Degradation In Simulated Body Fluid Research Articles

Spray-dried ternary bioactive glass microspheres: Direct and indirect structural effects of copper-doping on acellular degradation behavior

Silicate-based bioactive glass nano/microspheres hold significant promise for bone substitution by facilitating osteointegration through the release of biologically active ions and the formation of a biomimetic apatite layer. Cu-doping enhances properties such as pro-angiogenic and antibacterial behavior. While sol-gel methods usually yield homogeneous spherical particles for pure silica or binary glasses, synthesizing poorly aggregated Cu-doped ternary glass nano/microparticles without a secondary CuO crystalline phase remains challenging. This article introduces an alternative method for fabricating Cu-doped ternary microparticles using sol-gel chemistry combined with spray-drying. The resulting microspheres exhibit well-defined, poorly aggregated particles with spherical shapes and diameters of a few microns. Copper primarily integrates into the microspheres as Cu0 nanoparticles and as Cu2+ within the amorphous network. This doping affects silica network connectivity, as calcium and phosphorus are preferentially distributed in the glass network (respectively as network modifiers and formers) or involved in amorphous calcium phosphate nano-domains depending on the doping rate. These differences affect the interaction with simulated body fluid. Network depolymerization, ion release (SiO44−, Ca2+, PO43−, Cu2+), and apatite nanocrystal layer formation are impacted, as well as copper release. The latter is mainly provided by the copper involved in the silica network and not from metal nanoparticles, most of which remain in the microspheres after interaction. This understanding holds promising implications for potential therapeutic applications, offering possibilities for both short-term and long-term delivery of a tunable copper dose. Statement of significanceA novel methodology, scalable to industrial levels, enables the synthesis of copper-doped ternary bioactive glass microparticles by combining spray-drying and sol-gel chemistry. It provides precise control over the copper percentage in microspheres. This study explores the influence of synthesis conditions on the copper environment, notably Cu0 and Cu2+ ratios, characterized by EPR spectroscopy, an aspect poorly described for copper-doped bioactive glass. Additionally, copper indirectly affects silica network connectivity and calcium/phosphorus distribution, as revealed by SSNMR. Multiscale characterization illustrates how these features impact acellular degradation in simulated body fluid, highlighting the therapeutic potential for customizable copper dosing to address short- and long-term needs.

Comprehensive study of antimicrobial polycaprolactone/clay nanocomposite films: Preparation, characterization, properties and degradation in simulated body fluid

AbstractEven though the biodegradability of polycaprolactone (PCL) and its nanocomposites is lower compared to other biodegradable polyesters, this property and good biocompatibility are used for development of materials for drug delivery with a long‐term effect. We prepared novel PCL/clay nanocomposite films with antimicrobials chlorhexidine (CH) or octenidine (OCT) combined with ZnO anchored on vermiculite (VER). The intercalation of CH and OCT into the interlayer of VER/ZnOVER was confirmed by XRD, FTIR and SEM. The organically modified nanofillers compared to VER (−46.0 mV) or ZnOVER (−34.9 mV) showed a positive ζ‐potential (+30.7 mV (VER_CH), +21.9 mV (VER_OCT), +24.6 mV (ZnOVER_CH)) indicating a relatively stable materials, except ZnOVER_OCT (+8.6 mV), which strongly agglomerated.Thin PCL/clay films were prepared by solvent casting method and the effect of used nanofillers on structural, thermal, mechanical and antimicrobial properties followed by degradation under hydrolytic conditions was studied. The results showed that presence of ZnO significantly decreases thermal and mechanical stability. The nanofillers with the higher hydrophilic character are responsible for the fastest degradation of PCL matrix. Films possessed high antimicrobial efficiency in long time intervals, hence these nanocomposites open new avenues for the possible application of such materials for the drug delivery with a long‐term effect.Highlights Antimicrobial active PCL/clay nanocomposites were prepared. Nanofillers influenced the structure and properties of prepared thin PCL films. ZnO caused lower thermal stability and worse mechanical properties of PCL films. PCL/clay nanocomposite films degraded slowly by a hydrolytic mechanism. High potential as medical materials with long‐lasting antimicrobial efficacy.

