Preparation and characterization of antifouling thermosensitive magnetic nanoparticles for applications in biomedicine

Copolymer brushes grafting onto magnetic nanoparticles (MNPs) were prepared via surface free radical polymerization to improve antifouling properties of thermosensitive MNPs. A chain transfer agent was firstly attached to MNPs by silanization. Copolymerization of poly(ethylene glycol) monomethacrylate and N-isopropylacrylamide was then conducted to graft polymer brushes on the particles surface via surface free radical polymerization. The lower critical solution temperature of the obtained thermosensitive MNPs is 43 °C, which is higher than that of homopolymer poly(N-isopropylacrylamide). Nonspecific adsorption of protein was resisted at room temperature and 45 °C. The result suggested that poly(ethylene glycol) monomethacrylate segments decrease nonspecific adsorption of protein above LCST.     

Synthesis and characterization of PEG-iron oxide core-shell composite nanoparticles for thermal therapy

In this study, core-shell nanoparticles were developed to achieve thermal therapy that can ablate cancer cells in a remotely controlled manner. The core-shell nanoparticles were prepared using atomic transfer radical polymerization (ATRP) to coat iron oxide (Fe₃O₄) nanoparticles with a poly(ethylene glycol) (PEG) based polymer shell. The iron oxide core allows for the remote heating of the particles in an alternating magnetic field (AMF). The coating of iron oxide with PEG was verified through Fourier transform infrared spectroscopy and thermal gravimetric analysis. A thermoablation (55 °C) study was performed on A549 lung carcinoma cells exposed to nanoparticles and over a 10 min AMF exposure. The successful thermoablation of A549 demonstrates the potential use of polymer coated particles for thermal therapy.     

A biocompatible approach to surface modification: Biodegradable polymer functionalized super-paramagnetic iron oxide nanoparticles

In the study, Fe₃O₄ nanoparticles with a size range of 10–20 nm were firstly prepared by the modified controlled chemical coprecipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline medium. Then, the super-paramagnetic iron oxide nanoparticles were covalently modified by biodegradable polymers such as polyethylene glycol (PEG) and poly(ethylene glycol)-co-poly(d,l-lactide) (PELA). The size and its distribution of the nanoparticles were determined by dynamic light scattering measurements (DLS). The magnetic nanoparticles was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), Fourier transform infrared spectroscopy (FT-IR) and UV–visible spectrophotometry (UV). Magnetic properties were measured using a vibrating sample magnetometer. And the 5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate the biocompatibility of the magnetic nanoparticles. The results showed that the Fe₃O₄ nanoparticles functionalized by PEG and PELA possessed a mean size of 43.2 and 79.3 nm, respectively, and exhibited an excellent biocompatibility.     

Polymer grafting onto magnetite nanoparticles by “click” reaction

In this article, we described click chemistry methodology for the incorporation of biocompatible polymer chains to Magnetite nanoparticles (NPs). We used a reduction co-precipitation method to obtain Fe₃O₄ particles in aqueous solution. As a next step, magnetic NPs surface were modified by a silanization reaction with (3-bromopropyl)trimethoxysilane in order to introduce bromine groups on the particles surface which were converted to azide groups by the reaction with sodium azide. Acetylene functionalized poly(ethylene glycol) (a-PEG) and poly(ε-caprolactone) (a-PCL) were synthesized and grafted onto the surface of azide functionalized NPs via “click” reaction to obtain magnetic NPs. Success of the different functionalization processes at different stages was studied using Fourier Transform infrared spectroscopy (FTIR). The morphologies of magnetic NPs were further investigated by transmission electron microscopy (TEM). The magnetization and superparamagnetic behavior of naked Fe₃O₄ NPs and coated NPs at room temperature was investigated by the measurement of hysteresis curves using a Vibrating Sample Magnetometer (VSM).     

The synthesis and characterization of electrical and magnetic nanocomposite: PEDOT/PSS–Fe3O4

The poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate)–Fe₃O₄ (PEDOT/PSS–Fe₃O₄) nanoparticles have been prepared by using polystyrene sulfonic sodium (NaPSS) as a dispersant and dopant. The characterization of nanocomposites was investigated by transmission electron microscope, X-ray diffraction, UV spectroscopy, electrochemical study, four-probe, thermogravimetric analysis and magnetic property measurement system. XRD revealed the presence of spinel phase of Fe₃O₄ and the average size was calculated to be about 12 nm. The conductivity of nanocomposites at room temperature is excellent and it depends on the Fe₃O₄ content. The thermal stability of composites is outstanding. Higher saturation magnetization of 6.47 emu g⁻¹ (20 wt.% Fe₃O₄) was observed at 300 K.     

