Cell labeling with magnetic nanoparticles: opportunity for magnetic cell imaging and cell manipulation

Endocytosis: the match point of nanoparticle-based cancer therapy

Nanomedicine has inspired a ground-breaking strategy for cancer therapy. By intelligently assembling diverse moieties to form nanoparticles, numerous functionalities such as controlled release, synergistic efficiency, and in situ killing can be achieved. The emerging nanoparticles have been designed with elevated targeting efficiency as targeting cancer cells is the primary requirement for nanoparticles. However, effective targeting does not guarantee therapeutic effects as endocytosis is a prerequisite for nanoparticles to exert effects. The recent decade has witnessed the rapid development of endocytosis-oriented nanoparticles, and this review subtly analyzes, categorizes, and exemplifies these nanoparticles according to their biological internalization patterns, and the correlation between the endocytosis mechanism and the property of nanoparticles is bridged. Based on the interdisciplinary vision, the present challenges and future perspectives of nanoparticle design for successful endocytosis are discussed, highlighting the potential strategies for the future development of endocytosis-oriented nanoparticles, thus facilitating the endocytosis-oriented strategy from bench to bedside. The undeniable fact is that endocytosis-oriented nanoparticles will definitely bring new blood to the next generation of advanced cancer therapies.

Application of magnetic nanoparticles in adoptive cell therapy of cancer; training, guiding and imaging cells

Adoptive cell therapy (ACT) is on the horizon as a thrilling therapeutic plan for cancer. However, widespread application of ACT is often restricted by several challenges, including complexity of priming tumor-specific T cells and poor trafficking in solid tumors. The convergence of nanotechnology and cancer immunotherapy is coming of age and could address the limitations of ACT. Recent studies have provided evidence on the application of magnetic nanoparticles (MNPs) to generate smart immune cells and to bypass problems associated with conventional ACT. Herein, we review current progress in the application of MNPs to improve preparing, guiding and tracking immune cells in cancer ACT. Besides, we comment on the challenges ahead and strategies to optimize MNPs for clinical settings.

Formation and culture of cell spheroids by using magnetic nanostructures resembling a crown of thorns

In contrast to traditional two-dimensional cell-culture conditions, three-dimensional (3D) cell-culture models closely mimic complexin vivoconditions. However, constructing 3D cell culture models still faces challenges. In this paper, by using micro/nano fabrication method, including lithography, deposition, etching, and lift-off, we designed magnetic nanostructures resembling a crown of thorns. This magnetic crown of thorns (MCT) nanostructure enables the isolation of cells that have endocytosed magnetic particles. To assess the utility of this nanostructure, we used high-flux acquisition of Jurkat cells, an acute-leukemia cell line exhibiting the native phenotype, as an example. The novel structure enabled Jurkat cells to form spheroids within just 30 min by leveraging mild magnetic forces to bring together endocytosed magnetic particles. The size, volume, and arrangement of these spheroids were precisely regulated by the dimensions of the MCT nanostructure and the array configuration. The resulting magnetic cell clusters were uniform in size and reached saturation after 1400 s. Notably, these cell clusters could be easily separated from the MCT nanostructure through enzymatic digestion while maintaining their integrity. These clusters displayed a strong proliferation rate and survival capabilities, lasting for an impressive 96 h. Compared with existing 3D cell-culture models, the approach presented in this study offers the advantage of rapid formation of uniform spheroids that can mimicin vivomicroenvironments. These findings underscore the high potential of the MCT in cell-culture models and magnetic tissue enginerring.

Lack of cytotoxic and genotoxic effects of mPEG-silane coated iron(III) oxide nanoparticles doped with magnesium despite cellular uptake in cancerous and noncancerous lung cells

Cytotoxic and genotoxic effects of novel mPEG-silane coated iron(III) oxide nanoparticles doped with magnesium (Mg0.1-γ-Fe2O3(mPEG-silane)0.5) have been investigated on human adenocarcinomic alveolar basal epithelial (A549) and human normal bronchial epithelial (BEAS-2B) cells. In the studies several molecular and cellular targets addressing to cell membrane, cytoplasm organelles and nucleus components were served as toxicological endpoints. The as-synthesized nanoparticles were found to be stable in the cell culture media and were examined for different concentration and exposure times. No cytotoxicity of the tested nanoparticles was found although these nanoparticles slightly increased reactive oxygen species in both cell types studied. Mg0.1-γ-Fe2O3(mPEG-silane)0.5 nanoparticles did not produce any DNA strand breaks and oxidative DNA damages in A549 and BEAS-2B cells. Different concentration of Mg0.1-γ-Fe2O3(mPEG-silane)0.5 nanoparticles and different incubation time did not affect cell migration. The lung cancer cells' uptake of the nanoparticles was more effective than in normal lung cells. Altogether, the results evidence that mPEG-silane coated iron(III) oxide nanoparticles doped with magnesium do not elucidate any deleterious effects on human normal and cancerous lung cells despite cellular uptake of these nanoparticles. Therefore, it seems reasonable to conclude that these novel biocompatible nanoparticles are promising candidates for further development towards medical applications.

Modulation of calcium signaling and metabolic pathways in endothelial cells with magnetic fields

Calcium signaling plays a crucial role in various physiological processes, including muscle contraction, cell division, and neurotransmitter release. Dysregulation of calcium levels and signaling has been linked to a range of pathological conditions such as neurodegenerative disorders, cardiovascular disease, and cancer. Here, we propose a theoretical model that predicts the modulation of calcium ion channel activity and calcium signaling in the endothelium through the application of either a time-varying or static gradient magnetic field (MF). This modulation is achieved by exerting magnetic forces or torques on either biogenic or non-biogenic magnetic nanoparticles that are bound to endothelial cell membranes. Since calcium signaling in endothelial cells induces neuromodulation and influences blood flow control, treatment with a magnetic field shows promise for regulating neurovascular coupling and treating vascular dysfunctions associated with aging and neurodegenerative disorders. Furthermore, magnetic treatment can enable control over the decoding of Ca signals, ultimately impacting protein synthesis. The ability to modulate calcium wave frequencies using MFs and the MF-controlled decoding of Ca signaling present promising avenues for treating diseases characterized by calcium dysregulation.

Three-Dimensional Modeling with Osteoblast-like Cells under External Magnetic Field Conditions Using Magnetic Nano-Ferrite Particles for the Development of Cell-Derived Artificial Bone

The progress in artificial bone research is crucial for addressing fractures and bone defects in the aging population. However, challenges persist in terms of biocompatibility and structural complexity. Nanotechnology provides a promising avenue by which to overcome these challenges, with nano-ferrite particles (NFPs) exhibiting superparamagnetic properties. The ability to control cell positioning using a magnetic field opens up new possibilities for customizing artificial bones with specific shapes. This study explores the biological effects of NFPs on osteoblast-like cell lines (MC3T3-E1), including key analyses, such as cell viability, cellular uptake of NFPs, calcification processes, cell migration under external magnetic field conditions, and three-dimensional modeling. The results indicate that the impact of NFPs on cell proliferation is negligible. Fluorescence and transmission electron microscopy validated the cellular uptake of NFPs, demonstrating the potential for precise cell positioning through an external magnetic field. Under calcification-inducing conditions, the cells exhibited sustained calcification ability even in the presence of NFPs. The cell movement analysis observed the controlled movement of NFP-absorbing cells under an external magnetic field. Applying a magnetic field along the z-axis induced the three-dimensional shaping of cells incorporating NFPs, resulting in well-arranged z-axis directional patterns. In this study, NFPs demonstrated excellent biocompatibility and controllability under an external magnetic field, laying the foundation for innovative treatment strategies for customizing artificial bones.

High-throughput large scale microfluidic assembly of iron oxide nanoflowers@PS-b-PAA polymeric micelles as multimodal nanoplatforms for photothermia and magnetic imaging

Magnetic nanoparticles have been extensively explored as theranostic agents both in academic and clinical settings. Their self-assembly into nanohybrids using block copolymers can lead to new nanostructures with high functionalities and performances. Herein, we demonstrate a high-throughput and scalable method to elaborate magnetic micelles by the assembly of iron oxide magnetite nanoflowers, an efficient nanoheater, and the block copolymer Poly(styrene)-block-poly(acrylic acid) via a microfluidic-assisted nanoprecipitation method. We show that the size and shape of the magnetomicelles can be easily tuned by modulating the residence time in the microfluidic channel. In addition to their biocompatibility, we demonstrate the potential of these magnetic nanohybrids as multimodal theranostic platforms capable of generating heat by photothermia and functioning as negative contrast agents in magnetic resonance imaging and as imaging tracers in magnetic particle imaging. Notably, they outperform currently commercially available particles in terms of imaging functionalities.

