Preparation and characterization of magnetic nanofibers with iron oxide nanoparticles and poly(ethylene terephthalate)

Iron oxide nanoparticle/Poly(ethylene terephthalate) (PET) nanowebs were obtained by electrospinning. To achieve superparamagnetic properties, iron oxide nanoparticles with diameters below 25 nm were used. Diameter distribution of iron oxide nanoparticles was measured by a particle size analyzer. Iron oxide nanoparticles were added into 16 wt % PET solution in the ratio of 5, 10, and 15 wt % to PET. The morphology of iron oxide nanoparticle/PET nanowebs was observed using field emission-scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The nanofiber diameter increased as increasing iron oxide nanoparticle concentration. The superparamagnetic behavior of iron oxide nanoparticle/PET nanofiber was confirmed using superconducting quantum interference device (SQUID). The degree of crystallinity of iron oxide nanoparticle/PET nanowebs was calculated from a differential scanning calorimeter (DSC) results. The change of flexural rigidity and tensile properties of electrospun iron oxide nanoparticle/PET nanowebs with the external magnetic field were examined ISO 9073-7 testing method, universal testing machine and an appropriate magnet. Also, the elastic modulus of iron oxide nanoparticle/PET nanofiber was measured using nanoindentation. With applying magnetic field, the improvement in mechanical properties of field-responsive magnetic nanofibers and nanowebs was confirmed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Starch-Coated Magnetic Iron Oxide Nanoparticles for Affinity Purification of Recombinant Proteins

Starch-coated magnetic iron oxide nanoparticles have been synthesized by a simple, fast, and cost-effective co-precipitation method with cornstarch as a stabilizing agent. The structural and magnetic characteristics of the synthesized material have been studied by transmission electron microscopy, Mössbauer spectroscopy, and vibrating sample magnetometry. The nature of bonds between ferrihydrite nanoparticles and a starch shell has been examined by Fourier transform infrared spectroscopy. The data on the magnetic response of the prepared composite particles have been obtained by magnetic measurements. The determined magnetic characteristics make the synthesized material a good candidate for use in magnetic separation. Starch-coated magnetic iron oxide nanoparticles have been tested as an affinity sorbent for one-step purification of several recombinant proteins (cardiac troponin I, survivin, and melanoma inhibitory activity protein) bearing the maltose-binding protein as an auxiliary fragment. It has been shown that, due to the highly specific binding of this fragment to the starch shell, the target fusion protein is selectively immobilized on magnetic nanoparticles and eluted with the maltose solution. The excellent efficiency of column-free purification, high binding capacity of the sorbent (100–500 µg of a recombinant protein per milligram of starch-coated magnetic iron oxide nanoparticles), and reusability of the obtained material have been demonstrated.     

Alumoxane/ferroxane nanoparticles for the removal of viral pathogens: the importance of surface functionality to nanoparticle activity

A bi-functional nano-composite coating has been created on a porous Nomex? fabric support as a trap for aspirated virus contaminated water. Nomex? fabric was successively dip-coated in solutions containing cysteic acid functionalized alumina (alumoxane) nanoparticles and cysteic acid functionalized iron oxide (ferroxane) nanoparticles to form a nanoparticle coated Nomex? (NPN) fabric. From SEM and EDX the nanoparticle coating of the Nomex? fibers is uniform, continuous, and conformal. The NPN was used as a filter for aspirated bacteriophage MS2 viruses using end-on filtration. All measurements were repeated to give statistical reliability. The NPN fabrics show a large decrease as compared to Nomex? alone or alumoxane coated Nomex?. An increase in the ferroxane content results in an equivalent increase in virus retention. This suggests that it is the ferroxane that has an active role in deactivating and/or binding the virus. Heating the NPN to 160 °C results in the loss of cysteic acid functional groups (without loss of the iron nanoparticle's core structure) and the resulting fabric behaves similar to that of untreated Nomex?, showing that the surface functionalization of the nanoparticles is vital for the surface collapse of aspirated water droplets and the absorption and immobilization of the MS2 viruses. Thus, for virus immobilization, it is not sufficient to have iron oxide nanoparticles per se, but the surface functionality of a nanoparticle is vitally important in ensuring efficacy.     

