Shape-memory polymers that contain semicrystalline domains with a melting temperature (Tm) above and a crystallization temperature (Tc) below physiological temperature as fixing elements are useful to create medical devices or implants that can be custom-shaped inside or around the body. With the goal to expand the palette of materials that exhibit such properties, a series of segmented polyurethanes (PUs) containing different crystallizable polyester segments is investigated. The nature of the polyester, its molecular weight, and the ratio of hard to soft segments are systematically varied and the effect on the mechanical, thermal, and shape-memory properties of the various PUs is studied. Poly(1,12-dodecylene dodecanoate), poly(1,6-hexylene dodecanoate), and poly(ethylene sebacate) (PES) are selected as crystallizable polyester segments. The PES-based PUs display Tc values of 25–35 °C and a Tm of 60–63 °C, and allow good shape fixing at 37 °C. 相似文献
Nanofibers are one-dimensional nanomaterial in fiber form with diameter less than 1 µm and an aspect ratio (length/diameter) larger than 100:1. Among the different types of nanoparticle-loaded nanofiber systems, nanofibers loaded with magnetic nanoparticles have gained much attention from biomedical scientists due to a synergistic effect obtained from the unique properties of both the nanofibers and magnetic nanoparticles. These magnetic nanoparticle-encapsulated or -embedded nanofiber systems can be used not only for imaging purposes but also for therapy. In this review, we focused on recent advances in nanofibers loaded with magnetic nanoparticles, their biomedical applications, and future trends in the application of these nanofibers. 相似文献
Since the last decade, electrospinning is garnering more attention in the scientific research community, industries, applications like sensing (glucose, H2O2, dopamine, ascorbic acid, uric acid, neurotransmitter, etc.), biomedical applications (wound dressing, wound healing, skin, nerve, bone tissue engineering, and drug delivery systems), water treatment, energy harvesting, and storage applications. This review paper provides a brief overview of the electrospinning method, history of the electrospinning, factors affecting the electrospun nanofibers, and their morphology with different materials and composites (metals, metal oxides, 2D material, polymers and copolymers, carbon-based materials, etc.) used in the electrospinning technique with optical spinning parameters. Moreover, this paper deliberates the application of electrospun nanofibers and fibrous mats for sensing (electrochemical, optical, fluorescence, colorimetric, mechanical, photoelectric, mass sensitive change, resistive, ultrasensitive, etc.) in most illustrative representations. In the end, the challenges, opportunities of the electrospun nanofibers, and new direction for future progress are also discussed. 相似文献
Besides a stable phase, shape-memory polymers require an additional switchable moiety. In addition to thermal transitions and supramolecular interactions, these units can also be based on covalent bonds. Herein, the use of the reversible thiol-ene reaction as reversible cross-linker for the design of shape-memory polymers is demonstrated. A facile route to polymer networks with a thiol-ene acceptor and a comonomer (butyl methacrylate or 2-ethylhexyl methacrylate) cross-linked by dithiols is introduced. The thermal and mechanical properties of the resulting polymers are characterized in detail. Hereby, the polymers feature excellent shape-memory behavior with fixity and recovery rates above 90%. This study shows that the thiol-ene cross-linker can function as both, the stable and the switchable structural moiety rendering the usage of a covalent cross-linker unnecessary. This partial reversibility can also be proven by temperature-depending Raman spectroscopy. 相似文献
Hydrogels consist of three-dimensionally crosslinked polymeric chains, are hydrophilic, have the ability to absorb other molecules in their structure and are relatively easy to obtain. However, in order to improve some of their properties, usually mechanical, or to provide them with some physical, chemical or biological characteristics, hydrogels have been synthesized combined with other synthetic or natural polymers, filled with inorganic nanoparticles, metals, and even polymeric nanoparticles, giving rise to composite hydrogels. In general, different types of hydrogels have been synthesized; however, in this review, we refer to those obtained from the thermosensitive polymer poly(N-vinylcaprolactam) (PNVCL) and we focus on the definition, properties, synthesis techniques, nanomaterials used as fillers in composites and mainly applications of PNVCL-based hydrogels in the biomedical area. This type of material has great potential in biomedical applications such as drug delivery systems, tissue engineering, as antimicrobials and in diagnostic and bioimaging. 相似文献
Zein, which accounts for around 80% of the total protein composition in corn, is a biocompatible and biodegradable substance derived from renewable sources. Although insoluble in water, its amphiphilic characteristics are utilized to generate nanoparticles, nanofibers, microparticles, and even films. Numerous recent studies have demonstrated the potential of zein as a prospective biomaterial to develop fibrous scaffolds for biomedical functions owing to its biocompatibility, fibrous formation, and encapsulating qualities. Fabrication of zein-based fibrous scaffolds for biomedical applications is achieved by a wide variety of techniques, including electrospinning, wet spinning, freeze drying, and additive manufacturing. This article overviews current advancements in manufacturing techniques for zein-based fibrous scaffolds. In addition, it summarizes the most recent biomedical applications and research activities utilizing zein-based fibrous scaffolds. Overall, zein is proposed as a potential biomaterial for the production of fibrous scaffolds that stimulate cell adhesion and proliferation in a number of exciting biomedical applications due to its biodegradability, biocompatibility, and other unique features related to its structure. 相似文献
With their high‐surface‐to‐volume ratio, nanofibers have been postulated to increase interactions between nanofibrous materials and targeted substrates, which are helpful to overcome many obstacles and enhance the efficiency in a diverse number of applications. Over the past decade, many studies have been published on the fabrication of nanofibers and their applications in various fields. In this review, novel biological, chemical, and electrical characteristics of nanofibers as well as their recent status and achievements in medicine, chemistry, and electronics are analyzed. It is found that nanofibers can induce fast regeneration of many tissues/organs in medical applications and improve the efficiency of many chemical and electronics applications.
