Microtubules as a signal hub for axon growth in response to mechanical force

Microtubules are highly polar structures and are characterized by high anisotropy and stiffness. In neurons, they play a key role in the directional transport of vesicles and organelles. In the neuronal projections called axons, they form parallel bundles, mostly oriented with the plus-end towards the axonal termination. Their physico-chemical properties have recently attracted attention as a potential candidate in sensing, processing and transducing physical signals generated by mechanical forces. Here, we discuss the main evidence supporting the role of microtubules as a signal hub for axon growth in response to a traction force. Applying a tension to the axon appears to stabilize the microtubules, which, in turn, coordinate a modulation of axonal transport, local translation and their cross-talk. We speculate on the possible mechanisms modulating microtubule dynamics under tension, based on evidence collected in neuronal and non-neuronal cell types. However, the fundamental question of the causal relationship between these mechanisms is still elusive because the mechano-sensitive element in this chain has not yet been identified.

The effect of nanomaterials on embryonic stem cell neural differentiation: a systematic review

BACKGROUND

Humans' nervous system has a limited ability to repair nerve cells, which poses substantial challenges in treating injuries and diseases. Stem cells are identified by the potential to renew their selves and develop into several cell types, making them ideal candidates for cell replacement in injured neurons. Neuronal differentiation of embryonic stem cells in modern medicine is significant. Nanomaterials have distinct advantages in directing stem cell function and tissue regeneration in this field. We attempted in this systematic review to collect data, analyze them, and report results on the effect of nanomaterials on neuronal differentiation of embryonic stem cells.

METHODS

International databases such as PubMed, Scopus, ISI Web of Science, and EMBASE were searched for available articles on the effect of nanomaterials on neuronal differentiation of embryonic stem cells (up to OCTOBER 2023). After that, screening (by title, abstract, and full text), selection, and data extraction were performed. Also, quality assessment was conducted based on the STROBE checklist.

RESULTS

In total, 1507 articles were identified and assessed, and then only 29 articles were found eligible to be included. Nine studies used 0D nanomaterials, ten used 1D nanomaterials, two reported 2D nanomaterials, and eight demonstrated the application of 3D nanomaterials. The main biomaterial in studies was polymer-based composites. Three studies reported the negative effect of nanomaterials on neural differentiation.

CONCLUSION

Neural differentiation is crucial in neurological regenerative medicine. Nanomaterials with different characteristics, particularly those cellular regulating activities and stem cell fate, have much potential in neural tissue engineering. These findings indicate a new understanding of potential applications of physicochemical cues in nerve tissue engineering.

Magnetic chitosan hydrogel induces neuronal differentiation of neural stem cells by activating RAS-dependent signal cascade

Our aim was to modulate magnetic cues to influence the differentiation of neural stem cell (NSC) into neuron during nerve repair and to explore corresponding mechanisms. Here, a magnetic hydrogel composed of chitosan matrices and magnetic nanoparticles (MNPs) with different content was prepared as the magnetic-stimulation platform to apply intrinsically-present magnetic cue and externally-applied magnetic field to NSC grown on the hydrogel. The MNP content had regulatory effects on neuronal differentiation and the MNPs-50 samples exhibited the best neuronal potential and appropriate biocompatibility in vitro, as well as accelerated the subsequent neuronal regeneration in vivo. Remarkably, the use of proteomics analysis parsed the underlying mechanism of magnetic cue-mediated neuronal differentiation form the perspective of protein corona and intracellular signal transduction. The intrinsically-present magnetic cues in hydrogel contributed to the activation of intracellular RAS-dependent signal cascades, thus facilitating neuronal differentiation. Magnetic cue-dependent changes in NSCs benefited from the upregulation of adsorbed proteins related to "neuronal differentiation", "cell-cell interaction", "receptor", "protein activation cascade", and "protein kinase activity" in the protein corona. Additionally, magnetic hydrogel acted cooperatively with the exterior magnetic field, showing further improving neurogenesis. The findings clarified the mechanism for magnetic cue-mediated neuronal differentiation, coupling protein corona and intracellular signal transduction.

