Tracking stem cells in tissue-engineered organs using magnetic nanoparticles

Applications of Nanotechnology in the Field of Cardiology

Cardiovascular diseases (CVDs) are a leading cause of death globally, demanding innovative therapeutic strategies. Nanoformulations, including nanoparticles, address challenges in drug delivery, stem cell therapy, imaging, and gene delivery. Nanoparticles enhance drug solubility, bioavailability, and targeted delivery, with gas microbubbles, liposomal preparations, and paramagnetic nanoparticles showing potential in treating atherosclerosis and reducing systemic side effects. In stem cell therapy, nanoparticles improve cell culture, utilizing three-dimensional nanofiber scaffolds and enhancing cardiomyocyte growth. Gold nanoparticles and poly(lactic-co-glycolic acid) (PLGA)-derived microparticles promote stem cell survival. Stem cell imaging utilizes direct labeling with nanoparticles for magnetic resonance imaging (MRI), while optical tracking employs dye-conjugated nanoparticles. In gene delivery, polymeric nanoparticles like polyethylenimine (PEI) and dendrimers, graphene-based carriers, and chitosan nanoparticles offer alternatives to virus-mediated gene transfer. The potential of magnetic nanoparticles in gene therapy is explored, particularly in hepatocellular carcinoma. Overall, nanoparticles have transformative potential in cardiovascular disease management, with ongoing research poised to enhance clinical outcomes.

Magnetic hydrogel applications in articular cartilage tissue engineering

Articular cartilage defects afflict millions of individuals worldwide, presenting a significant challenge due to the tissue's limited self-repair capability and anisotropic nature. Hydrogel-based biomaterials have emerged as promising candidates for scaffold production in artificial cartilage construction, owing to their water-rich composition, biocompatibility, and tunable properties. Nevertheless, conventional hydrogels typically lack the anisotropic structure inherent to natural cartilage, impeding their clinical and preclinical applications. Recent advancements in tissue engineering (TE) have introduced magnetically responsive hydrogels, a type of intelligent hydrogel that can be remotely controlled using an external magnetic field. These innovative materials offer a means to create the desired anisotropic architecture required for successful cartilage TE. In this review, we first explore conventional techniques employed for cartilage repair and subsequently delve into recent breakthroughs in the application and utilization of magnetic hydrogels across various aspects of articular cartilage TE.

Nitrogen-vacancy center magnetic imaging of Fe3O4 nanoparticles inside the gastrointestinal tract of Drosophila melanogaster

Widefield magnetometry based on nitrogen-vacancy centers enables high spatial resolution imaging of magnetic field distributions without a need for spatial scanning. In this work, we show nitrogen-vacancy center magnetic imaging of Fe3O4 nanoparticles within the gastrointestinal tract of Drosophila melanogaster larvae. Vector magnetic field imaging based on optically detected magnetic resonance is carried out on dissected larvae intestine organs containing accumulations of externally loaded magnetic nanoparticles. The distribution of the magnetic nanoparticles within the tissue can be clearly deduced from the magnetic stray field measurements. Spatially resolved magnetic imaging requires the nitrogen-vacancy centers to be very close to the sample making the technique particularly interesting for thin tissue samples. This study is a proof of principle showing the capability of nitrogen-vacancy center magnetometry as a technique to detect magnetic nanoparticle distributions in Drosophila melanogaster larvae that can be extended to other biological systems.

Long-circulating magnetoliposomes as surrogates for assessing pancreatic tumour permeability and nanoparticle deposition

Nanocarriers are candidates for cancer chemotherapy delivery, with growing numbers of clinically-approved nano-liposomal formulations such as Doxil® and Onivyde® (liposomal doxorubicin and irinotecan) providing proof-of-concept. However, their complex biodistribution and the varying susceptibility of individual patient tumours to nanoparticle deposition remains a clinical challenge. Here we describe the preparation, characterisation, and biological evaluation of phospholipidic structures containing solid magnetic cores (SMLs) as an MRI-trackable surrogate that could aid in the clinical development and deployment of nano-liposomal formulations. Through the sequential assembly of size-defined iron oxide nanoparticle clusters with a stabilizing anionic phospholipid inner monolayer and an outer monolayer of independently-selectable composition, SMLs can mimic physiologically a wide range of nano-liposomal carrier compositions. In patient-derived xenograft models of pancreatic adenocarcinoma, similar tumour deposition of SML and their nano-liposomal counterparts of identical bilayer composition was observed in vivo, both at the tissue level (fluorescence intensities of 1.5 × 108 ± 1.8 × 107 and 1.2 × 108 ± 6.3 × 107, respectively; ns, 99% confidence interval) and non-invasively using MR imaging. We observed superior capabilities of SML as a surrogate for nano-liposomal formulations as compared to other clinically-approved iron oxide nano-formulations (ferumoxytol). In combination with diagnostic and therapeutic imaging tools, SMLs have high clinical translational potential to predict nano-liposomal drug carrier deposition and could assist in stratifying patients into treatment regimens that promote optimal tumour deposition of nanoparticulate chemotherapy carriers. STATEMENT OF SIGNIFICANCE: Solid magnetoliposomes (SMLs) with compositions resembling that of FDA-approved agents such as Doxil® and Onivyde® offer potential application as non-invasive MRI stratification agents to assess extent of tumour deposition of nano-liposomal therapeutics prior to administration. In animals with pancreatic adenocarcinoma (PDAC), SML-PEG exhibited (i) tumour deposition comparable to liposomes of the same composition; (ii) extended circulation times, with continued tumour deposition up to 24 hours post-injection; and (iii) MRI capabilities to determine tumour deposition up to 1 week post-injection, and confirmation of patient-to-patient variation in nanoparticulate deposition in tumours. Hence SMLs with controlled formulation are a step towards non-invasive MRI stratification approaches for patients, enabled by evaluation of the extent of deposition in tumours prior to administration of nano-liposomal therapeutics.