Fabrication and characterization of zinc oxide nanoparticle coated magnetic iron oxide: Effect of S-layers adsorption on surface of oxide

Mixed zinc oxide nanoparticle coated magnetic iron oxide has been prepared by a sol–gel and co-precipitation routes. Magnetic iron oxide nanoparticles were synthesized by co-precipitation of ferric and ferrous ions with ammonia, and then zinc oxide was coated onto the surface of magnetic iron oxide by hydrolysis of zinc precursors. As a result, zinc oxide coated magnetic iron oxide nanoparticles with an average size of 68 nm were obtained. The crystalline bacterial cell surface layer)S-layer (used in this study was isolated from Lactobacillus helveticus ATCC 12046. The S-layer was adsorbed onto the surface of zinc oxide nanoparticle coated magnetic iron oxide. The nanoparticles were analyzed by X-ray powder diffractometry (XRD), infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM) were used to characterize the structural and the chemical features of the nanocomposites. The infrared spectra indicate that the S-layer-nanoparticle interaction occurs. This novel nanoparticle showed admirable potential in adsorption of S-layers on the surface of oxides for drug delivery.     

Green synthesis of copper oxide nanoparticles: Characterization and applications for environmental and biomedical fields

In recent years, there has been an increasing interest in the development of plant-based nanoparticles due to their numerous benefits over conventional physio-chemical methods, including sustainability and environmental safety. Green synthesis, a process that produces safe and sustainable goods without the use of harsh chemicals or other harmful processes, is gaining popularity. The current study focuses on the green synthesis of copper oxide nanoparticles using Piper nigrum leaf extracts, their characterization, and applications. The synthesis of nanoparticles was confirmed by changes in colour, further endorsed by UV–visible spectroscopy. Copper oxide (CuO) nanoparticles were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). CuO nanoparticle sizes ranged between 58.23 and 69.89 nm and were spherical in shape. FTIR results indicated a functional group capped on the nanoparticle surface. The antibacterial activity of the copper oxide nanoparticles was tested, and they exhibited the significant decrease in bacterial concentration and the largest zone of inhibition, making them an efficient disinfectant. Antimicrobial activity against Bacillus subtilis and Escherichia coli was observed. Furthermore, the synthesized CuO nanoparticles exhibited a high affinity for safranin dyes and demonstrated maximum removal efficiency. This makes them an effective agent for removing dyes in wastewater from industries such as clothing manufacturing. Safranin dye was successfully removed with an efficiency of 78% using nanoparticles. In conclusion, the green synthesis of copper oxide nanoparticles using plant extracts presents an eco-friendly and sustainable approach for producing nanoparticles with a wide range of potential applications.     

Controlling transport and chemical functionality of magnetic nanoparticles

A wide range of metal, magnetic, semiconductor, and polymer nanoparticles with tunable sizes and properties can be synthesized by wet-chemical techniques. Magnetic nanoparticles are particularly attractive because their inherent superparamagnetic properties make them desirable for medical imaging, magnetic field assisted transport, and separations and analyses. With such applications on the horizon, synthetic routes for quickly and reliably rendering magnetic nanoparticle surfaces chemically functional have become an increasingly important focus. This Account describes common synthetic routes for making and functionalizing magnetic nanoparticles and discusses initial applications in magnetic field induced separations. The most widely studied magnetic nanoparticles are iron oxide (Fe2O3 and Fe3O4), cobalt ferrite (CoFe 2O4), iron platinum (FePt), and manganese ferrite (MnFe 2O4), although others have been investigated. Magnetic nanoparticles are typically prepared under either high-temperature organic phase or aqueous conditions, producing particles with surfaces that are stabilized by attached surfactants or associated ions. Although it requires more specialized glassware, high-temperature routes are generally preferred when a high degree of stability and low particle size dispersity is desired. Particles can be further modified with a secondary metal or polymer to create core-shell structures. The outer shells function as protective layers for the inner metal cores and alter the surface chemistry to enable postsynthetic modification of the surfactant chemistry. Efforts by our group as well as others have centered on pathways to yield nanoparticles with surfaces that are both easily functionalized and tunable in terms of the number and variety of attached species. Ligand place-exchange reactions have been shown quite successful for exchanging silanes, acids, thiols, and dopamine ligands onto the surfaces of some magnetic particles. Poly(ethylene oxide)-modified phospholipids can be inserted into nonpolar surface monolayers of as-prepared nanoparticles as a method for modifying the surface chemistry that induces water solubility. In general, reactive termini can subsequently be used to append a range of chemical groups. For example, surfactants with trifluoroethylester or azide termini have been used to attach a range of amine- or alkyne-containing species, respectively. Chemically functionalized magnetic nanoparticles are promising as advanced materials for analytical separations and analysis. Magnetic field flow fractionation leverages the size-dependent magnetic moments to purify and separate the components of a complex mixture of particles. Similarly, magnetic field gradients are useful for manipulating transport and separation in simple microfluidic devices. By either approach, magnet-induced transport of the particles is a simple method in which an attached reagent, catalyst, or bioanalytical tag can be moved between flow streams within a lab on a chip device.     

