Fabricating Water Dispersible Superparamagnetic Iron Oxide Nanoparticles for Biomedical Applications through Ligand Exchange and Direct Conjugation

In Vitro and In Vivo Biological Assays of Dextran Coated Iron Oxide Aqueous Magnetic Fluids

The iron oxide nanoparticles coated with different surface coatings were studied and characterized by multiple physicochemical and biological methods. The present paper aims at estimating the toxicity in vitro and in vivo of dextran coated iron oxide aqueous magnetic fluids. The in vitro studies were conducted by quantifying the viability of HeLa cells after their incubation with the samples (concentrations of 62.5−125−250−500 μg/mL at different time intervals). The estimation of the toxicity in vivo of administering dextran coated iron oxide aqueous magnetic fluids (DIO-AMF) with hydrodynamic diameter of 25.73 ± 4 nm to Male Brown Norway rats has been made. Different concentrations (62.5−125−250−500 μg/mL) of dextran coated iron oxide aqueous magnetic fluids were administered for 7 consecutive days. Hematology and biochemistry of the Male Brown Norway rats assessment was performed at various time intervals (24−72 h and 21−28 days) after intra-peritoneal injection. The results showed that high concentrations of DIO-AMF (250 and 500 μg/mL) significantly increased white blood cells, red blood cells, hemoglobin and hematocrit compared to the values obtained for the control group (p < 0.05). Moreover, following the administration of DIO-AMF, the levels of alkaline phosphatase and aspartate aminotransferase increased compared to the control group (p < 0.05). After DIO-AMF administration, no significant difference was observed in the levels of alanine aminotransferase, gamma-glutamyl transpeptidase, urea and creatinine compared to the control group (p < 0.05). The results of the present study showed that dextran coated iron oxide aqueous magnetic fluids in concentrations lower than 250 μg/mL are reliable for medical and pharmaceutical applications.

Poly(acrylic acid) capped iron oxide nanoparticles via ligand exchange with antibacterial properties for biofilm applications

Biofilm infections pose a rising threat to public health due to its existing protective shield, which preventing biocide penetration. Here, the oleate-capped iron oxide nanoparticles (OIONPs) were synthesized by the high-temperature method first; after then, the poly(acrylic acid)-capped iron oxide nanoparticles (PIONPs) were obtained via a ligand exchange reaction between OIONPs and sodium poly(acrylic acid). The physicochemical properties of PIONPs were evaluated by Fourier-transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Scanning Transmission Electron Microscopy (STEM), Dynamic Light Scattering (DLS), and zeta potential. The FT-IR analysis confirmed the successful ligand exchange on the surface of iron oxide nanoparticles. STEM images displayed that the prepared PIONPs were monodisperse spherical nanoparticles. The PIONPs were stable in ultrapure water and could be kept for 5 weeks without aggregation. Next, Cell Counting Kit-8 (CCK-8) assay and fluorescent images confirmed the excellent cytocompatibility of PIONPs, while the iron concentration of PIONPs was in the range of 5∼120 mg/L. Finally, PIONPs exhibited efficient antibacterial activity against E. coli and S. aureus, and Staphylococcus aureus subsp. aureus Rosenbach (SASAR) biofilm could be destroyed by treating PIONPs under alternating current (AC) applied field conditions.

Clickable iron oxide NPs based on catechol derived ligands: synthesis and characterization

Clickable magnetic nanoparticles have attracted great attention as potential nanoplatforms for biomedical applications because of the high functionalization efficiency of their surfaces with biomolecules, which facilitates their bio-compatibilization. However, the design and synthesis of clickable NPs is still challenging because of the complexity of the chemistry on the magnetic NP surface, thus robust methods that improve the ligand synthesis and the transfer of magnetic NPs in physiological media being in high-demand. In this work, we developed a versatile and enhanced synthetic route to fabricate potentially clickable IONPs of interest in nanomedicine. Catechol anchor ligands with different stereo-electronic features were synthetized from a hetero bi-functional PEG spacer backbone. The resulting catechol ligands transferred in good yields and high stability to magnetic NPs by an improved energetic ligand exchange method that combines sonication and high temperature. The azido functionalized IONPs exhibited excellent characteristics as T2 MRI contrast agents with low cytotoxicity, making these clickable magnetic NPs promising precursors for nanomedicines.

