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81.
Susan Thompson Jessica Stukel Abrar AlNiemi Rebecca Kuntz Willits 《Journal of visualized experiments : JoVE》2013,(82)
This work describes the formation of poly(ethylene glycol) (PEG) microgels via a photopolymerized precipitation reaction. Precipitation reactions offer several advantages over traditional microsphere fabrication techniques. Contrary to emulsion, suspension, and dispersion techniques, microgels formed by precipitation are of uniform shape and size, i.e. low polydispersity index, without the use of organic solvents or stabilizers. The mild conditions of the precipitation reaction, customizable properties of the microgels, and low viscosity for injections make them applicable for in vivo purposes. Unlike other fabrication techniques, microgel characteristics can be modified by changing the starting polymer molecular weight. Increasing the starting PEG molecular weight increased microgel diameter and swelling ratio. Further modifications are suggested such as encapsulating molecules during microgel crosslinking. Simple adaptations to the PEG microgel building blocks are explored for future applications of microgels as drug delivery vehicles and tissue engineering scaffolds. 相似文献
82.
Methods for culturing mammalian cells ex vivo are increasingly needed to study cell and tissue physiology and to grow replacement tissue for regenerative medicine. Two‐dimensional culture has been the paradigm for typical in vitro cell culture; however, it has been demonstrated that cells behave more natively when cultured in three‐dimensional environments. Permissive, synthetic hydrogels and promoting, natural hydrogels have become popular as three‐dimensional cell culture platforms; yet, both of these systems possess limitations. In this perspective, we discuss the use of both synthetic and natural hydrogels as scaffolds for three‐dimensional cell culture as well as synthetic hydrogels that incorporate sophisticated biochemical and mechanical cues as mimics of the native extracellular matrix. Ultimately, advances in synthetic–biologic hydrogel hybrids are needed to provide robust platforms for investigating cell physiology and fabricating tissue outside of the organism. Biotechnol. Bioeng. 2009;103: 655–663. © 2009 Wiley Periodicals, Inc. 相似文献
83.
Hydrogels that undergo deformation upon appropriate changes in pH or temperature have considerable promise as drug delivery vehicles. Drug uptake in swelling and nonswelling cylindrical hydrogels and drug release from these into a target fluid are investigated here. A mathematical model for hydrogel-solution composite, a composite of a distributed parameter system (cylindrical hydrogel) and a lumped parameter system (surrounding solution), is developed. The polymer network displacement in a swelling/deswelling hydrogel is described by a stress diffusion coupling model. The analytical solution for network displacement is used to predict solvent intake by swelling hydrogels, solvent efflux from deswelling hydrogels, and changes in pressure, porosity, and effective drug diffusivity. These in turn influence drug uptake during and after hydrogel swelling and drug release from hydrogel during and after deswelling. Numerical results illustrate benefits of hydrogel swelling for drug loading and merits of different modes of drug release. Drug uptake and drug release by temperature-responsive hydrogels are compared with those by hydrogels not subject to deformation. 相似文献
84.
Activity of norA efflux pump has been known as a resistance mechanism to antibiotics like ciprofloxacin in Staphylococcus aureus. This study was carried out to assess the effect of biosynthesized NiFe2O4@Ag nanocomposite on expression of norA gene in Staphylococcus aureus. In this experimental study, 30 clinical samples were collected from patients hospitalized at different hospitals in Guilan Province, Iran. Then, clinical isolates of S. aureus were identified by standard microbiological tests. Antimicrobial susceptibility tests of clinical and standard strains of S. aureus were done by disk diffusion method according to CLSI guideline. Fourier transform infrared spectroscopy (FT‐IR) was used to analyze the various functional groups present in the biosynthesized NiFe2O4@Ag nanocomposite. This analysis confirmed the formation of alga proteins coated on magnetite nanocomposite. X‐ray diffraction (XRD) verified the crystalline structure of NiFe2O4@Ag and the deposition of silver on the surface of NiFe2O4. Energy dispersive X‐ray mapping (EDX‐map) analysis confirmed the existence of Ag, Ni, Fe and O in the final product. Scanning electron microscopy (SEM) confirmed that the nanocomposites were spherical in shape and Transmission electron microscopy (TEM) results revealed that the NiFe2O4@Ag had the particle size about 100 nm. Antibacterial activity of NiFe2O4@Ag alone and combined with ciprofloxacin was evaluated using the disk assay method, and minimum inhibitory concentration (MIC) by broth dilution method. Afterwards, the expression of norA efflux pump gene with and without of NiFe2O4@Ag nanocomposite and ciprofloxacin was evaluated by Real‐Time PCR. Real‐Time PCR results demonstrated that the expression of norA gene in the strains exposed to both NiFe2O4@Ag nanocomposite (1/4 MIC) and ciprofloxacin (1/8 MIC) significantly reduced in comparison to untreated strains. This study reveals that, when NiFe2O4@Ag nanocomposite is combined with ciprofloxacin, the inhibitory effect of ciprofloxacin increases against growth of S. aureus. Therefore, NiFe2O4@Ag nanocomposite can be considered as an effective factor to decrease the growth of S. aureus along with ciprofloxacin. 相似文献
85.
