Individually Stabilized, Superparamagnetic Nanoparticles with Controlled Shell and Size Leading to Exceptional Stealth Properties and High Relaxivities

Ultrahigh-Resolution Visualization of Vascular Heterogeneity in Brain Tumors via Magnetic Nanoparticles-Enhanced Susceptibility-Weighted Imaging

The precise assessment of vascular heterogeneity in brain tumors is vital for diagnosing, grading, predicting progression, and guiding treatment decisions. However, currently, there is a significant shortage of high-resolution imaging approaches. Herein, we propose a contrast-enhanced susceptibility-weighted imaging (CE-SWI) utilizing the minimalist dextran-modified Fe3O4 nanoparticles (Dextran@Fe3O4 NPs) for ultrahigh-resolution mapping of vasculature in brain tumors. The Dextran@Fe3O4 NPs are prepared via a facile coprecipitation method under room temperature, and exhibit small hydrodynamic size (28 nm), good solubility, excellent biocompatibility, and high transverse relaxivity (r2*, 159.7 mM-1 s-1) under 9.4 T magnetic field. The Dextran@Fe3O4 NPs-enhanced SWI can increase the contrast-to-noise ratio (CNR) of cerebral vessels to 2.5 times that before injection and achieves ultrahigh-spatial-resolution visualization of microvessels as small as 0.1 mm in diameter. This advanced imaging capability not only allows for the detailed mapping of both enlarged peritumoral drainage vessels and the intratumoral microvessels, but also facilitates the sensitive imaging detection of vascular permeability deterioration in a C6 cells-bearing rat glioblastoma model. Our proposed Dextran@Fe3O4 NPs-enhanced SWI provides a powerful imaging technique with great clinical translation potential for the precise theranostics of brain tumors.

Recent advancements in nanomaterial-mediated ferroptosis-induced cancer therapy: Importance of molecular dynamics and novel strategies

Ferroptosis is a novel type of controlled cell death resulting from an imbalance between oxidative harm and protective mechanisms, demonstrating significant potential in combating cancer. It differs from other forms of cell death, such as apoptosis and necrosis. Molecular therapeutics have hard time playing the long-acting role of ferroptosis induction due to their limited water solubility, low cell targeting capacity, and quick metabolism in vivo. To this end, small molecule inducers based on biological factors have long been used as strategy to induce cell death. Research into ferroptosis and advancements in nanotechnology have led to the discovery that nanomaterials are superior to biological medications in triggering ferroptosis. Nanomaterials derived from iron can enhance ferroptosis induction by directly releasing large quantities of iron and increasing cell ROS levels. Moreover, utilizing nanomaterials to promote programmed cell death minimizes the probability of unfavorable effects induced by mutations in cancer-associated genes such as RAS and TP53. Taken together, this review summarizes the molecular mechanisms involved in ferroptosis along with the classification of ferroptosis induction. It also emphasized the importance of cell organelles in the control of ferroptosis in cancer therapy. The nanomaterials that trigger ferroptosis are categorized and explained. Iron-based and noniron-based nanomaterials with their characterization at the molecular and cellular levels have been explored, which will be useful for inducing ferroptosis that leads to reduced tumor growth. Within this framework, we offer a synopsis, which traverses the well-established mechanism of ferroptosis and offers practical suggestions for the design and therapeutic use of nanomaterials.

Feature Matching of Microsecond-Pulsed Magnetic Fields Combined with Fe3O4 Particles for Killing A375 Melanoma Cells

The combination of magnetic fields and magnetic nanoparticles (MNPs) to kill cancer cells by magneto-mechanical force represents a novel therapy, offering advantages such as non-invasiveness, among others. Pulsed magnetic fields (PMFs) hold promise for application in this therapy due to advantages such as easily adjustable parameters; however, they suffer from the drawback of narrow pulse width. In order to fully exploit the potential of PMFs and MNPs in this therapy, while maximizing therapeutic efficacy within the constraints of the narrow pulse width, a feature-matching theory is proposed, encompassing the matching of three aspects: (1) MNP volume and critical volume of Brownian relaxation, (2) relaxation time and pulse width, and (3) MNP shape and the intermittence of PMF. In the theory, a microsecond-PMF generator was developed, and four kinds of MNPs were selected for in vitro cell experiments. The results demonstrate that the killing rate of the experimental group meeting the requirements of the theory is at least 18% higher than the control group. This validates the accuracy of our theory and provides valuable guidance for the further application of PMFs in this therapy.

Dual Nanoparticle Conjugates for Highly Sensitive and Versatile Sensing Using 19 F Magnetic Resonance Imaging

Fluorine magnetic resonance imaging (19 F MRI) has emerged as an attractive alternative to conventional 1 H MRI due to enhanced specificity deriving from negligible background signal in this modality. We report a dual nanoparticle conjugate (DNC) platform as an aptamer-based sensor for use in 19 F MRI. DNC consists of core-shell nanoparticles with a liquid perfluorocarbon core and a mesoporous silica shell (19 F-MSNs), which give a robust 19 F MR signal, and superparamagnetic iron oxide nanoparticles (SPIONs) as magnetic quenchers. Due to the strong magnetic quenching effects of SPIONs, this platform is uniquely sensitive and functions with a low concentration of SPIONs (4 equivalents) relative to 19 F-MSNs. The probe functions as a "turn-on" sensor using target-induced dissociation of DNA aptamers. The thrombin binding aptamer was incorporated as a proof-of-concept (DNCThr ), and we demonstrate a significant increase in 19 F MR signal intensity when DNCThr is incubated with human α-thrombin. This proof-of-concept probe is highly versatile and can be adapted to sense ATP and kanamycin as well. Importantly, DNCThr generates a robust 19 F MRI "hot-spot" signal in response to thrombin in live mice, establishing this platform as a practical, versatile, and biologically relevant molecular imaging probe.

