Cationic Magnetic Nanoparticles Research Articles

Demulsification Performance and Mechanism of Tertiary Amine Polymer-Grafted Magnetic Nanoparticles in Surfactant-Free Oil-in-Water Emulsion.

Numerous cationic magnetic nanoparticles (MNPs) have previously been developed for demulsifying oil-in-water (O/W) emulsion, and results showed that the cationic MNPs could effectively flocculate and remove the negatively charged oil droplets via charge attraction; however, to the best of our knowledge, there are no research reports regarding the synergetic influence of both the positive charge density and interfacial activity of MNPs on the demulsification performance. In this study, three tertiary amine polymer-grafted MNPs, namely, poly(2-dimethylaminoethyl acrylate)-grafted MNPs (M-PDMAEA), poly(2-dimethylamino)ethyl methacrylate)-grafted MNPs (M-PDMAEMA), and poly(2-diethylaminoethyl methacrylate)-grafted MNPs (M-PDEAEMA), were synthesized and evaluated for their demulsification performance. Results demonstrated that a high positive charge density and superior interfacial activity of MNPs could cause partial oil droplet re-dispersion when excessive MNPs were introduced, leading to a lower magnetic separation efficiency and narrower demulsification window. Herein, a demulsification window is defined as a range of nanoparticle dosages in which the MNPs can effectively demulsify the O/W emulsion under certain conditions. For highly positively charged MNPs, their good interfacial activity could aggravate the formation of a narrower demulsification window. When tertiary amine polymer-grafted MNPs carried a lower positive charge density or weak interfacial activity, that is, M-PDMAEA at pH 4.0, M-PDMAEMA at pH 5.0-9.0, and M-PDEAEMA at pH 9.0-10.0, wide demulsification windows were observed. Additionally, a recycling experiment suggested that MNPs could maintain high demulsification efficiency up to at least five cycles, indicating their satisfactory recyclability. The three tertiary amine polymer-grafted MNPs can be potentially used for efficient demulsification from surfactant-free O/W emulsion in various pH ranges.

Synthesis and application of magnetic nanoparticles (MNPs) in siRNA delivery to the retina

AbstractIntroductionSmall interfering RNA (siRNA) is an important RNA interference tool that has found significant application in ocular therapy. For this reason, there is a considerable demand of siRNA delivery platforms able to effectively transfect cells within the retina. Up to now several strategies have been investigated for this application such as lipids, nanoparticles and polymers but in all the cases invasive injections are the only administration routes explored. Moreover, a major limitation shared by all these delivery systems is the lack of active targeting toward the posterior segment of the eye that hampers high transfection efficiencies.PurposeWe aim to synthesize and formulate a new magnetic nanoparticles‐mediated delivery technology that shall allow safe and efficient siRNA delivery to the retina assisted by magnetic targeting.Methods(1) Cationic MNPs have been synthesized, characterized, and their ability to form complexes with siRNA has been demonstrated by Zeta Potential. (2) The in vitro MNPs mediated gene silencing have been tested on green fluorescent protein (GFP)‐stably transfected cells (661W & RPE). Also, gene silencing of the endogenous glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) gene has been monitored. (3) Finally, the in vitro toxicity of the formulations has been determined in term of apoptosis, cell proliferation and protein production.ResultsMNPs were able to efficiently complex siRNA while maintain their size and charge. MNPs complexed with siRNA achieved high transfection efficiency and gene silencing of GFP as shown by fluorescence microscopy and flow cytometry. The knock‐down efficiency has been confirmed by targeting GAPDH by immunohistochemistry. Finally, proliferation, apoptosis and total protein content assays demonstrate the full biocompatibility of these gene delivery platforms.ConclusionsMagnetic nanoparticles are a promising platform for gene therapy in the context of ocular therapy and allow to achieve high transfection efficiencies in retinal cell lines.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska‐Curie grant agreement No 722717.

