Stabilization and functionalization of iron oxide nanoparticles for biomedical applications

Biocompatible coated magnetosome minerals with various organization and cellular interaction properties induce cytotoxicity towards RG-2 and GL-261 glioma cells in the presence of an alternating magnetic field

Background

Biologics magnetics nanoparticles, magnetosomes, attract attention because of their magnetic characteristics and potential applications. The aim of the present study was to develop and characterize novel magnetosomes, which were extracted from magnetotactic bacteria, purified to produce apyrogen magnetosome minerals, and then coated with Chitosan, Neridronate, or Polyethyleneimine. It yielded stable magnetosomes designated as M-Chi, M-Neri, and M-PEI, respectively. Nanoparticle biocompatibility was evaluated on mouse fibroblast cells (3T3), mouse glioblastoma cells (GL-261) and rat glioblastoma cells (RG-2). We also tested these nanoparticles for magnetic hyperthermia treatment of tumor in vitro on two tumor cell lines GL-261 and RG-2 under the application of an alternating magnetic field. Heating, efficacy and internalization properties were then evaluated.

Results

Nanoparticles coated with chitosan, polyethyleneimine and neridronate are apyrogen, biocompatible and stable in aqueous suspension. The presence of a thin coating in M-Chi and M-PEI favors an arrangement in chains of the magnetosomes, similar to that observed in magnetosomes directly extracted from magnetotactic bacteria, while the thick matrix embedding M-Neri leads to structures with an average thickness of 3.5 µm² per magnetosome mineral. In the presence of GL-261 cells and upon the application of an alternating magnetic field, M-PEI and M-Chi lead to the highest specific absorption rates of 120–125 W/g_Fe. Furthermore, while M-Chi lead to rather low rates of cellular internalization, M-PEI strongly associate to cells, a property modulated by the application of an alternating magnetic field.

Conclusions

Coating of purified magnetosome minerals can therefore be chosen to control the interactions of nanoparticles with cells, organization of the minerals, as well as heating and cytotoxicity properties, which are important parameters to be considered in the design of a magnetic hyperthermia treatment of tumor.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-017-0293-2) contains supplementary material, which is available to authorized users.

Multilayered Magnetic Nanobeads for the Delivery of Peptides Molecules Triggered by Intracellular Proteases

In this work, the versatility of layer-by-layer technology was combined with the magnetic response of iron oxide nanobeads to prepare magnetic mesostructures with a degradable multilayer shell into which a dye quenched ovalbumin conjugate (DQ-OVA) was loaded. The system was specifically designed to prove the protease sensitivity of the hybrid mesoscale system and the easy detection of the ovalbumin released. The uptake of the nanostructures in the breast cancer cells was followed by the effective release of DQ-OVA upon activation via the intracellular proteases degradation of the polymer shells. Monitoring the fluorescence rising due to DQ-OVA digestion and the cellular dye distribution, together with the electron microscopy studying, enabled us to track the shell degradation and the endosomal uptake pathway that resulted in the release of the digested fragments of DQ ovalbumin in the cytosol.

Acetate-Induced Disassembly of Spherical Iron Oxide Nanoparticle Clusters into Monodispersed Core-Shell Structures upon Nanoemulsion Fusion

It has been long known that the physical encapsulation of oleic acid-capped iron oxide nanoparticles (OA-IONPs) with the cetyltrimethylammonium (CTA+) surfactant induces the formation of spherical iron oxide nanoparticle clusters (IONPCs). However, the behavior and functional properties of IONPCs in chemical reactions have been largely neglected and are still not well-understood. Herein, we report an unconventional ligand-exchange function of IONPCs activated when dispersed in an ethyl acetate/acetate buffer system. The ligand exchange can successfully transform hydrophobic OA-IONP building blocks of IONPCs into highly hydrophilic, acetate-capped iron oxide nanoparticles (Ac-IONPs). More importantly, we demonstrate that the addition of silica precursors (tetraethyl orthosilicate and 3-aminopropyltriethoxysilane) to the acetate/oleate ligand-exchange reaction of the IONPs induces the disassembly of the IONPCs into monodispersed iron oxide-acetate-silica core-shell-shell (IONPs@acetate@SiO2) nanoparticles. Our observations evidence that the formation of IONPs@acetate@SiO2 nanoparticles is initiated by a unique micellar fusion mechanism between the Pickering-type emulsions of IONPCs and nanoemulsions of silica precursors formed under ethyl acetate buffered conditions. A dynamic rearrangement of the CTA+-oleate bilayer on the IONPC surfaces is proposed to be responsible for the templating process of the silica shells around the individual IONPs. In comparison to previously reported methods in the literature, our work provides a much more detailed experimental evidence of the silica-coating mechanism in a nanoemulsion system. Overall, ethyl acetate is proven to be a very efficient agent for an effortless preparation of monodispersed IONPs@acetate@SiO2 and hydrophilic Ac-IONPs from IONPCs.