A Porous Fluoride-Substituted Bovine-Derived Hydroxyapatite Scaffold Constructed for Applications in Bone Tissue Regeneration.

Hydroxyapatite is widely used in bone implantation because of its similar mineral composition to natural bone, allowing it to serve as a biocompatible osteoconductive support. A bovine-derived hydroxyapatite (BHA) scaffold was developed through an array of defatting and deproteinization procedures. The BHA scaffold was substituted with fluoride ions using a modified sol-gel method to produce a bovine-derived fluorapatite (BFA) scaffold. Fourier-transform infrared spectroscopy and X-ray diffraction analysis showed that fluoride ions were successfully substituted into the BHA lattice. According to energy dispersive X-ray analysis, the main inorganic phases contained calcium and phosphorus with a fluoride ratio of ~1-2 wt%. Scanning electron microscopy presented a natural microporous architecture for the BFA scaffold with pore sizes ranging from ~200-600 μm. The BHA scaffold was chemically stable and showed sustained degradation in simulated-body fluid. Young's modulus and yield strength were superior in the BFA scaffold to BHA. In vitro cell culture studies showed that the BFA was biocompatible, supporting the proliferative growth of Saos-2 osteoblast cells and exhibiting osteoinductive features. This unique technique of producing hydroxyapatite from bovine bone with the intent of producing high performance biomedically targeted materials could be used to improve bone repair.

Hexafluoroisopropanol based silk fibroin coatings on AZ31 biometals with enhanced adhesion, corrosion resistance and biocompatibility

Biomacromolecule coating on biomedical magnesium alloys have generated considerable interest for the improved corrosion resistance and biocompatibility. Silk fibroin (SF) based on aqueous solvent has been demonstrated to be a promising coating for magnesium alloy, but pretreatment process is necessary due to the corrosion susceptibility to water. Herein, the SF coating with hexafluoroisopropanol(HFIP) solvent was prepared without preteatment for simplified processing and enhanced adhesion. Ethylene glycol diglycidyl ether(EGDE) was applied to stabilize the coating with more chemical crosslinking. The morphologies and nano-scratch test verify that the compactness and adhesion strength of HFIP based SF are better than that of aqueous based SF. The electrochemical evaluation and in vitro degradation in simulated body fluid indicated that the HFIP based SF coating exhibited significantly enhanced corrosion resistance. Moreover, the application of EGDE post-treatment significantly improved corrosion resistance (the corrosion current density Icoor of the SF-HFIP-EGDE samples stands at 9.93*10−10A cm−2, representing a reduction by two orders of magnitude in comparison to pure SF samples). Cytoskeleton, cell adhesion and cytotoxicity tests with MC3T3-E1 cells verifies the improved cell adhesion and biological activity of silk coating. This study provides a simple method for physical deposition of biomacromolecule coatings on magnesium alloys, while improving adhesion and corrosion resistance.

Development of isotopically labelled 65Cu embedded PMMA-65CuO nanocomposites for detection and quantification of PMMA bone cement degradation at trace levels

Polymethyl methacrylate (PMMA) bone cement is a popular bone-filling material for biomedical applications. Bone-cement implant failure is a common occurrence, but the consequence of this failure can be prevented/minimised by early detection of degradation. This work utilises a stable isotope labelling approach to monitor PMMA bone cement degradation. Stable isotopically enriched traceable nanoparticles of 65CuO were synthesized and introduced to PMMA bone cement. Accelerated and normal degradation of 65CuO-loaded PMMA bone cement nanocomposite was performed in acetone and simulated body fluid (SBF). 65Cu was detected and quantified upon PMMA bone cement nanocomposite degradation. The results showed a linear correlation between bone cement degradation and tracer release. When the 65CuO-PMMA composite deteriorated by 6.10 ± 3.04% in acetone, 5.6 ± 2.5 µg of tracer was released in 10 min. Similarly, after one week of degradation in SBF, 0.35 ± 0.31 µg of 65Cu tracer was released, translating to a 0.18 ± 0.09% weight loss. The stable isotopic tracer approach allowed us to measure and detect 65Cu under conditions of high background Cu concentration present in the human body upon 0.2% of PMMA nanocomposite degradation. 65CuO nanoparticles addition to PMMA bone cement did not alter the cytocompatibility (proliferation, differentiation, and osteocalcin formation) in MG-63 cells.

