Mechanical properties of biodegradable polymer sutures coated with bioactive glass

Combining commercially available Polyglactin 910 (Vicryl®) sutures with bioactive glass powder offers new possibilities for application of composite materials in tissue engineering. Commercial bioactive glass (45S5 Bioglass®) powder was used to coat Vicryl® sutures and the tensile strength of the sutures was tested before and after immersion in simulated body fluid (SBF) as a means to assess the effect of the bioactive glass coating on suture degradation. Different gauge lengths (126.6 and 111.6 mm) and strain rates (2.54, 11.4 and 25.4 mm/min) were tested. The tensile strength of composite sutures was slightly lower than that of as-received Vicryl® sutures (404 MPa versus 463 MPa). However after 28 days immersion in SBF the residual tensile strength of the coated sutures was significantly higher, indicating a protective function of the Bioglass® coating. The tensile strength results were similar for the different gauge lengths and strain rates investigated. A qualitative explanation for the effect of bioactive glass coating on polymer degradation is offered.     

Hydroxyapatite/Bioactive Glass Films Produced by a Sol–Gel Method: In Vitro Behavior

Hydroxyapatite (HA) and HA/bioactive glass (49S) films were deposited on Si(100) substrates by a sol–gel dip‐coating method. The microstructure and in vitro bioactivity of the films were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X‐ray photoelectron spectroscopy (XPS). Polycrystalline HA and amorphous bioactive glass films were obtained after annealing at 600 and 400 °C, respectively. The crystallization temperature of HA was determined to be around 568 °C. The surfaces of the HA films were covered with an apatite layer consists of spherulites formed by nanosized needle‐like aggregates after the soaking in simulated body fluid (SBF) for 10 days, while amorphous HA/bioactive glass surface was covered with larger spherical crystallites. Both XPS and EDS results obtained from HA/bioactive glass film, after soaking in SBF, showed increasing P amounts on the surface at the expense of Si. The higher density of the newly formed layer on HA/bioactive glass surface than that of the HA surface after 10 days of soaking was evidence of increased reaction rate and apatite forming ability when bioactive glass layer is present on the HA films.     

Bioresorbable and bioactive composite materials based on polylactide foams filled with and coated by Bioglass® particles for tissue engineering applications

Poly(DL-lactide) (PDLLA) foams and bioactive glass (Bioglass®) particles were used to form bioresorbable and bioactive composite scaffolds for applications in bone tissue engineering. A thermally induced phase separation process was applied to prepare highly porous PDLLA foams filled with 10 wt % Bioglass® particles. Stable and homogeneous layers of Bioglass® particles on the surface of the PDLLA/Bioglass® composite foams as well as infiltration of Bioglass® particles throughout the porous network were achieved using a slurry-dipping technique. The quality of the bioactive glass coatings was reproducible in terms of thickness and microstructure. In vitro studies in simulated body fluid (SBF) were performed to study the formation of hydroxyapatite (HA) on the surface of the PDLLA/Bioglass® composites, as an indication of the bioactivity of the materials. Formation of the HA layer after immersion in SBF was confirmed by X-ray diffraction and Raman spectroscopy measurements. The rate of HA formation in Bioglass®-coated samples was higher than that observed in non-coated samples. SEM analysis showed that the HA layer thickness rapidly increased with increasing time in SBF in the Bioglass®-coated samples. The high bioactivity of the developed composites suggests that the materials are attractive for use as bioactive, resorbable scaffolds in bone tissue engineering.     

Feasibility, tailoring and properties of polyurethane/bioactive glass composite scaffolds for tissue engineering

This research work aims to propose highly porous polymer/bioactive glass composites as potential scaffolds for hard-tissue and soft-tissue engineering. The scaffolds were prepared by impregnating an open-cells polyurethane sponge with melt-derived particles of a bioactive glass belonging to the SiO₂–P₂O₅–CaO–MgO–Na₂O–K₂O system (CEL2). Both the starting materials and the composite scaffolds were investigated from a morphological and structural viewpoint by X-ray diffraction analysis and scanning electron microscopy. Tensile mechanical tests, carried out according to international ISO and ASTM standards, were performed by using properly tailored specimens. In vitro tests by soaking the scaffolds in simulated body fluid (SBF) were also carried out to assess the bioactivity of the porous composites. It was found that the composite scaffolds were highly bioactive as after 7 days of soaking in SBF a HA layer grew on their surface. The obtained polyurethane/CEL2 composite scaffolds are promising candidates for tissue engineering applications.     

