SPIONs: Superparamagnetic iron oxide-based nanoparticles for the delivery of microRNAi-therapeutics in cancer

Non-coding RNA (ncRNA)-based therapeutics that induce RNA interference (RNAi), such as microRNAs (miRNAs), have drawn considerable attention as a novel class of targeted cancer therapeutics because of their capacity to specifically target oncogenes/protooncogenes that regulate key signaling pathways involved in carcinogenesis, tumor growth and progression, metastasis, cell survival, proliferation, angiogenesis, and drug resistance. However, clinical translation of miRNA-based therapeutics, in particular, has been challenging due to the ineffective delivery of ncRNA molecules into tumors and their uptake into cancer cells. Recently, superparamagnetic iron oxide-based nanoparticles (SPIONs) have emerged as highly effective and efficient for the delivery of therapeutic RNAs to malignant tissues, as well as theranostic (therapy and diagnostic) applications, due to their excellent biocompatibility, magnetic responsiveness, broad functional surface modification, safety, and biodistribution profiles. This review highlights recent advances in the use of SPIONs for the delivery of ncRNA-based therapeutics with an emphasis on their synthesis and coating strategies. Moreover, the advantages and current limitations of SPIONs and their future perspectives are discussed.

Magnetic Fluids: The Interaction between the Microstructure, Macroscopic Properties, and Dynamics under Different Combinations of External Influences

Magnetic fluids were historically the first active nano-dispersion material. Despite over half a century of research, interest in these nano-objects continues to grow every year. This is due to the impressive development of nanotechnology, the synthesis of nanoscale structures, and surface-active systems. The unique combination of fluidity and magnetic response allows magnetic fluids to be used in engineering devices and biomedical applications. In this review, experimental results and fundamental theoretical approaches are systematized to predict the micro- and macroscopic behavior of magnetic fluid systems under different external influences. The article serves as working material for both experienced scientists in the field of magnetic fluids and novice specialists who are just beginning to investigate this topic.

Magnetic nanofluids (Ferrofluids): Recent advances, applications, challenges, and future directions

Impelled by the need to find solutions to new challenges of modern technologies new materials with unique properties are being explored. Among various new materials that emerged over the decades, magnetic fluids exhibiting interesting physiochemical properties (optical, thermal, magnetic, rheological, apparent density, etc.) under a magnetic stimulus have been at the forefront of research. In the initial phase, there has been a fervent scientific curiosity to understand the field-induced intriguing properties of such fluids but later a plethora of technological applications emerged. Magnetic nanofluid, popularly known as ferrofluid, is a colloidal suspension of fine magnetic nanoparticles, has been at the forefront of research because of its magnetically tunable physicochemical properties and applications. Due to their stimuli-responsive behaviour, they have been finding more applications in biology and other engineering disciplines in recent years. Therefore, a critical review of this topic highlighting the necessary background, the potential of this material for emerging technologies, and the latest developments is warranted. This review also provides a summary of various applications, along with the key challenges and future research directions. The first part of the review addresses the different types of magnetic fluids, the genesis of magnetic fluids, their synthesis methodologies, properties, and stabilization techniques are discussed in detail. The second part of the review highlights the applications of magnetic nanofluids and nanoemulsions (as model systems) in probing order-disorder transitions, scattering, diffraction, magnetically reconfigurable internal structures, molecular interaction, and weak forces between colloidal particles, conformational changes of macromolecules at interfaces and polymer-surfactant complexation at the oil-water interface. The last part of the review summarizes the interesting applications of magnetic fluids such as heat transfer, sensors (temperature, pH, urea detection, cations, defect detection sensors), tunable optical filters, removal of dyes, dynamic seals, magnetic hyperthermia-based cancer therapy and other biomedical applications. The applications of magnetic nanofluids in diverse disciplines are growing day by day, yet there are challenges in their practical adaptation as field-worthy or packaged products. This review provides a pedagogical description of magnetic fluids, with the necessary background, key concepts, physics, experimental protocols, design of experiments, challenges and future directions.

