Effect of Polymer and Cell Membrane Coatings on Theranostic Applications of Nanoparticles: A Review

The recent decade has witnessed a remarkable surge in the field of nanoparticles, from their synthesis, characterization, and functionalization to diverse applications. At the nanoscale, these particles exhibit distinct physicochemical properties compared to their bulk counterparts, enabling a multitude of applications spanning energy, catalysis, environmental remediation, biomedicine, and beyond. This review focuses on specific nanoparticle categories, including magnetic, gold, silver, and quantum dots (QDs), as well as hybrid variants, specifically tailored for biomedical applications. A comprehensive review and comparison of prevalent chemical, physical, and biological synthesis methods are presented. To enhance biocompatibility and colloidal stability, and facilitate surface modification and cargo/agent loading, nanoparticle surfaces are coated with different synthetic polymers and very recently, cell membrane coatings. The utilization of polymer- or cell membrane-coated nanoparticles opens a wide variety of biomedical applications such as magnetic resonance imaging (MRI), hyperthermia, photothermia, sample enrichment, bioassays, drug delivery, etc. With this review, the goal is to provide a comprehensive toolbox of insights into polymer or cell membrane-coated nanoparticles and their biomedical applications, while also addressing the challenges involved in translating such nanoparticles from laboratory benchtops to in vitro and in vivo applications. Furthermore, perspectives on future trends and developments in this rapidly evolving domain are provided.

Magnetically Active Bicontinuous Polymer Structures for Multiple Controlled Drug Delivery

The targeted delivery of drugs using wireless navigable magnetic robots allows the delivery of drug molecules to be controlled non only in time but also in space, improving medical outcomes. The main disadvantages behind their use lies in the low amount of drug that can be transported and the single nature of drug that can be loaded (hydrophilic or hydrophobic). These considerations limit their use in co-delivery systems, now recognized to be very promising for many different pathologies. A magnetic bijel-like structure is developed to load and release different types of molecules (hydrophilic and hydrophobic). In this work, the use of ε-caprolactone is explored, which can polymerize, forming hydrophobic domains (oil phase). After mixing with iron oxide nanoparticles (NPs), the water dispersion creates a magnetic biphasic porous structure without phase separation. The resulting device shows good performance both in magnetic actuation and as a drug delivery system.

Elaboration of Functionalized Iron Oxide Nanoparticles by Microwave-Assisted Co-Precipitation: A New One-Step Method in Water

Iron oxide nanoparticles are extensively utilized in various fields, particularly in biomedical applications. For such uses, nanoparticles must meet specific criteria, including precise size, morphology, physico-chemical properties, stability, and biocompatibility. Microwave-assisted co-precipitation offers an efficient method for producing water-soluble nanoparticles. Functionalization with citrate during synthesis is crucial for achieving a stable colloidal solution. This study aims to compare the effectiveness of conventional co-precipitation with microwave-assisted co-precipitation. The synthesized nanoparticles were characterized using TEM, DLS, FTIR, XRD, and magnetic measurements. The findings indicate that the in situ citrate functionalization during synthesis results in stable, non-aggregated nanoparticles.

Polypyrrole/iron-glycol chitosan nanozymes mediate M1 macrophages to enhance the X-ray-triggered photodynamic therapy for bladder cancer by promoting antitumor immunity

X-ray Photodynamic Therapy (XPDT) is an emerging, deeply penetrating, and non-invasive tumor treatment that stimulates robust antitumor immune responses. However, its efficacy is often limited by low therapeutic delivery and immunosuppressant within the tumor microenvironment. This challenge can potentially be addressed by utilizing X-ray responsive iron-glycol chitosan-polypyrrole nanozymes (GCS-I-PPy NZs), which activate M1 macrophages. These nanozymes increase tumor infiltration and enhance the macrophages' intrinsic immune response and their ability to stimulate adaptive immunity. Authors have designed biocompatible, photosensitizer-containing GCS-I-PPy NZs using oxidation/reduction reactions. These nanozymes were internalized by M1 macrophages to form RAW-GCS-I-PPy NZs. Authors' results demonstrated that these engineered macrophages effectively delivered the nanozymes with potentially high tumor accumulation. Within the tumor microenvironment, the accumulated GCS-I-PPy NZs underwent X-ray irradiation, generating reactive oxygen species (ROS). This ROS augmentation significantly enhanced the therapeutic effect of XPDT and synergistically promoted T cell infiltration into the tumor. These findings suggest that nano-engineered M1 macrophages can effectively boost the immune effects of XPDT, providing a promising strategy for enhancing cancer immunotherapy. The ability of GCS-I-PPy NZs to mediate M1 macrophage activation and increase tumor infiltration highlights their potential in overcoming the limitations of current XPDT approaches and improving therapeutic outcomes in melanoma and other cancers.