Preparation and characterization of poly(acrylonitrile-co-acrylic acid) nanofibrous composites with Fe3O4 magnetic nanoparticles

Nanofibrous composites are a new class of polymer materials with controlled and tailored properties. Novel Fe₃O₄/poly(acrylonitrile-co-acrylic acid) nanofibrous composites with magnetic behavior have been prepared by a simple electrospinning process. The nanofibrous composites were characterized by X-ray diffraction, field emission scanning electron microscopy and vibrating sample magnetometer. The distribution of Fe₃O₄ nanoparticles inside the nanofibrous composites was investigated by field emission scanning electron microscopy. X-ray diffraction revealed the presence of Fe₃O₄ nanoparticles in the nanofibrous composites. The maximum saturation magnetization for the composites, measured at 300 K, was 30.51 emu/g.     

Preparation and characterization of thermo-, pH-, and magnetic-field-responsive organic/inorganic hybrid microgels based on poly(ethylene glycol)

Nanocomposite microgels are a new class of intelligent materials because of their fast response time, large surface area, and so on. In this study, we demonstrate a new kind of multiple stimulus-responsive organic/inorganic hybrid microgels by combining dual stimuli-responsive poly(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol)methacrylate-co-acrylic acid) (PMOA) microgels with magnetic attapulgite/Fe₃O₄ (AT–Fe₃O₄) nanoparticles. AT–Fe₃O₄ nanoparticles were introduced into the dual-responsive (temperature and pH) PMOA microgels network by in situ polymerization. The responsive behaviors, microstructures, and the interaction between AT–Fe₃O₄ and PMOA microgels matrix of the prepared microgels were systematically characterized using field emission scanning electron microscopy, particle size and Zeta potential analyzer, vibrating sample magnetometer, and Fourier transform infrared spectroscopy. The results showed that the AT–Fe₃O₄ nanoparticles dispersed well in the microgel matrix, and the nanoparticles could be stably present in PMOA without phase separation because of the hydrogen bond (H-bond) interactions between AT–Fe₃O₄ nanoparticles and PMOA matrix. In addition, the multifunctional AT–Fe₃O₄/PMOA nanocomposite microgels had both temperature/pH sensitivity and magnetic functionality.     

Preparation and characterization of PNIPAAm-b-PLA/Fe3O4 thermo-responsive and magnetic composite micelles

Novel magnetic micelles with the flowerlike morphology were prepared with Fe₃O₄ nanoparticles and poly(N-isopropylacrylamide)-block-polylactide (PNIPAAm-b-PLA) copolymers by a dialysis method. The diameter of flowerlike micelles was about 1 μm. The core and shell of the micelles were hydrophilic, while the other area of the micelles was hydrophobic. The lower critical solution temperature (LCST) of PNIPAAm-b-PLA was about 38 °C. The magnetic intensity of Fe₃O₄ nanoparticles decreased after they were encapsulated into PNIPAAm-b-PLA micelles. Thermo-responsive and magnetic properties of the micelles would provide useful applications in the target drug delivery and release system.     

Zinc-doped ferrite nanoparticles as magnetic recyclable catalysts for scale-up glycolysis of poly(ethylene terephthalate) wastes

Innovations of catalyst design are critical to industrial implementation of poly(ethylene terephthalate) (PET) upcycling by glycolysis. A primary challenge that affects the purity of products and increases the recycling cost is the difficulty in catalyst separation and reusability. Here, magnetically isolable zinc ferrite nanoparticles (Zn-MNPs) were prepared and fabricated for higher catalytic activity in PET glycolysis. Results reveal that the substitution of zinc into the spinel structure of Fe₃O₄ significantly enhances its catalytic selectivity in PET glycolysis. Besides, the Zn-rich surface and hollow internal structure of the prepared catalysts create more active sites for reactants, relative to pure Fe₃O₄. Under mild conditions, PET chains experienced a powerful nucleophilic attack from ethylene glycol when catalyzed by Zn-MNPs, achieving 79.82% monomer yield and 100% PET degradation in 2 h with low consumption of ethylene glycol. The recovered catalysts can be reused for five consecutive cycles with high PET conversion. It is anticipated that the synthesized low-cost and recoverable Zn-MNPs are promising alternatives for the industrial upcycling of PET wastes.     