Nanoscale Iron-Based Metal–Organic Frameworks: Incorporation of Functionalized Drugs and Degradation in Biological Media

Metal-organic frameworks (MOFs) attract growing interest in biomedical applications. Among thousands of MOF structures, the mesoporous iron(III) carboxylate MIL-100(Fe) (MIL stands for the Materials of Lavoisier Institute) is among the most studied MOF nanocarrier, owing to its high porosity, biodegradability, and lack of toxicity. Nanosized MIL-100(Fe) particles (nanoMOFs) readily coordinate with drugs leading to unprecedented payloads and controlled release. Here, we show how the functional groups of the challenging anticancer drug prednisolone influence their interactions with the nanoMOFs and their release in various media. Molecular modeling enabled predicting the strength of interactions between prednisolone-bearing or not phosphate or sulfate moieties (PP and PS, respectively) and the oxo-trimer of MIL-100(Fe) as well as understanding the pore filling of MIL-100(Fe). Noticeably, PP showed the strongest interactions (drug loading up to 30 wt %, encapsulation efficiency > 98%) and slowed down the nanoMOFs' degradation in simulated body fluid. This drug was shown to bind to the iron Lewis acid sites and was not displaced by other ions in the suspension media. On the contrary, PS was entrapped with lower efficiencies and was easily displaced by phosphates in the release media. Noticeably, the nanoMOFs maintained their size and faceted structures after drug loading and even after degradation in blood or serum after losing almost the totality of the constitutive trimesate ligands. Scanning electron microscopy with high annular dark field (STEM-HAADF) in conjunction with X-Ray energy-dispersive spectrometry (XEDS) was a powerful tool enabling the unraveling of the main elements to gain insights on the MOF structural evolution after drug loading and/or upon degradation.

Effect of Immersion Time in Simulated Body Fluid on Adhesion Strength of Hydrothermally Treated Hydroxyapatite-Titanium Nitride Films on Polyetheretherketones

Abstract This study sought to investigate the effect of immersion time in simulated body fluid (SBF) on the adhesion strength of hydrothermally treated hydroxyapatite-titanium nitride (HA-TiN) films on polyetheretherketone (PEEK) substrates. The HA-TiN films were deposited on PEEK substrates via magnetron sputtering and annealed with hydrothermal treatment. The crystalline phase and element compositions on the deposited films were confirmed by X-ray diffractometry (XRD), and X-ray photoelectron spectrometry (XPS). The samples were then immersed in SBF at 37°C for 7 to 56 days, where the surface characterization and chemical composition of the films were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), and XPS. After the in vitro degradation in SBF, the adhesion strength between HA-TiN films and PEEK substrates were measured by a universal testing machine and further investigated the failure mode using a stereomicroscope and SEM. The results demonstrated the improvement of crystallinity on HA-TiN sputtered films after hydrothermal treatment. After immersion in SBF, the coating surface revealed some nucleation without any detachment and exhibited an increase of surface roughness. The hydroxyapatite and titanium dioxide were revealed on the surface throughout the 56 days, while the Ca/P ratio decreased and remained constant during immersion. The adhesion strength did not significantly differ in all groups. These findings concluded that hydrothermally treated HA-TiN sputtered films on PEEK substrates showed the stability of adhesion strength throughout 56 days in simulated physiological conditions. The dissolution and precipitation during immersion represented the favorable characteristics of the films in the orthopedic or dental application. Keywords: Adhesion, Degradation, Thin films, Hydroxyapatite, Titanium dioxide

Computational modelling of magnesium degradation in simulated body fluid under physiological conditions

