共查询到20条相似文献,搜索用时 15 毫秒
2.
3.
4.
With the aim of seeking a convenient way for integrating functional materials, a polymeric system, presenting both self-healing property and shape memory behavior, was proposed and constructed based on epoxy based shape memory polymer (ESMP) and poly (ε-caprolactone) (PCL). The synthesis principle of PCL–ESMP composite was based on phase separation phenomenon between the two ingredients. Such phase separated PCL–ESMP composite reserved melting transition of PCL and glassy transition of ESMP, respectively, which was the crucial mechanism for achieving self-healing performance and shape memory behavior. A bending-recovery experiment demonstrated that PCL–ESMP composite possessed excellent thermal-induced dual-shape memory effect. Meanwhile, single edge notched bend testing revealed that such composite exhibited desirable self-healing performance as well. This article introduced a simple contrivable concept and exhibited some experimental results of the PCL–ESMP dual-functional composite system. The promising applications are expected to more widely, such as functional composite matrix and intelligent structures. 相似文献
5.
D. Depan R.D.K. Misra 《Materials science & engineering. C, Materials for biological applications》2012,32(6):1704-1709
We describe here a transformative approach to synthesize a hybrid nanostructured drug carrier that exhibits the characteristics of controlled drug release. The synthesis of the nanohybrid architecture involved two steps. The first step involved direct crystallization of biocompatible copolymer along the long axis of the carbon nanotubes (CNTs), followed by the second step of attachment of drug molecule to the polymer via hydrogen bonding. The extraordinary inorganic–organic hybrid architecture exhibited high drug loading ability and is physically stable even under extreme conditions of acidic media and ultrasonic irradiation. The temperature and pH sensitive characteristics of the hybrid drug carrier and high drug loading ability merit its consideration as a promising carrier and utilization of the fundamental aspects used for synthesis of other promising drug carriers. The higher drug release response during the application of ultrasonic frequency is ascribed to a cavitation-type process in which the acoustic bubbles nucleate and collapse releasing the drug. Furthermore, the study underscores the potential of uniquely combining CNTs and biopolymers for drug delivery. 相似文献
6.
7.
Fabricating smart materials with supramolecular switch is an attractive research topic in recent years. In this communication, shape memory polyurethane supramolecular networks are synthesized from BINA, HDI, MDI and BDO. DSC results show that amorphous soft phase and hard phase are formed through different intermolecular hydrogen bondings at the regions of pyridine units and urethane groups in the resulted BINA containing polyurethanes (BIN-PUs). Moreover, DMA results show that the BIN-PUs have higher modulus ratio (Eg / Er > 400) and much higher maximum tanδ. These results determine that the BIN-PUs exhibit excellent shape memory effect: higher shape fixity (> 97%) and higher shape recovery (> 91.7%). 相似文献
8.
9.
10.
The objective of this study was to evaluate the effect of diluents and wax level on tablet integrity during heat treatment and dissolution for sustained-release formulations and the resultant effect on drug release. Dibasic calcium phosphate dihydrate (DCPD), microcrystalline cellulose (MCC), and lactose were evaluated for their effect on tablet integrity during drug dissolution and heat treatment in wax matrix formulations. A newly developed direct compression diluent, dibasic calcium phosphate anhydrous (DCPA), was also evaluated. Compritol® 888 ATO was used as the wax matrix material, with phenylpropanolamine hydrochloride (PPA) as a model drug. Tablets were made by direct compression and then subjected to heat treatment at 80°C for 30 min. The results showed that MCC, lactose, and DCPA could maintain tablets intact during heat treatment above the melting point of wax (70°C-75°C). However, DCPD tablets showed wax egress during the treatment. MCC tablets swelled and cracked during drug dissolution and resulted in quick release. DCPD and lactose tablets remained intact during dissolution and gave slower release than MCC tablets. DCPA tablets without heat treatment disintegrated very quickly and showed immediate release. In contrast, heat-treated DCPA tablets remained intact through the 24-hr dissolution test and only released about 80% PPA at 6 hr. In the investigation of wax level, DCPD was used as the diluent. The drug release rate decreased as the wax content increased from 15% to 81.25%. The dissolution data were best described by the Higuchi square-root-of-time model. Diluents showed various effects during heat treatment and drug dissolution. The integrity of the tablets was related to the drug release rate. Heat treatment retarded drug release if there was no wax egress. 相似文献
11.