Ultrasound-enhanced cascade chemodynamic tumor nanotherapy with lactic acid-enabled hydrogen peroxide self-production

Chemodynamic therapy (CDT) is an effective therapeutic modality for cancer treatment with the action of a catalytic Fenton-like chemoreactive process. To furnish sufficient hydrogen peroxide (H₂O₂) for CDT, catalysts similar to superoxide dismutase are designed to be in cooperation with nanoplatforms. In this work, we rationally integrate lactate oxidase (LOD) with ultrasmall superparamagnetic iron oxide nanoparticles (USPION) to achieve high efficiency of the cascade Fenton reaction for efficient tumor therapy. During the sequential reaction, LOD converts lactic acid into H₂O₂ and pyruvate (PA) in situ, and then USPION with peroxidase-like activity generates large amounts of toxic hydroxyl radicals (˙OH) under the action of H₂O₂. Moreover, the reaction effectively utilizes the excess lactic acid of the tumor microenvironment (TME) as a new target of cancer treatment. To further achieve high-performance tumor treatment, ultrasound has been introduced for augmenting this specific chemoreactive tumor therapy, which can affect cancer cells mainly through sonoporation, cavitation, and thermal effect. With the effects of ultrasound irradiation, this work has constructed an efficient oncology treatment system for tumors. Moreover, the presence of USPION is highly desirable for contrast-enhanced T₁-weighted MRI for monitoring the therapeutic process of cancer in real time.

Multifunctional nanocarriers of Fe3O4@PLA-PEG/curcumin for MRI, magnetic hyperthermia and drug delivery

Background: Despite medicinal advances, cancer is still a big problem requiring better diagnostic and treatment tools. Magnetic nanoparticle (MNP)-based nanosystems for multiple-purpose applications were developed for these unmet needs. Methods: This study fabricated novel trifunctional MNPs of Fe₃O₄@PLA-PEG for drug release, MRI and magnetic fluid hyperthermia. Result: The MNPs provided a significant loading of curcumin (∼11%) with controllable release ability, a high specific absorption rate of 82.2 W/g and significantly increased transverse relaxivity (r₂ = 364.75 mM^-1 s^-1). The in vivo study confirmed that the MNPs enhanced MRI contrast in tumor observation and low-field magnetic fluid hyperthermia could effectively reduce the tumor size in mice bearing sarcoma 180. Conclusion: The nanocarrier has potential for drug release, cancer treatment monitoring and therapy.

Applications of Magnetic Particle Imaging in Biomedicine: Advancements and Prospects

Magnetic particle imaging (MPI) is a novel emerging noninvasive and radiation-free imaging modality that can quantify superparamagnetic iron oxide nanoparticles tracers. The zero endogenous tissue background signal and short image scanning times ensure high spatial and temporal resolution of MPI. In the context of precision medicine, the advantages of MPI provide a new strategy for the integration of the diagnosis and treatment of diseases. In this review, after a brief explanation of the simplified theory and imaging system, we focus on recent advances in the biomedical application of MPI, including vascular structure and perfusion imaging, cancer imaging, the MPI guidance of magnetic fluid hyperthermia, the visual monitoring of cell and drug treatments, and intraoperative navigation. We finally optimize MPI in terms of the system and tracers, and present future potential biomedical applications of MPI.

In vivo MRI tracking and therapeutic efficacy of transplanted mesenchymal stem cells labeled with ferrimagnetic vortex iron oxide nanorings for liver fibrosis repair

Mesenchymal stem cells (MSCs) have showed promising effects in the treatment of liver fibrosis. Long-term and noninvasive in vivo tracking of transplanted MSCs is essential for understanding the therapeutic mechanism of MSCs during the therapy of liver fibrosis. In this study, we report the development of a ferrimagnetic vortex iron oxide nanoring (FVIO)-based nanotracer for the long-term visualization of transplanted human MSCs (hMSCs) by magnetic resonance imaging (MRI). The FVIOs were prepared by a hydrothermal reaction followed by hydrogen reduction. To endow the FVIOs with biocompatibility, polyethylene glycol amine (mPEG-NH₂) was covalently coupled on the surface of FVIOs, forming FVIO@PEG nanotracers with high contrast enhancement and intracellular uptake. The hMSCs labeled with FVIO@PEG nanotracers exhibited enhanced MRI contrast than those labeled with a commercial contrast agent, and could be continuously monitored by MRI in liver fibrosis mice for 28 days after transplantation, clearly clarifying the migration behavior of hMSCs in vivo. Moreover, we explored the therapeutic mechanism of the FVIO@PEG labeled hMSCs in the amelioration of liver fibrosis, including the reduction in inflammation and oxidative stress, the inhibition of hepatic fibrosis-caused histopathological damage, as well as the down-regulation of the expression of relevant cytokines. The results obtained in this work may deepen our understanding of the behavior and role of hMSCs in the treatment of liver fibrosis, which is key to the clinical application of stem cells in the therapy of liver diseases.

Magnetic particle imaging: tracer development and the biomedical applications of a radiation-free, sensitive, and quantitative imaging modality

Magnetic particle imaging (MPI) is an emerging tracer-based modality that enables real-time three-dimensional imaging of the non-linear magnetisation produced by superparamagnetic iron oxide nanoparticles (SPIONs), in the presence of an external oscillating magnetic field. As a technique, it produces highly sensitive radiation-free tomographic images with absolute quantitation. Coupled with a high contrast, as well as zero signal attenuation at-depth, there are essentially no limitations to where that can be imaged within the body. These characteristics enable various biomedical applications of clinical interest. In the opening sections of this review, the principles of image generation are introduced, along with a detailed comparison of the fundamental properties of this technique with other common imaging modalities. The main feature is a presentation on the up-to-date literature for the development of SPIONs tailored for improved imaging performance, and developments in the current and promising biomedical applications of this emerging technique, with a specific focus on theranostics, cell tracking and perfusion imaging. Finally, we will discuss recent progress in the clinical translation of MPI. As signal detection in MPI is almost entirely dependent on the properties of the SPION employed, this work emphasises the importance of tailoring the synthetic process to produce SPIONs demonstrating specific properties and how this impacts imaging in particular applications and MPI's overall performance.

