Amino-functionalized Fe3O4 Nanoparticles Research Articles

Immobilization of Candida catenulata cells by surface-loading of an amino-functionalized Fe3O4 nanoparticles and its application as the sustainable whole-cell biocatalyst for enzymatic biodiesel production

In this study, the intracellular lipases of Candida catenulata were examined as a whole-cell biocatalyst (WCB) of soybean oil transesterification and obtained a fatty acid methyl ester (FAME) yield of 79.1%. To facilitate the biocatalyst recovery and improve its stability, the WCB was attached to magnetic Fe3O4 nanoparticles activated by a linear structure of polyethyleneimine (PEI) as the multi-amino-functionalized arm. The preparation procedure of the magnetic whole-cell biocatalysts (MWCBs) was optimized by considering the pH during immobilization (X1), the weight ratio of nanoparticles-to-cell (X2), and PEI concentration (X3) using the response surface methodology. The best optimal setting of the variables was determined at X1 of 6.1, X2 of 0.6, and X3 of 0.7 w% with the transesterification activity of 7.6 × 105 IU gbiocatalyst−1 gained a FAME yield of 78.4% after 3 h. The MWCBs showed an improvement in thermal stability where the optimal temperature was shifted from 34C to 38 °C and the deactivation energy was increased from 183.9 kJ mol−1 and 223.6 kJ mol−1 after the immobilization. The MWCBs displayed satisfactory sustainability in the repeated transesterification experiments and maintained 87.3% of the original activity after 10 cycles which was higher than the bare-WCB system with a recovery of 57.4%.

High-Performance Detection of Exosomes Based on Synergistic Amplification of Amino-Functionalized Fe3O4 Nanoparticles and Two-Dimensional MXene Nanosheets

Exosomes derived from cancer cells have been recognized as a promising biomarker for minimally invasive liquid biopsy. Herein, a novel sandwich-type biosensor was fabricated for highly sensitive detection of exosomes. Amino-functionalized Fe3O4 nanoparticles were synthesized as a sensing interface with a large surface area and rapid enrichment capacity, while two-dimensional MXene nanosheets were used as signal amplifiers with excellent electrical properties. Specifically, CD63 aptamer attached Fe3O4 nanoprobes capture the target exosomes. MXene nanosheets modified with epithelial cell adhesion molecule (EpCAM) aptamer were tethered on the electrode surface to enhance the quantification of exosomes captured with the detection of remaining protein sites. With such a design, the proposed biosensor showed a wide linear range from 102 particles μL-1 to 107 particles μL-1 for sensing 4T1 exosomes, with a low detection limit of 43 particles μL-1. In addition, this sensing platform can determine four different tumor cell types (4T1, Hela, HepG2, and A549) using surface proteins corresponding to aptamers 1 and 2 (CD63 and EpCAM) and showcases good specificity in serum samples. These preliminary results demonstrate the feasibility of establishing a sensitive, accurate, and inexpensive electrochemical sensor for detecting exosome concentrations and species. Moreover, they provide a significant reference for exosome applications in clinical settings, such as liquid biopsy and early cancer diagnosis.

Enzymatic Protein Immobilization on Amino-Functionalized Nanoparticles.

The immobilization of proteins on nanoparticles has received much attention in recent years. Among different approaches, enzymatic protein immobilization shows unique advantages because of its site-specific connection. OaAEP1 is a recently engineered peptide ligase which can specifically recognize an N-terminal GL residue (NH2-Gly-Leu) and a C-terminal NGL amino acid residue (Asn-Gly-Leu-COOH) and ligates them efficiently. Herein, we report OaAEP1-mediated protein immobilization on synthetic magnetic nanoparticles. Our work showed that OaAEP1 could mediate C-terminal site-specific protein immobilization on the amino-functionalized Fe3O4 nanoparticles. Our work demonstrates a new method for site-specific protein immobilization on nanoparticles.

