磁性铁氧化物纳米粒子制备及其体内应用研究

磁性铁氧化物纳米粒子由于其生物相容性和低毒性而广泛的应用于生物医学领域。本文总结了近年来制备各种磁性铁氧化物纳米粒子的方法,比较了它们在粒径、结晶度以及制备条件等方面的优缺点,概括了对其进行表面修饰改性材料的种类,阐述近年来磁性铁氧化物纳米粒子在体内应用中药物运输、磁共振成像、磁热疗方面的进展,并指出当前应用中的主要方向和亟待解决的问题。     

Ultra magnetic liposomes for MR imaging, targeting, and hyperthermia

Magnetic liposomes offer opportunities as theranostic systems. The prerequisite for efficient imaging, tissue targeting or hyperthermia is high magnetic load of these vesicles. Here we describe the preparation of Ultra Magnetic Liposomes (UMLs), which may encapsulate iron oxide nanoparticles in a volume fraction of up to 30%. This remarkable magnetic charge provides UMLs with high magnetic mobilities, MRI relaxivities, and heating capacities for magnetic hyperthermia. Moreover, these UMLs are rapidly and efficiently internalized by cultured tumor cells and, when they are administered to mice, they can be vectorized to tumors by an external magnet.     

Magnetofection: Magic magnetic nanoparticles for efficient gene delivery

Magnetic nanoparticles (MNPs) have become a research hotspot and widely used in the biomedical field in recent decades due to their unique magnetic properties. This minireview summarizes the specific gene transfection of magnetic particles (magnetofection) during eversy dynamic process of gene delivery (gene binding, cellular uptake, endosomal escape, intracellular trafficking and in vivo targeting). Meanwhile, the synergistic biomedical application of magnetofection and the effects of MNPs have also been discussed, including magnetic resonance imaging (MRI), magnetic mediated hyperthermia (MMH), Fenton reaction and autophagy. Finally, the clinical prospect of magnetofection was briefly expected.     

Magnetofection: Magic magnetic nanoparticles for efficient gene delivery

Magnetic nanoparticles (MNPs) have become a research hotspot and widely used in the biomedical field in recent decades due to their unique magnetic properties. This minireview summarizes the specific gene transfection of magnetic particles (magnetofection) during eversy dynamic process of gene delivery (gene binding, cellular uptake, endosomal escape, intracellular trafficking and in vivo targeting). Meanwhile, the synergistic biomedical application of magnetofection and the effects of MNPs have also been discussed, including magnetic resonance imaging (MRI), magnetic mediated hyperthermia (MMH), Fenton reaction and autophagy. Finally, the clinical prospect of magnetofection was briefly expected.     

Biocompatibility and hyperthermia cancer therapy of casein‐coated iron oxide nanoparticles in mice

Magnetic nanoparticles (MNPs) can be used as heat generation source in cancer hyperthermia therapy. While iron oxide nanoparticles (NPs) are the most popular choice for magnetic hyperthermia, adding a surface enhancement can improve its performance. Furthermore, for MNPs to be used in biomedical application their cytotoxicity needs to be evaluated. In this study biocompatibility and also in vivo performance of casein‐coated MNPs were assessed. Cell viability of normal cell lines in all of tests remained above 95% for 0.5 and 1 mg/mL concentration and even the minimum recorded cell viability for normal cell lines was 84.78% at 20 mg/mL concentration. In contrast cell viability of cancer cell lines in contact with casein coated MNPs core‐shell structure except for one sample remained below 85%. By introduction of and alternating magnetic field, cell viability of samples with lower MNP concentration dropped by 20% to 30% while this drop for samples with higher concentration was 10% to 20%. Furthermore, results of in vivo trials show that just 1 week of hyperthermia treatment with casein coated MNPs core‐shell structure can reduce the tumor size of the mice by 33%. Real‐time polymerase chain reaction results further confirmed the effectiveness of this method. Moreover, findings of this study suggest that lower injection speed can improve NPs distribution and treatment effect. Results of this study suggest that core‐shell structure can positively affect the tumor growth and the combination of good biocompatibility, innate hostility toward cancer cells and good heating power makes them a good candidate for hyperthermia cancer therapy applications.     

Ultraparamagnetic Cells Formed through Intracellular Oxidation and Chelation of Paramagnetic Iron

Making cells magnetic is a long‐standing goal of chemical biology, aiming to enable the separation of cells from complex biological samples and their visualization in vivo using magnetic resonance imaging (MRI). Previous efforts towards this goal, focused on engineering cells to biomineralize superparamagnetic or ferromagnetic iron oxides, have been largely unsuccessful due to the stringent required chemical conditions. Here, we introduce an alternative approach to making cells magnetic, focused on biochemically maximizing cellular paramagnetism. We show that a novel genetic construct combining the functions of ferroxidation and iron chelation enables engineered bacterial cells to accumulate iron in “ultraparamagnetic” macromolecular complexes, allowing these cells to be trapped with magnetic fields and imaged with MRI in vitro and in vivo. We characterize the properties of these cells and complexes using magnetometry, nuclear magnetic resonance, biochemical assays, and computational modeling to elucidate the unique mechanisms and capabilities of this paramagnetic concept.     