Multicellular spheroids formation: The synergistic effects of halloysite nanoclay and cationic magnetic nanoparticles

We investigated the influence of halloysite nanotubes and magnetic nanoparticles stabilized by positively charged polyelectrolyte polyallyamine hydrochloride (PAH) on the built-up of multicellular spheroids using cancer and primary cell cultures. We found no adverse effects caused by the nanoparticles investigated on the formation of 3D cell structures. The use of magnetic nanoparticles (MNPs) has allowed controlling the spheroid spatial movement, which may find applications in cell biology, tissue engineering and nanomedicine. We have also shown for the first time that halloysite nanotubes do not affect the formation of spheroids, including those formed from mesenchymal stem cells.

Cationized Magnetoferritin Enables Rapid Labeling and Concentration of Gram-Positive and Gram-Negative Bacteria in Magnetic Cell Separation Columns.

ABSTRACTIn order to identify pathogens rapidly and reliably, bacterial capture and concentration from large sample volumes into smaller ones are often required. Magnetic labeling and capture of bacteria using a magnetic field hold great promise for achieving this goal, but the current protocols have poor capture efficiency. Here, we present a rapid and highly efficient approach to magnetic labeling and capture of both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria using cationized magnetoferritin (cat-MF). Magnetic labeling was achieved within a 1-min incubation period with cat-MF, and 99.97% of the labeled bacteria were immobilized in commercially available magnetic cell separation (MACS) columns. Longer incubation times led to more efficient capture, with S. aureus being immobilized to a greater extent than E. coli. Finally, low numbers of magnetically labeled E. coli bacteria (<100 CFU per ml) were immobilized with 100% efficiency and concentrated 7-fold within 15 min. Therefore, our study provides a novel protocol for rapid and highly efficient magnetic labeling, capture, and concentration of both Gram-positive and Gram-negative bacteria.IMPORTANCE Antimicrobial resistance (AMR) is a significant global challenge. Rapid identification of pathogens will retard the spread of AMR by enabling targeted treatment with suitable agents and by reducing inappropriate antimicrobial use. Rapid detection methods based on microfluidic devices require that bacteria are concentrated from large volumes into much smaller ones. Concentration of bacteria is also important to detect low numbers of pathogens with confidence. Here, we demonstrate that magnetic separation columns capture small amounts of bacteria with 100% efficiency. Rapid magnetization was achieved by exposing bacteria to cationic magnetic nanoparticles, and magnetized bacteria were concentrated 7-fold inside the column. Thus, bacterial capture and concentration were achieved within 15 min. This approach could be extended to encompass the capture and concentration of specific pathogens, for example, by functionalizing magnetic nanoparticles with antibodies or small molecule probes.

Adsorption Behaviors of Nucleic Acid by Cationic Magnetic Nanoparticles

Cationic magnetic nanoparticles are prepared by covalently binding spermidine and polyethylenimine onto the surface of nanoparticles via a glutaraldehyde coupling method. Nanoparticles modified by spermidine or polyethylenimine were characterized using Fourier-transformed infrared spectra, transmission electron microscopy and scanning electron microscopy. In this study, cationic magnetic nanoparticles were prepared by covalently conjugating cationic ligands onto the surface of nanoparticles. The plasmid DNA adsorption by the surface-modified magnetic nanoparticles was analyzed by Freundlich, Temkin, and Langmuir models. The maximal adsorption capacities in Langmuir model for polyethylenimine- and spermidine- modified nanoparticles are 341 and 116 μg/mg, respectively. Overall, the results demonstrated that the polyethylenimine-modified magnetic nanoparticles has the potential for purification of plasmid.

Synthesis of cationic magnetic nanoparticles and evaluation of their gene delivery efficacy in Hep G2 cells

Well-defined cationic polymers were synthesized via the reversible addition fragmentation chain transfer polymerization and were subsequently used as stabilizer for the synthesis of cationic iron-oxide magnetic nanoparticles via the coprecipitation method. The surface-coated iron-oxide nanoparticles made stable suspension in water and were characterized by a range of techniques such as dynamic light scattering, transmission electron microscopy, and thermogravimetric analysis. The presence of protonated amine and carbohydrate residues onto the surface of the nanoparticles allowed their facile complexation with DNA and the resulting nanocomplexes were then studied for their efficacy as DNA carriers in Hep G2 cells.

