Magnetogenetics: remote activation of cellular functions triggered by magnetic switches

Control of cardiac waves in human iPSC-CM syncytia by a Halbach array and magnetic nanoparticles

The Halbach array, originally developed for particle accelerators, is a compact arrangement of permanent magnets that creates well-defined magnetic fields without heating. Here, we demonstrate its use for modulating the speed of electromechanical waves in cardiac syncytia of human stem cell-derived cardiomyocytes. At 40-50 mT magnetic field strength, a cylindrical dipolar Halbach array boosted the conduction velocity (CV) by up to 25% when the magnetic field was co-aligned with the electromechanical wave (but not when perpendicular to it). To observe the effects, a short-term incubation of the cardiac cell constructs with non-targeted magnetic nanoparticles (mNPs) was sufficient. This led to increased CV anisotropy, and effects were most pronounced at slower pacing rates. Instantaneous formation and rearrangement of elongated mNP clusters upon magnetic-field rotation was seen, creating dynamic structural anisotropy that may have contributed to the directional CV effects. This approach may be useful for anti-arrhythmic control of cardiac waves.

Magnetically targeted delivery of probiotics for controlled residence and accumulation in the intestine

The effectiveness of orally delivered probiotics in treating gastrointestinal diseases is restricted by inadequate gut retention. In this study, we present a magnetically controlled strategy for probiotic delivery, which enables controlled accumulation and residence of probiotics in the intestine. The magnetically controlled probiotic is established by attaching amino-modified iron oxide (Fe3O4-NH3+ NPs) to polydopamine-coated Lacticaseibacillus rhamnosus GG (LGG@P) through electrostatic self-assembly and named as LGG@P@Fe3O4. In a simulated gastrointestinal environment, LGG@P@Fe3O4 maintains both structural stability and probiotic viability. Furthermore, the LGG@P@Fe3O4 clusters can be easily manipulated by an external magnetic field, inducing directional movement and aggregation. In vitro simulations demonstrated significant accumulation and retention of LGG@P@Fe3O4 under a magnetic field, with the optical density (OD) value of the suspension decreasing from ∼1.17 to ∼0.29. In contrast, the OD value of the suspension without a magnetic field remained at its original level (∼1.15). In a mouse model with intragastrically administered LGG@P@Fe3O4, the group exposed to a magnet exhibited stronger gut fluorescence after 24 h. The magnetically controlled probiotic delivery strategy offers an easy manufacturing and feasible method to enhance the effectiveness of probiotics in treating gastrointestinal diseases.

Intracellular Proteins Targeting with Bi-Functionalized Magnetic Nanoparticles Following their Endosomal Escape

The specific targeting of intracellular proteins or organelles by magnetic nanoparticles (MNPs) is a major challenge in nanomedicine, as most MNPs are internalized by cells through endocytosis and remain trapped inside small intracellular vesicles, limiting their ability to reach intracellular components. Furthermore, this phenomenon limits their heating capacity in magnetic hyperthermia, and therefore their potential for cancer treatment. This study presents a strategy based on an original double functionalization of MNPs, with polyhistidine peptides (PHPs) triggering endosomal escape and antibodies targeting specific cytosolic proteins. Negatively charged γ-Fe2O3@SiO2 MNPs with diameter smaller than 50 nm are functionalized with zwitterionic and thiol groups at their surface. These sulfhydryl groups are used to graft PHPs through a labile link, allowing the peptide to be released from the MNPs' surface once in the cytosolic reductive environment. This severing avoids any interaction between these peptides and intracellular components, which can hinder MNPs' intracellular mobility. The second MNPs' surface functionalization is performed through a non-labile link with antibodies targeting specific cytosolic proteins, namely HSP27 thermosensitive proteins, for this inaugural proof of concept. Bi-functionalized MNPs are able to successfully target the intracellular protein of interest, opening the door to promising biomedical applications of MNPs, in cellular engineering and magnetic hyperthermia.