Isotropic and anisotropic shape-memory polymer foams are prepared by supercritical carbon dioxide foaming from a multiblock copolymer (PDLCL) consisting of poly(ω-pentadecalactone) and poly(ε-caprolactone) segments. Analysis by micro-computed tomography reveals for the anisotropic PDLCL foam cells a high shape anisotropy ratio of R = 1.72 ± 0.62 with a corresponding Young's compression moduli ratio between longitudinal and transversal direction of 4.3. The experimental compression data in the linear elastic range can be well described by the anisotropic open foam model of Gibson and Ashby. A micro-morphological analysis for single pores using scanning electron microscopy images permits the correlation between the macroscopic stress-compression behavior and microscale structural changes. 相似文献
New carrier platforms have been designed for an electrospun pyridinium calixarene nanofiber for controlled drug delivery. First, 5,11,17,23-tetra-tert-butyl-25,27-bis(3-aminomethyl-pyridineamido)-26,28-dihydroxycalix[4]arene (3-AMP) scaffold was produced by electrospinning. AMP scaffold was modified by human serum albumin (HSA), folic acid (FA), and glutathione (GSH). Doxorubicin (DOX) was loaded to surfaces of the AMP, AMP-HSA, AMP-HSA-FA, and AMP-HSA-GSH nanofibers by using DOX solution in different buffers with, 2.2, 4.0, 6.0, and 7.4 pH. The release studies DOX from four different nanofibers was also done in a various amount microenviroments by changing pH values. The loading and release amount of DOX was estimated from the calibration curve drawn at 480 and 560 nm of excitation and emission wavelengths by using a fluorescence spectrophotometer. The loading studies were confirmed by Fourier transforms infrared, atomic force microscopy, transmission electron microscopy, scanning electron microscope, and energy-dispersive X-ray (EDX) analysis. 相似文献
Lactobacilli are a promising natural tool against vaginal dysbiosis and infections. However, new local delivery systems and additional knowledge about their distribution and mechanism of action would contribute to the development of effective medicine. This will be facilitated by the introduction of the techniques for effective, inexpensive, and real-time tracking of these probiotics following their release. Here, we engineered three model vaginal lactobacilli (Lactobacillus crispatus ATCC 33820, Lactobacillus gasseri ATCC 33323, and Lactobacillus jensenii ATCC 25258) and a control Lactobacillus plantarum ATCC 8014 to express fluorescent proteins with different spectral properties, including infrared fluorescent protein (IRFP), green fluorescent protein (GFP), red fluorescent protein (mCherry), and blue fluorescent protein (mTagBFP2). The expression of these fluorescent proteins differed between the Lactobacillus species and enabled quantification and discrimination between lactobacilli, with the longer wavelength fluorescent proteins showing superior resolving power. Each Lactobacillus strain was labeled with an individual fluorescent protein and incorporated into poly (ethylene oxide) nanofibers using electrospinning, as confirmed by fluorescence and scanning electron microscopy. The lactobacilli retained their fluorescence in nanofibers, as well as after nanofiber dissolution. To summarize, vaginal lactobacilli were incorporated into electrospun nanofibers to provide a potential solid vaginal delivery system, and the fluorescent proteins were introduced to distinguish between them and allow their tracking in the future probiotic-delivery studies. 相似文献
Polyvinylidene fluoride (PVDF) is a piezo‐polymer which among its crystalline phases, the β‐phase has been researched for the improvement of piezoelectric properties. In this study, to improve the β‐phase contents and thereby the piezoelectric response of the polymer, the effect of adding self‐synthesized ionic liquid surfactant (ILS) in PVDF nanofibers is studied. This material is added in different weight percentages into the PVDF solution and the nanofibers are produced by electrospinning to prepare active piezoelectric thin layers. SEM, XRD, FTIR, and piezo‐tests are employed for assessing the effect of the ILS on the enhancement of β‐phase in electrospun nanofibers and their piezoelectric performance. The results indicate ≈98.6% β‐phase formation in the sample containing 4 wt% ILS and in comparison with the pure nanofibers, the output voltage and its power density are improved 186.9% and 275%, respectively. Considering the results, it is suggested that the ILS can improve the piezoelectric response of the polymer in the fabricated structure by simple mixing in solution compared to other additives. 相似文献
Polyimides (PIs) possess excellent mechanical properties, thermal stability, and chemical resistance and can be converted to carbon materials by thermal carbonization. The preparation of carbon nanomaterials by carbonizing PI‐based nanomaterials, however, has been less studied. In this work, the fabrication of PI nanofibers is investigated using electrospinning and their transformation to carbon nanofibers. Poly(amic acid) carboxylate salts (PAASs) solutions are first electrospun to form PAAS nanofibers. After the imidization and carbonization processes, PI and carbon nanofibers can then be obtained, respectively. The Raman spectra reveal that the carbon nanofibers are partially graphitized by the carbonization process. The diameters of the PI nanofibers are observed to be smaller than those of the PAAS nanofibers because of the formation of the more densely packed structures after the imidization processes; the diameters of the carbon nanofibers remain similar to those of the PI nanofibers after the carbonization process. The thermal dissipation behaviors of the PI and carbon nanofibers are also examined. The infrared images indicate that the transfer rates of thermal energy for the carbon nanofibers are higher than those for the PI nanofibers, due to the better thermal conductivity of carbon caused by the covalent sp2 bonding between carbon atoms. 相似文献