Hydrophobic Fe3O4 Nanoparticles Research Articles

Biocompatible protein-based self-assembled nanocomposite as efficient drug nanocarrier and antibacterial agent

To fulfill diverse application-specific purposes, functional nanoparticles encapsulated into protein-based self-assemblies show promising advantages includes easy preparation, high biocompatibility and multiple properties. In this study, the model protein of BSA used for multi-component self-assembly, including hydrophobic Fe3O4 nanoparticles, nano-ZnO and curcumin, was constructed through hydrophobic interactions. The obtained composites of BSA-Fe3O4&ZnO and BSA-Fe3O4&ZnO&curcumin self-assemblies were tested for antibacterial and drug delivery, respectively. It was found that the multicomponents loaded into protein assembly confer a simple yet robust synthetic method resulting in the produced nanocomposites with high stability and desirable biocompatibility. Notably, the protein self-assemblies successfully increased the antibacterial efficacy of hydrophobic ZnO nanoparticles, and promote the intracellular delivery of poorly soluble curcumin to exert significant killing effects against cancer cells. Therefore, the constructed multi-component contained protein self-assembly that enables hydrophobic interactions of compositional nanoparticles holds promising potentials for the versatile uses in biomedical aspects.

Tumbleweed-like aggregation-induced-emission microrobots: Swarming for ultra-tracing of hydrazine

Hydrazine (N2H4) poses severe health risks even in trace amounts due to the highly carcinogenic and teratogenic degeneration while it is frequently used in industrial products. However, current techniques are difficult to perform in-situ detection of N2H4 within confined sophisticated reactors or slim apparatus. Bioinspired by natural plant tumbleweed, we have demonstrated that swarming aggregation-induced emission microrobots (AIE-bots), which have a tumbleweed-like macroporous structure, are capable of performing motile-targeting detection of N2H4 leakage or accumulation. In this protocol, the AIE-bots are assembled from emulsion droplets containing AIEgens and hydrophobic Fe3O4 nanoparticles evenly distributed in CHCl3 and n-hexane through phase separation during the evaporation of volatile solvents. Upon the application of a precessing B(t), the AIE-bots can wobble in swarms and adaptively navigate through narrow channels without adjusting B(t). Additionally, they can efficiently ascend steep slopes with angles up to 45° due to the lightweight and coarse surface. While moving, the swarming AIE-bots can in-situ perceive the N2H4 concentration surrounding with an LOD of 3.81 ppb via fluorescence enhancement based on the Schiff base reaction. This work provides a microrobot detecting unknown toxin leakage or accumulation in hard-to-reach microenvironments, and will inspire the development of fluorescent micro-/nanorobots for intelligent motile sensing.

Zn(II)-complex-based hydrolytic nanozymes prepared by nanoprecipitation for the hydrolysis of carboxylic esters and methyl parathion

Zn(II)-complex-based nanozymes have been extensively used for the cleavage of carboxylic esters and phosphate esters. Cooperativity between neighboring Zn(II) complexes is of paramount importance for the development of Zn(II)-complex-based nanozymes with excellent efficiency. Here, we have developed a controllable synthetic strategy for the construction of Zn(II)-complex-based nanozymes by using the nanoprecipitation technique, which could bring Zn(II) complexes in close proximity and regulate their microenvironments. Linear copolymers containing di(2-picolyl)amine moieties were used for the preparation of Zn(II)-complex-based nanozymes by the coordination between di(2-picolyl)amine and Zn(II) ion. These Zn(II)-complex-based nanozymes displayed excellent catalytic performance in the hydrolysis of carboxylic esters. Moreover, hydrophobic Fe3O4 nanoparticles could be incorporated into Zn(II)-complex-based nanozymes via the one-step nanoprecipitation approach, enabling the recovery of nanozymes by using a permanent magnet. Such nanozymes effectively catalyzed the hydrolysis of methyl parathion, which is highly resistant to spontaneous hydrolysis and is extremely hazardous. These nanozymes may find application in the hydrolysis of hazardous carboxylic esters and phosphate esters.