Fluorescent magnetic chitosan-based hydrogel incorporating Amino-Functionalized Fe3O4 and cellulose nanofibers modified with carbon dots for adsorption and detection of Cr (VI)

A fluorescent magnetic chitosan-based hydrogel (FMCH) incorporating Amino-Functionalized Fe3O4 nanoparticles (AF-Fe3O4 NPs) and cellulose nanofibers (CNFs) modified with carbon dots (CDs) was successfully synthesized via the crosslinking method. The FMCH was used as an adsorbent for removing Cr (VI) from aqueous solution and it exhibited encouraging adsorption performance for Cr (VI). The composition and structure of FMCH were characterized and its Cr (VI) sorption performance was evaluated. The results demonstrated that this hydrogel had 3D porous structures and a higher adsorption ability of Cr (VI). The maximum adsorption capacity of this hydrogel was measured to be 212.1 mg/g at 25 °C and pH 5.0. The performance of the FMCH in Cr (VI) adsorption was evaluated through a contrast experiment with the normal chitosan hydrogel without CNFs and AF-Fe3O4 NPs. The effect of the initial concentration of Cr (VI) and contact time were also evaluated. The results confirmed that the adsorption isotherm was according to the Freundlich model, and the adsorption kinetics followed the pseudo-second-order model. Furthermore, as a fluorescent sensor for Cr (VI), the detection sensitivity and selectivity were examined. The quantitative detection of Cr (VI) was achieved in the linear range of 20–800 mg/L. Meantime, the mechanism for highly efficient adsorption and detection of FMCH for Cr (VI) was analysed by FTIR and XPS. These results showed that the excellent sorption and sensing abilities of Cr (VI) may be mainly attributed to the porous structures which provided many active sites and ion transport channels and the additional AF-Fe3O4 NPs and CNFs modified with CDs improving the sorption ability of Cr (VI) and providing a rapid visual response to Cr (VI). It showed that the FMCH can be widely used for Cr (VI) detection and removal in wastewater.

Hyperbranched aromatic polyamide modified magnetic nanoparticles for the extraction of benzoylurea insecticides.

Herein, a novel hyperbranched aromatic polyamide-coated magnetic sorbent was prepared by in situ polymerization on the surface of amino-functionalized Fe3 O4 nanoparticles. The magnetic sorbent was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, elemental analysis, Brunauer-Emmett-Teller measurement, and X-ray photoelectron spectroscopy, etc. The new magnetic sorbent was used in the magnetic solid-phase extraction for the detection of seven benzoylurea insecticides. Under optimum conditions, low method detection limits (0.56-1.20ng/mL), acceptable coefficient of determination (0.9967-0.9996), wide linear ranges (2.5-500.0ng/mL), and good repeatability (intraday: 2.0-7.3%; interday: 1.9-9.2%) were achieved. The magnetic solid-phase extraction method based on the new magnetic sorbent showed good reliability in the analysis of seven benzoylurea insecticides in real water samples, as the relative recoveries were in the range from 80.1 to 116.3% with satisfactory RSDs (0.1-9.8%). By means of density functional theory and semiempirical quantum mechanical, the binding configuration and interaction energy of hyperbranched aromatic polyamide and benzoylurea insecticides were calculated. The result of theoretical calculation revealed that the adsorption of benzoylurea insecticides by hyperbranched aromatic polyamide was derived from hydrogen bonding and π-π stacking. The contribution of π-π stacking was greater than that of hydrogen bond, which was confirmed by energy decomposition analysis.

Magnetic Combined Cross-Linked Enzyme Aggregates of Ketoreductase and Alcohol Dehydrogenase: An Efficient and Stable Biocatalyst for Asymmetric Synthesis of (R)-3-Quinuclidinol with Regeneration of Coenzymes In Situ

