[Show abstract][Hide abstract] ABSTRACT: From physiological point of view, organic-inorganic composite nanofibers are envisioned promising substrates for bone tissue engineering. Biomineralization on polymeric nanofibers using simulated body fluid (SBF) is a common technique to obtain the composite nanofibers. Many factors, however, will affect the nucleation and crystal growth of deposited apatite, such as the additives like amino acids in SBF. In this study, electrospun composite nanofibers consisting of poly(L-lactide) (PLLA, 50wt%) and gelatin (50wt%) were soaked in 2.5 times SBF (2.5SBF) for different time periods (1, 2, 3, 5 and 7 days) to perform the biomineralization. Three amino acids (glycine, aspartic acid, or arginine) of different charge characteristics were introduced into the SBF, and their effects on nucleation and transformation of calcium phosphate depositions were systematically investigated. The results revealed that amino acids could take part in the early stage formation of pre-nucleation clusters, leading to different assemblies dependent closely on the feature of amino acid. In comparison with normal 2.5SBF, the presence of amino acid was able to enhance the preferred orientation of hydroxyapatite (HA) crystal along c axis and the transformation from amorphous calcium phosphate to hierarchical HA. The incorporation of glycine had promoted the formation of the well-evolved needle-like HA crystals in comparison with aspartic acid or arginine. It was suggested that the addition of amino acids into SBF might be a useful tool to regulate the biomineralizaiton for preparing organic-inorganic composite nanofibers.
[Show abstract][Hide abstract] ABSTRACT: In this study, thermo-sensitive poly(N-isopropylacrylamide) (PNIPAAm) was grafted onto gelatin via atom transfer radical polymerization (ATRP). The chemical structure of PNIPAAm-grafted gelatin (Gel-PNIPAAm) was confirmed by XPS, ATR-IR and 1H NMR characterizations. Gel-PNIPAAm aqueous solution exhibited sol-to-gel transformation at physiological temperature, and was studied as injectable hydrogel for bone defect regeneration in a cranial model. The hydrogel was biocompatible and demonstrated the ability to enhance bone regeneration in comparison with the untreated group (control). With the incor-poration of rat bone mesenchymal stem cells (BMSCs) into the hydrogel, the bone regeneration rate was further significantly enhanced. As indicated by micro-CT, histological (H&E and Masson) and immunohistochemical (osteocalcin and osteopontin) staining, at 12 weeks post-implantation, newly formed woven bone tissue was clearly detected in the hydrogel/BMSCs treated group, showing indistinguishable boundary with surrounding host bone tissues. The results suggested that the thermo-sensitive Gel-PNIPAAm hydrogel was an excellent injectable delivery vehicle of BMSCs for in vivo bone defect regeneration.
[Show abstract][Hide abstract] ABSTRACT: Core-shell polymer spheres of submicron diameter are a promising vehicle for sequential delivery of angiogenic and osteogenic growth factors to bone defect sites, to simulate the orchestrated temporal sequence of angiogenesis and osteogenesis. To achieve a homogeneous distribution pattern in the scaffold matrix and avoid fast biological clearance in vivo, attention should be paid to the particle size of the spheres, using a modified coaxial electrospraying technique, we prepared core-shell spheres about 1 μm in diameter using the polymers poly-(d,l-lactide) in the shell and poly(l-lactide-co-glycolic acid) in the core, and loaded them with VEGF and BMP-2, growth factors that stimulate angiogenesis and osteogenesis, respectively. PLGA/PDLLA controlled sequential delivery profiles, including an initial burst release of VEGF and a sustained release behavior of BMP-2 from the VEGF//BMP-2 spheres, were obtained. The VEGF and BMP-2 released from the spheres maintained their bioactivity; VEGF could enhance the proliferation of endothelial cells and BMP-2 could promote the osteogenic differentiation of bone marrow mesenchymal stem cells. Micro-computed tomography analysis showed that, among all the experimental groups, implantation of VEGF//BMP-2 spheres into rat cranial critical-sized bone defects enhanced new bone formation to the greatest extent, resulting in the largest amount of new bone volume and the largest isolated bone islands. Histological examination showed that VEGF//BMP-2 spheres also significantly increased in-growth of blood vessels with positive CD31 staining. All these findings suggest that the submicron-scale core-shell VEGF//BMP-2 spheres developed in this study are capable of yielding sequentially coupled angiogenesis and osteogenesis, implying their extensive application in bone tissue regeneration.