Low Forces Push the Maturation of Neural Precursors into Neurons

Mechanical stimulation modulates neural development and neuronal activity. In a previous study, magnetic "nano-pulling" is proposed as a tool to generate active forces. By loading neural cells with magnetic nanoparticles (MNPs), a precise force vector is remotely generated through static magnetic fields. In the present study, human neural stem cells (NSCs) are subjected to a standard differentiation protocol, in the presence or absence of nano-pulling. Under mechanical stimulation, an increase in the length of the neural processes which showed an enrichment in microtubules, endoplasmic reticulum, and mitochondria is found. A stimulation lasting up to 82 days induces a strong remodeling at the level of synapse density and a re-organization of the neuronal network, halving the time required for the maturation of neural precursors into neurons. The MNP-loaded NSCs are then transplanted into mouse spinal cord organotypic slices, demonstrating that nano-pulling stimulates the elongation of the NSC processes and modulates their orientation even in an ex vivo model. Thus, it is shown that active mechanical stimuli can guide the outgrowth of NSCs transplanted into the spinal cord tissue. The findings suggest that mechanical forces play an important role in neuronal maturation which could be applied in regenerative medicine.

Insights into the Molecular Mechanisms Regulating Cell Behavior in Response to Magnetic Materials and Magnetic Stimulation in Stem Cell (Neurogenic) Differentiation

Magnetic materials and magnetic stimulation have gained increasing attention in tissue engineering (TE), particularly for bone and nervous tissue reconstruction. Magnetism is utilized to modulate the cell response to environmental factors and lineage specifications, which involve complex mechanisms of action. Magnetic fields and nanoparticles (MNPs) may trigger focal adhesion changes, which are further translated into the reorganization of the cytoskeleton architecture and have an impact on nuclear morphology and positioning through the activation of mechanotransduction pathways. Mechanical stress induced by magnetic stimuli translates into an elongation of cytoskeleton fibers, the activation of linker in the nucleoskeleton and cytoskeleton (LINC) complex, and nuclear envelope deformation, and finally leads to the mechanical regulation of chromatin conformational changes. As such, the internalization of MNPs with further magnetic stimulation promotes the evolution of stem cells and neurogenic differentiation, triggering significant changes in global gene expression that are mediated by histone deacetylases (e.g., HDAC 5/11), and the upregulation of noncoding RNAs (e.g., miR-106b~25). Additionally, exposure to a magnetic environment had a positive influence on neurodifferentiation through the modulation of calcium channels' activity and cyclic AMP response element-binding protein (CREB) phosphorylation. This review presents an updated and integrated perspective on the molecular mechanisms that govern the cellular response to magnetic cues, with a special focus on neurogenic differentiation and the possible utility of nervous TE, as well as the limitations of using magnetism for these applications.

Axonal plasticity in response to active forces generated through magnetic nano-pulling

Mechanical force is crucial in guiding axon outgrowth before and after synapse formation. This process is referred to as "stretch growth." However, how neurons transduce mechanical input into signaling pathways remains poorly understood. Another open question is how stretch growth is coupled in time with the intercalated addition of new mass along the entire axon. Here, we demonstrate that active mechanical force generated by magnetic nano-pulling induces remodeling of the axonal cytoskeleton. Specifically, the increase in the axonal density of microtubules induced by nano-pulling leads to an accumulation of organelles and signaling vesicles, which, in turn, promotes local translation by increasing the probability of assembly of the "translation factories." Modulation of axonal transport and local translation sustains enhanced axon outgrowth and synapse maturation.

Superparamagnetic Iron Oxide Nanoparticles and Curcumin Equally Promote Neuronal Branching Morphogenesis in the Absence of Nerve Growth Factor in PC12 Cells

