Functional Nanomaterials on 2D Surfaces and in 3D Nanocomposite Hydrogels for Biomedical Applications

An emerging approach to improve the physicobiochemical properties and the multifunctionality of biomaterials is to incorporate functional nanomaterials (NMs) onto 2D surfaces and into 3D hydrogel networks. This approach is starting to generate promising advanced functional materials such as self‐assembled monolayers (SAMs) and nanocomposite (NC) hydrogels of NMs with remarkable properties and tailored functionalities that are beneficial for a variety of biomedical applications, including tissue engineering, drug delivery, and developing biosensors. A wide range of NMs, such as carbon‐, metal‐, and silica‐based NMs, can be integrated into 2D and 3D biomaterial formulations due to their unique characteristics, such as magnetic properties, electrical properties, stimuli responsiveness, hydrophobicity/hydrophilicity, and chemical composition. The highly ordered nano‐ or microscale assemblies of NMs on surfaces alter the original properties of the NMs and add enhanced and/or synergetic and novel features to the final SAMs of the NM constructs. Furthermore, the incorporation of NMs into polymeric hydrogel networks reinforces the (soft) polymer matrix such that the formed NC hydrogels show extraordinary mechanical properties with superior biological properties.     

Suppression of inhomogeneities in hydrogels formed by free-radical crosslinking copolymerization

Network microstructures of poly(acrylamide) (PAAm) and poly(N,N-dimethylacrylamide) (PDMA) hydrogels were compared by static light scattering and elasticity measurements. The hydrogels were prepared by free-radical crosslinking copolymerization of the monomers acrylamide (AAm) or N,N-dimethylacrylamide (DMA) with N,N′-methylenebis(acrylamide) as a crosslinker. During the formation of PAAm gels, the reaction time dependence of the scattered light intensity exhibits a maximum at a critical reaction time, while in case of PDMA gels, both a maximum and a minimum were observed, corresponding to the chain overlap threshold and the gel point, respectively. This difference in the time-course between the two gelling systems is due to the late onset of gelation in the DMA system with respect to the critical overlap concentration. Compared to the AAm system, no significant scattered light intensity rise was observed during the crosslinking polymerization of DMA. It was shown that, regardless of the crosslinker ratio and of the initial monomer concentration, PDMA gel is much more homogeneous than the corresponding PAAm gel due to the shift of the gelation threshold to the semidilute regime of the reaction system. The results suggest that the spatial gel inhomogeneity can be controlled by varying the gel point with respect to the critical overlap concentration during the preparation of gels by free-radical mechanism.     

Evaluation of 5G Cell Types through Channel Models

Journal of Communications Technology and Electronics - 5G technology provides much better capacity, speed, and bandwidth compared to its predecessor 4.5G, due to the high frequency it offers. Owing...     

Synthesis and swelling characteristics of poly(4‐vinylpyridine) gels crosslinked by irradiation

The effect of irradiation under vacuum on thermal properties and swelling behavior on poly(4‐vinylpyridine) (P4VP) was investigated. The gel percentage in the irradiated P4VP films was determined by Soxhlet extraction. UV spectroscopy was also used to determine sol percentage, which decreased as the radiation dose increased. The changes in thermal properties, such as glass‐transition temperature (T_g), were followed by differential scanning calorimetry before and after Soxhlet extraction. The gels prepared after irradiation were characterized with respect to their swelling properties and network structures. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2609–2614, 2001     

Synthesis, spectral characterisation and antimicrobial activity of new disazo dyes derived from heterocyclic coupling components

Two series of new disazo dyes were prepared by diazotising 4,4'-diaminodiphenylsulphonamide and 4,4'-diaminodiphenylurea and coupling with 3-methyl-1-phenyl-pyrazoline-5-one, 2-methylindole, 8-hydroxyquinoline, 2-phenylindole, 1-methyl-2-phenylindole, 3-amino-1-phenyl-pyrazoline-5-one. These dyes were characterised by ultraviolet–visible, Fourier transform infrared, nuclear magnetic resonance spectroscopic techniques and elemental analysis. The spectral characterisation of the dyes was evaluated with respect to visible absorption properties in various solvents. The effects of acid and base on the visible absorption maxima of the dyes were also reported. In addition, the antimicrobial effect of the dyes was evaluated.     

Polymer grafting onto magnetite nanoparticles by “click” reaction

In this article, we described click chemistry methodology for the incorporation of biocompatible polymer chains to Magnetite nanoparticles (NPs). We used a reduction co-precipitation method to obtain Fe₃O₄ particles in aqueous solution. As a next step, magnetic NPs surface were modified by a silanization reaction with (3-bromopropyl)trimethoxysilane in order to introduce bromine groups on the particles surface which were converted to azide groups by the reaction with sodium azide. Acetylene functionalized poly(ethylene glycol) (a-PEG) and poly(ε-caprolactone) (a-PCL) were synthesized and grafted onto the surface of azide functionalized NPs via “click” reaction to obtain magnetic NPs. Success of the different functionalization processes at different stages was studied using Fourier Transform infrared spectroscopy (FTIR). The morphologies of magnetic NPs were further investigated by transmission electron microscopy (TEM). The magnetization and superparamagnetic behavior of naked Fe₃O₄ NPs and coated NPs at room temperature was investigated by the measurement of hysteresis curves using a Vibrating Sample Magnetometer (VSM).     

Effects of microwave irradiation and chemical fixation on the localization of perisinusoidal cells in rat liver by gold impregnation

Modified gold impregnation is one of the methods that are used in light microscopical demonstration of hepatic perisinusoidal cells. This method has some disadvantages, such as restriction of fixation time to 16 h, which allows limited time for processing the tissues, especially when dealing with a large amount of material, and a long impregnation time (16–24 h). We investigated the effect of prolonged fixation on the staining of sections, to shorten the time needed for gold impregnation by using microwave irradiation. Liver specimens were fixed in Baker's calcium–formalin for different periods of time. After fixation, frozen sections were impregnated in gold chloride solution either at room temperature or in a microwave oven. The staining quality of the sections which had been impregnated in the microwave oven for a much shorter time were equal to or even superior to the ones impregnated at room temperature. Prolonging the fixation time up to 7 days did not affect the staining results by microwave irradiation, whereas satisfactory results were not obtained from sections stained at room temperature and fixed for more than 3 days. We conclude that microwave irradiation can be used to shorten the impregnation time in gold chloride solution and the duration of fixation can be prolonged up to 3 days in the original method and up to 7 days when microwave irradiation is used during impregnation.     

X-Ray crystal structure analysis and determination of azo-enamine and hydrazone-imine tautomers of two hetarylazo indole dyes

Two hetarylazo indole dyes were analyzed by single crystal X-ray diffraction. Dye 1 , C₁₈H₁₄N₄O, crystallises in the monoclinic system, space group P2₁/c, with two independent molecules in the asymmetric unit. Dye 2 , C₂₀H₁₆N₄, also crystallises in the monoclinic system, space group P2₁/n, Z  = 4. In both compounds, there are two intramolecular C–H...N hydrogen bonds which influenced the molecular conformation between the azo group and the indole ring system and its phenyl substituent. Each of the independent molecules of dye 1 interact through the N–H...N hydrogen bond, whereas no classical intermolecular hydrogen bond was observed in dye 2 . The molecules of dye 1 and dye 2 are packed differently in both structures.