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The major objective of this study was to explore the effects of silicon dioxide (SiO2) nanofibers on the performance of 2, 2-bis-[4-(methacryloxypropoxy)-phenyl]-propane (Bis-GMA)/tri-(ethyleneglycol) dimethacrylate (TEGDMA) dental composites. At first, the mechanical properties of Bis-GMA/TEGDMA (50/50, w/w) resins containing different contents of SiO2 nanofibers were evaluated to identify the appropriate composition to achieve the significant reinforcing effect. Secondly, optimized contents (5 or 10wt.%) of SiO2 nanofibers were mixed into resins together with SiO2 microparticles, which was 60wt.% of the resin. Controls for comparison were Bis-GMA/TEGDMA resins containing only SiO2 microparticles (60wt.%) or with additional SiO2 nanoparticles (5 or 10wt.%). Properties including abrasion, polymerization shrinkage and mechanical properties were evaluated to determine the contribution of SiO2 nanofibers. In comparison with SiO2 nanoparticles, SiO2 nanofibers improved the overall performance of Bis-GMA/TEGDMA composite resins, especially in improving abrasion resistance and decreasing polymerization shrinkage. The explanations were that one-dimensional SiO2 nanofibers were able to shield particular fillers from being abraded off, and able to form a kind of overlapped fibrous network to resist polymerization shrinkage. With these approaches, SiO2 nanofiber-containing Bis-GMA composite resins were envisioned a promising choice to achieve long-term durable restorations in clinical therapies., (Copyright © 2015. Published by Elsevier B.V.)

Proliferation and differentiation of bone-related cells are modulated by many factors such as scaffold design, growth factor, dynamic culture system, and physical simulation. Nanofibrous structure and moderate-intensity (1 mT-1 T) static magnetic field (SMF) have been identified as capable of stimulating proliferation and differentiation of osteoblasts. Herein, magnetic nanofibers were prepared by electrospinning mixture solutions of poly(L-lactide) (PLLA) and ferromagnetic Fe3O4 nanoparticles (NPs). The PLLA/Fe3O4 composite nanofibers demonstrated homogeneous dispersion of Fe3O4 NPs, and their magnetism depended on the contents of Fe3O4 NPs. SMF of 100 mT was applied in the culture of MC3T3-E1 osteoblasts on pure PLLA and PLLA/Fe3O4 composite nanofibers for the purpose of studying the effect of SMF on osteogenic differentiation of osteoblastic cells on magnetic nanofibrous scaffolds. On non-magnetic PLLA nanofibers, the application of external SMF could enhance the proliferation and osteogenic differentiation of MC3T3-E1 cells. In comparison with pure PLLA nanofibers, the incorporation of Fe3O4 NPs could also promote the proliferation and osteogenic differentiation of MC3T3-E1 cells in the absence or presence of external SMF. The marriage of magnetic nanofibers and external SMF was found most effective in accelerating every aspect of biological behaviors of MC3T3-E1 osteoblasts. The findings demonstrated that the magnetic feature of substrate and microenvironment were applicable ways in regulating osteogenesis in bone tissue engineering., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Composite nanofibers composed of polyacrylonitrile (PAN)-based carbon nanofibers and bioactive glass (BG) nanoparticles have been prepared by electrospinning and in situ sintering. Morphology observation showed that the BG nanoparticles of size 20-50 nm were uniformly distributed on the surface of composite nanofibers with 350 nm average diameter after carbonization. Biological mineralization indicated the formation of apatite-like layer on the surface of composite nanofibers, in which the composition of carbonate hydroxyapatite was proved by FTIR and XRD analysis. Cell growth dynamics according to cellular morphology, CCK-8 assay, and alkaline phosphatase activity assay exhibited better cell adhesion, proliferation, and osteogenic induction of bone marrow-derived mesenchymal stem cells cultured on the composite nanofibers, which suggested the higher bioactivity of composite nanofibers compared to pure PAN-based carbon nanofibers.