The endocytic penetration mechanism of iron oxide magnetic nanoparticles with positively charged cover: A morphological approach

In this study we present a morphological approach in observing the interaction of cationic magnetic nanoparticles with A-549 cells (human lung adenocarcinoma). Under our experimental conditions, nanoparticles easily penetrated cells and were observed in vivo, using bright light microscopy. In fixed cells, nanoparticles remained inside cells, showing quantity and distribution patterns similar to those in unfixed cells. The presence of nanoparticles did not affect cell viability or the morphologic parameters assessed. We determined the potential internalization mechanism of nanoparticles into cells using endocytosis inhibitors. The results suggest that nanoparticles used in this study penetrate A-549 cells mainly through a macropinocytosis process.

Gene transfer using self-assembled ternary complexes of cationic magnetic nanoparticles, plasmid DNA and cell-penetrating Tat peptide

Nonviral magnetofection facilitates gene transfer by using a magnetic field to concentrate magnetic nanoparticle-associated plasmid delivery vectors onto target cells. In light of the well-established effects of the Tat peptide, a cationic cell-penetrating peptide, that enhances the cytoplasmic delivery of a variety of cargos, we tested whether the combined use of magnetofection and Tat-mediated intracellular delivery would improve transfection efficiency. Through electrostatic interaction, gene transfer complexes were generated by mixing polyethylenimine-coated cationic magnetic iron beads with plasmid DNA, followed by addition of a bis(cysteinyl) histidine-rich Tat peptide. These ternary magnetofection complexes provided a 4-fold improvement in transgene expression at a dose of 1 μg of plasmid DNA per 20,000 cells over the binary complexes without the Tat peptide and transfected up to 60% of cells in vitro. The enhanced transfection efficiency was also observed in vivo in the rat spinal cord after lumbar intrathecal injection. Moreover, the injected ternary magnetofection complexes in the cerebrospinal fluid responded to a moving magnetic filed by shifting away from the injection site and mediating transgene expression in a remote region. Thus, our approach could potentially be useful for effective gene therapy treatments of localized diseases.

Substantiating in vivo magnetic brain tumor targeting of cationic iron oxide nanocarriers via adsorptive surface masking

Cationic magnetic nanoparticles are attractive as potential vehicles for tumor drug delivery due to their favorable interactions with both the tumor milieu and the therapeutic cargo. However, systemic delivery of these nanoparticles to the tumor site is compromised by their rapid plasma clearance. We developed a simple method for in vivo protection of cationic nanocarriers, using non-covalent surface masking with a conjugate of low molecular weight heparin and polyethylene glycol. Surface masking resulted in a 11-fold increase in plasma AUC and a 2-fold increase in the magnetic capture of systemically injected nanoparticles in orthotopic rodent brain tumors. Overall, the described methodology could expand the prospective applications for cationic magnetic nanoparticles in magnetically mediated gene/drug delivery.

Magnetic immobilization and electrochemical detection of leukemia K562 cells

A new protocol was proposed for rapid magnetic isolation, immobilization and electrochemical detection of leukemia K562 cells via their decoration with cationic magnetic nanoparticles (CMNPs). The CMNPs (3-aminopropyltriethoxysilane-treated Fe 3O 4) were synthesized in liquid solution and characterized by transmission electron microscopy. After the incubation of pre-cultured leukemia K562 cells in the coexistence of CMNPs for a period of time, the CMNPs modified living cells could be rapidly isolated from the medium and immobilized firmly on the electrode surface via a magnetic field, as traced by quartz crystal microbalance. The cyclic voltammetric experiments of the cells immobilized at glassy carbon electrode exhibited an irreversible anodic current peak whose height is proportional to cell viability, and the 5-fluorouracil cytotoxicity results obtained from the proposed magnetic-electrochemical method were supported by conventional MTT assays. The proposed method is simple, rapid, inexpensive, and convenient in electrode renewal, which is recommended as a promising experimental platform for wider applications in biosensing and cellular researches.