Regeneration of the damaged neurons in neurological disorders and returning their activities are two of the main purposes of neuromedicine. Combination use of specific nanoformulations with a therapeutic compound could be a good candidate for neuroregeneration applications. Accordingly, this research aims to utilize the combination of curcumin, as a neurogenesis agent, with dextran-coated superparamagnetic iron oxide nanoparticles (SPIONs) to evaluate their effects on PC12 cellsʹ neuronal branching morphogenesis in the absence of nerve growth factor. Therefore, the effects of each component alone and in combination form on the cytotoxicity, neurogenesis, and neural branching morphogenesis were evaluated using MTT assay, immunofluorescence staining, and inverted microscopy, respectively. Results confirmed the effectiveness of the biocompatible iron oxide nanoparticles (with a size of about 100 nm) in improving the percentage of neural branching (p < 0.01) in PC12 cells. In addition, the combination use of these nanoparticles with curcumin could enhance the effect of curcumin on neurogenesis (p < 0.01). These results suggest that SPIONs in combination with curcumin could act as an inducing factor on PC12 neurogenesis in the absence of nerve growth factor and could offer a novel therapeutic approach to the treatment of neurodegenerative diseases.

Magnetic nanocomposites for biomedical applications

Tissue engineering and regenerative medicine have solved numerous problems related to the repair and regeneration of damaged organs and tissues arising from aging, illnesses, and injuries. Nanotechnology has further aided tissue regeneration science and has provided outstanding opportunities to help disease diagnosis as well as treat damaged tissues. Based on the most recent findings, magnetic nanostructures (MNSs), in particular, have emerged as promising materials for detecting, directing, and supporting tissue regeneration. There have been many reports concerning the role of these nano-building blocks in the regeneration of both soft and hard tissues, but the subject has not been extensively reviewed. Here, we review, classify, and discuss various synthesis strategies for novel MNSs used in medicine. Advanced applications of magnetic nanocomposites (MG-NCs), specifically magnetic nanostructures, are further systematically reviewed. In addition, the scientific and technical aspects of MG-NC used in medicine are discussed considering the requirements for the field. In summary, this review highlights the numerous opportunities and challenges associated with the use of MG-NCs as smart nanocomposites (NCs) in tissue engineering and regenerative medicine.

SPION based magnetic PLGA nanofibers for neural differentiation of mesenchymal stem cells

Recently, magnetic platforms have been widely investigated in diagnostic, therapeutic and research applications due to certain properties, such as cell and tissue tracking and imaging, thermal therapy and being dirigible. In this study, the incorporation of magnetic nanoparticles (MNPs) in nanofibers has been proposed to combine the advantages of both nanofibers and MNPs to induce neural differentiation of mesenchymal stem cells. Magnetic poly (lactic-co-glycolic acid) nanofibers (containing 0%, 5% and 10% SPION) were fabricated and utilized as the matrix for the differentiation of mesenchymal stem cells (MSCs). Morphological, magnetic and mechanical properties were analyzed using FESEM, VSM and tensile test, respectively. The expression of neural markers (TUJ-1, NSE, MAP-2) was assessed quantitative and qualitatively utilizing RT-PCR and immunocytochemistry. Results confirmed the incorporation of MNPs in nanofibrous scaffold, presenting a saturation magnetization of 9.73 emu g^-1. Also, with increase in magnetic particle concentration (0%-10%), tensile strength increased from 4.08 to 5.85 MPa, whereas the percentage of elongation decreased. TUJ-1 expression was 3.8 and 1.8 fold for 10% and 5% magnetic scaffold (versus non-magnetic scaffold) respectively, and the expression of NSE was 6.3 and 1.2-fold for 10% and 5%, respectively. Consequently, it seems that incorporation of magnetic biomaterial can promote the neural differentiation of MSCs, during which the augmentation of super paramagnetic iron oxide concentration from 0% to 10% accelerates the neural differentiation process.

DNA/Magnetic Nanoparticles Composite to Attenuate Glass Surface Nanotopography for Enhanced Mesenchymal Stem Cell Differentiation

Mesenchymal stem cells (MSCs) have extensive pluripotent potential to differentiate into various cell types, and thus they are an important tool for regenerative medicine and biomedical research. In this work, the differentiation of hTERT-transduced adipose-derived MSCs (hMSCs) into chondrocytes, adipocytes and osteoblasts on substrates with nanotopography generated by magnetic iron oxide nanoparticles (MNPs) and DNA was investigated. Citrate-stabilized MNPs were synthesized by the chemical co-precipitation method and sized around 10 nm according to microscopy studies. It was shown that MNPs@DNA coatings induced chondrogenesis and osteogenesis in hTERT-transduced MSCs. The cells had normal morphology and distribution of actin filaments. An increase in the concentration of magnetic nanoparticles resulted in a higher surface roughness and reduced the adhesion of cells to the substrate. A glass substrate modified with magnetic nanoparticles and DNA induced active chondrogenesis of hTERT-transduced MSC in a twice-diluted differentiation-inducing growth medium, suggesting the possible use of nanostructured MNPs@DNA coatings to obtain differentiated cells at a reduced level of growth factors.