Fabrication of 3-methoxyphenol sensor based on Fe3O4 decorated carbon nanotube nanocomposites for environmental safety: Real sample analyses

Iron oxide ornamented carbon nanotube nanocomposites (Fe3O4.CNT NCs) were prepared by a wet-chemical process in basic means. The optical, morphological, and structural characterizations of Fe3O4.CNT NCs were performed using FTIR, UV/Vis., FESEM, TEM; XEDS, XPS, and XRD respectively. Flat GCE had been fabricated with a thin-layer of NCs using a coating binding agent. It was performed for the chemical sensor development by a dependable I-V technique. Among all interfering analytes, 3-methoxyphenol (3-MP) was selective towards the fabricated sensor. Increased electrochemical performances for example elevated sensitivity, linear dynamic range (LDR) and continuing steadiness towards selective 3-MP had been observed with chemical sensor. The calibration graph found linear (R2 = 0.9340) in a wide range of 3-MP concentration (90.0 pM ~ 90.0 mM). The limit of detection and sensitivity were considered as 1.0 pM and 9×10-4 μAμM-1cm-2 respectively. The prepared of Fe3O4.CNT NCs by a wet-chemical progression is an interesting route for the development of hazardous phenolic sensor based on nanocomposite materials. It is also recommended that 3-MP sensor is exhibited a promising performances based on Fe3O4.CNT NCs by a facile I-V method for the significant applications of toxic chemicals for the safety of environmental and health-care fields.

Detailed toxicity evaluation of β-cyclodextrin coated iron oxide nanoparticles for biomedical applications

The application of iron oxide nanoparticles [IONPs] in biomedical research is progressively increasing, leading to the rapid development of biocompatible and surface modified IONPs. However, there is still a need of information pertaining to its cellular and acute toxicity profile. This work reports the synthesis of β-cyclodextrin coated iron oxide nanoparticles (βCD-IONPs) and their characterization using spectroscopic (FT-IR), thermal (TGA) and surface analysis (TEM, SEM, BET and Zeta potential). All the characterization techniques displayed the synthesis of well dispersed, rod shaped βCD-IONPs of 45nm. Time dependent cellular uptake of these nanoparticles was also evaluated using Prussian blue staining. Further, cytocompatibility analysis was executed in mouse fibroblast cell line (NIH 3T3) using MTT and LDH assays, respectively which did not show any cytotoxic indications of βCD-IONPs. Finally, acute toxicity analysis was carried out in female Wistar rats according to OECD guidelines 420. Rats were exposed to the highest dose (2000mg/kg) of βCD-IONPs along with control and observed for 14days. After two weeks of administration, tissues and blood were collected and subjected to histopathological and biochemical analysis (SGOT, SGPT and ALP). Animals were sacrificed and gross necropsy was carried out. It has been shown that βCD-IONPs does not have any significant toxic effect at the cellular level. Thus, this study provides new perspectives for future biomedical applications.

Uptake and bioreactivity of charged chitosan-coated superparamagnetic nanoparticles as promising contrast agents for magnetic resonance imaging

Bioreactivity of superparamagnetic iron oxide nanoparticles (SPION) coated with thin layers of either cationic or anionic chitosan derivatives and serving as contrast agents in magnetic resonance imaging (MRI) was studied in vivo using BALB/c mouse model. Synthesized dual-modal fluorescing SPION were tracked in time using both fluorescent imaging and MRI. Although SPION started to be excreted by kidneys relatively shortly after administration they were uptaken by liver enhancing MRI contrast even up to 7 days. Importantly, chitosan-coated SPION caused only mild activation of acute phase response not affecting biochemical parameters of blood. Liver histology indicated the presence of SPION and modest increase in the number of Kupffer cells. The overall results indicated that SPION coated with ultrathin layers of chitosan ionic derivatives can serve as T₂ contrast agents for diagnosis of liver diseases or imaging of other organs assuming the dose is optimized according to the need.

Selective isolation and eradication of E. coli associated with urinary tract infections using anti-fimbrial modified magnetic reduced graphene oxide nanoheaters

The fast and efficient elimination of pathogenic bacteria from water, food or biological samples such as blood remains a challenging task. Magnetic isolation of bacteria from complex media holds particular promise for water disinfection and other biotechnological applications employing bacteria. When it comes to infectious diseases such as urinary tract infections, the selective removal of the pathogenic species in complex media such as human serum is also of importance. This issue can only be accomplished by adding pathogen specific targeting sites onto the magnetic nanostructures. In this work, we investigate the potential of 2-nitrodopamine modified magnetic particles anchored on reduced graphene oxide (rGO) nanocomposites for rapid capture and efficient elimination of E. coli associated with urinary tract infections (UTIs) from water and serum samples. An optimized magnetic nanocarrier achieves a 99.9% capture efficiency even at E. coli concentrations of 1 × 10¹ cfu mL^-1 in 30 min. In addition, functionalization of the nanostructures with poly(ethylene glycol) modified pyrene units and anti-fimbrial E. coli antibodies allowed specific elimination of E. coli UTI89 from serum samples. Irradiation of the E. coli loaded nanocomposite with a near-infrared laser results in the total ablation of the captured pathogens. This method can be flexibly modified for any other pathogenic bacteria, depending on the antibodies used, and might be an interesting alternative material for a magnetic-based body fluid purification approach.