Monodisperse Magnetite Nanoparticles Coupled with Nuclear Localization Signal Peptide for Cell‐Nucleus Targeting

Functionalization of monodisperse superparamagnetic magnetite (Fe₃O₄) nanoparticles for cell specific targeting is crucial for cancer diagnostics and therapeutics. Targeted magnetic nanoparticles can be used to enhance the tissue contrast in magnetic resonance imaging (MRI), to improve the efficiency in anticancer drug delivery, and to eliminate tumor cells by magnetic fluid hyperthermia. Herein we report the nucleus‐targeting Fe₃O₄ nanoparticles functionalized with protein and nuclear localization signal (NLS) peptide. These NLS‐coated nanoparticles were introduced into the HeLa cell cytoplasm and nucleus, where the particles were monodispersed and non‐aggregated. The success of labeling was examined and identified by fluorescence microscopy and MRI. The work demonstrates that monodisperse magnetic nanoparticles can be readily functionalized and stabilized for potential diagnostic and therapeutic applications.     

In vivo magnetic resonance detection of cancer by using multifunctional magnetic nanocrystals

The unique properties of magnetic nanocrystals provide them with high potential as key probes and vectors in the next generation of biomedical applications. Although superparamagnetic iron oxide nanocrystals have been extensively studied as excellent magnetic resonance imaging (MRI) probes for various cell trafficking, gene expression, and cancer diagnosis, further development of in vivo MRI applications has been very limited. Here, we describe in vivo diagnosis of cancer, utilizing a well-defined magnetic nanocrystal probe system with multiple capabilities, such as small size, strong magnetism, high biocompatibility, and the possession of active functionality for desired receptors. Our magnetic nanocrystals are conjugated to a cancer-targeting antibody, Herceptin, and subsequent utilization of these conjugates as MRI probes has been successfully demonstrated for the monitoring of in vivo selective targeting events of human cancer cells implanted in live mice. Further conjugation of these nanocrystal probes with fluorescent dye-labeled antibodies enables both in vitro and ex vivo optical detection of cancer as well as in vivo MRI, which are potentially applicable for an advanced multimodal detection system. Our study finds that high performance in vivo MR diagnosis of cancer is achievable by utilizing improved and multifunctional material properties of iron oxide nanocrystal probes.     

Carbon Dots as a New Class of Diamagnetic Chemical Exchange Saturation Transfer (diaCEST) MRI Contrast Agents

While carbon dots (C‐dots) have been extensively investigated pertaining to their fluorescent, phosphorescent, electrochemiluminescent, optoelectronic, and catalytic features, their inherent chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) properties are unknown. By virtue of their hydrophilicity and abundant exchangeable protons of hydroxyl, amine, and amide anchored on the surface, we report here that C‐dots can be adapted as effective diamagnetic CEST (diaCEST) MRI contrast agents. As a proof‐of‐concept demonstration, human glioma cells were labeled with liposomes with or without encapsulated C‐dots and implanted in mouse brain. In vivo CEST MRI was able to clearly differentiate labeled cells from non‐labeled cells. The present findings may encourage new applications of C‐dots for in vivo imaging in deep tissues, which is currently not possible using conventional fluorescent (near‐infrared) C‐dots.     

Magnetic fluid hyperthermia: focus on superparamagnetic iron oxide nanoparticles

Due to their unique magnetic properties, excellent biocompatibility as well as multi-purpose biomedical potential (e.g., applications in cancer therapy and general drug delivery), superparamagnetic iron oxide nanoparticles (SPIONs) are attracting increasing attention in both pharmaceutical and industrial communities. The precise control of the physiochemical properties of these magnetic systems is crucial for hyperthermia applications, as the induced heat is highly dependent on these properties. In this review, the limitations and recent advances in the development of superparamagnetic iron oxide nanoparticles for hyperthermia are presented.     