Droplet microfluidic devices for organized stem cell differentiation into germ cells: capabilities and challenges

Demystifying the mechanisms that underlie germline development and gamete production is critical for expanding advanced therapies for infertile couples who cannot benefit from current infertility treatments. However, the low number of germ cells, particularly in the early stages of development, represents a serious challenge in obtaining sufficient materials required for research purposes. In this regard, pluripotent stem cells (PSCs) have provided an opportunity for producing an unlimited source of germ cells in vitro. Achieving this ambition is highly dependent on accurate stem cell niche reconstitution which is achievable through applying advanced cell engineering approaches. Recently, hydrogel microparticles (HMPs), as either microcarriers or microcapsules, have shown promising potential in providing an excellent 3-dimensional (3D) biomimetic microenvironment alongside the systematic bioactive agent delivery. In this review, recent studies of utilizing various HMP-based cell engineering strategies for appropriate niche reconstitution and efficient in vitro differentiation are highlighted with a special focus on the capabilities of droplet-based microfluidic (DBM) technology. We believe that a deep understanding of the current limitations and potentials of the DBM systems in integration with stem cell biology provides a bright future for germ cell research.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12551-021-00907-5.

Photoacoustic and magnetic resonance imaging-based gene and photothermal therapy using mesoporous nanoagents

The integration of photothermal therapy (PTT) with gene therapy (GT) in a single nanoscale platform demonstrates great potential in cancer therapy. Porous iron oxide nanoagents (PIONs) are widely used as magnetic nanoagents in the drug delivery field and also serve as a photothermal nanoagent for photothermal therapy. However, the therapeutic efficacy of PIONs-mediated GT has not been studied. The long noncoding RNA (lncRNA) CRYBG3 (LNC CRYBG3), a lncRNA induced by heavy ion irradiation in lung cancer cells, has been reported to directly bind to globular actin (G-actin) and cause degradation of cytoskeleton and blocking of cytokinesis, thus indicating its potential for use in GT by simulating the effect of heavy ion irradiation and functioning as an antitumor drug. In the present study, we investigated the possibility of combining PIONs-mediated PTT and LNC CRYBG3-mediated GT to destroy non-small cell lung cancer (NSCLC) cells both in vitro and in vivo. The combination therapy showed a high cancer cell killing efficacy, and the cure rate was better than that achieved using PTT or GT alone. Moreover, as a type of magnetic nanoagent, PIONs can be used for magnetic resonance imaging (MRI) and photoacoustic imaging (PAI) both in vitro and in vivo. These findings indicate that the new combination therapy has high potential for cancer treatment.

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LNC CRYBG3 induced by heavy ion irradiation can cause cytoskeleton degradation and function as an antitumor drug.

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pcDNA3.1-LNC CRYBG3 delivered by PIONs can escape from lysosomes to facilitate plasmid release when exposed to NIR.

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The combination of PIONs-mediated PTT and LNC CRYBG3-mediated GT presents both diagnosis and treatment potential.

Poly(vinyl alcohol-co-itaconic acid) hydrogels grafted with several designed peptides for human pluripotent stem cell culture and differentiation into cardiomyocytes