Brownian Relaxation Shakes and Breaks Magnetic Iron Oxide-Polymer Nanocomposites to Release Cargo

Magnetic nanoparticles (NPs) are widely employed for remote controlled molecular release applications using alternating magnetic fields (AMF). Yet, they intrinsically generate heat in the process by Néel relaxation limiting their application scope. In contrast, iron oxide NPs larger than ≈15 nm react to AMF by Brownian relaxation resulting in tumbling and shaking. Here, such iron oxide NPs are combined with polymer shells where the shaking motion mechanically agitates and partially detaches the polymer chains, covalently cleaves a fraction of the polymers, and releases the prototypical cargo molecules doxorubicin and curcumin into solution. This heat-free release mechanism broadens the potential application space of polymer-functionalized magnetic NP composites.

Grafting of Cyclodextrin to Theranostic Nanoparticles Improves Blood-Brain Barrier Model Crossing

Core-shell superparamagnetic iron oxide nanoparticles hold great promise as a theranostic platform in biological systems. Herein, we report the biological effect of multifunctional cyclodextrin-appended SPIONs (CySPION) in mutant Npc1-deficient CHO cells compared to their wild type counterparts. CySPIONs show negligible cytotoxicity while they are strongly endocytosed and localized in the lysosomal compartment. Through their bespoke pH-sensitive chemistry, these nanoparticles release appended monomeric cyclodextrins to mobilize over-accumulated cholesterol and eject it outside the cells. CySPIONs show a high rate of transport across blood-brain barrier models, indicating their promise as a therapeutic approach for cholesterol-impaired diseases affecting the brain.

Synthesis and characterization of a macromolecular magnetic resonance imaging and delivery system with hyaluronic acid as a carrier

Using hyaluronic acid (HA) as macromolecular drug carriers, a glutathione-responsive imaging drug delivery system HA-SS-a-Gd-DOTA was formed by conjugating gadolinium chelates and cytarabine. This system exhibited T₁-reflexivity (21.9 mmol^-1 L s^-1, 0.5 T) that was higher than that of gadoterate meglumine. In an acidic environment, in vitro drug release reached 63.4% in 24 h. Low cytotoxicity indicated that this system has good biocompatibility. In vivo mouse imaging studies showed that tumor signaling was significantly enhanced. About 58% of the signal enhancement was obtained 50 min after injection of the drug. The degradation of the hyaluronic acid macromolecular chains in vivo makes it an ideal tumor imaging diagnostic agent because it did not cause damage to important organs of the mice.

Advanced Nanotechnology Approaches as Emerging Tools in Cellular-Based Technologies

Stem cells are valuable tools in regenerative medicine because they can generate a wide variety of cell types and tissues that can be used to treat or replace damaged tissues and organs. However, challenges related to the application of stem cells in the scope of regenerative medicine have urged scientists to utilize nanomedicine as a prerequisite to circumvent some of these hurdles. Nanomedicine plays a crucial role in this process and manipulates surface biology, the fate of stem cells, and biomaterials. Many attempts have been made to modify cellular behavior and improve their regenerative ability using nano-based strategies. Notably, nanotechnology applications in regenerative medicine and cellular therapies are controversial because of ethical and legal considerations. Therefore, this review describes nanotechnology in cell-based applications and focuses on newly proposed nano-based approaches. Cutting-edge strategies to engineer biological tissues and the ethical, legal, and social considerations of nanotechnology in regenerative nanomedicine applications are also discussed.

Anticancer Nanotherapeutics in Clinical Trials: The Work behind Clinical Translation of Nanomedicine

The ultimate goal of nanomedicine has always been the generation of translational technologies that can ameliorate current therapies. Cancer disease represented the primary target of nanotechnology applied to medicine, since its clinical management is characterized by very toxic therapeutics. In this effort, nanomedicine showed the potential to improve the targeting of different drugs by improving their pharmacokinetics properties and to provide the means to generate new concept of treatments based on physical treatments and biologics. In this review, we considered different platforms that reached the clinical trial investigation, providing an objective analysis about their physical and chemical properties and the working mechanism at the basis of their tumoritr opic properties. With this review, we aim to help other scientists in the field in conceiving their delivering platforms for clinical translation by providing solid examples of technologies that eventually were tested and sometimes approved for human therapy.

Recent advances in drug delivery and targeting to the brain

Our body keeps separating the toxic chemicals in the blood from the brain. A significant number of drugs do not enter the central nervous system (CNS) due to the blood-brain barrier (BBB). Certain diseases, such as tumor growth and stroke, are known to increase the permeability of the BBB. However, the heterogeneity of this permeation makes it difficult and unpredictable to transport drugs to the brain. In recent years, research has been directed toward increasing drug penetration inside the brain, and nanomedicine has emerged as a promising approach. Active targeting requires one or more specific ligands on the surface of nanoparticles (NPs), which brain endothelial cells (ECs) recognize, allowing controlled drug delivery compared to conventional targeting strategies. This review highlights the mechanistic insights about different cell types contributing to the development and maintenance of the BBB and summarizes the recent advancement in brain-specific NPs for different pathological conditions. Furthermore, fundamental properties of brain-targeted NPs will be discussed, and the standard lesion features classified by neurological pathology are summarized.