Recent advances in core-shell structured catalysts for low-temperature NH3-SCR of NOx

Ammonia selective catalytic reduction (NH₃-SCR) of nitrogen oxides is an effective and well-established technology for NO_x removal, but current commercial denitrification catalysts based on V₂O₅-WO₃/TiO₂ have some obvious disadvantages, including narrow operating temperature windows, toxicity, poor hydrothermal stability, and unsatisfied SO₂/H₂O tolerance. To overcome these drawbacks, it is imperative to investigate new types of highly efficient catalysts. In order to design catalysts with outstanding selectivity, activity, and anti-poisoning ability, core-shell structured materials have been widely applied in the NH₃-SCR reaction, which exhibits numerous advantages including the large surface area, the strong synergy interaction of core-shell materials, the confinement effect, and the shielding effect from the shell layer to protect the core. This review summarizes recent developments of core-shell structured catalysts for NH₃-SCR, including basic classification, synthesis methods, and a detailed description of the performance and mechanisms of each type of catalyst. It is hoped that the review will stimulate future developments in NH₃-SCR technology, leading to novel catalyst designs with improved denitrification performance.

Water-induced stacked α-Fe2O3 hexagonal nanoplates along [001] direction and its facet-dependent catalytic performances

Controlling the growth of nanocrystal to expose a specific facet is of great significance for the rational design of effective crystal catalysts. Herein, a water-induced stacking process was developed to...

Magnetic nanoparticles and clusters for magnetic hyperthermia: optimizing their heat performance and developing combinatorial therapies to tackle cancer

Magnetic hyperthermia (MHT) is a therapeutic modality for the treatment of solid tumors that has now accumulated more than 30 years of experience. In the ongoing MHT clinical trials for the treatment of brain and prostate tumors, iron oxide nanoparticles are employed as intra-tumoral MHT agents under a patient-safe 100 kHz alternating magnetic field (AMF) applicator. Although iron oxide nanoparticles are currently approved by FDA for imaging purposes and for the treatment of anemia, magnetic nanoparticles (MNPs) designed for the efficient treatment of MHT must respond to specific physical-chemical properties in terms of magneto-energy conversion, heat dose production, surface chemistry and aggregation state. Accordingly, in the past few decades, these requirements have boosted the development of a new generation of MNPs specifically aimed for MHT. In this review, we present an overview on MNPs and their assemblies produced via different synthetic routes, focusing on which MNP features have allowed unprecedented heating efficiency levels to be achieved in MHT and highlighting nanoplatforms that prevent magnetic heat loss in the intracellular environment. Moreover, we review the advances on MNP-based nanoplatforms that embrace the concept of multimodal therapy, which aims to combine MHT with chemotherapy, radiotherapy, immunotherapy, photodynamic or phototherapy. Next, for a better control of the therapeutic temperature at the tumor, we focus on the studies that have optimized MNPs to maintain gold-standard MHT performance and are also tackling MNP imaging with the aim to quantitatively assess the amount of nanoparticles accumulated at the tumor site and regulate the MHT field conditions. To conclude, future perspectives with guidance on how to advance MHT therapy will be provided.

