Porous-conductive chitosan scaffolds were fabricated by blending conductive polypyrrole (PPy) particles with chitosan solution
and employing an improved phase separation method. In vitro and in vivo degradation behaviors of these scaffolds were investigated. In the case of in vitro degradation, an enzymatic degradation system was employed and lysozyme was used as a working enzyme. Meanwhile, the degradation
products of scaffolds, glucosamine and N-acetyl-glucosamine, were also analyzed with a HPLC method. In vivo degradation of scaffolds was performed by subcutaneously implanting these scaffolds in rat for prescheduled time intervals.
In the both cases, the weight-loss of scaffolds was monitored during the whole degradation process for evaluating the degradation
of scaffolds. The changes in conductivity of scaffolds afterin vitro or in vivo degradation were also measured using a four-point technique. It was observed that the pore parameters of scaffolds themselves
could significantly influence the degradation behaviors of scaffolds but the PPy content in the scaffolds seemed not to impart
its effect to the degradation of scaffolds. Degradation dynamics of scaffolds and conductivity measurements indicated that
these scaffolds shown fairly different behaviors in their in vitro and in vivo degradation process. According to the results obtained from in vitro and in vivo degradation of scaffolds and based on some requirements of practical tissue engineering application, it was suggested that
the PPy content in the scaffold should be slightly higher than 3 wt.% but lower than 6 wt.%. 相似文献
Small interfering RNA (siRNA) is an attractive therapeutic candidate for sequencespecific gene silencing to treat incurable diseases using small molecule drugs.However,its efficient intracellular delivery has remained a challenge.Here,we have developed a highly biocompatible fluorescent carbon dot (CD),and demonstrate a functional siRNA delivery system that induces efficient gene knockdown in vitro and in vivo.We found that CD nanoparticles (NPs) enhance the cellular uptake of siRNA,via endocytosis in tumor cells,with low cytotoxicity and unexpected immune responses.Real-time study of fluorescence imaging in live cells shows that CD NPs favorably localize in cytoplasm and successfully release siRNA within 12 h.Moreover,we demonstrate that CD NP-mediated siRNA delivery significantly silences green fluorescence protein (GFP) expression and inhibits tumor growth in a breast cancer cell xenograft mouse model of tumor-specific therapy.We have developed a multi functional siRNA delivery vehicle enabling simultaneous bioimaging and efficient downregulation of gene expression,that shows excellent potential for gene therapy. 相似文献
In this study short-term in vitro and in vivo biocompatibility apects of a biodegradable polyurethane (PU) foam were evaluated. The PU consists of hard urethane segments and amorphous soft segments based on a copolyester of dl-lactide and -caprolactone. The urethane segments are of uniform length and synthesized with 1,4-butanediisocyanate. The foam has good mechanical properties and will be used for tissue regeneration applications. Degradation tests were carried out in a buffer solution for twelve weeks. Cytotoxicity was determined using extract and direct contact test methods with incubation periods varying form 24 to 72 h. The foam was implanted subcutaneously for one, four and twelve weeks and the tissue response to the material was histologically evaluated.In vitro, the mass loss was 3.4% after twelve weeks. In the cytotoxicity tests the PU caused no abnormal growth behaviour, nor morphological changes or inhibition in metabolic activity. The in vivo studies showed no toxic tissue response to the PU. Connective tissue ingrowth, accompanied by vascular ingrowth was complete at twelve weeks. In vivo degradation had started within four to twelve weeks.In conclusion, the PU shows a good in vitro and in vivo biocompatibility in these short-term experiments. 相似文献
Polyetheretherketone (PEEK) is regarded as one of the most potential candidates of biomaterials in spinal implant applications. However, as a bioinert material, PEEK plays a limited role in osteoconduction and osseointegration. In this study, recombinant human bone morphogenetic protein-2 (rhBMP-2) was immobilized onto the surface of collagen-coated PEEK in order to prepare a multi-functional material. After adsorbed onto the PEEK surface by hydrophobic interaction, collagen was cross-linked with N-(3-dimethylaminopropyl)-N′-ethyl carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). EDC/NHS system also contributed to the immobilization of rhBMP-2. Water contact angle tests, XPS and SEM clearly demonstrated the surface changes. ELISA tests quantified the amount of rhBMP-2 immobilized and the release over a period of 30 d. In vitro evaluation proved that the osteogenesis differentiation rate was higher when cells were cultured on modified PEEK discs than on regular ones. In vivo tests were conducted and positive changes of major parameters were presented. This report demonstrates that the rhBMP-2 immobilized method for PEEK modification increase bioactivity in vitro and in vivo, suggesting its practicability in orthopedic and spinal clinical applications. 相似文献
Based on the Arrhenius equation, a method to calculate the activation energy from the resistance transition is proposed for
high temperature superconductors. This method is applied to the Y-based superconductors. The activation energy is found to
be U(T,H)∼(1−T/Tc)4.8(H/H0)−3.8 of YBCO crystal, and U(T,H)∼(1−T/Tc)3.3(H/H0)−2.2 of Er doped MTG YBCO crystal, respectively. With the obtained activation energy U(T,H), the lower part of the experimental curve ρ(T,H) and its derivative can be reproduced.