Ferrofluids and bio-ferrofluids: looking back and stepping forward

Ferrofluids investigated along for about five decades are ultrastable colloidal suspensions of magnetic nanoparticles, which manifest simultaneously fluid and magnetic properties. Their magnetically controllable and tunable feature proved to be from the beginning an extremely fertile ground for a wide range of engineering applications. More recently, biocompatible ferrofluids attracted huge interest and produced a considerable increase of the applicative potential in nanomedicine, biotechnology and environmental protection. This paper offers a brief overview of the most relevant early results and a comprehensive description of recent achievements in ferrofluid synthesis, advanced characterization, as well as the governing equations of ferrohydrodynamics, the most important interfacial phenomena and the flow properties. Finally, it provides an overview of recent advances in tunable and adaptive multifunctional materials derived from ferrofluids and a detailed presentation of the recent progress of applications in the field of sensors and actuators, ferrofluid-driven assembly and manipulation, droplet technology, including droplet generation and control, mechanical actuation, liquid computing and robotics.

Targeted Drug Delivery for the Treatment of Blood Cancers

Blood cancers are a type of liquid tumor which means cancer is present in the body fluid. Multiple myeloma, leukemia, and lymphoma are the three common types of blood cancers. Chemotherapy is the major therapy of blood cancers by systemic administration of anticancer agents into the blood. However, a high incidence of relapse often happens, due to the low efficiency of the anticancer agents that accumulate in the tumor site, and therefore lead to a low survival rate of patients. This indicates an urgent need for a targeted drug delivery system to improve the safety and efficacy of therapeutics for blood cancers. In this review, we describe the current targeting strategies for blood cancers and recently investigated and approved drug delivery system formulations for blood cancers. In addition, we also discuss current challenges in the application of drug delivery systems for treating blood cancers.

Modifying superparamagnetic iron oxide and silica nanoparticles surfaces for efficient (MA)LDI-MS analyses of peptides and proteins

RATIONALE

Surface functionalization is considered to be the foundation for developing nanomaterial applications in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analyses. However, the surface properties of nanostructures can influence their interaction with the analyte and consequently the mass data. In the present study, functionalized nanoparticles (NPs) were used for MALDI-MS and laser desorption/ionization mass spectrometry (LDI-MS) experiments in order to evaluate the effect of the surface properties of NPs on tailoring the intensity of mass signals.

METHODS

Regarding the LDI-MS analyses, the surface of superparamagnetic iron oxide nanoparticles (SPIONs) was coated with nitrosonium tetrafluoroborate, citric acid, nitrodopamine, and gallic acid. Additionally, the SPIONs were applied as a matrix to analyze three small peptides. In the MALDI-MS analyses, silica NPs were selected as co-matrix and functionalized with cysteine, sulfobetaine, and amine alkoxysilanes. Then, the silica NPs were utilized as additives in the MALDI-MS samples of four proteins in a mass range between ~2000 and 60,000 Da.

RESULTS

The results of LDI-MS analyses demonstrated more than one order enhancement in the signal intensity of analytes based on the amount of electrostatic interaction and laser energy absorption by the surface ligands. However, those of MALDI-MS experiments indicated a significant signal improvement when achieving the colloidal stability of silica NPs in the matrix solution.

CONCLUSIONS

Based on the results, the surface properties of NPs affected the (MA)LDI-MS analyses indispensably. Finally, the functionalization of SPIONs represented a new model for the future development of NPs with both affinity and enhanced ionization abilities in mass spectrometry.

Chitosan, Polyethylene Glycol and Polyvinyl Alcohol Modified MgFe2O4 Ferrite Magnetic Nanoparticles in Doxorubicin Delivery: A Comparative Study In Vitro

Cancer-based magnetic theranostics has gained significant interest in recent years and can contribute as an influential archetype in the effective treatment of cancer. Owing to their excellent biocompatibility, minute sizes and reactive functional surface groups, magnetic nanoparticles (MNPs) are being explored as potential drug delivery systems. In this study, MgFe₂O₄ ferrite MNPs were evaluated for their potential to augment the delivery of the anticancer drug doxorubicin (DOX). These MNPs were successfully synthesized by the glycol-thermal method and functionalized with the polymers; chitosan (CHI), polyvinyl alcohol (PVA) and polyethylene glycol (PEG), respectively, as confirmed by Fourier transform infrared (FTIR) spectroscopy. X-ray diffraction (XRD) confirmed the formation of the single-phase cubic spinel structures while vibrating sample magnetometer (VSM) analysis confirmed the superparamagnetic properties of all MNPs. Transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA) revealed small, compact structures with good colloidal stability. CHI-MNPs had the highest DOX encapsulation (84.28%), with the PVA-MNPs recording the lowest encapsulation efficiency (59.49%). The 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT) cytotoxicity assays conducted in the human embryonic kidney (HEK293), colorectal adenocarcinoma (Caco-2), and breast adenocarcinoma (SKBR-3) cell lines showed that all the drug-free polymerized MNPs promoted cell survival, while the DOX loaded MNPs significantly reduced cell viability in a dose-dependent manner. The DOX-CHI-MNPs possessed superior anticancer activity (<40% cell viability), with approximately 85.86% of the drug released after 72 h in a pH-responsive manner. These MNPs have shown good potential in enhancing drug delivery, thus warranting further optimizations and investigations.

Bio-inspired surface modification of iron oxide nanoparticles for active stabilization in hydrogels

Biological materials employ a variety of dynamic interactions in sophisticated composite structures to function adaptively on different time and length scales. Inspired by such designs we develop a novel surface modification approach to promote dynamic interactions between nanoparticles and polymer chains in physical and double network hydrogels. Physical hydrogels are formed via reversible complexation of borate ions with poly(vinyl alcohol) (PVA) and chemical crosslinks are introduced by electron beam irradiation. Dopamine is used for surface modification of magnetic iron oxide nanoparticles (MNPs) in two different ways: the direct treatment results in anchoring via catechol groups, whereas the indirect method leaves the catechol group on the free surface of MNPs. Although the former particles show very good colloidal stability, they lower the network connectivity, which results in lower plateau modulus, faster terminal relaxation, and lower yield stress, presumably due to imposing an extra distance between PVA chains. In contrast to this passive design, the latter particles actively reinforce the network by forming clusters of physical bonds between catechol groups of the individual particles and the monodiol complexes of the borate ions and PVA chains. Moreover, the additional complexes formed upon the introduction of nanoparticles with active surfaces provide further energy dissipation potential and therefore enhance the toughness. This approach can help develop novel hydrogels with superior toughness and multiple stimuli-responsiveness.