Characterisation of the bioactive behaviour of sol–gel hydroxyapatite–CaO and hydroxyapatite–CaO–bioactive glass composites

The fabrication and characterization of sol–gel derived hydroxyapatite–calcium oxide (HAp–CaO) material is investigated focusing on the effect of the addition of a bioactive glass on the material bioactive behaviour through the fabrication of a novel HAp–CaO (70 wt.%)–bioactive glass (30 wt.%) composite material. The bioactive behaviour of the materials was assessed by immersion studies in Simulated Body Fluid (SBF) and the alterations of the materials surfaces after soaking periods in SBF were characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). A brittle and weakly crystalline carbonate hydroxyapatite (HCAp) layer was found to develop on the surface of all samples, few hours after immersion in SBF, confirming the high bioactivity of the material. Alterations of the morphology of the developed HCAp layer, which led to a more compact structure, were observed on the surface of composite samples after 7 days of immersion in SBF. The presence of the CaO phase seems to accelerate the formation of HCAp, while the bioactive glass affects both the morphology and cohesion of the developed layer.     

Investigation of emulsified,acid and acid-alkali catalyzed mesoporous bioactive glass microspheres for bone regeneration and drug delivery

Acid-catalyzed mesoporous bioactive glass microspheres (MBGMs-A) and acid-alkali co-catalyzed mesoporous bioactive glass microspheres (MBGMs-B) were successfully synthesized via combination of sol-gel and water-in-oil (W/O) micro-emulsion methods. The structural, morphological and textural properties of mesoporous bioactive glass microspheres (MBGMs) were characterized by various techniques. Results show that both MBGMs-A and MBGMs-B exhibit regularly spherical shape but with different internal porous structures, i.e., a dense microstructure for MBGMs-A and internally porous structure for MBGMs-B. ²⁹Si NMR data reveal that MGBMs have low polymerization degree of silica network. The in vitro bioactivity tests indicate that the apatite formation rate of MBGMs-B was faster than that of MBGMs-A after soaking in simulated body fluid (SBF) solution. Furthermore, the two kinds of MBGMs have similar storage capacity of alendronate (AL), and the release behaviors of AL could be controlled due to their unique porous structure. In conclusion, the microspheres are shown to be promising candidates as bone-related drug carriers and filling materials of composite scaffold for bone repair.     

Fabrication and characterization of silk fibroin/bioactive glass composite films

Composite films of silk fibroin (SF) with nano bioactive glass (NBG) were prepared by the solvent casting method, and the structures and properties of the composite films were characterized. Fourier transform infrared (FT-IR) spectroscopy analysis shows that the random coil and β-sheet structure co-exist in the SF films. Results of field emission scanning electron microscope (FESEM) indicate that the NBG particles are uniformly dispersed in the SF films. The measurements of the water contact angles suggest that the incorporation of NBG into SF can improve the hydrophilicity of the composites. The bioactivity of the composite films was evaluated by soaking in 1.5 times simulated body fluid (1.5 × SBF), and formation of a hydroxycarbonate apatite (HCA) layer was determined by XRD and FESEM. The results show that the SF/NBG composite film is bioactive as it induces the formation of HCA on the surface of the composite film after soaking in 1.5 × SBF for 7 days. In vitro osteoblasts attachment and proliferation tests show that the composite film is a good matrix for the growth of osteoblasts. Consequently, the incorporation of NBG into the SF film can enhance both the bioactivity and biocompatibility of the film, which suggests that the SF/NBG composite film may be a potential biomaterial for bone tissue engineering.     