Little Adjustments Significantly Simplify the Gram-Scale Synthesis of High-Quality Iron Oxide Nanocubes

This work presents a facile one-step protocol for the gram-scale synthesis of iron oxide nanocubes with adjustable sizes ranging from 13 to 20 nm and with size distributions between 7 and 12%. As X-ray diffraction indicated the initial formation of the wüstite phase, a formation mechanism of the nanocubes based on the wüstite crystal structure is proposed. When exposed to ambient conditions, the nanoparticles rapidly oxidize to magnetite/maghemite with a remaining wüstite core. The cubic morphology is attributed to the thermodynamic stability of the exposed {100} facets and the control over the growth rate via the use of a sodium oleate/oleic acid mixed ligand system. In contrast to previously reported procedures, the described synthetic approach does not require the initial preparation and isolation of iron oleate. Therefore, the amount of work and the consumption of hazardous solvents are significantly reduced. Thus, the method presented is much more efficient and environmentally more friendly while maintaining excellent control over the particles' shape, size, and size distribution.

Synthesis of highly monodisperse Pd nanoparticles using a binary surfactant combination and sodium oleate as a reductant

This study presents the synthesis of monodisperse Pd nanoparticles (NPs) stabilized by sodium oleate (NaOL) and hexadecyltrimethylammonium chloride (CTAC). The synthesis was conducted without traditional reductants and Pd-precursors are reduced by NaOL. It was confirmed that the alkyl double bond in NaOL is not the only explanation for the reduction of Pd-precursors since Pd NPs could be synthesized with CTAC and the saturated fatty acid sodium stearate (NaST). A quantitative evaluation of the reduction kinetics using UV-Vis spectroscopy shows that Pd NPs synthesized with both stabilizer combinations follow pseudo first-order reaction kinetics, where NaOL provides a faster and more effective reduction of Pd-precursors. The colloidal stabilization of the NP surface by CTAC and NaOL is confirmed by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) analysis.

Understanding the Effects of Iron Precursor Ligation and Oxidation State Leads to Improved Synthetic Control for Spinel Iron Oxide Nanocrystals

Iron oxide nanocrystals have the potential for use in a wide variety of applications if we can finely control and tune the diverse structural attributes that lead to specific, desired properties. At the high temperatures utilized for thermal decomposition based syntheses, commonly used Fe(III) alkylcarboxylate precursors are inadvertently reduced and produce wüstite (FeO), which is paramagnetic, as opposed to the desired ferrimagnetic spinel phases of magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃). To circumvent this issue, we carried out syntheses at lower temperatures (∼230 °C) using an esterification-mediated approach. Under these conditions, formation of the FeO phase can be avoided. However, we found that the precursor oxidation state and ligation had a surprisingly strong influence on the morphologies of the resulting nanocrystals. To investigate the cause of these morphological effects, we carried out analogous nanocrystal syntheses with a series of precursors. The use of Fe(III) oleate precursors yielded highly crystalline, largely twin-free nanocrystals; however, small amounts of acetylacetonate ligation yielded nanocrystals with morphologies characteristic of twin defects. During synthesis at 230 °C, the Fe(III) oleate precursor is partially reduced, providing sufficient quantities of Fe(II) that are needed to grow the Fe₃O₄ nanocrystals (wherein one-third of the iron atoms are in the Fe(II) state) without twinning. Our investigations suggest that the acetylacetonate ligands prevent reduction of Fe(III) to Fe(II), leading to twinned structures during synthesis. Harnessing this insight, we identified conditions to predictably and continuously grow octahedral, spinel nanocrystals as well as conditions to synthesize highly twinned nanocrystals. These findings also help explain observations in the thermal decomposition synthesis literature which suggest that iron oxide nanocrystals produced from Fe(acac)₃ are less prone to FeO contamination in comparison to those produced from Fe(III) alkylcarboxylates.