相似文献
This study evaluated the surface microhardness of four glass ionomer cements and a composite resin (Fuji IX, Ketac Molar,
Vidrion R, Vitromolar and Z 250). Ten specimens of each glass ionomer cement with 8.0 mm diameter and 5.0 mm high dimensions
were made and Vicker’s microhardness measurements were taken at 1 day and 1 week after initial setting reaction. The results
were analyzed using Student’s T test and Tukey test (p < 0.05) and demonstrated that the values of microhardness increased
after 1 week, with the exception of Fuji IX. Resin composite Z250 presented the greatest values for microhardness. 相似文献
We have studied electroluminescence in n-GaSb/n-AlGaAsSb/n-GaInAsSb heterostructures with isotype heterojunctions, in which the quantum efficiency of emission is increased due to the additional production of electron-hole pairs as a result of the impact ionization that takes place near the heterointerface. The impact ionization in such heterostructures is possible due to the presence of deep wells in the energy band structure. 相似文献
Photodiodes sensitive in the wavelength ranges 1–2.5 μm and 1–4.8 μm at room temperature have been created on the basis of n-GaSb/n-GaInAsSb/p-AlGaAsSb double-junction heterostructures of two types. The broadband photosensitivity of the diode structures of both types is indicative of the complete separation of photogenerated electron-hole pairs in the staggered n-p heterojunction (n-GaInAsSb/p-AlGaAsSb). The noise characteristics of photodetectors based on the proposed diode structures have been studied. Prospects of the use of these devices in thermophotovoltaic cells for low-temperature radiation sources are considered. 相似文献
This paper describes an improved experimental facility for measuring the speed of sound in liquids with an accuracy of up
to 0.1%. Measurements of the speed of sound in liquid n-hexane, n-octane, n-decane, and n-hexadecane at temperatures of 298–433
K and pressures of 0.1–100 MPa have been made. It has been shown that in the possible comparison range the obtained values
of the speed of sound are in good agreement with the literature data.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 732–736, July–August, 2008. 相似文献
Early diagnosis remains highly important for efficient cancer treatment,and hence,there is significant interest in the development of effective imaging strategies.This work reports a new multimodal bioimaging method for accurate and rapid diagnosis of cancer cells by introducing aqueous Fe2+ and Zn2+ ions into cancer cells (i.e.,HeLa,U87,and HepG2 cancer cells).We found that the biocompatible metal ions Fe2+ and Zn2+ forced the cancer cells to spontaneously synthesize fluorescent ZnO nanoclusters and magnetic Fe3O4 nanoclusters.These clusters could then be used for multimodal cancer imaging by combining fluorescence imaging with magnetic resonance imaging and computed tomography imaging.Meanwhile,for normal cells (i.e.,L02) and tissues,neither fluorescence nor any other obvious difference could be detected between preand post-injection.This multimodal bioimaging strategy based on the in situ biosynthesized Zn&Fe oxide nanoclusters might therefore be useful for early cancer diagnosis and therapy. 相似文献
Lanthanide-based upconversion nanoparticles (UCNPs) have been widely explored in various fields, including optical imaging,
in recent years. Although earlier work has shown that UCNPs with different lanthanide (Ln3+) dopants exhibit various colors, multicolor-especially in vivo multiplexed biomedical imaging-using UCNPs has rarely been reported. In this work, we synthesize a series of UCNPs with different
emission colors and functionalize them with an amphiphilic polymer to confer water solubility. Multicolor in vivo upconversion luminescence (UCL) imaging is demonstrated by imaging subcutaneously injected UCNPs and applied in multiplexed
in vivo lymph node mapping. We also use UCNPs for multicolor cancer cell labeling and realize in vivo cell tracking by UCL imaging. Moreover, for the first time we compare the in vivo imaging sensitivity of quantum dot (QD)-based fluorescence imaging and UCNP-based UCL imaging side by side, and find the
in vivo detection limit of UCNPs to be at least one order of magnitude lower than that of QDs in our current non-optimized imaging
system. Our data suggest that, by virtue of their unique optical properties, UCNPs have great potential for use in highly-sensitive
multiplexed biomedical imaging.