Macromolecules with Different Charges, Lengths, and Coordination Groups for the Coprecipitation Synthesis of Magnetic Iron Oxide Nanoparticles as T1 MRI Contrast Agents

Considerable efforts have been focused on the exploitation of macromolecule ligands for synthesis of magnetic Fe3O4 nanoparticles as T1 magnetic resonance imaging (MRI) contrast agents, but studies that concern macromolecule ligands with different charges and coordination groups are still limited. Herein, we used poly(acrylic acid) (PAA), poly(allylamine hydrochloride) (PAH), and polyvinyl alcohol (PVA), which possess negative, positive and neutral charges with carboxylic acid, amino and hydroxyl groups respectively, as templates and stabilizers to fabricate Fe3O4 nanoparticles through coprecipitation reaction. The obtained Fe3O4-PAA, Fe3O4-PAH, and Fe3O4-PVA nanoparticles showed T1 contrast performance with r1 relaxivities of 23.4, 60.3, and 30.6 mM s-1 at 0.5 T (25 °C), and a r2/r1 ratio of 2.62, 3.82, and 7.26, respectively. The cell viability assay revealed that Fe3O4-PAA and Fe3O4-PVA exhibited good biocompatibility, while Fe3O4-PAH displayed high cytotoxicity. In vivo T1-weighted (1 T) mice showed that both Fe3O4-PAA and Fe3O4-PVA were able to display remarkably brighten the contrast enhancement for the mice tumor and kidney sites, but Fe3O4-PAA had better contrast performance. This work highlights that the macromolecule ligands play an important role in the biocompatibility and T1 contrast performance of magnetic Fe3O4 nanoparticles.

Highly Magnetizable Crosslinked Chloromethylated Polystyrene-Based Nanocomposite Beads for Selective Molecular Separation of 4-Aminobenzoic Acid

In this work, we describe the preparation and characterization of highly magnetizable chloromethylated polystyrene-based nanocomposite beads. For synthesis optimization, acid-resistant core-shelled maghemite (γ-Fe₂O₃) nanoparticles are coated with sodium oleate and directly incorporated into the organic medium during a suspension polymerization process. A crosslinking agent, ethylene glycol dimethacrylate, is used for copolymerization with 4-vinylbenzyl chloride to increase the resistance of the microbeads against leaching. X-ray diffraction, inductively coupled plasma atomic emission spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and optical microscopy are used for bead characterization. The beads form a magnetic composite consisting of ∼500 nm-sized crosslinked polymeric microspheres, embedding ∼8 nm γ-Fe₂O₃ nanoparticles. This nanocomposite shows large room temperature magnetization (∼24 emu/g) due to the high content of maghemite (∼45 wt %) and resistance against leaching even in acidic media. Moreover, the presence of superficial chloromethyl groups is probed by Fourier transform infrared and X-ray photoelectron spectroscopy. The nanocomposite beads displaying chloromethyl groups can be used to selectively remove aminated compounds that are adsorbed on the beads, as is shown here for the molecular separation of 4-aminobenzoic acid from a mixture with benzoic acid. The high magnetization of the composite beads makes them suitable for in situ molecular separations in environmental and biological applications.

Nano-mediated delivery of double-stranded RNA for gene therapy of glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common type of malignant gliomas, characterized by genetic instability, intratumoral histopathological variability and unpredictable clinical behavior. Disappointing results in the treatment of gliomas with surgery, radiation and chemotherapy have fueled a search for new therapeutic targets and treatment modalities. Here we report new approach towards RNA interference therapy of glioblastoma multiforme based on the magnetic nanoparticles delivery of the double-stranded RNA (dsRNA) with homological sequences to mRNA of tenascin-C (TN-C), named ATN-RNA. The obtained nanocomposite consisted of polyethyleneimine (PEI) coated magnetic nanoparticles conjugated to the dsRNA show high efficiency in ATN-RNA delivery, resulting not only in significant TN-C expression level suppressesion, but also impairing the tumor cells migration. Moreover, synthesized nanomaterials show high contrast properties in magnetic resonance imaging (MRI) and low cytotoxicity combining with lack of induction of interferon response. We believe that the present work is a successful combination of effective, functional, non-immunostimulatory dsRNA delivery system based on magnetic nanoparticles with high potential for further application in GBM therapy.

Surface Functionalization of Iron Oxide Nanoparticles with Gallic Acid as Potential Antioxidant and Antimicrobial Agents

In this research, we report the size-controlled synthesis and surface-functionalization of magnetite with the natural antioxidant gallic acid (GA) as a ligand, using in situ and post-synthesis methods. GA functionalization provided narrow size distribution, with an average particle size of 5 and 8 nm for in situ synthesis of gallic acid functionalized magnetite IONP@GA1 and IONP@GA2, respectively, which are ultra-small particles as compared to unfunctionalized magnetite (IONP) and post functionalized magnetite IONP@GA3 with average size of 10 and 11 nm respectively. All the IONPs@GA samples were found hydrophilic with stable aggregation state. Prior to commencement of experimental lab work, PASS software was used to predict the biological activities of GA and it is found that experimental antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and antimicrobial studies using well diffusion method are in good agreement with the simulated results. Furthermore, the half maximal inhibitory concentration (IC50) values of DPPH antioxidant assay revealed a 2-4 fold decrease as compared to unfunctionalized IONP. In addition to antioxidant activity, all the three IONP@GA proved outstanding antimicrobial activity while testing on different bacterial and fungal strains. The results collectively indicate the successful fabrication of novel antioxidant, antimicrobial IONP@GA composite, which are magnetically separable, efficient, and low cost, with potential applications in polymers, cosmetics, and biomedical and food industries.