Nanoparticles targeting monocytes and macrophages as diagnostic and therapeutic tools for autoimmune diseases

Autoimmune diseases are chronic conditions that result from an inadequate immune response to self-antigens and affect many people worldwide. Their signs, symptoms, and clinical severity change throughout the course of the disease, therefore the diagnosis and treatment of autoimmune diseases are major challenges. Current diagnostic tools are often invasive and tend to identify the issue at advanced stages. Moreover, the available treatments for autoimmune diseases do not typically lead to complete remission and are associated with numerous side effects upon long-term usage. A promising strategy is the use of nanoparticles that can be used as contrast agents in diagnostic imaging techniques to detect specific cells present at the inflammatory infiltrates in tissues that are not easily accessible by biopsy. In addition, NPs can be designed to deliver drugs to a cell population or tissue. Considering the significant role played by monocytes in the development of chronic inflammatory conditions and their emergence as a target for extracorporeal monitoring and precise interventions, this review focuses on recent advancements in nanoparticle-based strategies for diagnosing and treating autoimmune diseases, with a particular emphasis on targeting monocyte populations.

How can clinical safety and efficacy concerns in stem cell therapy for spinal cord injury be overcome?

INTRODUCTION

Spinal cord injury (SCI) can lead to severe neurological dysfunction. Despite scientific and medical advances, clinically effective regenerative therapies including stem cells are lacking for SCI.

AREAS COVERED

This paper discusses translational challenges related to the safe, effective use of stem cells for SCI, with a focus on mesenchymal stem cells (MSCs), neural stem cells (NSCs), Schwann cells (SCs), olfactory ensheathing cells (OECs), oligodendrocyte precursor cells (OPCs), embryonic stem cells (ESCs), and induced pluripotent stem cells (iPSCs). We discuss approaches to enhance the efficacy of cell-based strategies by i) addressing patient heterogeneity and enhancing patient selection; ii) selecting cell type, cell source, cell developmental stage, and delivery technique; iii) enhancing graft integration and mitigating immune-mediated graft rejection; and iv) ensuring availability of cells. Additionally, we review strategies to optimize outcomes including combinatorial use of rehabilitation and discuss ways to mitigate potential risks of tumor formation associated with stem cell-based strategies.

EXPERT OPINION

Basic science research will drive translational advances to develop stem cell-based therapies for SCI. Genetic, serological, and imaging biomarkers may enable individualization of cell-based treatments. Moreover, combinatorial strategies will be required to enhance graft survival, migration and functional integration, to enable precision-based intervention.

In-vivo programmable acoustic manipulation of genetically engineered bacteria

Acoustic tweezers can control target movement through the momentum interaction between an acoustic wave and an object. This technology has advantages over optical tweezers for in-vivo cell manipulation due to its high tissue penetrability and strong acoustic radiation force. However, normal cells are difficult to acoustically manipulate because of their small size and the similarity between their acoustic impedance and that of the medium. In this study, we use the heterologous expression of gene clusters to generate genetically engineered bacteria that can produce numerous sub-micron gas vesicles in the bacterial cytoplasm. We show that the presence of the gas vesicles significantly enhances the acoustic sensitivity of the engineering bacteria, which can be manipulated by ultrasound. We find that by employing phased-array-based acoustic tweezers, the engineering bacteria can be trapped into clusters and manipulated in vitro and in vivo via electronically steered acoustic beams, enabling the counter flow or on-demand flow of these bacteria in the vasculature of live mice. Furthermore, we demonstrate that the aggregation efficiency of engineering bacteria in a tumour is improved by utilizing this technology. This study provides a platform for the in-vivo manipulation of live cells, which will promote the progress of cell-based biomedical applications.

Towards Regenerative Audiology: Immune Modulation of Adipose-Derived Mesenchymal Cells Preconditioned with Citric Acid-Coated Antioxidant-Functionalized Magnetic Nanoparticles

Introduction and Background: Based on stem cells, bioactive molecules and supportive structures, regenerative medicine (RM) is promising for its potential impact on field of hearing loss by offering innovative solutions for hair cell rescue. Nanotechnology has recently been regarded as a powerful tool for accelerating the efficiency of RM therapeutic solutions. Adipose-derived mesenchymal cells (ADSCs) have already been tested in clinical trials for their regenerative and immunomodulatory potential in various medical fields; however, the advancement to bedside treatment has proven to be tedious. Innovative solutions are expected to circumvent regulatory and manufacturing issues related to living cell-based therapies. The objectives of the study were to test if human primary ADSCs preconditioned with magnetic nanoparticles coated with citric acid and functionalized with antioxidant protocatechuic acid (MNP-CA-PCA) retain their phenotypic features and if conditioned media elicit immune responses in vitro. MNP-CA-PCA was synthesized and characterized regarding size, colloidal stability as well as antioxidant release profile. Human primary ADSCs preconditioned with MNP-CA-PCA were tested for viability, surface marker expression and mesenchymal lineage differentiation potential. Conditioned media (CM) from ADSCs treated with MNP-CA-PCA were tested for Il-6 and IL-8 cytokine release using ELISA and inhibition of lectin-stimulated peripheral blood monocyte proliferation. Results: MNP-CA-PCA-preconditioned ADSCs display good viability and retain their specific mesenchymal stem cell phenotype. CM from ADSCs conditioned with MNP-CA-PCA do not display increased inflammatory cytokine release and do not induce proliferation of allergen-stimulated allogeneic peripheral blood monocytes in vitro. Conclusions: While further in vitro and in vivo tests are needed to validate these findings, the present results indicated that CM from ADSCs preconditioned with MNP-CA-PCA could be developed as possible cell-free therapies for rescuing auditory hair cells.

Towards Regenerative Audiology: Immune Modulation of Adipose-Derived Mesenchymal Cells Preconditioned with Citric Acid-Coated Antioxidant-Functionalized Magnetic Nanoparticles

Introduction and Background: Based on stem cells, bioactive molecules and supportive structures, regenerative medicine (RM) is promising for its potential impact on field of hearing loss by offering innovative solutions for hair cell rescue. Nanotechnology has recently been regarded as a powerful tool for accelerating the efficiency of RM therapeutic solutions. Adipose-derived mesenchymal cells (ADSCs) have already been tested in clinical trials for their regenerative and immunomodulatory potential in various medical fields; however, the advancement to bedside treatment has proven to be tedious. Innovative solutions are expected to circumvent regulatory and manufacturing issues related to living cell-based therapies. The objectives of the study were to test if human primary ADSCs preconditioned with magnetic nanoparticles coated with citric acid and functionalized with antioxidant protocatechuic acid (MNP-CA-PCA) retain their phenotypic features and if conditioned media elicit immune responses in vitro. MNP-CA-PCA was synthesized and characterized regarding size, colloidal stability as well as antioxidant release profile. Human primary ADSCs preconditioned with MNP-CA-PCA were tested for viability, surface marker expression and mesenchymal lineage differentiation potential. Conditioned media (CM) from ADSCs treated with MNP-CA-PCA were tested for Il-6 and IL-8 cytokine release using ELISA and inhibition of lectin-stimulated peripheral blood monocyte proliferation. Results: MNP-CA-PCA-preconditioned ADSCs display good viability and retain their specific mesenchymal stem cell phenotype. CM from ADSCs conditioned with MNP-CA-PCA do not display increased inflammatory cytokine release and do not induce proliferation of allergen-stimulated allogeneic peripheral blood monocytes in vitro. Conclusions: While further in vitro and in vivo tests are needed to validate these findings, the present results indicated that CM from ADSCs preconditioned with MNP-CA-PCA could be developed as possible cell-free therapies for rescuing auditory hair cells.