相似文献
Electrospinning is a long-known polymer processing technique that has received more interest and attention in recent years
due to its versatility and potential use in the field of biomedical research. The fabrication of three-dimensional (3D) electrospun
matrices for drug delivery and tissue engineering is of particular interest. In the present study, we identified optimal conditions
to generate novel electrospun polymeric scaffolds composed of poly-d/l-lactide and poly-l-lactide in the ratio 50:50. Scanning electron microscopic analyses revealed that the generated poly(d/l-lactide-co-l-lactide) electrospun hybrid microfibers possessed a unique porous high surface area mimicking native extracellular matrix
(ECM). To assess cytocompatibility, we isolated dermal fibroblasts from human skin biopsies. After 5 days of in vitro culture,
the fibroblasts adhered, migrated and proliferated on the newly created 3D scaffolds. Our data demonstrate the applicability
of electrospun poly(d/l-lactide-co-l-lactide) scaffolds to serve as substrates for regenerative medicine applications with special focus on skin tissue engineering. 相似文献
The development of high-resolution nanosized photoacoustic contrast agents is an exciting yet challenging technological advance. Herein, antibody (breast cancer-associated antigen 1 (Brcaa1) monoclonal antibody)- and peptide (RGD)-functionalized gold nanoprisms (AuNprs) were used as a combinatorial methodology for in situ photoacoustic imaging, angiography, and localized hyperthermia using orthotopic and subcutaneous murine gastric carcinoma models. RGD-conjugated PEGylated AuNprs are available for tumor angiography, and Brcaa1 monoclonal antibody-conjugated PEGylated AuNprs are used for targeting and for in situ imaging of gastric carcinoma in orthotopic tumor models. In situ photoacoustic imaging allowed for anatomical and functional imaging at the tumor site. In vivo tumor angiography imaging showed enhancement of the photoacoustic signal in a time-dependent manner. Furthermore, photoacoustic imaging demonstrated that tumor vessels were clearly damaged after localized hyperthermia. This is the first proof-of-concept using two AuNprs probes as highly sensitive contrasts and therapeutic agents for in situ tumor detection and inhibition. These smart antibody/peptide AuNprs can be used as an efficient nanotheranostic platform for in vivo tumor detection with high sensitivity, as well as for tumor targeting therapy, which, with a single-dose injection, results in tumor size reduction and increases mice survival after localized hyperthermia treatment.