Alkali oxide containing mesoporous bioactive glasses: Synthesis,characterization and in vitro bioactivity

We report, for the first time, the synthesis of sodium oxide containing mesoporous bioactive quaternary glasses and compared with two different mesoporous ternary silicate systems by modified sol–gel process. With the aid of three different glass systems, a systematic analysis has been made on phosphorous-bearing (P-bearing) and phosphorous-free (P-free) mesoporous bioactive glasses to investigate the role of phosphorus on in vitro bioactivity of various silicate glasses with constant alkali oxide content. The combined use of multiple analytical techniques XRD, FTIR, SEM, nitrogen adsorption/desorption analysis before and after soaking in the SBF solution allowed us to establish strong correlation between composition, pore structure and bioactivity. We find that the P-bearing mesoporous glasses show the rapid hydroxycarbonate apatite (HCA) crystallization than P-free mesoporous glasses independent of calcium content. The present study reveals that the presence of phosphorous jointly with calcium in the bioactive glass system significantly enhances the rate of apatite formation as well as crystallization of apatite phase. Additionally, we find that a glass with sodium orthophosphate rich phase enhances the solubility when immersed in SBF and further accelerate the kinetics of apatite formation. The influences of the chemical composition and their superior textural properties on bioactivity are explained in terms of the unique structure of mesoporous bioactive glasses.     

Fabrication and characterization of bioactive silk fibroin/wollastonite composite scaffolds

Composite scaffolds of silk fibroin (SF) with bioactive wollastonite were prepared by freeze-drying. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy analysis showed that random coil and β-sheet structure co-existed in the SF scaffold. The mechanical performance, surface hydrophilicity and water-uptake capacity of the composite scaffolds were improved compared with those of pure SF scaffold. The bioactivity of the composite scaffold was evaluated by soaking in a simulated body fluid (SBF), and formation of a hydroxycarbonate apatite (HCA) layer was determined by FT-IR and XRD. The results showed that the SF/wollastonite composite scaffold was bioactive as it induced the formation of HCA on the surface of the composite scaffold after soaking in SBF for 5 days. In vitro cell attachment and proliferation tests showed that the composite scaffold was a good matrix for the growth of L929 mouse fibroblast cells. Consequently, the incorporation of wollastonite into the SF scaffold can enhance both the mechanical strength and bioactivity of the scaffold, which suggests that the SF/wollastonite composite scaffold may be a potential biomaterial for tissue engineering.     

Preparation and characterization of bioactive and biodegradable Wollastonite/poly(D,L-lactic acid) composite scaffolds

Composite scaffolds of poly(D,L-lactic acid) (PDLLA) with bioactive wollastonite were fabricated by the conventional solvent casting-particulate leaching method. The pore structures and morphology of the scaffolds were determined by scanning electron microscopy (SEM). The bioactivity of the composites was evaluated by soaking in a simulated body fluid (SBF), and the formation of the hydroxyapatite (HAp) layer was determined by SEM and energy-dispersive spectrometer. The results showed that the wollastonite/PDLLA composites were bioactive as it induced the formation of HAp on the surface of the composite scaffolds after soaking in SBF for seven days. In addition, pH and ion concentration changes of SBF solutions with composite scaffolds were examined. The results showed that the composites could release Ca and Si ions, which could neutralize the acidic degradation by-products of the PDLLA, and stabilize the pH of the SBF solutions between 6.7 and 7.2 within a three-week soaking period. Furthermore, the measurements of the water contact angles suggested that incorporation of wollastonite into PDLLA could improve the hydrophilicity of the composites and the enhancement was dependent on the wollastonite content. All these results suggest that incorporation of wollastonite into PDLLA might be a useful approach for the preparation of composite scaffolds for tissue repair and tissue-engineering applications.     

Fabrication of bioactive composite by developing PLLA onto the framework of sintered HA scaffold

Composite porous scaffolds of hydroxyapatite (HA)/poly-l-lactide (PLLA) were fabricated by a two-step immersing replication method. Structure and mechanical properties of both the single HA scaffold and the composite HA/PLLA scaffold were determined. The bioactivity of the scaffolds was evaluated by soaking in a simulated body fluid (SBF), and the formation of the apatite layer was determined by X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and Energy-Dispersive Spectrometer (EDS). The results showed that without changing the highly interconnected porous structure, the HA/PLLA composite scaffold was mechanically enhanced to a great deal of extent compared with single HA scaffold. On the other hand, it is also suggested that the HA/PLLA scaffold was bioactive as it induced the formation of apatite on the surface of the composite scaffolds after soaking in SBF for 7 days.     