Electro- and Magneto-Active Biomaterials for Diabetic Tissue Repair: Advantages and Applications

The diabetic tissue repair process is frequently hindered by persistent inflammation, infection risks, and a compromised tissue microenvironment, which lead to delayed wound healing and significantly impact the quality of life for diabetic patients. Electromagnetic biomaterials offer a promising solution by enabling the intelligent detection of diabetic wounds through electric and magnetic effects, while simultaneously improving the pathological microenvironment by reducing oxidative stress, modulating immune responses, and exhibiting antibacterial action. Additionally, these materials inherently promote tissue regeneration by regulating cellular behavior and facilitating vascular and neural repair. Compared to traditional biomaterials, electromagnetic biomaterials provide advantages such as noninvasiveness, deep tissue penetration, intelligent responsiveness, and multi-stimuli synergy, demonstrating significant potential to overcome the challenges of diabetic tissue repair. This review comprehensively examines the superiority of electromagnetic biomaterials in diabetic tissue repair, elucidates the underlying biological mechanisms, and discusses specific design strategies and applications tailored to the pathological characteristics of diabetic wounds, with a focus on skin wound healing and bone defect repair. By addressing current limitations and pursuing multi-faceted strategies, electromagnetic biomaterials hold significant potential to improve clinical outcomes and enhance the quality of life for diabetic patients.

Modulation of GABAergic neurons in acute epilepsy using sonogenetics

Epilepsy, a neurological disorder caused by hypersynchronous neural disturbances, has traditionally been treated with surgery, pharmacotherapy, and neuromodulation techniques such as deep brain stimulation and vagus nerve stimulation. However, these methods are often limited by invasiveness, off-target effects, and poor resolution. We present a noninvasive alternative utilizing sonogenetics to selectively stimulate γ-aminobutyric acid (GABA)ergic neurons in the amygdala through engineered auditory-sensing protein, mPrestin (N7T, N308S), in a pentylenetetrazole-induced rat model. Activation of GABAergic neurons induced by the sonication with 0.5-MHz transcranial ultrasound can modulate epileptiform activity by 50 %. Electrophysiological recordings confirmed effective neuromodulation and persistent seizure suppression up to 60 min post-treatment without tissue damage, inflammation, or apoptosis. This sonogenetic approach offers a promising, safe method for epilepsy management by targeting GABAergic neurons.

Programming mammalian cell behaviors by physical cues

In recent decades, the field of synthetic biology has witnessed remarkable progress, driving advances in both research and practical applications. One pivotal area of development involves the design of transgene switches capable of precisely regulating specified outputs and controlling cell behaviors in response to physical cues, which encompass light, magnetic fields, temperature, mechanical forces, ultrasound, and electricity. In this review, we delve into the cutting-edge progress made in the field of physically controlled protein expression in engineered mammalian cells, exploring the diverse genetic tools and synthetic strategies available for engineering targeting cells to sense these physical cues and generate the desired outputs accordingly. We discuss the precision and efficiency limitations inherent in these tools, while also highlighting their immense potential for therapeutic applications.

Green Dentistry in Oral Cancer Treatment Using Biosynthesis Superparamagnetic Iron Oxide Nanoparticles: A Systematic Review