Magnetic nanoparticles--templated assembly of protein subunits: a new platform for carbohydrate-based MRI nanoprobes

A new approach for the preparation of carbohydrate-coated magnetic nanoparticles is reported. In a first step, we show that the pH-driven assembly-disassembly natural process that occurs in apoferritin protein is effective for the encapsulation of maghemite nanoparticles of different sizes: 4 and 6 nm. In a second step, we demonstrate that the presence of functional amine groups in the outer shell of apoferritin allows functionalization with two carbohydrates, N-acetyl-D-glucosamine and d-mannose. High-resolution electron microscopy (HREM), high angle annular dark field scanning electron microscopy (HAADF-STEM), electron energy loss spectroscopy (EELS), X-ray diffraction (XRD), and SQUID technique have been used to characterize the magnetic samples, termed herein Apomaghemites. The in vivo magnetic resonance imaging (MRI) studies showed the efficiency in contrasting images for these samples; that is, the r(2) NMR relaxivities are comparable with Endorem (a commercial superparamagnetic MRI contrast agent). The r(2) relaxivity values as well as the pre-contrast and post-contrast T(2)*-weighted images suggested that our systems could be used as perspective superparamagnetic contrast agents for magnetic resonance imaging (MRI). The carbohydrate-functionalized Apomaghemite nanoparticles retained their recognition abilities, as demonstrated by the strong affinity with their corresponding carbohydrate-binding lectins.     

In vitro magnetic hyperthermia response of iron oxide MNP’s incorporated in DA3, MCF-7 and HeLa cancer cell lines

In the current work, iron oxide magnetic nanoparticles (MNP’s) were synthesized by thermal decomposition of Fe(acac)₃-(iron acetylacetonate) compounds in high-boiling organic solvents containing stabilizing surfactants and examined as possible agents for magnetic hyperthermia treatment, according to their structural, magnetic and heating properties. Three different cancer cell lines (DA3, MCF-7 and HeLa cell lines) were used to assess the suitability of the MNP’s. The experimental results proved that the synthesized MNPs are non-toxic and the uptake efficiency was extremely good. Further, from in vitro hyperthermia results, very fast thermal response was observed (reaching hyperthermia levels in less than 200 s), which minimize the duration of the cell and human body exposure in a high frequency AC external magnetic field.      

Magnetic hyperthermia: Potentials and limitations

Despite the fact that the magnetic hyperthermia (MH) has been known for more than 75 years, it is still debated in its clinical applications. The generation of a higher temperature at a tumor is called hyperthermia. There is a different of temperature ranges going from 39 to 40 ?°C up to such high temperatures as 80–90 ?°C. However, due to its high potential, MH is used along with nanoparticles as heat intermediaries in the treatment of cancer. Many Magnetic Nanoparticles (MNPs) with several properties and morphological metallic structures have been useful to magnetics hyperthermia therapy. These MNPs are categorized into two groups; magnetic alloy nanoparticles (MANPs) and magnetic metal oxide nanoparticles (MMONPs). The principal challenges of this method are the control of local tumoral temperature and the increase in nanoparticles heating power. The hyperthermia agents derived from magnetic nanoparticles along with magnetic field. In the recent study, hyperthermia thought, dissimilar types of magnetic nanoparticles for hyperthermia, efficacy for cancer therapy, advances, challenges, and future chances have been examined.     

Linear assemblies of magnetic nanoparticles as MRI contrast agents

Using a one-step procedure we have prepared magnetic fluids comprising of polyelectrolyte stabilized magnetite nanoparticles. These nanocomposites are comprised of linear, chain-like assemblies of magnetic nanoparticles, which can be aligned in parallel arrays by an external magnetic field. We have shown the potential use of these materials as contrast agents by measuring their MR response in live rats. The new magnetic fluids have demonstrated good biocompatibility and potential for in vivo MRI diagnostics.     

Magnetic nanosensor particles in luminescence upconversion capability

Nanoparticles (NPs) exhibit interesting size-dependent electrical, optical, magnetic, and chemical properties that cannot be observed in their bulk counterparts. The synthesis of NPs (i.e., crystalline particles ranging in size from 1 to 100 nm) has been intensely studied in the past decades. Magnetic nanoparticles (MNPs) form a particularly attractive class of NPs and have found numerous applications such as in magnetic resonance imaging to visualize cancer, cardiovascular, neurological and other diseases. Other uses include drug targeting, tissue imaging, magnetic immobilization, hyperthermia, and magnetic resonance imaging. MNPs, due to their magnetic properties, can be easily separated from (often complex) matrices and manipulated by applying external magnetic field. Near-infrared to visible upconversion luminescent nanoparticles (UCLNPs) form another type of unusual nanoparticles. They are capable of emitting visible light upon NIR light excitation. Lanthanide-doped (Yb, Er) hexagonal NaYF? UCLNPs are the most efficient upconversion phosphors known up to now. The use of UCLNPs for in vitro imaging of cancer cells and in vivo imaging in tissues has been demonstrated. UCLNPs show great potential as a new class of luminophores for biological, biomedical, and sensor applications. We are reporting here on our first results on the combination of MNP and UCLNP technology within an ongoing project supported by the DFG and the FWF (Austria).     