Tuning Properties of Iron Oxide Nanoparticles in Aqueous Synthesis without Ligands to Improve MRI Relaxivity and SAR

Aqueous synthesis without ligands of iron oxide nanoparticles (IONPs) with exceptional properties still remains an open issue, because of the challenge to control simultaneously numerous properties of the IONPs in these rigorous settings. To solve this, it is necessary to correlate the synthesis process with their properties, but this correlation is until now not well understood. Here, we study and correlate the structure, crystallinity, morphology, as well as magnetic, relaxometric and heating properties of IONPs obtained for different durations of the hydrothermal treatment that correspond to the different growth stages of IONPs upon initial co-precipitation in aqueous environment without ligands. We find that their properties were different for IONPs with comparable diameters. Specifically, by controlling the growth of IONPs from primary to secondary particles firstly by colloidal and then also by magnetic interactions, we control their crystallinity from monocrystalline to polycrystalline IONPs, respectively. Surface energy minimization in the aqueous environment along with low temperature treatment is used to favor nearly defect-free IONPs featuring superior properties, such as high saturation magnetization, magnetic volume, surface crystallinity, the transversal magnetic resonance imaging (MRI) relaxivity (up to r₂ = 1189 mM⁻¹·s⁻¹ and r₂/r₁ = 195) and specific absorption rate, SAR (up to 1225.1 W·g_Fe⁻¹).

Release of Doxorubicin by a Folate-Grafted, Chitosan-Coated Magnetic Nanoparticle

In clinical tumor therapy, chemotherapeutic routes have caused severe side effects; current delivery methods are unsatisfactory. Successful design of a remotely folate (FA)-grafted chitosan (CS)-coated magnetic nanoparticle (MNP) with low toxicity, has been achieved. A chemotherapeutic drug such as doxorubicin (DOX), is loaded in the MNP-based matrix (FA-grafted CS-DOX-_TPP-MNP), which is coated by an activated target tumor molecule of FA-grafted CS biopolymer with the inclusion of tripolyphosphate (TPP) as a linker. The resultant nano-complexes exhibited random aggregates (~240 nm) and zeta potential (−24.9 mV). In vivo experiments using athymic BALB/c nude mice with human glioblastoma U87 cells in a subcutaneous tumor model revealed that magnetic guidance of FA-grafted CS-DOX-_TPP-MNP, injected via the tail vein, significantly decreased tumor growth. This manuscript demonstrates the feasibility of magnetizing control of FA-grafted CS-DOX-_TPP-MNP to enhance the localization of drug release.

Polyelectrolyte coating on superparamagnetic iron oxide nanoparticles as interface between magnetic core and biorelevant media

Nanoparticles do not exist in thermodynamical equilibrium because of high surface free energy, thus they have only kinetic stability. Spontaneous changes can be delayed by designed surface coating. In biomedical applications, superparamagnetic iron oxide nanoparticles (SPIONs) require an optimized coating in order to fulfil the expectation of medicine regulatory agencies and ultimately that of biocompatibility. In this work, we show the high surface reactivity of naked SPIONs due to ≡Fe-OH sites, which can react with H⁺/OH^- to form pH- and ionic strength-dependent charges. We explain the post-coating of naked SPIONs with organic polyacids via multi-site complex bonds formed spontaneously. The excess polyacids can be removed from the medium. The free COOH groups in coating are prone to react with active biomolecules like proteins. Charging and pH- and salt-dependent behaviour of carboxylated SPIONs were characterized quantitatively. The interrelation between the coating quality and colloidal stability measured under biorelevant conditions is discussed. Our coagulation kinetics results allow us to predict colloidal stability both on storage and in use; however, a simpler method would be required to test SPION preparations. Haemocompatibility tests (smears) support our qualification for good and bad SPION manufacturing; the latter 'promises' fatal outcome in vivo.

Surface engineering of SPIONs: role of phosphonate ligand multivalency in tailoring their efficacy

We report the design of scaffolds containing mono-, bis-, and tris-phosphonate coordinating groups, and a polyethylene glycol chain, for stabilizing superparamagnetic iron oxide nanoparticles (SPIONs), using simple and versatile chemistry. We demonstrate that the number of anchoring phosphonate sites on the ligand influence the colloidal stability, magnetic and biological properties of SPIONs, and the latter do not solely depend on attaching moieties that can enhance their aqueous dispersion. These parameters can be tailored by the number of conjugation sites on the ligand, as evidenced from dynamic light scattering at various salt concentrations, magnetic relaxivities and cell viability studies.