A magnetic X-band frequency microwave nanoabsorbent made of iron oxide/halloysite nanostructures combined with polystyrene.

A novel nanocomposite has been designed and fabricated through an in situ polymerization process, based on iron oxide nanoparticles (Fe3O4 NPs), halloysite nanotubes (HNTs), and polystyrene (PS). The prepared nanocomposite (formulated as Fe3O4/HNT-PS) has been fully characterized through various methods, and its applicability in microwave absorption was investigated by using some single-layer and bilayer pellets containing nanocomposite and resin. The efficiency of the Fe3O4/HNT-PS composite with different weight ratios and pellets with the thickness of 3.0 and 4.0 mm were examined. Vector network analysis (VNA) revealed that the microwave (12 GHz) can be noticeably absorbed by Fe3O4/HNT-60% PS particles in a bilayer structure with 4.0 mm thickness and 85% resin of the pellets, resulting in a microwave absorption value of ca. -26.9 dB. The observed bandwidth (RL < -10 dB) was about 1.27 GHz, where ca. 95% of the radiated wave is absorbed. Ultimately, due to low-cost raw materials and high performance of the presented absorbent system, the Fe3O4/HNT-PS nanocomposite and the construction of the presented bilayer system can be subjected to further investigations to test and compare with other compounds for industrialization.

Nanoscale bioconjugates: A review of the structural attributes of drug-loaded nanocarrier conjugates for selective cancer therapy.

Nanobioconjugates are nanoscale drug delivery vehicles that have been conjugated to or decorated with biologically active targeting ligands. These targeting ligands can be antibodies, peptides, aptamers, or small molecules such as vitamins or hormones. Most research studies in this field have been devoted to targeting cancer. Moreover, the nanostructures can be designed with an additional level of targeting by being designed to be stimulus-responsive or "smart" by a judicious choice of materials to be incorporated into the hybrid nanostructures. This stimulus could be an acidic pH, raised temperature, enzyme, ultrasound, redox potential, an externally applied magnetic field, or laser irradiation. In this case, the smart capability can increase the accumulation at the tumor site or the on-demand drug release, while the ligand ensures selective binding to the tumor cells. The present review highlights some interesting studies classified according to the nanostructure material. These materials include natural substances (polysaccharides), multi-walled carbon nanotubes (and halloysite nanotubes), metal-organic frameworks and covalent-organic frameworks, metal nanoparticles (gold and silver), and polymeric micelles.

Experimental study on classical and metaheuristics algorithms for optimal nano-chitosan concentration selection in surface coating and food packaging.

In this study the Lagrange interpolation optimization algorithm based on two variables with respect to all experimental replicates (POA), was compared with two other heuristics methods (WOA and GOA). Modification of the apple surface by an edible nano coating solution in food packaging was used as case study. The experiment was performed as a factorial test based on completely randomized design by 100 permutations data sets. Results showed a significant difference between the three optimization methods (POA, WOA and GOA) which indicates the necessity of optimization and also efficiency of the present POA. The optimum result by POA, similar to a rose petal property, could rise 72% in surface contact angle (CA). The scanning electron microscopy (SEM) images of the derived surfaces showed almost a uniform spherical nanoparticles morphology. Remarkable advantages of this new approach are no additional material requirement, healthful, easy, inexpensive, fast and affordable technique for surface improvement.

Development of novel and green NiFe2O4/geopolymer nanocatalyst based on bentonite for synthesis of imidazole heterocycles by ultrasonic irradiations.

Geopolymers as aluminosilicate inorganic polymers and eco-friendly building materials which can be used as substrate for different kinds of composite. In this research, according to the fabrication of geopolymer based on bentonite as a substrate and embedment of NiFe2O4 nanoparticles in the construction of this polymer, the synthesis of a new magnetic nanocomposite (NiFe2O4/geopolymer) was investigated for the first time. In order to describe its chemistry and morphology features, different analyses such as Fourier transform infrared spectroscopy, field-emission scanning electron microscopy and transmission electron microscopy images, Brunauer-Emmet-Teller adsorption-desorption isotherm, X-ray diffraction pattern, energy-dispersive X-ray analysis, thermogravimetric analysis, and vibrating-sample magnetometer analysis were used. The application of this novel nanocatalyst was studied for one-pot three-component condensation reaction of substituted imidazole derivatives by accelerated ultrasonic irradiations. Compared to the other conventional catalysts which were used for the synthesis of imidazole derivatives, the green synthesis method for fabrication of this heterogeneous and magnetic nanocatalyst, its high thermal stability, being eco-friendly, noticeable efficiency and easy reusability have become privileges to be superior.