Thermal and rheological properties of magnetic nanofluids: Recent advances and future directions

Technological advancement and miniaturization of electronic gadgets fueled intense research on nanofluids as potential candidates for cooling applications as a substitute to conventional heat transfer fluids. Among nanofluids, magnetic nanofluids, traditionally known as ferrofluids have attracted a lot of attention owing to their magnetic field tunable thermal conductivity and rheological properties due to the aggregation of the magnetic nanoparticles into chains or columns in the presence of the magnetic field. The field-induced aggregates act as low resistance pathways thereby improving thermal transport substantially. Recent studies show that ferrofluids with smaller size and narrow size distribution display significant enhancement in thermal conductivity in the presence of a magnetic field with negligible viscosity enhancement, which is ideal for effective thermal management of electronic devices, especially in miniature electronic devices. On the contrary, highly polydisperse ferrofluids containing large aggregates, show modest enhancement in thermal conductivity in the presence of a magnetic field and a huge enhancement in viscosity. The most recent studies show that magnetic field ramp rate has a profound effect on aggregation kinetics and thermal and rheological properties. The viscosity enhancement under an external stimulus impedes their practical use in electronics cooling, which warrants the need to attain a high thermal conductivity to viscosity ratio, under a modest magnetic field. Though there are several reviews on heat transfer in nanofluids and hybrid nanofluids, a comprehensive review on fundamental understanding of field-induced thermal and rheological properties in magnetic fluids is missing in the literature. This review provides a pedagogical description of the fundamental understanding of field-induced thermal and rheological properties in magnetic fluids, with the necessary background, key concepts, definitions, mechanisms, theoretical models, experimental protocols, and design of experiments. Many important case studies are presented along with the experimental design aspects. The review also provides a summary of important experimental studies with key findings, along with the key challenges and future research directions. The review is an ideal material for experimentalists and theoreticians practicing in the field of magnetic fluids, and also serves as an excellent reference for freshers who indent to begin research on this topic.

Magnetic Trails: A Novel Artificial Pheromone for Swarm Robotics in Outdoor Environments

Swarm robotics finds inspiration in nature to model behaviors, such as the use of pheromone principles. Pheromones provide an indirect and decentralized communication scheme that have shown positive experimental results. Real implementations of pheromones have suffered from slow sensors and have been limited to controlled environments. This paper presents a novel technology to implement real pheromones for swarm robotics in outdoor environments by using magnetized ferrofluids. A ferrofluid solution, with its deposition and magnetization system, is detailed. The proposed substance does not possess harmful materials for the environment and can be safely handled by humans. Validation demonstrates that the substance represents successfully pheromone characteristics of locality, diffusion and evaporation on several surfaces in outdoor conditions. Additionally, the experiments show an improvement over the chemical representation of pheromones by using magnetic substances and existing magnetometer sensor technologies, which provide better response rates and recovery periods than MOX chemical sensors. The present work represents a step toward swarm robotics experimentation in uncontrolled outdoor environments. In addition, the presented pheromone technology may be use by the broad area of swarm robotics for robot exploration and navigation.

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.

Investigation of the Rheological Properties of Zn-Ferrite/Perfluoropolyether Oil-Based Ferrofluids

The rheological properties of ferrofluids are related to various applications, such as sealing and loudspeakers, and have therefore attracted widespread attention. However, the rheological properties and their influence on the mechanisms of perfluoropolyether oil (PFPE oil)-based ferrofluids are complicated and not clear. Here, a series of PFPE oil-based ferrofluids were synthesized via a chemical co-precipitation method, and their rheological properties were revealed, systematically. The results indicate that the prepared Zn-ferrite particles have an average size of 12.1 nm, within a range of 4–18 nm, and that the ferrofluids have excellent dispersion stability. The activity of the ferrofluids changes from Newtonian to non-Newtonian, then to solid-like with increasing w from 10 wt% to 45.5 wt%, owing to their variation in microstructures. The viscosity of the ferrofluids increases with increasing M_w (the molecular weight of base liquid PFPE oil polymer), attributed to the increase in entanglements between PFPE oil molecules. The magnetization temperature variation of Zn-ferrite nanoparticles and viscosity temperature variation of PFPE oil together contribute to the viscosity temperature change in ferrofluids. The viscosity of the ferrofluids basically remains unchanged when shear rate is above 50 s⁻¹, with increasing magnetic field strength; however, it first increases and then levels off when the rate is under 10 s⁻¹, revealing that the shear rate and magnetic field strength together affect viscosity. The viscosity and its alteration in Zn-ferrite/PFPE oil-based ferrofluids could be deduced through our work, which will be greatly significant in basic theoretical research and in various applications.