Biodegradable Biopolymeric Nanoparticles for Biomedical Applications-Challenges and Future Outlook

Biopolymers are polymers obtained from either renewable or non-renewable sources and are the most suitable candidate for tailor-made nanoparticles owing to their biocompatibility, biodegradability, low toxicity and immunogenicity. Biopolymeric nanoparticles (BPn) can be classified as natural (polysaccharide and protein based) and synthetic on the basis of their origin. They have been gaining wide interest in biomedical applications such as tissue engineering, drug delivery, imaging and cancer therapy. BPn can be synthesized by various fabrication strategies such as emulsification, ionic gelation, nanoprecipitation, electrospray drying and so on. The main aim of the review is to understand the use of nanoparticles obtained from biodegradable biopolymers for various biomedical applications. There are very few reviews highlighting biopolymeric nanoparticles employed for medical applications; this review is an attempt to explore the possibilities of using these materials for various biomedical applications. This review highlights protein based (albumin, gelatin, collagen, silk fibroin); polysaccharide based (chitosan, starch, alginate, dextran) and synthetic (Poly lactic acid, Poly vinyl alcohol, Poly caprolactone) BPn that has recently been used in many applications. The fabrication strategies of different BPn are also being highlighted. The future perspective and the challenges faced in employing biopolymeric nanoparticles are also reviewed.

Engineered Macrophages: A Safe-by-Design Approach for the Tumor Targeting Delivery of Sub-5 nm Gold Nanoparticles

Ultrasmall nanoparticles (NPs) are a promising platform for the diagnosis and therapy of cancer, but the particles in sizes as small as several nanometers have an ability to translocate across biological barriers, which may bring unpredictable health risks. Therefore, it is essential to develop workable cell-based tools that can deliver ultrasmall NPs to the tumor in a safer manner. Here, this work uses macrophages as a shuttle to deliver sub-5 nm PEGylated gold (Au) NPs to tumors actively or passively, while reducing the accumulation of Au NPs in the brain. This work demonstrates that sub-5 nm Au NPs can be rapidly exocytosed from live macrophages, reaching 45.6% within 24 h, resulting in a labile Au NP-macrophage system that may release free Au NPs into the blood circulation in vivo. To overcome this shortcoming, two straightforward methods are used to engineer macrophages to obtain "half-dead" and "dead" macrophages. Although the efficiency of engineered macrophages for delivering sub-5 nm Au NPs to tumors is 2.2-3.8% lower than that of free Au NPs via the passive enhanced permeability and retention effect, this safe-by-design approach can dramatically reduce the accumulation of Au NPs in the brain by more than one order of magnitude. These promising approaches offer an opportunity to expand the immune cell- or stem cell-mediated delivery of ultrasmall NPs for the diagnosis and therapy of diseases in a safer way in the future.

c-Met-Targeting 19F MRI Nanoparticles with Ultralong Tumor Retention for Precisely Detecting Small or Ill-Defined Colorectal Liver Metastases

Purpose

Precisely detecting colorectal liver metastases (CLMs), the leading cause of colorectal cancer-associated mortality, is extremely important. ¹H MRI with high soft tissue resolution plays a key role in the diagnosing liver lesions; however, precise detecting CLMs by ¹H MRI is a great challenge due to the limited sensitivity. Even though contrast agents may improve the sensitivity, due to their short half-life, repeated injections are required to monitor the changes of CLMs. Herein, we synthesized c-Met-targeting peptide-functionalized perfluoro-15-crown-5-ether nanoparticles (AH111972-PFCE NPs), for highly sensitive and early diagnosis of small CLMs.

Methods

The size, morphology and optimal properties of the AH111972-PFCE NPs were characterized. c-Met specificity of the AH111972-PFCE NPs was validated by in vitro experiment and in vivo ¹⁹F MRI study in the subcutaneous tumor murine model. The molecular imaging practicability and long tumor retention of the AH111972-PFCE NPs were evaluated in the liver metastases mouse model. The biocompatibility of the AH111972-PFCE NPs was assessed by toxicity study.

Results

AH111972-PFCE NPs with regular shape have particle size of 89.3 ± 17.8 nm. The AH111972-PFCE NPs exhibit high specificity, strong c-Met-targeting ability, and precise detection capability of CLMs, especially small or ill-defined fused metastases in ¹H MRI. Moreover, AH111972-PFCE NPs could be ultralong retained in metastatic liver tumors for at least 7 days, which is conductive to the implementation of continuous therapeutic efficacy monitoring. The NPs with minimal side effects and good biocompatibility are cleared mainly via the spleen and liver.

Conclusion

The c-Met targeting and ultralong tumor retention of AH111972-PFCE NPs will contribute to increasing therapeutic agent accumulation in metastatic sites, laying a foundation for CLMs diagnosis and further c-Met targeted treatment integration. This work provides a promising nanoplatform for the future clinical application to patients with CLMs.

Use of metal-based contrast agents for in vivo MR and CT imaging of phagocytic cells in neurological pathologies

The activation of phagocytic cells is a hallmark of many neurological diseases. Imaging them in their 3-dimensional cerebral environment over time is crucial to better understand their role in disease pathogenesis and to monitor their potential therapeutic effects. Phagocytic cells have the ability to internalize metal-based contrast agents both in vitro and in vivo and can thus be tracked by magnetic resonance imaging (MRI) or computed tomography (CT). In this review article, we summarize the different labelling strategies, contrast agents, and in vivo imaging modalities that can be used to monitor cells with phagocytic activity in the central nervous system using MRI and CT, with a focus on clinical applications. Metal-based nanoparticle contrast agents such as gadolinium, gold and iron are ideal candidates for these applications as they have favourable magnetic and/or radiopaque properties and can be fine-tuned for optimal uptake by phagocytic cells. However, they also come with downsides due to their potential toxicity, especially in the brain where they might accumulate. We therefore conclude our review by discussing the pitfalls, safety and potential for clinical translation of these metal-based neuroimaging techniques. Early results in patients with neuropathologies such as multiple sclerosis, stroke, trauma, cerebral aneurysm and glioblastoma are promising. If the challenges represented by safety issues are overcome, phagocytic cells imaging will be a very valuable tool for studying and understanding the inflammatory response and evaluating treatments that aim at mitigating this response in patients with neurological diseases.

Nanomaterials against intracellular bacterial infection: from drug delivery to intrinsic biofunction

Fighting intracellular bacteria with strong antibiotics evading remains a long-standing challenge. Responding to and regulating the infectious microenvironment is crucial for treating intracellular infections. Sophisticated nanomaterials with unique physicochemical properties exhibit great potential for precise drug delivery towards infection sites, along with modulating infectious microenvironment via their instinct bioactivity. In this review, we first identify the key characters and therapeutic targets of intracellular infection microenvironment. Next, we illustrate how the nanomaterials physicochemical properties, such as size, charge, shape and functionalization affect the interaction between nanomaterials, cells and bacteria. We also introduce the recent progress of nanomaterial-based targeted delivery and controlled release of antibiotics in intracellular infection microenvironment. Notably, we highlight the nanomaterials with unique intrinsic properties, such as metal toxicity and enzyme-like activity for the treatment of intracellular bacteria. Finally, we discuss the opportunities and challenges of bioactive nanomaterials in addressing intracellular infections.

Comparative heating efficiency and cytotoxicity of magnetic silica nanoparticles for magnetic hyperthermia treatment on human breast cancer cells

Magnetic hyperthermia (MHT) is a promising treatment for a variety of cancers due to its ability to increase the sensitivity of cells to other treatments, such as chemotherapy. Superparamagnetic nanoparticles (MNPs) were used for MHT treatment due to their heat generation ability under an AC magnetic field (AMF). In this study, iron oxide and zinc-doped iron oxide MNPs were produced and modified with silica to obtain eleven different types (MSNP-I to -XI) of magnetic silica nanoparticles (MSNPs). The MSNPs which show the highest heating capacity were selected to investigate their MHT ability on non-tumourigenic MCF-10A and tumourigenic MCF-7 cell lines. The cytotoxicity results indicated that the size, the content of the magnetic core and silica coating thickness were important in the heating capacity of MSNPs under AMF. After MHT treatment, selected MSNPs showed limited cytotoxicity on MCF-10A, but significant cell death on MCF-7.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03377-y.