Oral cancer is a worldwide health issue with high incidence and mortality, demands an effective treatment to improve patient prognosis. Superparamagnetic iron oxide nanoparticles (SPIONs) emerged as a candidate for oral cancer treatment due to their unique attributes, enabling a synergistic combination with its drug-delivery capabilities and hyperthermia when exposed to magnetic fields. SPIONs can be synthesized using biopolymers from agricultural waste like lignin from paddy, which produce biogenic nano iron oxide with superparamagnetic and antioxidant effects. In addition, lignin also acts as a stabilizing agent in creating SPIONs. This study aimed to explore how agricultural waste could be used to prepare SPIONs using the green synthesis method and to evaluate its potential for oral cancer specifically focusing on its effectiveness, side effects, biocompatibility, and toxicity. A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol. PubMed, EBSCO, and Scopus databases were exploited in the selection of articles published within the last decade. This study quality assessment uses OHAT for critical appraisal tools. Only 10 studies met the inclusion criteria. The findings suggest that the use of agricultural waste in the preparation of SPIONs not only holds potency for oral cancer treatment through drug delivery and hyperthermia but also aligns with the concept of green dentistry. SPIONs as a treatment modality for oral cancer have demonstrated notable effectiveness and versatility. This study provides robust evidence supporting green dentistry by using agricultural waste in the preparation and formulation of SPIONs for managing oral cancer. Its multifunctional nature and ability to enhance treatment efficacy while minimizing adverse effects on healthy tissues highlights the potency of SPION-based oral cancer treatments.

Temporal and spatial resolution of magnetosome degradation at the subcellular level in a 3D lung carcinoma model

Magnetic nanoparticles offer many exciting possibilities in biomedicine, from cell imaging to cancer treatment. One of the currently researched nanoparticles are magnetosomes, magnetite nanoparticles of high chemical purity synthesized by magnetotactic bacteria. Despite their therapeutic potential, very little is known about their degradation in human cells, and even less so of their degradation within tumours. In an effort to explore the potential of magnetosomes for cancer treatment, we have explored their degradation process in a 3D human lung carcinoma model at the subcellular level and with nanometre scale resolution. We have used state of the art hard X-ray probes (nano-XANES and nano-XRF), which allow for identification of distinct iron phases in each region of the cell. Our results reveal the progression of magnetite oxidation to maghemite within magnetosomes, and the biosynthesis of magnetite and ferrihydrite by ferritin.

In vivo magnetogenetics for cell-type-specific targeting and modulation of brain circuits

Neuromodulation technologies are crucial for investigating neuronal connectivity and brain function. Magnetic neuromodulation offers wireless and remote deep brain stimulations that are lacking in optogenetic- and wired-electrode-based tools. However, due to the limited understanding of working principles and poorly designed magnetic operating systems, earlier magnetic approaches have yet to be utilized. Furthermore, despite its importance in neuroscience research, cell-type-specific magnetic neuromodulation has remained elusive. Here we present a nanomaterials-based magnetogenetic toolbox, in conjunction with Cre-loxP technology, to selectively activate genetically encoded Piezo1 ion channels in targeted neuronal populations via torque generated by the nanomagnetic actuators in vitro and in vivo. We demonstrate this cell-type-targeting magnetic approach for remote and spatiotemporal precise control of deep brain neural activity in multiple behavioural models, such as bidirectional feeding control, long-term neuromodulation for weight control in obese mice and wireless modulation of social behaviours in multiple mice in the same physical space. Our study demonstrates the potential of cell-type-specific magnetogenetics as an effective and reliable research tool for life sciences, especially in wireless, long-term and freely behaving animals.

Bioluminescence-optogenetics-mediated gene therapy in a sleep-disordered breathing mouse model

Obstructive sleep apnea (OSA) incurs a huge individual, societal, and economic burden. Specific and selective targeting of hypoglossal motor neurons could be an effective means to treat OSA. Bioluminescent-optogenetics (BL-OG) is a novel genetic regulatory approach in which luminopsins, fusion proteins of light-generating luciferase and light-sensing ion channels, increase neuronal excitability when exposed to a suitable substrate. Here we develop and validate the feasibility of BL-OG for sleep-disordered breathing (SDB). Upon confirming that diet-induced obese mice represent an excellent SDB model, we employed a method of targeting the hypoglossal nucleus (12 N) by peripherally injecting retrogradely transported rAAV2/Retro. With AAV transduction, the eLMO3 protein is expressed in hypoglossal motor neurons (HMN); administration of CTZ results in production of bioluminescence that in turn activates the tethered channelrhodopsin, leading to an increase in the firing of HMN and a 2.7 ± 0.8-fold increase in phasic activity of the genioglossus muscle, a 7.6 ± 1.8-fold increase in tonic activity, and improvements in hypoventilation and apnea index without impacting sleep structure. This is therefore the first study to leverage the rAAV2/Retro vector to execute the BL-OG approach in SDB, which amplified genioglossus muscle discharge activity and increased airflow in mice after activation. This study marks the pioneering utilization of BL-OG in SDB research.