Host-guest driven ligand replacement on monodisperse inorganic nanoparticles

We demonstrate that crown ether-assisted ligand replacement on Fe3O4 NPs using halide salts leads to quantitative stripping of an existing stabilizer shell with unprecedented (complete) efficiency; this allows subsequent re-grafting of functional ligands at maximal surface density. The mechanism of the anion-driven ligand replacement is elucidated by varying the halide salt and the versatility by varying the re-grafted ligand.

Characterizing Physical Properties of Superparamagnetic Nanoparticles in Liquid Phase Using Brownian Relaxation

Superparamagnetic iron oxide nanoparticles (SPIONs) have been extensively used as bioimaging contrast agents, heating sources for tumor therapy, and carriers for controlled drug delivery and release to target organs and tissues. These applications require elaborate tuning of the physical and magnetic properties of the SPIONs. The authors present here a search-coil-based method to characterize these properties. The nonlinear magnetic response of SPIONs to alternating current magnetic fields induces harmonic signals that contain information of these nanoparticles. By analyzing the phase lag and harmonic ratios in the SPIONs, the authors can predict the saturation magnetization, the average hydrodynamic size, the dominating relaxation processes of SPIONs, and the distinction between single- and multicore particles. The numerical simulations reveal that the harmonic ratios are inversely proportional to saturation magnetizations and core diameters of SPIONs, and that the phase lag is dependent on the hydrodynamic volumes of SPIONs, which corroborate the experimental results. Herein, the authors stress the feasibility of using search coils as a method to characterize physical and magnetic properties of SPIONs, which may be applied as building blocks in nanoparticle characterization devices.

Design and characterization of lisinopril-loaded superparamagnetic nanoparticles as a new contrast agent for in vitro, in vivo MRI imaging, diagnose the tumors and drug delivery system

Superparamagnetic γ-Fe₂O₃@SiO₂@lisinopril (MNPs-Lisinopril) nanoparticles are T2 and T2* negative contrast agents for magnetic resonance imaging. In this work, we report the preparation of lisinopril-coated MNPs for the first time as new T2 and T2* negative contrast agent for in vitro and in vivo MRI imaging and demonstrate the potential it simultaneously for drug delivery system, diagnose the tumors and MRI contrast agent. Measurements on the relaxivities (r₁, r₂ and r₂*) of the MNPs-Lisinopril were determined in deionized water (in vitro). Furthermore, after subcutaneous injection of the MNPs-Lisinopril into 4T1 (ATCC^® CRL2539™) tumor in BALB/c mice, the relaxivities were determined by a 1.5 T MRI apparatus (in vivo). T2- and T2*-weighted MRI images of MNPs-Lisinopril showed that the MR signal intensity decreased significantly with increasing nanoparticle concentration in water. With measured r₂ values up to 236.66 mM^-1s ^-1, our MNPs-Lisinopril show better performance than commercial alternatives. Also we tested drug release of Lisinopril coated MNPs at two different pHs. The MNPs- Lisinopril is a pH-sensitive drug delivery system and releases different amounts of lisinopril from MNPs-Captopril in different pHs.

Nanomaterials engineering for drug delivery: a hybridization approach

The last twenty years have witnessed great advances in biology, medicine, and materials science, leading to the development of various nanoparticle (NP)-mediated drug delivery systems. Innovation in materials science has led the generation of biodegradable, biocompatible, stimuli-responsive, and targeted delivery systems. However, currently available nanotherapeutic technologies are not efficient, which has culminated in the failure of their clinical trials. Despite huge efforts devoted to drug delivery nanotherapeutics, only a small amount of the injected material could reach the desired target. One promising strategy to enhance the efficiency of NP drug delivery is to hybridize multiple materials, where each component could play a critical role in an efficient multipurpose delivery system. This review aims to comprehensively cover different techniques, materials, advantages, and drawbacks of various systems to develop hybrid nano-vesicles for drug delivery. Attention is finally given to the hybridization benefits in overcoming the biological barriers for drug delivery. It is believed that the advent of modern nano-formulations for multifunctional hybrid carriers paves the way for future advances to achieve more efficient drug delivery systems.