Nanotopographic cues from biomaterials exert powerful effects on the osteogenic differentiation of mesenchymal stem cells because of their niche-mimicking features. However, the biological mechanisms underlying cell lineage determination by surface nanotopography have not been clearly elucidated. Here, we explored the osteogenic behavior of human bone marrow mesenchymal stem cells (hBMSCs) on poly-l-lactide nanofibers with different orientations and monitored the dynamic changes in global gene expression triggered by topographical cues. RT-PCR analysis of osteogenic marker genes and ALP activity assays demonstrated that hBMSCs cultured on random nanofibers showed enhanced osteogenic-specific fate compared with those on aligned nanofibers. Microarray analysis demonstrated a similar temporal change in gene expression patterns between hBMSCs cultured on random nanofibers and those induced with an osteogenic supplement (OS). However, the extent of osteogenic differentiation on the fibrous scaffold was much lower than that driven by chemical OS. In-depth pathway analysis revealed that focal adhesion kinase, TGF-β, Wnt, and MAPK pathways were involved in the activation of osteogenic differentiation in hBMSCs on random nanofibers. These findings suggested that a lower extent but similar rhythm of dynamic cellular behavior was induced on random nanofibers when compared with the OS condition and that mechanotransduction could trigger nonspecific and multilevel responses in hBMSCs. This study provides insight into the regulation of osteogenesis directed by substratum surfaces.

Poly(lactide-co-glycolide) (PLGA) copolymers are the most prevalent materials for tissue engineering applications. To mimic the real microenvironment of extracellular matrix (ECM) for cell growth, nanofibrous PLGA scaffolds are preferred. PLGA5050 (in which the molar ratio of lactidyl to glycolidyl units is 50:50), which is an utterly amorphous polymer, was first reported to be made into nanofibrous networks (fiber diameter around 500 nm) using phase separation from PLGA5050/THF solutions in this study. The concentration of polymeric solution had significant effects on fiber diameter and unit length. Nonsolvent (e.g. H2O) was unnecessary to form the PLGA5050 gel, which was critical to nanofibrosis, as if the environmental temperature for gelation occurrence was low enough (-70 °C). The physical crosslinks to stabilize the PLGA5050/THF gel were believed to be GA segments along the backbone owing to their inferior solubility in THF. The addition of H2O would cause adverse effects of liquid-liquid phase separation and nanofibrosis failure owing to the hydrophilicity of glycolidyl units. Associating with the phase separation method, particle-leaching technique was applied to fabricate three-dimensional scaffolds with macroporous and nanofibrous structures. To ensure the occurrence of nanofibrosis on macropore walls, the temperature of salt particles should be best lowed to -70 °C beforehand. Accordingly, scaffolds prepared under varied parameters exhibited different nanofiber and pore morphologies, which affected the pore size, porosity, specific surface area, water contact angle and protein adsorption ability etc. The preliminary cell (MC3T3-E1) culture confirmed the cell ingrowth into the macroporous and nanofibrous PLGA5050 scaffolds in comparison with the solely nanofibrous matrixes. This kind of bi-scaled three dimensional matrixes can be superior candidate scaffolds for tissue engineering applications., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Electrospun tetracycline (Tet)-loaded poly(D,L-lactide-co-glycolide) (PLGA) nanofibers are considered to have great potential as local drug-delivery systems. This study was designed to explore the effects of the lactidyl/glycolidyl (LA/GA) unit ratio and molecular weight of PLGA on Tet entrapment efficiency and in vitro release kinetics. Three kinds of PLGA (PLGA75/25, M w = 100 000 or 50 000; PLGA50/50, M w = 50 000) were examined in this study. Electrospun nanofibers were fabricated containing 3, 5, 10 wt% Tet. The results showed that PLGA50/50 entrapped more Tet than both PLGA75/25 co-polymers, and the PLGA75/25 of M w = 100 000 entrapped the least amount of Tet, suggesting that the lower the molecular weight of PLGA was, the higher the GA content in PLGA was and the higher the resulting Tet entrapment. Tet loading played an important role in Tet release. Nanofibers with 3 and 5 wt% Tet loading exhibited a sustained release for more than 28 days, whereas 10 wt% Tet only lasted 14 days. Loading of 3 wt% Tet resulted in approx. 35% release in the initial 12 h, 5 wt% Tet released approx. 70% and 10 wt% Tet resulted in approx. 85% release. The integrity of Tet incorporated into electrospun PLGA nanofibers was identified by FT-IR spectrum examination and the bacterial inhibition test. The modified Kirby-Bauer test showed dose-dependent inhibition of Staphylococcus aureus growth by Tet, confirming Tet structural stability throughout the electrospinning procedure. MG-63 cells demonstrated good adhesion and proliferation on all PLGA/Tet fibrous membranes. These results indicate that Tet entrapment and release kinetics of PLGA/Tet composite fibrous scaffolds can be tailored by the LA/GA ratios, molecular weights and drug loadings. Tet-loaded fibrous scaffolds show great potential for local drug delivery and bone defect repair.