Bioactivity of CaSiO<Subscript>3</Subscript>/poly-lactic acid (PLA) composites prepared by various surface loading methods of CaSiO<Subscript>3</Subscript> powder

Mixing bioactive ceramic powders with polymers is an effective method for generating bioactivity to the polymer-matrix composites but it is necessary to incorporate up to 40 vol% of bioactive ceramic powder. However, such a high mixing ratio offsets the advantages of the flexibility and formability of polymer matrix and it would be highly advantageous to lower the mixing ratio. Since surface loading of ceramic powders in the polymer is thought to be an effective way of reducing the mixing ratio of the ceramic powder while maintaining bioactive activity, CaSiO₃/poly-lactic acid (PLA) composites were prepared by three methods; (1) casting, (2) spin coating and (3) hot pressing. In methods (1) and (2), a suspension was prepared by dissolving PLA in chloroform and dispersing CaSiO₃ powder in it. The suspension was cast and dried to form a film in the case of method (1) while it was spin-coated on a PLA substrate in method (2). In method (3), CaSiO₃ powder was surface loaded on to a PLA substrate by hot-pressing. The bioactivity of these samples was investigated in vitro using simulated body fluid (SBF). Apatite formation was not observed in the samples prepared by method (1) but some apatite formation was achieved by mixing polyethylene glycol (PEG) with the PLA, producing a porous polymer matrix. In method (2), apatite was clearly observed after soaking for 7 days. Enhanced apatite formation was observed in method (3), the thickness of the resulting apatite layers becoming about 20 μm after soaking for 14 days. Since the amount of CaSiO₃ powder used in these samples was only ≤0.4 vol%, it is concluded that this preparation method is very effective in generating bioactivity in polymer-matrix composites by loading with only very small amounts of ceramic powder.     

Assessment of in vitro bioactivity of SiO2-BaO-ZnO-B2O3-Al2O3 glasses: An optico-analytical approach

Bioactive glasses are an important subclass of biomaterials. The bioactivity of a glass depends on its initial constituents and their respective amounts. In the present investigation, five barium-zinc-borosilicate glass samples have been studied by varying Al₂O₃ mol% to check their bioactivity. The optical and bioactive properties of pristine glasses are compared with glasses soaked in Simulated Body Fluid (SBF) for 10 and 30 days using pH measurement, Ultraviolet–visible-Near Infrared-red (UV–vis–NIR), Fourier Transform Infra-Red (FTIR) spectroscopy, X-ray diffraction and Scanning Electron Microscopy (SEM) techniques. Although calcium is not present as an initial constituent in glass composition, yet bioactivity is observed in some glass samples after dipping them in SBF.     

Effect of nanoparticulate bioactive glass particles on bioactivity and cytocompatibility of poly(3-hydroxybutyrate) composites

This work investigated the effect of adding nanoparticulate (29 nm) bioactive glass particles on the bioactivity, degradation and in vitro cytocompatibility of poly(3-hydroxybutyrate) (P(3HB)) composites/nano-sized bioactive glass (n-BG). Two different concentrations (10 and 20 wt %) of nanoscale bioactive glass particles of 45S5 Bioglass composition were used to prepare composite films. Several techniques (Raman spectroscopy, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray) were used to monitor their surface and bioreactivity over a 45-day period of immersion in simulated body fluid (SBF). All results suggested the P(3HB)/n-BG composites to be highly bioactive, confirmed by the formation of hydroxyapatite on material surfaces upon immersion in SBF. The weight loss and water uptake were found to increase on increasing bioactive glass content. Cytocompatibility study (cell proliferation, cell attachment, alkaline phosphatase activity and osteocalcin production) using human MG-63 osteoblast-like cells in osteogenic and non-osteogenic medium showed that the composite substrates are suitable for cell attachment, proliferation and differentiation.     