Enhanced activity of vancomycin by encapsulation in hybrid magnetic nanoparticles conjugated to a cell-penetrating peptide.

We describe a novel antibiotic delivery system based on magnetic nanoparticles (NPs) conjugated to a cell-penetrating peptide (CPP). Silica-coated iron oxide NPs were produced via a co-deposition method, and coated by a polyvinyl alcohol (PVA) polymeric network via physicochemical binding. Vancomycin (VAN) was then entrapped into this PVA network. A hexapeptide sequence Gly-Ala-Phe-Pro-His-Arg, was synthesized in the solid phase and then conjugated onto the surface of the magnetic NPs. The drug ratio incorporation into the carrier system and drug release were monitored through precise analysis. Confocal microscopy showed that the NPs could be internalized into Staphylococcus aureus and Escherichia coli bacterial cells. The antimicrobial effects of VAN were significantly enhanced by this system with a low dosage of VAN. Advantages include rapid targeted-drug delivery process, drug dose reduction, and equal effects on both Gram-positive and Gram-negative bacteria.

Cu(ii) immobilized on Fe3O4@HNTs-tetrazole (CFHT) nanocomposite: synthesis, characterization, investigation of its catalytic role for the 1,3 dipolar cycloaddition reaction, and antibacterial activity.

In the present study, Cu(ii) immobilized on an Fe3O4@HNTs-tetrazole (CFHT) nanocomposite was designed and prepared. For this, halloysite nanotubes (HNTs) as natural mesoporous substances were modified during several chemical reactions. The synthesis of the CFHT nanocomposite was investigated step by step with the required physicochemical techniques such as FT-IR, EDX, SEM, TEM, XRD, VSM, TGA and CHNS analyses. After ensuring that the nanocomposite was successfully prepared, its catalytic application in the synthesis of the 5-substituted 1H-tetrazole derivatives via multicomponent reactions (MCRs) between aromatic aldehydes, malononitrile, and sodium azide was assessed. According to the experimental results, the prepared nanocomposite exhibited excellent capability for conducting this MCR reaction. All desired products were obtained in a short reaction time (30-40 min) with high productivity (90-97%) and without a complicated workup procedure. Furthermore, the magnetic property of the synthesized heterogeneous nanocomposite empowers it to be recovered and reused in five times successive reactions without any significant reduction in reaction efficiency. Moreover, the remarkable antibacterial activity of the nanocomposite against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was evaluated by agar diffusion and plate-count methods. The zones of inhibition were around 16 and 20 mm for E. coli and S. aureus bacteria, respectively. Also, colony analysis confirms the killing of bacteria by using the CFHT nanocomposite.

Facile Peptide Bond Formation: Effective Interplay between Isothiazolone Rings and Silanol Groups at Silver/Iron Oxide Nanocomposite Surfaces.

Proportional to considerable progress in protein-drug conjugations, attention to the efficient peptide coupling reagents is being increased. Hence, in this study, a versatile heterogeneous nanoscale reagent is presented for chemical, biological, and medical purposes. A combination of silver and silica-coated iron oxide nanoparticles (Ag/Fe3O4) has been well functionalized with isothiazolone rings via a silver-modified Heck mechanism. An appropriate condition is provided for peptide bond formation through the surface interplay between silanol groups and the loaded isothiazolone rings. A logical mechanism including a series of successive covalent bonds onto the surface of Ag/Fe3O4 nanocomposites is suggested for this catalyzed peptide bond formation. Accurate comparisons have been made to obtain the optimum value of the nanocatalyst and suitable conditions. As an additional application, the biological activity of the desired product has also been investigated through antibacterial assay tests. The results showed that our desired product could also be used as an effective heterogeneous nanoscale antibacterial agent for different purposes. In this regard, all of the essential structural and practical analyses have been carried out and precisely interpreted.

A novel biocompatible core-shell magnetic nanocomposite based on cross-linked chitosan hydrogels for in vitro hyperthermia of cancer therapy.

