Long term biotransformation and toxicity of dimercaptosuccinic acid-coated magnetic nanoparticles support their use in biomedical applications

Magnetic Seeding of SPIO-BMSCs Into a Biphasic Scaffold Can Promote Tendon-Bone Healing After Rotator Cuff Repair

BACKGROUND

The tendon-bone interface (TBI) in the rotator cuff has a poor intrinsic capacity for healing, which increases the risk of retear after rotator cuff repair (RCR). However, facilitating regeneration of the TBI still remains a great clinical challenge. Herein, the authors established a novel strategy based on magnetic seeding to enhance the TBI regeneration.

HYPOTHESIS

Magnetic seeding bone marrow mesenchymal stem cells labeled with superparamagnetic iron oxide (SPIO-BMSCs) into a biphasic scaffold can promote tendon-bone healing after RCR.

STUDY DESIGN

Controlled laboratory study.

METHODS

BMSCs were labeled with SPIOs. Prussian blue staining, CCK-8 tests, Western blot, and quantitative reverse transcription polymerase chain reaction (PCR) were used to determine the optimal effect concentration of SPIOs on cell bioactivities and abilities. Then SPIO-BMSCs were magnetically seeded into a biphasic scaffold under a magnetic field. The seeding efficacy was assessed by a scanning electron microscope, and the potential mechanism in chondrogenic differentiation after seeding SPIO-BMSCs into the scaffold was evaluated by Western blot and PCR. Furthermore, the effect of SPIO-BMSC/biphasic scaffold on tendon-bone healing after RCR using a rat model was examined using histological analysis, enzyme-linked immunosorbent assay, and biomechanical evaluation.

RESULTS

BMSCs labeled with 100 μg/mL SPIO had no effect on cell bioactivities and the ability of chondrogenic differentiation. SPIO-BMSCs were magnetically seeded into a biphasic scaffold, which offered a high seeding efficacy to enhance chondrogenic differentiation of SPIO-BMSCs via the CDR1as/miR-7/FGF2 pathway for TBI formation in vitro. Furthermore, in vivo application of the biphasic scaffold with magnetically seeded SPIO-BMSCs showed their regenerative potential, indicating that they could significantly accelerate and promote TBI healing with superior biomechanical properties after RCR in a rat rotator cuff tear model.

CONCLUSION

Magnetically seeding SPIO-BMSCs into a biphasic scaffold enhanced seeding efficacy to promote cell distribution and condensation. This construct enhanced the chondrogenesis process via the CDR1as/miR-7/FGF2 pathway and further promoted tendon-bone healing after RCR in a rat rotator cuff tear model.

CLINICAL RELEVANCE

This study provides an alternative strategy for improving TBI healing after RCR.

Magnetic Lipid-Based hybrid nanosystems: A combined stimuli- responsive nanocarriers for enriched chemotherapeutic potential of L-carnosine in induced breast Ehrlich ascites tumor model

Magnetic Lipid-Based Hybrid Nanosystems (M-LCNPs) is a novel nanoplatform that can respond to magnetic stimulus and are designed for delivering L-carnosine (CN), a challenging dipeptide employed in the treatment of breast cancer. CN exhibits considerable water solubility and undergoes in-vivo degradation, hence restricting its application. Consequently, it is anticipated that the developed M-LCNPs will enhance the effectiveness of CN. To ensure the physical stability of MNPs, they were initially coated with a mixture of oleic acid and oleylamine before being included in pegylated liquid crystalline nanoparticles (PLCNPs). The proposed M-LCNPs exhibited promising in-vitro characteristics, notably a small particle size (143.5 nm ± 1.25) and a high zeta potential (-39.5 mV ± 1.54), together with superparamagnetic behavior. The in-vitro release profile exhibited a prolonged release pattern. The IC50 values of M-LCNPs were 1.57 and 1.59 times lower than these of the CN solution after 24 and 48 hours, respectively. Female BALB/C female mice with an induced breast cancer (Ehrlich Ascites tumor [EAT] model) were used to study the influence of an external magnetic field on the chemotherapeutic activity and toxicity of CN loaded in the developed M-LCNPs. Stimuli-responsive M-LCNPs exhibited no apparent systemic toxicity in addition to enhanced chemotherapeutic efficacy compared to nontargeted M-LCNPs and CN solution, as evidenced by a reduction of % tumor growth (11.7%), VEGF levels (22.95 pg/g tissue), and cyclin D1 levels (27.61 ng/g tissue), and an increase in caspase-3 level (28.9 ng/g tissue). Ultimately, the developed stimuli-responsive CN loaded M-LCNPs presented a promising nanoplatform for breast cancer therapy.

Biocompatibility and proteomic profiling of DMSA-coated iron nanocubes in a human glioblastoma cell line

Background: Superparamagnetic iron core iron oxide shell nanocubes have previously shown superior performance in magnetic resonance imaging T2 contrast enhancement compared with spherical nanoparticles. Methods: Iron core iron oxide shell nanocubes were synthesized, stabilized with dimercaptosuccinic acid (DMSA-NC) and physicochemically characterized. MRI contrast enhancement and biocompatibility were assessed in vitro. Results: DMSA-NC showed a transverse relaxivity of 122.59 mM-1·s-1 Fe. Treatment with DMSA-NC did not induce cytotoxicity or oxidative stress in U-251 cells, and electron microscopy demonstrated DMSA-NC localization within endosomes and lysosomes in cells following internalization. Global proteomics revealed dysregulation of iron storage, transport, transcription and mRNA processing proteins. Conclusion: DMSA-NC is a promising T2 MRI contrast agent which, in this preliminary investigation, demonstrates favorable biocompatibility with an astrocyte cell model.

Recent trends in preparation and biomedical applications of iron oxide nanoparticles

The iron oxide nanoparticles (IONPs), possessing both magnetic behavior and semiconductor property, have been extensively used in multifunctional biomedical fields due to their biocompatible, biodegradable and low toxicity, such as anticancer, antibacterial, cell labelling activities. Nevertheless, there are few IONPs in clinical use at present. Some IONPs approved for clinical use have been withdrawn due to insufficient understanding of its biomedical applications. Therefore, a systematic summary of IONPs' preparation and biomedical applications is crucial for the next step of entering clinical practice from experimental stage. This review summarized the existing research in the past decade on the biological interaction of IONPs with animal/cells models, and their clinical applications in human. This review aims to provide cutting-edge knowledge involved with IONPs' biological effects in vivo and in vitro, and improve their smarter design and application in biomedical research and clinic trials.

DMSA-coated IONPs trigger oxidative stress, mitochondrial metabolic reprograming and changes in mitochondrial disposition, hindering cell cycle progression of cancer cells

There is increasing interest in modulating the redox homeostasis of tumors since high levels of reactive oxygen species (ROS) make them more vulnerable to changes in these species. Nanomedicine offers promise in this context as such applications may provoke biological responses that induce ROS production. Indeed, iron oxide nanoparticles (IONPs) can induce ROS accumulation through the so-called Fenton reaction of iron, further augmenting the ROS in tumors and overloading the antioxidant system beyond its capacity, thereby driving oxidative stress to a level that is incompatible with cell survival. Here, three different coatings for IONPs were compared to assess their intrinsic capacity to induce ROS production in cells. Of these coatings, dimercaptosuccinic acid-coated IONPs (DMSA-NPs) provoked the strongest ROS production, which was associated with the ability to reprogram the metabolism of cancer cells. This latter phenomenon involved shutting-down oxidative phosphorylation (OXPHOS), shifting mitochondrial morphology towards a more elongated phenotype, reducing the total mitochondrial mass and ultimately, blocking cell proliferation by inducing G0/G1 cell cycle arrest. Consequently, the data obtained highlights the importance of studying the chemical properties of IONPs, presenting DMSA-NPs as a novel tool to induce oxidative stress in cancer cells and alter their cell fate.