Metal-Free Photoinduced Electron Transfer-Atom Transfer Radical Polymerization Integrated with Bioinspired Polydopamine Chemistry as a Green Strategy for Surface Engineering of Magnetic Nanoparticles

Developing green and efficient technologies for surface modification of magnetic nanoparticles (MNPs) is of crucial importance for their biomedical and environmental applications. This study reports, for the first time, a novel strategy by integrating metal-free photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP) with the bioinspired polydopamine (PDA) chemistry for controlled architecture of functional polymer brushes from MNPs. Conformal PDA encapsulation layers were initially generated on the surfaces of MNPs, which served as the protective shells while providing an ideal platform for tethering 2-bromo-2-phenylacetic acid (BPA), a highly efficient initiator. Metal-free PET-ATRP technique was then employed for controlled architecture of poly(glycidyl methacrylate) (PGMA) brushes from the core-shell MNPs by using diverse organic dyes as photoredox catalysts. Impacts of light sources (including UV and visible lights), photoredox catalysts, and polymerization time on the composition and morphology of the PGMA brushes were investigated. Moreover, the versatility of the PGMA-functionalized core-shell MNPs was demonstrated by covalent attachment of ethylenediamine (EDA), a model functional molecule, which afforded the MNPs with improved hydrophilicity, dispersibility, and superior binding ability to uranyl ions. The green methodology by integrating metal-free PET-ATRP with facile PDA chemistry would provide better opportunities for surface modification of MNPs and miscellaneous nanomaterials for biomedical and electronic applications.

Construction of an Acetylcholinesterase Sensor Based on Synthesized Paramagnetic Nanoparticles, a Simple Tool for Neurotoxic Compounds Assay

Magnetic particles (MPs) have been widely used in biological applications in recent years as a carrier for various molecules. Their big advantage is in repeated use of immobilized molecules including enzymes. Acetylcholinesterase (AChE) is an enzyme playing crucial role in neurotransmission and the enzyme is targeted by various molecules like Alzheimer's drugs, pesticides and warfare agents. In this work, an electrochemical biosensor having AChE immobilized onto MPs and stabilized through glutaraldehyde (GA) molecule was proposed for assay of the neurotoxic compounds. The prepared nanoparticles were modified by pure AChE and they were used for the measurement anti-Alzheimer's drug galantamine and carbamate pesticide carbofuran with limit of detection 1.5 µM and 20 nM, respectively. All measurements were carried out using screen-printed sensor with carbon working, silver reference, and carbon auxiliary electrode. Standard Ellman's assay was used for validation measurement of both inhibitors. Part of this work was the elimination of reversible inhibitors represented by galantamine from the active site of AChE. For this purpose, we used a lower pH to get the original activity of AChE after inhibition by galantamine. We also observed decarbamylation of the AChE-carbofuran adduct. Influence of organic solvents to AChE as well as repeatability of measurement with MPs with AChE was also established.

Structural and Thermodynamic Properties of Nanoparticle-Protein Complexes: A Combined SAXS and SANS Study

We propose a novel method for determining the structural and thermodynamic properties of nanoparticle-protein complexes under physiological conditions. The method consists of collecting a full set of small-angle X-ray and neutron-scattering measurements in solutions with different concentrations of nanoparticles and protein. The nanoparticle-protein dissociation process is described in the framework of the Hill cooperative model, based on which the whole set of X-ray and neutron-scattering data is fitted simultaneously. This method is applied to water solutions of gold nanoparticles in the presence of human serum albumin without any previous manipulation and can be, in principle, extended to all systems. We demonstrate that the protein dissociation constant, the Hill coefficient, and the stoichiometry of the nanoparticle-protein complex are obtained with a high degree of confidence.

Controlled aggregation and cell uptake of thermoresponsive polyoxazoline-grafted superparamagnetic iron oxide nanoparticles

Hydrophilic polymer-coated iron oxide nanoparticles are potential materials for a plethora of applications in the biotechnological field. Typical such polymers, e.g. dextran or poly(ethylene glycol), lack the ability to tailor the biological response to an environmental trigger, while common responsive polymers such as poly(N-isopropylacrylamide) or poly(acrylic acid) are not suitable for biomedical applications. We present the synthesis and characterization of superparamagnetic iron oxide nanoparticles with thermoresponsive polyoxazoline brushes grafted at unprecedented density using nitrodopamine anchor chemistry. Reversible aggregation/deaggregation is observed in water and biological medium, confirming control over the colloidal stability. Thermal switching of the solubility could only be achieved by global heating of the sample, while local magnetothermal heating did not produce a sufficiently strong temperature gradient through the brush. Varying the polymer composition allows for tuning of the lower critical solution temperature (LCST) as well as the average nanoparticle cluster size obtained upon heating. The LCST of polyoxazolines and the thermal colloidal stability are shown to be greatly affected by ion concentration, by polymer grafting density and also by the presence of serum protein; this shows that transition temperatures of free polymers in water can be very misleading for the design of polymer-coated nanomaterials for biomedical applications. Finally, the thermoresponsive SPION are shown to be non-cytotoxic and with a low cell uptake scaling with the hydration of the polymer brush, which is tuned by the polymer composition. Thus, we demonstrate that pozylated nanoparticles provide the advantages of PEG- and PNIPAM-grafted nanoparticles, but provide a tunable and more easily functionalizable platform for further development.