Antioxidant, Antitumoral, Antimicrobial, and Prebiotic Activity of Magnetite Nanoparticles Loaded with Bee Pollen/Bee Bread Extracts and 5-Fluorouracil

The gut microbiota dysbiosis that often occurs in cancer therapy requires more efficient treatment options to be developed. In this concern, the present research approach is to develop drug delivery systems based on magnetite nanoparticles (MNPs) as nanocarriers for bioactive compounds. First, MNPs were synthesized through the spraying-assisted coprecipitation method, followed by loading bee pollen or bee bread extracts and an antitumoral drug (5-fluorouracil/5-FU). The loaded-MNPs were morphologically and structurally characterized through transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Dynamic Light Scattering (DLS), and thermogravimetric analysis. UV-Vis spectroscopy was applied to establish the release profiles and antioxidant activity. Furthermore, the antibacterial and antitumoral activity of loaded-MNPs was assessed. The results demonstrate that MNPs with antioxidant, antibacterial, antiproliferative, and prebiotic properties are obtained. Moreover, the data highlight the improvement of 5-FU antibacterial activity by loading on the MNPs' surface and the synergistic effects between the anticancer drug and phenolic compounds (PCs). In addition, the prolonged release behavior of PCs for many hours (70-75 h) after the release of 5-FU from the developed nanocarriers is an advantage, at least from the point of view of the antioxidant activity of PCs. Considering the enhancement of L. rhamnosus MF9 growth and antitumoral activity, this study developed promising drug delivery alternatives for colorectal cancer therapy.

Magnetic colloidal nanoformulations to remotely trigger mechanotransduction for osteogenic differentiation

Nowadays, diseases associated with an ageing population, such as osteoporosis, require the development of new biomedical approaches to bone regeneration. In this regard, mechanotransduction has emerged as a discipline within the field of bone tissue engineering. Herein, we have tested the efficacy of superparamagnetic iron oxide nanoparticles (SPIONs), obtained by the thermal decomposition method, with an average size of 13 nm, when exposed to the application of an external magnetic field for mechanotransduction in human bone marrow-derived mesenchymal stem cells (hBM-MSCs). The SPIONs were functionalized with an Arg-Gly-Asp (RGD) peptide as ligand to target integrin receptors on cell membrane and used in colloidal state. Then, a comprehensive and comparative bioanalytical characterization of non-targeted versus targeted SPIONs was performed in terms of biocompatibility, cell uptake pathways and mechanotransduction effect, demonstrating the osteogenic differentiation of hBM-MSCs. A key conclusion derived from this research is that when the magnetic stimulus is applied in the first 30 min of the in vitro assay, i.e., when the nanoparticles come into contact with the cell membrane surface to initiate endocytic pathways, a successful mechanotransduction effect is observed. Thus, under the application of a magnetic field, there was a significant increase in runt-related transcription factor 2 (Runx2) and alkaline phosphatase (ALP) gene expression as well as ALP activity, when cells were exposed to RGD-functionalized SPIONs, demonstrating osteogenic differentiation. These findings open new expectations for the use of remotely activated mechanotransduction using targeted magnetic colloidal nanoformulations for osteogenic differentiation by drug-free cell therapy using minimally invasive techniques in cases of bone loss.