Enzymes are biocatalysts. In this study, a novel biocatalyst consisting of magnetic combined cross-linked enzyme aggregates (combi-CLEAs) of 3-quinuclidinone reductase (QNR) and glucose dehydrogenase (GDH) for enantioselective synthesis of (R)-3-quinuclidinolwith regeneration of cofactors in situ was developed. The magnetic combi-CLEAs were fabricated with the use of ammonium sulfate as a precipitant and glutaraldehyde as a cross-linker for direct immobilization of QNR and GDH from E. coli BL(21) cell lysates onto amino-functionalized Fe3O4 nanoparticles. The physicochemical properties of the magnetic combi-CLEAs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and magnetic measurements. Field emission scanning electron microscope (FE-SEM) images revealed a spherical structure with numerous pores which facilitate the movement of the substrates and coenzymes. Moreover, the magnetic combi-CLEAs exhibited improved operational and thermal stability, enhanced catalytic performance for transformation of 3-quinuclidinone (33 g/L) into (R)-3-quinuclidinol in 100% conversion yield and 100% enantiomeric excess (ee) after 3 h of reaction. The activity of the biocatalysts was preserved about 80% after 70 days storage and retained more than 40% of its initial activity after ten cycles. These results demonstrated that the magnetic combi-CLEAs, as cost-effective and environmentally friendly biocatalysts, were suitable for application in synthesis of (R)-3-quinuclidinol essential for the production of solifenacin and aclidinium with better performance than those currently available.

Ultrasound-assisted dispersive magnetic solid phase extraction based on amino-functionalized Fe3O4 adsorbent for recovery of clomipramine from human plasma and its determination by high performance liquid chromatography: Optimization by experimental design.

The applicability of Amino-functionalized Fe3O4 nanoparticles (NPs) as an effective adsorbent was developed for the extraction and determination of clomipramine (CLP) in plasma sample by ultrasound-assisted dispersive magnetic solid phase extraction (UADM-SPE) and high-performance liquid chromatography-ultraviolet (HPLC-UV) detection. Fabrication of the Fe3O4@SiO2-NH2 magnetic nanoparticles confirmed by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effect of different extraction parameters (i.e. pH of the sample solution, the amount of magnetic nanoparticles (MNPs), sample volume, temperature and sonication time) on the extraction recovery of CLP were investigated by response surface methodology through central composite design (CCD). The optimum condition is obtained when the affecting parameters are set to: pH of the sample solution=9, the amount of MNPs=37mg, sample volume=23mL, 25°C temperature and sonication time=1min. Under the optimum condition, extraction recovery was 90.6% with relative standard deviation of 3.5%, and enrichment factor of 117. The linear range for determination of CLP was 0.017-0.70mgL-1 with a determination coefficient (R2) of 0.999. Limit of detection (LOD) and limit of quantification (LOQ) were 0.005 and 0.0167mgL-1, respectively. The established UADM-SPE-HPLC-UV method was rapid, simple and efficient for determination of CLP in human plasma samples.

Voltammetric aptamer-based switch probes for sensing diclofenac using a glassy carbon electrode modified with a composite prepared from gold nanoparticles, carbon nanotubes and amino-functionalized Fe3O4 nanoparticles

The authors describe an aptamer based assay for the model analyte diclofenac (DCF). It is based on the use of amino-functionalized magnetite and gold nanoparticles (Fe3O4/AuNPs) that were used to decorate carbon nanotubes (CNTs) to form a highly conductive film on the surface of a glassy carbon electrode. An amino-modified DNA capture probe (ssDNA1) was placed on the Fe3O4/AuNPs using glutaraldehyde as the linker. A DCF-specific aptamer (referred to as ssDNA2) acting as the detection probe was then attached to the surface of the modified electrode via hybridization. On addition of DCF, the conformation of the aptamer undergoes a change from a random coil structure to a rigid tertiary structure (like a pocket). This change can be traced by measuring the decrease of the current observed by differential pulse voltammetry using hexacyanoferrate as a redox probe, typically at a working voltage of 0.22 V vs. Ag/AgCl. The method has a 3.4 fM detection limit and two linear responses that cover the 0.01 to 1 pM and 10 to 1300 pM DCF concentration ranges.