Polymer Brush-Grafted Nanoparticles Preferentially Interact with Opsonins and Albumin

Nanoparticles find increasing applications in life science and biomedicine. The fate of nanoparticles in a biological system is determined by their protein corona, as remodeling of their surface properties through protein adsorption triggers specific recognition such as cell uptake and immune system clearance and nonspecific processes such as aggregation and precipitation. The corona is a result of nanoparticle–protein and protein–protein interactions and is influenced by particle design. The state-of-the-art design of biomedical nanoparticles is the core–shell structure exemplified by superparamagnetic iron oxide nanoparticles (SPIONs) grafted with dense, well-hydrated polymer shells used for biomedical magnetic imaging and therapy. Densely grafted polymer chains form a polymer brush, yielding a highly repulsive barrier to the formation of a protein corona via nonspecific particle–protein interactions. However, recent studies showed that the abundant blood serum protein albumin interacts with dense polymer brush-grafted SPIONs. Herein, we use isothermal titration calorimetry to characterize the nonspecific interactions between human serum albumin, human serum immunoglobulin G, human transferrin, and hen egg lysozyme with monodisperse poly(2-alkyl-2-oxazoline)-grafted SPIONs with different grafting densities and core sizes. These particles show similar protein interactions despite their different “stealth” capabilities in cell culture. The SPIONs resist attractive interactions with lysozymes and transferrins, but they both show a significant exothermic enthalpic and low exothermic entropic interaction with low stoichiometry for albumin and immunoglobulin G. Our results highlight that protein size, flexibility, and charge are important to predict protein corona formation on polymer brush-stabilized nanoparticles.

Updates on the applications of iron-based nanoplatforms in tumor theranostics

With the development of biomedicine and materials science, the emerging research of iron-based nanoplatforms (INPs) have provided a bright future for tumor theranostics. Thanks to its excellent biocompatibility and diverse application potential, some INPs have successfully transformed from the laboratory to the clinic and market, making it one of the most successful nanoplatforms. Further investigations associated with its enormous biomedical potential is continuing, and new features of them are being demonstrated. The discovery of ferroptosis therapy opens up new avenue for the applications of INPs in tumor therapy, which is attracting tremendous attention from worldwide. It is well established that some of the INPs are capable of triggering the tumor cell ferroptosis efficiently, accelerating the tumor cell death process. Combined with anti-tumor drugs or other tumor therapy approaches, the INPs-induced ferroptosis are expected to break the bottleneck in the treatment of drug-resistant malignant tumors. In addition, other applications of INPs in tumor theranostics field are still active. Featured with the catalase-like ability, INPs were also well documented to reverse the tumor hypoxia as nanozymes, assisting and enhancing the oxygen-consuming tumor therapy approaches. And the unique magnetic property of INPs endow it with great potential in tumor diagnosis, hyperthermal therapy and target drug delivery. It is of great significance to summarize these new advances. Herein, the latest reports of the applications of INPs in tumor theranostics are classified to expound the trend of its research and development. The featured functions of it will be discussed in detail to provide a new insight. The key issues needing to be addressed and the development prospective will be put forward. We hope that this review will be helpful to understand the ample potential of INPs in tumor theranostics field.

Understanding Nanoparticle Toxicity to Direct a Safe-by-Design Approach in Cancer Nanomedicine

Nanomedicine is a rapidly growing field that uses nanomaterials for the diagnosis, treatment and prevention of various diseases, including cancer. Various biocompatible nanoplatforms with diversified capabilities for tumor targeting, imaging, and therapy have materialized to yield individualized therapy. However, due to their unique properties brought about by their small size, safety concerns have emerged as their physicochemical properties can lead to altered pharmacokinetics, with the potential to cross biological barriers. In addition, the intrinsic toxicity of some of the inorganic materials (i.e., heavy metals) and their ability to accumulate and persist in the human body has been a challenge to their translation. Successful clinical translation of these nanoparticles is heavily dependent on their stability, circulation time, access and bioavailability to disease sites, and their safety profile. This review covers preclinical and clinical inorganic-nanoparticle based nanomaterial utilized for cancer imaging and therapeutics. A special emphasis is put on the rational design to develop non-toxic/safe inorganic nanoparticle constructs to increase their viability as translatable nanomedicine for cancer therapies.

Polymer Topology Determines the Formation of Protein Corona on Core-Shell Nanoparticles

Linear and cyclic poly(2-ethyl-2-oxazoline) (PEOXA) adsorbates provide excellent colloidal stability to superparamagnetic iron oxide nanoparticles (FexOy NPs) within protein-rich media. However, dense shells of linear PEOXA brushes cannot prevent weak but significant attractive interactions with human serum albumin. In contrast, their cyclic PEOXA counterparts quantitatively hinder protein adsorption, as demonstrated by a combination of dynamic light scattering and isothermal titration calorimetry. The cyclic PEOXA brushes generate NP shells that are denser and more compact than their linear counterparts, entirely preventing the formation of a protein corona as well as aggregation, even when the lower critical solution temperature of PEOXA in a physiological buffer is reached.

