Acid-coated Magnetic Nanoparticles Research Articles

A comprehensive study on doxorubicin-loaded aspartic acid-coated magnetic Fe3O4 nanoparticles: Synthesis, characterization and in vitro anticancer investigations

Magnetic Fe₃O₄ nanoparticles (MNPs) hold significant potential across various scientific fields due to their notable properties. For biomedical applications, MNPs must be biocompatible, stable, and possess high magnetic potential. Aspartic acid (ASP) as a coating agent not only provides biocompatibility, stability, and high magnetic potential but also offers the potential for absorbing various drugs for targeted delivery due to its carboxyl and amino functional groups. So, in this study, we synthesized ASP-coated MNPs (ASP-MNPs) through a one-step co-precipitation method and loaded doxorubicin (DOX) onto these nanoparticles to create DOX-ASP-MNPs for targeted drug delivery. Characterization of the nanoparticle confirmed the crystal structure, spherical morphology, and improved size distribution of ASP-MNPs (8.53 ± 2.56 nm) compared to uncoated MNPs (7.05 ± 1.89 nm), as analyzed by XRD, FESEM, and TEM. FT-IR and zeta potential assessments (ZP = −6.3 mV for MNPs, ZP = −31.1 mV for ASP-MNPs) verified successful ASP binding, DOX loading, and nanoparticle stability. VSM analysis indicated a slight decrease in saturation magnetism after coating (51.1 emu/g) compared to MNPs (57.4 emu/g). In vitro release studies demonstrated a higher release rate (83 %) of DOX-ASP-MNPs at pH 5.2, indicating their suitability for cancerous cells. Cytotoxicity assays on A-549 cancer cell lines showed a dose-dependent response. DAPI staining revealed that free DOX caused more DNA damage. Cellular uptake studies indicated a time-dependent uptake of DOX-ASP-MNPs, higher at 3 h compared to 1 h, though lower than free DOX uptake due to different uptake pathways. Apoptosis assays over 72 h showed similar apoptotic rates for DOX-ASP-MNPs and free DOX. These findings suggest that ASP-MNPs possess enhanced physicochemical properties and effective drug delivery capabilities, making them a promising candidate for different biomedical applications, particularly targeted cancer therapy.

Field-induced magnetorheological study towards the active magneto-viscoelastic behavior of stable MnFe2O4 magnetic nanofluid

This work presents the fine-tuned synthesis of MnFe2O4 oleic acid-coated magnetic nanoparticles (MNPs) by the chemical co-precipitation method. The X-ray photoelectron spectroscopy (XPS) was utilized to investigate the elemental composition and oxidation state of oleic acid-coated MnFe2O4 MNPs. The Fourier transform infrared spectroscopy (FTIR) spectra were used to confirm the functional groups in the oleic acid-coated MnFe2O4 magnetic nanoparticles. The spherical shape of MnFe2O4 MNPs is confirmed by Field emission scanning electron microscopy (FESEM) and High-resolution transmission electron microscopy (HRTEM) techniques. Zeta potential (ζ) measurements were performed to confirm the stability of MnFe2O4 magnetic nanofluid (MNF). Magnetic measurements (M−vs−H) reveal the saturation magnetization, Ms = 20.3 emu/g and coercivity, HC = 30 Oe, confirming the single domain superparamagnetic nature at 300 K. Field-induced shear thinning behavior of the MnFe2O4 magnetic fluid is confirmed by a power law, η = c γn + n∞ and steady-state behavior measurements. Magneto viscous effect initially increased at a low shear rate of 20 s−1 and then decreased at a higher shear rate of 100 s−1, which confirms the stability of the MnFe2O4 magnetic fluid. Also, the highest deflection angle, θ = 243 m.rad of MnFe2O4 magnetic fluid was observed at a moderate shear rate 100 s−1 and a high magnetic field of 1.2 T, while the lowest value of deflection angle, θ = 65 m.rad was observed in the absence of magnetic field. In contrast, the storage modulus (G') is greater than the loss modulus (G''), in corroboration with the viscoelastic-to-viscous behavior of MnFe2O4 magnetic fluid.