Immobilization of Alkaline Protease on Amino-Functionalized Magnetic Nanoparticles and Its Efficient Use for Preparation of Oat Polypeptides

Alkaline protease was successfully immobilized onto amino-functionalized Fe3O4 nanoparticles. The enzyme loading was 388.2 mg of protein/g of support and the activity recovery was more than 54.2%. After immobilization, the affinity of alkaline protease toward substrate and its stability were significantly enhanced. The immobilized enzyme still retained 50.1% of its initial activity after 10 cycles of successive reuse, exhibiting excellent operational stability. The immobilized enzyme was capable of efficiently catalyzing hydrolysis of oat bran into oat polypeptides. Under the optimized conditions, the maximum DPPH radical scavenging rate (antioxidant activity) of oat polypeptides (8.4 mg/mL) was 82.3%, which was much higher than the reported result. Moreover, the prepared oat polypeptides by immobilized enzyme showed higher antioxidant activity than those prepared by free enzyme, owing to an increase of relatively hydrophobic components of oat polypeptides. Furthermore, the immobilized enzyme was demonstr...

Synthesis and Characterization of Sulfamic-Acid Functionalized Magnetic Fe3O4 Nanoparticles Coated by Poly(amidoamine) Dendrimer

Grafting of chlorosulfuric acid on the amino-functionalized Fe3O4 nanoparticles produced sulfamic acid-functionalized magnetic Fe3O4 nanoparticles as a novel organic–inorganic hybrid material, which was characterized with X-ray diffractometry (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, scanning electron spectroscopy, and magnetization measurements (VSM). The as-prepared nanocomposite with a narrow size distribution has the crystallite size from XRD (11 ± 4 nm) and particle size from TEM analysis (12.9 ± 0.4 nm) are consistent with each other. Magnetization measurements proved the superparamagnetic property of the product.

Combination of surface imprinting and immobilized template techniques for preparation of core-shell molecularly imprinted polymers based on directly amino-modified Fe3O4 nanoparticles for specific recognition of bovine hemoglobin.

In this work, the core-shell bovine hemoglobin (BHb)-imprinted superparamagnetic nanoparticles (Fe3O4@BHb-MIPs) were synthesized by combining for the first time a surface imprinting technique and a two-step immobilized template strategy. Initially, amino-functionalized Fe3O4 nanoparticles (Fe3O4@NH2) were synthesized directly through a facile one-pot hydrothermal method. Next, BHb was immobilized on the surface of Fe3O4@NH2 through non-covalent interactions. Then, siloxane co-polymerization on the Fe3O4@NH2-protein complex surface resulted in a polymeric network molded around BHb which then became further immobilized. Finally, a thin polymer layer with specific recognition cavities for BHb was formed on the surface of Fe3O4@NH2 after the removal of the template protein. The morphology and structure property of the prepared magnetic nanoparticles were characterized by transmission electronic microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), and vibrating sample magnetometer (VSM). To obtain the best selectivity and binding performance, the polymerization and adsorption conditions were investigated in detail. Under the optimized conditions, the Fe3O4@BHb-MIPs exhibited fast adsorption kinetics, large binding capacity, significant selectivity, and favorable reproducibility. The resultant Fe3O4@BHb-MIPs could not only specifically extract BHb from a mixed standard protein mixture, but also selectively enriched BHb from a real bovine blood sample. In addition, the synthetic process was quite simple and the stability and regeneration of the Fe3O4@BHb-MIPs were also satisfactory.

Chemical Bonding Approach for Fabrication of Hybrid Magnetic Metal–Organic Framework-5: High Efficient Adsorbents for Magnetic Enrichment of Trace Analytes