Synthesis and characterization of nearly monodisperse superparamagnetic (Fe3O4/Poly(methyl methacrylate))-SiO2 nanoparticles with raspberry-like morphology

Uniform and nearly monodisperse superparamagnetic Fe3O4/Poly(methyl methacrylate) (core)/SiO2 (shell) nanoparticles with raspberry-like morphology and high saturation magnetization were prepared in three different steps. At first, a facile, one-shot procedure to synthesize hydrophobic Fe3O4 nanoparticles through a modified co-precipitation method was implemented. Based on the hydrophobic interactions, these nanoparticles were used directly in a mini-emulsion polymerization resulting in encapsulation with PMMA. Then, for the covering with a silica shell, the surfaces of the Fe3O4/PMMA nanospheres were hydrolyzed in alkaline media and became hydrophilic through hydrolyzation. In the last step shell deposition of the Fe3O4/PMMA nanospheres through a modified Stober method was implemented. The surface morphology was investigated by scanning electron microscopy (SEM) and the core-shell structure and the prepared products’ diameters were measured by transmission electron microscopy (TEM); the size of the magnetic nanospheres was approximately 83 nm. Vibrating sample magnetometry (VSM) showed high magnetic saturation and superparamagnetic characteristics of the particles. Thermogravimetric analysis (TGA) was used as a supplementary test and, based on the mass loss at high temperature (600°C), the magnetic (Fe3O4) and non-magnetic content (PMMA) of the Fe3O4/PMMA nanospheres was measured as 81 and 19%, respectively. The narrow polydispersity of the nanospheres, measured by dynamic light scattering (DLS), was approximately 0.101. In every preparation step, the synthesized products were characterized by Fourier transform infrared (FTIR) spectroscopy. Our study focused on designing two-layered magnetic nanoparticles with drug delivery potential using two-layer encapsulation based on the hydrophobic and hydrophilic surface characteristics of the PMMA core and silica shells, respectively.

A Sampling of Highlights from the Literature: Article Recommendations from Our Deputy and Senior Editors.

