechanisms of Mesoporous Bioactive Glasses as Probed by Multinuclear 31P, 29Si, 23Na and 13C Solid-State NMR

An array of magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy experiments is applied to explore the surface reactions of a mesoporous bioactive glass (MBG) of composition Ca0.10Si0.85P0.04O1.90 when subjected to a simulated body fluid (SBF) for variable intervals. Powder X-ray diffraction and 31P NMR techniques are employed to quantitatively monitor the formation of an initially amorphous calcium phosphate surface layer and its subsequent crystallization into hydroxycarbonate apatite (HCA). Prior to the onset of HCA formation, 1H → 29Si cross-polarization (CP) NMR evidence dissolution of calcium ions; a slightly increased connectivity of the speciation of silicate ions is observed at the MBG surface over 1 week of SBF exposure. The incorporation of carbonate and sodium ions into the bioactive orthophosphate surface layer is explored by 1H → 13C CPMAS and 23Na NMR, respectively. We discuss similarities and distinctions in composition−bioactivity relationships established for traditio...

Characterization of the surface layers formed on titanium by plasma electrolytic oxidation

This paper is concerned with the surface modification of titanium by the PEO method (plasma electrolytic oxidation) in the solutions which contain Ca, P, Si and Na. The chemical composition of the thus formed surface layers was examined by XPS and EDS. The morphology of the surface was observed by SEM. The phase composition was determined by X-ray diffraction (XRD). The adhesive strength of the oxide layers was evaluated by the scratch-test. The corrosion resistance was determined in a simulated body fluid (SBF) at a temperature of 37 °C by electrochemical methods for various exposure times. The oxide layers obtained were porous and enriched with Ca, P, Si and Na and their properties depended on the electrolyte solution and the parameters of the oxidation process. The results of the electrochemical examinations show that the surface modification by PEO does not worsen the corrosion resistance of titanium after a 13 h exposure in SBF. The electrochemical impedance spectroscopy (EIS) results indicate that the surface layers have a complex structure and that their electric properties undergo changes during long-term exposures in SBF.

Effects of poly(lactic‐co‐glycolic acid) (PLGA) degradability on the apatite‐forming capacity of electrospun PLGA/SiO2–CaO nonwoven composite fabrics

We investigated the effects of poly(lactic-co-glycolic acid) (PLGA) degradability on the apatite-forming ability of electrospun PLGA/SiO(2)-CaO gel composite fabric. Two PLGA copolymer compositions with low and high degradability were used in experiments. A nonwoven polymer/ceramic composite fabric composed of randomly mixed microsized biodegradable PLGA fibers and nanosized bioactive SiO(2)-CaO gel fibers was prepared using a simultaneous electrospinning method. A 17 wt.% PLGA solution was prepared using 1,1,3,3-hexafluoro-2-propanol as a solvent, while the SiO(2)-CaO gel solution was prepared via a condensation reaction following hydrolysis of tetraethyl orthosilicate under acidic conditions. PLGA and SiO(2)-CaO gel solutions were spun simultaneously with two separate nozzles under electric fields of 1 and 2 kV/cm using two syringe pumps with flow rates of 7.5 and 5 mL/h, respectively. As controls, low and high degradable PLGA and SiO(2)-CaO gel nonwoven fabrics were also made by the same methods. The five nonwoven fabrics that were produced were exposed to simulated body fluid (SBF) for 1 week. SBF exposure resulted in the deposition of a layer of apatite crystals on the surfaces of both the SiO(2)-CaO gel and the low degradable PLGA/SiO(2)-CaO gel composite fabrics, but not on the low and high degradable PLGA or the high degradable PLGA/SiO(2)-CaO gel composite fabrics. The results are explained in terms of the acidity of the PLGA degradation products, which could have a direct influence on apatite dissolution.