Multifunctional ferritin cage nanostructures for fluorescence and MR imaging of tumor cells

Bionanoparticles and nanostructures have attracted increasing interest as versatile and promising tools in many applications including biosensing and bioimaging. In this study, to image and detect tumor cells, ferritin cage-based multifunctional hybrid nanostructures were constructed that: (i) displayed both the green fluorescent protein and an Arg-Gly-Asp peptide on the exterior surface of the ferritin cages; and (ii) incorporated ferrimagnetic iron oxide nanoparticles into the ferritin interior cavity. The overall architecture of ferritin cages did not change after being integrated with fusion proteins and ferrimagnetic iron oxide nanoparticles. These multifunctional nanostructures were successfully used as a fluorescent imaging probe and an MRI contrast agent for specifically probing and imaging α(v)β(3) integrin upregulated tumor cells. The work provides a promising strategy for tumor cell detection by simultaneous fluorescence and MR imaging.     

Frequency-Dependent Magnetic Susceptibility of Magnetite and Cobalt Ferrite Nanoparticles Embedded in PAA Hydrogel

Chemically responsive hydrogels with embedded magnetic nanoparticles are of interest for biosensors that magnetically detect chemical changes. A crucial point is the irreversible linkage of nanoparticles to the hydrogel network, preventing loss of nanoparticles upon repeated swelling and shrinking of the gel. Here, acrylic acid monomers are adsorbed onto ferrite nanoparticles, which subsequently participate in polymerization during synthesis of poly(acrylic acid)-based hydrogels (PAA). To demonstrate the fixation of the nanoparticles to the polymer, our original approach is to measure low-field AC magnetic susceptibility spectra in the 0.1 Hz to 1 MHz range. In the hydrogel, the magnetization dynamics of small iron oxide nanoparticles are comparable to those of the particles dispersed in a liquid, due to fast Néel relaxation inside the particles; this renders the ferrogel useful for chemical sensing at frequencies of several kHz. However, ferrogels holding thermally blocked iron oxide or cobalt ferrite nanoparticles show significant decrease of the magnetic susceptibility resulting from a frozen magnetic structure. This confirms that the nanoparticles are unable to rotate thermally inside the hydrogel, in agreement with their irreversible fixation to the polymer network.     

Enhanced Magnetic Hyperthermia of Magnetoferritin through Synthesis at Elevated Temperature

Iron oxide nanoparticles have attracted a great deal of research interest in recent years for magnetic hyperthermia therapy owing to their biocompatibility and superior thermal conversion efficiency. Magnetoferritin is a type of biomimetic superparamagnetic iron oxide nanoparticle in a ferritin cage with good monodispersity, biocompatibility, and natural hydrophilicity. However, the magnetic hyperthermic efficiency of this kind of nanoparticle is limited by the small size of the mineral core as well as its low synthesis temperature. Here, we synthesized a novel magnetoferritin particle by using a recombinant ferritin from the hyperthermophilic archaeon Pyrococcus furiosus as a template with high iron atom loading of 9517 under a designated temperature of 90 °C. Compared with the magnetoferritins synthesized at 45 and 65 °C, the one synthesized at 90 °C displays a larger average magnetite and/or maghemite core size of 10.3 nm. This yields an increased saturation magnetization of up to 49.6 emu g⁻¹ and an enhanced specific absorption rate (SAR) of 805.3 W g⁻¹ in an alternating magnetic field of 485.7 kHz and 49 kA m⁻¹. The maximum intrinsic loss power (ILP) value is 1.36 nHm² kg⁻¹. These results provide new insights into the biomimetic synthesis of magnetoferritins with enhanced hyperthermic efficiency and demonstrate the potential application of magnetoferritin in the magnetic hyperthermia of tumors.     