A two-step circuit allows ultrasensitive sensing of antigen density (from Ron Mader via Flickr)Recognition of normal cells expressing a low density of target antigen is a barrier to chimeric antigen receptor (CAR) T–cell therapy for some cancers. Hernandez-Lopez et al. have designed a two-step antigen-recognition circuit enabling CAR T cells to distinguish cells expressing high and low densities of target antigen. They engineer T cells to express a synthetic Notch receptor with low affinity for HER2. HER2 recognition by this receptor drives expression of a CAR with high affinity for HER2. These cells kill tumor cell lines and 3D spheroids expressing high densities of HER2 but spare those with low densities of HER2, showing this approach could limit on-target, off-tumor responses.Hernandez-Lopez RA, …, Lim WA. Science 2021 Mar 12;371:1166–71.Alveolar rhabdomyosarcoma (from Nephron via Wikimedia Commons)Increased understanding of the microenvironment at distant sites prior to metastases becoming detectable at those sites could lead to new strategies for treating metastases. In a syngeneic orthotopic model of rhabdomyosarcoma that spontaneously metastasizes to the lungs, Kaczanowska et al. identify a transcriptional program indicative of myeloid-mediated immune suppression in the premetastatic lung. Intravenous administration of myeloid cells genetically engineered to express IL12 reprograms the premetastatic niche, reversing the immunosuppressive phenotype and inducing T cell–mediated antitumor immunity, such that metastases are reduced and survival improved. These data suggest a new strategy for treating metastatic disease.Kaczanowska S,…, Kaplan RN. Cell 2021 Apr 15;184:2033–52.e21.MRTFs play dual roles in cancer and antitumor immunity (from Fig. 1 of Finch-Edmondson et al., Cell Mol Biol Lett 2016)Tumor cells have multiple ways of evading immune detection. Tello-Lafoz et al. find that myocardin-related transcription factors (MRTF) are “double agents.” On one hand, MRTFs support tumor progression and metastasis, but on the other hand, high expression boosts CTL and natural killer–cell activation, an effect enhanced by anti-CTLA4 therapy. High MRTF expression also alters the rigidity of the tumor cell F-actin cytoskeleton, a mechanical change that renders the tumor cells more susceptible to elimination. The data bring to light “mechanical” changes that can occur that allow for improved immunosurveillance and tumor killing.Tello-Lafoz M, …, Er EE. Immunity 2021 Mar 22. DOI: 10.1016/j.immuni.2021.02.020.CD161 on T cells is inhibitory (T/NK-cell CD161 IHC; from Fig. 2F of Dorfeshan et al., Biomed Res Int 2013)T cells play a vital role in the efficacy of immunotherapies. Using single-cell RNA sequencing, Mathewson et al. analyze tumor-infiltrating T cells in patients with glioma. They identify clonal CD8+ T cells coexpressing cytotoxic programs and natural killer (NK) cell–associated genes, including CD161 (encoded by KLRB1). CD161 is identified as an inhibitory receptor that limits T cell–mediated tumor killing. Inactivation of KLRB1 or blockade of CD161 restores T-cell killing of glioma targets in vitro and in vivo. These data point to CD161 and other NK cell–associated receptors (expressed by T cells) as potential immunotherapeutic targets.Mathewson ND, …, Wucherpfennig KW. Cell 2021 Mar 4;184:1281–98.e26.Bacteria-derived peptides can be presented by tumor cells (by Moustafa Abdou via Ask Hematologist/Understand Hematology)Bacteria are associated with some cancers and have a role in modulating immune function. Kalaora et al. investigate whether bacterial antigens are expressed on melanoma HLA molecules. More than 250 bacteria-derived peptides, originating from 41 bacterial species, are identified. A subset of these peptides are not only presented by HLA-I/II in different tumors within the same patient but also found across samples from different patients. The peptides presented by tumor cells are immunogenic and activate tumor-infiltrating lymphocytes ex vivo, providing further insight into the impact of bacteria on antitumor immunity.Kalaora S, …, Samuels Y. Nature 2021 Apr 1;592:138–43.3-D rendering of a neutrophil (from Blausen.com staff via Wikimedia Commons)Microrobots controlled by rotating magnetic fields have potential to allow precise therapeutic targeting of cancers. However, current microrobots are susceptible to immune clearance and cannot efficiently penetrate biological barriers such as the blood–brain barrier. Zhang et al. show these challenges can be addressed using neutrophil-based microrobots, referred to as “neutrobots.” Neutrobots are made in three steps: first, synthesis of nanogels loaded with hydrophobic Fe3O4 nanoparticles and paclitaxel; second, coating of the nanogels with the outer membrane of Escherichia coli; and third, phagocytosis of the coated nanogels by neutrophils. The neutrobots accurately deliver paclitaxel in a postoperative orthotopic glioma model, increasing survival, thereby highlighting the therapeutic potential of neutrobots.Zhang H, …, He Q. Science Robotics 2021 Mar 24;6:eaaz9519.

Characterization of Magnetite/Iodized Oil Magnetic Fluid for Embolization and Hyperthermia Application

Fe3O4 nanoparticles/iodized oil magnetic fluids (FIOMFs) have showed potential in targeted hyperthermia for liver tumors; in this paper, FIOMFs were simply and conveniently prepared by dispersing the synthesized hydrophobic Fe3O4 nanoparticles (FNPs) in iodized oil; the stability, magnetothermal effects, and the biotoxicity of FIOMFs were evaluated. The results showed that the stability of FIOMFs was mainly influenced by the morphology and the size of FNPs. FNPs prepared with FeCl3·6H2O, oleylamine (OAm), ethylene glycol (EG), and stearic acid exhibited the best suspension stability, which could suspend in iodized oil stably for a long time. Depending on the FNP content and the parameters of the alternating magnetic field (AMF), the temperature of FIOMF in AMF can reach up to more than 70 °C within 60 s, exhibited excellent magnetothermal effects. The in vitro cytotoxicity tests indicated the cytotoxicity of FNPs is mainly influenced by its concentration in cells.