Individually Stabilized, Superparamagnetic Nanoparticles with Controlled Shell and Size Leading to Exceptional Stealth Properties and High Relaxivities

Superparamagnetic iron oxide nanoparticles (SPION) have received immense interest for biomedical applications, with the first clinical application as negative contrast agent in magnetic resonance imaging (MRI). However, the first generation MRI contrast agents with dextran-enwrapped, polydisperse iron oxide nanoparticle clusters are limited to imaging of the liver and spleen; this is related to their poor colloidal stability in biological media and inability to evade clearance by the reticuloendothelial system. We investigate the qualitatively different performance of a new generation of individually PEG-grafted core-shell SPION in terms of relaxivity and cell uptake and compare them to benchmark iron oxide contrast agents. These PEG-grafted SPION uniquely enable relaxivity measurements in aqueous suspension without aggregation even at 9.4 T magnetic fields due to their extraordinary colloidal stability. This allows for determination of the size-dependent scaling of relaxivity, which is shown to follow a d2 dependence for identical core-shell structures. The here introduced core-shell SPION with ∼15 nm core diameter yield a higher R2 relaxivity than previous clinically used contrast agents as well as previous generations of individually stabilized SPION. The colloidal stability extends to control over evasion of macrophage clearance and stimulated uptake by SPION functionalized with protein ligands, which is a key requirement for targeted MRI.

Radiolabeled inorganic nanoparticles for positron emission tomography imaging of cancer: an overview

Over the last few years, a plethora of radiolabeled inorganic nanoparticles have been developed and evaluated for their potential use as probes in positron emission tomography (PET) imaging of a wide variety of cancers. Inorganic nanoparticles represent an emerging paradigm in molecular imaging probe design, allowing the incorporation of various imaging modalities, targeting ligands, and therapeutic payloads into a single vector. A major challenge in this endeavor is to develop disease-specific nanoparticles with facile and robust radiolabeling strategies. Also, the radiolabeled nanoparticles should demonstrate adequate in vitro and in vivo stability, enhanced sensitivity for detection of disease at an early stage, optimized in vivo pharmacokinetics for reduced non-specific organ uptake, and improved targeting for achieving high efficacy. Owing to these challenges and other technological and regulatory issues, only a single radiolabeled nanoparticle formulation, namely "C-dots" (Cornell dots), has found its way into clinical trials thus far. This review describes the available options for radiolabeling of nanoparticles and summarizes the recent developments in PET imaging of cancer in preclinical and clinical settings using radiolabeled nanoparticles as probes. The key considerations toward clinical translation of these novel PET imaging probes are discussed, which will be beneficial for advancement of the field.

Superparamagnetic iron oxide nanoparticles functionalized by peptide nucleic acids

Hydrophilic SPION were decorated with PNA decamers by SH/maleimide clickreaction as potential MRI and hyperthermia agents, and PNA carriers.

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.

Provenance information as a tool for addressing engineered nanoparticle reproducibility challenges

Nanoparticles of various types are of increasing research and technological importance in biological and other applications. Difficulties in the production and delivery of nanoparticles with consistent and well defined properties appear in many forms and have a variety of causes. Among several issues are those associated with incomplete information about the history of particles involved in research studies, including the synthesis method, sample history after synthesis, including time and nature of storage, and the detailed nature of any sample processing or modification. In addition, the tendency of particles to change with time or environmental condition suggests that the time between analysis and application is important and some type of consistency or verification process can be important. The essential history of a set of particles can be identified as provenance information and tells the origin or source of a batch of nano-objects along with information related to handling and any changes that may have taken place since it was originated. A record of sample provenance information for a set of particles can play a useful role in identifying some of the sources and decreasing the extent of particle variability and the lack of reproducibility observed by many researchers.

Surface Modified Multifunctional and Stimuli Responsive Nanoparticles for Drug Targeting: Current Status and Uses

Nanocarriers, due to their unique features, are of increased interest among researchers working with pharmaceutical formulations. Polymeric nanoparticles and nanocapsules, involving non-toxic biodegradable polymers, liposomes, solid lipid nanoparticles, and inorganic-organic nanomaterials, are among the most used carriers for drugs for a broad spectrum of targeted diseases. In fact, oral, injectable, transdermal-dermal and ocular formulations mainly consist of the aforementioned nanomaterials demonstrating promising characteristics such as long circulation, specific targeting, high drug loading capacity, enhanced intracellular penetration, and so on. Over the last decade, huge advances in the development of novel, safer and less toxic nanocarriers with amended properties have been made. In addition, multifunctional nanocarriers combining chemical substances, vitamins and peptides via coupling chemistry, inorganic particles coated by biocompatible materials seem to play a key role considering that functionalization can enhance characteristics such as biocompatibility, targetability, environmental friendliness, and intracellular penetration while also have limited side effects. This review aims to summarize the "state of the art" of drug delivery carriers in nanosize, paying attention to their surface functionalization with ligands and other small or polymeric compounds so as to upgrade active and passive targeting, different release patterns as well as cell targeting and stimuli responsibility. Lastly, future aspects and potential uses of nanoparticulated drug systems are outlined.