Magnetogenetics as a promising tool for controlling cellular signaling pathways

Magnetogenetics emerges as a transformative approach for modulating cellular signaling pathways through the strategic application of magnetic fields and nanoparticles. This technique leverages the unique properties of magnetic nanoparticles (MNPs) to induce mechanical or thermal stimuli within cells, facilitating the activation of mechano- and thermosensitive proteins without the need for traditional ligand-receptor interactions. Unlike traditional modalities that often require invasive interventions and lack precision in targeting specific cellular functions, magnetogenetics offers a non-invasive alternative with the capacity for deep tissue penetration and the potential for targeting a broad spectrum of cellular processes. This review underscores magnetogenetics' broad applicability, from steering stem cell differentiation to manipulating neuronal activity and immune responses, highlighting its potential in regenerative medicine, neuroscience, and cancer therapy. Furthermore, the review explores the challenges and future directions of magnetogenetics, including the development of genetically programmed magnetic nanoparticles and the integration of magnetic field-sensitive cells for in vivo applications. Magnetogenetics stands at the forefront of cellular manipulation technologies, offering novel insights into cellular signaling and opening new avenues for therapeutic interventions.

Magnetic Modulation of Biochemical Synthesis in Synthetic Cells

Synthetic cells can be constructed from diverse molecular components, without the design constraints associated with modifying 'living' biological systems. This can be exploited to generate cells with abiotic components, creating functionalities absent in biology. One example is magnetic responsiveness, the activation and modulation of encapsulated biochemical processes using a magnetic field, which is absent from existing synthetic cell designs. This is a critical oversight, as magnetic fields are uniquely bio-orthogonal, noninvasive, and highly penetrative. Here, we address this by producing artificial magneto-responsive organelles by coupling thermoresponsive membranes with hyperthermic Fe3O4 nanoparticles and embedding them in synthetic cells. Combining these systems enables synthetic cell microreactors to be built using a nested vesicle architecture, which can respond to alternating magnetic fields through in situ enzymatic catalysis. We also demonstrate the modulation of biochemical reactions by using different magnetic field strengths and the potential to tune the system using different lipid compositions. This platform could unlock a wide range of applications for synthetic cells as programmable micromachines in biomedicine and biotechnology.

Hybrid hydrogels support neural cell culture development under magnetic actuation at high frequency

The combination of hydrogels and magnetic nanoparticles, scarcely explored to date, offers a wide range of possibilities for innovative therapies. Herein, we have designed hybrid 3D matrices integrating natural polymers, such as collagen, chitosan (CHI) and hyaluronic acid (HA), to provide soft and flexible 3D networks mimicking the extracellular matrix of natural tissues, and iron oxide nanoparticles (IONPs) that deliver localized heat when exposed to an alternating magnetic field (AMF). First, colloidally stable nanoparticles with a hydrodynamic radius of ∼20 nm were synthesized and coated with either CHI (NPCHI) or HA (NPHA). Then, collagen hydrogels were homogeneously loaded with these coated-IONPs resulting in soft (E0 ∼ 2.6 kPa), biodegradable and magnetically responsive matrices. Polymer-coated IONPs in suspension preserved primary neural cell viability and neural differentiation even at the highest dose (0.1 mg Fe/mL), regardless of the coating, even boosting neuronal interconnectivity at lower doses. Magnetic hydrogels maintained high neural cell viability and sustained the formation of highly interconnected and differentiated neuronal networks. Interestingly, those hydrogels loaded with the highest dose of NPHA (0.25 mgFe/mg polymer) significantly impaired non-neuronal differentiation with respect to those with NPCHI. When evaluated under AMF, cell viability slightly diminished in comparison with control hydrogels magnetically stimulated, but not compared to their counterparts without stimulation. Neuronal differentiation under AMF was only affected on collagen hydrogels with the highest dose of NPHA, while non-neuronal differentiation regained control values. Taken together, NPCHI-loaded hydrogels displayed a superior performance, maybe benefited from their higher nanomechanical fluidity. STATEMENT OF SIGNIFICANCE: Hydrogels and magnetic nanoparticles are undoubtedly useful biomaterials for biomedical applications. Nonetheless, the combination of both has been scarcely explored to date. In this study, we have designed hybrid 3D matrices integrating both components as promising magnetically responsive platforms for neural therapeutics. The resulting collagen scaffolds were soft (E0 ∼ 2.6 kPa) and biodegradable hydrogels with capacity to respond to external magnetic stimuli. Primary neural cells proved to grow on these substrates, preserving high viability and neuronal differentiation percentages even under the application of a high-frequency alternating magnetic field. Importantly, those hydrogels loaded with chitosan-coated iron oxide nanoparticles displayed a superior performance, likely related to their higher nanomechanical fluidity.