Large-scale production of superparamagnetic iron oxide nanoparticles by flame spray pyrolysis: In vitro biological evaluation for biomedical applications

Despite the large number of synthesis methodologies described for superparamagnetic iron oxide nanoparticles (SPIONs), the search for their large-scale production for their widespread use in biomedical applications remains a mayor challenge. Flame Spray Pyrolysis (FSP) could be the solution to solve this limitation, since it allows the fabrication of metal oxide nanoparticles with high production yield and low manufacture costs. However, to our knowledge, to date such fabrication method has not been upgraded for biomedical purposes. Herein, SPIONs have been fabricated by FSP and their surface has been treated to be subsequently coated with dimercaptosuccinic acid (DMSA) to enhance their colloidal stability in aqueous media. The final material presents high quality in terms of nanoparticle size, homogeneous size distribution, long-term colloidal stability and magnetic properties. A thorough in vitro validation has been performed with peripheral blood cells and mesenchymal stem cells (hBM-MSCs). Specifically, hemocompatibility studies show that these functionalized FSP-SPIONs-DMSA nanoparticles do not cause platelet aggregation or impair basal monocyte function. Moreover, in vitro biocompatibility assays show a dose-dependent cellular uptake while maintaining high cell viability values and cell cycle progression without causing cellular oxidative stress. Taken together, the results suggest that the FSP-SPIONs-DMSA optimized in this work could be a worthy alternative with the benefit of a large-scale production aimed at industrialization for biomedical applications.

Intracellular transformation and disposal mechanisms of magnetosomes in macrophages and cancer cells

Magnetosomes are magnetite nanoparticles biosynthesized by magnetotactic bacteria. Given their potential clinical applications for the diagnosis and treatment of cancer, it is essential to understand what becomes of them once they are within the body. With this aim, here we have followed the intracellular long-term fate of magnetosomes in two cell types: cancer cells (A549 cell line), because they are the actual target for the therapeutic activity of the magnetosomes, and macrophages (RAW 264.7 cell line), because of their role at capturing foreign agents. It is shown that cells dispose of magnetosomes using three mechanisms: splitting them into daughter cells, excreting them to the surrounding environment, and degrading them yielding less or non-magnetic iron products. A deeper insight into the degradation mechanisms by means of time-resolved X-ray absorption near-edge structure (XANES) spectroscopy has allowed us to follow the intracellular biotransformation of magnetosomes by identifying and quantifying the iron species occurring during the process. In both cell types there is a first oxidation of magnetite to maghemite and then, earlier in macrophages than in cancer cells, ferrihydrite starts to appear. Given that ferrihydrite is the iron mineral phase stored in the cores of ferritin proteins, this suggests that cells use the iron released from the degradation of magnetosomes to load ferritin. Comparison of both cellular types evidences that macrophages are more efficient at disposing of magnetosomes than cancer cells, attributed to their role in degrading external debris and in iron homeostasis.

3,4-Dihydroxiphenylacetic Acid-Based Universal Coating Technique for Magnetic Nanoparticles Stabilization for Biomedical Applications

Magnetic nanoparticles based on iron oxide attract researchers' attention due to a wide range of possible applications in biomedicine. As synthesized, most of the magnetic nanoparticles do not form the stable colloidal solutions that are required for the evaluation of their interactions with cells or their efficacy on animal models. For further application in biomedicine, magnetic nanoparticles must be further modified with biocompatible coating. Both the size and shape of magnetic nanoparticles and the chemical composition of the coating have an effect on magnetic nanoparticles' interactions with living objects. Thus, a universal method for magnetic nanoparticles' stabilization in water solutions is needed, regardless of how magnetic nanoparticles were initially synthesized. In this paper, we propose the versatile and highly reproducible ligand exchange technique of coating with 3,4-dihydroxiphenylacetic acid (DOPAC), based on the formation of Fe-O bonds with hydroxyl groups of DOPAC leading to the hydrophilization of the magnetic nanoparticles' surfaces following phase transfer from organic solutions to water. The proposed technique allows for obtaining stable water-colloidal solutions of magnetic nanoparticles with sizes from 21 to 307 nm synthesized by thermal decomposition or coprecipitation techniques. Those stabilized by DOPAC nanoparticles were shown to be efficient in the magnetomechanical actuation of DNA duplexes, drug delivery of doxorubicin to cancer cells, and targeted delivery by conjugation with antibodies. Moreover, the diversity of possible biomedical applications of the resulting nanoparticles was presented. This finding is important in terms of nanoparticle design for various biomedical applications and will reduce nanomedicines manufacturing time, along with difficulties related to comparative studies of magnetic nanoparticles with different magnetic core characteristics.

Photothermia at the nanoscale induces ferroptosis via nanoparticle degradation

The Fe(II)-induced ferroptotic cell death pathway is an asset in cancer therapy, yet it calls into question the biocompatibility of magnetic nanoparticles. In the latter, Fe(II) is sequestered within the crystal structure and is released only upon nanoparticle degradation, a transition that is not well understood. Here, we dissect the chemical environment necessary for nanoparticle degradation and subsequent Fe(II) release. Importantly, temperature acts as an accelerator of the process and can be triggered remotely by laser-mediated photothermal conversion, as evidenced by the loss of the nanoparticles' magnetic fingerprint. Remarkably, the local hot-spot temperature generated at the nanoscale can be measured in operando, in the vicinity of each nanoparticle, by comparing the photothermal-induced nanoparticle degradation patterns with those of global heating. Further, remote photothermal irradiation accelerates degradation inside cancer cells in a tumor spheroid model, with efficiency correlating with the endocytosis progression state of the nanoparticles. High-throughput imaging quantification of Fe2+ release, ROS generation, lipid peroxidation and cell death at the spheroid level confirm the synergistic thermo-ferroptotic therapy due to the photothermal degradation at the nanoparticle level.

A multifunctional adsorbent based on 2,3-dimercaptosuccinic acid/dopamine-modified magnetic iron oxide nanoparticles for the removal of heavy-metal ions

Overexploitation of nature by humans has led to an increasingly serious issue of heavy-metal water pollution. To reduce the threat of water pollution to humans and the environment, it is imperative to develop or improve the water treatment technology for heavy-metal-containing wastewater. Functionalized Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) have been widely used as effective adsorbents for the removal of heavy-metal ions from water owing to their high efficiency, low cost, selective adsorption ability, and recyclability. In this study, Fe₃O₄@DA-DMSA magnetic nanoparticles (FDDMs) were prepared by the functionalization of Fe₃O₄ MNPs with environmentally friendly dopamine (DA) and a heavy-metal detoxifying agent such as 2,3-dimercaptosuccinic acid (DMSA) for the efficient and rapid adsorption of Pb²⁺, Cu²⁺, and Cd²⁺, with maximum adsorption capacities of 187.62, 63.01, and 49.46 mg/g, respectively. FDDMs exhibited the best ability to remove Pb²⁺ with a maximum adsorption capacity than that of the most reported Fe₃O₄ MNP-related adsorbents. In actual wastewater and multi-component simulated water samples contaminated with Pb²⁺, Cu²⁺, and Cd²⁺, the as-prepared adsorbent maintained a good removal ability for Pb²⁺ with low influence by ionic strength and interfering ions, as well as exhibited an excellent selectivity. According to the results of batch experiments and X-ray photoelectron spectroscopy (XPS) analysis of the adsorbent before and after adsorption, the adsorption mechanism of the adsorbent for the removal of heavy-metal ions mainly involves coordination and ion exchange. In addition, the adsorbent exhibited a good regeneration performance. Therefore, FDDMs can be considered as a promising adsorbent for the treatment of heavy-metal wastewater.