Magnesium alloys are highly attractive for the use as temporary implant materials, due to their high biocompatibility and biodegradability. However, the prediction of the degradation rate of the implants is difficult, therefore, a large number of experiments are required. Computational modelling can aid in enabling the predictability, if sufficiently accurate models can be established. This work presents a generalized model of the degradation of pure magnesium in simulated body fluid over the course of 28 days considering uncertainty aspects. The model includes the computation of the metallic material thinning and is calibrated using the mean degradation depth of several experimental datasets simultaneously. Additionally, the formation and precipitation of relevant degradation products on the sample surface is modelled, based on the ionic composition of simulated body fluid. The computed mean degradation depth is in good agreement with the experimental data (NRMSE=0.07). However, the quality of the depth profile curves of the determined elemental weight percentage of the degradation products differs between elements (such as NRMSE=0.40 for phosphorus vs. NRMSE=1.03 for magnesium). This indicates that the implementation of precipitate formation may need further developments. The sensitivity analysis showed that the model parameters are correlated and which is related to the complexity and the high computational costs of the model. Overall, the model provides a correlating fit to the experimental data of pure Mg samples of different geometries degrading in simulated body fluid with reliable error estimation.

3D gel-printing of porous MgFe2O4 magnetic scaffolds for bone tissue engineering

It is increasing evidence that the synergistic effects of magnetic scaffolds and magnetic fields can accelerate bone repairing and regeneration, and the bone tumor may be treated using magnetite nanoparticles (MNPs) with hyperthermia. In this study, in order to apply the magnetocaloric performance of MgFe2O4 to bone tissue engineering, porous MgFe2O4 magnetic scaffolds were successfully prepared by chemical coprecipitation method and 3D gel-printing (3DGP) technology. The printing slurry based on polyvinyl alcohol (PVA) system exhibited shear thinning properties, and its maximum solid loading was about 63 wt%. When the slurry was squeezed out of the needle, the slurry viscosity was 0.58 Pa·s at the shear rate of 316.3 s-1. The scaffolds sintered above 1100 °C were superparamagnetic and their compressive strength was within 1.8–12.51MPa, which is suitable for human cancellous bone. The highest saturation magnetization of porous MgFe2O4 scaffolds printed by 3DGP was 10.63 emu/g when they were sintered at 1200 °C. The weight loss rate of the scaffolds was 2.15% after degradation in simulated body fluid (SBF) for 5 weeks, pH value of SBF was between 6.78 and 7.4. Preliminary biological experiment shows that MC3T3-E1 cells had good adhesion and proliferation on MgFe2O4 scaffolds surface, and MgFe2O4 scaffolds can promote alkaline phosphatase (ALP) activation, which explain that porous MgFe2O4 magnetic scaffolds may be used for bone repairing.

Interfacial Compatibilization into PLA/Mg Composites for Improved In Vitro Bioactivity and Stem Cell Adhesion.

The present work highlights the crucial role of the interfacial compatibilization on the design of polylactic acid (PLA)/Magnesium (Mg) composites for bone regeneration applications. In this regard, an amphiphilic poly(ethylene oxide-b-L,L-lactide) diblock copolymer with predefined composition was synthesised and used as a new interface to provide physical interactions between the metallic filler and the biopolymer matrix. This strategy allowed (i) overcoming the PLA/Mg interfacial adhesion weakness and (ii) modulating the composite hydrophilicity, bioactivity and biological behaviour. First, a full study of the influence of the copolymer incorporation on the morphological, wettability, thermal, thermo-mechanical and mechanical properties of PLA/Mg was investigated. Subsequently, the bioactivity was assessed during an in vitro degradation in simulated body fluid (SBF). Finally, biological studies with stem cells were carried out. The results showed an increase of the interfacial adhesion by the formation of a new interphase between the hydrophobic PLA matrix and the hydrophilic Mg filler. This interface stabilization was confirmed by a decrease in the damping factor (tanδ) following the copolymer addition. The latter also proves the beneficial effect of the composite hydrophilicity by selective surface localization of the hydrophilic PEO leading to a significant increase in the protein adsorption. Furthermore, hydroxyapatite was formed in bulk after 8 weeks of immersion in the SBF, suggesting that the bioactivity will be noticeably improved by the addition of the diblock copolymer. This ceramic could react as a natural bonding junction between the designed implant and the fractured bone during osteoregeneration. On the other hand, a slight decrease of the composite mechanical performances was noted.

