In vitro antibacterial activity and cytocompatibility of magnesium-incorporated poly(lactide-co-glycolic acid) scaffolds.

BACKGROUND: Bone defects are often combined with the risk of infection in the clinic, and artificial bone substitutes are often implanted to repair the defective bone. However, the implant materials are carriers for bacterial growth, and biofilm can form on the implant surface, which is difficult to eliminate using antibiotics and the host immune system. Magnesium (Mg) was previously reported to possess antibacterial potential. METHODS: In this study, Mg was incorporated into poly(lactide-co-glycolic acid) (PLGA) to fabricate a PLGA/Mg scaffold using a low-temperature rapid-prototyping technique. All scaffolds were divided into three groups: PLGA (P), PLGA/10 wt% Mg with low Mg content (PM-L) and PLGA/20 wt% Mg with high Mg content (PM-H). The degradation test of the scaffolds was conducted by immersing them into the trihydroxymethyl aminomethane-hydrochloric acid (Tris-HCl) buffer solution and measuring the change of pH values and concentrations of Mg ions. The antibacterial activity of the scaffolds was investigated by the spread plate method, tissue culture plate method, scanning electron microscopy and confocal laser scanning microscopy. Additionally, the cell attachment and proliferation of the scaffolds were evaluated by the cell counting kit-8 (CCK-8) assay using MC3T3-E1 cells. RESULTS: The Mg-incorporated scaffolds degraded and released Mg ions and caused an increase in the pH value. Both PM-L and PM-H inhibited bacterial growth and biofilm formation, and PM-H exhibited higher antibacterial activity than PM-L after incubation for 24 and 48 h. Cell tests revealed that PM-H exerted a suppressive effect on cell attachment and proliferation. CONCLUSIONS: These findings demonstrated that the PLGA/Mg scaffolds possessed favorable antibacterial activity, and a higher content of Mg (20%) exhibited higher antibacterial activity and inhibitory effects on cell attachment and proliferation than low Mg content (10%).

In vitro biocompatiability and mechanical properties of bone adhesive tape composite based on poly(butyl fumarate)/poly(propylene fumarate)-diacrylate networks.

Polyfumarate has been considered as injectable and biodegradable bone cement. However, its mechanical and degradation properties are particularly important. Therefore, the current study aimed to develop the properties by compositing poly (butyl fumarate)-based networks with hydroxyapatite nano-powders. In this regard, the poly (butyl fumarate) (PBF) matrix composite was compared with different components by evaluating their composition, mechanical properties, hydrophilicity, and biodegradability. Furthermore, their bioactivity in the phosphate-buffered saline (PBS) and, via applying mouse embryo osteoblast precursor cells (MC3T3-E1), their cell interaction, including adhesion, proliferation, and in vitro cytotoxicity assay, were assessed. The addition of hydroxyapatite improved the mechanical strength and modulus of PBF matrix composite. The composite reinforced with 3 wt% hydroxyapatite showed a higher lap-shear strength (1.68 MPa) and bonding strength (4.30 MPa), a maximum compression strength at fracture (95.18 MPa), modulus (925.29 MPa), and compression strength at yield (31.43 MPa), respectively. Also, hydrophilicity and in vitro degradation of the composite were enhanced in the presence of hydroxyapatite. In this condition, after a period of immersion (52 weeks) in PBS, the weight loss rate, and degradation rate of the composite increased. The composite proliferation, adhesion, and toxicity of MC3T3-E1 cells improved in comparison to the PBF matrix composite. Accordingly, controllable strength and degradation of the composite, along with its proven biocompatibility, make the composite a candidate for the treatment of comminuted fractures.

The influence of Sr and H3PO4 concentration on the hydration of SrCaHA bone cement.

