Xuliang Deng

Gelatin nanofibrous membrane fabricated by electrospinning of aqueous gelatin solution for guided tissue regeneration

The electrospinning of gelatin aqueous solution was successfully carried out by elevating the spinning temperature. The effects of spinning temperature and solution concentration were investigated on the morphology of gelatin nanofibers in the current study. To improve the stability and mechanical properties in moist state, the gelatin nanofibrous membrane was chemically crosslinked by 1-ethyl-3-dimethyl-aminopropyl carbodiimide hydrochloride and N-hydroxyl succinimide. The concentration of crosslinker was optimized by measuring the swelling degree and weight loss. Nanofibrous structure of the membrane was retained after lyophilization, although the fibers were curled and conglutinated. Tensile test revealed that the hydrated membrane becomes pliable and provides predetermined mechanical properties. Periodontal ligament cells cultured on the membrane in vitro exhibited good cell attachment, growth, and proliferation. Gelatin nanofibrous membrane can be one of promising biomaterials for the regeneration of damaged periodontal tissues.

Poly(L-lactic acid)/hydroxyapatite hybrid nanofibrous scaffolds prepared by electrospinning.

Poly(L-lactic acid)/hydroxyapatite hybrid nanofibrous scaffolds were prepared via electrospinning. The structure and morphology of the scaffolds were investigated using scanning electron microscopy, differential scanning calorimetry and Fourier transform infrared spectroscopy. The experimental results showed that the average diameter of hybrid nanofiber was similar to that of pure poly(L-lactic acid) fiber, but a new surface bonding (COO−) was formed in hybrid nanofiber which made the surface of the fiber coarse. The weight loss and water uptake of pure poly(L-lactic acid) scaffolds increased continuously and the viscosity-average molecular weight decreased in the phosphate buffer solution as time passed, while those of hybrid scaffolds were very much slowed down because the dissolving of hydroxyapatite particles acted as a physical barrier and blocked off the entry of water. The biocompatibility of the scaffold has been investigated by human osteosarcoma MG-63 cell culture on the scaffold. The preliminary results showed that cells were well adhered and proliferated better on the hybrid scaffolds than pure scaffolds.

The effect of poly (L-lactic acid) nanofiber orientation on osteogenic responses of human osteoblast-like MG63 cells

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.

Magnetic biodegradable Fe3O4/CS/PVA nanofibrous membranes for bone regeneration.

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 Youngs 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.

Post-draw PAN–PMMA nanofiber reinforced and toughened Bis-GMA dental restorative composite

OBJECTIVESnThe 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.nnnMETHODSnPAN(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.nnnRESULTSnThe 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.nnnSIGNIFICANCEnThe 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.

Rapid translocation and pharmacokinetics of hydroxylated single-walled carbon nanotubes in mice

Determining the in vivo pharmacological profiles of carbon nanotubes (CNTs) is essential for the promising biomedical applications of CNTs, such as drug delivery. Using iodine-131 tracing we studied the fundamental behavior of hydroxylated single-walled CNTs (SWNTols) shortly after they were introduced into the animal body (from 2 min to 1 h) by providing the biodistribution data and pharmacokinetic parameters. The distribution was slightly influenced by injection modes, but in any mode radioactivity was found all over the body within 2 min except brain. Liver, kidneys, stomach and lungs are the target organs with high uptake of SWNTols. The SWNTols content in several tissues, such as heart, lungs, and muscle is positively correlated with its content in the blood, showing clearly that the blood stream brings SWNTols to the whole body. This work presents the initial in vivo behavior of the water-soluble functionalized SWNTs, providing also the basic data to show opportunities and limitations for realization of the CNT-based drug vehicle.

Effects of compatibility of deproteinized antler cancellous bone with various bioactive factors on their osteogenic potential.