Smart Magnetic Nanocarriers for Multi-Stimuli On-Demand Drug Delivery

In this study, we report the realization of drug-loaded smart magnetic nanocarriers constituted by superparamagnetic iron oxide nanoparticles encapsulated in a dual pH- and temperature-responsive poly (N-vinylcaprolactam-co-acrylic acid) copolymer to achieve highly controlled drug release and localized magnetic hyperthermia. The magnetic core was constituted by flower-like magnetite nanoparticles with a size of 16.4 nm prepared by the polyol approach, with good saturation magnetization and a high specific absorption rate. The core was encapsulated in poly (N-vinylcaprolactam-co-acrylic acid) obtaining magnetic nanocarriers that revealed reversible hydration/dehydration transition at the acidic condition and/or at temperatures above physiological body temperature, which can be triggered by magnetic hyperthermia. The efficacy of the system was proved by loading doxorubicin with very high encapsulation efficiency (>96.0%) at neutral pH. The double pH- and temperature-responsive nature of the magnetic nanocarriers facilitated a burst, almost complete release of the drug at acidic pH under hyperthermia conditions, while a negligible amount of doxorubicin was released at physiological body temperature at neutral pH, confirming that in addition to pH variation, drug release can be improved by hyperthermia treatment. These results suggest this multi-stimuli-sensitive nanoplatform is a promising candidate for remote-controlled drug release in combination with magnetic hyperthermia for cancer treatment.

Mechanisms of immune response to inorganic nanoparticles and their degradation products

Careful assessment of the biological fate and immune response of inorganic nanoparticles is crucial for use of such carriers in drug delivery and other biomedical applications. Many studies have elucidated the cellular and molecular mechanisms of the interaction of inorganic nanoparticles with the components of the immune system. The biodegradation and dissolution of inorganic nanoparticles can influence their ensuing immune response. While the immunological properties of inorganic nanoparticles as a function of their physicochemical properties have been investigated in detail, little attention has been paid to the immune adverse effects towards the degradation products of these nanoparticles. To fill this gap, we herein summarize the cellular mechanisms of immune response to inorganic nanoparticles and their degradation products with specific focus on immune cells. We also accentuate the importance of designing new methods and instruments for the in situ characterization of inorganic nanoparticles in order to assess their safety as a result of degradation. This review further sheds light on factors that need to be considered in the design of safe and effective inorganic nanoparticles for use in delivery of bioactive and imaging agents.

Nanotechnology in cardiac stem cell therapy: cell modulation, imaging and gene delivery

The wide arena of applications opened by nanotechnology is multidimensional. It is already been proven that its prominence can continuously influence human life. The role of stem cells in curing degenerative diseases is another major area of research. Cardiovascular diseases are one of the major causes of death globally. Nanotechnology-assisted stem cell therapy could be used to tackle the challenges faced in the management of cardiovascular diseases. In spite of the positive indications and proven potential of stem cells to differentiate into cardiomyocytes for cardiac repair and regeneration during myocardial infarction, this therapeutic approach still remains in its infancy due to several factors such as non-specificity of injected cells, insignificant survival rate, and low cell retention. Attempts to improve stem cell therapy using nanoparticles have shown some interest among researchers. This review focuses on the major hurdles associated with cardiac stem cell therapy and the role of nanoparticles to overcome the major challenges in this field, including cell modulation, imaging, tracking and gene delivery.

This review summarizes the potential challenges present in cardiac stem cell therapy and the major role of nanotechnology to overcome these challenges including cell modulation, tracking and imaging of stem cells.

Cellular and molecular imaging for stem cell tracking in neurological diseases

Stem cells (SCs) are cells with strong proliferation ability, multilineage differentiation potential and self-renewal capacity. SC transplantation represents an important therapeutic advancement for the treatment strategy of neurological diseases, both in the preclinical experimental and clinical settings. Innovative and breakthrough SC labelling and tracking technologies are widely used to monitor the distribution and viability of transplanted cells non-invasively and longitudinally. Here we summarised the research progress of the main tracers, labelling methods and imaging technologies involved in current SC tracking technologies for various neurological diseases. Finally, the applications, challenges and unresolved problems of current SC tracing technologies were discussed.

Exploring precision polymers to fine-tune magnetic resonance imaging properties of iron oxide nanoparticles

The use of bio-polymers as stabilising agents for iron oxide-based negative magnetic resonance imaging (MRI) contrast agents has become popular in recent years, however the wide polydispersity of biologically-derived and commercially available polymers limits the ability to produce truly tuneable and reproducible behaviour, a major challenge in this area. In this work, stable colloids of iron oxide nanoparticles were prepared utilising precision-engineered bio-polymer mimics, poly(2-acrylamido-2-methylpropane sodium sulfonate) (P(AMPS)) polymers, with controlled narrow polydispersity molecular weights, as templating stabilisers. In addition to producing magnetic colloids with excellent MRI contrast capabilities (r₂ values reaching 434.2 mM^-1 s^-1 at 25 °C and 23 MHz, several times higher than similar commercial analogues), variable field relaxometry provided unexpected important insights into the dynamic environment of the hydrated materials, and hence their exceptional MRI behaviour. Thanks to the polymer's templating backbone and flexible conformation in aqueous suspension, nanocomposites appear to behave as "multi-core" clustered species, enhancing interparticle interactions whilst retaining water diffusion, boosting relaxation properties at low frequency. This clustering behaviour, evidenced by small-angle X-ray scattering, and strong relaxometric response, was fine-tuned using the well-defined molecular weight polymer species with precise iron to polymer ratios. By also showing negligible haemolytic activity, these nanocomposites exhibit considerable potential for MRI diagnostics.

L-Lysine-modified Fe3O4 nanoparticles for magnetic cell labeling

The efficiency of magnetic labeling with L-Lys-modified Fe₃O₄ magnetic nanoparticles (MNPs) and the stability of magnetization of rat adipose-derived mesenchymal stem cells, lineage-negative (Lin(-)) hematopoietic progenitor cells from mouse bone marrow and human leukemia K562 cells were studied. For this purpose, covalent modification of MNPs with 3-aminopropylsilane and N-di-Fmoc-L-lysine followed by removal of N-protecting groups was carried out. Since the degree of hydroxylation of the surface of the starting nanoparticles plays a crucial role in the silanization reaction and the possibility of obtaining stable colloidal solutions. In present work we for the first time performed a comparative qualitative and quantitative evaluation of the number of adsorbed water molecules and hydroxyl groups on the surface of chemically and physically obtained Fe₃O₄ MNPs using comprehensive FTIR spectroscopy and thermogravimetric analysis. The results obtained can be further used for magnetic labeling of cells in experiments in vitro and in vivo.