In vitro characterization of novel nanostructured collagen-hydroxyapatite composite scaffolds doped with magnesium with improved biodegradation rate for hard tissue regeneration

New materials are required for bone healing in regenerative medicine able to temporarily substitute damaged bone and to be subsequently resorbed and replaced by endogenous tissues. Taking inspiration from basic composition of the mammalian bones, composed of collagen, apatite and a number of substitution ions, among them magnesium (Mg2+), in this work, novel composite scaffolds composed of collagen(10%)-hydroxyapatite (HAp)(90%) and collagen(10%)-HAp(80%)-Mg(10%) were developed. The lyophilization was used for composites preparation. An insight into the nanostructural nature of the developed scaffolds was performed by Scanning Electron Microscopy coupled with Energy Dispersive X-Ray and Transmission Electron Microscopy coupled with Energy Dispersive X-Ray. The HAp nanocrystallite clusters and Mg nanoparticles were homogeneously distributed within the scaffolds and adherent to the collagen fibrils. The samples were tested for degradation in Simulated Body Fluid (SBF) solution by soaking for up to 28 days. The release of Mg from collagen(10%)-HAp(80%)-Mg(10%) composite during the period of up to 21 days was attested, this composite being characterized by a decreased degradation rate with respect to the composite without Mg. The developed composite materials are promising for applications as bone substitute materials favouring bone healing and regeneration.

Exploring key ionic interactions for magnesium degradation in simulated body fluid – A data-driven approach

We have studied the degradation of pure magnesium wire in simulated body fluid and its subsets under physiological conditions to enable the prediction of the degradation rate based on the medium's ionic composition. To this end, micro-computed tomography and scanning electron microscopy with energy-dispersive X-ray spectroscopy were used, followed by a tree regression analysis. A non-linear relationship was found between degradation rate and the precipitation of calcium salts. The mean absolute error for predicting the degradation rate was 1.35 mm/yr. This comparatively high value indicates that ionic interactions were exceedingly complex or that an unknown parameter determining the degradation may exist.

Physical, electrochemical and biological evaluations of spin-coated ε-polycaprolactone thin films containing alumina/graphene/carbonated hydroxyapatite/titania for tissue engineering applications.

Composite structures are at the frontier of materials science and engineering and polymeric/ceramic composites present one of their most prospective subsets. Prior studies have shown both improvements and deteriorations of properties of polymers upon the addition of ceramic phases to them, but not many studies have dealt with the direct comparison of chemically distinct inorganic additives. The goal of this study was to compare the properties of ε-polycaprolactone (PCL) thin films supplemented with alumina, graphene, carbonated hydroxyapatite or titania particles, individually, in identical amounts (12wt%). The composite films were analyzed for their phase composition, grain size, morphology, surface roughness, porosity, cell response, mechanical properties and electrochemical performance. Each additive imparted one or more physical or biological properties onto PCL better than others. Thus, alumina increased the microhardness of the films better than any other additive, with the resulting values exceeding 10MPa. It also led to the formation of a composite with the least porosity and the greatest stability to degradation in simulated body fluid based on open circuit potential (OCP) measurements and electrochemical impedance spectroscopy (EIS). Titania made the surface of PCL roughest, which in combination with its high porosity explained why it was the most conducive to the growth of human fibroblasts, alongside being most prone to degradation in wet, corrosive environments and having the highest Poisson's ratio. Graphene, in contrast, made the surface of PCL smoothest and the bulk structure most porous, but also most conductive, with the OCP of -37mV. The OCP of PCL supplemented with carbonated hydroxyapatite had the highest OCP of -134mV and also the highest mechanical moduli, including the longitudinal (781MPa), the shear (106MPa), the bulk (639MPa), and the elastic (300MPa). The only benefit of the deposition of multilayered PCL films supplemented with all four inorganic additives was to enable a relatively high resistance to degradation. This study demonstrates that the properties of thin PCL films could be effectively optimized through the simple choice of appropriate inorganic additives dispersed in them. There is no single additive that proves ideal for improving all the properties of interest in PCL thin films, but their choice should be adjusted to the actual application. One such method of compositional optimization could prove crucial in the effort to develop biocomposites for superior performance in tissue engineering applications.