Rheological Tunable Magnetic Fluids with Long-Term Stability

Magnetic fluids have advantages such as flow ability and solid-like property in strong magnetic fields, but have to suffer from the tradeoff between suspension stability and flow resistance. In this work, a thermal/photo/magnetorheological water-based magnetic fluid is fabricated by using oleic acid-coated Fe₃O₄ (Fe₃O₄@OA) nanoparticles as the magnetic particles and the amphiphilic penta block copolymer (PTMC-F127-PTMC)-based aqueous solution as the carrier fluid. Due to the hydrophobic self-assembly between Fe₃O₄@OA and PTMC-F127-PTMC, the Newtonian-like magnetic fluid has outstanding long-term stability and reversible rheological changes between the low-viscosity flow state and the 3D gel structure. In the linear viscoelastic region, the viscosity exhibits an abrupt increase from below 0.10 Pa s at 20 °C to ≈1.3 × 10⁴ Pa s at 40 °C. Benefitting from the photothermal and magnetocaloric effects of the Fe₃O₄@OA nanoparticles, the rheological change process also can be controlled by near infrared light and alternating magnetic field, which endows the magnetic fluid with the applications in the fields of mobile valves, moveable switches, buffer or damping materials in sealed devices, etc.     

Synthesis and characterization of core–shell magnetic molecularly imprinted polymer nanoparticles for selective extraction of tizanidine in human plasma

In this study, simple, effective and general processes were used for the synthesis of a new nano-molecularly imprinted polymers (MIPs) layer on magnetic Fe₃O₄ nanoparticles (NPs) with uniform core–shell structure by combining surface imprinting and nanotechniques. The first step for the synthesis of magnetic NPs was co-precipitation of Fe²⁺ and Fe³⁺ in an ammonia solution. Then, an SiO₂ shell was coated on the magnetic core with the Stöber method. Subsequently, the C=C groups were grafted onto the silica-modified Fe₃O₄ surface by 3-(trimethoxysilyl) propyl methacrylate. Finally, MIPs films were formed on the surface of Fe₃O₄@SiO₂ by the copolymerization of C=C end groups with methacrylic acid (functional monomer), ethylene glycol dimethacrylate (cross-linker), 2,2-azobisisobutyronitrile (initiator) and tizanidine (template molecule). The products were characterized using techniques that included Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermo gravimetric analysis (TGA), scanning electron microscopy (SEM), UV spectrophotometry, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). Measurement of tizanidine through use of the core–shell magnetic molecularly imprinted polymers nanoparticles (MMIPs-NPs) in human plasma samples compared to the paracetamol showed that the synthesized nanosized MMIP for tizanidine has acted selectively.     

Synthesis of chitosan/poly (ethylene glycol)-modified magnetic nanoparticles for antibiotic delivery and their enhanced anti-biofilm activity in the presence of magnetic field

Biocompatible Fe₃O₄/chitosan (CS)/poly (ethylene glycol) (PEG)/gentamicin (Gent) magnetic nanoparticles, namely Fe₃O₄@PEG-Gent NPs, have been successfully developed for antibiotic delivery. In which, PEG dicarboxylic acid was used to modify Fe₃O₄ NPs for good dispersity as well as offer sufficient carboxyl groups as binding sites. And then the free Gent was facilely loaded onto Fe₃O₄ NPs so as to achieve powerful antibacterial activity via electrostatic interactions. Under acidic condition, the CS and PEG of Fe₃O₄@PEG-Gent were protonated to introduce the positive charge to NPs surface, thus facilitating the contact with negatively charged bacterial cell membrane. What is more, the stretches of CS chains triggered by acidic pH may prevent the antimicrobial efficiency of Gent from weakening. Compared with the free antibiotic, these nanocomposites presented better antimicrobial efficacy against gram-positive bacteria S. aureus under acidic condition. Intriguingly, the confocal laser scanning macroscopy imaging suggested that the anti-biofilm efficacy of nanocomposites was significantly enhanced in the presence of an external magnetic field. Due to the superparamagnetic performance of Fe₃O₄ NPs, these nanocomposites were allowed deeper penetration into a mature biofilm of S. aureus by magnetic field, leading to an effective Gent delivery for eradication of biofilm. The ingenious fabrication of the antibiotic delivery system not only efficiently improved the effectiveness and bioavailability of Gent at acidic media, but also provided an innovative platform to treat bacterial biofilms-associated infection by applying extra environmental factors such as magnetic field.     

