Up-converting β-NaY0.8[Yb0.18Er0.02]F4 nanoparticles coated by superparamagnetic γ-Fe2O3 nanosatellites: elaboration, characterization and in vitro cytotoxicity

Current biomedical imaging techniques are vital for the diagnosis of various diseases. They are related to the development of multimodal probes encompassing all the functionalities required for comprehensive imaging. In this context, we applied a simple and reproducible wet synthesis route to produce such probes. This method allowed us to prepare about 100 nm sized lanthanide-doped yttrium fluoride nanoparticles β-NaY0.8[Yb0.18Er0.02]F4, coated with about 10 nm sized iron oxide γ-Fe2O3 nanocrystals. By this way, the built granular hetero-nanostructures combine desirable up-converting photoluminescence (the core) and superparamagnetic properties (the satellites), enabling dual optical and magnetic resonance imaging applications. Through citrate ligand grafting, the designed core-satellite particles formed stable aqueous colloids, which are valuable for biomedical applications. Optical spectroscopy and confocal microscopy revealed their capability for sustained visible light emission (predominantly green) upon near-infrared excitation (980 nm). Additionally, based on XTT assays, when incubated for 24 hours with mammalian healthy or cancer cells, even at doses as high as 0.1 mg mL-1 (milligrams of particles), they did not induce significant cytotoxicity. The measured body temperature magnetization of the engineered nanoconstructs was found to be about 10 emu g-1 (grams of particles) at 1.5 T, which is high enough to use them as positive or negative contrast magnetic resonance agents in the clinic, as confirmed by relaxometry measurements in Milli-Q water. This result underscores their promising biomedical utility as bimodal probes for optical and magnetic imaging.

Prussian Blue Staining to Visualize Iron Oxide Nanoparticles

Iron deposits in cells and tissues can be detected by ex vivo histological examination through the Prussian blue (PB) staining. This practical, inexpensive, and highly sensitive technique involves the treatment of fixed tissue sections and cells with acid solutions of ferrocyanides that combine with ferric ion forming a bright blue pigment (i.e., ferric ferrocyanide). The staining can be applied to visualize iron oxide nanoparticles (IONPs), versatile magnetic nanosystems that are used in various biomedical applications and whose localization is usually required at a higher resolution than that enabled by in vivo tracking techniques.

Histochemistry for nanomedicine: Novelty in tradition

During the last two centuries, histochemistry has provided significant advancements in many fields of life sciences. After a period of neglect due to the great development of biomolecular techniques, the histochemical approach has been reappraised and is now widely applied in the field of nanomedicine. In fact, the novel nanoconstructs intended for biomedical purposes must be visualized to test their interaction with tissue and cell components. To this aim, several long-established staining methods have been re-discovered and re-interpreted in an unconventional way for unequivocal identification of nanoparticulates at both light and transmission electron microscopy.

Novel Nanoparticle-Based Cancer Treatment, Effectively Inhibits Lung Metastases and Improves Survival in a Murine Breast Cancer Model

Sarah Nanoparticles (SaNPs) are unique multicore iron oxide-based nanoparticles, developed for the treatment of advanced cancer, following standard care, through the selective delivery of thermal energy to malignant cells upon exposure to an alternating magnetic field. For their therapeutic effect, SaNPs need to accumulate in the tumor. Since the potential accumulation and associated toxicity in normal tissues are an important risk consideration, biodistribution and toxicity were assessed in naïve BALB/c mice. Therapeutic efficacy and the effect on survival were investigated in the 4T1 murine model of metastatic breast cancer. Toxicity evaluation at various timepoints did not reveal any abnormal clinical signs, evidence of alterations in organ function, nor histopathologic adverse target organ toxicity, even after a follow up period of 25 weeks, confirming the safety of SaNP use. The biodistribution evaluation, following SaNP administration, indicated that SaNPs accumulate mainly in the liver and spleen. A comprehensive pharmacokinetics evaluation, demonstrated that the total percentage of SaNPs that accumulated in the blood and vital organs was ~78%, 46%, and 36% after 4, 13, and 25 weeks, respectively, suggesting a time-dependent clearance from the body. Efficacy studies in mice bearing 4T1 metastatic tumors revealed a 49.6% and 70% reduction in the number of lung metastases and their relative size, respectively, in treated vs. control mice, accompanied by a decrease in tumor cell viability in response to treatment. Moreover, SaNP treatment followed by alternating magnetic field exposure significantly improved the survival rate of treated mice compared to the controls. The median survival time was 29 ± 3.8 days in the treated group vs. 21.6 ± 4.9 days in the control, p-value 0.029. These assessments open new avenues for generating SaNPs and alternating magnetic field application as a potential novel therapeutic modality for metastatic cancer patients.