Chemical Engineering Journal 08/2015; 273:490-501. DOI:10.1016/j.cej.2015.03.068 · 4.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel fiber-in-tube hierarchical nanostructure of SnO2@porous carbon in carbon tubes (SnO2@PC/CTs) is creatively designed and synthesized though a carbon coating on scalable electrospun hybrid nanofibers template and a post-etching technique. This 1D nanoarchitecture consists of double carbon-buffering matrixes, i.e., the external carbon tubular shell and the internal porous carbon skeleton, which can work synergistically to address the various issues of SnO2 nanoanode operation, such as pulverization, particle aggregation, and vulnerable electrical contacts between the SnO2 nanoparticles and the carbon conductors. Thus, the as-obtained SnO2@PC/CTs nanohybrids used as a lithium-ion-battery anode exhibits a higher reversible capacity of 1045 mA h g−1 at 0.5 A g−1 after 300 cycles as well as a high-rate cycling stability after 1000 cycles. The enhanced performance can be attributed to the wonderful merits of the external carbon protective shell for preserving the integrity of the overall electrode, and the internal porous carbon skeleton for inhibiting the aggregation and electrical isolation of the active particles during cycling.
Particle and Particle Systems Characterization 08/2015; DOI:10.1002/ppsc.201500073 · 3.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To cure serious bone tuberculosis, a novel long-term drug delivery system was designed and prepared to satisfy the needs of both bone regeneration and antituberculous drug therapy. The antituberculous drug (rifampicin, RFP) was loaded into a porous scaffold, which composed of a new designed polylactone, poly(ε-caprolactone)-block-poly(lactic-co-glycolic acid) (b-PLGC) copolymer, and β-tricalcium phosphate (β-TCP). The releasing results demonstrated that RFP could be steadily released for as long as 12 weeks both in vitro and in vivo. Within the in vivo experimental period, the drug concentration in tissues surrounding implants was much higher than that of in blood which was still superior to the effective value to kill mycobacterium tuberculosis. MC3T3-E1 osteoblasts proliferated well in extracts and co-culture on composite scaffolds, indicating good biocompatibility and cell affinity of the scaffold. The results of rabbit radius repair experiment displayed the scaffold has good bone regeneration capacity. The RFP-loaded b-PLGC/TCP composite scaffold thus could be envisioned to be a potential and promising substrate in clinical treatment of bone tuberculosis.
[Show abstract][Hide abstract] ABSTRACT: Multi walled carbon nanotubes decorated with ferriferrous oxide nanoparticle (MWCNTs-Fe3O4) complex was used as an effective reinforcement in the polymer composites. The MWCNTs-Fe3O4 with various grafting contents of Fe3O4 nanoparticles were successfully prepared by combining in situ atom transfer radical polymerization (ATRP) and coprecipitation process, which was characterized with Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscope (TEM). The MWCNTs-Fe3O4 complex showed the strong magnetic response behavior, which could be easily aligned in an external magnetic field. The alignment state of MWCNTs-Fe3O4 complex could be modulated by adjusting the intensity of external magnetic field, grafting content of Fe3O4 nanoparticles and viscosity of the solvent. Moreover, with the addition of MWCNTs-Fe3O4, tensile strength and modulus of epoxy composites were enhanced by 12.3 and 10.9%, respectively, which was due to the reinforcing effect of the aligned MWCNTs-Fe3O4 within magnetic field.