Tools for manipulation and positioning of microtissues

Complex three-dimensional (3D) in vitro models are emerging as a key technology to support research areas in personalised medicine, such as drug development and regenerative medicine. Tools for manipulation and positioning of microtissues play a crucial role in the microtissue life cycle from production to end-point analysis. The ability to precisely locate microtissues can improve the efficiency and reliability of processes and investigations by reducing experimental time and by providing more controlled parameters. To achieve this goal, standardisation of the techniques is of primary importance. Compared to microtissue production, the field of microtissue manipulation and positioning is still in its infancy but is gaining increasing attention in the last few years. Techniques to position microtissues have been classified into four main categories: hydrodynamic techniques, bioprinting, substrate modification, and non-contact active forces. In this paper, we provide a comprehensive review of the different tools for the manipulation and positioning of microtissues that have been reported to date. The working mechanism of each technique is described, and its merits and limitations are discussed. We conclude by evaluating the potential of the different approaches to support progress in personalised medicine.

Cell Tracking by Magnetic Particle Imaging: Methodology for Labeling THP-1 Monocytes with Magnetic Nanoparticles for Cellular Imaging

Magnetic particle imaging (MPI) is a noninvasive tomographic imaging modality for the quantitative visualization of magnetic nanoparticles (MNPs) with high temporal and spatial resolution. The general capability of MPI for cell tracking (e.g., monitoring living cells labeled with MNPs) has successfully been shown. MNPs in cell culture media are often subjected to structural and magnetic changes. In addition to the deteriorating reproducibility, this also complicates the systematic study of the relationship between the MNP properties and their cellular uptake for MPI. Here, we present a method for the preparation of magnetically labeled THP-1 (Tamm-Horsfall Protein-1) monocytes that are used in MPI cell tracking. The method development was performed using two different MPI tracers, which exhibited electrostatic and steric stabilizations, respectively. In the first step, the interaction between the MNPs and cell culture media was investigated and adjusted to ensure high structural and magnetic stability. Furthermore, the influences of the incubation time, MNP concentration used for cellular uptake, and individual preparation steps (e.g., the washing of cells) were systematically investigated. Finally, the success of the developed loading method was demonstrated by the MPI measurements. The presented systematic investigation of the factors that influence the MNP loading of cells will help to develop a reliable and reproducible method for MPI monocyte tracking for the early detection of inflammation in the future.

Effect of Oleylamine on the Surface Chemistry, Morphology, Electronic Structure, and Magnetic Properties of Cobalt Ferrite Nanoparticles

The influence of oleylamine (OLA) concentration on the crystallography, morphology, surface chemistry, chemical bonding, and magnetic properties of solvothermal synthesized CoFe₂O₄ (CFO) nanoparticles (NPs) has been thoroughly investigated. Varying OLA concentration (0.01-0.1 M) resulted in the formation of cubic spinel-structured CoFe₂O₄ NPs in the size-range of 20-14 (±1) nm. The Fourier transform spectroscopic analyses performed confirmed the OLA binding to the CFO NPs. The thermogravimetric measurements revealed monolayer and multilayer coating of OLA on CFO NPs, which were further supported by the small-angle X-ray scattering measurements. The magnetic measurements indicated that the maximum saturation (M_S) and remanent (M_r) magnetization decreased with increasing OLA concentration. The ratio of maximum dipolar field (H_dip), coercivity (H_C), and exchanged bias field (H_ex) (at 10 K) to the average crystallite size (D_xrd), i.e., (H_dip/D_xrd), (H_C/D_xrd), and (H_ex/D_xrd), increased linearly with OLA concentration, indicating that OLA concurrently controls the particle size and interparticle interaction among the CFO NPs. The results and analyses demonstrate that the OLA-mediated synthesis allowed for modification of the structural and magnetic properties of CFO NPs, which could readily find potential application in electronics and biomedicine.

Hope for bone regeneration: The versatility of iron oxide nanoparticles

Although bone tissue has the ability to heal itself, beyond a certain point, bone defects cannot rebuild themselves, and the challenge is how to promote bone tissue regeneration. Iron oxide nanoparticles (IONPs) are a magnetic material because of their excellent properties, which enable them to play an active role in bone regeneration. This paper reviews the application of IONPs in bone tissue regeneration in recent years, and outlines the mechanisms of IONPs in bone tissue regeneration in detail based on the physicochemical properties, structural characteristics and safety of IONPs. In addition, a bibliometric approach has been used to analyze the hot spots and trends in the field in order to identify future directions. The results demonstrate that IONPs are increasingly being investigated in bone regeneration, from the initial use as magnetic resonance imaging (MRI) contrast agents to later drug delivery vehicles, cell labeling, and now in combination with stem cells (SCs) composite scaffolds. In conclusion, based on the current research and development trends, it is more inclined to be used in bone tissue engineering, scaffolds, and composite scaffolds.

Simultaneous Multiplexed Imaging of Biomolecules in Transgenic Mouse Brain Tissues Using Mass Spectrometry Imaging: A Multi-omic Approach

The importance of multi-omic-based approaches to better understand diverse pathological mechanisms including neurodegenerative diseases has emerged. Spatial information can be of great help in understanding how biomolecules interact pathologically and in elucidating target biomarkers for developing therapeutics. While various analytical methods have been attempted for imaging-based biomolecule analysis, a multi-omic approach to imaging remains challenging due to the different characteristics of biomolecules. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a powerful tool due to its sensitivity, chemical specificity, and high spatial resolution in visualizing chemical information in cells and tissues. In this paper, we suggest a new strategy to simultaneously obtain the spatial information of various kinds of biomolecules that includes both labeled and label-free approaches using ToF-SIMS. The enzyme-assisted labeling strategy for the targets of interest enables the sensitive and specific imaging of large molecules such as peptides, proteins, and mRNA, a task that has been, to date, difficult for any MS analysis. Together with the strength of the analytical performance of ToF-SIMS in the label-free tissue imaging of small biomolecules, the proposed strategy allows one to simultaneously obtain integrated information of spatial distribution of metabolites, lipids, peptides, proteins, and mRNA at a high resolution in a single measurement. As part of the suggested strategy, we present a sample preparation method suitable for MS imaging. Because a comprehensive method to examine the spatial distribution of multiple biomolecules in tissues has remained elusive, our strategy can be a useful tool to support the understanding of the interactions of biomolecules in tissues as well as pathological mechanisms.

Micro/Nanosystems for Magnetic Targeted Delivery of Bioagents

Targeted delivery of pharmaceuticals is promising for efficient disease treatment and reduction in adverse effects. Nano or microstructured magnetic materials with strong magnetic momentum can be noninvasively controlled via magnetic forces within living beings. These magnetic carriers open perspectives in controlling the delivery of different types of bioagents in humans, including small molecules, nucleic acids, and cells. In the present review, we describe different types of magnetic carriers that can serve as drug delivery platforms, and we show different ways to apply them to magnetic targeted delivery of bioagents. We discuss the magnetic guidance of nano/microsystems or labeled cells upon injection into the systemic circulation or in the tissue; we then highlight emergent applications in tissue engineering, and finally, we show how magnetic targeting can integrate with imaging technologies that serve to assist drug delivery.

SPIONs mediated magnetic actuation promotes nerve regeneration by inducing and maintaining repair-supportive phenotypes in Schwann cells

Background

Schwann cells, the glial cells in the peripheral nervous system, are highly plastic. In response to nerve injury, Schwann cells are reprogrammed to a series of specialized repair-promoting phenotypes, known as repair Schwann cells, which play a pivotal role in nerve regeneration. However, repair Schwann cells represent a transient and unstable cell state, and these cells progressively lose their repair phenotypes and repair‐supportive capacity; the transience of this state is one of the key reasons for regeneration failure in humans. Therefore, the ability to control the phenotypic stability of repair Schwann cells is of great practical importance as well as biological interest.

Results

We designed and prepared a type of fluorescent–magnetic bifunctional superparamagnetic iron oxide nanoparticles (SPIONs). In the present study, we established rat sciatic nerve injury models, then applied SPIONs to Schwann cells and established an effective SPION-mediated magnetic actuation system targeting the sciatic nerves. Our results demonstrate that magnetic actuation mediated by SPIONs can induce and maintain repair-supportive phenotypes of Schwann cells, thereby promoting regeneration and functional recovery of the sciatic nerve after crush injury.