Irreversible changes in protein conformation due to interaction with superparamagnetic iron oxide nanoparticles

The understanding of the interactions between nanomaterials and proteins is of extreme importance in medicine. In a biological fluid, proteins can adsorb and associate with nanoparticles, which can have significant impact on the biological behavior of the proteins and the nanoparticles. We report here on the interactions of iron saturated human transferrin protein with both bare and polyvinyl alcohol coated superparamagnetic iron oxide nanoparticles (SPIONs). The exposure of human transferrin to SPIONs results in the release of iron, which changes the main function of the protein, which is the transport of iron among cells. After removal of the magnetic nanoparticles, the original protein conformation is not recovered, indicating irreversible changes in transferrin conformation: from a compact to an open structure.     

Materials Characterization of Feraheme/Ferumoxytol and Preliminary Evaluation of Its Potential for Magnetic Fluid Hyperthermia

Feraheme, is a recently FDA-cleared superparamagnetic iron oxide nanoparticle (SPION)-based MRI contrast agent that is also employed in the treatment of iron deficiency anemia. Feraheme nanoparticles have a hydrodynamic diameter of 30 nm and consist of iron oxide crystallites complexed with a low molecular weight, semi-synthetic carbohydrate. These features are attractive for other potential biomedical applications such as magnetic fluid hyperthermia (MFH), since the carboxylated polymer coating affords functionalization of the particle surface and the size allows for accumulation in highly vascularized tumors via the enhanced permeability and retention effect. This work presents morphological and magnetic characterization of Feraheme by transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDX), and superconducting quantum interference device (SQUID) magnetometry. Additionally, the results of an initial evaluation of the suitability of Feraheme for MFH applications are described, and the data indicate the particles possess promising properties for this application.     

Iron oxide-based superparamagnetic polymeric nanomaterials: Design, preparation, and biomedical application

Recent advances in the development and biological applications of polymeric nanomaterials embedded with superparamagnetic iron oxide nanoparticles (SIONPs) are summarized. Novel SIONP-polymer hybrid nanoparticles are prepared by various methods, including direct modification with polymers, surface-initiated controlled polymerization, inorganic silica/polymer hybridization, self-assembly, self-association, and various heterogeneous polymerization methods. They have potential for various biomedical applications, including magnetic resonance imaging (MRI) contrast enhancement, targeted drug delivery, hyperthermia, biological separation, protein immobilization, and biosensors.     

Magnetically separable bimodal mesoporous carbons with a large capacity for the immobilization of biomolecules

A method for the fabrication of carbon-based mesoporous magnetic composites with a large capacity for the adsorption/immobilization of biomolecules is presented. The composites consist of iron oxide spinel nanoparticles inserted into the pores of templated unimodal or bimodal mesoporous carbons. The deposition of the magnetic iron oxide nanoparticles was carried out following two synthetic routes: (1) the direct incorporation of nanoparticles into the pores of the templated carbons and (2) the insertion of nanoparticles into the mesopores of the carbon-silica composite followed by the selective removal of silica framework. The carbon-iron oxide magnetic composites prepared according to route 2 were found to have better textural properties (larger BET surface areas and pore volumes) and significantly higher capacity for the adsorption of hemoglobin and immobilization of lysozyme. The amounts of hemoglobin or lysozyme adsorbed/immobilized by these materials were 176 mg hemoglobin g⁻¹ support and 131 mg lysozyme g⁻¹ support using route 1 and 430 mg hemoglobin g⁻¹ support and 322 mg lysozyme g⁻¹ support by route 2. Furthermore, we have demonstrated that, when no inorganic nanoparticles are deposited, the bimodal mesoporous carbon shows exceptionally a large immobilization capacity for hemoglobin (830 mg g⁻¹ support) and lysozyme (510 mg g⁻¹).     

A cerium oxide nanoparticle-based device for the detection of chronic inflammation via optical and magnetic resonance imaging

Monitoring of microenvironmental parameters is critical in healthcare and disease management. Harnessing the antioxidant activity of nanoceria and the imaging capabilities of iron oxide nanoparticles in a device setup, we were able to image changes in the device's aqueous milieu. The device was able to convey and process changes in the microenvironment's pH and reactive oxygen species' concentration, distinguishing physiological from abnormal levels. As a result under physiological and transient inflammatory conditions, the device's fluorescence and magnetic resonance signals, emanating from multimodal iron oxide nanoparticles, were similar. However, under chronic inflammatory conditions that are usually associated with high local concentrations of reactive oxygen species and pH decrease, the device's output was considerably different. Specifically, the device's fluorescence emission significantly decreased, while the magnetic resonance signal T2 increased. Further studies identified that the changes in the device's output are attributed to inactivation of the sensing component's nanoceria that prevents it from successfully scavenging the generated free radicals. Interestingly, the buildup of free radical excess led to polymerization of the iron oxide nanoparticle's coating, with concomitant formation of micron size aggregates. Our studies indicate that a nanoceria-based device can be utilized for the monitoring of pro-inflammatory biomarkers, having important applications in the management of numerous ailments while eliminating nanoparticle toxicity issues.     