In Vivo Tracking of Tissue Engineered Constructs

To date, the fields of biomaterials science and tissue engineering have shown great promise in creating bioartificial tissues and organs for use in a variety of regenerative medicine applications. With the emergence of new technologies such as additive biomanufacturing and 3D bioprinting, increasingly complex tissue constructs are being fabricated to fulfill the desired patient-specific requirements. Fundamental to the further advancement of this field is the design and development of imaging modalities that can enable visualization of the bioengineered constructs following implantation, at adequate spatial and temporal resolution and high penetration depths. These in vivo tracking techniques should introduce minimum toxicity, disruption, and destruction to treated tissues, while generating clinically relevant signal-to-noise ratios. This article reviews the imaging techniques that are currently being adopted in both research and clinical studies to track tissue engineering scaffolds in vivo, with special attention to 3D bioprinted tissue constructs.

Cartilage Tissue Engineering Using Stem Cells and Bioprinting Technology-Barriers to Clinical Translation

There is no long-term treatment strategy for young and active patients with cartilage defects. Early and effective joint preserving treatments in these patients are crucial in preventing the development of osteoarthritis. Tissue engineering over the past few decades has presented hope in overcoming the issues involved with current treatment strategies. Novel advances in 3D bioprinting technology have promoted more focus on efficient delivery of engineered tissue constructs. There have been promising in-vitro studies and several animal studies looking at 3D bioprinting of engineered cartilage tissue. However, to date there are still no human clinical trials using 3D printed engineered cartilage tissue. This review begins with discussion surrounding the difficulties with articular cartilage repair and the limitations of current clinical management options which have led to research in cartilage tissue engineering. Next, the major barriers in each of the 4 components of cartilage tissue engineering; cells, scaffolds, chemical, and physical stimulation will be reviewed. Strategies that may overcome these barriers will be discussed. Finally, we will discuss the barriers surrounding intraoperative delivery of engineered tissue constructs and possible solutions.

Incorporation of nanoparticles into transplantable decellularized matrices: Applications and challenges

Decellularization of tissues can significantly improve regenerative medicine and tissue engineering by producing natural, less immunogenic, three-dimensional, acellular matrices with high biological activity for transplantation. Decellularized matrices retain specific critical components of native tissues such as stem cell niche, various growth factors, and the ability to regenerate in vivo. However, recellularization and functionalization of these matrices remain limited, highlighting the need to improve the characteristics of decellularized matrices. Incorporating nanoparticles into decellularized tissues can overcome these limitations because nanoparticles possess unique properties such as multifunctionality and can modify the surface of decellularized matrices with additional growth factors, which can be loaded onto the nanoparticles. Therefore, in this minireview, we highlight the various approaches used to improve decellularized matrices with incorporation of nanoparticles and the challenges present in these applications.

Yolk-Shell Nanostructures: Design, Synthesis, and Biomedical Applications

Yolk-shell nanostructures (YSNs) composed of a core within a hollow cavity surrounded by a porous outer shell have received tremendous research interest owing to their unique structural features, fascinating physicochemical properties, and widespread potential applications. Here, a comprehensive overview of the design, synthesis, and biomedical applications of YSNs is presented. The synthetic strategies toward YSNs are divided into four categories, including hard-templating, soft-templating, self-templating, and multimethod combination synthesis. For the hard- or soft-templating strategies, different types of rigid or vesicle templates are used for making YSNs. For the self-templating strategy, a number of unconventional synthetic methods without additional templates are introduced. For the multimethod combination strategy, various methods are applied together to produce YSNs that cannot be obtained directly by only a single method. The biomedical applications of YSNs including biosensing, bioimaging, drug/gene delivery, and cancer therapy are discussed in detail. Moreover, the potential superiority of YSNs for these applications is also highlighted. Finally, some perspectives on the future research and development of YSNs are provided.

Photoacoustic Imaging of Embryonic Stem Cell-Derived Cardiomyocytes in Living Hearts with Ultrasensitive Semiconducting Polymer Nanoparticles

The last decade has seen impressive progress in human embryonic stem cell-derived cardiomyocytes (hESC-CMs) that makes them ideal tools to repair injured hearts. To achieve an optimal outcome, advanced molecular imaging methods are essential to accurately track these transplanted cells in the heart. Herein, we demonstrate for the first time that a class of photoacoustic nanoparticles (PANPs) incorporating semiconducting polymers (SPs) as contrast agents can be used in the photoacoustic imaging (PAI) of transplanted hESC-CMs in living mouse hearts. This is achieved by virtue of two benefits of PANPs. First, strong PA signals and specific spectral features of SPs allow PAI to sensitively detect and distinguish a small number of PANP-labeled cells (2,000) from background tissues in vivo. Second, the PANPs show a high efficiency for hESC-CM labeling without adverse effects on cell structure, function, and gene expression. Assisted by ultrasound imaging, the delivery and engraftment of hESC-CMs in living mouse hearts can be assessed by PANP-based PAI with high spatial resolution (~100 μm). In summary, this study explores and validates a novel application of SPs as a PA contrast agent to track labeled cells with high sensitivity and accuracy in vivo, highlighting the advantages of integrating PAI and PANPs to advance cardiac regenerative therapies.

Nanotechnology for Neuroscience: Promising Approaches for Diagnostics, Therapeutics and Brain Activity Mapping

Unlocking the secrets of the brain is a task fraught with complexity and challenge - not least due to the intricacy of the circuits involved. With advancements in the scale and precision of scientific technologies, we are increasingly equipped to explore how these components interact to produce a vast range of outputs that constitute function and disease. Here, an insight is offered into key areas in which the marriage of neuroscience and nanotechnology has revolutionized the industry. The evolution of ever more sophisticated nanomaterials culminates in network-operant functionalized agents. In turn, these materials contribute to novel diagnostic and therapeutic strategies, including drug delivery, neuroprotection, neural regeneration, neuroimaging and neurosurgery. Further, the entrance of nanotechnology into future research arenas including optogenetics, molecular/ion sensing and monitoring, and piezoelectric effects is discussed. Finally, considerations in nanoneurotoxicity, the main barrier to clinical translation, are reviewed, and direction for future perspectives is provided.