CD40-targeting magnetic nanoparticles for MRI/optical dual-modality molecular imaging of vulnerable atherosclerotic plaques

BACKGROUND AND AIMS

Acute coronary syndrome caused by vulnerable plaque rupture or erosion is a leading cause of death worldwide. CD40 has been reported to be highly expressed in atherosclerotic plaques and closely related to plaque stability. Therefore, CD40 is expected to be a potential target for the molecular imaging of vulnerable plaques in atherosclerosis. We aimed to design a CD40-targeted magnetic resonance imaging (MRI)/optical multimodal molecular imaging probe and explore its ability to detect and target vulnerable atherosclerotic plaques.

METHODS

CD40-Cy5.5 superparamagnetic iron oxide nanoparticles (CD40-Cy5.5-SPIONs), which comprise a CD40-targeting multimodal imaging contrast agent, were constructed by conjugating CD40 antibody and Cy5.5-N-hydroxysuccinimide ester with SPIONs. During this in vitro study, we observed the binding ability of CD40-Cy5.5-SPIONs with RAW 264.7 cells and mouse aortic vascular smooth muscle cells (MOVAS) after different treatments, using confocal fluorescence microscopy and Prussian blue staining. An in vivo study involving ApoE^-/- mice fed a high-fat diet for 24-28 weeks was performed. 24 h after intravenous injection of CD40-Cy5.5-SPIONs, fluorescence imaging and MRI were performed.

RESULTS

CD40-Cy5.5-SPIONs bind specifically to tumor necrosis factor (TNF)-α-treated macrophages and smooth muscle cells. Fluorescence imaging results showed that, compared with the control group and the atherosclerosis group injected with non-specific bovine serum albumin (BSA)-Cy5.5-SPIONs, the atherosclerotic group injected with CD40-Cy5.5-SPIONs had a stronger fluorescence signal. T2-weighted images showed that the carotid arteries of atherosclerotic mice injected with CD40-Cy5.5-SPIONs had a significant substantial T2 contrast enhancement effect.

CONCLUSIONS

CD40-Cy5.5-SPIONs could potentially serve as an effective MRI/optical probe for vulnerable atherosclerotic plaques during non-invasive detection.

Different coatings on magnetic nanoparticles dictate their degradation kinetics in vivo for 15 months after intravenous administration in mice

BACKGROUND

The surface coating of iron oxide magnetic nanoparticle (MNPs) drives their intracellular trafficking and degradation in endolysosomes, as well as dictating other cellular outcomes. As such, we assessed whether MNP coatings might influence their biodistribution, their accumulation in certain organs and their turnover therein, processes that must be understood in vivo to optimize the design of nanoformulations for specific therapeutic/diagnostic needs.

RESULTS

In this study, three different MNP coatings were analyzed, each conferring the identical 12 nm iron oxide cores with different physicochemical characteristics: 3-aminopropyl-triethoxysilane (APS), dextran (DEX), and dimercaptosuccinic acid (DMSA). When the biodistribution of these MNPs was analyzed in C57BL/6 mice, they all mainly accumulated in the spleen and liver one week after administration. The coating influenced the proportion of the MNPs in each organ, with more APS-MNPs accumulating in the spleen and more DMSA-MNPs accumulating in the liver, remaining there until they were fully degraded. The changes in the physicochemical properties of the MNPs (core size and magnetic properties) was also assessed during their intracellular degradation when internalized by two murine macrophage cell lines. The decrease in the size of the MNPs iron core was influenced by their coating and the organ in which they accumulated. Finally, MNP degradation was analyzed in the liver and spleen of C57BL/6 mice from 7 days to 15 months after the last intravenous MNP administration.

CONCLUSIONS

The MNPs degraded at different rates depending on the organ and their coating, the former representing the feature that was fundamental in determining the time they persisted. In the liver, the rate of degradation was similar for all three coatings, and it was faster than in the spleen. This information regarding the influence of coatings on the in vivo degradation of MNPs will help to choose the best coating for each biomedical application depending on the specific clinical requirements.

Influence of Polymer Shell Molecular Weight on Functionalized Iron Oxide Nanoparticles Morphology and In Vivo Biodistribution

Iron oxide nanoparticles (IONPs) have been extensively used in different biomedical applications due to their biocompatibility and magnetic properties. However, different functionalization approaches have been developed to improve their time-life in the systemic circulation. Here, we have synthesized IONPs using a modified Massart method and functionalized them in situ with polyethylene glycol with different molecular weights (20 K and 35 K). The resulting nanoparticles were characterized in terms of morphology, structure, and composition using transmission electron microscopy (TEM) and selected area electron diffraction (SAED). In vivo biodistribution was evaluated in Balb/c mice, the presence of IONP being evidenced through histopathological investigations. IONP morphological characterization showed a change in shape (from spherical to rhombic) and size with molecular weight, while structural characterization proved the obtaining of highly crystalline samples of spinel structured cubic face-centered magnetite. In vivo biodistribution in a mice model proved the biocompatibility of all of the IONP samples. All NPs were cleared through the liver, spleen, and lungs, while bare IONPs were also evidenced in kidneys.

de la Fuente J, Fratila RM, Grazú V, Gutiérrez L. Iron Speciation in Animal Tissues Using AC Magnetic Susceptibility Measurements: Quantification of Magnetic Nanoparticles, Ferritin, and Other Iron-Containing Species

The simultaneous detection and quantification of several iron-containing species in biological matrices is a challenging issue. Especially in the frame of studies using magnetic nanoparticles for biomedical applications, no gold-standard technique has been described yet and combinations of different techniques are generally used. In this work, AC magnetic susceptibility measurements are used to analyze different organs from an animal model that received a single intratumor administration of magnetic nanoparticles. The protocol used for the quantification of iron associated with the magnetic nanoparticles is carefully described, including the description of the preparation of several calibration standard samples of nanoparticle suspensions with different degrees of dipolar interactions. The details for the quantitative analysis of other endogenous iron-containing species such as ferritin or hemoglobin are also described. Among the advantages of this technique are that tissue sample preparation is minimal and that large amounts of tissue can be characterized each time (up to hundreds of milligrams). In addition, the very high specificity of the magnetic measurements allows for tracking of the nanoparticle transformations. Furthermore, the high sensitivity of the instrumentation results in very low limits of detection for some of the iron-containing species. Therefore, the presented technique is an extremely valuable tool to track iron oxide magnetic nanoparticles in samples of biological origin.

Synthesis and characterization of CoxFe1-xFe2O4 nanoparticles by anionic, cationic, and non-ionic surfactant templates via co-precipitation

The cobalt ferrite nanoparticles (Co_xFe_1-xFe₂O₄) were synthesized by the surfactant templated co-precipitation method using various surfactants namely sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (CTAB), and Tween20. Under the substitution, the Co_xFe_1-xFe₂O₄ particles were synthesized at various Co²⁺ and Fe²⁺ mole ratios (x = 1, 0.6, 0.2, and 0) with the SDS. The cobalt ferrite nanoparticles were characterized for their morphology, structure, magnetic, and electrical properties. All Co_xFe_1-xFe₂O₄ nanoparticles showed the nanoparticle sizes varying from 16 to 43 nm. In the synthesis of CoFe₂O₄, the SDS template provided the smallest particle size, whereas the saturated magnetization (M_s) of CoFe₂O₄ was reduced by using CTAB, SDS, and Tween20. For the Co_xFe_1-xFe₂O₄ as synthesized by the SDS template at 1.2 CMC, the M_s increased with increasing Fe²⁺ mole ratio. The highest M_s of 100.4 emu/g was obtained from the Fe₃O₄ using the SDS template. The Fe₃O₄ nanoparticle is potential to be used in various actuator and biomedical devices.