IOP Conference Series Materials Science and Engineering 07/2015; 87(1). DOI:10.1088/1757-899X/87/1/012088
[Show abstract][Hide abstract] ABSTRACT: Bioactive glass (BG) decorated nanoporous composite carbon nanofibers (PCNF/BG) were prepared for the purpose of obtaining effective substrates for skeletal tissue regeneration. The preparation was conducted by electrospinning of polyacrylonitrile (PAN)/polymethylmethacrylate (PMMA) blends with addition of sol-gel precursors of 58s-type (mol%: 58 %SiO2-38 %CaO-4 %P2O5) BG, followed by high temperature thermal treatment. The removal of PMMA during the carbonization of PAN generated numerous slitlike nanoporous structure along CNFs, leading to a significant enhancement in specific surface area, surface roughness and pore volume, which were confirmed by characterizations of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET). PCNF/BG composites with different specific surface areas were biologically evaluated by experiments of biomineralization in simulated body fluid (SBF), in vitro MC3T3-E1 osteoblasts proliferation and osteogenic differentiation. Compared to non-porous CNF/BG, the nanoporous structure distinctively enlarged the interfacial reaction area of BG component with medium environment and thus enhanced the bioactivity of CNFs by accelerating the dissolution of BG component and providing abundant nucleation sites for hydroxyapatite depositions. The released ions displayed distinct promotion in proliferation and osteogenic differentiation of osteoblasts cells, which promoted the osteocompatibility of carbon-based materials significantly.
[Show abstract][Hide abstract] ABSTRACT: Effects of butyl glycidyl ether (BGE) activated montmorillonites (BGE-MMTs) on moisture-resistant characteristics of epoxy-based composites were evaluated. The activated MMTs were prepared by intercalating BGE into the inter-layer surfaces of octadecyl ammonium modified MMTs (O-MMTs) under ultrasonication, and in a form of liquid nano-reinforcement. It showed advantages of low viscosity, excellent dispersibility and high chemical reactivity in epoxy matrix. The enhancements in tensile and flexural properties of BGE-MMTs/epoxy composites confirmed the well dispersion of BGE-MMTs in epoxy matrix and the strong interfacial adhesion between the two components. More importantly, the well-dispersed BGE-MMTs in epoxy matrix led to significant enhancement in the moisture-barrier properties of epoxy composites. In comparison with that of neat epoxy, the moisture diffusion coefficient of BGE-MMTs/epoxy composites significantly decreased from 10.1×10-6 to 0.3×10-6 cm2/s. The enhancement in moisture-barrier properties was ascribed to the exfoliated two-dimensional lamellar structure of MMTs extending the effective penetration paths of water molecules into tortuous forms. A model concerning moisture diffusion in BGE-MMTs/epoxy composites was suggested.
[Show abstract][Hide abstract] ABSTRACT: Carbon nanomaterials (CNM), such as carbon nanotube (CNT) and graphene, are highlighted in bone regeneration because of their osteo-inductive properties. Their combinations with nanofibrous polymeric scaffolds, which mimic the morphology of natural extracellular matrix of bone, arouse keen interest in bone tissue engineering. To this end, CNM were incorporated into nanofibrous poly(L-lactic acid) (PLLA) scaffolds by thermal induced phase separation. The CNM-containing composite nanofibrous scaffolds were biologically evaluated by both in vitro co-culture of bone mesenchymal stem cells (BMSCs) and in vivo implantation. The nanofibrous structure itself demonstrated significant enhancement in cell adhesion, proliferation and oseogenic differentiation of BMSCs, and with the incorporation of CNM, the composite nanofibrous scaffolds further promoted osteogenic differentiation of BMSCs significantly. Between the two CNMs, graphene showed stronger effect in promoting osteogenic differentiation of BMSCs than CNT. The results of in vivo experiments revealed that the composite nanofibrous scaffolds had both good biocompatibility and strong ability in inducing osteogenesis. CNMs could remarkably enhance the expression of osteogenesis-related proteins as well as the formation of type I collagen. Similarly, the graphene-containing composite nanofibrous scaffolds demonstrated the strongest effect on inducing osteogenesis in vivo. These findings demonstrated that CNM-containing composite nanofibrous scaffolds were obviously more efficient in promoting osteogenesis than pure polymeric scaffolds.