Sr-contained calcium hydroxyapatite (SrCaHA) cement is a potential biomaterial for in vivo bone repair and surgery fixation due to its excellent biodegradability, bioactivity, biocompatibility, easily shaping and self-hardening. We had ever reported the in vitro physiochemical properties, biocompatibility and in vivo degradability of the SrCaHA cement obtained by mixing a cement powder of Ca(4)(PO(4))(2)O/CaHPO(4)/SrHPO(4) and a cement liquid of diluted H(3)PO(4) aqueous solution. In the present study, we intensively studied the influences of both Sr content and H(3)PO(4) concentration in diluted phosphoric acid aqueous solution on the setting time, hydration heat-liberation behaviours, and real-time microstructure and phase evolutions of the SrCaHA cement. The results show that both PO(4)(3-) and H(+) ions in PA solution attended the hydration reaction as reactants, and thus the increase of the PA concentration not only promoted the dissolution of Ca(4)(PO(4))(2)O but also pushed the hydration progress of SrCaHA bone cement. Sr content exhibits a remarkable retardation role on the apatite transformation of the SrCaHA cement pastes which probably attributed to its higher degree of supersaturation for yielding apatite crystals and lower transformation rate when exposed to the Sr(2+)-containing hydration system. This present results contribute to a better understanding on the hydration mechanism of the new SrCaHA cement and help to the more precisely controlling of its hydration process.

Enhancing Antibacterial Performance and Biocompatibility of Pure Titanium by a Two-Step Electrochemical Surface Coating.

A two-step electrochemical surface treatment has been developed to modify the CP Ti surface on commercially pure titanium grade 2 (CP Ti): (1) anodic oxidation to form TiO2 nanotube precoatings loaded with silver (Ag) and (2) microarc oxidation (MAO) to produce a porous Ca-P-Ag coating in an electrolyte containing Ag, Ca, and P. One-step MAO in the same electrolyte has also been used to produce porous Ca-P-Ag coatings without anodic oxidation and preloaded Ag as a control. Surface morphologies and alloying chemistry of the two coatings were characterized by SEM, EDS, and XPS. Biocompatibility and antimicrobial properties have been evaluated by the MTT method and co-culture of Staphylococcus aureus, respectively. It is demonstrated that porous coatings with high Ag content can be achieved on the CP Ti by the two-step treatment. The optimized MAO voltage for excellent comprehensive properties of the coating is 350 V, in which a suitable chemical equilibrium between Ag, Ca, and P contents and a Ca/P ratio of 1.67 similar to HA can be obtained, and the Ag particles are in the size of less than 100 nm and embedded into the underneath of the coating surface. After being contacted with S. aureus for 1 and 7 days, the average bactericidal rates were 99.53 and 89.27% and no cytotoxicity was detected. In comparison, the one-step MAO coatings contained less Ag, had a lower Ca/P ratio, and showed lower antimicrobial ability than the two-step treated samples.

Effects of different sulfonation times and post-treatment methods on the characterization and cytocompatibility of sulfonated PEEK.

Polyetheretherketone (PEEK) has been becoming a popular implant material in orthopaedic applications. The lack of bioactivity affects PEEK's long-term lifetime, and appropriate surface modification is an effective way to enhance its bioactivity. Sulfonation of PEEK can endow PEEK with a 3 D porous network surface and improve its bioactivity. This study is aimed at exploring an optimal sulfonation time and a post-treatment method of PEEK sulfonation. PEEK was immersed into concentrated sulfuric acid for different sulfonation times and experienced different post-treatment methods to turn into sulfonated PEEK (SPEEK). The immersion times were 0.5 min (SPEEK0.5), 1 min (SPEEK1), 3 min (SPEEK3), 5 min (SPEEK5) and 7 min (SPEEK7), and the post-treatment methods were acetone rinsing (SPEEK-T1), hydrothermal treatment (SPEEK-T2) and NaOH immersion (SPEEK-T3). Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy, hydrophilic property, ion release and cell viability evaluations were performed to optimize the sulfonation time, and the SEM, EDS, ion release and cell viability were analysed to optimize the post-treatment method. The results showed a porous network structure was formed on all samples of SPEEK, and the porous structure became more obvious and the S concentration increased with increasing sulfonation time. However, too long of an immersion time (SPEEK7) tended to damage the superficial porous structure and left a higher content of sulfuric acid, which could inhibit the growth of MC3T3E1 cells on its surface. In addition, the surface morphology, residual sulfuric acid and cytocompatibility of SPEEK-T1, SPEEK-T2 and SPEEK-T3 were not distinctly different. In conclusion, a 5-min sulfonation time was considered to be the optimal selection, and acetone rinsing, hydrothermal treatment and NaOH immersion showed the same effect in removing the residual sulfuric acid. The understanding of optimal sulfonation time and post-treatment method can provide a theoretical basis in preparing SPEEK for orthopaedic applications.