Combinations of calcium phosphate scaffolds and bioactive factors are promising niche-mimetic solutions for repairing large-sized bone defects. However, the importance of compatibility between scaffolds and bioactive factors on their osteogenic outcomes has been largely ignored. This study aimed to investigate the compatibility of calcinated antler cancellous bone (CACB) scaffolds with various bioactive factors including icariin (ICA), velvet antler polypeptides (VAP) or recombinant human bone morphogenetic protein-2 (rhBMP-2) as well as their combinational osteogenic potential in vitro and in vivo. Scanning electron microscopy and fourier transform infrared spectroscopy confirmed the uniform distribution and chemical stability of the reagents on CABC. In vitro release profiles showed relative steady release of ICA from ICA/CACB, burst VAP release from VAP/CACB, and minimal rhBMP-2 release from rhBMP-2/CACB composites. When compared with VAP and rhBMP-2, incorporation of ICA within CACB resulted in most increased cell attachment, proliferation, alkaline phosphatase activity, osteogenic gene expression, and mineralization of rat bone marrow mesenchymal stem cells. In rabbit mandible critical-sized defects, the most extensive osteogenesis and neovascularization were observed in the ICA/CACB group. Differences between the VAP/CACB and rhBMP-2/CACB groups were not apparent. Interestingly, low pro-inflammatory (TNF-α, IL-6) and high anti-inflammatory (IL-10) mRNA levels were observed at scaffold implantation sites which were in close association with amount of new bone formation. These findings highlight that the compatibility between scaffolds and bioactive factors should been taken into account when considering the formula of optimized bone defect repair.

Lower extent but similar rhythm of osteogenic behavior in hBMSCs cultured on nanofibrous scaffolds versus induced with osteogenic supplement.

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.

In vitro hydrolytic and enzymatic degradation of nestlike-patterned electrospun poly(D,L-lactide-co-glycolide) scaffolds

A common problem in applying electrospun biodegradable polyester matrixes as tissue-engineering scaffolds is their serious shrinkage with degradation to reduce the porosity drastically. To ameliorate this problem, a nestlike-patterned poly(D,L-lactide-co-glycolide) (PLGA) nanofibrous (∼900 nm) matrix was proposed and fabricated by electropinning. Shrinkage studies demonstrated that the dimension change of nestlike-patterned fibrous membrane was much smaller than those of nonwoven and parallel-aligned fibrous membranes. And the robust framework of the patterned matrix helped to maintain its original nestlike topographical structure during degradation. Compared to hydrolytic-degraded specimens, the PLGA nanofibrous matrixes degraded in the presence of lysozyme showed larger weight loss but slower decrease in molecular weight. Besides, porous fibers with intact surface were detected by scanning electron microscopy after 20-week hydrolysis, and fibers with pores both inside and on surface were observed after enzymatic degradation for 12 weeks. Accordingly, the former presented a bimodal gel permeation chromatography (GPC) peak, while no bi or multimodal GPC peaks were found for the latter as degradation proceeded. These results indicated that an acid autocatalytic effect still existed in the hydrolysis of PLGA nanofibrous matrix. The presence of lysozyme could only accelerate the dissolution of degradation products with low molecular weight, but have no contribution to the chain scission.

Osteoconductive effectiveness of bone graft derived from antler cancellous bone: an experimental study in the rabbit mandible defect model.

The purpose of this study was to evaluate the properties of a novel inorganic xenogenic bone substitute, calcinated antler cancellous bone (CACB). Physicochemical properties of CACB including surface morphology, phase composition, chemical bond structure, Ca/P ratio and porosity were characterized by scanning electron microscopy, X-ray diffraction spectroscopy, Fourier-transform infrared spectroscopy, inductively coupled plasma-atomic emission spectroscopy and nitrogen adsorption analysis, and were found to closely resemble calcinated human cancellous bone. The bone defect repair efficacy of CACB was evaluated in comparison with commercially available bone substitutes (Bio-Oss(®)) within rabbit mandible defects. The gross observation, micro-CT and histology analysis data demonstrated that CACB was efficacious for bone regeneration, and was comparable with Bio-Oss(®) bone substitute in inducing neovascularization and osteogenesis within the mandible defects. CACB can therefore serve as a safe, renewable, and sustainable source of bone graft material, but without the ethical issues pertaining to animal welfare.