Glucose biosensor based on the room-temperature phosphorescence of TiO2/SiO2 nanocomposite 总被引:1,自引:0,他引:1
The direct immobilization of glucose oxidase (GOD) on TiO2/SiO2 nanocomposite and its application as glucose biosensor were investigated. The room-temperature phosphorescence of TiO2/SiO2 nanocomposite can be quenched by hydrogen peroxide (H2O2). The detection of glucose may be accomplished by monitoring the formation of hydrogen peroxide which generated in the oxidation process of glucose with the catalysis of GOD. To our surprise, by using a 96-hole polyporous plate accessory of fluorescence spectrophotometer, the biosensor exhibits excellent linear response to glucose concentrations ranging from 1.0 × 10−9 to 1.0 × 10−2 M with a detection limit of 1.2 × 10−10 M. The TiO2/SiO2 nanocomposite can be used as both supporting material and signal transducer. The phosphorescence intensity and color of the biosensor change obviously and even could be observed with naked eyes by continuous addition of glucose. Based on the room-temperature phosphorescence of TiO2/SiO2 nanocomposite, a new method of solid substrate-room-temperature phosphorimetry (SS-RTP) for glucose determination is proposed. A glucose biosensor was fabricated with wide determination concentration range, low detection limit, high sensitivity, and fast response time. And the biosensor has been successfully applied to the determination of glucose in human blood serum. The coacervation of GOD enzyme and its interaction with TiO2/SiO2 nanocomposite enlarge the surface area and enhance the chemical stability of GOD. The nice biocompatibility, large surface area, good chemical stability and nontoxicity of the TiO2/SiO2 nanocomposite have made this material suitable for functioning as biosensor. 相似文献
86.
Sei Kwang Hahn Rachit Ohri Cecilia M. Giachelli 《Biotechnology and Bioprocess Engineering》2005,10(3):218-224
Surface modification of glutaraldehyde fixed bovine pericardium (GFBP) was successfully carried out with hyaluronic acid (HA)
derivatives. At first, HA was chemically modified with adipic dihydrazide (ADH) to introduce hydrazide functional group into
the carboxyl group of HA backbone. Then, GFBP was surface modified by grafting HA-ADH to the free aldehyde groups on the tissue
and the subsequent HA-ADH hydrogel coating. HA-ADH hydrogels could be prepared through selective crosslinking at low pH between
hydrazide groups of HA-ADH and crosslinkers containing succinimmidyl moieties with minimized protein denaturation. When HA-ADH
hydrogels were prepared at low pH of 4.8 in the presence of erythropoietin (EPO) as a model protein, EPO release was continued
up to 85% of total amount of loaded EPO for 4 days. To the contrary, only 30% of EPO was released from HA-ADH hydrogels prepared
at pH=7.4, which might be due to the denaturation of EPO during the crosslinking reaction. Because the carboxyl groups on
the glucuronic acid residues are recognition sites for HA degradation by hyaluronidase, the HA-ADH hydrogels degraded more
slowly than HA hydrogels prepared by the crosslinking reaction of divinyl sulfone with hydroxyl groups of HA. Following a
two-week subcutaneous implantation in osteopontin-null mice, clinically significant levels of calcification were observed
for the positive controls without any surface modification. However, the calcification of surface modified GFBP with HA-ADH
and HA-ADH hydrogels was drastically reduced by more than 85% of the positive controls. The anti-calcification effect of HA
surface modification was also confirmed by microscopic analysis of explan ted tissue after staining with Alizarin Red S for
calcium, which followed the trend as observed with calcium quantification. 相似文献
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Biomimetic Spider‐Web‐Like Composites for Enhanced Rate Capability and Cycle Life of Lithium Ion Battery Anodes
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Pallab Bhattacharya Manikantan Kota Dong Hoon Suh Kwang Chul Roh Ho Seok Park 《Liver Transplantation》2017,7(17)
It is crucial to control the structure and composition of composite anode materials to enhance the cell performance of such anode materials for lithium ion batteries. Herein, a biomimetic strategy is demonstrated for the design of high performance anode materials, inspired by the structural characteristics and working principles of sticky spider‐webs. Hierarchically porous, sticky, spider‐web‐like multiwall carbon nanotube (MWCNT) networks are prepared through a process involving ozonation, ice‐templating assembly, and thermal treatment, thereby integrating the networks with γ‐Fe2O3 particles. The spider‐web‐like MWCNT/γ‐Fe2O3 composite network not only traps the active γ‐Fe2O3 materials tightly but also provides fast charge transport through the 3D internetworked pathways and the mechanical integrity. Consequently, the composite web shows a high capacity of ≈822 mA h g?1 at 0.05 A g?1, fast rate capability with ≈72.3% retention at rates from 0.05 to 1 A g?1, and excellent cycling stability of >88% capacity retention after 310 cycles with a Coulombic efficiency >99%. These remarkable electrochemical performances are attributed to the complementarity of the 3D spider‐web‐like structure with the strong attachment of γ‐Fe2O3 particles on the sticky surface. This synthetic strategy offers an environmentally safe, simple, and cost‐effective avenue for the biomimetic design of high performance energy storage materials. 相似文献
90.
Putka CS Gehrke SH Willis M Stafford D Bryant J 《Biotechnology and bioengineering》2002,80(2):139-143
The addition of poly(ethylene glycol) and salts to clarified cell lysates of Thiosphaera pantotropha increases sorption of microbial proteins into dextran hydrogels, consistent with the thermodynamics of aqueous two-phase extraction. Addition of 12 wt% PEG-10,000 to the lysate increased total sorption of protein by the dextran gel from 5.2 mg/g dextran to 37 mg/g; addition of either 0.1 M potassium iodide or tetrabutylammonium fluoride along with PEG to the lysate increased protein sorption to more than 63 mg/g, a 12-fold increase. SDS-PAGE demonstrated that the type of salt added controls which proteins are absorbed by the gel. Previously demonstrated only with model solutions, these results suggest another approach to recovery and separation strategies for proteins produced by fermentation. 相似文献