Chondroitin sulfate-capped super-paramagnetic iron oxide nanoparticles as potential carriers of doxorubicin hydrochloride

Chondroitin-4-sulfate (CS), a glycosaminoglycan, was used to prepare CS-capped super-paramagnetic iron oxide nanoparticles, which were further employed for loading a water-soluble chemotherapeutic agent (doxorubicin hydrochloride, DOX). CS-capped SPIONs have potential biomedical application in cancer targeting. The optimized formulation had a hydrodynamic size of 91.2±0.8nm (PDI; 0.228±0.004) and zeta potential of -49.1±1.66mV. DOX was loaded onto the formulation up to 2% (w/w) by physical interaction with CS. TEM showed nano-sized particles having a core-shell structure. XRD confirmed crystal phase of iron oxide. FT-IR conceived the interaction of iron oxide with CS as bidentate chelation and also confirmed DOX loading. Vibration sample magnetometry confirmed super-paramagnetic nature of nanoparticles, with saturation magnetization of 0.238emug(-1). In vitro release profile at pH 7.4 showed that 96.67% of DOX was released within 24h (first order kinetics). MTT assay in MCF7 cells showed significantly higher (p<0.0001) cytotoxicity for DOX in SPIONs than DOX solution (IC50 values 6.294±0.4169 and 11.316±0.1102μgmL(-1), respectively).

Emerging translational research on magnetic nanoparticles for regenerative medicine

Regenerative medicine, which replaces or regenerates human cells, tissues or organs, to restore or establish normal function, is one of the fastest-evolving interdisciplinary fields in healthcare. Over 200 regenerative medicine products, including cell-based therapies, tissue-engineered biomaterials, scaffolds and implantable devices, have been used in clinical development for diseases such as diabetes and inflammatory and immune diseases. To facilitate the translation of regenerative medicine from research to clinic, nanotechnology, especially magnetic nanoparticles have attracted extensive attention due to their unique optical, electrical, and magnetic properties and specific dimensions. In this review paper, we intend to summarize current advances, challenges, and future opportunities of magnetic nanoparticles for regenerative medicine.

Evaluation of High-Yield Purification Methods on Monodisperse PEG-Grafted Iron Oxide Nanoparticles

Fundamental research on nanoparticle (NP) interactions and development of next-generation biomedical NP applications relies on synthesis of monodisperse, functional, core-shell nanoparticles free of residual dispersants with truly homogeneous and controlled physical properties. Still, synthesis and purification of e.g. such superparamagnetic iron oxide NPs remain a challenge. Comparing the success of different methods is marred by the sensitivity of analysis methods to the purity of the product. We synthesize monodisperse, oleic acid (OA)-capped, Fe3O4 NPs in the superparamagnetic size range (3-10 nm). Ligand exchange of OA for poly(ethylene glycol) (PEG) was performed with the PEG irreversibly grafted to the NP surface by a nitrodopamine (NDA) anchor. Four different methods were investigated to remove excess ligands and residual OA: membrane centrifugation, dialysis, size exclusion chromatography, and precipitation combined with magnetic decantation. Infrared spectroscopy and thermogravimetric analysis were used to determine the purity of samples after each purification step. Importantly, only magnetic decantation yielded pure NPs at high yields with sufficient grafting density for biomedical applications (∼1 NDA-PEG(5 kDa)/nm(2), irrespective of size). The purified NPs withstand challenging tests such as temperature cycling in serum and long-term storage in biological buffers. Dynamic light scattering, transmission electron microscopy, and small-angle X-ray scattering show stability over at least 4 months also in serum. The successful synthesis and purification route is compatible with any conceivable functionalization for biomedical or biomaterial applications of PEGylated Fe3O4 NPs.