Cetuximab-Conjugated Magnetic Poly(Lactic-co-Glycolic Acid) Nanoparticles for Dual-Targeted Delivery of Irinotecan in Glioma Treatment.

A glioma is the most common malignant primary brain tumor in adults and is categorized according to its growth potential and aggressiveness. Within gliomas, grade 4 glioblastoma remains one of the most lethal malignant solid tumors, with a median survival time less than 18 months. By encapsulating CPT-11 and oleic acid-coated magnetic nanoparticles (OMNPs) in poly(lactic-co-glycolic acid) (PLGA) nanoparticles, we first prepared PLGA@OMNP@CPT-11 nanoparticles in this study. After conjugating cetuximab (CET) with PLGA@OMNP@CPT-11, spherical PLGA@OMNP@CPT-11-CET nanoparticles with 250 nm diameter, 33% drug encapsulation efficiency, and 22% drug loading efficiency were prepared in a single emulsion/evaporation step. The nanoparticles were used for dual-targeted delivery of CPT-11 to U87 primary glioblastoma cells by actively targeting the overexpressed epidermal growth factor receptor on the surface of U87 cells, as well as by magnetic targeting. The physicochemical properties of nanoparticles were characterized in detail. CET-mediated targeting promotes intracellular uptake of nanoparticles by U87 cells, which can release four times more drug at pH 5 than at pH 7.4 to facilitate drug release in endosomes after intracellular uptake. The nanovehicle PLGA@OMNP-CET is cytocompatible and hemocompatible. After loading CPT-11, PLGA@OMNP@CPT-11-CET shows the highest cytotoxicity toward U87 compared with free CPT-11 and PLGA@OMNP@CPT-11 by providing the lowest drug concentration for half-maximal cell death (IC50) and the highest rate of cell apoptosis. In orthotopic brain tumor-bearing nude mice with U87 xenografts, intravenous injection of PLGA@OMNP@ CPT-11-CET followed by guidance with a magnetic field provided the best treatment efficacy with the lowest tumor-associated signal intensity from bioluminescence imaging.

Microwave Synthesis of Poly(Acrylic) Acid-Coated Magnetic Nanoparticles as Draw Solutes in Forward Osmosis.

Polyacrylic acid (PAA)-coated magnetic nanoparticles (MNP@PAA) were synthesized and evaluated as draw solutes in the forward osmosis (FO) process. MNP@PAA were synthesized by microwave irradiation and chemical co-precipitation from aqueous solutions of Fe2+ and Fe3+ salts. The results showed that the synthesized MNPs have spherical shapes of maghemite Fe2O3 and superparamagnetic properties, which allow draw solution (DS) recovery using an external magnetic field. Synthesized MNP, coated with PAA, yielded an osmotic pressure of ~12.8 bar at a 0.7% concentration, resulting in an initial water flux of 8.1 LMH. The MNP@PAA particles were captured by an external magnetic field, rinsed in ethanol, and re-concentrated as DS in repetitive FO experiments with deionized water as a feed solution (FS). The osmotic pressure of the re-concentrated DS was 4.1 bar at a 0.35% concentration, resulting in an initial water flux of 2.1 LMH. Taken together, the results show the feasibility of using MNP@PAA particles as draw solutes.

Optimized synthesis of polyacrylic acid-coated magnetic nanoparticles for high-efficiency DNA isolation and size selection.

