Citric acid stabilized on the surface of magnetic nanoparticles as an efficient and recyclable catalyst for transamidation of carboxamides, phthalimide, urea and thiourea with amines under neat conditions

Economic and Accessible Portable Homemade Magnetic Hyperthermia System: Influence of the Shape, Characteristics and Type of Nanoparticles in Its Effectiveness

Currently, one of the main causes of death in the world is cancer; therefore, it is urgent to obtain a precocious diagnosis, as well as boost research and development of new potential treatments, which should be more efficient and much less invasive for the patient. Magnetic hyperthermia (MH) is an emerging cancer therapy using nanoparticles, which has proved to be effective when combined with chemotherapy, radiotherapy and/or surgery, or even by itself, depending on the type and location of the tumor's cells. This article presents the results obtained by using a previously developed economic homemade hyperthermia device with different types of magnetite nanoparticles, with sizes ranging between 12 ± 5 and 36 ± 11 nm and presenting different shapes (spherical and cubic particles). These magnetic nanoparticles (MNPs) were synthesized by three different methods (co-precipitation, solvothermal and hydrothermal processes), with their final form being naked, or possessing different kinds of covering layers (polyethylene glycol (PEG) or citric acid (CA)). The parameters used to characterize the heating by magnetic hyperthermia, namely the Specific Absorption Rate (SAR) and the intrinsic loss power (ILP), have been obtained by two different methods. Among other results, these experiments allowed for the determination of which synthesized MNPs showed the best performance concerning hyperthermia. From the results, it may be concluded that, as expected, the shape of MNPs is an important factor, as well as the time that the MNPs can remain suspended in solution (which is directly related to the concentration and covering layer of the MNPs). The MNPs that gave the best results in terms of the SAR were the cubic particles covered with PEG, while in terms of total heating the spherical particles covered with citric acid proved to be better.

Efficient and straightforward spectrophotometric analysis of 5-hydroxymethylfurfural (HMF) using citrate@Fe3O4 nanoparticles as an adsorbent

In this study, we developed a spectrophotometry method for the analysis of 5-hydroxymethylfurfuraldehyde (HMF) in pharmaceutical formulations using citrate@Fe3O4 adsorbent. As bare magnetite (Fe3O4) has certain limitations, such as aggregation and oxidation, surface modifications are commonly used to improve its properties. We successfully coated Fe3O4 with sodium citrate to create a magnetic adsorbent for isolating HMF from samples. We confirmed the successful surface coating of Fe3O4 with citrate using Fourier Transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Zeta potential, and scanning electron microscopy (SEM). The high adsorption capacity of citrate@Fe3O4 is due to the abundance of carboxyl and hydroxyl groups on the surface of the adsorbent, making it ideal for HMF extraction. The HMF concentration was then quantified using spectrophotometry. Citrate@Fe3O4 exhibited a high surface area and strong interaction with HMF. We analyzed the individual influential factors affecting the magnetic solid phase extraction (MSPE) setup. Validation parameters were also provided to confirm the reliability of the method. Under optimal parameters, the method exhibited excellent linearity in the range of 0.05-30.00 μg/ml with the lower limit of quantification (LLOQ) of 0.05 μg/ml. Relative standard deviations (RSD) values for precision were better than 10% and the method's trueness were better than 10%. Recoveries were found to be in the range of 85% to 106%, indicating excellent accuracy and reliability. We used this method to identify and measure HMF in six different dextrose pharmaceutical dosage forms as intravenous injectable solutions and three honey samples.

Direct additive-free N-formylation and N-acylation of anilines and synthesis of urea derivatives using green, efficient, and reusable deep eutectic solvent ([ChCl][ZnCl2]2)

In the current report, we introduce a simple, mild efficient and green protocol for N-formylation and N-acetylation of anilines using formamide, formic acid, and acetic acid as inexpensive, nontoxic, and easily available starting materials just with heating along stirring in [ChCl][ZnCl2]2 as a durable, reusable deep eutectic solvent (DES), which acts as a dual catalyst and solvent system to produce a wide range of formanilides and acetanilides. Also, a variety of unsymmetrical urea derivatives were synthesized by the reaction of phenyl isocyanate with a range of amine compounds using this benign DES in high to excellent yields. [ChCl][ZnCl2]2 showed good recycling and reusability up to four runs without considerable loss of its catalytic activity.