Super-paramagnetic loaded nanoparticles based on biological macromolecules for in vivo targeted MR imaging

Target-specific MRI contrast agent based on super-paramagnetic iron oxide-chitosan-folic acid (SPIONP-CS-FA) nanoparticles was fabricated by using an ionotropic gelation method, which involved the loading of SPIONPs at various concentrations into CS-FA nanoparticles by electrostatic interaction. The SPIONP-CS-FA nanoparticles were characterized by ATR-FTIR, XRD, TEM, and VSM techniques. This study revealed that the advantages of this system would be green fabrication, low cytotoxicity at iron concentrations ranging from 0.52 mg/L to 4.16 mg/L, and high water stability (pH 6) at 4°C over long periods. Average particle size and positive zeta-potential of the SPIONP-CS-FA nanoparticles was found to be 130 nm with narrow size distribution and 42 mV, respectively. In comparison to SPIONP-0.5-CS nanoparticles, SPIONP-0.5-CS-FA nanoparticles showed higher and specific cellular uptake levels into human cervical adenocarcinoma cells due to the presence of folate receptors, while in vivo results (Wistar rat) indicated that only liver tissue showed significant decreases in MR image intensity on T2 weighted images and T2* weighted images after post-injection, in comparison with other organs. Our results demonstrated that SPIONP-CS-FA nanoparticles can be applied as an either tumor or organ specific MRI contrast agents.

Predictable Heating and Positive MRI Contrast from a Mesoporous Silica-Coated Iron Oxide Nanoparticle

Iron oxide nanoparticles have great potential as diagnostic and therapeutic agents in cancer and other diseases; however, biological aggregation severely limits their function in vivo. Aggregates can cause poor biodistribution, reduced heating capability, and can confound their visualization and quantification by magnetic resonance imaging (MRI). Herein, we demonstrate that the incorporation of a functionalized mesoporous silica shell can prevent aggregation and enable the practical use of high-heating, high-contrast iron oxide nanoparticles in vitro and in vivo. Unmodified and mesoporous silica-coated iron oxide nanoparticles were characterized in biologically relevant environments including phosphate buffered saline, simulated body fluid, whole mouse blood, lymph node carcinoma of prostate (LNCaP) cells, and after direct injection into LNCaP prostate cancer tumors in nude mice. Once coated, iron oxide nanoparticles maintained colloidal stability along with high heating and relaxivity behaviors (SARFe = 204 W/g Fe at 190 kHz and 20 kA/m and r1 = 6.9 mM(-1) s(-1) at 1.4 T). Colloidal stability and minimal nonspecific cell uptake allowed for effective heating in salt and agarose suspensions and strong signal enhancement in MR imaging in vivo. These results show that (1) aggregation can lower the heating and imaging performance of magnetic nanoparticles and (2) a coating of functionalized mesoporous silica can mitigate this issue, potentially improving clinical planning and practical use.

A simple route to diverse noble metal-decorated iron oxide nanoparticles for catalysis

Developing facile synthetic routes to multifunctional nanoparticles combining the magnetic properties of iron oxides with the optical and catalytic utility of noble metal particles remains an important goal in realizing the potential of hybrid nanomaterials. To this end, we have developed a single route to noble metal-decorated magnetic nanoparticles (Fe3O4@SiO2-M; M = Au, Pd, Ag, and PtAg) and characterized them by HRTEM and STEM/EDX imaging to reveal their nanometer size (16 nm Fe3O4 and 1-5 nm M seeds) and uniformity. This represents one of the few examples of genuine multifunctional particles on the nanoscale. We show that these hybrid structures have excellent catalytic activity for the reduction of 4-nitrophenol (knorm = 2 × 10(7) s(-1) mol(Pd)(-1); 5 × 10(6) s(-1) mol(Au)(-1); 5 × 10(5) s(-1) mol(PtAg)(-1); 7 × 10(5) s(-1) mol(Ag)(-1)). These rates are the highest reported for nano-sized comparables, and are competitive with mesoparticles of similar composition. Due to their magnetic response, the particles are also suitable for magnetic recovery and maintain >99% conversion for at least four cycles. Using this synthetic route, Fe3O4@SiO2-M particles show great promise for further development as a precursor to complicated anisotropic materials or for applications ranging from nanocatalysis to biomedical sensing.

Triggered Release from Thermoresponsive Polymersomes with Superparamagnetic Membranes

Magnetic polymersomes were prepared by self-assembly of the amphiphilic block copolymer poly(isoprene-b-N-isopropylacrylamide) with monodisperse hydrophobic superparamagnetic iron oxide nanoparticles (SPION). The specifically designed thermoresponsive block copolymer allowed for efficient incorporation of the hydrophobic nanoparticles in the membrane core and encapsulation of the water soluble dye calcein in the lumen of the vesicles. Magnetic heating of the embedded SPIONs led to increased bilayer permeability through dehydration of the thermoresponsive PNIPAM block. The entrapped calcein could therefore be released in controlled doses solely through exposure to pulses of an alternating magnetic field. This hybrid SPION-polymersome system demonstrates a possible direction for release applications that merges rational polymersome design with addressed external magnetic field-triggered release through embedded nanomaterials.