Effects of Ag, Cu or Ca addition on microstructure and comprehensive properties of biodegradable Zn-0.8Mn alloy

Zn-0.8Mn (in wt%) alloy with good ductility is used for design of novel Zn-0.8Mn-0.4x (x = Ag, Cu or Ca) alloys. Hot extrusion not only eliminates brittleness of the as-cast alloys but also significantly improves their strengths. Among them, Zn-0.8Mn-0.4Ca exhibits the highest strength, Zn-0.8Mn-0.4Ag exhibits the highest ductility, but Zn-0.8Mn-0.4Cu exhibits the best combination of strength and ductility. The minor addition of Ag, Cu or Ca accelerates alloy degradation in simulated body fluid. However, Cu addition much improves in vitro biocompatibility and endows antibacterial ability of Escherichia coli. Overall, Zn-0.8Mn-0.4Cu alloy has the best comprehensive properties.

Calcium phosphate composite cements based on simple mixture of brushite and apatite phases

The composite cements based on simple mixtures brishite and apatite with ratio 70/30, 50/50, 30/70 were developed. The processes of phase formation, microstructure and mechanical properties were studied. The kinetics of degradation in simulated body fluid depending on the microstructure and the materials phase composition was carried out. The biological test in vitro were performed using the MTT-test on the human fibroblast immortalized (hFB) cell line and the human osteosarcoma cell line MG-63. The materials didn’t have acute cytoxicity and possessed surface matrix properties. It was determined that the both line of cells actively proliferated, with viable cells values higher 20-60 % then control at all observation periods.

Mechanical and degradation property improvement in a biocompatible Mg-Ca-Sr alloy by thermomechanical processing.

Magnesium-based alloys have attracted interest as a potential material to comprise biomedical implants that are simultaneously high-strength and temporary, able to provide stabilization before degrading safely and able to be excreted by the human body. Many alloy systems have been evaluated, but this work reports on improved properties through hot extrusion of one promising alloy: Mg-1.0 wt% Ca-0.5 wt%Sr. This alloy has previously demonstrated promising toxicity and degradation properties in the as-cast and rolled conditions. In the current study extrusion causes a dramatic improvement in the mechanical properties in tension and compression, as well as a low in vitro degradation rate. Microstructure (texture, second phase distribution, and grain size), bulk mechanical properties, flow behavior, degradation in simulated body fluid, and effect on osteoblast cyctotoxicity are evaluated and correlated to extrusion temperature. Maximum yield strength of 300 MPa (above that of annealed 316 stainless steel) with 10% elongation is observed, making this alloy competitive with existing implant materials.

Electrospun PCL/HA coated friction stir processed AZ31/HA composites for degradable implant applications​

Hydroxyapatite (HA) nanoparticles were dispersed in AZ31 alloy by friction stir processing (FSP) to produce AZ31/HA metal matrix composites. The composite surface was acid treated using HNO3 and coated with polycaprolactone/HA (PCL/HA) mat by electrospinning. Coating parameters were optimized to obtain PCL/HA nanocomposite fibrous mat with an adhesion strength of 4B Grade (ASTM D3359-09 tape test) on AZ31/HA composite surface. Presence of HA on the substrate and in the coating helps in enhancing biomineralization and develop thick CaP layer on the surface which also facilitates controlled degradation in simulated body fluid at normal physiological conditions of pH 7.2 and 37°C. Rat skeletal muscle cells culture study showed better adhesion and proliferation on coated samples compared to the uncoated samples. The combination of electrospun nanofibrous PCL/HA composite coating on acid pre-treated FSPed AZ31/HA composite surface seems to have the potential for biodegradable magnesium implant applications with enhanced bioactivity for tissue regeneration.