Long-Term Clearance and Biodistribution of Magnetic Nanoparticles Assessed by AC Biosusceptometry

Once administered in an organism, the physiological parameters of magnetic nanoparticles (MNPs) must be addressed, as well as their possible interactions and retention and elimination profiles. Alternating current biosusceptometry (ACB) is a biomagnetic detection system used to detect and quantify MNPs. The aims of this study were to evaluate the biodistribution and clearance of MNPs profiles through long-time in vivo analysis and determine the elimination time carried out by the association between the ACB system and MnFe₂O₄ nanoparticles. The liver, lung, spleen, kidneys, and heart and a blood sample were collected for biodistribution analysis and, for elimination analysis, and over 60 days. During the period analyzed, the animal’s feces were also collectedd. It was possible to notice a higher uptake by the liver and the spleen due to their characteristics of retention and uptake. In 60 days, we observed an absence of MNPs in the spleen and a significant decay in the liver. We also determined the MNPs’ half-life through the liver and the spleen elimination. The data indicated a concentration decay profile over the 60 days, which suggests that, in addition to elimination via feces, there is an endogenous mechanism of metabolization or possible agglomeration of MNPs, resulting in loss of ACB signal intensity.

Recent development for biomedical applications of magnetic nanoparticles

In recent decades, the use of engineered nanoparticles has been increasing in various sectors, including biomedicine, diagnosis, water treatment, and environmental remediation leading to significant public concerns. Among these nanoparticles, magnetic nanoparticles (MNPs) have gained many attentions in medicine, pharmacology, drug delivery system, molecular imaging, and bio-sensing due to their various properties. In addition, various studies have reviewed MNPs main applications in the biomedical engineering area with intense progress and recent achievements. Nanoparticles, especially the magnetic nanoparticles, have recently been confirmed with excellent antiviral activity against different viruses, including SARS-CoV-2(Covid-19) and their recent development against Covid-19 also has also been discussed. This review aims to highlight the recent development of the magnetic nanoparticles and their biomedical applications such as diagnosis of diseases, molecular imaging, hyperthermia, bio-sensing, gene therapy, drug delivery and the diagnosis of Covid-19.

Safety Evaluation of Nanotechnology Products

Nanomaterials are now being used in a wide variety of biomedical applications. Medical and health-related issues, however, have raised major concerns, in view of the potential risks of these materials against tissue, cells, and/or organs and these are still poorly understood. These particles are able to interact with the body in countless ways, and they can cause unexpected and hazardous toxicities, especially at cellular levels. Therefore, undertaking in vitro and in vivo experiments is vital to establish their toxicity with natural tissues. In this review, we discuss the underlying mechanisms of nanotoxicity and provide an overview on in vitro characterizations and cytotoxicity assays, as well as in vivo studies that emphasize blood circulation and the in vivo fate of nanomaterials. Our focus is on understanding the role that the physicochemical properties of nanomaterials play in determining their toxicity.

Understanding MNPs Behaviour in Response to AMF in Biological Milieus and the Effects at the Cellular Level: Implications for a Rational Design That Drives Magnetic Hyperthermia Therapy toward Clinical Implementation

Simple Summary

Magnetic hyperthermia therapy is an alternative treatment for cancer that complements traditional therapies and that has shown great promise in recent years. In this review, we assess the current applications of this therapy in order to understand why its translation from the laboratory to the clinic has been less smooth than was anticipated, identifying the possible bottlenecks and proposing solutions to the problems encountered.

Abstract

Hyperthermia has emerged as a promising alternative to conventional cancer therapies and in fact, traditional hyperthermia is now commonly used in combination with chemotherapy or surgery during cancer treatment. Nevertheless, non-specific application of hyperthermia generates various undesirable side-effects, such that nano-magnetic hyperthermia has arisen a possible solution to this problem. This technique to induce hyperthermia is based on the intrinsic capacity of magnetic nanoparticles to accumulate in a given target area and to respond to alternating magnetic fields (AMFs) by releasing heat, based on different principles of physics. Unfortunately, the clinical implementation of nano-magnetic hyperthermia has not been fluid and few clinical trials have been carried out. In this review, we want to demonstrate the need for more systematic and basic research in this area, as many of the sub-cellular and molecular mechanisms associated with this approach remain unclear. As such, we shall consider here the biological effects that occur and why this theoretically well-designed nano-system fails in physiological conditions. Moreover, we will offer some guidelines that may help establish successful strategies through the rational design of magnetic nanoparticles for magnetic hyperthermia.

Long-Term Fate of Magnetic Particles in Mice: A Comprehensive Study

Safe application of nanoparticles in medicine requires full understanding of their pharmacokinetics including catabolism in the organism. However, information about nanoparticle degradation is still scanty due to difficulty of long-term measurements by invasive techniques. Here, we describe a magnetic spectral approach for in vivo monitoring of magnetic particle (MP) degradation. The method noninvasiveness has allowed performing of a broad comprehensive study of the 1-year fate of 17 types of iron oxide particles. We show a long-lasting influence of five parameters on the MP degradation half-life: dose, hydrodynamic size, ζ-potential, surface coating, and internal architecture. We observed a slowdown in MP biotransformation with an increase of the injected dose and faster degradation of the particles of a small hydrodynamic size. A comparison of six types of 100 nm particles coated by different hydrophilic polymer shells has shown that the slowest (t_1/2 = 38 ± 6 days) and the fastest (t_1/2 = 15 ± 4 days) degradations were achieved with a polyethylene glycol and polyglucuronic acid coatings, respectively. The most significant influence on the MP degradation was due to the internal architecture of the particles as the coverage of magnetic cores with a solid 39 nm polystyrene layer slowed down the half-life of the core-shell MPs from 48 days to more than 1 year. The revealed deeper insights into the particle degradation in vivo may facilitate rational design of nano- and microparticles with predictable long-term fate in vivo.

Mild Magnetic Hyperthermia-Activated Innate Immunity for Liver Cancer Therapy

Magnetic hyperthermia therapy (MHT) is noninvasive and features excellent tissue penetration for deep-seated tumors, but unfortunately, it suffers the low therapeutic efficacy due to the limited magneto-thermal efficiency and insufficient intratumor accumulation of conventional intravenous-injected magnetic nanoparticles, which are actually mostly sequestered by the mononuclear phagocyte system, especially the liver. Such a disadvantageous characteristic of preferential liver uptake is here exploited, for the first time as far as we know, to treat orthotopic liver cancer by mild MHT using specially designed composite magnetic nanoparticles. A kind of core-shell-structured and Zn²⁺-doped Zn-CoFe₂O₄@Zn-MnFe₂O₄ superparamagnetic nanoparticles (ZCMF) has been synthesized which exhibits excellent and highly controllable magnetic hyperthermia performance owing to an exchange-coupled magnetism between the core and shell, and Zn²⁺ doping. The controllable mild MHT at 43-44 °C based on ZCMF demonstrates almost complete inhibition of liver cancer cell proliferation and tumor growth, which is associated with the suppression of heat shock protein 70 (HSP70) expression. More importantly, the mild MHT-treated liver cancer cells are capable of activating natural killer (NK) cells by dramatically upregulating the expression of UL16-binding proteins (ULBPs), ligands of natural killer group 2 member D (NKG2D). As a result, the growth of both xenograft tumors and orthotopic liver tumors were almost completely suppressed under mild MHT via induced NK-cell-related antitumor immunity in vivo. This work not only evidences the great potential of mild MHT but also reveals the underlying immunity activation mechanism in liver cancer treatment by mild MHT.