Evaluating the bioactivity of a hydroxyapatite-incorporated polyetheretherketone biocomposite.

BACKGROUND: Polyetheretherketone (PEEK) exhibits stable chemical properties, excellent biocompatibility, and rational mechanical properties that are similar to those of human cortical bone, but the lack of bioactivity impedes its clinical application. METHODS: In this study, hydroxyapatite (HA) was incorporated into PEEK to fabricate HA/PEEK biocomposite using a compounding and injection-molding technique. The tensile properties of the prepared HA/PEEK composites (HA content from 0 to 40 wt%) were tested to choose an optimal HA content. To evaluate the bioactivity of the composite, the cell attachment, proliferation, spreading and alkaline phosphatase (ALP) activity of MC3T3-E1 cells, and apatite formation after immersion in simulated body fluid (SBF), and osseointegration in a rabbit cranial defect model were investigated. The results were compared to those from ultra-high molecular weight polyethylene (UHMWPE) and pure PEEK. RESULTS: By evaluating the tensile properties and elastic moduli of PEEK composite samples/PEEK composites with different HA contents, the 30 wt% HA/PEEK composite was chosen for use in the subsequent tests. The results of the cell tests demonstrated that PEEK composite samples/PEEK composite exhibited better cell attachment, proliferation, spreading, and higher ALP activity than those of UHMWPE and pure PEEK. Apatite islands formed on the HA/PEEK composite after immersion in SBF for 7 days and grew continuously with longer time periods. Animal tests indicated that bone contact and new bone formation around the HA/PEEK composite were more obvious than those around UHMWPE and pure PEEK. CONCLUSIONS: The HA/PEEK biocomposite created by a compounding and injection-molding technique exhibited enhanced osteogenesis and could be used as a candidate of orthopedic implants.

Synthesis and cellular biocompatibility of two kinds of HAP with different nanocrystal morphology.

Two kinds of hydroxyapatite (HA) with different nanocrystal morphology were obtained via a simple aqueous precipitation method under different reactants molar ratios. Under Ca/P molar ratio of 1.67/1, rod-like crystal was produced, while under Ca/P molar ratio of 1.80/1, spherical crystal was produced. The spherical crystal was 40-60 nm in diameter, while the rod-like crystal was 40-55 nm in diameter and 79-100 nm in length. The influence of HA nanocrystal morphology on osteoblasts growth was assayed by MTT method and SEM. The results indicated that there was a significantly higher absorbency value on the surface of HA with spherical crystal in MTT assay than the latter. In the process of SEM observation, it is found that osteoblasts spread out a large quantity of nano-filopodias on spherical crystal surface, thus exhibiting much more active cell morphology. In conclusion, HA with spherical nanocrystal showed more favorable properties than that with rod-like one for osteoblasts.

Development of Sr-incorporated biphasic calcium phosphate bone cement.