In recent years, interest in magnetic biomimetic scaffolds for tissue engineering has increased considerably. The aim of this study is to develop magnetic biodegradable fibrous materials with potential use in bone regeneration. Magnetic biodegradable Fe(3)O(4)/chitosan (CS)/poly vinyl alcohol (PVA) nanofibrous membranes were achieved by electrospinning with average fiber diameters ranging from 230 to 380 nm and porosity of 83.9-85.1%. The influences of polymer concentration, applied voltage and Fe(3)O(4) nanoparticles loading on the fabrication of nanofibers were investigated. The polymer concentration of 4.5 wt%, applied voltage of 20 kV and Fe(3)O(4) nanoparticles loading of lower than 5 wt% could produce homogeneous, smooth and continuous Fe(3)O(4)/CS/PVA nanofibrous membranes. X-ray diffraction (XRD) data confirmed that the crystalline structure of the Fe(3)O(4), CS and PVA were maintained during electrospinning process. Fourier transform infrared spectroscopy (FT-IR) demonstrated that the Fe(3)O(4) loading up to 5 wt% did not change the functional groups of CS/PVA greatly. Transmission electron microscopy (TEM) showed islets of Fe(3)O(4) nanoparticles evenly distributed in the fibers. Weak ferrimagnetic behaviors of membranes were revealed by vibrating sample magnetometer (VSM) test. Tensile test exhibited Young's modulus of membranes that were gradually enhanced with the increase of Fe(3)O(4) nanoparticles loading, while ultimate tensile stress and ultimate strain were slightly reduced by Fe(3)O(4) nanoparticles loading of 5%. Additionally, MG63 human osteoblast-like cells were seeded on the magnetic nanofibrous membranes to evaluate their bone biocompatibility. Cell growth dynamics according to MTT assay and scanning electron microscopy (SEM) observation exhibited good cell adhesion and proliferation, suggesting that this magnetic biodegradable Fe(3)O(4)/CS/PVA nanofibrous membranes can be one of promising biomaterials for facilitation of osteogenesis.