Stem Cell Tracking Technologies for Neurological Regenerative Medicine Purposes

The growing field of stem cell therapy is moving toward clinical trials in a variety of applications, particularly for neurological diseases. However, this translation of cell therapies into humans has prompted a need to create innovative and breakthrough methods for stem cell tracing, to explore the migration routes and its reciprocity with microenvironment targets in the body, to monitor and track the outcome after stem cell transplantation therapy, and to track the distribution and cell viability of transplanted cells noninvasively and longitudinally. Recently, a larger number of cell tracking methods in vivo were developed and applied in animals and humans, including magnetic resonance imaging, nuclear medicine imaging, and optical imaging. This review has been intended to summarize the current use of those imaging tools in tracking stem cells, detailing their main features and drawbacks, including image resolution, tissue penetrating depth, and biosafety aspects. Finally, we address that multimodality imaging method will be a more potential tracking tool in the future clinical application.

Assessing cell-nanoparticle interactions by high content imaging of biocompatible iron oxide nanoparticles as potential contrast agents for magnetic resonance imaging

Stem cell tracking in cellular therapy and regenerative medicine is an urgent need, superparamagnetic iron oxide nanoparticles (IONPs) could be used as contrast agents in magnetic resonance imaging (MRI) that allows visualization of the implanted cells ensuring they reach the desired sites in vivo. Herein, we report the study of the interaction of 3,4-dihydroxyhydrocinnamic acid (DHCA) functionalized IONPs that have desirable properties for T2 - weighted MRI, with bone marrow-derived primary human mesenchymal stem cells (hMSCs). Using the multiparametric high-content imaging method, we evaluate cell viability, formation of reactive oxygen species, mitochondrial health, as well as cell morphology and determine that the hMSCs are minimally affected after labelling with IONPs. Their cellular uptake is visualized by transmission electron microscopy (TEM) and Prussian Blue staining, and quantified using an iron specific colourimetric method. In vitro and in vivo studies demonstrate that these IONPs are biocompatible and can produce significant contrast enhancement in T2-weighted MRI. Iron oxide nanoparticles are detected in vivo as hypointense regions in the liver up to two weeks post injection using 9.4 T MRI. These DHCA functionalized IONPs are promising contrast agents for stem cell tracking by T2-weighted MRI as they are biocompatible and show no evidence of cytotoxic effects on hMSCs.

High magnetisation, monodisperse and water-dispersible CoFe@Pt core/shell nanoparticles

High magnetisation and monodisperse CoFe alloy nanoparticles are desired for a wide range of biomedical applications. However, these CoFe nanoparticles are prone to oxidation, resulting in the deterioration of their magnetic properties. In the current work, CoFe alloy nanoparticles were prepared by thermal decomposition of cobalt and iron carbonyls in organic solvents at high temperatures. Using a seeded growth method, we successfully synthesised chemically stable CoFe@Pt core/shell nanostructures. The obtained core/shell nanoparticles have high saturation magnetisation up to 135 emu g^-1. The magnetisation value of the core/shell nanoparticles remains 93 emu g^-1 after being exposed to air for 12 weeks. Hydrophobic CoFe@Pt nanoparticles were rendered water-dispersible by encapsulating with poly(maleic anhydride-alt-1-octadecene) (PMAO). These nanoparticles were stable in water for at least 3 months and in a wide range of pH from 2 to 11.

Nanoparticles for bone tissue engineering

Tissue engineering (TE) envisions the creation of functional substitutes for damaged tissues through integrated solutions, where medical, biological, and engineering principles are combined. Bone regeneration is one of the areas in which designing a model that mimics all tissue properties is still a challenge. The hierarchical structure and high vascularization of bone hampers a TE approach, especially in large bone defects. Nanotechnology can open up a new era for TE, allowing the creation of nanostructures that are comparable in size to those appearing in natural bone. Therefore, nanoengineered systems are now able to more closely mimic the structures observed in naturally occurring systems, and it is also possible to combine several approaches - such as drug delivery and cell labeling - within a single system. This review aims to cover the most recent developments on the use of different nanoparticles for bone TE, with emphasis on their application for scaffolds improvement; drug and gene delivery carriers, and labeling techniques. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:590-611, 2017.

Nanostructured scaffold as a determinant of stem cell fate

The functionality of stem cells is tightly regulated by cues from the niche, comprising both intrinsic and extrinsic cell signals. Besides chemical and growth factors, biophysical signals are important components of extrinsic signals that dictate the stem cell properties. The materials used in the fabrication of scaffolds provide the chemical cues whereas the shape of the scaffolds provides the biophysical cues. The effect of the chemical composition of the scaffolds on stem cell fate is well researched. Biophysical signals such as nanotopography, mechanical forces, stiffness of the matrix, and roughness of the biomaterial influence the fate of stem cells. However, not much is known about their role in signaling crosstalk, stem cell maintenance, and directed differentiation. Among the various techniques for scaffold design, nanotechnology has special significance. The role of nanoscale topography in scaffold design for the regulation of stem cell behavior has gained importance in regenerative medicine. Nanotechnology allows manipulation of highly advanced surfaces/scaffolds for optimal regulation of cellular behavior. Techniques such as electrospinning, soft lithography, microfluidics, carbon nanotubes, and nanostructured hydrogel are described in this review, along with their potential usage in regenerative medicine. We have also provided a brief insight into the potential signaling crosstalk that is triggered by nanomaterials that dictate a specific outcome of stem cells. This concise review compiles recent developments in nanoscale architecture and its importance in directing stem cell differentiation for prospective therapeutic applications.

Magnetic Resonance Imaging of Human-Derived Amniotic Membrane Stem Cells Using PEGylated Superparamagnetic Iron Oxide Nanoparticles

OBJECTIVE

The label and detection of cells injected into target tissues is an area of focus for researchers. Iron oxide nanoparticles can be used to label cells as they have special characteristics. The purpose of this study is to examine the effects of iron oxide nanoparticles on human-derived amniotic membrane stem cell (hAMCs) survival and to investigate the magnetic properties of these nanoparticles with increased contrast in magnetic resonance imaging (MRI).