多孔硅酸钙生物陶瓷的制备及体外活性和降解性研究

以聚乙二醇为造孔剂,制备了多孔硅酸钙生物陶瓷.应用本文提供的方法,可制得孔连通性好、气孔率53.7%-73.6%、抗压强度4.9-48.5MPa、大孔孔径200-500μm的多孔陶瓷.研究表明,多孔硅酸钙生物陶瓷的力学强度随造孔剂含量的增加而明显降低,而气孔率则相反.应用模拟体液浸泡实验研究了多孔陶瓷的体外生物活性和降解性.研究表明,样品在模拟体液中浸泡1天表面就全部被碳酸代羟基磷灰石层覆盖住.气孔率为63.1%的样品7天的降解率达7.14%,具有良好的降解性.研究结果显示多孔硅酸钙生物陶瓷有望作为硬组织修复支架材料用.     

In vitro physicochemical properties, osteogenic activity, and immunocompatibility of calcium silicate-gelatin bone grafts for load-bearing applications

The use of a composite made of natural polymer gelatin and bioactive calcium silicate resembling the morphology and properties of natural bone may provide a solution to the problem of ceramic brittleness for load-bearing applications. The in vitro bioactivity, degradability, osteogenic activity, and immunocompatibility of three types of calcium silicate-gelatin composite bone grafts were characterized. The osteogenic activity and immunocompatibility were evaluated by incubating the bone grafts with human dental pulp cells. After soaking in a simulated body fluid (SBF) for 1 day, all materials were covered with clusters of "bone-like" apatite spherulites. The control material without gelatin exhibited an insignificant change in strength, degradability, and porosity and a small weight loss of 6% after 180 days of soaking in the SBF solution. In contrast, the soaking time imposed in this study did have a statistically significant effect on compressive strength, porosity, and weight loss of the gelatin-containing composites. After 180 days of soaking, the composite with 10 wt % gelatin lost 47% and 10% in compressive strength and weight, respectively, with a porosity of 23%. However, the presence of gelatin promoted greater cell attachment and proliferation on the composite bone grafts. Pulp cells on the calcium silicate-gelatin bone grafts expressed higher levels of osteocalcin, osteopontin, and bone sialoprotein. The inhibition of inducible nitric oxide synthase and interleukin-1 expression and the activation of interleukin-10 were increased with increasing gelatin content. Overall, these findings provide evidence that composite bone grafts containing 10 wt % gelatin with a high initial strength were bioactive, nontoxic, and osteogenic and may be able to promote bone healing for load-bearing applications.     

Bioactivity of CaSiO<Subscript>3</Subscript>/poly-lactic acid (PLA) composites prepared by various surface loading methods of CaSiO<Subscript>3</Subscript> powder

Mixing bioactive ceramic powders with polymers is an effective method for generating bioactivity to the polymer-matrix composites but it is necessary to incorporate up to 40 vol% of bioactive ceramic powder. However, such a high mixing ratio offsets the advantages of the flexibility and formability of polymer matrix and it would be highly advantageous to lower the mixing ratio. Since surface loading of ceramic powders in the polymer is thought to be an effective way of reducing the mixing ratio of the ceramic powder while maintaining bioactive activity, CaSiO₃/poly-lactic acid (PLA) composites were prepared by three methods; (1) casting, (2) spin coating and (3) hot pressing. In methods (1) and (2), a suspension was prepared by dissolving PLA in chloroform and dispersing CaSiO₃ powder in it. The suspension was cast and dried to form a film in the case of method (1) while it was spin-coated on a PLA substrate in method (2). In method (3), CaSiO₃ powder was surface loaded on to a PLA substrate by hot pressing. The bioactivity of these samples was investigated in vitro using simulated body fluid (SBF). Apatite formation was not observed in the samples prepared by method (1) but some apatite formation was achieved by mixing polyethylene glycol (PEG) with the PLA, producing a porous polymer matrix. In method (2), apatite was clearly observed after soaking for 7 days. Enhanced apatite formation was observed in method (3), the thickness of the resulting apatite layers becoming about 20 μm after soaking for 14 days. Since the amount of CaSiO₃ powder used in these samples was only ≤0.4 vol%, it is concluded that this preparation method is very effective in generating bioactivity in polymer-matrix composites by loading with only very small amounts of ceramic powder.     