In this study, poly (L-lactic acid) (PLLA)/trifluoroethanol (TFE) solution was electrospun to fabricate fibrous scaffolds with different fiber orientations. Random and parallel PLLA nanofiber alignments were achieved by using a metal plate and a rolling rod as the receiver, respectively. The parallel PLLA fibrous scaffolds were further hot-stretched to obtain hyperparallel PLLA fibrous scaffolds. The PLLA fibrous scaffolds were characterized by fiber diameter, interfiber distance, fiber array angle, water contact angle, morphology and mechanical strength. The tensile strength of hyperparallel nano-fibers was approximately 5- and 14-times the parallel and random fibers, respectively. Osteoblast-like MG63 cells were cultured on the PLLA scaffolds to study the effects of fiber orientation on cell morphology, proliferation and differentiation. The cells on the randomly-oriented scaffolds showed irregular forms, while the cells exhibited shuttle-like shapes on the parallel scaffolds and had larger aspect ratios along the fiber direction of the hyperparallel scaffolds. Alkaline phosphatase (ALP) activity and collagen I (placeStateCol I) and osteocalcin (OC) deposition exhibited fiber orientation dependence. With an increase in parallelism of the fibers, there was a decrease in ALP activity and placeStateCol I and OC production. These results suggest that exploitation of PLLA fiber orientation may be used to control osteoblast-like cell responses., (Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.)

Objectives: The polyacrylonitrile (PAN)-poly(methyl methacrylate) (PMMA) core-shell nanofiber reinforced dental composites have been investigated for their excellent interface adhesive, and this kind of novel dental composite has the potential for clinical uses such as denture base resin and crown-bridge material. The first objective of this work was to determine the improving effect of tensile properties by post-drawing PAN-PMMA nanofibers membrane. The second objective was to examine the flexural strength (Fs), flexural modulus (Ey) and work of fracture (WOF) of Bis-GMA/TEGDMA composites reinforced with PAN-PMMA nanofibers., Methods: PAN(core)-PMMA(shell) nanofiber was made by an electrospinning setup with a high-speed rotating rod-like collector. The post-draw process was carried out at 120 degrees C for 5 min, and all the nanofiber membranes were elongated to the desired elongation ratio (30%, 60% or 100%). Tensile properties and flexural properties of both nanofiber membranes and nanofiber reinforced Bis-GMA/TEGDMA composites were investigated. A scanning electron microscope (SEM) was used to observe the fiber morphology and the fracture surface of the composite. A dynamic mechanical thermal analyzer (DMTA) was employed to determine the dynamic mechanical properties such as tandelta and E'., Results: The post-drawing treatment significantly improved the tensile properties and fiber parallelism of nanofiber membranes. The addition of PAN-PMMA nanofibers into Bis-GMA/TEGDMA clearly showed the reinforcement effect; the flexural strength (Fs), flexural modulus (Ey) and work of fracture (WOF) kept rising with the nanofiber mass fraction changing from 0%, 0.6%, 0.8%, 1.0% to 1.2%. The flexural properties of composites reinforced with post-drawn nanofiber were further increased in comparison with those of untreated nanofiber reinforced ones. Also, the SEM observations of the fracture surface of the composites demonstrated good interfacial adhesion between fibers and resin., Significance: The post-drawing treatment was confirmed as a useful method for significantly increasing the tensile strength (673.4%) and tensile modulus (875.3%) of nanofiber membranes. In addition, the composites reinforced with post-drawn PAN-PMMA nanofibers exhibited higher Fs (13.6%), Ey (5.3%) and WOF (30.4%) than those reinforced with as-electrospun PAN-PMMA nanofibers. When 1.2% mass fraction of post-drawn nanofibers were added to Bis-GMA/TEGDMA resin, the Fs, Ey and WOF increased by 51.6%, 64.3% and 152.0%, respectively, compared with neat resin., (Copyright 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

Calcium phosphate- (CaP-) based composite scaffolds have been used extensively for the bone regeneration in bone tissue engineering. Previously, we developed a biomimetic composite nanofibrous membrane of gelatin/β-tricalcium phosphate (TCP) and confirmed their biological activity in vitro and bone regeneration in vivo. However, how these composite nanofibers promote the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is unknown. Here, gelatin/β-TCP composite nanofibers were fabricated by incorporating 20 wt% β-TCP nanoparticles into electrospun gelatin nanofibers. Electron microscopy showed that the composite β-TCP nanofibers had a nonwoven structure with a porous network and a rough surface. Spectral analyses confirmed the presence and chemical stability of the β-TCP and gelatin components. Compared with pure gelatin nanofibers, gelatin/β-TCP composite nanofibers caused increased cell attachment, proliferation, alkaline phosphatase activity, and osteogenic gene expression in rat BMSCs. Interestingly, the expression level of the calcium-sensing receptor (CaSR) was significantly higher on the composite nanofibrous scaffolds than on pure gelatin. For rat calvarial critical sized defects, more extensive osteogenesis and neovascularization occurred in the composite scaffolds group compared with the gelatin group. Thus, gelatin/β-TCP composite scaffolds promote osteogenic differentiation of BMSCs in vitro and bone regeneration in vivo by activating Ca2+-sensing receptor signaling. [ABSTRACT FROM AUTHOR]