Conclusions

Our research indicate that Schwann cells can sense these external, magnetically driven mechanical forces and transduce them to intracellular biochemical signals that promote nerve regeneration by inducing and maintaining the repair phenotypes of Schwann cells. We hope that this study will provide a new therapeutic strategy to promote the regeneration and repair of injured peripheral nerves.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01337-5.

Droplet Manipulation under a Magnetic Field: A Review

The magnetic manipulation of droplets is one of the emerging magnetofluidic technologies that integrate multiple disciplines, such as electromagnetics, fluid mechanics and so on. The directly driven droplets are mainly composed of ferrofluid or liquid metal. This kind of magnetically induced droplet manipulation provides a remote, wireless and programmable approach beneficial for research and engineering applications, such as drug synthesis, biochemistry, sample preparation in life sciences, biomedicine, tissue engineering, etc. Based on the significant growth in the study of magneto droplet handling achieved over the past decades, further and more profound explorations in this field gained impetus, raising concentrations on the construction of a comprehensive working mechanism and the commercialization of this technology. Current challenges faced are not limited to the design and fabrication of the magnetic field, the material, the acquisition of precise and stable droplet performance, other constraints in processing speed and so on. The rotational devices or systems could give rise to additional issues on bulky appearance, high cost, low reliability, etc. Various magnetically introduced droplet behaviors, such as deformation, displacement, rotation, levitation, splitting and fusion, are mainly introduced in this work, involving the basic theory, functions and working principles.

Tumor models to assess immune response and tumor-microbiome interactions in colorectal cancer

Despite significant advances over the past 2 decades in preventive screening and therapy aimed at improving patient survival, colorectal cancer (CRC) remains the second most common cause of cancer death in the United States. The average 5-year survival rate of CRC patients with positive regional lymph nodes is only 40%, while less than 5% of patients with distant metastases survive beyond 5 years. There is a critical need to develop novel therapies that can improve overall survival in patients with poor prognoses, particularly since 60% of them are diagnosed at an advanced stage. Pertinently, immune checkpoint blockade therapy has dramatically changed how we treat CRC patients with microsatellite-instable high tumors. Furthermore, accumulating evidence shows that changes in gut microbiota are associated with the regulation of host antitumor immune response and cancer progression. Appropriate animal models are essential to deciphering the complex mechanisms of host antitumor immune response and tumor-gut microbiome metabolic interactions. Here, we discuss various mouse models of colorectal cancer that are developed to address key questions on tumor immune response and tumor-microbiota interactions. These CRC models will also serve as resourceful tools for effective preclinical studies.

Highly aminated iron oxide nanoworms for simultaneous manufacturing and labeling of chimeric antigen receptor T cells

Cell based therapies including chimeric antigen receptor (CAR) T cells are promising for treating leukemias and solid cancers. At the same time, there is interest in enhancing the functionality of these cells via surface decoration with nanoparticles (backpacking). Magnetic nanoparticle cell labeling is of particular interest due to opportunities for magnetic separation, in vivo manipulation, drug delivery and magnetic resonance imaging (MRI). While modification of T cells with magnetic nanoparticles (MNPs) was explored before, we questioned whether MNPs are compatible with CAR-T cells when introduced during the manufacturing process. We chose highly aminated 120 nm crosslinked iron oxide nanoworms (CLIO NWs, ~36,000 amines per NW) that could efficiently label different adherent cell lines and we used CD123 CAR-T cells as the labeling model. The CD123 CAR-T cells were produced in the presence of CLIO NWs, CLIO NWs plus protamine sulfate (PS), or PS only. The transduction efficiency of lentiviral CD123 CAR with only NWs was ~23% lower than NW+PS and PS groups (~33% and 35%, respectively). The cell viability from these three transduction conditions was not reduced within CAR-T cell groups, though lower compared to non-transduced T cells (mock T). Use of CLIO NWs instead of, or together with cationic protamine sulfate for enhancement of lentiviral transduction resulted in comparable levels of CAR expression and viability but decreased the proportion of CD8+ cells and increased the proportion of CD4+ cells. CD123 CAR-T transduced in the presence of CLIO NWs, CLIO NWs plus PS, or PS only, showed similar level of cytotoxicity against leukemic cell lines. Furthermore, fluorescence microscopy imaging demonstrated that CD123 CAR-T cells labeled with CLIO NW formed rosettes with CD123+ leukemic cells as the non-labeled CAR-T cells, indicating that the CAR-T targeting to tumor cells has maintained after CLIO NW labeling. The in vivo trafficking of the NW labeled CAR-T cells showed the accumulation of CAR-T labeled with NWs primarily in the bone marrow and spleen. CAR-T cells can be magnetically labeled during their production while maintaining functionality using the positively charged iron oxide NWs, which enable the in vivo biodistribution and tracking of CAR-T cells.

Droplet-based microfluidics in biomedical applications

Droplet-based microfluidic systems have been employed to manipulate discrete fluid volumes with immiscible phases. Creating the fluid droplets at microscale has led to a paradigm shift in mixing, sorting, encapsulation, sensing, and designing high throughput devices for biomedical applications. Droplet microfluidics has opened many opportunities in microparticle synthesis, molecular detection, diagnostics, drug delivery, and cell biology. In the present review, we first introduce standard methods for droplet generation (i.e., passive and active methods) and discuss the latest examples of emulsification and particle synthesis approaches enabled by microfluidic platforms. Then, the applications of droplet-based microfluidics in different biomedical applications are detailed. Finally, a general overview of the latest trends along with the perspectives and future potentials in the field are provided.

Effects of DC Magnetic Fields on Magnetoliposomes

The potential use of magnetic nanoparticles (MNPs) in biomedicine as magnetic resonance, drug delivery, imagenology, hyperthermia, biosensors, and biological separation has been studied in different laboratories. One of the challenges on MNP elaboration for biological applications is the size, biocompatibility, heat efficiency, stabilization in physiological conditions, and surface coating. Magnetoliposome (ML), a lipid bilayer of phospholipids encapsulating MNPs, is a system used to reduce toxicity. Encapsulated MNPs can be used as a potential drug and a gene delivery system, and in the presence of magnetic fields, MLs can be accumulated in a target tissue by a strong gradient magnetic field. Here, we present a study of the effects of DC magnetic fields on encapsulated MNPs inside liposomes. Despite their widespread applications in biotechnology and environmental, biomedical, and materials science, the effects of magnetic fields on MLs are unclear. We use a modified coprecipitation method to synthesize superparamagnetic nanoparticles (SNPs) in aqueous solutions. The SNPs are encapsulated inside phospholipid liposomes to study the interaction between phospholipids and SNPs. Material characterization of SNPs reveals round-shaped nanoparticles with an average size of 12 nm, mainly magnetite. MLs were prepared by the rehydration method. After formation, we found two types of MLs: one type is tense with SNPs encapsulated and the other is a floppy vesicle that does not show the presence of SNPs. To study the response of MLs to an applied DC magnetic field, we used a homemade chamber. Digitalized images show encapsulated SNPs assembled in chain formation when a DC magnetic field is applied. When the magnetic field is switched off, it completely disperses SNPs. Floppy MLs deform along the direction of the external applied magnetic field. Solving the relevant magnetostatic equations, we present a theoretical model to explain the ML deformations by analyzing the forces exerted by the magnetic field over the surface of the spheroidal liposome. Tangential magnetic forces acting on the ML surface result in a press force deforming MLs. The type of deformations will depend on the magnetic properties of the mediums inside and outside the MLs. The model predicts a coexistence region of oblate-prolate deformation in the zone where χ = 1. We can understand the chain formation in terms of a dipole-dipole interaction of SNP.

Citrate-Coated Superparamagnetic Iron Oxide Nanoparticles Enable a Stable Non-Spilling Loading of T Cells and Their Magnetic Accumulation

T cell infiltration into a tumor is associated with a good clinical prognosis of the patient and adoptive T cell therapy can increase anti-tumor immune responses. However, immune cells are often excluded from tumor infiltration and can lack activation due to the immune-suppressive tumor microenvironment. To make T cells controllable by external forces, we loaded primary human CD3+ T cells with citrate-coated superparamagnetic iron oxide nanoparticles (SPIONs). Since the efficacy of magnetic targeting depends on the amount of SPION loading, we investigated how experimental conditions influence nanoparticle uptake and viability of cells. We found that loading in the presence of serum improved both the colloidal stability of SPIONs and viability of T cells, whereas stimulation with CD3/CD28/CD2 and IL-2 did not influence nanoparticle uptake. Furthermore, SPION loading did not impair cytokine secretion after polyclonal stimulation. We finally achieved 1.4 pg iron loading per cell, which was both located intracellularly in vesicles and bound to the plasma membrane. Importantly, nanoparticles did not spill over to non-loaded cells. Since SPION-loading enabled efficient magnetic accumulation of T cells in vitro under dynamic conditions, we conclude that this might be a good starting point for the investigation of in vivo delivery of immune cells.