In vivo Cell Tracking Using Non-invasive Imaging of Iron Oxide-Based Particles with Particular Relevance for Stem Cell-Based Treatments of Neurological and Cardiac Disease

Stem cell-based therapeutics is a rapidly developing field associated with a number of clinical challenges. One such challenge lies in the implementation of methods to track stem cells and stem cell-derived cells in experimental animal models and in the living patient. Here, we provide an overview of cell tracking in the context of cardiac and neurological disease, focusing on the use of iron oxide-based particles (IOPs) visualized in vivo using magnetic resonance imaging (MRI). We discuss the types of IOPs available for such tracking, their advantages and limitations, approaches for labeling cells with IOPs, biological interactions and effects of IOPs at the molecular and cellular levels, and MRI-based and associated approaches for in vivo and histological visualization. We conclude with reviews of the literature on IOP-based cell tracking in cardiac and neurological disease, covering both preclinical and clinical studies.

In vitro and in vivo experiments with iron oxide nanoparticles functionalized with DEXTRAN or polyethylene glycol for medical applications: magnetic targeting

In this research work, DEXTRAN- and polyethylene glycol (PEG)-coated iron-oxide superparamagnetic nanoparticles were synthetized and their cytotoxicity and biodistribution assessed. Well-crystalline hydrophobic Fe3 O4 SPIONs were formed by a thermal decomposition process with d = 18 nm and σ = 2 nm; finally, the character of SPIONs was changed to hydrophilic by a post-synthesis procedure with the functionalization of the SPIONs with PEG or DEXTRAN. The nanoparticles present high saturation magnetization and superparamagnetic behavior at room temperature, and the hydrodynamic diameters of DEXTRAN- and PEG-coated SPIONs were measured as 170 and 120 nm, respectively. PEG- and DEXTRAN-coated SPIONs have a Specific Power Absorption SPA of 320 and 400 W/g, respectively, in an ac magnetic field with amplitude of 13 kA/m and frequency of 256 kHz. In vitro studies using VERO and MDCK cell lineages were performed to study the cytotoxicity and cell uptake of the SPIONs. For both cell lineages, PEG- and DEXTRAN-coated nanoparticles presented high cell viability for concentrations as high as 200 μg/mL. In vivo studies were conducted using BALB/c mice inoculating the SPIONs intravenously and exposing them to the presence of an external magnet located over the tumour. It was observed that the amount of PEG-coated SPIONs in the tumor increased by up to 160% when using the external permanent magnetic as opposed to those animals that were not exposed to the external magnetic field.

Magnetic resonance imaging tracking of ferumoxytol-labeled human neural stem cells: studies leading to clinical use

Numerous stem cell-based therapies are currently under clinical investigation, including the use of neural stem cells (NSCs) as delivery vehicles to target therapeutic agents to invasive brain tumors. The ability to monitor the time course, migration, and distribution of stem cells following transplantation into patients would provide critical information for optimizing treatment regimens. No effective cell-tracking methodology has yet garnered clinical acceptance. A highly promising noninvasive method for monitoring NSCs and potentially other cell types in vivo involves preloading them with ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) to enable cell tracking using magnetic resonance imaging (MRI). We report here the preclinical studies that led to U.S. Food and Drug Administration approval for first-in-human investigational use of ferumoxytol to label NSCs prior to transplantation into brain tumor patients, followed by surveillance serial MRI. A combination of heparin, protamine sulfate, and ferumoxytol (HPF) was used to label the NSCs. HPF labeling did not affect cell viability, growth kinetics, or tumor tropism in vitro, and it enabled MRI visualization of NSC distribution within orthotopic glioma xenografts. MRI revealed dynamic in vivo NSC distribution at multiple time points following intracerebral or intravenous injection into glioma-bearing mice that correlated with histological analysis. Preclinical safety/toxicity studies of intracerebrally administered HPF-labeled NSCs in mice were also performed, and they showed no significant clinical or behavioral changes, no neuronal or systemic toxicities, and no abnormal accumulation of iron in the liver or spleen. These studies support the clinical use of ferumoxytol labeling of cells for post-transplant MRI visualization and tracking.