Critical Parameters to Improve Pancreatic Cancer Treatment Using Magnetic Hyperthermia: Field Conditions, Immune Response, and Particle Biodistribution

Magnetic hyperthermia (MH) was used to treat a murine model of pancreatic cancer. This type of cancer is generally characterized by the presence of dense stroma that acts as a barrier for chemotherapeutic treatments. Several alternating magnetic field (AMF) conditions were evaluated using three-dimensional (3D) cell culture models loaded with magnetic nanoparticles (MNPs) to determine which conditions were producing a strong effect on the cell viability. Once the optimal AMF conditions were selected, in vivo experiments were carried out using similar frequency and field amplitude parameters. A marker of the immune response activation, calreticulin (CALR), was evaluated in cells from a xenograft tumor model after the MH treatment. Moreover, the distribution of nanoparticles within the tumor tissue was assessed by histological analysis of tumor sections, observing that the exposure to the alternating magnetic field resulted in the migration of particles toward the inner parts of the tumor. Finally, a relationship between an inadequate body biodistribution of the particles after their intratumoral injection and a significant decrease in the effectiveness of the MH treatment was found. Animals in which most of the particles remained in the tumor area after injection showed higher reductions in the tumor volume growth in comparison with those animals in which part of the particles were found also in the liver and spleen. Therefore, our results point out several factors that should be considered to improve the treatment effectiveness of pancreatic cancer by magnetic hyperthermia.

Accelerated anaerobic biodecolorization of sulfonated azo dyes by magnetite nanoparticles as potential electron transfer mediators

Anaerobic decolorization of azo dyes has been evidenced to be an economical and effective pretreatment method, but its generally limited by the low decolorization efficiency, especially for biodecolorization sulfonated azo dyes. In this study, magnetite nanoparticles (MNPs) as a conductive material, was coupled into anaerobic system for enhancing decolorization of sulfonated azo dyes, i.e., methyl orange (MO), with technology feasibility and system stability emphasized. The results showed that the anaerobic decolorization capacity was significantly enhanced with addition of MNPs (at dose of 1 g/L), where the efficiencies of MO decolorization and aromatic amines formation were as high as 97.28 ± 0.78 % and 99.44 ± 0.25%, respectively. In addition, both electron transport system activity and sludge conductivity were also significantly improved, suggesting that a direct extracellular electron transfer had been successfully established via MNPs as RMs. Under continuous-flow experiments, addition of MNPs not only improved anaerobic system resistance environmental stress (e.g., high MO concentration, low hydraulic retention time and low co-substance concentration) but also accelerated sludge granulation. The relative abundance of functional species related to dissimilatory iron reduction and MO biodegradation were also enriched under MNPs stimulation. The observed long-term stable performance suggests the full-scale application potential of this coupled system for treatment of wastewater containing sulfonated azo dyes.

Disruption of Cell Adhesion and Cytoskeletal Networks by Thiol-Functionalized Silica-Coated Iron Oxide Nanoparticles

One of the major obstacles that limits the use of magnetic nanoparticles in biomedical applications is their potential toxicity. In the present study, we evaluated the cytotoxic effects of thiol-functionalized silica-coated iron oxide (Fe₃O₄@SiO₂-SH) nanoparticles using human lung epithelial cells A549. We investigated the effect of Fe₃O₄@SiO₂-SH nanoparticles on the cell viability, proliferation, cell cycle distribution, adhesion, apoptosis, and the orientation of the cytoskeletal networks, as well as on expression of proteins involved in cell death, cell survival, and cell adhesion. We demonstrated that exposure of A549 cells to Fe₃O₄@SiO₂-SH nanoparticles resulted in severe disruption of the actin microfilaments and microtubule cytoskeleton and reduced the size of focal adhesions. Furthermore, cell adhesion was significantly affected as well as the phosphorylation of focal adhesion kinase (FAK), extracellular-signal-regulated kinase (ERK), and p38. Our findings highlight the need for in-depth cytotoxic evaluation of nanoparticles supporting their safer use, especially in biomedical applications.

Scaffold-free biofabrication of adipocyte structures with magnetic levitation

Tissue engineering research aims to repair the form and/or function of impaired tissues. Tissue engineering studies mostly rely on scaffold-based techniques. However, these techniques have certain challenges, such as the selection of proper scaffold material, including mechanical properties, sterilization, and fabrication processes. As an alternative, we propose a novel scaffold-free adipose tissue biofabrication technique based on magnetic levitation. In this study, a label-free magnetic levitation technique was used to form three-dimensional (3D) scaffold-free adipocyte structures with various fabrication strategies in a microcapillary-based setup. Adipogenic-differentiated 7F2 cells and growth D1 ORL UVA stem cells were used as model cells. The morphological properties of the 3D structures of single and cocultured cells were analyzed. The developed procedure leads to the formation of different patterns of single and cocultured adipocytes without a scaffold. Our results indicated that adipocytes formed loose structures while growth cells were tightly packed during 3D culture in the magnetic levitation platform. This system has potential for ex vivo modeling of adipose tissue for drug testing and transplantation applications for cell therapy in soft tissue damage. Also, it will be possible to extend this technique to other cell and tissue types.

Ever-Evolving Identity of Magnetic Nanoparticles within Human Cells: The Interplay of Endosomal Confinement, Degradation, Storage, and Neocrystallization

Considerable knowledge has been acquired in inorganic nanoparticles' synthesis and nanoparticles' potential use in biomedical applications. Among different materials, iron oxide nanoparticles remain unrivaled for several reasons. Not only do they respond to multiple physical stimuli (e.g., magnetism, light) and exert multifunctional therapeutic and diagnostic actions but also they are biocompatible and integrate endogenous iron-related metabolic pathways. With the aim to optimize the use of (magnetic) iron oxide nanoparticles in biomedicine, different biophysical phenomena have been recently identified and studied. Among them, the concept of a "nanoparticle's identity" is of particular importance. Nanoparticles' identities evolve in distinct biological environments and over different periods of time. In this Account, we focus on the remodeling of magnetic nanoparticles' identities following their journey inside cells. For instance, nanoparticles' functions, such as heat generation or magnetic resonance imaging, can be highly impacted by endosomal confinement. Structural degradation of nanoparticles was also evidenced and quantified in cellulo and correlates with the loss of magnetic nanoparticle properties. Remarkably, in human stem cells, the nonmagnetic products of nanoparticles' degradation could be subsequently reassembled into neosynthesized, endogenous magnetic nanoparticles. This stunning occurrence might account for the natural presence of magnetic particles in human organs, especially the brain. However, mechanistic details and the implication of such phenomena in homeostasis and disease have yet to be completely unraveled.This Account aims to assess the short- and long-term transformations of magnetic iron oxide nanoparticles in living cells, particularly focusing on human stem cells. Precisely, we herein overview the multiple and ever-evolving chemical, physical, and biological magnetic nanoparticles' identities and emphasize the remarkable intracellular fate of these nanoparticles.