Facile and high-efficient immobilization of histidine-tagged multimeric protein G on magnetic nanoparticles

This work reports the high-efficient and one-step immobilization of multimeric protein G on magnetic nanoparticles. The histidine-tagged (His-tag) recombinant multimeric protein G was overexpressed in Escherichia coli BL21 by the repeated linking of protein G monomers with a flexible linker. High-efficient immobilization on magnetic nanoparticles was demonstrated by two different preparation methods through the amino-silane and chloro-silane functionalization on silica-coated magnetic nanoparticles. Three kinds of multimeric protein G such as His-tag monomer, dimer, and trimer were tested for immobilization efficiency. For these tests, bicinchoninic acid (BCA) assay was employed to determine the amount of immobilized His-tag multimeric protein G. The result showed that the immobilization efficiency of the His-tag multimeric protein G of the monomer, dimer, and trimer was increased with the use of chloro-silane-functionalized magnetic nanoparticles in the range of 98% to 99%, rather than the use of amino-silane-functionalized magnetic nanoparticles in the range of 55% to 77%, respectively.     

Development and Application of a Label-Free Fluorescence Method for Determining the Composition of Gold Nanoparticle–Protein Conjugates

A method was developed for determining the composition of the conjugates between gold nanoparticles and proteins based on the intrinsic fluorescence of unbound protein molecules. The fluorescence was evaluated after separation of the conjugates from the reaction mixture by centrifugation. Gold nanoparticles obtained using the citrate technique (average diameter 24 nm) were conjugated at pH 5.4 with the following four proteins: human immunoglobulin G (IgG), bovine serum albumin (BSA), recombinant streptococcal protein G (protein G), and Kunitz-type soybean trypsin inhibitor (STI). The compositions of these conjugates were determined using the developed method. The conjugate compositions were dependent on the concentration of the added protein, and in all cases reached saturation. The equilibrium dissociation constants of the gold nanoparticle conjugates with IgG, BSA, protein G, STI in the initial section of the concentration dependence curve were 4, 6, 10, and 15 nM, respectively. Close to saturation, the corresponding values were 25, 76, 175, and 100 nM, respectively. The maximal binding capacities of a single gold nanoparticle for IgG, BSA, Protein G, and STI were 52, 90, 500, and 550, respectively, which agrees well with the hypothesis of monolayer immobilization.     

磁性壳聚糖微球的研究进展

磁性氧化铁纳米粒子（Fe3O4,γ-Fe2O3等）因具有尺寸小、超顺磁性和低毒性等特点,已经引起了生物化工、医药工业研究领域的广泛关注。磁性壳聚糖微球具有表面非常光滑的球形结构。近年来,已经制备出了平均粒径在10～2.5×105 nm之间的磁性壳聚糖微球,并在生物医药、食品工程和污水处理等许多领域已经取得了初步的应用,特别是在污水处理和酶固定化领域。本文综述了近年来磁性氧化铁纳米粒子和磁性壳聚糖微球的制备方法、磁性壳聚糖微球的改性方法及应用的最新研究成果。     

Carbon-coated iron oxide nanoparticles as contrast agents in magnetic resonance imaging

Coprecipitated ferrite nanoparticles were coated with carbon using a hydrothermal method. From transmission electron microscope pictures, we could see that the coated iron oxide nanoparticles were spherical in shape with an average diameter of 90 nm. The strong bonding of carbon on the nanoparticle surfaces was checked by noting the C = O and C = C vibrations in Fourier transform infrared spectra. The spin-lattice relaxation process [T ₁] and spin-spin relaxation process [T ₂] relaxivities of hydrogen protons in the aqueous solution of coated nanoparticles were determined to be 1.139 (mM·s)^-1 and 1.115 (mM·s)^-1, respectively. These results showed that the carbon-coated iron oxide nanoparticles are applicable as both T ₁ and T ₂ contrast agents in magnetic resonance imaging.     