A facile and efficient strategy about the synthesis of a novel kind of hybrid magnetic metal-organic framework (MOF)-5 via chemical bonding assembly was reported. The covalent bonding established between the amino functionalized Fe3O4 nanoparticles and the surface of the metal organic framework improved the chemical stability and structure uniformity of the hybrid microcrystals. Combination of MOF-5 with Fe3O4 nanoparticles allows for facile withdrawal of the porous materials by magnetic decantation. The powder X-ray diffraction patterns of the hybrid magnetic MOF-5 showed the structure of the metal organic framework was not disturbed with the decoration of magnetic nanoparticles. The as-synthesized materials combine the favorable attributes of both magnetic characteristics of Fe3O4 nanoparticles and high porosity of metal organic framework, making them excellent candidates as adsorbents for magnetic enrichment of trace analytes. Their potential applications were explored by preconcentrating polycyclic aromatic hydrocarbons and gibberellic acids from environmental, food, and plant samples prior to gas chromatography-mass spectrometry (GC/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), respectively. The results showed that the magnetic MOF-5 exhibited superior enrichment capacity for both of these nonpolar and polar analytes. The method demonstrated good precision (relative standard deviations (RSDs) of 1.7-9.7%), low detection limits (0.91-1.96 ng·L(-1) for polycyclic aromatic hydrocarbons and 0.006-0.08 μg L(-1) for gibberellic acid), and good linearity (correlation coefficients higher than 0.9949). The RSDs of batch-to-batch extraction were 2.9-11.2%. The magnetic MOF-5 was robust enough for repeatable use without damage of extraction performance.

Synthesis of streptavidin-conjugated magnetic nanoparticles for DNA detection

In this paper, we report a fabrication of streptavidin-coated magnetic nanoparticles used for DNA detection. Initially, amino-functionalized Fe3O4 nanoparticles with high saturation magnetization are prepared by a photopolymerization method using allylamine as monomer. It is followed by covalent immobilization of streptavidin onto the particle surface via a two-step reaction using glutaraldehyde as coupling agent. Streptavidin-coated magnetic nanoparticles are characterized and further tested for their ability to capture DNA target after binding biotinylated oligonucleotide probes. The results show that the products (~27.2 nm) have a maximum biotin-binding capacity of 0.71 nmol mg−1 when the immobilization reaction is conducted with a mass ratio of streptavidin to magnetic carriers above 0.2 in phosphate buffered saline (pH 7.4) for 24 h. In addition, highly negative ζ-potential and good magnetic susceptibility of the nanocomposites make them applicable for DNA collection and detection, which is verified by the results from the preliminary application of streptavidin-coated magnetic nanoparticles in DNA detection. Therefore, the magnetic nanoparticles provide a promising approach for rapid collection and detection of gene.

A highly efficient magnetic solid acid catalyst for synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation

Fe3O4 nanoparticles were prepared by chemical coprecipitation method and subsequently coated with 3-aminopropyltriethoxysilane (APTES) via silanization reaction. Grafting of chlorosulfuric acid on the amino-functionalized Fe3O4 nanoparticles afforded sulfamic acid-functionalized magnetic nanoparticles (SA-MNPs). SA-MNPs was found to be a mild and effective solid acid catalyst for the efficient, one-pot, three-component synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation. This protocol afforded corresponding imidazoles in shorter reaction durations, and in high yields. This green procedure has many obvious advantages compared to those reported in the previous literatures, including avoiding the use of harmful catalysts, easy and quick isolation of the products, excellent yields, short routine, and simplicity of the methodology.

High efficient removal of Pb (II) by amino-functionalized Fe3O4 magnetic nano-particles

An amino-functionalized magnetic nano-adsorbent (MNPs-NH2) has been prepared by a simple one-pot method for the removal of Pb (II). These amino-functionalized Fe3O4 nano-particles showed a high adsorption capacity and efficient adsorption toward Pb (II) in an aqueous medium. The studies on the adsorption of Pb (II) ions revealed that the process obey the pseudo-second order kinetic model, the determining step might be chemical sorption. Among the various isotherm models, the experimental data for the adsorption of Pb (II) were found to follow the Langmuir isotherm and the maximum adsorption capacity was 40.10mgg−1 at pH 5 and 298K. The sorption mean free energy from the Dubinin–Radushkevich isotherm was found to be 10.31kJmol−1, indicating a chemical sorption. In addition, Pb (II) ions could be desorbed from nano-adsorbents and the MNPs-NH2 exhibited a good reusability. Importantly, about 98% of Pb (II) could be removed by MNPs-NH2 from industrial wastewater and tap water.