Core-Shell Imidazoline-Functionalized Mesoporous Silica Superparamagnetic Hybrid Nanoparticles as a Potential Theranostic Agent for Controlled Delivery of Platinum(II) Compound

Introduction

As widely used chemotherapeutic agents, platinum compounds have several therapeutic challenges, such as drug resistance and adverse effects. Theranostic systems, macromolecular or colloidal therapeutics with companion diagnostics, not only address controlled drug delivery but also enable real-time monitoring of tumor sites.

Methods

Synthesis of magnetic mesoporous silica nanoparticles (MMSNs) was performed for dual magnetic resonance imaging and drug delivery. MMSN surfaces were modified by imidazoline groups (MMSN-Imi) for cisplatin (Cis-Pt) conjugation via free N-termini to achieve well-controlled drug-release kinetics. Cis-Pt adsorption isotherms and drug-release profile at pH 5 and 7.4 were investigated using inductively coupled plasma atomic emission spectroscopy.

Results

MMSN-Imi showed a specific surface area of 517.6 m² g⁻¹, mean pore diameter of 3.26 nm, and saturated magnetization of 53.63 emu/g. A relatively high r₂/r₁ relaxivity value was obtained for MMSN-Imi. The nanoparticles provided high Cis-Pt loading with acceptable loading capacity (~30% w:w). Sustained release of Cis-Pt under acidic conditions led to specific inhibitory effects on the growth of human epithelial ovarian carcinoma cells, determined using MTT assays. Dual acridine orange–propidium iodide staining was investigated, confirming induction of apoptosis and necrotic cell death.

Conclusion

MMSN-Imi exhibited potential for applications in cancer chemotherapy and combined imaging.

Magnetic core-shell nanowires as MRI contrast agents for cell tracking

BACKGROUND

Identifying the precise location of cells and their migration dynamics is of utmost importance for achieving the therapeutic potential of cells after implantation into a host. Magnetic resonance imaging is a suitable, non-invasive technique for cell monitoring when used in combination with contrast agents.

RESULTS

This work shows that nanowires with an iron core and an iron oxide shell are excellent materials for this application, due to their customizable magnetic properties and biocompatibility. The longitudinal and transverse magnetic relaxivities of the core-shell nanowires were evaluated at 1.5 T, revealing a high performance as T2 contrast agents. Different levels of oxidation and various surface coatings were tested at 7 T. Their effects on the T2 contrast were reflected in the tailored transverse relaxivities. Finally, the detection of nanowire-labeled breast cancer cells was demonstrated in T2-weighted images of cells implanted in both, in vitro in tissue-mimicking phantoms and in vivo in mouse brain. Labeling the cells with a nanowire concentration of 0.8 μg of Fe/mL allowed the detection of 25 cells/µL in vitro, diminishing the possibility of side effects. This performance enabled an efficient labelling for high-resolution cell detection after in vivo implantation (~ 10 nanowire-labeled cells) over a minimum of 40 days.

CONCLUSIONS

Iron-iron oxide core-shell nanowires enabled the efficient and longitudinal cellular detection through magnetic resonance imaging acting as T2 contrast agents. Combined with the possibility of magnetic guidance as well as triggering of cellular responses, for instance by the recently discovered strong photothermal response, opens the door to new horizons in cell therapy and make iron-iron oxide core-shell nanowires a promising theranostic platform.

Recent Advancements of Magnetic Nanomaterials in Cancer Therapy

Magnetic nanomaterials belong to a class of highly-functionalizable tools for cancer therapy owing to their intrinsic magnetic properties and multifunctional design that provides a multimodal theranostics platform for cancer diagnosis, monitoring, and therapy. In this review article, we have provided an overview of the various applications of magnetic nanomaterials and recent advances in the development of these nanomaterials as cancer therapeutics. Moreover, the cancer targeting, potential toxicity, and degradability of these nanomaterials has been briefly addressed. Finally, the challenges for clinical translation and the future scope of magnetic nanoparticles in cancer therapy are discussed.

New Frontiers in Molecular Imaging with Superparamagnetic Iron Oxide Nanoparticles (SPIONs): Efficacy, Toxicity, and Future Applications

Supermagnetic Iron Oxide Nanoparticles (SPIONs) are nanoparticles that have an iron oxide core and a functionalized shell. SPIONs have recently raised much interest in the scientific community, given their exciting potential diagnostic and theragnostic applications. The possibility to modify their surface and the characteristics of their core make SPIONs a specific contrast agent for magnetic resonance imaging but also an intriguing family of tracer for nuclear medicine. An example is 68Ga-radiolabeled bombesin-conjugated to superparamagnetic nanoparticles coated with trimethyl chitosan that is selective for the gastrin-releasing peptide receptors. These receptors are expressed by several human cancer cells such as breast and prostate neoplasia. Since the coating does not interfere with the properties of the molecules bounded to the shell, it has been proposed to link SPIONs with antibodies. SPIONs can be used also to monitor the biodistribution of mesenchymal stromal cells and take place in various applications. The aim of this review of literature is to analyze the diagnostic aspect of SPIONs in magnetic resonance imaging and in nuclear medicine, with a particular focus on sentinel lymph node applications. Moreover, it is taken into account the possible toxicity and the effects on human physiology to determine the SPIONs' safety.