We developed poly(vinyl alcohol-co-itaconic acid) (PV) hydrogels grafted with laminin-derived peptides that had different joint segments and several specific designs, including dual chain motifs. PV hydrogels grafted with a peptide derived from laminin-β4 (PMQKMRGDVFSP) containing a joint segment, dual chain motif and cationic amino acid insertion could attach human pluripotent stem (hPS) cells and promoted high expansion folds in long-term culture (over 10 passages) with low differentiation rates, whereas hPS cells attached poorly on PV hydrogels grafted with laminin-α5 peptides that had joint segments with and without a cationic amino acid or on PV hydrogels grafted with laminin-β4 peptides containing the joint segment only. The inclusion of a cationic amino acid in the laminin-β4 peptide was critical for hPS cell attachment on PV hydrogels, which contributed to the zeta potential shifting to higher values (3-4 mV enhancement). The novel peptide segment-grafted PV hydrogels developed in this study supported hPS cell proliferation, which induced better hPS cell expansion than recombinant vitronectin-coated dishes (gold standard of hPS cell culture dishes) in xeno-free culture conditions. After long-term culture on peptide-grafted hydrogels, hPS cells could be induced to differentiate into specific lineages of cells, such as cardiomyocytes, with high efficiency.

Progress and prospects of magnetic iron oxide nanoparticles in biomedical applications: A review

Nanoscience has been considered as one of the most substantial research in modern science. The utilization of nanoparticle (NP) materials provides numerous advantages in biomedical applications due to their unique properties. Among various types of nanoparticles, the magnetic nanoparticles (MNPs) of iron oxide possess intrinsic features, which have been efficiently exploited for biomedical purposes including drug delivery, magnetic resonance imaging, Magnetic-activated cell sorting, nanobiosensors, hyperthermia, and tissue engineering and regenerative medicine. The size and shape of nanostructures are the main factors affecting the physicochemical features of superparamagnetic iron oxide nanoparticles, which play an important role in the improvement of MNP properties, and can be controlled by appropriate synthesis strategies. On the other hand, the proper modification and functionalization of the surface of iron oxide nanoparticles have significant effects on the improvement of physicochemical and mechanical features, biocompatibility, stability, and surface activity of MNPs. This review focuses on popular methods of fabrication, beneficial surface coatings with regard to the main required features for their biomedical use, as well as new applications.

Neural priming of adipose-derived stem cells by cell-imprinted substrates

Cell-imprinting technology is a novel method for directing stem cell fate using substrates molded from target cells. Here, we fabricated and studied cell-imprinted substrates for neural priming in human adipose-derived stem cells in the absence of chemical cues. We molded polydimethylsiloxane silicone substrates on fixed differentiated neural progenitor cells (ReNcell^TMVM). The ReNcell^TMcell line consists of immortalized human neural progenitor cells that are capable to differentiate into neural cells. The fabricated cell-imprinted silicone substrates represent the geometrical micro- and nanotopology of the target cell morphology. During the molding procedure, no transfer of cellular proteins was detectable. In the first test with undifferentiated ReNcell^TMVM cells, the cell-imprinted substrates could accelerate neural differentiation. With adipose-derived stem cells cultivated on the imprinted substrates, we observed modifications of cell morphology, shifting from spread to elongated shape. Both immunofluorescence and quantitative gene expression analysis showed upregulation of neural stem cell and early neuronal markers. Our study, for the first time, demonstrated the effectiveness of cell-imprinted substrates for neural priming of adipose-derived stem cells for regenerative medicine applications.

Magnetic nanocomplexes for gene delivery applications

Gene delivery is an indispensable technique for various biomedical applications such as gene therapy, stem cell engineering and gene editing. Recently, magnetic nanoparticles (MNPs) have received increasing attention for their use in promoting gene delivery efficiency. Under magnetic attraction, gene delivery efficiency using viral or nonviral gene carriers could be universally enhanced. Besides, magnetic nanoparticles could be utilized in magnetic resonance imaging or magnetic hyperthermia therapy, providing extra theranostic opportunities. In this review, recent research integrating MNPs with a viral or nonviral gene vector is summarized from both technical and application perspectives. Applications of MNPs in cutting-edge research technologies, such as biomimetic cell membrane nano-gene carriers, exosome-based gene delivery, cell-based drug delivery systems or CRISPR/Cas9 gene editing, are also discussed.