Exploring the host range for genetic transfer of magnetic organelle biosynthesis

Magnetosomes produced by magnetotactic bacteria have great potential for application in biotechnology and medicine due to their unique physicochemical properties and high biocompatibility. Attempts to transfer the genes for magnetosome biosynthesis into non-magnetic organisms have had mixed results. Here we report on a systematic study to identify key components needed for magnetosome biosynthesis after gene transfer. We transfer magnetosome genes to 25 proteobacterial hosts, generating seven new magnetosome-producing strains. We characterize the recombinant magnetosomes produced by these strains and demonstrate that denitrification and anaerobic photosynthesis are linked to the ability to synthesize magnetosomes upon the gene transfer. In addition, we show that the number of magnetosomes synthesized by a foreign host negatively correlates with the guanine-cytosine content difference between the host and the gene donor. Our findings have profound implications for the generation of magnetized living cells and the potential for transgenic biogenic magnetic nanoparticle production.

Genetically encoded mediators for sonogenetics and their applications in neuromodulation

Sonogenetics is an emerging approach that harnesses ultrasound for the manipulation of genetically modified cells. The great penetrability of ultrasound waves enables the non-invasive application of external stimuli to deep tissues, particularly advantageous for brain stimulation. Genetically encoded ultrasound mediators, a set of proteins that respond to ultrasound-induced bio-effects, play a critical role in determining the effectiveness and applications of sonogenetics. In this context, we will provide an overview of these ultrasound-responsive mediators, delve into the molecular mechanisms governing their response to ultrasound stimulation, and summarize their applications in neuromodulation.

A Simple and Versatile Strategy for Oriented Immobilization of His-Tagged Proteins on Magnetic Nanoparticles

Oriented and covalent immobilization of proteins on magnetic nanoparticles (MNPs) is particularly challenging as it requires both the functionality of the protein and the colloidal stability of the MNPs to be preserved. Here, we describe a simple, straightforward, and efficient strategy for MNP functionalization with proteins using metal affinity binding. Our method involves a single-step process where MNPs are functionalized using a preformed, ready-to-use nitrilotriacetic acid-divalent metal cation (NTA-M2+) complex and polyethylene glycol (PEG) molecules. As a proof-of-concept, we demonstrate the oriented immobilization of a recombinant cadherin fragment engineered with a hexahistidine tag (6His-tag) onto the MNPs. Our developed methodology is simple and direct, enabling the oriented bioconjugation of His-tagged cadherins to MNPs while preserving protein functionality and the colloidal stability of the MNPs, and could be extended to other proteins expressing a polyhistidine tag. When compared to the traditional method where NTA is first conjugated to the MNPs and afterward free metal ions are added to form the complex, this novel strategy results in a higher functionalization efficiency while avoiding MNP aggregation. Additionally, our method allows for covalent bonding of the cadherin fragments to the MNP surface while preserving functionality, making it highly versatile. Finally, our strategy not only ensures the correct orientation of the protein fragments on the MNPs but also allows for the precise control of their density. This feature enables the selective targeting of E-cadherin-expressing cells only when MNPs are decorated with a high density of cadherin fragments.