Targeting strategies for superparamagnetic iron oxide nanoparticles in cancer therapy

Among various nanoparticles, superparamagnetic iron oxide nanoparticles (SPIONs) have been increasingly studied for their excellent superparamagnetism, magnetic heating properties, and enhanced magnetic resonance imaging (MRI). The conjugation of SPIONs with drugs to obtain delivery nanosystems has several advantages including magnetic targeted functionalization, in vivo imaging, magnetic thermotherapy, and combined delivery of anticancer agents. To further increase the targeting efficiency of drugs through a delivery nanosystem based on SPIONs, additional targeting moieties including transferrin, antibodies, aptamers, hyaluronic acid, folate, and targeting peptides are coated onto the surface of SPIONs. Therefore, this review summarizes the latest progresses in the conjugation of targeting molecules and drug delivery nanosystems based on SPIONs, especially focusing on their performances to develop efficient targeted drug delivery systems for tumor therapy. STATEMENT OF SIGNIFICANCE: Some magnetic nanoparticle-based nanocarriers loaded with drugs were evaluated in patients and did not produce convincing results, leading to termination of clinical development in phase II/III. An alternative strategy for drug delivery systems based on SPIONs is the conjugation of these systems with targeting segments such as transferrin, antibodies, aptamers, hyaluronic acid, folate, and targeting peptides. These targeting moieties can be recognized by specific integrin/receptors that are overexpressed specifically on the tumor cell surface, resulting in minimizing dosage and reducing off-target effects. This review focuses on magnetic nanoparticle-based nonviral drug delivery systems with targeting moieties to deliver anticancer drugs, with an aim to provide suggestions on the development of SPIONs through discussion.

Preparation and Application of Magnetic Responsive Materials in Bone Tissue Engineering

At present, many kinds of materials are used for bone tissue engineering, such as polymer materials, metals, etc., which in general have good biocompatibility and mechanical properties. However, these materials cannot be controlled artificially after implantation, which may result in poor repair performance. The appearance of the magnetic response material enables the scaffolds to have the corresponding ability to the external magnetic field. Within the magnetic field, the magnetic response material can achieve the targeted release of the drug, improve the performance of the scaffold, and further have a positive impact on bone formation. This paper first reviewed the preparation methods of magnetic responsive materials such as magnetic nanoparticles, magnetic polymers, magnetic bioceramic materials and magnetic alloys in recent years, and then introduced its main applications in the field of bone tissue engineering, including promoting osteogenic differentiation, targets release, bioimaging, cell patterning, etc. Finally, the mechanism of magnetic response materials to promote bone regeneration was introduced. The combination of magnetic field treatment methods will bring significant progress to regenerative medicine and help to improve the treatment of bone defects and promote bone tissue repair.

Effect of Polymer Surface Modification of Superparamagnetic Iron Oxide Nanoparticle Dispersions in High Salinity Environments

Superparamagnetic nanoparticles (SPIONs) can be used as nuclear magnetic resonance (NMR) signal enhancement agents for petroleum exploration. This enhancement effect is uniform if SPIONs are monodisperse in size and in composition; yet it is challenging to synthesize monodisperse particles that do not aggregate in high salinity petroleum brine. Here, we report a method to synthesize individual SPIONs coated with tunable surface coating densities of poly(2-acrylamido-2-methyl-1-propanesulfonic acid (pAMPS) with a catechol end-group (pAMPS*). To establish parameters under which pAMPS*-coated SPIONS do not aggregate, we compared computational predictions with experimental results for variations in pAMPS* chain length and surface coverage. Using this combined theoretical and experimental approach, we show that singly dispersed SPIONs remained stabilized in petroleum brine for up to 75 h with high surface density pAMPS*.

Poly(ethylene glycol) Grafting of Nanoparticles Prevents Uptake by Cells and Transport Through Cell Barrier Layers Regardless of Shear Flow and Particle Size

It has long been a central tenet of biomedical research that coating of nanoparticles with hydrated polymers can improve their performance in biomedical applications. However, the efficacy of the approach in vivo is still debated. In vitro model systems to test the performance of engineered nanoparticles for in vivo applications often use nonrepresentative cell lines and conditions for uptake and toxicity tests. We use our platform of monodisperse iron oxide nanoparticles densely grafted with nitrodopamide-poly(ethylene glycol) (PEG) to probe cell interactions with a set of cell types and culture conditions that are relevant for applications in which nanoparticles are injected into the bloodstream. In the past, these particles have proved to have excellent stability and negligible interaction with proteins and membranes under physiological conditions. We test the influence of flow on the uptake of nanoparticles. We also investigate the transport through endothelial barrier cell layers, as well as the effect that PEG-grafted iron oxide nanoparticles have on cell layers relevant for nanoparticles injected into the bloodstream. Our results show that the dense PEG brush and resulting lack of nonspecific protein and membrane interaction lead to negligible cell uptake, toxicity, and transport across barrier layers. These results contrast with far less well-defined polymer-coated nanoparticles that tend to aggregate and consequently strongly interact with cells, for example, by endocytosis.

Design Principles for Thermoresponsive Core-Shell Nanoparticles: Controlling Thermal Transitions by Brush Morphology

In this feature article, we summarize our recent work on understanding and controlling the thermal behavior of nanoparticles grafted with thermoresponsive polymer shells. Precision synthesis of monodisperse superparamagnetic iron oxide nanocrystals was combined with irreversible dense grafting of nitrodopamide-anchored thermoresponsive polymer chains. We provide an overview of how the dense and stable grafting of biomedically relevant polymers, including poly(ethylene glycol), poly( N-isopropylacrylamide), polysarcosin, and polyoxazolines, can be achieved. This platform has made it possible for us to demonstrate that the polymer brush geometry, as defined by the nanoparticle core and relative polymer brush size, determines the thermal transitions of the polymer brush. We furthermore summarize our work on how the polymer shell transitions and nanoparticle aggregation can be tuned. With the independent variation of the core and the shell, we can optimize and precisely control the thermally controlled solubility of our system. Finally, our feature article gives examples relevant to current and future applications. We show how the thermal response of the shell influences the nanoparticle performance in biological fluids and interactions with proteins and cells, also under purely magnetic actuation of the nanoparticles through the superparamagnetic iron oxide core.