Dissolution behavior and bioactivity study of glass ceramic scaffolds in the system of CaO–P2O5–Na2O–ZnO prepared by sol–gel technique

Three-dimensional glass ceramic scaffolds from the system CaO–P₂O₅–Na₂O–ZnO have been prepared by coating polyurethane foams with sol–gel derived glass slurry. Main phase catena hexaphosphate (Ca₄P₆O₁₉), minor phases calcium pyrophosphate (β-Ca₂P₂O₇) and calcium metaphosphate (β-Ca(PO₃)₂) were detected in the prepared glass ceramics. In order to assess the potential use in hard tissue engineering, the dissolution and precipitation behavior of the glass ceramics was investigated in vitro after soaking in simulated body fluid (SBF) for different periods of time, and the bioactivity and biocompatibility studies were conducted using mouse MC3T3-E1. Ca₄P₆O₁₉ phase showed a good chemical durability in SBF solution over the period time of soaking. However, there were small quantities of apatite-like deposits formed on the surfaces after soaking 28 days, exhibiting a poor ability of inducing calcification in SBF. In vitro cell culture, a high degree of cell adhesion and spreading was achieved and large number of mineralized deposits composed of Ca, P and Zn were detected in these porous scaffolds. These results confirmed the biocompatibility and bioactivity of the glass ceramics and the positive effects on mouse MC3T3-E1 cell behavior although no continuous apatite layer was formed on scaffold surfaces after soaking in SBF, and also demonstrated that Zn doped this glass ceramics could strongly stimulate the formation of mineralized deposits in vitro culture of MC3T3-E1 cells.     

Novel bioresorbable and bioactive composites based on bioactive glass and polylactide foams for bone tissue engineering

Bioresorbable and bioactive tissue engineering scaffolds based on bioactive glass (45S5 Bioglass®) particles and macroporous poly(DL-lactide) (PDLLA) foams were fabricated. A slurry dipping technique in conjunction with pretreatment in ethanol was used to achieve reproducible and well adhering bioactive glass coatings of uniform thickness on the internal and external surfaces of the foams. In vitro studies in simulated body fluid (SBF) demonstrated rapid hydroxyapatite (HA) formation on the surface of the composites, indicating their bioactivity. For comparison, composite foams containing Bioglass® particles as filler for the polymer matrix (in concentration of up to 40 wt %) were prepared by freeze-drying, enabling homogenous glass particle distribution in the polymer matrix. The formation of HA on the composite surfaces after immersion in phosphate buffer saline (PBS) was investigated to confirm the bioactivity of the composites. Human osteoblasts (HOBs) were seeded onto as-fabricated PDLLA foams and onto PDLLA foams coated with Bioglass® particles to determine early cell attachment and spreading. Cells were observed to attach and spread on all surfaces after the first 90 min in culture. The results of this study indicate that the fabricated composite materials have potential as scaffolds for guided bone regeneration.     

溶胶-凝胶生物活性玻璃纤维的制备及其体外矿化性能研究

采用溶胶-凝胶法制备出CaO-P2O5-SiO2系统生物活性玻璃纤维．通过倒置相差显微镜、SEM、FTIR等测试手段考察了生物活性玻璃纤维的微观形貌和显微结构；采用生物材料的体外实验方法以及XRD、SEM、FTIR等测试手段研究了生物活性玻璃纤维在模拟生理体液（SBF）中浸泡后的表面反应产物的形成机理、结晶程度和微观形貌．结果表明，这种生物活性玻璃纤维是一种不连续的短纤维，具有较好的纤维形态和较高的生物活性，在短时间内即可在模拟生理体液（SBF）中形成茸毛状A类碳酸羟基磷灰石（HCA）层．