Inhalable magnetic nanoparticles for targeted hyperthermia in lung cancer therapy

Lung cancer (specifically, non-small cell lung cancer; NSCLC) is the leading cause of cancer-related deaths in the United States. Poor response rates and survival with current treatments clearly indicate the urgent need for developing an effective means to treat NSCLC. Magnetic hyperthermia is a non-invasive approach for tumor ablation, and is based on heat generation by magnetic materials, such as superparamagnetic iron oxide (SPIO) nanoparticles, when subjected to an alternating magnetic field. However, inadequate delivery of magnetic nanoparticles to tumor cells can result in sub-lethal temperature change and induce resistance while non-targeted delivery of these particles to the healthy tissues can result in toxicity. In our studies, we evaluated the effectiveness of tumor-targeted SPIO nanoparticles for magnetic hyperthermia of lung cancer. EGFR-targeted, inhalable SPIO nanoparticles were synthesized and characterized for targeting lung tumor cells as well as for magnetic hyperthermia-mediated antitumor efficacy in a mouse orthotopic model of NSCLC. Our results show that EGFR targeting enhances tumor retention of SPIO nanoparticles. Further, magnetic hyperthermia treatment using targeted SPIO nanoparticles resulted in significant inhibition of in vivo lung tumor growth. Overall, this work demonstrates the potential for developing an effective anticancer treatment modality for the treatment of NSCLC based on targeted magnetic hyperthermia.

Long-term multilayer adherent network (MAN) expansion, maintenance, and characterization, chemical and genetic manipulation, and transplantation of human fetal forebrain neural stem cells

Human neural stem/precursor cells (hNSC/hNPC) have been targeted for application in a variety of research models and as prospective candidates for cell-based therapeutic modalities in central nervous system (CNS) disorders. To this end, the successful derivation, expansion, and sustained maintenance of undifferentiated hNSC/hNPC in vitro, as artificial expandable neurogenic micro-niches, promises a diversity of applications as well as future potential for a variety of experimental paradigms modeling early human neurogenesis, neuronal migration, and neurogenetic disorders, and could also serve as a platform for small-molecule drug screening in the CNS. Furthermore, hNPC transplants provide an alternative substrate for cellular regeneration and restoration of damaged tissue in neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. Human somatic neural stem/progenitor cells (NSC/NPC) have been derived from a variety of cadaveric sources and proven engraftable in a cytoarchitecturally appropriate manner into the developing and adult rodent and monkey brain while maintaining both functional and migratory capabilities in pathological models of disease. In the following unit, we describe a new procedure that we have successfully employed to maintain operationally defined human somatic NSC/NPC from developing fetal, pre-term post-natal, and adult cadaveric forebrain. Specifically, we outline the detailed methodology for in vitro expansion, long-term maintenance, manipulation, and transplantation of these multipotent precursors.

Synthesis of superparamagnetic nanotubes as MRI contrast agents and for cell labeling

AIMS

Magnetic nanoparticles have been studied widely as MRI contrast agents to increase the sensitivity of this technique. This work describes the synthesis and characterization of magnetic nanotubes (MNTs) as a novel MRI contrast agent.

METHODS

MNTs with high saturation magnetization were fabricated by the synthesis of superparamagnetic iron oxide nanoparticles (SPIONs) directly in the pores of silica nanotubes (SNTs). The MNTs were characterized by electron microscopy, superconducting quantum interference device and MRI. Preliminary studies on in vitro cytotoxicity and cell labeling were carried out.

RESULTS

The MNTs retained the superparamagnetic characteristics in bulk solutions with a considerably high saturation magnetization of 95 emu/gFe. The nuclear magnetic resonance (NMR) relaxivities for MNTs of 500 nm in length and of 60 nm in diameter were r(1) = 1.6 +/- 0.3 mM(-1)s(-1) and r(2) = 264 +/- 56 mM(-1)s(-1) and, for the MNTs of 2 microm in length and 70 nm in diameter, the r(1) and r(2) were 3.0 +/- 1.3 and 358 +/- 65 mM(-1)s(-1), respectively. In vitro cell labeling showed promising results with excellent labeling efficiency. No cellular toxicity was observed in vitro.

CONCLUSIONS

The integration of SPIONs with SNTs imparts the superparamagnetic characteristics of SPIONs onto the SNTs, creating unique magnetic nanoparticles with multifunctionality. The MNTs showed promising results as a MRI contrast agent with high NMR relaxivities, little cytotoxicity and high cell-labeling efficiency.