Thermoresponsive surfaces designed for the proliferation and differentiation of human pluripotent stem cells

Thermoresponsive surfaces enable the detachment of cells or cell sheets by decreasing the temperature of the surface when harvesting the cells. However, human pluripotent stem cells (hPSCs), such as embryonic stem cells and induced pluripotent stem cells, cannot be directly cultured on a thermoresponsive surface; hPSCs need a specific extracellular matrix to bind to the integrin receptors on their surfaces. We prepared a thermoresponsive surface by using poly(N-isopropylacrylamide-co-butylacrylate) and recombinant vitronectin to provide an optimal coating concentration for the hPSC culture. hPSCs can be cultured on the same thermoresponsive surface for 5 passages by partial detachment of the cells from the surface by decreasing the temperature for 30 min; then, the remaining hPSCs were subsequently cultured on the same dishes following the addition of new cultivation media. The detached cells, even after continual culture for five passages, showed high pluripotency, the ability to differentiate into cells derived from the 3 germ layers and the ability to undergo cardiac differentiation.

Fe/Mn multilayer nanowires as dual mode T1 -T2 magnetic resonance imaging contrast agents

To overcome the negative contrast limitations, and to improve the sensitivity of the magnetic resonance signals, the mesoporous silica coated Fe/Mn multilayered nanowires (NWs) were used as a T₁ -T₂ dual-mode contrast agents (CAs). The single component Fe and Mn NWs, and Fe/Mn multilayer NWs were synthesized by electrodeposition in the homemade anodic aluminum oxide (AAO) templates with the aperture of about 30 nm. The structural characterization and morphology of single component and multisegmented NWs was done by X-ray diffraction and transmission electron microscopy. The elemental composition of Fe/Mn multilayerd NWs was confirmed by energy-dispersive X-ray and energy-dispersive spectrometer. Vibrating sample magnetometer was used to test the magnetic properties, and 1.5 T magnetic resonance imaging (MRI) scanner was used to measure the relaxation efficiency. Importantly, the MRI study indicated that the Fe/Mn multilayer NWs showed a significant T₁ -T₂ imaging effect, and have longitudinal relaxivity (r₁ ) value, that is, 1.25 ± 0.0329 × 10^-4 μM^-1 s^-1 and transverse relaxivity (r₂ ), that is, 5.13 ± 0.123 × 10^-4 μM^-1 s^-1 , which was two times of r₁ value (0.654 ± 0.00899 × 10^-4 μM^-1 s^-1 ) of Mn NWs, and r₂ value (2.96 ± 0.0415 × 10^-4 μM^-1 s^-1 ) of Fe NWs. Hence, Fe/Mn multilayer NWs have potential to be used as T₁ -T₂ dual-mode CAs.

Ligand-free upconversion nanoparticles for cell labeling and their effects on stem cell differentiation

Recently, the wide application of upconversion nanoparticles (UCNPs) in the field of bioimaging has raised the requirement of biocompatibility. Current cytocompatibility studies on UCNPs mainly focus on cancer cells; however, their potential effects on normal cells are rarely addressed. Herein, the cellular effects of a trace amount of ligand-free NaYF₄:Yb/Er nanocrystals on the differentiation of rat bone mesenchymal stem cells (rBMSCs) were investigated. First, due to their excellent upconversion fluorescent properties, the cellular uptake of ligand-free NaYF₄:Yb/Er nanocrystals was confirmed by confocal laser scanning microscopy, and a homogeneous cytoplasmic distribution was imaged. Second, the viability of the rBMSCs cultured with a series of concentrations of nanoparticles (0, 30, 300, and 3000 ng ml^-1) was evaluated, and a dose threshold was determined. Third, the effects of ligand-free NaYF₄:Yb/Er nanocrystals on the osteogenesis of the rBMSCs were intensively characterized. The alkaline phosphatase activity assay, quantitative real time polymerase chain reaction for related osteogenic genes, and immunofluorescence staining of specific biomarkers and mineral deposits demonstrated that the ligand-free NaYF₄:Yb/Er nanocrystals at a proper concentration can enhance osteogenic differentiation. Finally, intracytoplasmic lipid detection showed that the adipogenic differentiation of rBMSCs might be inhibited in the presence of ligand-free NaYF₄:Yb/Er nanocrystals. Meanwhile, these results showed that the effects of ligand-free NaYF₄:Yb/Er nanocrystals on rBMSCs were concentration-dependent and reciprocal between osteogenic and adipogenic differentiation. This work provides new insights into the exploring the biocompatibility of UCNPs and will benefit the research community engaged in nanotechnology and biomedicine.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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