To follow the design strategy of traditional biphasic calcium phosphate (BCP) ceramic, in the present study, strontium-doped biphasic calcium phosphate bone cement (Sr-BCPC) composites comprising Sr-ß-tricalcium phosphate (TCP)/Sr-hydroxyapatite (HAP) had been prepared for the first time using Sr x -ß-TCP/tetracalcium phosphate (TTCP) as a cement powder and diluted phosphoric acid as a cement liquid. The phase composition, setting time, compressive strength, washout resistance, in vitro degradation rate, microstructure evolutions, hydration dynamics and cytotoxicity of Sr-BCPC at various Sr contents were intensively investigated. It was found that the final cement product was composed of entangled Sr-HAP nano-needles and cobblestone-like Sr-ß-TCP sub-micron particles, and the weight percentages in the final cement product after hydration in simulated body fluid for 24 h were in the ranges of 60 wt%-70 wt% Sr-HAP and 30 wt%-40 wt% Sr-ß-TCP, respectively. Sr and the concentration of Sr exhibit significant effects on the phase compositions, compressive strength, setting time, in vitro degradation rate and cytotoxicity of the biphasic bone cement. In particular, the degradation rate increased considerably with the increase of the Sr-ß-TCP phase. It is anticipated that the introduction of the 'biphasic' design into calcium phosphate bone cements is an effective strategy to improve their degradation properties.

Development of a strontium-containing hydroxyapatite bone cement.

A new route was developed to synthesis a new type of strontium-containing hydroxyapatite (Sr-HAP) bone cement with precursors of tetracalcium phosphate (TTCP), strontium hydrogen phosphate (DSPA), dicalcium phosphate (DCPA), phosphate acid and water. The processing parameters and fundamental properties including pH value, setting time, compressive strength of final hardened body and the cytotoxicity for serial extracts of each cements were investigated. The result shows that the final product of the cement after setting for 24h is nonstoichiometic Sr-containing hydroxyapatite (Ca(10-m-x)Sr(x) square(m)(HPO4)y(PO4)6-y(OH)2-2m square2m, 0

[Application of polyvinyl alcohol in biomedical engineering].

This paper explicated the present application of poly- vinyl alcohol (PVA) in the field of biomedical engineering, such as artificial cartilage, drug delivery systems, microorganism enwrapping, cell micro-capsulation, anti-thrombin materials, and biomedical sponges. And a preliminary study of the good dispersion of PVA as a surfactant on nano-particles of hydroxyapatite was presented.

[Microencapsulation of immortalized mandibular condylar chondrocytes].

To explore the possibility of microencapsulation of chondrocytes in cartilage tissue engineering, immortalized manibular condylar chondrocytes (IMCCs) were microencapsuled by Alginate-polylysine-alginate (APA) method, according to air pressure shearing model. Phase contrast microscopy, trypan blue staining exclusion, cell number counting, HE staining and immunohistochemistry method were used to observe the morphology of the microencapsules, the growth character of cells, cartilage characteristics, and so on. The results showed that IMCC could survive and grow in microencapsule, and the viability rate of cells is more than 80 per cent. The diameter of microcapsule is 779 microns in average. The number of cell increased with time, and cells went into platform in about 20 days. Cells grew in clusters and cartilage specific proteoglycans and type II collagen were highly expressed. It was concluded that IMCC could form cartilage-like tissue within microencapsulation, implying that microencapsule technique might be applicable to cartilage tissue engineering.

Porous allograft bone scaffolds: doping with strontium.

Strontium (Sr) can promote the process of bone formation. To improve bioactivity, porous allograft bone scaffolds (ABS) were doped with Sr and the mechanical strength and bioactivity of the scaffolds were evaluated. Sr-doped ABS were prepared using the ion exchange method. The density and distribution of Sr in bone scaffolds were investigated by inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). Controlled release of strontium ions was measured and mechanical strength was evaluated by a compressive strength test. The bioactivity of Sr-doped ABS was investigated by a simulated body fluid (SBF) assay, cytotoxicity testing, and an in vivo implantation experiment. The Sr molar concentration [Sr/(Sr+Ca)] in ABS surpassed 5% and Sr was distributed nearly evenly. XPS analyses suggest that Sr combined with oxygen and carbonate radicals. Released Sr ions were detected in the immersion solution at higher concentration than calcium ions until day 30. The compressive strength of the Sr-doped ABS did not change significantly. The bioactivity of Sr-doped material, as measured by the in vitro SBF immersion method, was superior to that of the Sr-free freeze-dried bone and the Sr-doped material did not show cytotoxicity compared with Sr-free culture medium. The rate of bone mineral deposition for Sr-doped ABS was faster than that of the control at 4 weeks (3.28 ± 0.23 µm/day vs. 2.60 ± 0.20 µm/day; p<0.05). Sr can be evenly doped into porous ABS at relevant concentrations to create highly active bone substitutes.