Effect of Zwitterionic Surfactant Ligand Monolayer on Magnetic Hyperthermia Properties of Monosize Fe3O4 Nanoparticles

Here Brown relaxation time was altered to enhance magnetic hyperthermia value. Narrow size distributed, hydrophobic Fe3O4 nanoparticles were synthesized by solvothermal reflux method. It is reported that the existing both single step and two-step ligand exchange protocols could not replace hydrophobic surfactant ligand completely. Hence, as-synthesized samples were transferred into hydrophilic by completely removing the hydrophobic surfactant on the nanoparticles by high polar ionic liquids and ligated short-chain bidentate zwitterionic dopamine sulfonate on nanoparticles surface. The short molecules will fast up the Brown relaxation time compared to long molecule surfactant such as polyethylene glycol (PEG). The resultant sample shows magnetic hyperthermia value of 558 Js− 1g− 1 of Fe content at 316 kHz and 35.33 kA/m, at 2 mg/mL. The obtained hyperthermia is very high compared to long-chain PEG ligated Fe3O4 nanoparticles. It is attributed to relaxation time difference of long-chain PEG ligated Fe3O4 and short molecule zwitterion surfactant stabilized Fe3O4. Present hyperthermia results are the first report on zwitterionic dopamine sulfonate anchored Fe3O4 superparamagnetic nanoparticles.

Recoverable magnetic nanoparticles as hydrate inhibitors

This work investigates a mixed emulsifier system composed of Fe3O4 nanoparticles and Span 20 for the development of reusable hydrate inhibitors. Hydrophobic Fe3O4 nanoparticles were prepared by adsorption of Span 20 on the particle surface, and this was confirmed through UV-absorbance and elemental analysis. Water-in-oil Pickering emulsion droplets with Span 20-adsorbed Fe3O4 nanoparticles were analyzed using a confocal microscope and observed through SEM and EDS mapping of solidified emulsion samples. Due to the physical hindrance of the Span 20-adsorbed Fe3O4 nanoparticles, they can act as both kinetic hydrate inhibitors and anti-agglomerants. The induction time is significantly increased by hindering the nucleation, and the torque is lowered by the anti-adhesive behaviors of the hydrophobic particles. The additional injection of the nanoparticles induces the formation of a capillary water bridge, which increases the contact area and hydrate former supersaturation and reduces the dispersion of the emulsion droplet. Therefore, there would be an optimal concentration of Span 20-adsorbed Fe3O4 nanoparticles which maximizes the inhibition performance. A boot drum separator with a magnetic field shows excellent recovery performance for magnetic hydrate inhibitors with the injection of acetone into the boot separator to break the Pickering emulsions. Overall, the Span 20-adsorbed Fe3O4 nanoparticles provide dual roles as kinetic hydrate inhibitors and anti-agglomerants, providing a new approach for the recovery of hydrate inhibitors with superparamagnetic properties.

Degradable and Thermosensitive Microgels with Tannic Acid as the Sole Cross-Linker.

Poly(N-isopropylacrylamide) (PNIPAM)-tannic acid (TA) microgels were successfully prepared via surfactant-free emulsion polymerization (SFEP) at 70 °C in aqueous solution using N-isopropylacrylamide (NIPAM) as the monomer and a natural polyphenol macromolecule, TA, as the sole cross-linker. The cross-linking network of the PNIPAM-TA microgels was confirmed to contain both physical cross-linking structures formed via hydrogen-bonding interactions between TA and PNIPAM chains and chemical cross-linking structures formed via capturing the radicals of propagating polymer chains by catechol and pyrogallol groups of TA. Furthermore, TA was applied to modify the surface of hydrophobic Fe3O4 nanoparticles, leading to hydrophilic Fe3O4@TA composite nanoparticles, which were successfully used as the cross-linker to fabricate PNIPAM-Fe3O4@TA organic-inorganic hybrid microgels. The obtained PNIPAM-TA and PNIPAM-Fe3O4@TA organic-inorganic hybrid microgels had a uniform spherical shape with a relatively narrow size distribution and exhibited thermosensitive behavior and pH-tunable degradation. The PNIPAM-TA microgels were stable in the pH range of 1.3-11.1 but underwent complete degradation with pH above 11.4. The PNIPAM-Fe3O4@TA hybrid microgels were partially degraded at pH values of 1.3 and 2.1, stable in the pH range of 3.1-11.1, and underwent complete degradation at pH above 11.4. The partial degradation of PNIPAM-Fe3O4@TA organic-inorganic hybrid microgels under strong acidic conditions was attributed to the disintegration of Fe3O4 nanoparticles. The complete degradation of both microgels at pH above 11.4 was attributed to the hydrolysis of ester groups of TA under strong alkali conditions.