Effect of Fe3O4 Nanoparticles Modified by Citric and Oleic Acids on the Physicochemical and Magnetic Properties of Hybrid Electrospun P(VDF-TrFE) Scaffolds

This study considers a fabrication of magnetoactive scaffolds based on a copolymer of vinylidene fluoride and trifluoroethylene (P(VDF-TrFE)) and 5, 10, and 15 wt.% of magnetite (Fe₃O₄) nanoparticles modified with citric (CA) and oleic (OA) acids by solution electrospinning. The synthesized Fe₃O₄-CA and Fe₃O₄-OA nanoparticles are similar in particle size and phase composition, but differ in zeta potential values and magnetic properties. Pure P(VDF-TrFE) scaffolds as well as composites with Fe₃O₄-CA and Fe₃O₄-OA nanoparticles demonstrate beads-free 1 μm fibers. According to scanning electron (SEM) and transmission electron (TEM) microscopy, fabricated P(VDF-TrFE) scaffolds filled with CA-modified Fe₃O₄ nanoparticles have a more homogeneous distribution of magnetic filler due to both the high stabilization ability of CA molecules and the affinity of Fe₃O₄-CA nanoparticles to the solvent used and P(VDF-TrFE) functional groups. The phase composition of pure and composite scaffolds includes a predominant piezoelectric β-phase, and a γ-phase, to a lesser extent. When adding Fe₃O₄-CA and Fe₃O₄-OA nanoparticles, there was no significant decrease in the degree of crystallinity of the P(VDF-TrFE), which, on the contrary, increased up to 76% in the case of composite scaffolds loaded with 15 wt.% of the magnetic fillers. Magnetic properties, mainly saturation magnetization (M_s), are in a good agreement with the content of Fe₃O₄ nanoparticles and show, among the known magnetoactive PVDF or P(VDF-TrFE) scaffolds, the highest M_s value, equal to 10.0 emu/g in the case of P(VDF-TrFE) composite with 15 wt.% of Fe₃O₄-CA nanoparticles.

Toxicity Effects of Engineered Iron Nanoparticles (Fe3O4) on the Growth, Cell Density, and Pigment Content of Chlorella vulgaris

This study investigated the effects of Fe₃O₄ nanoparticles released from synthesized thiourea catalyst on the biological aspects of Chlorella vulgaris. Fe₃O₄ concentrations (0, 10, 100, 250, 500, 750, and 1000 mg L^-1) were used for the exposure tests. Biological parameters of C. vulgaris, including cell density, cell viability, and pigment content, were assessed. Bioconcentration and bioaccumulation factors were evaluated for contaminated microalgae. Non-carcinogenic risks were then assessed using target hazard quotient (THQ) for potential risks in human consumptions. Findings showed that C. vulgaris cell number increased from 0 to 500 mg L^-1 of Fe₃O₄ concentration. Chlorophyll a represented a time-dependent response, and greatest values were detected in 250 and 500 mg L^-1 Fe₃O₄ at 4.2 and 4 mg/g, respectively. Chlorophyll b content showed a time-related manner in exposure to Fe₃O₄ with the highest values recorded at 250 mg L^-1 after 96 h. Moreover, bioaccumulation displayed a dose-dependent response at 15,000 µg/g dw in 1000 mg L^-1, whereas the lowest concentration was in the control group at 1700 µg/g dw. The bioconcentration factor showed a concentration-relevant decrease in all iron treatments and 10 mg L^-1 of Fe₃O₄ represented the greatest BCF at 327.3611. Non-carcinogenic risks illustrated negligible hazard (THQ < 1) and the largest EDI and THQ were calculated in 1000 mg L^-1 at 7.4332E-07 (mg kg^-1 day^-1) and 1.06189E-09, respectively. Together, iron is an essential trace element for biological purposes in aquatic systems, but in exceeding concentrations could impose toxicity effects to C. vulgaris populations.

Simple rapid stabilization method through citric acid modification for magnetite nanoparticles

A highly stable and magnetized citric acid (CA)-functionalized iron oxide aqueous colloidal solution (Fe3O4@CA) was synthesized by using a simple and rapid method of one-step co-participation via a chemical reaction between Fe3+ and Fe2+ in a NaOH solution at 65 °C, followed by CA addition to functionalize the Fe3O4 surface in 25 min. The NPs were synthesized at lower temperatures and shortened time compared with conventional methods. Surface functionalization is highly suggested because bare Fe3O4 nanoparticles (Fe3O4 NPs) are frequently deficient due to their low stability and hydrophilicity. Hence, 19 nm-sized Fe3O4 NPs coated with CA (Fe3O4@CA) were synthesized, and their microstructure, morphology, and magnetic properties were characterized using X-ray diffraction, transmission electron microscopy, Zeta potential, Fourier transform infrared spectroscopy, and vibrating sample magnetometer. CA successfully modified the Fe3O4 surface to obtain a stabilized (homogeneous and well dispersed) aqueous colloidal solution. The Zeta potential value of the as-prepared Fe3O4@CA increases from - 31 to - 45 mV. These CA-functionalized NPs with high magnetic saturation (54.8 emu/g) show promising biomedical applications.