Unravelling the nucleation, growth, and faceting of magnetite-gold nanohybrids

The chemical synthesis of nanoparticles with a preassigned size and shape is important for an optimized performance in any application. Therefore, systematic monitoring of the synthesis is required for the control and detailed understanding of the nucleation and growth of the nanoparticles. Here, we study Fe3O4-Au hybrid nanoparticles in detail using probes of the reaction mixture during synthesis and their thorough characterization. The proposed approach eliminates the problem of repeatability and reproducibility of the chemical synthesis and was carried out using laboratory equipment (standard transmission electron microscopy, X-ray diffraction, and magnetometry) for typically 10 μL samples instead of, for example, a dedicated synthesis and inspection at a synchrotron radiation facility. From the three independent experimental techniques we extract the nanoparticle size at 12 stages of the synthesis. These diameters show identical trends and good quantitative agreement. Two consecutive processes occur during the synthesis of Fe3O4-Au nanoparticles, the nucleation and the growth of spherical Fe3O4 nanoparticles on the surface of Au seeds during the heating stage and their faceting towards octahedral shape during reflux. The final nanoparticles with sizes of 15 nm Fe3O4 and 4 nm Au exhibit superparamagnetic behavior at ambient temperature. These are high-quality, close to stoichiometric Fe3O4 nanocrystals with nearly volumetric magnetic behavior as confirmed by the presence of the Verwey transition. Understanding the processes occurring during the synthesis allows the nanoparticle size and shape to be adjusted, improving their capabilities in biomedical applications.

Continuous production of iron oxide nanoparticles via fast and economical high temperature synthesis

A continuous, fast and economical high temperature synthesis of iron oxide nanoparticles was developed and compared to a conventional batch synthesis in terms of production costs.

Synthesis and high-resolution structural and chemical analysis of iron-manganese-oxide core-shell nanocubes

We have investigated the structure and chemical composition of nanoparticles synthesized by thermal decomposition of a mixture of iron oleate and manganese oleate in a high-boiling solvent in the presence of Na-oleate and oleic acid as surfactants by analytical transmission electron microscopy (TEM). The particles appear core-shell like in bright field TEM images. Higher spatial resolution TEM (HRTEM) analysis reveals a FeO/MnO like structure in the core and a spinel like structure in the shell. With high-resolution analytical methods like energy dispersive x-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), the distribution of the metals Mn and Fe was investigated. Differences in the oxidation state of these metals were found between the core and the shell region. The presence of sodium from the used surfactant (Na-oleate) on the surface of the particles has been proved.

Magnetic Separation in Bioprocessing Beyond the Analytical Scale: From Biotechnology to the Food Industry

Downstream processing needs more innovative ideas to advance and overcome current bioprocessing challenges. Chromatography is by far the most prevalent technique used by a conservative industrial sector. Chromatography has many advantages but also often represents the most expensive step in a pharmaceutical production process. Therefore, alternative methods as well as further processing strategies are urgently needed. One promising candidate for new developments on a large scale is magnetic separation, which enables the fast and direct capture of target molecules in fermentation broths. There has been a small revolution in this area in the last 10–20 years and a few papers dealing with the use of magnetic separation in bioprocessing examples beyond the analytical scale have been published. Since each target material is purified with a different magnetic separation approach, the comparison of processes is not trivial but would help to understand and improve magnetic separation and thus making it attractive for the technical scale. To address this issue, we report on the latest achievements in magnetic separation technology and offer an overview of the progress of the capture and separation of biomolecules derived from biotechnology and food technology. Magnetic separation has great potential for high-throughput downstream processing in applied life sciences. At the same time, two major challenges need to be overcome: (1) the development of a platform for suitable and flexible separation devices and (2) additional investigations of advantageous processing conditions, especially during recovery. Concentration and purification factors need to be improved to pave the way for the broader use of magnetic applications. The innovative combination of magnetic gradients and multipurpose separations will set new magnetic-based trends for large scale downstream processing.

Valuable structure-size relationships for tadpole-shaped single-chain nanoparticles with long and short flexible tails unveiled

Tadpole-shaped single-chain nanoparticles (TSCNPs) are useful soft building blocks for nanotechnology composed of a flexible polymer chain tethered to an intramolecularly folded single-chain nanoparticle.