《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1986,247(2):265-280
A discharge ion source of the FEBIAD-type is described which allows accumulation of various elements in a cooled trap and release of the stored atoms after a preselected time in a defined bunch. This bunching effect is systematically investigated for the elements CuGe, PdSb and AuBi as a function of temperature and of the trap materials graphite, zirconium, niobium, molybdenum and tantalum. The accumulation/release characteristics and the underlying adsorption/desorption mechanism are qualitatively explained in terms of the temperature and enthalpy of adsorption; the measured sequences of the elements may, with some reservation, be used to test theoretical predictions. Utilizing the differences in accumulation efficiency and release profile for neighbouring elements, a high degree of chemical selectivity may be achieved. This feature, important for mass-separation on-line, is illustrated by a test in which neutron-deficient Sn isotopes were investigated γ-spectroscopically with substantially reduced isobaric contamination of In, Cd and Ag. Additionally, the bunching itself strongly increases the peak-to-noise ratio in collinear laser spectroscopy, permitting the study of isotopes hitherto inaccessible due to low production rates. The extension of this new method to other elements and to higher release speed is outlined. 相似文献
12.
Dicalcium phosphate dihydrate (CaHPO4·2H2O), also known as brushite, is one of the important bioceramics for bone regeneration. However, fast setting of the brushite cement under physiological conditions has limited its clinical use. Furthermore, brushite cement without any additives normally has poor injectability due to the liquid–solid phase separation. In the present study, magnesium-doped β-tricalcium phosphate (Mg-β-TCP) with chemical formula of β-Ca2.96?x Mg x (PO4)2 was used to prepare injectable brushite cements with improved physicochemical properties. β-TCP containing different amounts of Mg2+ ions were reacted with monocalcium phosphate monohydrate [Ca(H2PO4)2·H2O, MCPM] in the presence of water to furnish corresponding brushite cement. The samples were characterized using X-ray diffractometry, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The effect of magnesium ions on the structural, mechanical, and setting properties of the cements is reported. Our results indicate that the presence of Mg2+ ions increases the degree of injectability, setting time, and mechanical properties of the brushite cement. The compressive strength of brushite cement was substantially increased upon incorporation of Mg2+ ions. Furthermore, the setting times of the brushite cement were significantly improved. Gentamicin sulfate, amoxicillin and ampicillin trihydrate were incorporated into the Mg-brushite cement, and their release profiles showed a sustained drug release over 14 days. Cumulative releases of 99.3, 87, and 79 % were observed for gentamicin sulfate, amoxicillin, and ampicillin trihydrate, respectively. 相似文献
13.
利用光镜、XRD、DTA、压缩试验和TEM研究了等原子比TaRu超高温形状记忆合金的显微组织、相变、压缩特性和应变恢复特性.研究发现在高温到室温的降温阶段,合金发生了β(母相)→β′(中间马氏体相)→β"(马氏体)两步相变.室温显微组织为规则排布的马氏体板条,晶格结构为单斜结构.马氏体板条内部的孪晶关系经标定为(101)I型孪晶.室温压缩过程中变体内部的马氏体板条发生再取向及粗化.β′→β逆相变提供了主要的形状记忆效应,最大可恢复应变为2%. 相似文献
14.
Novel physically crosslinked hydrogels based on N-isopropylacrylamide and 1-vinyl-2-pyrrolidinone were synthesised using photopolymerisation. The gelation behaviour of the
copolymers was investigated using modulated differential scanning calorimetry, oscillatory rheological analysis and the test
tube inversion method. A number of the samples gelled spontaneously under physiological conditions and importantly did not
undergo syneresis within the desired temperature window. Two active pharmaceutical ingredients (APIs), diclofenac sodium and
procaine hydrochloride, were entrapped within the thermogelling materials by increasing external test temperature. The temperature-triggered
gelation of the copolymer gels was used as a means of controlling the release of the APIs, and was found to retard the dissolution
rate significantly. 相似文献
15.
In order to develop high functionality of shape memory materials, the shape memory composites combined with TiNi wire and shape memory epoxy were fabricated, and the mechanical and thermomechanical properties were studied. The results showed that TiNi wire can compensate for the stiffness decrease of SMPs at elevated temperature, and the strength of interface and strength of interface matrix were important to further increase elevated temperature mechanical properties. The recovery stress of composites could be adjusted by changing the pre-strain, and the maximum recovery stress was obtained at 8% which was TiNi wire maximum recoverable strain. The addition of 1 vol% TiNi wire could increase the maximum recovery stress from 1.36 MPa to 4.04 MPa, which was almost 3 times of the matrix and at the same time maintained the rates of shape fixity and shape recovery close to 100%. 相似文献
16.