Potential Toxicity of Iron Oxide Magnetic Nanoparticles: A Review

The noteworthy intensification in the development of nanotechnology has led to the development of various types of nanoparticles. The diverse applications of these nanoparticles make them desirable candidate for areas such as drug delivery, coasmetics, medicine, electronics, and contrast agents for magnetic resonance imaging (MRI) and so on. Iron oxide magnetic nanoparticles are a branch of nanoparticles which is specifically being considered as a contrast agent for MRI as well as targeted drug delivery vehicles, angiogenic therapy and chemotherapy as small size gives them advantage to travel intravascular or intracavity actively for drug delivery. Besides the mentioned advantages, the toxicity of the iron oxide magnetic nanoparticles is still less explored. For in vivo applications magnetic nanoparticles should be nontoxic and compatible with the body fluids. These particles tend to degrade in the body hence there is a need to understand the toxicity of the particles as whole and degraded products interacting within the body. Some nanoparticles have demonstrated toxic effects such inflammation, ulceration, and decreases in growth rate, decline in viability and triggering of neurobehavioral alterations in plants and cell lines as well as in animal models. The cause of nanoparticles' toxicity is attributed to their specific characteristics of great surface to volume ratio, chemical composition, size, and dosage, retention in body, immunogenicity, organ specific toxicity, breakdown and elimination from the body. In the current review paper, we aim to sum up the current knowledge on the toxic effects of different magnetic nanoparticles on cell lines, marine organisms and rodents. We believe that the comprehensive data can provide significant study parameters and recent developments in the field. Thereafter, collecting profound knowledge on the background of the subject matter, will contribute to drive research in this field in a new sustainable direction.

Magnetically Actuated Manipulation and Its Applications for Cartilage Defects: Characteristics and Advanced Therapeutic Strategies

For the fact that articular cartilage is a highly organized and avascular tissue, cartilage defects are limited to spontaneously heal, which would subsequently progress to osteoarthritis. Many methods have been developed to enhance the ability for cartilage regeneration, among which magnetically actuated manipulation has attracted interests due to its biocompatibility and non-invasive manipulation. Magnetically actuated manipulation that can be achieved by introducing magnetic nanoparticles and magnetic field. This review summarizes the cutting-edge research on the chondrogenic enhancements via magnetically actuated manipulation, including cell labeling, cell targeting, cell assembly, magnetic seeding and tissue engineering strategies.

The Intrinsic Biological Identities of Iron Oxide Nanoparticles and Their Coatings: Unexplored Territory for Combinatorial Therapies

Over the last 20 years, iron oxide nanoparticles (IONPs) have been the subject of increasing investigation due to their potential use as theranostic agents. Their unique physical properties (physical identity), ample possibilities for surface modifications (synthetic identity), and the complex dynamics of their interaction with biological systems (biological identity) make IONPs a unique and fruitful resource for developing magnetic field-based therapeutic and diagnostic approaches to the treatment of diseases such as cancer. Like all nanomaterials, IONPs also interact with different cell types in vivo, a characteristic that ultimately determines their activity over the short and long term. Cells of the mononuclear phagocytic system (macrophages), dendritic cells (DCs), and endothelial cells (ECs) are engaged in the bulk of IONP encounters in the organism, and also determine IONP biodistribution. Therefore, the biological effects that IONPs trigger in these cells (biological identity) are of utmost importance to better understand and refine the efficacy of IONP-based theranostics. In the present review, which is focused on anti-cancer therapy, we discuss recent findings on the biological identities of IONPs, particularly as concerns their interactions with myeloid, endothelial, and tumor cells. Furthermore, we thoroughly discuss current understandings of the basic molecular mechanisms and complex interactions that govern IONP biological identity, and how these traits could be used as a stepping stone for future research.

Sperm Cell Driven Microrobots-Emerging Opportunities and Challenges for Biologically Inspired Robotic Design

With the advent of small-scale robotics, several exciting new applications like Targeted Drug Delivery, single cell manipulation and so forth, are being discussed. However, some challenges remain to be overcome before any such technology becomes medically usable; among which propulsion and biocompatibility are the main challenges. Propulsion at micro-scale where the Reynolds number is very low is difficult. To overcome this, nature has developed flagella which have evolved over millions of years to work as a micromotor. Among the microscopic cells that exhibit this mode of propulsion, sperm cells are considered to be fast paced. Here, we give a brief review of the state-of-the-art of Spermbots - a new class of microrobots created by coupling sperm cells to mechanical loads. Spermbots utilize the flagellar movement of the sperm cells for propulsion and as such do not require any toxic fuel in their environment. They are also naturally biocompatible and show considerable speed of motion thereby giving us an option to overcome the two challenges of propulsion and biocompatibility. The coupling mechanisms of physical load to the sperm cells are discussed along with the advantages and challenges associated with the spermbot. A few most promising applications of spermbots are also discussed in detail. A brief discussion of the future outlook of this extremely promising category of microrobots is given at the end.

Chemotherapeutic potential of L-carnosine from stimuli-responsive magnetic nanoparticles against breast cancer model

Aim: L-carnosine-coated magnetic nanoparticles (CCMNPs) were developed to enhance chemotherapeutic activity of carnosine-dipeptide. Materials & methods: Surface grafting of MNPs with carnosine was contended by differential scanning calorimetry, infrared spectroscopy and x-ray diffraction. Physicochemical characterization and in vitro cytotoxicity on MCF-7 cell line was carried out. In vivo chemotherapeutic activity and toxicity was assessed by an Ehrlich Ascites tumor model. Results: CCMNPs possessed monodispersed size (120 nm), ζ (-27.3 mV), magnetization (51.52 emu/g) and entrapment efficiency (88.3%) with sustained release rate. CCMNPs showed 2.3-folds lower IC50 values compared with carnosine solution after 48 h. Targeted CCMNPs were specifically accumulated in tumor showing significant reduction in tumor size with no systemic toxicity. Significant reduction in VEGF and cyclin D1 levels were observed. Conclusion: The developed system endowed with responsiveness to an external stimulus can represent a promising magnetically targeted delivery system for carnosine site specific delivery.

Transformation Cycle of Magnetosomes in Human Stem Cells: From Degradation to Biosynthesis of Magnetic Nanoparticles Anew

The nanoparticles produced by magnetotactic bacteria, called magnetosomes, are made of a magnetite core with high levels of crystallinity surrounded by a lipid bilayer. This organized structure has been developed during the course of evolution of these organisms to adapt to their specific habitat and is assumed to resist degradation and to be able to withstand the demanding biological environment. Herein, we investigated magnetosomes' structural fate upon internalization in human stem cells using magnetic and photothermal measurements, electron microscopy, and X-ray absorption spectroscopy. All measurements first converge to the demonstration that intracellular magnetosomes can experience an important biodegradation, with up to 70% of their initial content degraded, which is associated with the progressive storage of the released iron in the ferritin protein. It correlates with an extensive magnetite to ferrihydrite phase transition. The ionic species delivered by this degradation could then be used by the cells to biosynthesize magnetic nanoparticles anew. In this case, cell magnetism first decreased with magnetosomes being dissolved, but then cells remagnetized entirely, evidencing the neo-synthesis of biogenic magnetic nanoparticles. Bacteria-made biogenic magnetosomes can thus be totally remodeled by human stem cells, into human cells-made magnetic nanoparticles.

Improved magnetic lateral flow assays with optimized nanotags for point-of-use inductive biosensing

Magnetic nanotags in lateral flow immunoassay for inductive biosensing: clusters of superparamagnetic critical size optimize the reading out.

Recent Advances in Magnetite Nanoparticle Functionalization for Nanomedicine

Functionalization of nanomaterials can enhance and modulate their properties and behaviour, enabling characteristics suitable for medical applications. Magnetite (Fe3O4) nanoparticles are one of the most popular types of nanomaterials used in this field, and many technologies being already translated in clinical practice. This article makes a summary of the surface modification and functionalization approaches presented lately in the scientific literature for improving or modulating magnetite nanoparticles for their applications in nanomedicine.