A tandem polyol process and ATRP used to design new processable hybrid exchange-biased CoxFe3−xO4@CoO@PMMA nanoparticles

The relationships between interparticle distance and magnetic properties of CoxFe_3−xO₄@CoO@PMMA nanoparticles clearly emphasize the role of material processing for the design of tailored flexible polymer based hybrid materials.

Cytotoxicity and imaging studies of β-NaGdF4:Yb3+Er3+@PEG-Mo nanorods

Multimodal imaging based on nanostructures has become a subject of interest for numerous biomedical laboratories.

Facile synthesis of superparamagnetic magnetite nanoflowers and their applications in cellular imaging

Thermal decomposition of an iron-oleate complex in the presence of a surfactant gives water-soluble biocompatible superparamagnetic magnetite nanoflowers via a one-pot reaction.

Synthesis and in vitro properties of iron oxide nanoparticles grafted with brushed phosphorylcholine and polyethylene glycol

A new and facile strategy for grafting IONPs by phosphonic acic terminated PC brushes has been demonstrated and characterized in vitro.

Effect of Ce doping into ZnO nanostructures to enhance the phenolic sensor performance

Various Ce-doped ZnO nanostructures (Ce/ZnO NSs) were prepared by a facile wet chemical method using reducing agents in alkaline medium.

Magnetic nanoparticles and nanocomposites for remote controlled therapies

This review highlights the state-of-the-art in the application of magnetic nanoparticles (MNPs) and their composites for remote controlled therapies. Novel macro- to nano-scale systems that utilize remote controlled drug release due to actuation of MNPs by static or alternating magnetic fields and magnetic field guidance of MNPs for drug delivery applications are summarized. Recent advances in controlled energy release for thermal therapy and nanoscale energy therapy are addressed as well. Additionally, studies that utilize MNP-based thermal therapy in combination with other treatments such as chemotherapy or radiation to enhance the efficacy of the conventional treatment are discussed.

The interaction of sterically stabilized magnetic nanoparticles with fresh human red blood cells

Sterically stabilized superparamagnetic iron oxide nanoparticles (SPIONs) were incubated with fresh human erythrocytes (red blood cells [RBCs]) to explore their potential application as magnetic resonance imaging contrast agents. The chemical shift and linewidth of (133)Cs(+) resonances from inside and outside the RBCs in (133)Cs nuclear magnetic resonance spectra were monitored as a function of time. Thus, we investigated whether SPIONs of two different core sizes and with three different types of polymeric stabilizers entered metabolically active RBCs, consuming glucose at 37°C. The SPIONs broadened the extracellular (133)Cs(+) nuclear magnetic resonance, and brought about a small change in its chemical shift to a higher frequency; while the intracellular resonance remained unchanged in both amplitude and chemical shift. This situation pertained over incubation times of up to 90 minutes. If the SPIONs had entered the RBCs, the intracellular resonance would have become broader and possibly even shifted. Therefore, we concluded that our SPIONs did not enter the RBCs. In addition, the T 2 relaxivity of the small and large particles was 368 and 953 mM(-1) s(-1), respectively (three and nine times that of the most effective commercially available samples). This suggests that these new SPIONs will provide a superior performance to any others reported thus far as magnetic resonance imaging contrast agents.

Nanomedical innovation: the SEON-concept for an improved cancer therapy with magnetic nanoparticles

Nanomedicine offers tremendous opportunities for the development of novel therapeutic and diagnostic tools. During the last decades, extensive knowledge was gained about stabilizing and the coating of nanoparticles, their functionalization for drug binding and drug release and possible strategies for therapies and diagnostics of different diseases. Most recently, more and more emphasis has been placed on nanotoxicology and nanosafety aspects. The section of experimental oncology and nanomedicine developed a concept for translating this knowledge into clinical application of magnetic drug targeting for the treatment of cancer and other diseases using superparamagnetic iron oxide nanoparticles. This approach includes reproducible synthesis, detailed characterization, nanotoxicological testing, evaluation in ex vivo models, preclinical animal studies and production of superparamagnetic iron oxide nanoparticles according to good manufacturing practice regulations.

Aqueous synthesis of polyhedral "brick-like" iron oxide nanoparticles for hyperthermia and T2 MRI contrast enhancement

A low temperature, aqueous synthesis of polyhedral iron oxide nanoparticles (IONPs) is presented. The modification of the co-precipitation hydrolysis method with Triton X surfactants results in the formation of crystalline polyhedral particles. The particles are herein termed iron oxide "nanobricks" (IONBs) as the variety of particles made are all variations on a simple "brick-like" rhombohedral shape as evaluated by TEM. These IONBs can be easily coated with hydrophilic silane ligands, allowing them to be dispersed in aqueous media. The dispersed particles are investigated for potential applications as hyperthermia and T2 MRI contrast agents. The results demonstrate that the IONBs perform better than comparable spherical IONPs in both applications, and show r2 values amongst the highest for iron oxide based materials reported in the literature.