Multiparametric biophysical profiling of red blood cells in malaria infection

Biophysical separation promises label-free, less-invasive methods to manipulate the diverse properties of live cells, such as density, magnetic susceptibility, and morphological characteristics. However, some cellular changes are so minute that they are undetectable by current methods. We developed a multiparametric cell-separation approach to profile cells with simultaneously changing density and magnetic susceptibility. We demonstrated this approach with the natural biophysical phenomenon of Plasmodium falciparum infection, which modifies its host erythrocyte by simultaneously decreasing density and increasing magnetic susceptibility. Current approaches have used these properties separately to isolate later-stage infected cells, but not in combination. We present biophysical separation of infected erythrocytes by balancing gravitational and magnetic forces to differentiate infected cell stages, including early stages for the first time, using magnetic levitation. We quantified height distributions of erythrocyte populations-27 ring-stage synchronized samples and 35 uninfected controls-and quantified their unique biophysical signatures. This platform can thus enable multidimensional biophysical measurements on unique cell types.

Tracking adoptive T cell immunotherapy using magnetic particle imaging

Adoptive cellular therapy (ACT) is a potent strategy to boost the immune response against cancer. ACT is effective against blood cancers but faces challenges in treating solid tumors. A critical step for the success of ACT immunotherapy is to achieve efficient trafficking and persistence of T cells to solid tumors. Non-invasive tracking of the accumulation of adoptively transferred T cells to tumors would greatly accelerate development of more effective ACT strategies. We demonstrate the use of magnetic particle imaging (MPI) to non-invasively track ACT T cells in vivo in a mouse model of brain cancer. Magnetic labeling did not impair primary tumor-specific T cells in vitro, and MPI allowed the detection of labeled T cells in the brain after intravenous or intracerebroventricular administration. These results support the use of MPI to track adoptively transferred T cells and accelerate the development of ACT treatments for brain tumors and other cancers.

Recent Advancements of Specific Functionalized Surfaces of Magnetic Nano- and Microparticles as a Theranostics Source in Biomedicine

Magnetic nano- and microparticles (MNMPs) belong to a highly versatile class of colloids with actuator and sensor properties that have been broadly studied for their application in theranostics such as molecular imaging and drug delivery. The use of advanced biocompatible, biodegradable polymers and polyelectrolytes as MNMP coating materials is essential to ensure the stability of MNMPs and enable efficient drug release while at the same time preventing cytotoxic effects. In the past years, huge progress has been made in terms of the design of MNMPs. Especially, the understanding of coating formation with respect to control of drug loading and release kinetics on the molecular level has significantly advanced. In this review, recent advancements in the field of MNMP surface engineering and the applicability of MNMPs in research fields of medical imaging, diagnosis, and nanotherapeutics are presented and discussed. Furthermore, in this review the main emphasis is put on the manipulation of biological specimens and cell trafficking, for which MNMPs represent a favorable tool enabling transport processes of drugs through cell membranes. Finally, challenges and future perspectives for applications of MNMPs as theranostic nanomaterials are discussed.

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.

Improving Tumor Retention of Effector Cells in Adoptive Cell Transfer Therapies by Magnetic Targeting

Adoptive cell transfer therapy is a promising anti-tumor immunotherapy in which effector immune cells are transferred to patients to treat tumors. However, one of its main limitations is the inefficient trafficking of inoculated effector cells to the tumor site and the small percentage of effector cells that remain activated when reaching the tumor. Multiple strategies have been attempted to improve the entry of effector cells into the tumor environment, often based on tumor types. It would be, however, interesting to develop a more general approach, to improve and facilitate the migration of specific activated effector lymphoid cells to any tumor type. We and others have recently demonstrated the potential for adoptive cell transfer therapy of the combined use of magnetic nanoparticle-loaded lymphoid effector cells together with the application of an external magnetic field to promote the accumulation and retention of lymphoid cells in specific body locations. The aim of this review is to summarize and highlight the recent findings in the field of magnetic accumulation and retention of effector cells in tumors after adoptive transfer, and to discuss the possibility of using this approach for tumor targeting with chimeric antigen receptor (CAR) T-cells.

Nanoscale magnetic imaging enabled by nitrogen vacancy centres in nanodiamonds labelled by iron-oxide nanoparticles

Nanodiamonds containing the nitrogen vacancy centre (NV) have a significant role in biosensing, bioimaging, drug delivery, and as biomarkers in fluorescence imaging, due to their photo-stability and biocompatibility. The optical read out of the NV unpaired electron spin has been used in diamond magnetometry to image living cells and magnetically labelled cells. Diamond magnetometry is mostly based on the use of bulk diamond with a large concentration of NV centres in a wide field fluorescence microscope equipped with microwave excitation. It is possible to correlate the fluorescence maps with the magnetic field maps of magnetically labelled cells with diffraction limit resolution. Nanodiamonds have not as yet been implemented to image magnetic fields within complex biological systems at the nanometre scale. Here we demonstrate the suitability of nanodiamonds to correlate the fluorescence map with the magnetic imaging map of magnetically labelled cells. Nanoscale optical images with 17 nm resolution of nanodiamonds labelling fixed cells bound to iron oxide magnetic nanoparticles are demonstrated by using a single molecule localisation microscope. Nanoscale magnetic field images of the magnetised magnetic nanoparticles spatially assigned to individual cells are superresolved by the NV centres within nanodiamonds conjugated with the magnetic nanoparticles with 20 nm resolutions. Our method offers a new platform for the super-resolution of optical magnetic imaging in biological samples conjugated with nanodiamonds and iron-oxide magnetic nanoparticles.

The effect of magnetic field exposure on differentiation of magnetite nanoparticle-loaded adipose-derived stem cells

Magnetic nanoparticles (MNPs) are versatile tools for various applications in biotechnology and nanomedicine. MNPs-mediated cell tracking, targeting and imaging are increasingly studied for regenerative medicine applications in cell therapy and tissue engineering. Mechanical stimulation influences mesenchymal stem cell differentiation. Here we show that MNPs-mediated magneto-mechanical stimulation of human primary adipose derived stem cells (ADSCs) exposed to variable magnetic field (MF) influences their adipogenic and osteogenic differentiation. ADSCs loaded with biocompatible magnetite nanoparticles of 6.6 nm, and with an average load of 21 picograms iron/cell were exposed to variable low intensity (0.5 mT - LMF) and higher intensity magnetic fields (14.7 and 21.6 mT - HMF). Type, duration, intensity and frequency of MF differently affect differentiation. Short time (2 days) intermittent exposure to LMF increases adipogenesis while longer (7 days) intermittent as well as continuous exposure favors osteogenesis. HMF (21.6 mT) short time intermittent exposure favors osteogenesis. Different exposure protocols can be used to increase differentiation dependently on expected results. Magnetic remotely-actuated MNPs up-taken by ADSCs promotes the shift towards osteoblastic lineage. ADSCs-MNPs under MF exposure could be used for enabling osteoblastic conversion during cell therapy for systemic osteoporosis. Current results enable further in vivo studies investigating the role of remotely-controlled magnetically actuated ADSCs-MNPs for the treatment of osteoporosis.