Journal of Biomedical Materials Research Part A 04/2015; 103(4). DOI:10.1002/jbm.a.35283 · 3.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The development of safe and effective supramolecular polycations has attracted much attention. In this work, a series of novel cyclodextrin (CD)-based supramolecular assemblies were readily prepared via the host–guest interaction by assembling different adamantane-functionalized α-CD derivatives with multiple β-CD-cored polycations. The supramolecular assemblies were investigated in terms of their pDNA-binding capabilities, cytotoxicities, cellular internalization and gene transfection efficiencies in HEK293, HepG2 and C6 cell lines. The supramolecular polycations displayed low cytotoxicities, similar to those of the CD-cored carriers. After self-assemblies, the gene transfection efficiencies and antitumor abilities of the supramolecular carriers were significantly enhanced. The present study demonstrates that such supramolecular preparation of CD-based polycations could provide a flexible strategy for the design and development of new assemblies with high efficiency and low cytotoxicity.
[Show abstract][Hide abstract] ABSTRACT: Alignment states of one dimensional multi walled carbon nanotube containing various contents of zero dimensional ferriferrous oxide nanoparticles (MWCNT-Fe3O4) were numerically characterized. MWCNT-Fe3O4 complexes were successfully prepared via in-situ surface-initiated atom transfer radical polymerization, followed by coprecipitation process. The complexes showed strong magnetism, which endowed them the possibility to be aligned under the action of external magnetic field. The intensity of magnetic field, loading content of Fe3O4 nanoparticles and viscosity of dispersing medium, however, all had substantial effects on the alignment degree. To evaluate the alignment effectively and quantitatively, an orientation tensor description based on marking the direction of single MWCNT in a selected region of optical images was employed. The results showed that MWCNT-Fe3O4 complex containing 26 wt.% of Fe3O4 nanoparticles achieved desirable alignment in deionized water under the magnetic field at the intensity of 0.10 T. Accordingly, epoxy composites reinforced with such aligned MWCNT-Fe3O4 complexes displayed 12.3 and 10.9 % enhancement in tensile strength and modulus, as well as 8.9 and 6.1 % enhancement in flexural strength and modulus, respectively.
[Show abstract][Hide abstract] ABSTRACT: The issue of how to improve the thermoelectric figure of merit (ZT) in oxide semiconductors has been challenging for more than 20 years. In this work, we report an effective path to substantial reduction in thermal conductivity and increment in carrier concentration, and thus a remarkable enhancement in the ZT value is achieved. The ZT value of In2O3 system was enhanced 4-fold by nanostructuing (nano-grains and nano-inclusions) and point defect engineering. The introduction of point defects in In2O3 results in a glass-like thermal conductivity. The lattice thermal conductivity could be reduced by 60%, and extraordinary low lattice thermal conductivity (1.2 W m(-1) K(-1) @ 973 K) below the amorphous limit was achieved. Our work paves a path for enhancing the ZT in oxides by both the nanosturcturing and the point defect engineering for better phonon-glasses and electron-crystal (PGEC) materials.