μSR-Study of a 3% CoFe2O4 Nanoparticle Concentration Ferrofluid

Magnetic fluids based on single-domain magnetic spinel ferrite nanoparticles dispersed in various liquid media are of particular practical and scientific interest. This paper presents a muon spectroscopy study of a ferrofluid based on magnetic nanoparticles of CoFe2O4 molecules dispersed in water (H2O) with a nanoparticle concentration of 3%. In this study, it was determined that the structure and magnitude of the magnetization of a ferrofluid depend on the viscosity of the liquid itself. It was shown that, at room temperature (290 K) and under an external magnetic field of 527 G, the observed additional magnetization was ~20 G. In a small fraction of the sample under study (~20%), negative magnetization (diamagnetism) was observed. At low temperatures (~30 K), the sample acted as a paramagnet in a magnetic field. For the first time, the magnetic field inside and in the immediate vicinity of a CoFe2O4 nanoparticle has been measured experimentally using the μSR method: the value was 1.96 ± 0.44 kG; thus, direct measurement of the magnetization of a nanoscale object was performed.

Effective fields in magnetic colloids and features of their magnetization kinetics

We present results of magnetization and magnetic susceptibility dependence investigations performed for undecane-based ferrofluids with dominant of Brownian relaxation for particles. A robust and effective method of fine particle size characterization is presented. It is based on the core-shell model and the analysis of the dependence of saturation magnetization on particle concentration. A novel advantage method has been used as a straightforward way to determine the concentration dependence of the effective field related to particle interaction that was calculated from the experimentally obtained concentration dependence of low field susceptibility. The computed relationship is compared with the concentration dependences of effective fields derived from several well-known theoretical models. We present some peculiarities of the real part of dynamic magnetic susceptibility on temperature. Investigated features are defined both by the magnetic state of fine particles and by crystallization of carrier at the liquid to a solid phase transition. For the first time, the dependence of the magnetization relaxation time on the colloidal particle concentration and the magnitude of bias DC magnetic field was investigated experimentally. Results are in good agreement with theoretical predictions for moderate concentration and significantly differs for concentration greater 7 vol%. It is concluded that this effect can be related either to the enhanced particle interaction or to the transition of some particles from superparamagnetic to a ferromagnetic state. These predictions are verified through the calculation in terms of Cole-Cole diagrams methods.

Review on the advancements of magnetic gels: towards multifunctional magnetic liposome-hydrogel composites for biomedical applications

Magnetic gels have been gaining great attention in nanomedicine, as they combine features of hydrogels and magnetic nanoparticles into a single system. The incorporation of liposomes in magnetic gels further leads to a more robust multifunctional system enabling more functions and spatiotemporal control required for biomedical applications, which includes on-demand drug release. In this review, magnetic gels components are initially introduced, as well as an overview of advancements on the development, tuneability, manipulation and application of these materials. After a discussion of the advantages of combining hydrogels with liposomes, the properties, fabrication strategies and applications of magnetic liposome-hydrogel composites (magnetic lipogels or magnetolipogels) are reviewed. Overall, the progress of magnetic gels towards smart multifunctional materials are emphasized, considering the contributions for future developments.

From Single-Core Nanoparticles in Ferrofluids to Multi-Core Magnetic Nanocomposites: Assembly Strategies, Structure, and Magnetic Behavior

Iron oxide nanoparticles are the basic components of the most promising magnetoresponsive nanoparticle systems for medical (diagnosis and therapy) and bio-related applications. Multi-core iron oxide nanoparticles with a high magnetic moment and well-defined size, shape, and functional coating are designed to fulfill the specific requirements of various biomedical applications, such as contrast agents, heating mediators, drug targeting, or magnetic bioseparation. This review article summarizes recent results in manufacturing multi-core magnetic nanoparticle (MNP) systems emphasizing the synthesis procedures, starting from ferrofluids (with single-core MNPs) as primary materials in various assembly methods to obtain multi-core magnetic particles. The synthesis and functionalization will be followed by the results of advanced physicochemical, structural, and magnetic characterization of multi-core particles, as well as single- and multi-core particle size distribution, morphology, internal structure, agglomerate formation processes, and constant and variable field magnetic properties. The review provides a comprehensive insight into the controlled synthesis and advanced structural and magnetic characterization of multi-core magnetic composites envisaged for nanomedicine and biotechnology.

Chain Formation and Phase Separation in Ferrofluids: The Influence on Viscous Properties

Ferrofluids have attracted considerable interest from researchers and engineers due to their rich set of unique physical properties that are valuable for many industrial and biomedical applications. Many phenomena and features of ferrofluids' behavior are determined by internal structural transformations in the ensembles of particles, which occur due to the magnetic interaction between the particles. An applied magnetic field induces formations, such as linear chains and bulk columns, that become elongated along the field. In turn, these structures dramatically change the rheological and other physical properties of these fluids. A deep and clear understanding of the main features and laws of the transformations is necessary for the understanding and explanation of the macroscopic properties and behavior of ferrofluids. In this paper, we present an overview of experimental and theoretical works on the internal transformations in these systems, as well as on the effect of the internal structures on the rheological effects in the fluids.