Flower-like Mn-Doped Magnetic Nanoparticles Functionalized with αvβ3-Integrin-Ligand to Efficiently Induce Intracellular Heat after Alternating Magnetic Field Exposition, Triggering Glioma Cell Death

Despite the potential of magnetic nanoparticles (NPs) to mediate intracellular hyperthermia when exposed to an alternating magnetic field (AMF), several studies indicate that the intracellular heating capacity of magnetic NPs depends on factors such as cytoplasm viscosity, nanoparticle aggregation within subcellular compartments, and dipolar interactions. In this work, we report the design and synthesis of monodispersed flowerlike superparamagnetic manganese iron oxide NPs with maximized SAR (specific absorption rate) and evaluate their efficacy as intracellular heaters in the human tumor-derived glioblastoma cell line U87MG. Three main strategies to tune the particle anisotropy of the core and the surface to reach the maximum heating efficiency were adopted: (1) varying the crystalline anisotropy by inserting a low amount of Mn²⁺ in the inverse spinel structure, (2) varying the NP shape to add an additional anisotropy source while keeping the superparamagnetic behavior, and (3) maximizing NP-cell affinity through conjugation with a biological targeting molecule to reach the NP concentration required to increase the temperature within the cell. We investigate possible effects produced by these improved NPs under the AMF (f = 96 kHz, H = 47 kA/m) exposure in the glioblastoma cell line U87MG by monitoring the expression of hsp70 gene and reactive oxygen species (ROS) production, as both effects have been described to be induced by increasing the intracellular temperature. The induced cell responses include cellular membrane permeabilization and rupture with concomitant high ROS appearance and hsp70 expression, followed by cell death. The responses were largely limited to cells that contained the NPs exposed to the AMF. Our results indicate that the developed strategies to optimize particle anisotropy in this work are a promising guidance to improve the heating efficiency of magnetic NPs in the human glioma cell line.

Nanoparticles for Bioapplications: Study of the Cytotoxicity of Water Dispersible CdSe(S) and CdSe(S)/ZnO Quantum Dots

Semiconductor nanocrystals or quantum dots (QDs) have unique optical and physical properties that make them potential imaging tools in biological and medical applications. However, concerns over the aqueous dispersivity, toxicity to cells, and stability in biological environments may limit the use of QDs in such applications. Here, we report an investigation into the cytotoxicity of aqueously dispersed CdSe(S) and CdSe(S)/ZnO core/shell QDs in the presence of human colorectal carcinoma cells (HCT-116) and a human skin fibroblast cell line (WS1). The cytotoxicity of the precursor solutions used in the synthesis of the CdSe(S) QDs was also determined in the presence of HCT-116 cells. CdSe(S) QDs were found to have a low toxicity at concentrations up to 100 µg/mL, with a decreased cell viability at higher concentrations, indicating a highly dose-dependent response. Meanwhile, CdSe(S)/ZnO core/shell QDs exhibited lower toxicity than uncoated QDs at higher concentrations. Confocal microscopy images of HCT-116 cells after incubation with CdSe(S) and CdSe(S)/ZnO QDs showed that the cells were stable in aqueous concentrations of 100 µg of QDs per mL, with no sign of cell necrosis, confirming the cytotoxicity data.

Single cell magnetometry by magnetophoresis vs. bulk cell suspension magnetometry by SQUID-MPMS - a comparison

Paramagnetic constituents of a cell have strong effect on cell's volume magnetic susceptibility even at low volume fraction because of their high susceptibility relative to that of the diamagnetic cell constituents. The effect can be measured at a single cell level by measuring cell terminal velocity in viscous media using a microscope equipped with a well-defined field and gradient magnet configuration (referred to as magnetophoretic analysis by cell tracking velocimetry, CTV). The sensitivity of such a microscopic-scale magnetometry was compared to that of a reference method of superconducting quantum interference-magnetic properties measurement system (SQUID-MPMS) using a red blood cell (RBC) suspension model. The RBC hemoglobin oxygen saturation determines the hemoglobin molecular magnetic susceptibility (diamagnetic when fully oxygenated, paramagnetic when fully deoxygenated or converted to methemoglobin). The SQUID-MPMS measurements were performed on an average of 5,000 RBCs in 20 μL physiological phosphate buffer at room temperature, those by CTV on a single cell track in a mean magnetic field of 1.6 T and mean gradient of 240 T/m, repeated for an average of 1,000 tracks per sample. This suggests 5,000× higher sensitivity of cell susceptometry by magnetophoretic analysis than by SQUID-MPMS. The magnetophoretic mean RBC magnetic susceptibilities were in the range determined by SQUID-MPMS (lower limit) and theory (upper limit). The ability of magnetophoretic analysis to resolve susceptibility peaks in a mixed cell populations was confirmed for an oxy RBC and met RBC mixture. Magnetophoretic analysis by CTV provides new tool for studies of emergence of paramagnetic reaction products in the cell.

Biosynthesis of magnetic nanoparticles from nano-degradation products revealed in human stem cells

While magnetic nanoparticles offer exciting possibilities for stem cell imaging or tissue bioengineering, their long-term intracellular fate remains to be fully documented. Besides, it appears that magnetic nanoparticles can occur naturally in human cells, but their origin and potentially endogenous synthesis still need further understanding. In an effort to explore the life cycle of magnetic nanoparticles, we investigated their transformations upon internalization in mesenchymal stem cells and as a function of the cells' differentiation status (undifferentiated, or undergoing adipogenesis, osteogenesis, and chondrogenesis). Using magnetism as a fingerprint of the transformation process, we evidenced an important degradation of the nanoparticles during chondrogenesis. For the other pathways, stem cells were remarkably "remagnetized" after degradation of nanoparticles. This remagnetization phenomenon is the direct demonstration of a possible neosynthesis of magnetic nanoparticles in cellulo and could lay some foundation to understand the presence of magnetic crystals in human cells. The neosynthesis was shown to take place within the endosomes and to involve the H-subunit of ferritin. Moreover, it appeared to be the key process to avoid long-term cytotoxicity (impact on differentiation) related to high doses of magnetic nanoparticles within stem cells.

Cell-Promoted Nanoparticle Aggregation Decreases Nanoparticle-Induced Hyperthermia under an Alternating Magnetic Field Independently of Nanoparticle Coating, Core Size, and Subcellular Localization

Magnetic hyperthermia has a significant potential to be a new breakthrough for cancer treatment. The simple concept of nanoparticle-induced heating by the application of an alternating magnetic field has attracted much attention, as it allows the local heating of cancer cells, which are considered more susceptible to hyperthermia than healthy cells, while avoiding the side effects of traditional hyperthermia. Despite the potential of this therapeutic approach, the idea that local heating effects due to the application of alternating magnetic fields on magnetic nanoparticle-loaded cancer cells can be used as a treatment is controversial. Several studies indicate that the heating capacity of magnetic nanoparticles is largely reduced in the cellular environment because of increased viscosity, aggregation, and dipolar interactions. However, an increasing number of studies, both in vitro and in vivo, show evidence of successful magnetic hyperthermia treatment on several different types of cancer cells. This apparent contradiction might be due to the use of different experimental conditions. Here, we analyze the effects of several parameters on the cytotoxic efficiency of magnetic nanoparticles as heat inductors under an alternating magnetic field. Our results indicate that the cell-nanoparticle interaction reduces the cytotoxic effects of magnetic hyperthermia, independent of nanoparticle coating and core size, the cell line used, and the subcellular localization of nanoparticles. However, there seems to occur a synergistic effect between the application of an external source of heat and the presence of magnetic nanoparticles, leading to higher toxicities than those induced by heat alone or the accumulation of nanoparticles within cells.