Unveiling the Role of the Properties of Magnetic Nanoparticles for Highly Efficient Low-Frequency Magneto-Mechanical Actuation of Biomolecules

The role of the properties of magnetic nanoparticles in the remote magneto-mechanical actuation of biomolecules under the influence of external magnetic fields is still of particular interest. Here, a specially designed strategy based on the mechanical destruction of short oligonucleotide duplexes is used to demonstrate the effect of magnetic nanoparticles with different sizes (5-99 nm) on the magnitude of the magneto-mechanical actuations in a low-frequency alternating magnetic field. The results show that the mechanical destruction of complementary chains of duplexes, caused by the rotational-vibrational movements of nanoparticles upon exposure to a magnetic field, has a nonmonotonic dependence on the nanoparticle core size. The main hypothesis of this phenomenon is associated with a key role of magneto-dipole interactions between individual nanoparticles, which blocks the movements of nanoparticles in dense clusters. This result will allow fine-tuning of the magnetic nanoparticle properties for addressing specific magneto-mechanical tasks.

Sulfobetaine-Phosphonate Block Copolymer Coated Iron Oxide Nanoparticles for Genomic Locus Targeting and Magnetic Micromanipulation in the Nucleus of Living Cells

Exerting forces on biomolecules inside living cells would allow us to probe their dynamic interactions in their native environment. Magnetic iron oxide nanoparticles represent a unique tool capable of pulling on biomolecules with the application of an external magnetic field gradient; however, their use has been restricted to biomolecules accessible from the extracellular medium. Targeting intracellular biomolecules represents an additional challenge due to potential nonspecific interactions with cytoplasmic or nuclear components. We present the synthesis of sulfobetaine-phosphonate block copolymer ligands, which provide magnetic nanoparticles that are stealthy and targetable in living cells. We demonstrate, for the first time, their efficient targeting in the nucleus and their use for magnetic micromanipulation of a specific genomic locus in living cells. We believe that these stable and sensitive magnetic nanoprobes represent a promising tool to manipulate specific biomolecules in living cells and probe the mechanical properties of living matter at the molecular scale.

Dynamic photoelectrical regulation of ECM protein and cellular behaviors

Dynamic regulation of cell-extracellular matrix (ECM)-material interactions is crucial for various biomedical applications. In this study, a light-activated molecular switch for the modulation of cell attachment/detachment behaviors was established on monolayer graphene (Gr)/n-type Silicon substrates (Gr/Si). Initiated by light illumination at the Gr/Si interface, pre-adsorbed proteins (bovine serum albumin, ECM proteins collagen-1, and fibronectin) underwent protonation to achieve negative charge transfer to Gr films (n-doping) through π-π interactions. This n-doping process stimulated the conformational switches of ECM proteins. The structural alterations in these ECM interactors significantly reduced the specificity of the cell surface receptor-ligand interaction (e.g., integrin recognition), leading to dynamic regulation of cell adhesion and eventual cell detachment. RNA-sequencing results revealed that the detached bone marrow mesenchymal stromal cell sheets from the Gr/Si system manifested regulated immunoregulatory properties and enhanced osteogenic differentiation, implying their potential application in bone tissue regeneration. This work not only provides a fast and feasible method for controllable cells/cell sheets harvesting but also gives new insights into the understanding of cell-ECM-material communications.

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A light-activated molecular switch for regulation of cell attachment/detachment behaviors was established on (Gr/Si) substrates.

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Light-induced charge transfer from ECM protein to Gr/Si through π-π interactions, resulting in the conformational alteration of ECM proteins.

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Structural changes in ECM weakened the binding between RGD and integrin, inducing cell detachment.

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This work provides a feasible method for cell harvesting and improves the understanding of cell-ECM-material communications.