Design strategies for shape-controlled magnetic iron oxide nanoparticles

Ferrimagnetic iron oxide nanoparticles (magnetite or maghemite) have been the subject of an intense research, not only for fundamental research but also for their potentiality in a widespread number of practical applications. Most of these studies were focused on nanoparticles with spherical morphology but recently there is an emerging interest on anisometric nanoparticles. This review is focused on the synthesis routes for the production of uniform anisometric magnetite/maghemite nanoparticles with different morphologies like cubes, rods, disks, flowers and many others, such as hollow spheres, worms, stars or tetrapods. We critically analyzed those procedures, detected the key parameters governing the production of these nanoparticles with particular emphasis in the role of the ligands in the final nanoparticle morphology. The main structural and magnetic features as well as the nanotoxicity as a function of the nanoparticle morphology are also described. Finally, the impact of each morphology on the different biomedical applications (hyperthermia, magnetic resonance imaging and drug delivery) are analysed in detail. We would like to dedicate this work to Professor Carlos J. Serna, Instituto de Ciencia de Materiales de Madrid, ICMM/CSIC, for his outstanding contribution in the field of monodispersed colloids and iron oxide nanoparticles. We would like to express our gratitude for all these years of support and inspiration on the occasion of his retirement.

Unravelling the Thermal Decomposition Parameters for The Synthesis of Anisotropic Iron Oxide Nanoparticles

Iron oxide nanoparticles are widely used as a contrast agent in magnetic resonance imaging (MRI), and may be used as therapeutic agent for magnetic hyperthermia if they display in particular high magnetic anisotropy. Considering the effect of nanoparticles shape on anisotropy, a reproducible shape control of nanoparticles is a current synthesis challenge. By investigating reaction parameters, such as the iron precursor structure, its water content, but also the amount of the surfactant (sodium oleate) reported to control the shape, iron oxide nanoparticles with different shape and composition were obtained, in particular, iron oxide nanoplates. The effect of the surfactant coming from precursor was taking into account by using in house iron stearates bearing either two or three stearate chains and the negative effect of water on shape was confirmed by considering these precursors after their dehydration. Iron stearates with three chains in presence of a ratio sodium oleate/oleic acid 1:1 led mainly to nanocubes presenting a core-shell Fe1-xO@Fe3-xO₄ composition. Nanocubes with straight faces were only obtained with dehydrated precursors. Meanwhile, iron stearates with two chains led preferentially to the formation of nanoplates with a ratio sodium oleate/oleic acid 4:1. The rarely reported flat shape of the plates was confirmed with 3D transmission electronic microscopy (TEM) tomography. The investigation of the synthesis mechanisms confirmed the major role of chelating ligand and of the heating rate to drive the cubic shape of nanoparticles and showed that the nanoplate formation would depend mainly on the nucleation step and possibly on the presence of a given ratio of oleic acid and chelating ligand (oleate and/or stearate).

Shape-controlled syntheses of metal oxide nanoparticles by the introduction of rare-earth metals

Here, we report the size- and shape-controlled synthesis of metal oxide nanoparticles through the introduction of rare-earth metals. The addition of gadolinium oleate in the synthesis of iron oxide nanoparticles induced sphere-to-cube shape changes of nanoparticles and generated iron oxide nanocubes coated with gadolinium. Based on experimental investigations and density functional theory (DFT) calculations, we attribute the shape change to the facet-selective binding of undecomposed gadolinium oleates. While many previous studies on the shape-controlled syntheses of nanoparticles rely on the stabilization of specific crystal facets by anionic surfactants or their decomposition products, this study shows that the interaction between growing transition metal oxide nanoparticles and rare-earth metal complexes can be used as a robust new mechanism for shape-controlled syntheses. Indeed, we demonstrated that this approach was applicable to other transition metal oxide nanoparticles (i.e., manganese oxide and manganese ferrite) and rare earth metals (i.e., gadolinium, europium, and cerium). This study also demonstrates that the nature of metal-ligand bonding can play an important role in the shape control of nanoparticles.