Design of stable super-hydrophobic/super-oleophilic 3D carbon fiber felt decorated with Fe3O4 nanoparticles: Facial strategy, magnetic drive and continuous oil/water separation in harsh environments

Stable and efficient separation of oil slicks from oil-contaminated water in harsh environments is still a big challenge. Recently, three-dimensional hydrophobic/super-oleophilic materials exhibit promising application in continuous oil/water separation. Herein, we developed a facial method to prepare three-dimensional super-hydrophobic/super-oleophilic carbon fiber felt (CFF) materials by anchoring the hydrophobic Fe3O4 nanoparticles onto 3D CFF. Owing to the well-defined micro-/nano-structure and low surface energy, as-obtained CFF materials showed high water contact angle of 164.1 ± 1.3° and low oil contact angle of 0°. As a result, as-prepared CFF materials exhibited excellent adsorption driven by external magnetic field and continuous oils separation from immiscible oil/water mixtures, with the high separation efficiency up to 99.99%. More importantly, the resulting super-wetting material showed stable super-hydrophobic property and continuous oil/water separation performance in harsh environments such as strong corrosive/salt solutions, organic solvents, and high/low-temperature systems. Therefore, this work provides an alternative strategy to obtain 3D super-hydrophobic/super-oleophilic materials with easy operation, durable and efficient continuous oil/water separation performance, exhibiting potential application for treating the large-scale industrial oily wastewater in harsh environments.

Multi-targeting magnetic hyaluronan capsules efficiently capturing circulating tumor cells

Accurate detection and isolation of circulating tumor cells (CTCs) hold high value for urgent clinical applications in cancer prognosis and treatment monitoring. Even though the immuno-magnetic isolation strategy has been an important milestone for enrichment of precious CTCs from complex clinical samples, the origin and cell cycle change of CTCs would influence greatly on the performance of antibody-mediated capture process. Herein, we proposed the multi-targeting magnetic capsules (TMCs), which combine the natural immune recognition and tumor-specific ligand targeting, for the purpose of rare CTCs capture. Generally, the fluorescence-visible magnetic capsules (MCs) were constructed via an ultra-sonication assembly procedure using fluorescently-labeled thiolated hyaluronan (RhB-HA-SH) and hydrophobic Fe3O4 nanoparticles, during which superparamagnetic Fe3O4 were blocked by RhB-HA-SH cross-linking via oxidation of the thiol groups. Functionalized with folic acid (FA) and anti-epithelial-cell-adhesion-molecule (anti-EpCAM) antibody, the obtained fluorescent-visible multi-targeting hyaluronan magnetic capsules could capture and isolate more than 88% of rare MCF-7 cells in mimic biological samples in 15 min of incubation. Moreover, these isolated cells still showed good proliferation and migration abilities, facilitating further CTCs-related studies. Furthermore, these TMCs were successfully employed to the capture and detection of few CTCs in 1.5 mL cancer patient peripheral blood samples, indicating that they could be a promising candidate for CTCs capture and detection through simple and fast magnetic manipulation.