On the first evidence of exchange-bias feature in magnetically contrasted consolidates made from CoFe2O4-CoO core-shell nanoparticles

Hetero-nanostructures based on magnetic contrast oxides have been prepared as highly dense nanoconsolidates. Cobalt ferrite-cobalt oxide core-shell type nanoparticles (NPs) were synthesized by seed mediated growth in polyol and subsequently consolidated by Spark Plasma Sintering (SPS) at 500 °C for a few minutes while applying a uniaxial pressure of 100 MPa. It is interesting to note that the exchange bias feature observed in the core-shell NPs is reproduced in their ceramic counterparts, or even attenuated. A systematic structural characterization was then carried out to elucidate the decrease in the exchange magnetic field, involving mainly advanced X-ray diffraction, zero-field and in-field ⁵⁷Fe Mössbauer spectrometry, magnetic measurements and electron microscopy.

Targeted magnetic separation of biomolecules and cells using earthicle-based ferrofluids

Targeting specific molecular or cell populations within single tissues or multicomponent in vitro systems is a most sought goal in biomedicine. Here we report on targeted magnetic separation of cells and biomolecules using a ferrofluid comprising superparamagnetic iron-oxide/silicate/carbon core/shell/crust nanoparticles in combination with a handheld, 2.5 cm³ NdFeB magnet (≤180 mT) and one minute exposure time. Ferrofluids were highly effective at separating (i) biomolecules, (ii) bacteria and (iii) eukaryotic cells from solutions, and they also exhibited selectivity in the separation of all three families of entities. Specifically, they were more effective at separating the negatively charged protein, albumin in the presence of the external magnetic field, but were more effective at precipitating the positively charged protein, lysozyme without the application of the external field. Because of the more effective sorption of proteins than carbohydrates on carbon and the shielding of peptidoglycans by the transmembrane proteins and hydrophilic heads of the outer membrane amphiphiles in Gram-negative bacteria, they were separated more effectively than their Gram-positive counterparts. Ferrofluids were also more efficient at separating the clinical isolate, methicillin-resistant version of S. aureus (MRSA) than its regular, lab strain and the effect is thought to be due to structural changes to the cell envelope caused by the overexpression of efflux pumps or by the higher rate of conjugation conditioning horizontal gene transfer in MRSA than in the regular, nonresistant strain. Ferrofluids also displayed a greater affinity for the cancer cells than for the normal, primary cells and allowed for targeted separation of the former after the cells were allowed to uptake the nanoparticles for 24 h. This selectivity should allow for an effective separation of cancer cells interspersed within a healthy cell population. Interaction with bacterial and eukaryotic cells was driven neither by electrostatic attraction nor chemisorption, but by weaker, van der Waals and π-interactions. Adsorption was also endothermic, irreversible for the most part, and more favorable at high concentrations, as inferred by comparison with Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms. These targeted effects are relevant for numerous fields of biomedicine and biotechnologies and require further insight for optimization and translation.

Viewing the Emphasis on State-of-the-Art Magnetic Nanoparticles: Synthesis, Physical Properties, and Applications in Cancer Theranostics

Cancer-related mortality is a leading cause of death among both men and women around the world. Target-specific therapeutic drugs, early diagnosis, and treatment are crucial to reducing the mortality rate. One of the recent trends in modern medicine is "Theranostics," a combination of therapeutics and diagnosis. Extensive interest in magnetic nanoparticles (MNPs) and ultrasmall superparamagnetic iron oxide nanoparticles (NPs) has been increasing due to their biocompatibility, superparamagnetism, less-toxicity, enhanced programmed cell death, and auto-phagocytosis on cancer cells. MNPs act as a multifunctional, noninvasive, ligand conjugated nano-imaging vehicle in targeted drug delivery and diagnosis. In this review, we primarily discuss the significance of the crystal structure, magnetic properties, and the most common method for synthesis of the smaller sized MNPs and their limitations. Next, the recent applications of MNPs in cancer therapy and theranostics are discussed, with certain preclinical and clinical experiments. The focus is on implementation and understanding of the mechanism of action of MNPs in cancer therapy through passive and active targeting drug delivery (magnetic drug targeting and targeting ligand conjugated MNPs). In addition, the theranostic application of MNPs with a dual and multimodal imaging system for early diagnosis and treatment of various cancer types including breast, cervical, glioblastoma, and lung cancer is reviewed. In the near future, the theranostic potential of MNPs with multimodality imaging techniques may enhance the acuity of personalized medicine in the diagnosis and treatment of individual patients.