The time-dependent Ginzburg–Landau equation with thermal noise is used to calculate the Nernst signal eN, describing the Nernst effect, in type-II superconductor in the vortex-liquid regime. The Gaussian method used is an elaboration
of the Hartree–Fock method. An additional assumption often made in analytical calculations that only the lowest Landau level
significantly contributes to physical quantities of interest in the high-field limit is lifted by including all the Landau
levels. The values of eN are in good quantitative agreement with experimental data for temperature close to Tc on Bi2Sr2CaCu2O8+δ and Bi2Sr2Ca2Cu3O10+δ. 相似文献
The state of the art in the search for novel superhard and (or) incompressible materials on the basis of higher borides of
s, p, d metals has been briefly reviewed. The information has been considered about experimental and theoretical studies of the following
groups of borides: diborides of 4d, 5d heavy metals (Tc, Ru, Rh, Re, Os, and Ir), hexagonal tetraborides with the WB4-type structure, and AMB14 borides (where A, M are s, p metals) as well as of a number of related systems. 相似文献
The possibility of creating a new scheme of a laser-pumped quantum magnetometric device based on a double-beam MX magnetometer is considered. The proposed system ensures the simultaneous measurement of the modulus of the Earth’s magnetic
field vector (with an absolute accuracy of 0.02 nT) and two angles of deviation of this vector with an absolute accuracy and
sensitivity of not worse than 0.4″ (0.1 nT) at a measurement time of τ = 1 s. In contrast to the known analogous systems,
the proposed scheme does not require generating additional magnetic fields. 相似文献
Although Calcium Phosphate Cements (CPC) are highly biocompatible and osteconductive materials, its resorption rate still
remains too slow for some applications. In this work the introduction of Macroporosity in an injectable CPC is evaluated as
a way to accelerate resorption and to increase bone ingrowth. A Macroporous and a standard CPC were injected just after preparation
in a defect drilled in rabbit femur for their in vivo evaluation. The foaming agent used was Albumen, which gave up to a 75% porosity. Sodium Alginate was added to promote the
cohesion of the foamed paste after implantation. In the case of the Macroporous Cement, bone growth and neovascularisation
was observed inside the pores of the material, not only at the margins of the cement but also in some central pores. After
12 weeks of implantation, the residual material volume of the Macroporous Cement was approximately 35% of the initial value,
whereas only the outer layers of non-Macroporous CPC were resorbed, being the residual material volume close to 100%. The
higher resorption rate was due to the higher surface contact with body fluids which increased the dissolution rate, and to
the enhancement of the cellular activity 相似文献
Thermodynamic modeling of the chemical vapor deposition of boron-carbonitride-based films in the B-C-N-H-O system using mixtures of N-trimethylborazine and nitrogen is carried out for reduced pressures (13.3 and 1.33 Pa) and a wide temperature range (300–1300 K). The source of oxygen impurities in this system is a residual pressure of 0.40 Pa. The results indicate that films of various compositions can be grown. The conditions for the deposition of BCxNy films are identified. 相似文献
Semi-organic nonlinear optical material, L-lysine L-lysinium dichloride nitrate (2C6H15N2O2+_{2}^{+} · H + · NO3-_{3}^{-} · 2Cl − ) was synthesized at room temperature. Single crystals of L-LLDN were grown by slow cooling solution growth technique. The grown crystal was confirmed by powder X-ray diffraction analysis.
The crystalline perfection of the grown single crystal was characterized by high-resolution X-ray diffraction (HRXRD) studies.
The cut-off wavelength was determined by UV-vis transmission spectral analysis. The frequency doubling of the grown crystal
was confirmed by powder second harmonic generation (SHG) measurement. The refractive index and birefringence of the crystal
were determined using He–Ne laser source. Mechanical property of the crystal was determined by Vickers hardness tester. The
frequency and temperature dependence of dielectric constant (εr), dielectric loss (tan δ) and a.c. conductivity (σac) were also measured. 相似文献
A system with n independent components which works if and only if a least k of its n components work is called a k-out-of-n system. For exponentially distributed component lifetimes, we obtain point and interval estimators for the scale parameter of the component lifetime distribution of a k-out-of-n system when the system failure time is observed only. In particular, we prove that the maximum likelihood estimator (MLE) of the scale parameter based on progressively Type-II censored system lifetimes is unique. Further, we propose a fixed-point iteration procedure to compute the MLE for k-out-of-n systems data. In addition, we illustrate that the Newton–Raphson method does not converge for any initial value. Finally, exact confidence intervals for the scale parameter are constructed based on progressively Type-II censored system lifetimes. 相似文献