Solid-phase reversible immobilization (SPRI) bead technology is widely used in molecular biology for convenient DNA manipulation. However, commercial SPRI bead kits lack cost advantages and flexibility. It is, therefore, necessary to develop new and alternative cost-effective methods of on-par or better quality. Herein, an easy and cost-effective method is proposed for synthesizing polyacrylic acid-coated iron oxide nanoparticles (PAA-IONPs) through in situ polymerization at lab scale for high-efficiency nucleic acid extraction and size selection. A design of experiment (DoE) approach was used to investigate the influence of iron oxide nanoparticles (IONPs), acrylic acid (AA) monomer, and sodium dodecyl sulfate (SDS) surfactant amounts on the sizes and carboxyl group densities of PAA-IONPs. Thorough characterization by thermogravimetric analysis (TGA), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and vibrating sample magnetometry (VSM) highlights the importance of a low starting pH achieved by a high ratio of AA/IONPs, to yield the largest sizes (554 nm) and highest carboxyl group densities (2.13 mmol g-1) obtained in this study. An efficient DNA purification strategy is then presented using homemade beads-suspension buffer and optimized bead concentrations (17% PEG 8000, 2.5 M NaCl, and 3 mg mL-1 PAA-IONPs). This method shows comparable performance to the control (AMPure XP beads) for DNA recovery. An adjustable PAA-IONPs DNA purification system was also developed to be used for DNA-size selection at low DNA amounts (50-100 ng) with a high degree of resolution and recovery. In conclusion, this work offers an optimized PAA-IONPs synthesis protocol and a flexible DNA purification approach that will enable researchers to manipulate DNA under various conditions, holding the significant potential to benefit future molecular biology research and diagnostics.

Preparation of Ferrofluid from Adipic Acid Coated Magnetic Nanoparticles and Hydrophobic Deep Eutectic Solvent Used in Dispersive Micro-Solid-Phase Extraction: Application for the Pre-Concentration and Determination of Clozapine in Biological Samples.

The aim of the present study is the preparation of a novel magnetic ferrofluid (FF) based on a hydrophobic deep eutectic solvent (DES), which is used for the extraction of trace quantities of clozapine from biological samples. For this purpose, a highly stable FF was prepared through the combination of adipic acid-coated magnetic nanoparticles (MNPs) plus tetraethylammonium chloride/thymol hDES without an additional stabilizer. These solvents were synthesized by the available and less-toxic materials, which is the appropriate option to support the solvents for the preparation of FF. In this study, a water-immiscible DES acts simultaneously as a carrier and stabilizer for the MNPs. In addition, the strong interactions between clozapine and magnetic FF could increase the extraction efficiency. The fractional factorial design was used for screening the experimental parameters. Then, the effective factors were optimized using the Box-Behnken design. The optimum extraction conditions were the following: pH of the sample solution: 8, the volume of the desorption solvent: 200μL and desorption time: 5min. Moreover, the suggested method exhibited low limits of detection in the range of 2.8-3.1μgL-1. The linear range was 10.0-500.0μgL-1 for human plasma and urine samples with acceptable recoveries greater than 91.4%. In addition, the proposed method is convenient, sensitive, effective, rapid and environmentally friendly.

Determination of diflufenican and azaconazole pesticides in wastewater samples by GC-MS after preconcentration with stearic acid functionalized magnetic nanoparticles-based dispersive solid-phase extraction.

This study presents the preconcentration of diflufenican and azaconazole from domestic wastewater samples by using dispersive solid-phase extraction (dSPE) for determination by gas chromatography-mass spectrometry (GC-MS). Stearic acid-coated magnetic nanoparticles were used as adsorbents for dSPE method. In order to maximize the efficiency of the extraction process, parameters such as magnetic nanoparticle (MNP) type and amount, eluent type and volume, mixing type, and mixing period were all optimized. The linear range obtained for azaconazole and diflufenican was 7.50-500ng/mL and 7.50-750ng/mL, and their limits of detection/quantification (LOD/LOQ) were calculated as 1.3/4.3ng/mL and 1.4/4.7ng/mL, respectively. By comparing the LOD values of direct GC-MS and the developed dSPE method, azaconazole and diflufenican recorded approximately 35 and 38 folds enhancement in detection power. Recovery experiments with domestic wastewater were carried out to certify the proposed method's accuracy and applicability. By using the matrix matching calibration strategy, the good percent recovery results between 98 and 105% were obtained.

Dye Elimination by Surface-Functionalized Magnetite Nanoparticles: Kinetic and Isotherm Studies

In the present manuscript, uncoated and citric acid-coated magnetic nanoparticles were synthesized and characterized using various techniques. The manuscript mainly focuses on the adsorption study of the citric acid-modified magnetic nanoparticles for dye adsorption from the solution. The effect of several factors, including adsorbent amount, adsorption time, and dye solution concentration, were examined. Additionally, kinetic and isotherm studies confirmed that the adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model. The desorption study was also scrutinized. The coated magnetite nanoparticles show better adsorption capacity than uncoated magnetite nanoparticles.