Although poly(l-lactic acid) nanofibers are known to promote osteogenic differentiation of bone marrow stromal cells, their relative hydrophobicity and surface inertia tend to hinder their biomedical application. We explored a feasible and effective technique to improve the bioactivity and biocompatibility of poly(l-lactic acid) fibers for further application in regenerative medicine. A low-temperature atmospheric plasma was used to treat poly(l-lactic acid) nanofibers for 1, 5, and 10 min, and the surface properties and dose-dependent effects on the behavior of bone marrow stromal cells were studied. Both the amino group content and surface hydrophilicity of the nanofibers increased with treatment time, whereas the spreading and proliferation of bone marrow stromal cells were greatest on nanofibers which had been treated for 5 min, followed by samples treated for 1 and 10 min. The quantitative reverse transcription–polymerase chain reaction analysis of the bone marrow stromal cells on the 5-min-treated nanofibers had the highest expression level of osteogenic marker genes including RUNX2, BMP2, ALP, COL1A1, OPN, and OCN. The nanofibers treated for 5 min also promoted the high levels of alkaline phosphatase activity. These results suggest the exertion of dose-dependent effects by atmospheric plasma treatment on the surface of poly(l-lactic acid) nanofibers, and that this treatment is a feasible and effective technique to improve biomaterial biocompatibility and promotion of osteogenic differentiation of bone marrow stromal cells. [ABSTRACT FROM AUTHOR]

Electrospun tetracycline (Tet)-loaded poly(D,L-lactide-co-glycolide) (PLGA) nanofibers are considered to have great potential as local drug-delivery systems. This study was designed to explore the effects of the lactidyl/glycolidyl (LA/GA) unit ratio and molecular weight of PLGA on Tet entrapment efficiency and in vitro release kinetics. Three kinds of PLGA (PLGA75/25, Mw = 100 000 or 50 000; PLGA50/50, Mw = 50 000) were examined in this study. Electrospun nanofibers were fabricated containing 3, 5, 10 wt% Tet. The results showed that PLGA50/50 entrapped more Tet than both PLGA75/25 co-polymers, and the PLGA75/25 of Mw = 100 000 entrapped the least amount of Tet, suggesting that the lower the molecular weight of PLGA was, the higher the GA content in PLGA was and the higher the resulting Tet entrapment. Tet loading played an important role in Tet release. Nanofibers with 3 and 5 wt% Tet loading exhibited a sustained release for more than 28 days, whereas 10 wt% Tet only lasted 14 days. Loading of 3 wt% Tet resulted in approx. 35% release in the initial 12 h, 5 wt% Tet released approx. 70% and 10 wt% Tet resulted in approx. 85% release. The integrity of Tet incorporated into electrospun PLGA nanofibers was identified by FT-IR spectrum examination and the bacterial inhibition test. The modified Kirby-Bauer test showed dose-dependent inhibition of Staphylococcus aureus growth by Tet, confirming Tet structural stability throughout the electrospinning procedure. MG-63 cells demonstrated good adhesion and proliferation on all PLGA/Tet fibrous membranes. These results indicate that Tet entrapment and release kinetics of PLGA/Tet composite fibrous scaffolds can be tailored by the LA/GA ratios, molecular weights and drug loadings. Tet-loaded fibrous scaffolds show great potential for local drug delivery and bone defect repair. [ABSTRACT FROM AUTHOR]