Shape and size controlled synthesis of uniform iron oxide nanocrystals through new non-hydrolytic routes

New, non-hydrolytic routes to synthesize highly crystalline iron oxide nanocrystals (8-40 nm, magnetite) are described in this report whereby particle size and morphology were precisely controlled through reactant (precursor, e.g. (FeO(OH)) ratios, co-surfactant and organic additive, and/or reaction time. Particle size, with high monodispersivity (<10%), is demonstrated to be a function of precursor concentrations and through the addition of different cosurfactants and/or additives, cubic, octahedral, potato-like, and flower-like iron oxide nanocrystals can be reproducibly synthesized through simple one-pot thermal decomposition methods. High resolution transmission electron microscope, x-ray diffraction, and superconducting quantum interference device were used to characterize the size, structure and magnetic properties of the resulting nanocrystals. For aqueous applications, materials synthesized/purified in organic solvents are broadly water dispersible through a variety of phase (aqueous) transfer method(s).

High-Performance Ferrite Nanoparticles through Nonaqueous Redox Phase Tuning

From magnetic resonance imaging to cancer hyperthermia and wireless control of cell signaling, ferrite nanoparticles produced by thermal decomposition methods are ubiquitous across biomedical applications. While well-established synthetic protocols allow for precise control over the size and shape of the magnetic nanoparticles, structural defects within seemingly single-crystalline materials contribute to variability in the reported magnetic properties. We found that stabilization of metastable wüstite in commonly used hydrocarbon solvents contributed to significant cation disorder, leading to nanoparticles with poor hyperthermic efficiencies and transverse relaxivities. By introducing aromatic ethers that undergo radical decomposition upon thermolysis, the electrochemical potential of the solvent environment was tuned to favor the ferrimagnetic phase. Structural and magnetic characterization identified hallmark features of nearly defect-free ferrite nanoparticles that could not be demonstrated through postsynthesis oxidation with nearly 500% increase in the specific loss powers and transverse relaxivity times compared to similarly sized nanoparticles containing defects. The improved crystallinity of the nanoparticles enabled rapid wireless control of intracellular calcium. Our work demonstrates that redox tuning during solvent thermolysis can generate potent theranostic agents through selective phase control in ferrites and can be extended to other transition metal oxides relevant to memory and electrochemical storage devices.

Shape-controlled iron oxide nanocrystals: synthesis, magnetic properties and energy conversion applications

Iron oxide nanocrystals (IONCs) with various geometric morphologies show excellent physical and chemical properties and have received extensive attention in recent years.

Recent progress on magnetic iron oxide nanoparticles: synthesis, surface functional strategies and biomedical applications

This review focuses on the recent development and various strategies in the preparation, microstructure, and magnetic properties of bare and surface functionalized iron oxide nanoparticles (IONPs); their corresponding biological application was also discussed. In order to implement the practical in vivo or in vitro applications, the IONPs must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of IONPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The new functionalized strategies, problems and major challenges, along with the current directions for the synthesis, surface functionalization and bioapplication of IONPs, are considered. Finally, some future trends and the prospects in these research areas are also discussed.

Precise control over shape and size of iron oxide nanocrystals suitable for assembly into ordered particle arrays

Here we demonstrate how monodisperse iron oxide nanocubes and nanospheres with average sizes between 5 and 27 nm can be synthesized by thermal decomposition. The relative importance of the purity of the reactants, the ratio of oleic acid and sodium oleate, the maximum temperature, and the rate of temperature increase, on robust and reproducible size and shape-selective iron oxide nanoparticle synthesis are identified and discussed. The synthesis conditions that generate highly monodisperse iron oxide nanocubes suitable for producing large ordered arrays, or mesocrystals are described in detail.

Selectively self-assembling graphene nanoribbons with shaped iron oxide nanoparticles

Nanoflower-shaped iron oxide nanoparticles (FeNPs) were attached onto graphene nanoribbons (GNRs).

Synthesis and Characterization of Iron Oxide Nanoparticles

Iron oxide nanoparticles show great promise in bio-applications like drug delivery, magnetic resonance imaging, and hyperthermia. This is because the size of these magnetic nanoparticles is comparable to biomolecules and the particles can be removed via normal iron metabolic pathways. These nanoparticles are also attractive for industrial separations and catalysis because they can be magnetically recovered. However, the size, morphology, and surface coating of the iron oxide nanoparticles greatly affect their magnetic properties and biocompatibility. Therefore, nanoparticles with tunable characteristics are desirable. This chapter elaborates the synthesis techniques for the formation of iron oxide nanoparticles with good control over reproducibility, surface and magnetic properties, and morphology. The well-known co-precipitation and thermal decomposition methods are detailed in this chapter. The surface modification routes and characterization of these nanoparticles are also discussed. The chapter will be particularly useful for engineering/science graduate students and/or faculty interested in synthesizing iron oxide nanoparticles for specific research applications.