Red Blood Cell Membrane as a Biomimetic Nanocoating for Prolonged Circulation Time and Reduced Accelerated Blood Clearance

For decades, poly(ethylene glycol) (PEG) has been widely incorporated into nanoparticles for evading immune clearance and improving the systematic circulation time. However, recent studies have reported a phenomenon known as “accelerated blood clearance (ABC)” where a second dose of PEGylated nanomaterials is rapidly cleared when given several days after the first dose. Herein, we demonstrate that natural red blood cell (RBC) membrane is a superior alternative to PEG. Biomimetic RBC membrane‐coated Fe₃O₄ nanoparticles (Fe₃O₄@RBC NPs) rely on CD47, which is a “don't eat me” marker on the RBC surface, to escape immune clearance through interactions with the signal regulatory protein‐alpha (SIRP‐α) receptor. Fe₃O₄@RBC NPs exhibit extended circulation time and show little change between the first and second doses, with no ABC suffered. In addition, the administration of Fe₃O₄@RBC NPs does not elicit immune responses on neither the cellular level (myeloid‐derived suppressor cells (MDSCs)) nor the humoral level (immunoglobulin M and G (IgM and IgG)). Finally, the in vivo toxicity of these cell membrane‐camouflaged nanoparticles is systematically investigated by blood biochemistry, hematology testing, and histology analysis. These findings are significant advancements toward solving the long‐existing clinical challenges of developing biomaterials that are able to resist both immune response and rapid clearance.     

Preparation and characterization of hollow Fe3O4/SiO2@PEG–PLA nanoparticles for drug delivery

In this study we present a novel targeted anticancer drug delivery, which was size controlled Fe₃O₄/SiO₂ hollow microspheres (HMS) as magnetic core and poly (ethylene glycol)-poly–(d,l-lactide) (PEG–PLA) surface coating (HMS@PEG–PLA). And investigations were to test a new convenient method, which is one-step precipitation polymerization on HMS, forming magnetic hollow polymer microspheres. The HMS@PEG–PLA which have hollow structure and uniform size were characterized by Transmission Electron Microscopy (TEM). Vibrating Sample Magnetometer (VSM) showed a characteristic of super paramagnetic with saturation magnetization value of about 19.78 emu/g. In vitro cytotoxicity of Fe₃O₄/SiO₂@PEG–PLA (HMS@PEG–PLA) hollow microspheres were of low toxicity, so it can be used as a drug carrier, and cisplatin (CDDP) as the model drug release behavior was researched. The results have exhibited preferable release properties.     

A facile route to synthesis of superparamagnetic Fe3O4–PDVB nanoworms

Fe₃O₄–polydivinylbenzene (PDVB) nanoworms were firstly synthesized by precipitation polymerization of divinylbenzene in the presence of oleic acid coated iron oxide nanoparticles. The nanoworms had superparamagnetic properties at room temperature, but ferromagnetism at 5 K. Thermogravimetric analysis curves indicated that in comparison with magnetic nanoparticles, the weight percent of iron oxide in nanoworms was slightly declined due to the formation of Fe₃O₄–PDVB nanocomposites. The superparamagnetic nanoworms could be well dispersed in ethanol, and were capable of easy separation by an external magnetic field. Overall, this provided a valuable methodology for preparation of elongated magnetic nanoparticles with high surface-to-volume ratio, which had potential applications in drug delivery/targeting, magnetic resonance imaging, and nanoprobes for diagnosis and disease treatment.     

Facile fabrication of ZnLa0.02Fe1.98O4/PPy and application in water treatment

A core–shell structure of magnetic ZnLa_0.02Fe_1.98O₄/Polypyrrole (PPy) nanoparticles (NPs) was facilely fabricated at room temperature, in which FeCl₃ was used as an initiator. Dodecyl sulfate anions (SDS) were adsorbed onto the outer surface of the ZnLa_0.02Fe_1.98O₄ through the charge compensation. The absorbed SDS induced the adhesion of the PPy to the surface of the ZnLa_0.02Fe_1.98O₄ along with polymerization. The as-prepared composite shows better performance in removal of pollutants like methyl orange (MO) from water by adsorption than that of the ZnLa_0.02Fe_1.98O₄. The adsorption experiments indicated that the adsorption was divided into two processes. The maximum adsorption capacity for MO was determined to be 76.34 mg/g. The experimental data fit the Langmuir model implying the single layer adsorption. The adsorption process was described by the pseudo-second-order kinetic model. The adsorption of MO onto the ZnLa_0.02Fe_1.98O₄/PPy was exothermic process, and the randomness decreased at the process. To decrease experimental temperature is suitable for the adsorption of MO onto the ZnLa_0.02Fe_1.98O₄/PPy.     