Porous surface modified bioactive bone cement for enhanced bone bonding.

BACKGROUND: Polymethylmethacrylate bone cement cannot provide an adhesive chemical bonding to form a stable cement-bone interface. Bioactive bone cements show bone bonding ability, but their clinical application is limited because bone resorption is observed after implantation. Porous polymethylmethacrylate can be achieved with the addition of carboxymethylcellulose, alginate and gelatin microparticles to promote bone ingrowth, but the mechanical properties are too low to be used in orthopedic applications. Bone ingrowth into cement could decrease the possibility of bone resorption and promote the formation of a stable interface. However, scarce literature is reported on bioactive bone cements that allow bone ingrowth. In this paper, we reported a porous surface modified bioactive bone cement with desired mechanical properties, which could allow for bone ingrowth. MATERIALS AND METHODS: The porous surface modified bioactive bone cement was evaluated to determine its handling characteristics, mechanical properties and behavior in a simulated body fluid. The in vitro cellular responses of the samples were also investigated in terms of cell attachment, proliferation, and osteoblastic differentiation. Furthermore, bone ingrowth was examined in a rabbit femoral condyle defect model by using micro-CT imaging and histological analysis. The strength of the implant-bone interface was also investigated by push-out tests. RESULTS: The modified bone cement with a low content of bioactive fillers resulted in proper handling characteristics and adequate mechanical properties, but slightly affected its bioactivity. Moreover, the degree of attachment, proliferation and osteogenic differentiation of preosteoblast cells was also increased. The results of the push-out test revealed that higher interfacial bonding strength was achieved with the modified bone cement because of the formation of the apatite layer and the osseointegration after implantation in the bony defect. CONCLUSIONS: Our findings suggested a new bioactive bone cement for prosthetic fixation in total joint replacement.

The in situ synthesis of biphasic calcium phosphate scaffolds with controllable compositions, structures, and adjustable properties.

In this study, biphasic calcium phosphate (BCP) porous scaffolds with controllable phase compositions, controllable macropore percentages, and thus adjustable properties were in situ prepared by sintering a series of composites consisted of calcium phosphate cement (CPC) and porous resin negative mold made from rapid prototyping (RP) technique. The CPC pastes were formed by mixing a powder mixture of tetracalcium phosphate and anhydrous dicalcium phosphate with liquid phase of diluted phosphate acid solution. Results show that the phase composition was easily adjustable by controlling both weight ratio of the powder mixture to the liquid phase (P/L) and concentration of the liquid phase. The macropore structure of the BCP scaffold can be regulated by using different RP negative molds. Through in vitro compressive strength (CS) and immersion tests, it was demonstrated that both macropore percentage and phase composition played important roles in the CS and also the dissolving rates of the scaffolds. As the macropore percentage of the scaffold increased, its CS decreased but the dissolving rate increased; also, as the weight ratio of hydroxyapatite to tricalcium (HA/TCP) in the scaffold increased, the CS first increased and then decreased but the dissolving rate uniformly decreased. The CS values of the BCP scaffolds with a HA/TCP weight ratio of 59:41 were 5.84 +/- 1.16 MPa for a total porosity of approximately 67.67% containing a macropore percentage of 30%, and 3.34 +/- 0.79 MPa for a total porosity of approximately 70.90% containing a macropore percentage of 50%, respectively, comparable to the corresponding levels of human cancellous bone (2-12 MPa).