Iron oxide nanoparticles with sizes, shapes and compositions resulting in different magnetization signatures as potential labels for multiparametric detection

Magnetic iron oxide nanoparticles differing in their size, shape (spherical, hexagonal, rods, cubes) and composition have been synthesized and modified using caffeic acid for transfer to aqueous media and stabilization of the particle suspensions at physiological pH. A super quantum interference device and the recently patented magnetic sensor MIAplex®, which registered a signal proportional to the second derivative of the magnetization curve, were used to study the magnetization behavior of the nanoparticles. The differences in the magnetic signatures of the nanoparticles (spheres and rods) make them promising candidates for the simultaneous detection of different types of biological molecules.

Enhancing transversal relaxation for magnetite nanoparticles in MR imaging using Gd³+- chelated mesoporous silica shells

A new magnetic nanoparticle was synthesized in the form of Gd(3+)-chelated Fe(3)O(4)@SiO(2). The Fe(3)O(4) nanoparticle was octahedron-structured, was highly magnetic (∼94 emu/g), and was the core of an encapsulating mesoporous silica shell. DOTA-NHS molecules were anchored to the interior channels of the porous silica to chelate Gd(3+) ions. Because there were Gd(3+) ions within the silica shell, the transverse relaxivity increased 7-fold from 97 s(-1) mM(-1) of Fe(3)O(4) to 681 s(-1) mM(-1) of Gd(3+)-chelated Fe(3)O(4)@SiO(2) nanoparticles with r(2)/r(1) = 486. The large transversal relaxivity of the Gd(3+)-chelated Fe(3)O(4)@SiO(2) nanoparticles had an effective magnetic resonance imaging effect and clearly imaged lymph nodes. Physiological studies of liver, spleen, kidney, and lung tissue in mice infused with these new nanoparticles showed no damage and no cytotoxicity in Kupffer cells, which indicated that Gd(3+)-chelated Fe(3)O(4)@SiO(2) nanoparticles are biocompatible.

Synthesis and growth mechanism of iron oxide nanowhiskers

Iron oxide nanowhiskers with dimensions of approximately 2 × 20 nm were successfully synthesized by selectively heating an iron oleate complex. Such nanostructures resulted from the difference in the ligand coordination microenvironments of the Fe(III) oleate complex, according to our electronic structure calculations and thermogravimetric analysis. A ligand-directed growth mechanism was subsequently proposed to rationalize the growth process. The formation of the nanowhiskers provides a unique example of shape-controlled nanostructures, offering additional insights into nanoparticle synthesis.

Synthesis, self-assembly, and characterization of PEG-coated iron oxide nanoparticles as potential MRI contrast agent

AIM

Investigated the self-assembly and characterization of novel antifouling polyethylene glycol (PEG)-coated iron oxide nanoparticles as nanoprobes for magnetic resonance imaging (MRI) contrast agent.

METHOD

Monodisperse oleic acid-coated superparamagnetic iron oxide cores are synthesized by thermal decomposition of iron oleate. The self-assembly behavior between iron oxide cores and PEG-lipid conjugates in water and their characteristics are confirmed by transmission electron microscope, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, and vibrating sample magnetometer.

RESULT

Dynamic light scattering shows superparamagnetic iron oxide nanoparticles coated with PEG are stable in water for pH of 3-10 and ionic strengths up to 0.3 M NaCl, and are protein resistant in physiological conditions. Additionally, in vitro MRI study demonstrates the efficient magnetic resonance imaging contrast characteristics of the iron oxide nanoparticles.

CONCLUSION

The result indicates that the novel antifouling PEG-coated superparamagnetic iron oxide nanoparticles could potentially be used in a wide range of applications such as biotechnology, MRI, and magnetic fluid hyperthermia.