MATERIALS AND METHODS

In this experimental study, we initially isolated mesenchymal stem cells from amniotic membranes and analyzed them by flow cytometry. In addition, we synthesized superparamagnetic iron oxide nanoparticles (SPIONs) and characterized them by various methods. The SPIONs were incubated with hAMCs at concentrations of 25-800 μg/mL. The cytotoxicity of nanoparticles on hAMCs was measured by the MTT assay. Next, we evaluated the effectiveness of the magnetic nanoparticles as MRI contrast agents. Solutions of SPION were prepared in water at different iron concentrations for relaxivity measurements by a 1.5 Tesla clinical MRI instrument.

RESULTS

The isolated cells showed an adherent spindle shaped morphology. Polyethylene glycol (PEG)-coated SPIONs exhibited a spherical morphology. The average particle size was 20 nm and magnetic saturation was 60 emu/g. Data analysis showed no significant reduction in the percentage of viable cells (97.86 ± 0.41%) after 72 hours at the 125 μg/ml concentration compared with the control. The relaxometry results of this SPION showed a transverse relaxivity of 6.966 (μg/ml.s)(-1).

CONCLUSION

SPIONs coated with PEG used in this study at suitable concentrations had excellent labeling efficiency and biocompatibility for hAMCs.

Nano-Enabled Approaches for Stem Cell-Based Cardiac Tissue Engineering

Cardiac diseases are the most prevalent causes of mortality in the world, putting a major economic burden on global healthcare system. Tissue engineering strategies aim at developing efficient therapeutic approaches to overcome the current challenges in prolonging patients survival upon cardiac diseases. The integration of advanced biomaterials and stem cells has offered enormous promises for regeneration of damaged myocardium. Natural or synthetic biomaterials have been extensively used to deliver cells or bioactive molecules to the site of injury in heart. Additionally, nano-enabled approaches (e.g., nanomaterials, nanofeatured surfaces) have been instrumental in developing suitable scaffolding biomaterials and regulating stem cells microenvironment to achieve functional therapeutic outcomes. This review article explores tissue engineering strategies, which have emphasized on the use of nano-enabled approaches in combination with stem cells for regeneration and repair of injured myocardium upon myocardial infarction (MI). Primarily a wide range of biomaterials, along with different types of stem cells, which have utilized in cardiac tissue engineering will be presented. Then integration of nanomaterials and surface nanotopographies with biomaterials and stem cells for myocardial regeneration will be presented. The advantages and challenges of these approaches will be reviewed and future perspective will be discussed.

Doxorubicin loaded dual pH- and thermo-responsive magnetic nanocarrier for combined magnetic hyperthermia and targeted controlled drug delivery applications

Magnetic nanocarriers have attracted increasing attention for multimodal cancer therapy due to the possibility to deliver heat and drugs locally. The present study reports the development of magnetic nanocomposites (MNCs) made of an iron oxide core and a pH- and thermo-responsive polymer shell, that can be used as both hyperthermic agent and drug carrier. The conjugation of anticancer drug doxorubicin (DOX) to the pH- and thermo-responsive MNCs via acid-cleavable imine linker provides advanced features for the targeted delivery of DOX molecules via the combination of magnetic targeting, and dual pH- and thermo-responsive behaviour which offers spatial and temporal control over the release of DOX. The iron oxide cores exhibit a superparamagnetic behaviour with a saturation magnetization around 70 emu g(-1). The MNCs contained 8.1 wt% of polymer and exhibit good heating properties in an alternating magnetic field. The drug release experiments confirmed that only a small amount of DOX was released at room temperature and physiological pH, while the highest drug release of 85.2% was obtained after 48 h at acidic tumour pH under hyperthermia conditions (50 °C). The drug release kinetic followed Korsmeyer-Peppas model and displayed Fickian diffusion mechanism. From the results obtained it can be concluded that this smart magnetic nanocarrier is promising for applications in multi-modal cancer therapy, to target and efficiently deliver heat and drug specifically to the tumour.

Tracking and Quantification of Magnetically Labeled Stem Cells using Magnetic Resonance Imaging

Stem cell based therapies have critical impacts on treatments and cures of diseases such as neurodegenerative or cardiovascular disease. In vivo tracking of stem cells labeled with magnetic contrast agents is of particular interest and importance as it allows for monitoring of the cells' bio-distribution, viability, and physiological responses. Herein, recent advances are introduced in tracking and quantification of super-paramagnetic iron oxide (SPIO) nanoparticles-labeled cells with magnetic resonance imaging, a noninvasive approach that can longitudinally monitor transplanted cells. This is followed by recent translational research on human stem cells that are dual-labeled with green fluorescence protein (GFP) and SPIO nanoparticles, then transplanted and tracked in a chicken embryo model. Cell labeling efficiency, viability, and cell differentiation are also presented.

Stimuli-responsive magnetic nanoparticles for tumor-targeted bimodal imaging and photodynamic/hyperthermia combination therapy

Despite magnetic nanoparticles having shown great potential in cancer treatment, tremendous challenges related to diagnostic sensitivity and treatment efficacy for clinical application remain. Herein, we designed optimized multifunctional magnetite nanoparticles (AHP@MNPs), composed of Fe3O4 nanoparticles and photosensitizer conjugated hyaluronic acid (AHP), to achieve enhanced tumor diagnosis and therapy. Fe3O4 nanoparticles (MNPs) were synthesized by a facile hydrolysis method. MNPs have higher biocompatibility, controllable particle sizes, and desirable magnetic properties. The fabricated AHP@MNPs have enhanced water solubility (average size: 108.13 ± 1.08 nm), heat generation properties, and singlet oxygen generation properties upon magnetic and laser irradiation. The AHP@MNPs can target tumors via CD44 receptor-mediated endocytosis, which have enhanced tumor therapeutic effects through photodynamic/hyperthermia-combined treatment without any drugs. We successfully detected tumors implanted in mice via magnetic resonance imaging and optical imaging. Furthermore, we demonstrated the photodynamic/hyperthermia-combined therapeutic efficacy of AHP@MNPs with synergistically enhanced efficacy against cancer.