High T2-relaxation and biocompatible magnetic nanofluids with poly(amino acid) coating

A facile one-pot method has been developed to prepare poly(amino acid) functionalized, water-stable, biocompatible, and superparamagnetic iron oxide nanoparticles (NPs) with small diameters of ∼10 nm. The obtained biocompatible magnetic nanoparticles capped with polyaspartic acid (PASP) exhibit a relatively high saturation magnetization (57.1 emu/g) and a much strong magnetic resonance (MR) T₂ relaxation effect with the transverse relaxivity coefficient (r₂) as high as 302.6 s⁻¹ mM⁻¹. Interestingly, the as-prepared Fe₃O₄@PASP NPs are highly stable in aqueous solution and demonstrate the property of magnetic nanofluids. The high T₂ effect, good water-stability, superparamagnetization, biocompatibility and bioconjugatability render the as-synthesized Fe₃O₄@PASP NPs great desirable for bioapplications such as magnetic resonance imaging (MRI), bioseparation, targeted drug delivery, and so on.     

One-pot fabrication of magnetic nanocomposite microcapsules

Fe₂O₃ nanoparticles can self-assembly at liquid-liquid interfaces to form stable water-in-oil Pickering emulsions. Novel magnetic and thermo-sensitive microcapsules were one-pot fabricated by radical polymerization of N-isopropylacrylamide (NIPAm) at the aqueous phases of Pickering emulsions at 60 °C. The obtained PNIPAm was deposited from the water phases onto the interfaces of water-in-oil Pickering emulsions to form Fe₂O₃/PNIPAm nanocomposite shells because of its hydrophobicity at this reaction temperature. Pickering emulsion polymerization opens up a new route to fabricate a variety of hollow and hybrid microcapsules.     

Multifunctional Magnetic–Optical Nanoparticle Probes for Simultaneous Detection,Separation, and Thermal Ablation of Multiple Pathogens

Multifunctional nanoparticles possessing magnetization and near‐infrared (NIR) absorption have warranted interest due to their significant applications in magnetic resonance imaging, diagnosis, bioseparation, target delivery, and NIR photothermal ablation. Herein, the site‐selective assembly of magnetic nanoparticles onto the ends or ends and sides of gold nanorods with different aspect ratios (ARs) to create multifunctional nanorods decorated with varying numbers of magnetic particles is described for the first time. The resulting hybrid nanoparticles are designated as Fe₃O₄? Au_rod? Fe₃O₄ nanodumbbells and Fe₃O₄? Au_rod necklacelike constructs with tunable optical and magnetic properties, respectively. These hybrid nanomaterials can be used for multiplex detection and separation because of their tunable magnetic and plasmonic functionality. More specifically, Fe₃O₄? Au_rod necklacelike probes of different ARs are utilized for simultaneous optical detection based on their plasmon properties, magnetic separation, and photokilling of multiple pathogens from a single sample at one time. The combined functionalities of the synthesized probes will open up many exciting opportunities in dual imaging for targeted delivery and photothermal therapy.     

Efficient purification of His-tagged protein by superparamagnetic Fe3O4/Au–ANTA–Co2 + nanoparticles

Superparamagnetic Fe₃O₄/Au nanoparticles were synthesized and surface modified with mercaptopropionic acid (MPA), followed by conjugating Nα,Nα-Bis(carboxymethyl)-l-lysine hydrate (ANTA) and subsequently chelating Co^2 +. The resulting Fe₃O₄/Au–ANTA–Co^2 + nanoparticles have an average size of 210 nm in aqueous solution, and a magnetization of 36 emu/g, endowing the magnetic nanoparticles with excellent magnetic responsivity and dispersity. The Co^2 + ions in the magnetic nanoparticle shell provide docking site for histidine, and the Fe₃O₄/Au–ANTA–Co^2 + nanoparticles exhibit excellent performance in binding of a His-tagged protein with a binding capacity of 74 μg/mg. The magnetic nanoparticles show highly selective purification of the His-tagged protein from Escherichia coli lysate. Therefore, the obtained Fe₃O₄/Au–ANTA–Co^2 + nanoparticles exhibited excellent performance in the direct separation of His-tagged protein from cell lysate.