Blend of neem oil based polyesteramide as magnetic nanofiber mat for efficient cancer therapy

Stearic acid-coated magnetic nanoparticles (SMN) and FU (5-Fluorouracil) were immobilized in the blends of neem oil-based polyesteramide and fabricated as nanofiber mat (NM) for controlled release of FU under the influence of an external magnetic field for targeted drug delivery to treat cancer efficiently. Analyzed the surface morphology of the fibers using E-SEM, it was observed that the fibers were smooth with the diameter ranging from 250 to 450 nm. TEM studies showed the uniform distribution of SMN in the nanofibers. The physicochemical properties of NM and raw materials were analyzed using FTIR, TGA, and XRD. The results suggested that the polymers were well blended. In-vitro FU release studies of the NMs recorded a significant difference in the cumulative percentage of FU release from SMN-NMs. The SMN-NMs released 95% of FU in 4 h, whereas, NMs released 83% of FU in 24 h. The cell viability assay for the NM was evaluated in the L929 mouse fibroblast cells, where ˃75% of cells were viable. The hemolysis assay for the developed SMN-NF showed ˂5% of hemolysis, which indicated the NMs were safe for application. The anti-cancer activity of FU loaded SMN-NF was analyzed in the MCF-7 cancer cell line, which recorded more than 50% cell death within 24 h. From SQUID analysis, we found that the 10% SMN were superparamagnetic in nature, the magnetization at 30 kOe was observed to be 4.3 emu/g. Based on the in vitro results, we concluded that the developed SMN-NMs are recommended for in vivo studies to understand their efficacy for the targeted drug delivery to treat cancer.

Enhancing efficacy of existing antibacterials against selected multiple drug resistant bacteria using cinnamic acid-coated magnetic iron oxide and mesoporous silica nanoparticles

ABSTRACT Developing new antibacterial drugs by using traditional ways is insufficient to meet existing challenges; hence, new strategies in the field of antibacterial discovery are necessary. An alternative strategy is to improve the efficacy of currently available antibiotics. Herein, the antibacterial efficacy of drugs (Cefixime, Sulfamethoxazole, and Moxifloxacin) and drug-loaded cinnamic acid-coated magnetic iron oxide and mesoporous silica nanoparticles (NPs) was elucidated versus Gram-negative bacteria (Pseudomonas aeruginosa, Klebsiella pneumoniae, neuropathogenic Escherichia coli K1 and Serratia marcescens) and Gram-positive bacteria (Methicillin-resistant Staphylococcus aureus (MRSA), Streptococcus pyogenes, Streptococcus pneumoniae, and Bacillus cereus). NPs were synthesized by co-precipitation and the Stöber method, and characterized by Fourier transform-infrared spectroscopy, Zetasizer, and Atomic force microscopy. Lactate dehydrogenase (LDH) assays were accomplished to determine drug cytotoxicity against human cells. Spherical NPs in the range of 118–362 nm were successfully synthesized. Antibacterial assays revealed that drugs conjugated with NPs portray enhanced bactericidal efficacies against multiple drug resistant bacteria compared to the drugs alone. Of note, Cefixime-conjugated NPs against Escherichia coli K1 and Methicillin- resistant Staphylococcus aureus, resulted in the complete eradication of all bacterial isolates tested at significantly lower concentrations compared to the antibiotics alone. Likewise, conjugation of Moxifloxacin resulted in the complete elimination of E. coli K1 and MRSA. Of note, nano-formulated drugs presented negligible cytotoxicity against human cells. These results depict potent, and enhanced efficacy of nano-formulated drugs against medically important bacteria and can be used as alternatives to current antibiotics. Future in vivo studies and clinical studies are warranted in prospective years to realize these expectations.