Labeling of mesenchymal stem cells for MRI with single-cell sensitivity

Sensitive cell detection by magnetic resonance imaging (MRI) is an important tool for the development of cell therapies. However, clinically approved contrast agents that allow single-cell detection are currently not available. Therefore, we compared very small iron oxide nanoparticles (VSOP) and new multicore carboxymethyl dextran-coated iron oxide nanoparticles (multicore particles, MCP) designed by our department for magnetic particle imaging (MPI) with discontinued Resovist^® regarding their suitability for detection of single mesenchymal stem cells (MSC) by MRI. We achieved an average intracellular nanoparticle (NP) load of >10 pg Fe per cell without the use of transfection agents. NP loading did not lead to significantly different results in proliferation, colony formation, and multilineage in vitro differentiation assays in comparison to controls. MRI allowed single-cell detection using VSOP, MCP, and Resovist^® in conjunction with high-resolution T2*-weighted imaging at 7 T with postprocessing of phase images in agarose cell phantoms and in vivo after delivery of 2,000 NP-labeled MSC into mouse brains via the left carotid artery. With optimized labeling conditions, a detection rate of ~45% was achieved; however, the experiments were limited by nonhomogeneous NP loading of the MSC population. Attempts should be made to achieve better cell separation for homogeneous NP loading and to thus improve NP-uptake-dependent biocompatibility studies and cell detection by MRI and future MPI. Additionally, using a 7 T MR imager equipped with a cryocoil resulted in approximately two times higher detection. In conclusion, we established labeling conditions for new high-relaxivity MCP, VSOP, and Resovist^® for improved MRI of MSC with single-cell sensitivity.

Bioluminescent magnetic nanoparticles as potential imaging agents for mammalian spermatozoa

BACKGROUND

Nanoparticles have emerged as key materials for developing applications in nanomedicine, nanobiotechnology, bioimaging and theranostics. Existing bioimaging technologies include bioluminescent resonance energy transfer-conjugated quantum dots (BRET-QDs). Despite the current use of BRET-QDs for bioimaging, there are strong concerns about QD nanocomposites containing cadmium which exhibits potential cellular toxicity.

RESULTS

In this study, bioluminescent composites comprised of magnetic nanoparticles and firefly luciferase (Photinus pyralis) are examined as potential light-emitting agents for imaging, detection, and tracking mammalian spermatozoa. Characterization was carried out using infrared spectroscopy, TEM and cryo-TEM imaging, and ζ-potential measurements to demonstrate the successful preparation of these nanocomposites. Binding interactions between the synthesized nanoparticles and spermatozoon were characterized using confocal and atomic/magnetic force microscopy. Bioluminescence imaging and UV-visible-NIR microscopy results showed light emission from sperm samples incubated with the firefly luciferase-modified nanoparticles. Therefore, these newly synthesized luciferase-modified magnetic nanoparticles show promise as substitutes for QD labeling, and can potentially also be used for in vivo manipulation and tracking, as well as MRI techniques.

CONCLUSIONS

These preliminary data indicate that luciferase-magnetic nanoparticle composites can potentially be used for spermatozoa detection and imaging. Their magnetic properties add additional functionality to allow for manipulation, sorting, or tracking of cells using magnetic techniques.

Methods of Monitoring Cell Fate and Tissue Growth in Three-Dimensional Scaffold-Based Strategies for In Vitro Tissue Engineering

In the field of tissue engineering, there is a need for methods that allow assessing the performance of tissue-engineered constructs noninvasively in vitro and in vivo. To date, histological analysis is the golden standard to retrieve information on tissue growth, cellular distribution, and cell fate on tissue-engineered constructs after in vitro cell culture or on explanted specimens after in vivo applications. Yet, many advances have been made to optimize imaging techniques for monitoring tissue-engineered constructs with a sub-mm or μm resolution. Many imaging modalities have first been developed for clinical applications, in which a high penetration depth has been often more important than lateral resolution. In this study, we have reviewed the current state of the art in several imaging approaches that have shown to be promising in monitoring cell fate and tissue growth upon in vitro culture. Depending on the aimed tissue type and scaffold properties, some imaging methods are more applicable than others. Optical methods are mostly suited for transparent materials such as hydrogels, whereas magnetic resonance-based methods are mostly applied to obtain contrast between hard and soft tissues regardless of their transparency. Overall, this review shows that the field of imaging in scaffold-based tissue engineering is developing at a fast pace and has the potential to overcome the limitations of destructive endpoint analysis.

Polyol synthesis, functionalisation, and biocompatibility studies of superparamagnetic iron oxide nanoparticles as potential MRI contrast agents

Iron oxide nanoparticles (IONPs) of low polydispersity were obtained through a simple polyol synthesis in high pressure and high temperature conditions. The control of the size and morphology of the nanoparticles was studied by varying the solvent used, the amount of iron precursor and the reaction time. Compared with conventional synthesis methods such as thermal decomposition or co-precipitation, this process yields nanoparticles with a narrow particle size distribution in a simple, reproducible and cost effective manner without the need for an inert atmosphere. For example, IONPs with a diameter of ca. 8 nm could be made in a reproducible manner and with good crystallinity as evidenced by X-ray diffraction analysis and high saturation magnetization value (84.5 emu g(-1)). The surface of the IONPs could be tailored post synthesis with two different ligands which provided functionality and stability in water and phosphate buffer saline (PBS). Their potential as a magnetic resonance imaging (MRI) contrast agent was confirmed as they exhibited high r1 and r2 relaxivities of 7.95 mM(-1) s(-1) and 185.58 mM(-1) s(-1) respectively at 1.4 T. Biocompatibility and viability of IONPs in primary human mesenchymal stem cells (hMSCs) was studied and confirmed.

Citrate-capped iron oxide nanoparticles impair the osteogenic differentiation potential of rat mesenchymal stem cells

The cellular uptake of citrate-capped iron oxide nanoparticles can impair the osteogenic differentiation of MSCs.