Superparamagnetic Iron Oxide Nanoparticles-Current and Prospective Medical Applications

The recent, fast development of nanotechnology is reflected in the medical sciences. Superparamagnetic Iron Oxide Nanoparticles (SPIONs) are an excellent example. Thanks to their superparamagnetic properties, SPIONs have found application in Magnetic Resonance Imaging (MRI) and magnetic hyperthermia. Unlike bulk iron, SPIONs do not have remnant magnetization in the absence of the external magnetic field; therefore, a precise remote control over their action is possible. This makes them also useful as a component of the advanced drug delivery systems. Due to their easy synthesis, biocompatibility, multifunctionality, and possibility of further surface modification with various chemical agents, SPIONs could support many fields of medicine. SPIONs have also some disadvantages, such as their high uptake by macrophages. Nevertheless, based on the ongoing studies, they seem to be very promising in oncological therapy (especially in the brain, breast, prostate, and pancreatic tumors). The main goal of our paper is, therefore, to present the basic properties of SPIONs, to discuss their current role in medicine, and to review their applications in order to inspire future developments of new, improved SPION systems.

Comparing Strategies for Magnetic Functionalization of Microbubbles

The advancement of ultrasound-mediated therapy has stimulated the development of drug-loaded microbubble agents that can be targeted to a region of interest through an applied magnetic field prior to ultrasound activation. However, the need to incorporate therapeutic molecules while optimizing the responsiveness to both magnetic and acoustic fields and maintaining adequate stability poses a considerable challenge for microbubble synthesis. The aim of this study was to evaluate three different methods for incorporating iron oxide nanoparticles (IONPs) into phospholipid-coated microbubbles using (1) hydrophobic IONPs within an oil layer below the microbubble shell, (2) phospholipid-stabilized IONPs within the shell, or (3) hydrophilic IONPs noncovalently bound to the surface of the microbubble. All microbubbles exhibited similar acoustic response at both 1 and 7 MHz. The half-life of the microbubbles was more than doubled by the addition of IONPs by using both surface and phospholipid-mediated loading methods, provided the lipid used to coat the IONPs was the same as that constituting the microbubble shell. The highest loading of IONPs per microbubble was also achieved with the surface loading method, and these microbubbles were the most responsive to an applied magnetic field, showing a 3-fold increase in the number of retained microbubbles compared to other groups. For the purpose of drug delivery, surface loading of IONPs could restrict the attachment of hydrophilic drugs to the microbubble shell, but hydrophobic drugs could still be incorporated. In contrast, although the incorporation of phospholipid IONPs produced more weakly magnetic microbubbles, it would not interfere with hydrophilic drug loading on the surface of the microbubble.

Thermoresponsive Core-Shell Nanoparticles: Does Core Size Matter?

Nanoparticles grafted with a dense brush of hydrophilic polymers exhibit high colloidal stability. However, reversible aggregation can be triggered by an increase in temperature if the polymer is thermoresponsive, as the polymer shell partly loses its hydration. We investigate the role of nanoparticle curvature on the critical solution temperature (CST) of grafted poly(2-isopropyl-2-oxazoline) (PiPOx) and critical flocculation temperature (CFT) of the core-shell nanoparticle dispersion. Cores with diameters ranging from 5 to 21 nm were studied by temperature-cycled dynamic light scattering and differential scanning calorimetry over a large range of concentrations. We show that core size and curvature only have a minor influence on particle aggregation (CFT and cluster size), while they have major influence on the CST of the polymer shell. The densely grafted shells exhibit three distinct solvation transitions, the relative contributions of each is controlled by the core curvature. We link these transitions to different polymer density regimes within the spherical brush and demonstrate that the CST of the innermost part of the brush coincides with the CFT of the particle dispersion.

Stealth Nanoparticles Grafted with Dense Polymer Brushes Display Adsorption of Serum Protein Investigated by Isothermal Titration Calorimetry

Core-shell nanoparticles receive much attention for their current and potential applications in life sciences. Commonly, a dense shell of hydrated polymer, a polymer brush, is grafted to improve colloidal stability of functional nanoparticles and to prevent protein adsorption, aggregation, cell recognition, and uptake. Until recently, it was widely assumed that a polymer brush shell indeed prevents strong association of proteins and that this leads to their superior "stealth" properties in vitro and in vivo. We show using T-dependent isothermal titration calorimetry on well-characterized monodisperse superparamagnetic iron oxide nanoparticles with controlled dense stealth polymer brush shells that "stealth" core-shell nanoparticles display significant attractive exothermic and enthalpic interactions with serum proteins, despite having excellent colloidal stability and negligible nonspecific cell uptake. This observation is at room temperature shown to depend only weakly on variation of iron oxide core diameter and type of grafted stealth polymer: poly(ethylene glycol), poly(ethyl oxazoline), poly(isopropyl oxazoline), and poly( N-isopropyl acrylamide). Polymer brush shells with a critical solution temperature close to body temperature showed a strong temperature dependence in their interactions with proteins with a significant increase in protein binding energy with increased temperature. The stoichiometry of interaction is estimated to be near 1:1 for PEGylated nanoparticles and up to 10:1 for larger thermoresponsive nanoparticles, whereas the average free energy of interaction is enthalpically driven and comparable to a weak hydrogen bond.

Dextran-coated superparamagnetic iron oxide nanoparticles for magnetic resonance imaging: evaluation of size-dependent imaging properties, storage stability and safety

BACKGROUND

Rising criticism of currently available contrast agents for magnetic resonance imaging, either due to their side effects or limited possibilities in terms of functional imaging, evoked the need for safer and more versatile agents. We previously demonstrated the suitability of novel dextran-coated superparamagnetic iron oxide nanoparticles (SPIONDex) for biomedical applications in terms of safety and biocompatibility.