Vibrational response of clusters of Fe3O4 nanoparticles patterned on glass surfaces investigated with magnetic sample modulation AFM

The vibration of Fe3O4 nanoparticles in response to an alternating magnetic field can be sensitively detected using contact mode atomic force microscopy (AFM) combined with selective modulation of magnetic domains. While imaging patterned samples of magnetic nanoparticles with contact mode AFM, a magnetic field was applied to drive sample vibration. The field altered in polarity and strength according to parameters of an AC current applied to a solenoid located under the sample. The vibration of Fe3O4 nanoparticles was detected by a nonmagnetic AFM tip to map the changes in frequency and amplitude of the vibrating sample at the level of individual Fe3O4 nanoparticles and clusters. Colloidal lithography, was used to prepare patterns of Fe3O4 nanoparticles on a glass surface using the basic steps of mixing, drying and removing the surface template of latex spheres. Monodisperse latex spheres were used to guide the deposition of magnetic nanoparticles in the spaces between the close-packed spheres of the latex film. With a mixture approach of "two-particle" lithography, 2D arrays of patterned aggregates of metal nanoparticles were generated which formed a periodic, well-defined arrangement that was suitable for subsequent characterizations with magnetic sample modulation (MSM).

Flexible Guidance of Microengines by Dynamic Topographical Pathways in Ferrofluids

In this work, we demonstrate a simple, versatile, and real-time motion guidance strategy for artificial microengines and motile microorganisms in a ferrofluid by dynamic topographical pathways (DTPs), which are assembled from superparamagnetic nanoparticles in response to external magnetic field ( H). In this general strategy, the DTPs can exert anisotropic resistance forces on autonomously moving microengines and thus regulate their orientation. As the DTPs with different directions and lengths can be reversibly and swiftly assembled in response to the applied H, the microengines in the ferrofluid can be guided on demand with controlled motion directions and trajectories, including circular, elliptical, straight-line, semi-sine, and sinusoidal trajectories. The as-demonstrated control strategy obviates reliance on the customized responses of micromotors and applies to autonomously propelling agents swimming both in bulk and near substrate walls. Furthermore, the microengines (or motile microorganisms) in a ferrofluid can be considered as an integrated system, and it may inspire the development of intelligent systems with cooperative functions for biomedical and environmental applications.

Nanoformulations for Drug Delivery: Safety, Toxicity, and Efficacy

This chapter presents an outline of the recent available information regarding safety, toxicity, and efficacy of nano drug delivery systems. Of particular importance is the evaluation of several key factors to design nontoxic and effective nanoformulations. Among them, we focus on nanostructure materials and synthesis methods, mechanisms of interactions with biological systems, treatment of nanoparticles, manufacture impurities, and nanostability. Emphasis is given to in silico, in vitro, and in vivo models used to assess and predict the toxicity of these new formulations. Additionally, some examples of in vitro and in vivo studies of specific nanoderivatives are also presented in this chapter.

Synthesis, characterization and theoretical studies on novel organic–inorganic hybrid ion–gel polymer thin films from a γ-Fe2O3 doped polyvinylpyrrolidone–N-butylpyridinium tetrafluoroborate composite via intramolecular thermal polymerization

Facile one-step synthesis and material study of novel PVP-ion gel thin film and improvement of ionic conductivity, specific conductance and charge density of it by doping high-dielectric γ-Fe₂O₃ magnetic nanoparticles is presented here.

A universal magnetic ferrofluid: Nanomagnetite stable hydrosol with no added dispersants and at neutral pH

A facile method to produce highly stable magnetite magnetic fluid at neutral pH without any stabilizing agents, resulting in pure Fe3O4 nanoparticles dispersed in water is described. The hydrosol which consists of only two components - magnetite and water - behaves as a typical ferrofluid, that is, although it responds to a magnetic field, the magnetic particles cannot be phase-separated from the water by that field. No such pure magnetic fluid have been described before, making it a universal carrier which can be easily modified for any application in materials science and chemistry, and in particular for a range of applications where non-corrosivity, low viscosity, and mild conditions are needed, such as in most bioapplications and in nano electro-mechanical systems. Under optimal conditions the hydrosol is stable for at least three months.

Application of Fe78Si9B13 amorphous particles in magnetorheological fluids

Fe₇₈Si₉B₁₃ amorphous particles with high saturation magnetization, low remanence and low coercivity are applied in preparing magnetorheological fluids.