Synthesis and Characterization of Hydrophobic Fe3O4 Magnetic Nanoparticles with High Saturation Magnetization

A simple one-step solvothermal method is proposed to prepare hydrophobic Fe3O4 nanoparticles (MNPs) using iron acetylacetonate (Fe(acac)3), oleylamine (OAm), and ethylene glycol (EG). X-ray powder diffraction, scanning electron microscope, infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectrometry, and vibrating sample magnetometer are used to characterize the structure, morphology, and properties of products. The testing results indicate that the as-synthesized products are spherical-like hydrophobic MNPs, superparamagnetic at room temperature, with a saturation magnetization up to 76.8 emu/g. The good hydrophobic property of MNPs is attributed to the coverage of oleylamine, without causing a remarkable loss of magnetic property. In addition, the influences of material ratio, aging time, oleic acid, and stearic acid used as additives are studied in our research.

Efficient in situ growth of platinum nanoclusters on the surface of Fe3O4 for the detection of latent fingermarks

Hydrophobic Fe3O4 nanoparticles were modified with polyethyleneimine (PEI) to obtain hydrophilic Fe3O4 nanoparticles. By reducing the content of H2PtCl6 solution by using l-ascorbic acid (AA) as a reductive agent, fluorescent platinum nanoclusters (Pt NCs) were incubated into the PEI-modified Fe3O4 nanoparticles. The prepared Fe3O4@Pt NCs microspheres possessed a uniform size, improved monodispersity, high magnetization (40.8 emu/g) and high fluorescence quantum yield (9.0%). Moreover, compared to the reported methods, this method demonstrated that the incubation of Pt NCs on the surface of PEI-Fe3O4 was more convenient and needed less reaction time (about 10 min). The experimental results showed that latent fingermarks developing with Fe3O4@Pt NCs powder exhibit excellent ridge details. The Fe3O4@Pt NCs with superparamagnetism and excellent fluorescence showed great potential in forensic science.

Magnetic separable chitosan microcapsules decorated with silver nanoparticles for catalytic reduction of 4-nitrophenol

In the work, we have synthesized silver (Ag) nanoparticles deposited chitosan (CS) microcapsules with magnetic multiple Fe3O4 cores (denoted as Fe3O4/CS-Ag) as efficient catalysts for the reduction of 4-nitrophenol. The Fe3O4/CS-Ag catalysts are prepared by coating hydrophobic Fe3O4 nanoparticles with chitosan via a multiple emulsion-chemical crosslinking method and following in situ deposition of Ag nanoparticles onto the surfaces. The morphology and composition of the Fe3O4/CS-Ag microcapsules are characterized by Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy. Moreover, the catalytic activity of the Fe3O4/CS-Ag catalyst was investigated, which shows a conversion efficiency as high as 98% within 15min for the reduction of p-nitrophenol to p-aminophenol. At the same time, the recovered Fe3O4/CS-Ag catalyst with an external magnet can retain good activity after 10 cycles. These results indicate that the multiple emulsion-chemical crosslinking method is an efficient and simple way for the preparation of magnetic separable chitosan microcapsules, and the fabricated Fe3O4/CS-Ag is a promising catalytic material with excellent catalytic activity and convenient recovery ability.

Fluorescence quenching study on the interaction of ferroferric oxide nanoparticles with bovine serum albumin

Fluorescence quenching was used to study the potential interaction mechanism of Bovine serum albumin (BSA) with either hydrophilic ferroferric oxide (Fe3O4) nanoparticles (NPs) or hydrophobic Fe3O4 NPs. The experimental results indicated the mechanism between BSA and hydrophilic Fe3O4 NPs was static quenching and the one between BSA and hydrophobic Fe3O4 NPs was dynamic process that was drove by Förster's resonance energy transfer (FRET). And the binding parameters for the interaction of BSA with either hydrophilic or hydrophobic Fe3O4 NPs were calculated by using the fluorescence quenching measurement. The binding constant (KA) values of hydrophilic Fe3O4 NPs were 8518.73±23.35 (at 298K), 1190.31±15.41 (at 306K) and 321.97±8.57 (at 313K), respectively. The thermodynamic analysis implied that the intermolecular forces between BSA and hydrophilic Fe3O4 NPs were Van der Waals interaction or hydrogen bond, because the values of ΔH and ΔS between them were negative. While the one of BSA and hydrophobic Fe3O4 NPs involved hydrophobic forces, owing to the positive ΔH and ΔS between them. But they were all enthalpy-driven and exothermic, since their ΔG values were all negative. Synchronous fluorescence spectroscopy suggested that the conformation of tryptophan residue of BSA was changed in the presence of hydrophilic Fe3O4 NPs or hydrophobic Fe3O4 NPs, because the position of the maximum emission wavelength had a discernible red shift.