Humboldt-Fellow, on leave from Centro Atomico Bariloche, 8400 Bariloche, and CRUB, Universidad National del Comahue, Argentina. 相似文献
17.
18.
Previous studies have demonstrated that multi-walled carbon nanotubes grown out of anodized nanotubular titanium (MWNT-Ti) can be used as a sensing electrode for various biomedical applications; such sensors detected the redox reactions of certain molecules, specifically proteins deposited by osteoblasts during extracellular matrix bone formation. Since it is known that polypyrrole (PPy) can release drugs upon electrical stimulation, in this study antibiotics (penicillin/streptomycin, P/S) or an anti-inflammatory drug (dexamethasone, Dex), termed PPy[P/S] or PPy[Dex], respectively, were electrodeposited in PPy on titanium. The objective of the present study was to determine if such drugs can be released from PPy on demand and (by applying a voltage) control cellular behavior important for orthopedic applications. Results showed that PPy films possessed nanometer-scale roughness as analyzed by atomic force microscopy. X-ray photoelectron spectroscopy confirmed the presence of P/S and Dex encapsulated within the PPy films. Results from cyclic voltammetry showed that 80% of the drugs were released on demand when sweep voltages were applied for five cycles at a scan rate of 0.1 V s(-1). Furthermore, osteoblast (bone-forming cells) and fibroblast (fibrous tissue-forming cells) adhesion were determined on the PPy films. Results showed that PPy[Dex] enhanced osteoblast adhesion after 4 h of culture compared to plain Ti. PPy-Ti (with or without anionic drug doping) inhibited fibroblast adhesion compared to plain Ti. These in vitro results confirmed that electrodeposited PPy[P/S] and PPy[Dex] can release drugs on demand to potentially fight bacterial infection, reduce inflammation, promote bone growth or reduce fibroblast functions, further implicating the use of such materials as implant sensors. 相似文献
19.
Hee Young Kim Tatsuhito FukushimaPio John S. Buenconsejo Tae-hyun NamShuichi Miyazaki 《Materials Science and Engineering: A》2011,528(24):7238-7246
The effects of Ta and Sn contents on the martensitic transformation temperature, crystal structure and thermal stability of Ti-Ta-Sn alloys are investigated in order to develop novel high temperature shape memory alloys. The martensitic transformation temperature significantly decreases by aging or thermal cycling due to the formation of ω phase in the Ti-Ta binary alloys. The addition of Sn is effective for suppressing the formation of ω phase and improves stability of shape memory effect during thermal cycling. The amount of Sn content necessary for suppressing aging effect increases with decreasing Ta content. High martensitic transformation temperature with good thermal stability can be achieved by adjustment of the Ta and Sn contents. Furthermore, the addition of Sn as a substitute of Ta with keeping the transformation temperature same increases the transformation strain in the Ti-Ta-Sn alloys. A Ti-20Ta-3.5Sn alloy reveals stable shape memory effect with a martensitic transformation start temperature about 440 K and a larger recovery strain when compared with a Ti-Ta binary alloy showing similar martensitic transformation temperature. 相似文献
20.
Souza KC Ardisson JD Sousa EM 《Journal of materials science. Materials in medicine》2009,20(2):507-512
Ordered mesoporous materials like SBA-15 have a network of channels and pores with well-defined size in the nanoscale range. This particular silica matrix pore architecture makes them suitable for hosting a broad variety of compounds in very promising materials in a range of applications, including drug release magnetic carriers. In this work, magnetic nanoparticles embedded into mesoporous silica were prepared in two steps: first, magnetite was synthesized by oxidation-precipitation method, and next, the magnetic nanoparticles were coated with mesoporous silica by using nonionic block copolymer surfactants as structure-directing agents. The materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N(2) adsorption, and scanning electron microscopy (SEM). The influence of magnetic nanoparticles on drug release kinetics was studied with cisplatin, carboplatin, and atenolol under in vitro conditions in the absence and in the presence of an external magnetic field (0.25 T) by using NdFeB permanent magnet. The constant external magnetic field did not affect drug release significantly. The low-frequency alternating magnetic field had a large influence on the cisplatin release profile. 相似文献