Magnetic Nanoparticles for Nanomedicine

The field of nanomedicine has recently emerged as a product of the expansion of a range of nanotechnologies into biomedical science, pharmacology and clinical practice. Due to the unique properties of nanoparticles and the related nanostructures, their applications to medical diagnostics, imaging, controlled drug and gene delivery, monitoring of therapeutic outcomes, and aiding in medical interventions, provide a new perspective for challenging problems in such demanding issues as those involved in the treatment of cancer or debilitating neurological diseases. In this review, we evaluate the role and contributions that the applications of magnetic nanoparticles (MNPs) have made to various aspects of nanomedicine, including the newest magnetic particle imaging (MPI) technology allowing for outstanding spatial and temporal resolution that enables targeted contrast enhancement and real-time assistance during medical interventions. We also evaluate the applications of MNPs to the development of targeted drug delivery systems with magnetic field guidance/focusing and controlled drug release that mitigate chemotherapeutic drugs’ side effects and damage to healthy cells. These systems enable tackling of multiple drug resistance which develops in cancer cells during chemotherapeutic treatment. Furthermore, the progress in development of ROS- and heat-generating magnetic nanocarriers and magneto-mechanical cancer cell destruction, induced by an external magnetic field, is also discussed. The crucial roles of MNPs in the development of biosensors and microfluidic paper array devices (µPADs) for the detection of cancer biomarkers and circulating tumor cells (CTCs) are also assessed. Future challenges concerning the role and contributions of MNPs to the progress in nanomedicine have been outlined.

Magnetic Silica-Coated Iron Oxide Nanochains as Photothermal Agents, Disrupting the Extracellular Matrix, and Eradicating Cancer Cells

Cancerous cells and the tumor microenvironment are among key elements involved in cancer development, progression, and resistance to treatment. In order to tackle the cells and the extracellular matrix, we herein propose the use of a class of silica-coated iron oxide nanochains, which have superior magnetic responsiveness and can act as efficient photothermal agents. When internalized by different cancer cell lines and normal (non-cancerous) cells, the nanochains are not toxic, as assessed on 2D and 3D cell culture models. Yet, upon irradiation with near infrared light, the nanochains become efficient cytotoxic photothermal agents. Besides, not only do they generate hyperthermia, which effectively eradicates tumor cells in vitro, but they also locally melt the collagen matrix, as we evidence in real-time, using engineered cell sheets with self-secreted extracellular matrix. By simultaneously acting as physical (magnetic and photothermal) effectors and chemical delivery systems, the nanochain-based platforms offer original multimodal possibilities for prospective cancer treatment, affecting both the cells and the extracellular matrix.

Magnetic targeting of adoptively transferred tumour-specific nanoparticle-loaded CD8+ T cells does not improve their tumour infiltration in a mouse model of cancer but promotes the retention of these cells in tumour-draining lymph nodes

Background

Adoptive T cell-transfer (ATC) therapy is a highly promising cancer-treatment approach. However, in vivo-administered T cells tend to disperse, with only a small proportion reaching the tumour. To remedy this, magnetic targeting of T cells has been recently explored. Magnetic nanoparticles (MNPs) functionalised with antibodies were attached to effector T cells and magnetically recruited to tumour sites under MRI guidance. In this study, we investigated whether 3-aminopropyl-triethoxysilane (APS)-coated MNPs directly attached to CD8⁺ T cell membranes could also magnetically target and accumulate tumour-specific CD8⁺ T cells in solid tumours using an external magnetic field (EMF). As it has been shown that T cells associated with APS-coated MNPs are retained in lymph nodes (LNs), and tumour-draining LNs are the most common sites of solid-tumour metastases, we further evaluated whether magnetic targeting of APS-MNP-loaded CD8⁺ T cells could cause them to accumulate in tumour-draining LNs.

Results

First, we show that antigen-specific CD8⁺ T cells preserve their antitumor activity in vitro when associated with APS-MNPs. Next, we demonstrate that the application of a magnetic field enhanced the retention of APS-MNP-loaded OT-I CD8⁺ T cells under flow conditions in vitro. Using a syngeneic mouse model, we found similar numbers of APS-MNP-loaded OT-I CD8⁺ T cells and OT-I CD8⁺ T cells infiltrating the tumour 14 days after cell transfer. However, when a magnet was placed near the tumour during the transfer of tumour-specific APS-MNP-loaded CD8⁺ T cells to improve tumour infiltration, a reduced percentage of tumour-specific T cells was found infiltrating the tumour 14 days after cell transfer, which was reflected in a smaller reduction in tumour size compared to tumour-specific CD8⁺ T cells transferred with or without MNPs in the absence of a magnetic field. Nonetheless, magnet placement near the tumour site during cell transfer induced infiltration of activated tumour-specific CD8⁺ T cells in tumour-draining LNs, which remained 14 days after cell transfer.

Conclusions

The use of an EMF to improve targeting of tumour-specific T cells modified with APS-MNPs reduced the percentage of these cells infiltrating the tumour, but promoted the retention and the persistence of these cells in the tumour-draining LNs.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0520-0) contains supplementary material, which is available to authorized users.

Magnetically Assisted Control of Stem Cells Applied in 2D, 3D and In Situ Models of Cell Migration

The success of cell therapy approaches is greatly dependent on the ability to precisely deliver and monitor transplanted stem cell grafts at treated sites. Iron oxide particles, traditionally used in vivo for magnetic resonance imaging (MRI), have been shown to also represent a safe and efficient in vitro labelling agent for mesenchymal stem cells (MSCs). Here, stem cells were labelled with magnetic particles, and their resulting response to magnetic forces was studied using 2D and 3D models. Labelled cells exhibited magnetic responsiveness, which promoted localised retention and patterned cell seeding when exposed to magnet arrangements in vitro. Directed migration was observed in 2D culture when adherent cells were exposed to a magnetic field, and also when cells were seeded into a 3D gel. Finally, a model of cell injection into the rodent leg was used to test the enhanced localised retention of labelled stem cells when applying magnetic forces, using whole body imaging to confirm the potential use of magnetic particles in strategies seeking to better control cell distribution for in vivo cell delivery.

Disturbance of adhesomes by gold nanoparticles reveals a size- and cell type-bias

Gold nanoparticles (AuNP) have been thoroughly studied as multifunctional theranosis agents for cell imaging and cancer therapy as well as sensors due to their tunable physical and chemical properties. Although AuNP have proved to be safe in a wide concentration range, yet other important biological effects can arise in the sublethal window of treatment. This is especially pivotal to understand how AuNP can affect cell biology when labeling steps are needed for cell tracking in vivo, as nanoparticle loading can affect cell migratory/invasion ability, a function mediated by filamentous actin-rich nanometric structures collectively called adhesomes. It is noteworthy that, although numerous research studies have addressed the cell response to AuNP loading, yet none of them focuses on adhesome dynamics as a target of intracellular pathways affected by AuNP. We intend to study the collective dynamics of adhesive F-actin rich structures upon AuNP treatment as an approach to understand the complex AuNP-triggered modulation of migration/invasion related cellular functions. We demonstrated that citrate-coated spherical AuNP of different sizes (3, 11, 16, 30 and 40 nm) disturbed podosome-forming rosettes and the resulting extracellular matrix (ECM) degradation in a murine macrophage model depending on core size. This phenomenon was accompanied by a reduction in metalloproteinase MMP2 and an increment in metalloproteinase inhibitors, TIMP-1/2 and SerpinE1. We also found that AuNP treatment has opposite effects on focal adhesions (FA) in endothelial and mesenchymal stem cells. While endothelial cells reduced their mature FA number and ECM degradation rate upon AuNP treatment, mouse mesenchymal stem cells increased the number and size of mature FA and, therefore, the ECM degradation rate. Overall, AuNP appear to disturb adhesive structures and therefore migratory/invasive cell functions measured as ECM degradation ability, providing new insights into AuNP-cell interaction depending on cell type.

Comparative Heating Efficiency of Cobalt-, Manganese-, and Nickel-Ferrite Nanoparticles for a Hyperthermia Agent in Biomedicines

In this study, the ac magnetic hyperthermia responses of spinel CoFe₂O₄, MnFe₂O₄, and NiFe₂O₄ nanoparticles of comparable sizes (∼20 nm) were investigated to evaluate their feasibility of use in magnetic hyperthermia. The heating ability of EDT-coated nanoparticles which were dispersed in two different carrier media, deionized water and ethylene glycol, at concentrations of 1 and 2 mg/mL, was evaluated by estimating the specific loss power (SLP) (which is a measure of magnetic energy transformed into heat) under magnetic fields of 15, 25, and 50 kA/m at a constant frequency of 195 kHz. The maximum value of SLP has been found to be ∼315 W/g for CoFe₂O₄ and ∼295 W/g for MnFe₂O₄ and NiFe₂O₄ nanoparticles. We report very promising heating temperature rising characteristics of CoFe₂O₄, MnFe₂O₄, and NiFe₂O₄ nanoparticles under different applied magnetic fields that indicate the effectiveness of these nanoparticles as hyperthermia agents.