Development of magnetic dispersive micro-solid phase extraction based on magnetic adipic acid nanoparticles and deep eutectic solvents for the isolation and pre-concentration of phenolic compounds in fruit juice samples prior to determination by HPLC-UV

In this research, novel magnetic nanoparticles based on ultrasonic-assisted magnetic dispersive micro-solid phase extraction and deep eutectic solvent have been developed for the determination of phenolic compounds (naringenin, hesperetin, gallic acid) in fruit juice samples. For this purpose, for the first time, adipic acid-coated magnetic nanoparticles (AD@Fe3O4) as an efficient sorbent were synthesized and identified. In this study, deep eutectic solvents were prepared with available and less-toxic compounds and used as eluent solvent in the desorption step. These solvents are good options instead of conventional organic solvents to reduce hazardous waste products and improve the adsorption capacity. In addition, the extracted analytes were easily isolated from the media by an external magnet, and no special devices were required for phase separation. The screening of some important parameters on the extraction procedure was examined by fractional factorial design. Then, the central composite design was applied to optimize the effective parameters. The optimum conditions for the developed method were obtained as pH: 3.7, the amount of salt: 5% (w/v), the amount of adsorbent: 2 mg, and extraction time: 2 min. Under the optimal conditions, the proposed method demonstrated excellent linearity in the range of 1.0–500.0 µg L−1 for hesperetin and 5.0–500.0 µg L−1 for naringenin and gallic acid (R2 > 0.997). The extraction recoveries were obtained above 91.0%, and the intra-day and inter-day precision (RSD%) lower than 4.8%. Limit of detections (LODs) were in the range of 0.3–2.0 µg L−1. The results indicated that the suggested method is simple, fast, and eco-friendly. At the end, the new method was effectively applied for the determination of phenolic compounds in fruit juice samples.

Highly Porous Magnetic Janus Microparticles with Asymmetric Surface Topology.

Monodispersed magnetic Janus particles composed of a porous polystyrene portion and a nonporous poly(vinyl acetate) portion with embedded oleic acid-coated magnetic nanoparticles were generated using microfluidic emulsification followed by two distinct phase separation events triggered by solvent evaporation. The template droplets were composed of 2 wt % polystyrene, 2 wt % poly(vinyl acetate), and 0.5-2 wt % n-heptane-based magnetic fluid dissolved in dichloromethane (DCM). The porosity of polystyrene compartments was the result of phase separation between a nonvolatile nonsolvent (n-heptane) and a volatile solvent (DCM) within polystyrene-rich phase. The focused ion beam cross-sectioning and scanning electron microscopy (SEM) imaging revealed high surface porosity of polystyrene compartments with negligible porosity of poly(vinyl acetate) parts, which can be exploited to increase the wettability contrast between the two polymers and enhance bubble generation in bubble-driven micromotors. The porosity of the polystyrene portion was controlled by varying the fraction of n-heptane in the dispersed phase. The particle composition was confirmed by scanning electron microscopy-energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The fabricated particles were successfully magnetized when subjected to an external magnetic field, which led to their aggregation into regular 2D assemblies. The particle clusters composed of two to four individual particles could be rotated with a rotating magnetic field. Microfluidic generation of highly porous Janus particles with compositional, topological, and magnetic asymmetry provides a cost-effective, easy-to-implement yet highly robust and versatile strategy for the manufacturing of multifunctional smart particles.

Integrating functionalized magnetite nanoparticles with low salinity water and surfactant solution: Interfacial tension study

In this study, citric acid-coated magnetic (CACM) nanoparticles (NPs) were synthesized and utilized as an interfacial tension (IFT) reduction agent. In addition, the effect of three types of salts at different concentrations up to 150,000 ppm was investigated. These salts, NaCl, CaCl2, and MgCl2, showed the IFT values of 19.34, 16.24 and 12.23 mN/m, respectively, at the optimum salinity condition. The IFT decreased swiftly with increasing brine concentration at the beginning and then, increased after the optimum point due to the effect of asphaltenes and salts, respectively. Meanwhile, CACM NPs indicated a very significant capability to reduce the IFT value down to 3.99 mN/m without using any surfactant. The CACM NPs, among the other NPs used in this study, have shown a key role in IFT reduction due to their acidic feature (these NPs were coated by citric acid). Consequently, the combination of the NPs with surfactant at low salinity condition, showed major changes (for Fe2O3 and SiO2 NPs) and minor changes (for CACM NPs) at the interface as the movement of the surfactants by the NPs to the interface increases the surface-active agents at interface for reducing the IFT. The findings of this study can help to gain a better understanding of the IFT behavior using magnetite NPs in combination with surfactant at low salinity condition.