Paclitaxel-Induced Ultrasmall Gallic Acid-Fe@BSA Self-Assembly with Enhanced MRI Performance and Tumor Accumulation for Cancer Theranostics

Ultrasmall nanoparticles have attracted great attention because of their efficient renal clearance. However, their bioapplication is still severely hampered by the poor performance derived from low tumor accumulation. Here, a large, self-assembled nanoparticle was designed for cancer theranostics and used with paclitaxel (PTX) to assemble bovine serum albumin-coated ultrasmall gallic acid-Fe(III) (GA-Fe@BSA-PTX) nanoparticles by the hydrophobic effect. The GA-Fe@BSA-PTX self-assembled nanoparticles featured appropriate size (∼115 nm), high water dispersity and stability, and low cell toxicity. Importantly, the magnetic resonance imaging performance and tumor accumulation of GA-Fe@BSA-PTX self-assembled nanoparticles were much better than those of the ultrasmall GA-Fe@BSA nanoparticles. Furthermore, the GA-Fe@BSA-PTX self-assembled nanoparticles exhibited an excellent therapeutic effect on tumors, owing to the combined chemo- and photothermal effects. This work highlights the great potential of the as-synthesized GA-Fe@BSA-PTX self-assembled nanoparticles as a multifunctional theranostic nanoplatform, offering compelling opportunities for theranostic applications in the clinic.

Magnetic properties of nanoparticles as a function of their spatial distribution on liposomes and cells

The aggregation processes of magnetic nanoparticles in biosystems are analysed by comparing the magnetic properties of three systems with different spatial distributions of the nanoparticles. The first one is iron oxide nanoparticles (NPs) of 14 nm synthesized by coprecipitation with two coatings, (3-aminopropyl)trimethoxysilane (APS) and dimercaptosuccinic acid (DMSA). The second one is liposomes with encapsulated nanoparticles, which have different configurations depending on the NP coating (NPs attached to the liposome surface or encapsulated in its aqueous volume). The last system consists of two cell lines (Pan02 and Jurkat) incubated with the NPs. Dynamic magnetic behaviour (AC) was analysed in liquid samples, maintaining their colloidal properties, while quasi-static (DC) magnetic measurements were performed on lyophilised samples. AC measurements provide a direct method for determining the effect of the environment on the magnetization relaxation of nanoparticles. Thus, the imaginary (χ'') component shifts to lower frequencies as the aggregation state increases from free nanoparticles to those attached or embedded into liposomes in cell culture media and more pronounced when internalized by the cells. DC magnetization curves show no degradation of the NPs after interaction with biosystems in the analysed timescale. However, the blocking temperature is shifted to higher temperatures for the nanoparticles in contact with the cells, regardless of the location, the incubation time, the cell line and the nanoparticle coating, supporting AC susceptibility data. These results indicate that the simple fact of being in contact with the cells makes the nanoparticles aggregate in a non-controlled way, which is not the same kind of aggregation caused by the contact with the cell medium nor inside liposomes.

A Novel Metal-Based Imaging Probe for Targeted Dual-Modality SPECT/MR Imaging of Angiogenesis

Superparamagnetic iron oxide nanoparticles with well-integrated multimodality imaging properties have generated increasing research interest in the past decade, especially when it comes to the targeted imaging of tumors. Bevacizumab (BCZM) on the other hand is a well-known and widely applied monoclonal antibody recognizing VEGF-A, which is overexpressed in angiogenesis. The aim of this proof-of-concept study was to develop a dual-modality nanoplatform for in vivo targeted single photon computed emission tomography (SPECT) and magnetic resonance imaging (MRI) of tumor vascularization. Iron oxide nanoparticles (IONPs) have been coated with dimercaptosuccinic acid (DMSA), for consequent functionalization with the monoclonal antibody BCZM radiolabeled with 99mTc, via well-developed surface engineering. The IONPs were characterized based on their size distribution, hydrodynamic diameter and magnetic properties. In vitro cytotoxicity studies showed that our nanoconstruct does not cause toxic effects in normal and cancer cells. Fe3O4-DMSA-SMCC-BCZM-99mTc were successfully prepared at high radiochemical purity (>92%) and their stability in human serum and in PBS were demonstrated. In vitro cell binding studies showed the ability of the Fe3O4-DMSA-SMCC-BCZM-99mTc to bind to the VEGF-165 isoform overexpressed on M-165 tumor cells. The ex vivo biodistribution studies in M165 tumor-bearing SCID mice showed high uptake in liver, spleen, kidney and lungs. The Fe3O4-DMSA-SMCC-BCZM-99mTc demonstrated quick tumor accumulation starting at 8.9 ± 1.88%ID/g at 2 h p.i., slightly increasing at 4 h p.i. (16.21 ± 2.56%ID/g) and then decreasing at 24 h p.i. (6.01 ± 1.69%ID/g). The tumor-to-blood ratio reached a maximum at 24 h p.i. (~7), which is also the case for the tumor-to-muscle ratio (~18). Initial pilot imaging studies on an experimental gamma-camera and a clinical MR camera prove our hypothesis and demonstrate the potential of Fe3O4-DMSA-SMCC-BCZM-99mTc for targeted dual-modality imaging. Our findings indicate that Fe3O4-DMSA-SMCC-BCZM-99mTc IONPs could serve as an important diagnostic tool for biomedical imaging as well as a promising candidate for future theranostic applications in cancer.

Effect of Surface Chemistry and Associated Protein Corona on the Long-Term Biodegradation of Iron Oxide Nanoparticles In Vivo

The protein corona formed on the surface of a nanoparticle in a biological medium determines its behavior in vivo. Herein, iron oxide nanoparticles containing the same core and shell, but bearing two different surface coatings, either glucose or poly(ethylene glycol), were evaluated. The nanoparticles' protein adsorption, in vitro degradation, and in vivo biodistribution and biotransformation over four months were investigated. Although both types of nanoparticles bound similar amounts of proteins in vitro, the differences in the protein corona composition correlated to the nanoparticles biodistribution in vivo. Interestingly, in vitro degradation studies demonstrated faster degradation for nanoparticles functionalized with glucose, whereas the in vivo results were opposite with accelerated biodegradation and clearance of the nanoparticles functionalized with poly(ethylene glycol). Therefore, the variation in the degradation rate observed in vivo could be related not only to the molecules attached to the surface, but also with the associated protein corona, as the key role of the adsorbed proteins on the magnetic core degradation has been demonstrated in vitro.

Unravelling the mechanisms that determine the uptake and metabolism of magnetic single and multicore nanoparticles in a Xenopus laevis model

Multicore superparamagnetic nanoparticles have been proposed as ideal tools for some biomedical applications because of their high magnetic moment per particle, high specific surface area and long term colloidal stability. Through controlled aggregation and packing of magnetic cores it is possible to obtain not only single-core but also multicore and hollow spheres with internal voids. In this work, we compare toxicological properties of single and multicore nanoparticles. Both types of particles showed moderate in vitro toxicity (MTT assay) tested in Hep G2 (human hepatocellular carcinoma) and Caco-2 (human colorectal adenocarcinoma) cells. The influence of surface chemistry in their biological behavior was also studied after functionalization with O,O'-bis(2-aminoethyl) PEG (2000 Da). For the first time, these nanoparticles were evaluated in a Xenopus laevis model studying their whole organism toxicity and their impact upon iron metabolism. The degree of activation of the metabolic pathway depends on the size and surface charge of the nanoparticles which determine their uptake. The results also highlight the potential of Xenopus laevis model bridging the gap between in vitro cell-based assays and rodent models for toxicity assessment to develop effective nanoparticles for biomedical applications.