T cells loaded with magnetic nanoparticles are retained in peripheral lymph nodes by the application of a magnetic field

Background

T lymphocytes are highly dynamic elements of the immune system with a tightly regulated migration. T cell-based transfer therapies are promising therapeutic approaches which in vivo efficacy is often limited by the small proportion of administered cells that reaches the region of interest. Manipulating T cell localisation to improve specific targeting will increase the effectiveness of these therapies. Nanotechnology has been successfully used for localized release of drugs and biomolecules. In particular, magnetic nanoparticles (MNPs) loaded with biomolecules can be specifically targeted to a location by an external magnetic field (EMF). The present work studies whether MNP-loaded T cells could be targeted and retained in vitro and in vivo at a site of interest with an EMF.

Results

T cells were unable to internalize the different MNPs used in this study, which remained in close association with the cell membrane. T cells loaded with an appropriate MNP concentration were attracted to an EMF and retained in an in vitro capillary flow-system. MNP-loaded T cells were also magnetically retained in the lymph nodes after adoptive transfer in in vivo models. This enhanced in vivo retention was in part due to the EMF application and to a reduced circulating cell speed within the organ. This combined use of MNPs and EMFs did not alter T cell viability or function.

Conclusions

These studies reveal a promising approach to favour cell retention that could be implemented to improve cell-based therapy.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0440-z) contains supplementary material, which is available to authorized users.

Human adipose-derived stem cells loaded with drug-coated magnetic nanoparticles for in-vitro tumor cells targeting

Magnetic nanoparticles (MNPs) functionalized with different therapeutics delivered by mesenchymal stem cells represent a promising approach to improve the typical drug delivery methods. This innovative method, based on the "Trojan horse" principle, faces however important challenges related to the viability of the MNPs-loaded cells and drug stability. In the present study we report about an in vitro model of adipose-derived stem cells (ADSCs) loaded with palmitate-coated MNPs (MNPsPA) as antitumor drug carriers targeting a 3D tissue-like osteosarcoma cells. Cell viability, MNPsPA-drug loading capacity, cell speed, drug release rate, magnetization and zeta potential were determined and analysed. The results revealed that ADSCs loaded with MNPsPA-drug complexes retained their viability at relatively high drug concentrations (up to 1.22 pg antitumor drug/cell for 100% cell viability) and displayed higher speed compared to the targeted tumor cells in vitro. The magnetization of the sterilized MNPsPA complexes was 67 emu/g within a magnetic field corresponding to induction values of clinical MRI devices. ADSCs payload was around 9 pg magnetic material/cell, with an uptake rate of 6.25 fg magnetic material/min/cell. The presented model is a proof-of-concept platform for stem cells-mediated MNPs-drug delivery to solid tumors that could be further correlated with MRI tracking and magnetic hyperthermia for theranostic applications.

A Critical Review on Selected External Physical Cues and Modulation of Cell Behavior: Magnetic Nanoparticles, Non-thermal Plasma and Lasers

Physics-based biomedical approaches have proved their importance for the advancement of medical sciences and especially in medical diagnostics and treatments. Thus, the expectations regarding development of novel promising physics-based technologies and tools are very high. This review describes the latest research advances in biomedical applications of external physical cues. We overview three distinct topics: using high-gradient magnetic fields in nanoparticle-mediated cell responses; non-thermal plasma as a novel bactericidal agent; highlights in understanding of cellular mechanisms of laser irradiation. Furthermore, we summarize the progress, challenges and opportunities in those directions. We also discuss some of the fundamental physical principles involved in the application of each cue. Considerable technological success has been achieved in those fields. However, for the successful clinical translation we have to understand the limitations of technologies. Importantly, we identify the misconceptions pervasive in the discussed fields.

Tenacic Acids: A New Class of Tenacious Binders to Metal Oxide Surfaces

The backbone of 2-hydroxyisophthalic acid was identified as a potential metal oxide anchor because of the perfect alignment of all three of its donor groups for binding to inorganic surfaces. It can therefore be used in the design of organic linkers for metal oxide based hybrid materials. Optimized and scalable methods for the synthesis of 2-hydroxyisophthalic acid (1) and its 5-substituted derivatives: 5-bromo- (2), 5-sulfooxy- (3), 5-hydroxy- (4), and 5-PEG600 (5) are presented. Dynamic light scattering (DLS) demonstrated that compound 2 inhibits Fe(OH)3 precipitation when FeIII aqueous solutions are titrated with NaOH, while similar titrations in the presence of the structurally-related isophthalic and salicylic acids, both missing the third donor group, show turbidity at pHs as low as 2.3 and 3.5, respectively. The adduct synthesized from 4.5 nm γ-Fe2 O3 nanoparticles and 5 is water-, alcohol- and CH2 Cl2 -soluble, and forms stable aqueous colloids in the pH range of 4.4-8.7. Moreover, at a pH close to neutral these colloids survive at 100 °C, demonstrating the high practicality of 2-hydroxyisophthalic acid for nanoparticulate inorganic/organic hybrid material design.

Development and validation of broad-spectrum magnetic particle labelling processes for cell therapy manufacturing

Background

Stem cells are increasingly seen as a solution for many health challenges for an ageing population. However, their potential benefits in the clinic are currently curtailed by technical challenges such as high cell dose requirements and point of care delivery, which pose sourcing and logistics challenges. Cell manufacturing solutions are currently in development to address the supply issue, and ancillary technologies such as nanoparticle-based labelling are being developed to improve stem cell delivery and enable post-treatment follow-up.

Methods

The application of magnetic particle (MP) labelling to potentially scalable cell manufacturing processes was investigated in a range of therapeutically relevant cells, including mesenchymal stromal cells (MSC), cardiomyocytes (CMC) and neural progenitor cells (ReN). The efficiency and the biological effect of particle labelling were analysed using fluorescent imaging and cellular assays.

Results

Flow cytometry and fluorescent microscopy confirmed efficient labelling of monolayer cultures. Viability was shown to be retained post labelling for all three cell types. MSC and CMC demonstrated higher tolerance to MP doses up to 100× the standard concentration. This approach was also successful for MP labelling of suspension cultures, demonstrating efficient MP uptake within 3 h, while cell viability was unaffected by this suspension labelling process. Furthermore, a procedure to enable the storing of MP-labelled cell populations to facilitate cold chain transport to the site of clinical use was investigated. When MP-labelled cells were stored in hypothermic conditions using HypoThermosol solution for 24 h, cell viability and differentiation potential were retained post storage for ReN, MSC and beating CMC.

Conclusions

Our results show that a generic MP labelling strategy was successfully developed for a range of clinically relevant cell populations, in both monolayer and suspension cultures. MP-labelled cell populations were able to undergo transient low-temperature storage whilst maintaining functional capacity in vitro. These results suggest that this MP labelling approach can be integrated into cell manufacturing and cold chain transport processes required for future cell therapy approaches.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0968-0) contains supplementary material, which is available to authorized users.

Improving the Subcutaneous Mouse Tumor Model by Effective Manipulation of Magnetic Nanoparticles-Treated Implanted Cancer Cells

Murine tumor models have played a fundamental role in the development of novel therapeutic interventions and are currently widely used in translational research. Specifically, strategies that aim at reducing inter-animal variability of tumor size in transplantable mouse tumor models are of particular importance. In our approach, we used magnetic nanoparticles to label and manipulate colon cancer cells for the improvement of the standard syngeneic subcutaneous mouse tumor model. Following subcutaneous injection on the scruff of the neck, magnetically-tagged implanted cancer cells were manipulated by applying an external magnetic field towards localized tumor formation. Our data provide evidence that this approach can facilitate the formation of localized tumors of similar shape, reducing thereby the tumor size's variability. For validating the proof-of-principle, a low-dose of 5-FU was administered in small animal groups as a representative anticancer therapy. Under these experimental conditions, the 5-FU-induced tumor growth inhibition was statistically significant only after the implementation of the proposed method. The presented approach is a promising strategy for studying accurately therapeutic interventions in subcutaneous experimental solid tumor models allowing for the detection of statistically significant differences between smaller experimental groups.