Paramagnetic nanoparticle T(1) and T(2) MRI contrast agents

There is no doubt that magnetic resonance imaging contrast agents (MRI CAs) can play a vital role in diagnosing diseases. Therefore, demand for new MRI CAs with an enhanced sensitivity and advanced functionalities is very high. Here, paramagnetic nanoparticles (NPs) are reviewed as new potential candidates for either T(1) or T(2) MRI CAs or both. These include surface coated lanthanide (Ln) oxide NPs (Ln = Gd, Dy, and Ho) and manganese oxide NPs. Surface coating materials should be biocompatible and hydrophilic. Compared to conventional large NPs, these surface coated paramagnetic NPs can be made ultrasmall with core particle diameter ranging from 1 to 3 nm, but their magnetic properties are still sufficient for MRI CAs. At this particle diameter, they can be easily excreted from the body through the renal system, which is prerequisite for in vivo applications. Mixed lanthanide oxide NPs into which a fluorescent Ln material is incorporated will be valuable as multiple imaging agents for both MRI-fluorescent imaging (FI) and MRI-cellular imaging (CL). These paramagnetic NPs can be further functionalized towards target-specific imaging, multiplex imaging, and drug delivery.     

Spatially Resolved Quantification of Gadolinium(III)‐Based Magnetic Resonance Agents in Tissue by MALDI Imaging Mass Spectrometry after In Vivo MRI

Gadolinium(III)‐based contrast agents improve the sensitivity and specificity of magnetic resonance imaging (MRI), especially when targeted contrast agents are applied. Because of nonlinear correlation between the contrast agent concentration in tissue and the MRI signal obtained in vivo, quantification of certain biological or pathophysiological processes by MRI remains a challenge. Up to now, no technology has been able to provide a spatially resolved quantification of MRI agents directly within the tissue, which would allow a more precise verification of in vivo imaging results. MALDI imaging mass spectrometry for spatially resolved in situ quantification of gadolinium(III) agents, in correlation to in vivo MRI, were evaluated. Enhanced kinetics of Gadofluorine M were determined dynamically over time in a mouse model of myocardial infarction. MALDI imaging was able to corroborate the in vivo imaging MRI signals and enabled in situ quantification of the gadolinium probe with high spatial resolution.     

Synthesis,functionalization, and nanomedical applications of functional magnetic nanoparticles

This review summarizes the current synthesis of magnetic nanoparticles (MNPs) preparation, functionalization and stabilization methods. And furthermore it highlights some actual case analyses of these MNPs for disease therapy, drug delivery, hyperthermia, bioseparation and bioimaging applications.     

A Smart,Autocatalytic, DNAzyme Biocircuit for in Vivo,Amplified, MicroRNA Imaging

DNAzymes have been recognized as promising transducing agents for visualizing endogenous biomarkers, but their inefficient intracellular delivery and limited amplification capacity (including insufficient cofactor supply) preclude their extensive biological application. Herein, an autocatalytic DNAzyme (ACD) biocircuit is constructed for amplified microRNA imaging in vivo based on a hybridization chain reaction (HCR) and DNAzyme biocatalysis, sustained by a honeycomb MnO₂ nanosponge (hMNS). The hMNS not only delivers DNA probes, but also supplies Mn²⁺ as a DNAzyme cofactor and magnetic resonance imaging (MRI) agent. Through the subsequent cross‐activation of HCR and DNAzyme amplicons, the ACD amplifies the limited signal resulting from miRNA recognition. The hMNS/ACD system was used to image microRNA in vivo, thus demonstrating its great promise in cancer diagnosis.     

A Smart,Autocatalytic, DNAzyme Biocircuit for in Vivo,Amplified, MicroRNA Imaging

DNAzymes have been recognized as promising transducing agents for visualizing endogenous biomarkers, but their inefficient intracellular delivery and limited amplification capacity (including insufficient cofactor supply) preclude their extensive biological application. Herein, an autocatalytic DNAzyme (ACD) biocircuit is constructed for amplified microRNA imaging in vivo based on a hybridization chain reaction (HCR) and DNAzyme biocatalysis, sustained by a honeycomb MnO₂ nanosponge (hMNS). The hMNS not only delivers DNA probes, but also supplies Mn²⁺ as a DNAzyme cofactor and magnetic resonance imaging (MRI) agent. Through the subsequent cross-activation of HCR and DNAzyme amplicons, the ACD amplifies the limited signal resulting from miRNA recognition. The hMNS/ACD system was used to image microRNA in vivo, thus demonstrating its great promise in cancer diagnosis.