Synthesis of polyelectrolyte nanocapsules with iron oxide (Fe3O4) nanoparticles for magnetic targeting

Magnetic vehicles have become highly promising for delivery of therapeutic actives as they can be targeted to selected pathologically changed tissues/cells through the application of a magnetic field gradient. The aim of this work was to prepare and characterize nanocapsules with iron oxide nanoparticles for magnetic targeting. Nanocapsules were prepared by encapsulation of oil droplets containing hydrophobic Fe3O4 nanoparticles (NP) in polyelectrolyte shells, using the layer by layer technique. The average size of synthesized nanocapsules was ∼100nm and the batch concentration was 1011nanocapsules/ml. Morphology of magnetic carriers were investigated by Cryo-Scanning Electron Microscopy.

PH-Responsive biodegradable polymeric micelles with anchors to interface magnetic nanoparticles for MR imaging in detection of cerebral ischemic area.

A novel type of pH-responsive biodegradable copolymer was developed based on methyloxy-poly(ethylene glycol)-block-poly[dopamine-2-(dibutylamino) ethylamine-l-glutamate] (mPEG-b-P(DPA-DE)LG) and applied to act as an intelligent nanocarrier system for magnetic resonance imaging (MRI). The mPEG-b-P(DPA-DE)LG copolymer was synthesized by a typical ring opening polymerization of N-carboxyanhydrides (NCAs-ROP) using mPEG-NH2 as a macroinitiator, and two types of amine-terminated dopamine groups and pH-sensitive ligands were grafted onto a side chain by a sequential aminolysis reaction. This design greatly benefits from the addition of the dopamine groups to facilitate self-assembly, as these groups can act as high-affinity anchors for iron oxide nanoparticles, thereby increasing long-term stability at physiological pH. The mPEG moiety in the copolymers helped the nanoparticles to remain well-dispersed in an aqueous solution, and pH-responsive groups could control the release of hydrophobic Fe3O4 nanoparticles in an acidic environment. The particle size of the Fe3O4-loaded mPEG-b-P(DPA-DE)LG micelles was measured by dynamic light scattering (DLS) and cryo-TEM. The superparamagnetic properties of the Fe3O4-loaded mPEG-b-P(DPA-DE)LG micelles were confirmed by a superconducting quantum interference device (SQUID). T2-weighted magnetic resonance imaging (MRI) of Fe3O4-loaded mPEG-b-P(DPA-DE)LG phantoms exhibited enhanced negative contrast with an r2 relaxivity of approximately 106.7 mM(-1) s(-1). To assess the ability of the Fe3O4-loaded mPEG-P(DE-DPA)LG micelles to act as MRI probes, we utilized a cerebral ischemia disease rat model with acidic tissue. We found that a gradual change in contrast in the cerebral ischemic area could be visualized by MRI after 1 h, and maximal signal loss was detected after 24 h post-injection. These results demonstrated that the Fe3O4-loaded mPEG-b-P(DPA-DE)LG micelles can act as pH-triggered MRI probes for diagnostic imaging of acidic pathological tissues.