Abstract: A kind of core–shell nanofibers containing sodium fluoride (NaF) was produced and used as reinforcing materials for dimethacrylate-based dental restorative resins in this study. The core–shell nanofibers were prepared by coaxial-electrospinning with polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) solutions as core and shell fluids, respectively. The produced PAN–PMMA nanofibers varied in fiber diameter and the thickness of PMMA shell depending on electrospinning parameters. NaF-loaded nanofibers were obtained by incorporating NaF nanocrystals into the core fluid at two loadings (0.8 or 1.0wt.%). Embedment of NaF nanocrystals into the PAN core did not damage the core–shell structure. The addition of PAN–PMMA nanofibers into Bis-GMA/TEGDMA clearly showed the reinforcement due to the good interfacial adhesion between fibers and resin. The flexural strength (Fs) and flexural modulus (Ey) of the composites decreased slightly as the thickness of PMMA shell increasing. Sustained fluoride releases with minor initial burst release were achieved from NaF-loaded core–shell nanofibers and the corresponding composites, which was quite different from the case of embedding NaF nanocrystals into the dental resin directly. The study demonstrated that NaF-loaded PAN–PMMA core–shell nanofibers were not only able to improve the mechanical properties of restorative resin, but also able to provide sustained fluoride release to help in preventing secondary caries. [Copyright &y& Elsevier]

Abstract: Gelatin/β-TCP composite nanofibers were fabricated by incorporated different content of β-TCP nanoparticles (0, 5, 10, and 20wt.%) into electrospun gelatin nanofibers. The morphology and chemical structure of the composite nanofibers were characterized by SEM, TEM, XRD, and TGA techniques. Especially, calcium ion release behaviors from the composite nanofibers were investigated in the cell culture medium and correlated to the osteoblastic behavior of MG-63 cells. The results demonstrated that the adhesion, spreading, proliferation and the early osteogenic differentiation of osteoblast-like MG-63 cells on the composite nanofibers depended positively on the content of incorporated β-TCP nanoparticles and their dissolution behavior in the medium thereof. [Copyright &y& Elsevier]

Abstract: Carbon nanofibers decorated with β-tricalcium phosphate (β-TCP) nanoparticles (β-TCP/CNFs) have been prepared by sintering electrospun polyacrylonitrile fibers with calcium nitrate tetrahydrate as the calcium source and triethyl phosphate as the phosphorus source. Microstructure and phase composition analysis indicate that the resulting materials are composed of β-TCP nanoparticles and CNFs. And the long β-TCP/CNFs can be cut into organism-eliminable short CNFs gradually in hydrochloric acid solution due to the solubilization of β-TCP nanoparticles. The materials exhibit good biocompatibility, and have comparable effect on cell growth with pure CNFs, with their tuning ability in degradation. [Copyright &y& Elsevier]

Abstract: PAN core–PMMA shell nanofiber fabric was prepared by electrospinning of polymer blends to reinforce 2,2-bis-[4-(methacryloxypropoxy)-phenyl]-propane (Bis-GMA) a dental resin system. The core–shell structure of the PAN–PMMA nanofiber was confirmed by scanning electron microscopy (SEM) and transmission electron microscope/energy dispersive spectroscopy (TEM/EDS) observation. The flexural properties and dynamic mechanical properties of the PAN–PMMA nanofiber reinforced Bis-GMA composites were studied. Results showed that PMMA shell was partly dissolved with the Bis-GMA resin. After photopolymerization, liner PMMA chains interpenetrated and entangled with the dental resin network, which resulted in an in situ nano-interface in the shell structure. Improvement of the mechanical properties of the PAN–PMMA nanofiber reinforced Bis-GMA composites has been achieved through this nano-interface formation. [Copyright &y& Elsevier]