Nanoparticles-Assisted Stem Cell Therapy for Ischemic Heart Disease

Stem cell therapy has attracted increasing attention as a promising treatment strategy for cardiac repair in ischemic heart disease. Nanoparticles (NPs), with their superior physical and chemical properties, have been widely utilized to assist stem cell therapy. With the help of NPs, stem cells can be genetically engineered for enhanced paracrine profile. To further understand the fate and behaviors of stem cells in ischemic myocardium, imaging NPs can label stem cells and be tracked in vivo under multiple modalities. Besides that, NPs can also be used to enhance stem cell retention in myocardium. These facts have raised efforts on the development of more intelligent and multifunctional NPs for cellular application. Herein, an overview of the applications of NPs-assisted stem cell therapy is given. Key issues and future prospects are also critically addressed.

A novel magnetic hydrogel with aligned magnetic colloidal assemblies showing controllable enhancement of magnetothermal effect in the presence of alternating magnetic field

A novel magnetic hydrogel is formed via the field-directed assembly of magnetic nanomaterials during the gelation process. The novel magnetic hydrogel exhibits direction-dependent thermogenesis in an alternating magnetic field. The specific absorption rate value in the direction along the assemblies can be 2.1-fold as much as that in the direction normal to the assemblies while the heating rate is 6-8-fold. Due to the anisotropic thermogenesis, the novel magnetic hydrogel also shows a direction-dependent release of drugs that has a 3.4-fold difference between the two directions.

Iron oxide nanoparticle-mediated development of cellular gap junction crosstalk to improve mesenchymal stem cells' therapeutic efficacy for myocardial infarction

Electrophysiological phenotype development and paracrine action of mesenchymal stem cells (MSCs) are the critical factors that determine the therapeutic efficacy of MSCs for myocardial infarction (MI). In such respect, coculture of MSCs with cardiac cells has windowed a platform for cardiac priming of MSCs. Particularly, active gap junctional crosstalk of MSCs with cardiac cells in coculture has been known to play a major role in the MSC modification through coculture. Here, we report that iron oxide nanoparticles (IONPs) significantly augment the expression of connexin 43 (Cx43), a gap junction protein, of cardiomyoblasts (H9C2), which would be critical for gap junctional communication with MSCs in coculture for the generation of therapeutic potential-improved MSCs. MSCs cocultured with IONP-harboring H9C2 (cocultured MSCs: cMSCs) showed active cellular crosstalk with H9C2 and displayed significantly higher levels of electrophysiological cardiac biomarkers and a cardiac repair-favorable paracrine profile, both of which are responsible for MI repair. Accordingly, significantly improved animal survival and heart function were observed upon cMSC injection into rat MI models compared with the injection of unmodified MSCs. The present study highlights an application of IONPs in developing gap junctional crosstalk among the cells and generating cMSCs that exceeds the reparative potentials of conventional MSCs. On the basis of our finding, the potential application of IONPs can be extended in cell biology and stem cell-based therapies.

Highly efficient loading of doxorubicin in Prussian Blue nanocages for combined photothermal/chemotherapy against hepatocellular carcinoma

Doxorubicin-loaded Prussian Blue-based nanoparticles for combined photothermal/chemotherapy against hepatocellular carcinoma.

An open source image processing method to quantitatively assess tissue growth after non-invasive magnetic resonance imaging in human bone marrow stromal cell seeded 3D polymeric scaffolds

Monitoring extracellular matrix (ECM) components is one of the key methods used to determine tissue quality in three-dimensional (3D) scaffolds for regenerative medicine and clinical purposes. This is even more important when multipotent human bone marrow stromal cells (hMSCs) are used, as it could offer a method to understand in real time the dynamics of stromal cell differentiation and eventually steer it into the desired lineage. Magnetic Resonance Imaging (MRI) is a promising tool to overcome the challenge of a limited transparency in opaque 3D scaffolds. Technical limitations of MRI involve non-uniform background intensity leading to fluctuating background signals and therewith complicating quantifications on the retrieved images. We present a post-imaging processing sequence that is able to correct for this non-uniform background intensity. To test the processing sequence we investigated the use of MRI for in vitro monitoring of tissue growth in three-dimensional poly(ethylene oxide terephthalate)-poly(butylene terephthalate) (PEOT/PBT) scaffolds. Results showed that MRI, without the need to use contrast agents, is a promising non-invasive tool to quantitatively monitor ECM production and cell distribution during in vitro culture in 3D porous tissue engineered constructs.

Techniques for physicochemical characterization of nanomaterials

Advances in nanotechnology have opened up a new era of diagnosis, prevention and treatment of diseases and traumatic injuries. Nanomaterials, including those with potential for clinical applications, possess novel physicochemical properties that have an impact on their physiological interactions, from the molecular level to the systemic level. There is a lack of standardized methodologies or regulatory protocols for detection or characterization of nanomaterials. This review summarizes the techniques that are commonly used to study the size, shape, surface properties, composition, purity and stability of nanomaterials, along with their advantages and disadvantages. At present there are no FDA guidelines that have been developed specifically for nanomaterial based formulations for diagnostic or therapeutic use. There is an urgent need for standardized protocols and procedures for the characterization of nanoparticles, especially those that are intended for use as theranostics.

Glypican-3 antibody functionalized Prussian blue nanoparticles for targeted MR imaging and photothermal therapy of hepatocellular carcinoma

MRI-guided photothermal therapy is becoming a more widely accepted minimally invasive technique.

Protein A-conjugated iron oxide nanoparticles for separation ofVibrio choleraefrom water samples

Pathogen separation is of great significance for precise detection and prevention of disease outbreaks. For the first time, protein A conjugated with chitosan-coated iron oxide nanoparticles was prepared for pathogen separation at low concentrations from liquid samples.Vibrio choleraeO1 (VO1) bacteria were used for testing the effectiveness of this conjugate. Transmission electron microscopy (TEM) was used to confirm the presence of captured VO1. The results showed that, after binding with a specific antibody, the conjugate allows separation of VO1 bacteria from water samples at a concentration as low as 10 cfu mL⁻¹. Moreover, the conjugate can be used in parallel with conventional or modern diagnostic tests for quick and accurate detection of pathogens.