METHODS

In the present study, we investigated the size-dependent cross-linking process of these particles as well as the size dependency of their imaging properties. For the latter purpose, we adopted a simple and easy-to-perform experiment to estimate the relaxivity of the particles. Furthermore, we performed an extensive analysis of the particles' storage stability under different temperature conditions, showing their superb stability and the lack of any signs of agglomeration or sedimentation during a 12 week period.

RESULTS

Independent of their size, SPIONDex displayed no irritation potential in a chick chorioallantoic membrane assay. Cell uptake studies of ultra-small (30 nm) SPIONDex confirmed their internalization by macrophages, but not by non-phagocytic cells. Additionally, complement activation-related pseudoallergy (CARPA) experiments in pigs treated with ultra-small SPIONDex indicated the absence of hypersensitivity reactions.

CONCLUSION

These results emphasize the exceptional safety of SPIONDex, setting them apart from the existing SPION-based contrast agents and making them a very promising candidate for further clinical development.

Polydopamine Surface Chemistry: A Decade of Discovery

Polydopamine is one of the simplest and most versatile approaches to functionalizing material surfaces, having been inspired by the adhesive nature of catechols and amines in mussel adhesive proteins. Since its first report in 2007, a decade of studies on polydopamine molecular structure, deposition conditions, and physicochemical properties have ensued. During this time, potential uses of polydopamine coatings have expanded in many unforeseen directions, seemingly only limited by the creativity of researchers seeking simple solutions to manipulating surface chemistry. In this review, we describe the current state of the art in polydopamine coating methods, describe efforts underway to uncover and tailor the complex structure and chemical properties of polydopamine, and identify emerging trends and needs in polydopamine research, including the use of dopamine analogs, nitrogen-free polyphenolic precursors, and improvement of coating mechanical properties.

Fluorescent Magnetopolymersomes: A Theranostic Platform to Track Intracellular Delivery

We present a potential theranostic delivery platform based on the amphiphilic diblock copolymer polybutadiene-block-poly (ethylene oxide) combining covalent fluorescent labeling and membrane incorporation of superparamagnetic iron oxide nanoparticles for multimodal imaging. A simple self-assembly and labeling approach to create the fluorescent and magnetic vesicles is described. Cell uptake of the densely PEGylated polymer vesicles could be altered by surface modifications that vary surface charge and accessibility of the membrane active species. Cell uptake and cytotoxicity were evaluated by confocal microscopy, transmission electron microscopy, iron content and metabolic assays, utilizing multimodal tracking of membrane fluorophores and nanoparticles. Cationic functionalization of vesicles promoted endocytotic uptake. In particular, incorporation of cationic lipids in the polymersome membrane yielded tremendously increased uptake of polymersomes and magnetopolymersomes without increase in cytotoxicity. Ultrastructure investigations showed that cationic magnetopolymersomes disintegrated upon hydrolysis, including the dissolution of incorporated iron oxide nanoparticles. The presented platform could find future use in theranostic multimodal imaging in vivo and magnetically triggered delivery by incorporation of thermorepsonsive amphiphiles that can break the membrane integrity upon magnetic heating via the embedded superparamagnetic nanoparticles.

A magnetically responsive nanocomposite scaffold combined with Schwann cells promotes sciatic nerve regeneration upon exposure to magnetic field

Peripheral nerve repair is still challenging for surgeons. Autologous nerve transplantation is the acknowledged therapy; however, its application is limited by the scarcity of available donor nerves, donor area morbidity, and neuroma formation. Biomaterials for engineering artificial nerves, particularly materials combined with supportive cells, display remarkable promising prospects. Schwann cells (SCs) are the absorbing seeding cells in peripheral nerve engineering repair; however, the attenuated biologic activity restricts their application. In this study, a magnetic nanocomposite scaffold fabricated from magnetic nanoparticles and a biodegradable chitosan-glycerophosphate polymer was made. Its structure was evaluated and characterized. The combined effects of magnetic scaffold (MG) with an applied magnetic field (MF) on the viability of SCs and peripheral nerve injury repair were investigated. The magnetic nanocomposite scaffold showed tunable magnetization and degradation rate. The MGs synergized with the applied MF to enhance the viability of SCs after transplantation. Furthermore, nerve regeneration and functional recovery were promoted by the synergism of SCs-loaded MGs and MF. Based on the current findings, the combined application of MGs and SCs with applied MF is a promising therapy for the engineering of peripheral nerve regeneration.

Synthesis of Distinct Iron Oxide Nanomaterial Shapes Using Lyotropic Liquid Crystal Solvents

A room temperature reduction-hydrolysis of Fe(III) precursors such as FeCl₃ or Fe(acac)₃ in various lyotropic liquid crystal phases (lamellar, hexagonal columnar, or micellar) formed by a range of ionic or neutral surfactants in H₂O is shown to be an effective and mild approach for the preparation of iron oxide (IO) nanomaterials with several morphologies (shapes and dimensions), such as extended thin nanosheets with lateral dimensions of several hundred nanometers as well as smaller nanoflakes and nanodiscs in the tens of nanometers size regime. We will discuss the role of the used surfactants and lyotropic liquid crystal phases as well as the shape and size differences depending upon when and how the resulting nanomaterials were isolated from the reaction mixture. The presented synthetic methodology using lyotropic liquid crystal solvents should be widely applicable to several other transition metal oxides for which the described reduction-hydrolysis reaction sequence is a suitable pathway to obtain nanoscale particles.

Enhanced cellular uptake of iron oxide nanoparticles modified with 1,2-dimyristoyl-sn-glycero-3-phosphocholine

DMPC greatly enhanced the cellular uptake of SPIONs, resulting in remarkable amounts of accumulated nanoparticles in PC-12 cells.