Ecofriendly-developed Polyacrylic Acid-coated Magnetic Nanoparticles as Catalysts in Photo-fenton Processes

In this work, iron oxide-based magnetic nanoparticles (MNPs) stabilized by polyacrylic acid (PAA) polymer were prepared and characterized as a continuation of a previous research already reported. MNPs composed by pure magnetite cores having good magnetic properties were developed, thus achieving an improvement in the modified coprecipitation method used. The photocatalytic activity of the nanoparticles towards acid orange 7 (AO7), under both radiation types, UV-Vis and LED-Vis, was tested. Pollutant degradation percentages of 64 and 37 % were obtained by using UV-Vis and LED-Vis radiation, respectively.

Thermosensitive magnetic liposomes for alternating magnetic field-inducible drug delivery in dual targeted brain tumor chemotherapy

The nonspecific distribution and non-targeted heating of chemotherapeutic agents in the human body commonly produce adverse side effects during brain cancer management. Even though an external magnetic field can partially gather extracellular magnetic drug carriers near brain tumor, magnetic guidance alone still cannot precisely identify and target either tumors or healthy tissues due to a lack of selectivity. In this study, we successfully developed thermal and magnetic dual-responsive thermosensitive magnetic liposomes (TML), which co-encapsulates Camptosar (CPT-11) and citric acid-coated magnetic Fe3O4 nanoparticles within the aqueous core and surface-conjugated with Cetuximab (CET) for recognizing over-expressed epidermal growth factor receptors on cancer cell surface. This drug carrier system can control the release of encapsulated drug when exposed to a high-frequency alternating magnetic field (AMF) that elevates the temperature of the liposomal membrane and triggers drug release from TML after their selective endocytosis by cancer cells. By detailed characterizing the physico-chemical and biological properties of liposomes, we demonstrated the liposomal formulation is with high biocompatibility and showed no hemolysis in vitro. Enhanced intracellular uptake of TML-CPT-11-CET by human primary glioblastoma cells (U87) also supported targeted delivery through CET-mediated endocytosis. The treatment of TML-CPT-11-CET solutions by AMF in vitro showed rise in solution temperature and enhanced drug release, which enhanced cytotoxicity of CPT-11 toward U87 though cell apoptosis as revealed from flow cytometry analysis of apoptotic cells and Western blot studies of marker proteins. Finally, the in vivo therapeutic efficacy was demonstrated in mice orthotopic xenograft brain tumor model from IVIS and PET/MRI studies.

Enhanced removal and detection of benzo[a]pyrene in environmental water samples using carbon dots-modified magnetic nanocomposites

Magnetic nanoparticles (MNPs) have already proven their efficacy in the disposal of a wide array of environmental contaminants in recent years. However, the difficulties in dispersibility and agglomeration of MNPs arising from its own physical and chemical properties limit its large-scale application. Herein, we fabricated the carbon dots/fatty acid-coated MNPs (CDs/C11-Fe3O4) through a facile and simple method. To utilize the advantage of carbon dots, these limitations can be mitigated by diminishing the size of MNPs and modifying the surface of MNPs. Detailed characterization including VSM, FT-IR, XPS and TEM conformed that the higher adsorption capacity of CDs/C11-Fe3O4 is mainly attributed to low average size (<8 nm), which is obviously lower than that of C11-Fe3O4 (about 13 nm). The CDs/C11-Fe3O4 showed higher adsorption performance than that of C11-Fe3O4 nanocomposites (76.23 ng mg−1 for CDs/C11-Fe3O4 and 59.89 ng mg−1 for C11-Fe3O4). The adsorption processes of BaP on both C11-Fe3O4 and CDs/C11-Fe3O4 nanocomposites are exothermic, and well simulated by pseudo-second-order model. Moreover, the CDs/C11-Fe3O4 were also applied for the detection of BaP in large-volume water samples, which satisfies the China environmental protection standard, are promising candidates for water remediation.