In this work, the chemical cross-linked interaction between chitosan polymeric chains and synthetic terephthaloyl diisothiocyanate as a cross-linker was accomplished in order to fabricate three dimensional cross-linked chitosan hydrogel. This cross-linked hydrogel with considerable characteristics including high stability and homogeneity in aqueous solution (water) and high porosity was applied as new substrate for generation of new magnetic terephthaloyl thiourea cross-linked chitosan nanocomposite. The features of this new magnetic nanocomposite were characterized by FT-IR, EDX, FE-SEM, TEM and VSM analysis. The Size distribution of nanoparticles according to the size histogram of FE-SEM images was estimated between 30 and 40 nm. The performance of designed magnetic nanocomposite was evaluated by magnetic fluid hyperthermia procedure. Under the alternating magnetic field (AMF), the specific absorption rate (66.92 w·g-1) was determined and as well, its saturation magnetization value was reported 78.43 emu·g-1.

Design and preparation of Fe3O4@PVA polymeric magnetic nanocomposite film and surface coating by sulfonic acid via in situ methods and evaluation of its catalytic performance in the synthesis of dihydropyrimidines.

For the first time, the design and preparation of magnetic polyvinyl alcohol (Fe3O4@PVA) nanocomposite film as a novel nanocatalyst was accomplished by in situ precipitation method. To enhance the catalysis activity, the surface modification of this nanocomposite was carried out by sulfonic acid. After the synthesis of this nanocomposite film, Fourier-transform infrared (FT-IR) spectroscopy, energy-dispersive X-ray (EDX) analysis, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) images, X-ray diffraction (XRD) pattern, N2 adsorption-desorption by Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM) were utilized to confirm the structure of the nanocomposite. The catalytic activity of Fe3O4@PVA was investigated by the synthesis of dihydropyrimidine derivatives from an aldehyde, ß-ketoester and urea or thiourea. This heterogeneous nanocatalyst can be easily separated by an external magnet and reused for several times without any significant loss of activity. Simple work-up, mild reaction conditions and easily recoverable catalyst are the advantageous of this nanocomposite film.

Mesoporous halloysite nanotubes modified by CuFe2O4 spinel ferrite nanoparticles and study of its application as a novel and efficient heterogeneous catalyst in the synthesis of pyrazolopyridine derivatives.

In this study, mesoporous halloysite nanotubes (HNTs) were modified by CuFe2O4 nanoparticles for the first time. The morphology, porosity and chemistry of the CuFe2O4@HNTs nanocomposite were fully characterized by Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM) image, transmission electron microscope (TEM) images, energy-dispersive X-ray (EDX), X-ray diffraction (XRD) pattern, Brunauer-Emmett-Teller (BET) adsorption-desorption isotherm, thermogravimetric (TG) and vibrating sample magnetometer (VSM) curve analyses. The results confirmed that CuFe2O4 with tetragonal structure, uniform distribution, and less agglomeration was located at HNTs. CuFe2O4@HNTs nanocomposite special features were high thermal stability, crystalline structure, and respectable magnetic property. SEM and TEM results showed the nanotube structure and confirmed the stability of basic tube in the synthetic process. Also, inner diameters of tubes were increased in calcination temperature at 500 °C. A good magnetic property of CuFe2O4@HNTs led to use it as a heterogeneous catalyst in the synthesis of pyrazolopyridine derivatives. High efficiency, green media, mild reaction conditions and easily recovery of the nanocatalyst are some advantages of this protocol.

Magnetic guanidinylated chitosan nanobiocomposite: A green catalyst for the synthesis of 1,4-dihydropyridines.

In this study, a novel magnetic guanidinylated chitosan nanobiocomposite was synthesized and characterized by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis (CHN), thermogravimetric analysis (TGA), X-ray diffraction (XRD) pattern, energy dispersive X-ray (EDX) analysis, vibrating sample magnetometer (VSM) curves, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. SEM and TEM images of the nanobiocomposite showed its nearly spherical shape and uniform size distribution with an average size of about 42 nm. In the current protocol, the amino functional groups on the surface of chitosan were increased due to successfully modification of chitosan via simply conversion of amino groups to guanidine. Therefore, due to the highly amount of amino functional groups and magnetic properties of the synthesized nanobiocomposite, it was successfully utilized as a heterogeneous catalyst for the one-pot multicomponent synthesis of 1,4-dihydropyridines. These products are important class of N-heterocyclic and biologically-active compounds. Many of these reported synthesis methods for these nucleuses require expensive reagents, organic solvents, long reaction time and tedious work-up methods. Noteworthy, the advantages of this method are easy separation and reusability of catalyst, high-to-excellent yields of products, use of a green solvent, mild reaction conditions and simple and chromatography free work-up procedure.