[Show abstract][Hide abstract] ABSTRACT: Objective
The objective of this study was to prepare a novel asymmetric chitosan guided bone regeneration (GBR) membrane, which is composed of a dense layer isolating the bone defect from the invasion of surrounding connective fibrous tissue and a loose layer which can improve cell adhesion and stabilize blood clots, thus guided bone regeneration. Methods The chitosan membrane was fabricated through liquid nitrogen quencher combined with lyophilization and cross-linked by sodium tripolyphosphate (TPP). The physical properties of asymmetric chitosan membrane were measured by scanning electron microscope (SEM), fourier-transform infrared (FTIR), x-ray diffraction (XRD) and tensile test machine. MTT assay and Live/Dead cell staining for MC3T3-E1 osteoblasts cultured on the membrane were used to characterize the biocompatibility of the membrane. In animal experiments, full-thickness and critical sized skull defects were made to evaluate the effect of the membrane on bone regeneration. Results The results of this study indicate that the asymmetric chitosan membrane can be built and cross-linked by TPP to enhance the tensile strength of the membrane. In vitro experiment showed that no significant numbers of dead cells were detected on the chitosan membrane, indicating that the membrane had good biocompatibility. In animal experiments, the chitosan membrane had faster new bone formation, showing the capability to enhance bone regeneration. Conclusion The chitosan membrane prepared in this study has an asymmetric structure; its tensile strength, biodegradation and biocompatibility fulfill the requirements of guided bone regeneration. Therefore, the asymmetric chitosan membrane is a promising GBR membrane for bone regeneration. Clinical Significance Guided bone regeneration (GBR) is an effective method for healing bone defects caused by periodontitis and implantitis, in which GBR membrane is a key biomaterial.
Journal of Dentistry 12/2014; 42(12). DOI:10.1016/j.jdent.2014.08.015 · 2.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Biodegradable polyesters and polyphosphazenes are both promising biomaterials for tissue regeneration. A combination of both materials would provide additional advantages over the individual components in aspects of biocompatibility and osteocompatibility. Applications of polyester/polyphosphazene composites, however, were limited due to the severe phase separation. In this study, cross-linkable poly(glycine ethyl ester-co-hydroxyethyl methacrylate)phosphazene (PGHP) was synthesized. It was blended with poly(L-lactide) (PLLA) or poly(L-lactide-co-glycolide) (PLGA), using chloroform as a mutual solvent, and photo-crosslinked before solvent removal. The resulting PLLA (or PLGA)/PGHP composites demonstrated no significant phase separation due to the restricting function of the crosslinked PGHP polymeric network. In comparison with uncrosslinked blends, the mechanical properties of crosslinked composites were remarkably improved, which indicated their strong potential in bone regeneration applications.
[Show abstract][Hide abstract] ABSTRACT: Biodegradable polyphosphazenes were categorized as osteoinductive materials due to their phosphorus-containing feature, however, they were less supportive in cell attachment and proliferation at earlier points in comparison with biodegradable aliphatic polyesters. Therefore, mussel-inspired surface modification of poly(alanine ethyl ester -co- glycine ethyl ester)phosphazene (PAGP) was studied, intending to circumvent the above mentioned disadvantage of polyphosphazene. To this end, PAGP and poly(L-lactide) (PLLA) were electrospun into nanofibrous substrates and surface treated with dopamine aqueous solution. With the analysis of scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscope (XPS) and Fourier transform infrared spectroscope (FT-IR), the successful poly(dopamine) coating was identified on both PAGP and PLLA nanofibers. MC3T3-E1 osteoblasts were found attaching and proliferating much well on poly(dopamine) modified nanofibrous substrates in comparison with the pristine ones. Besides, the poly(dopamine) coating demonstrated high activity in promoting osteogenous differentiation. Because the phosphorus content on nanofiber surface was decreased with the poly(dopamine) coating, the poly(dopamine)-coated PAGP nanofibrous substrate was slightly inferior to pure PAGP nanofibrous substrate in osteogenous differentiation. In a summary, the results confirmed that poly(dopamine) modified polyphosphazenes were promising scaffold materials with both high cell affinity and high osteocompatibility for bone regeneration.
Journal of Biomedical Materials Research Part A 11/2014; 102(11). DOI:10.1002/jbm.a.35065 · 3.37 Impact Factor