Scanning pulsed laser ablation in liquids: An alternative route to obtaining biocompatible YbFe nanoparticles as multiplatform contrast agents for combined MRI and CT imaging

Ytterbium ferrites are being used in many promising applications, such as visible-light photocatalysis, solar cells, magnetooptic devices, electro-magnetic equipment, etc., due to their fantastic ferroelectric and ferromagnetic properties. However, despite their good magnetic and radiopaque features, the use of ytterbium ferrites as multiplatform contrast agents in magnetic resonance imaging (MRI) and X-ray computed tomography (CT) is still under-developed. This is mainly due to difficulties in obtaining stable and biocompatible aqueous colloidal dispersions of ytterbium ferrite nanoparticles. In order to overcome this limitation, this work explores an eco-friendly method to directly synthesize such dispersions by liquid-assisted pulsed laser ablation of ytterbium ferrite massive targets. First, orthorhombic bulk YbFeO₃ targets were obtained by a reaction-sintering method. Then, colloidal dispersions of nanoparticles were produced directly in both distilled water and ethanol by irradiating the bulk YbFeO₃ targets with high-power infrared nanosecond lasers pulses. A battery of techniques has been used to characterize the as synthesized YbFeO₃ targets and colloidal dispersions of YbFe nanoparticles to determine their composition, structure, magnetic properties, X-ray attenuation potentials, and colloidal properties. Moreover, the biocompatibility of the systems was also analysed by MTT cell viability assay. Results indicated that the use of distilled water as ablation medium yields colloidal dispersions consisted mainly of paramagnetic ytterbium ferrite nanoparticles. Contrarily, the use of ethanol as solvent leads to colloidal dispersions of polycrystalline nanoparticles with both ferromagnetic and paramagnetic behaviour, due to the coexistence, in each nanoparticle, of ytterbium ferrite, ytterbium oxide, and iron oxide crystalline phases. Both colloidal dispersions exhibit also high biocompatibility and suitable X-ray attenuation properties. Moreover, they show bio-safe hydrodynamic sizes (lower than 200 nm) with acceptable overall hydrodynamic polydispersity index values (under 0.4), being stable in water for several weeks. These results pave the way for the future evaluation of Yb–Fe based nanoparticles as multiplatform contrast agents in multimodal MRI and CT imaging.     

Synergistically integrated nanoparticles as multimodal probes for nanobiotechnology

Current biomedical imaging techniques including magnetic resonance imaging (MRI), positron emission tomography (PET), and computed X-ray tomography (CT) are vital in the diagnosis of various diseases. Each imaging modality has its own merits and disadvantages, and a single technique does not possess all the required capabilities for comprehensive imaging. Therefore, multimodal imaging methods are quickly becoming important tools for state-of-the-art biomedical research and clinical diagnostics and therapeutics. In this Account, we will discuss synergistically integrated nanoparticle probes, which will be an essential tool in multimodal imaging technology. When inorganic nanoparticles are introduced into biological systems, their extremely small size and their exceptional physical and chemical properties make them useful probes for biological diagnostics. Nanoparticle probes can endow imaging techniques with enhanced signal sensitivity, better spatial resolution, and the ability to relay information about biological systems at the molecular and cellular levels. Simple magnetic nanoparticles function as MRI contrast enhancement probes. These magnetic nanoparticles can then serve as a core platform for the addition of other functional moieties including fluorescence tags, radionuclides, and other biomolecules for multimodal imaging, gene delivery, and cellular trafficking. For example, MRI-optical dual-modal probes composed of a fluorescent dye-doped silica (DySiO(2)) core surrounded by magnetic nanoparticles can macroscopically detect neuroblastoma cancer cells via MRI along with subcellular information via fluorescence imaging. Magnetic nanoparticles can also be coupled to radionuclides ((124)I) to construct MRI-PET dual-modal probes. Such probes can accurately detect lymph nodes (LNs), which are critical for assessing cancer metastasis. In vivo MRI/PET images can clearly identify small (approximately 3 mm) LNs along with precise anatomical information. Systems using multicomponent nanoparticles modified with biomolecules can also monitor gene expression and other markers in cell therapeutics studies. We have used hybrid stem cell-magnetic nanoparticle probes with MRI to monitor in vivo stem cell trafficking. MRI with hybrid probes of magnetic nanoparticles and adenovirus can detect target cells and can monitor gene delivery and the expression of green fluorescent proteins optically. Each component of such multimodal probes complements the other modalities, and their synergistic materials properties ultimately provide more accurate information in in vitro and in vivo biological systems.