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

Citric acid-coated magnetic nanoparticles (Fe3O4–CA NPs) were successfully prepared and characterized. This magnetic nanocatalyst was employed as an efficient, recyclable, and environmentally benign heterogeneous catalyst for the transamidation of carboxamides, phthalimide, urea and thiourea with amines. Several derivatives of formylated and transamidated products were synthesized in good to excellent yields in the presence of this catalytic system. And, the catalyst could be easily separated from the reaction mixture using an external magnet and can be reused six times without any significant loss in its catalytic activity.

Gallic acid-functionalized magnetic nanoparticles: a convenient and green approach for synthesis of α-aminonitriles under solvent-free conditions

Gallic acid-coated magnetic nanoparticles were efficiently prepared, characterized by Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, scanning electron microscopy, and transmission electron microscopy, and employed as an environmentally friendly and recyclable catalyst for one-pot synthesis of three-component reaction via Strecker reaction, incorporating aldehydes/ketones, amines, and trimethylsilyl cyanides under solvent-free conditions. Operational simplicity, product purity, natural resources and reusability of the catalyst are considered as evident features of this protocol which will hopefully develop into an inexpensive, efficient, and clean strategy for the synthesis of α-aminonitriles.

A new combination for the determination of ultratrace cadmium: solid-phase microextraction by stearic acid-coated magnetic nanoparticles prior to batch-type hydride generation atomic absorption spectrometry.

Solid-phase microextraction method based on stearic acid-coated magnetic nanoparticle has been combined with batch-type hydride generation atomic absorption spectrometry (BT-HGAAS) system to determine cadmium at ultratrace levels. After the adsorption of cadmium ions onto stearic acid-coated magnetic nanoparticles, they were easily separated from the aqueous phase by means of a magnet. All the instrumental and experimental parameters such as pH of buffer solution, interaction period, concentration, and volume of NaBH4 were optimized. Under the optimal conditions, limit of quantification (LOQ) and limit of detection (LOD) for the solid-phase microextraction (SPME) based on stearic acid-coated magnetic nanoparticles-BT-HGAAS (SACMNP-BT-HGAAS) method were obtained as 270.8ng/L and 81.7ng/L, respectively. The matrix-matching calibration method was performed in order to improve the accuracy of cadmium quantification in tap water and the recovery results obtained were as follows: 88.56 ± 8.92 and 97.43 ± 9.76, for 6.0 and 8.0ng/mL of cadmium-spiked tap water samples, respectively. Graphical abstract ᅟ.

Synthesis, characterization and application of lipase-conjugated citric acid-coated magnetic nanoparticles for ester synthesis using waste frying oil.

In the present work, magnetic nanoparticles (MNPs) were prepared by chemical precipitation of trivalent and divalent iron ions which were functionalized using citric acid. The bacterial isolate Staphylococcus epidermidis KX781317 was isolated from oil-contaminated site. The isolate produced lipase, which was purified and immobilized on magnetic nanoparticles (MNPs) for ester synthesis from waste frying oil (WFO). The characterization of MNPs employed conventional TEM, XRD and FTIR techniques. TEM analysis of MNPs showed the particle size in the range of 20-50nm. FTIR spectra revealed the binding of citric acid to Fe3O4 and lipase on citric acid-coated MNPs. The citric acid-coated MNPs and lipase-conjugated citric acid-coated MNPs had similar XRD patterns which indicate MNPs could preserve their magnetic properties. The maximum immobilization efficiency 98.21% of lipase-containing citric acid-coated MNPs was observed at ratio 10:1 of Cit-MNPs:lipase. The pH and temperature optima for lipase conjugated with Cit-MNPs were 7 and 35°C, respectively. Isobutanol was found to be an effective solvent for ester synthesis and 1:2 ratio of oil:alcohol observed significant for ester formation. The ester formation was determined using TLC and the % yield of ester conversion was calculated. The rate of ester formation is directly proportional to the enzyme load. Formed esters were identified as isobutyl laurate ester and isobutyl myristate ester through GC-MS analysis.