Preparation and characterization of magnetic poly(styrene–glycidyl methacrylate) microspheres for highly efficient protein adsorption by two‐stage dispersion polymerization

ABSTRACTMicrometer‐sized superparamagnetic poly(styrene–glycidyl methacrylate)/Fe3O4 spheres were synthesized by two‐stage dispersion polymerization with modified hydrophobic Fe3O4 nanoparticles, styrene (St), and glycidyl methacrylate (GMA). The morphology and properties of the magnetic Fe3O4–P (St‐GMA) microspheres were examined by scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, thermogravimetric analysis, and attenuated total reflectance. The average size of the obtained magnetic microspheres was 1.50 μm in diameter with a narrow size distribution, and the saturation magnetization of the magnetic microspheres was 8.23 emu/g. The magnetic Fe3O4–P (St‐GMA) microspheres with immobilized iminodiacetic acid–Cu2+ groups were used to investigate the adsorption capacity and selectivity of the model proteins, bovine hemoglobin (BHb) and bovine serum albumin (BSA). We found that the adsorption capacity of BHb was as high as 190.66 mg/g of microspheres, which was 3.20 times greater than that of BSA, which was only 59.64 mg/g of microspheres as determined by high‐performance liquid chromatography. With a rather low nonspecific adsorption, these microspheres have great potential for protein separation and purification applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43005.

Well-designed multihollow magnetic imprinted microspheres based on cellulose nanocrystals (CNCs) stabilized Pickering double emulsion polymerization for selective adsorption of bifenthrin

In our study, the multihollow magnetic imprinted microspheres (HM-IMs) were synthesized by Pickering double water in oil in water (w1/o/w2) emulsion polymerization. In w1/o/w2 emulsion, hydrophobic Fe3O4 nanoparticles were used to stabilize the inner water in oil (w1/o) droplets. Cellulose nanocrystals (CNCs), which were acquired from cotton source by acid hydrolysis process, were used as stabilizer on the outer oil in water (o/w2) interface. The template bifenthrin (BF) and functional monomer were contained in oil phase. The imprinting process was conducted by thermally initiated radical polymerization of functional and cross-linked monomers. The multihollow structure was well-designed by adjusting amounts of stabilizers and degree of emulsification. Characterization results indicated that the Pickering double w1/o/w2 emulsion and HM-IMs were successfully produced. The as-prepared sorbents possessed thermal stability (below 250°C) and enough magnetic sensitivity (Ms=0.46emug−1). The sorbents were used to selectively adsorb template BF. The adsorption equilibrium was fitted well by Langmuir isothermal model, indicating the monolayer molecular adsorption for BF. And pseudo-second-order kinetics model gave a better fit to the kinetic data, suggesting that the chemical process could be the rate-limiting step in the adsorption of BF. The selective recognition capability for template BF of HM-IMs sorbents was proved to be excellent compared with structural analogs. And the HM-IMs presented good dynamic adsorption performance for BF and the fixed bed adsorption conditions were tunable. The regeneration ability of the sorbents was also proved to be satisfying by five repeated adsorption–desorption cycles.

Selective removal of erythromycin by magnetic imprinted polymers synthesized from chitosan-stabilized Pickering emulsion

Magnetic imprinted polymers (MIPs) were synthesized by Pickering emulsion polymerization and used to adsorb erythromycin (ERY) from aqueous solution. The oil-in-water Pickering emulsion was stabilized by chitosan nanoparticles with hydrophobic Fe3O4 nanoparticles as magnetic carrier. The imprinting system was fabricated by radical polymerization with functional and crosslinked monomer in the oil phase. Batches of static and dynamic adsorption experiments were conducted to analyze the adsorption performance on ERY. Isotherm data of MIPs well fitted the Freundlich model (from 15°C to 35°C), which indicated heterogeneous adsorption for ERY. The ERY adsorption capacity of MIPs was about 52.32μmol/g at 15°C. The adsorption kinetics was well described by the pseudo-first-order model, which suggested that physical interactions were primarily responsible for ERY adsorption. The Thomas model used in the fixed-bed adsorption design provided a better fit to the experimental data. Meanwhile, ERY exhibited higher affinity during adsorption on the MIPs compared with the adsorption capacity of azithromycin and chloramphenicol. The MIPs also exhibited excellent regeneration capacity with only about 5.04% adsorption efficiency loss in at least three repeated adsorption–desorption cycles.