A Study on Degradation Behavior of 3D Printed Gellan Gum Scaffolds

Gellan gum (GG) is one of the natural hydrogels showing potential for tissue engineering. In this study, we investigate GG for wound dressing and cartilage applications through 3D printing which allows for the creation of complex structures and scaffolds with different porosities. Degradation of two different GG scaffold designs and one solid sample were performed using both simulated body fluid and phosphate buffered saline. It was found that the scaffolds with a higher surface area to mass ratio have a higher degradation rate, and that the compressive modulus and strength increase after degradation in simulated body fluid.

Development of 70/30 Poly-L-DL-Lactic Acid Filaments for 3D Printers (Part 2): Mechanical and Surface Properties of Bioabsorbable Printed Plates for Biomedical Applications

The mechanical, chemical, roughness and wettability properties of 70/30 poly (L,DL-lactide acid) three-dimensional (3D)-printed surgical plates made with extruded polymer filaments developed in the first part of this work were investigated. The plates were printed with horizontal (HRZ) and vertical (VRT) running layer orientations and evaluated by tensile, Fourier transform infrared (FTIR), optical perfilometry and wettability tests before and after degradation in simulated body fluid (SBF) for 21 days. The results show that the ultimate tensile strength (UTS) of HRZ plates before immersion in SBF was higher (34.1 MPa) than that of VRT plates (31.8 MPa). The Young’s modulus (E) of HRZ plates and VRT plates are similar (4 GPa). After immersion in SBF, the UTS of HRZ plates dropped to 20.5 MPa and E decreased to 3.3 GPa. VRT were not tested after SBF immersion due to the large degradation. FTIR analysis showed no evidence of chemical change in the plates after immersion in SBF. The roughness parameter R3z of VRT surfaces (19.54 µm) was higher than that of the HRZ surfaces (12.80 µm). The roughness parameters increased after degradation in SBF (p = 0.7048). The contact angles of HRZ surfaces before immersion in SBF (66.28°) were higher than after immersion in SBF (18.12°); the same behavior was also observed in VRT plates.

In vitro study on the degradation of lithium-doped hydroxyapatite for bone tissue engineering scaffold

Li-doped hydroxyapatite (LiHA) which is prepared through introducing low dose of Li into hydroxyapatite (HA) has been increasingly studied as a bone tissue-engineered scaffold. The degradation properties play a crucial role in the success of long-term implantation of a bone tissue-engineered construct. Herein, the in vitro degradation behaviors of LiHA scaffolds via two approaches were investigated in this study: solution-mediated degradation and osteoblast-mediated degradation. In solution-mediated degradation, after being immersed in simulated body fluid (SBF) for some time, some characteristics of these scaffolds (such as release of ionized lithium and phosphate, pH change, mechanical properties, cytocompatibility and SEM surface characterization) were systematically tested. A similar procedure was also employed to research the degradation behaviors of LiHA scaffolds in osteoblast-mediated degradation. The results suggested that the degradation in SBF and degradation in culture medium with cell existed distinguishing mechanisms. LiHA scaffolds were degraded via a hydrolytic mechanism when they were soaked in SBF. Upon degradation, an apatite precipitation (layer) was formed on the surfaces of scaffolds. While a biological mechanism was presented for the degradation of scaffolds in cell-mediated degradation. Compared with pure HA, LiHA scaffolds had a better effect on the growth of osteoblast cells, meanwhile, the release amount of PO43− in a degradation medium indicated that osteoblasts could accelerate the degradation of LiHA due to the more physiological activities of osteoblast. According to the results from compressive strength test, doping Li into HA could enhance the strength of HA. Moreover, the results from MTT assay and SEM observation showed that the degradation products of LiHA scaffolds were beneficial to the proliferation of osteoblasts. The results of this research can provide the theoretical basis for the clinical application of LiHA scaffolds.