Versatile magnetic configuration for the control and manipulation of superparamagnetic nanoparticles

The control and manipulation of superparamagnetic nanoparticles (SP-MNP) is a significant challenge and has become increasingly important in various fields, especially in biomedical research. Yet, most of applications rely on relatively large nanoparticles, 50 nm or higher, mainly due to the fact that the magnetic control of smaller MNPs is often hampered by the thermally induced Brownian motion. Here we present a magnetic device able to manipulate remotely in microfluidic environment SP-MNPs smaller than 10 nm. The device is based on a specifically tailored configuration of movable permanent magnets. The experiments performed in 500 µm capillary have shown the ability to concentrate the SP-MNPs into regions characterized by different shapes and sizes ranging from 100 to 200 µm. The results are explained by straightforward calculations and comparison between magnetic and thermal energies. We provide then a comprehensive description of the magnetic field intensity and its spatial distribution for the confinement and motion of magnetic nanoparticles for a wide range of sizes. We believe this description could be used to establish accurate and quantitative magnetic protocols not only for biomedical applications, but also for environment, food, security, and other areas.

Untethered: using remote magnetic fields for regenerative medicine

Magnetic fields are increasingly being used for the remote, noncontact manipulation of cells and biomaterials for a wide range of regenerative medical (RM) applications. They have been deployed for their direct effects on biological systems or in conjunction with magnetic materials or magnetically tagged cells for a targeted therapeutic effect. In this work, we highlight the recent trends on the broad use of magnetic fields for the homing of therapeutic cells and particles at targeted tissue sites, biomimetic tissue fabrication, and control of cell fate and proliferation. We also survey the design and control principles of magnetic manipulation systems, including their capabilities and limitations, which can guide future research into developing more effective magnetic field-based regenerative strategies.

Magneto-Mechanical Approach in Biomedicine: Benefits, Challenges, and Future Perspectives

The magneto-mechanical approach is a powerful technique used in many different applications in biomedicine, including remote control enzyme activity, cell receptors, cancer-selective treatments, mechanically-activated drug releases, etc. This approach is based on the use of a combination of magnetic nanoparticles and external magnetic fields that have led to the movement of such nanoparticles with torques and forces (enough to change the conformation of biomolecules or even break weak chemical bonds). However, despite many theoretical and experimental works on this topic, it is difficult to predict the magneto-mechanical effects in each particular case, while the important results are scattered and often cannot be translated to other experiments. The main reason is that the magneto-mechanical effect is extremely sensitive to changes in any parameter of magnetic nanoparticles and the environment and changes in the parameters of the applied magnetic field. Thus, in this review, we (1) summarize and propose a simplified theoretical explanation of the main factors affecting the efficiency of the magneto-mechanical approach; (2) discuss the nature of the MNP-mediated mechanical forces and their order of magnitude; (3) show some of the main applications of the magneto-mechanical approach in the control over the properties of biological systems.

Sonogenetics: Recent advances and future directions

Sonogenetics refers to the use of genetically encoded, ultrasound-responsive mediators for noninvasive and selective control of neural activity. It is a promising tool for studying neural circuits. However, due to its infancy, basic studies and developments are still underway, including gauging key in vivo performance metrics such as spatiotemporal resolution, selectivity, specificity, and safety. In this paper, we summarize recent findings on sonogenetics to highlight technical hurdles that have been cleared, challenges that remain, and future directions for optimization.

Magnetic Control of Cells by Chemical Fabrication of Melanin

Melanin is an organic material biosynthesized from tyrosine in pigment-producing cells. The present study reports a simple method to generate tailored functional materials in mammalian cells by chemically fabricating intracellular melanin. Our approach exploits synthetic tyrosine derivatives to hijack the melanin biosynthesis pathway in pigment-producing cells. Its application was exemplified by synthesizing and using a paramagnetic tyrosine derivative, m-YR, which endowed melanoma cells with responsiveness to external magnetic fields. The mechanical force generated by the magnet-responsive melanin forced the cells to elongate and align parallel to the magnetic power lines. Critically, even non-pigment cells were similarly remote-controlled by external magnetic fields once engineered to express tyrosinase and treated with m-YR, suggesting the versatility of the approach. The present methodology may potentially provide a new avenue for mechanobiology and magnetogenetic studies and a framework for magnetic control of specific cells.

de la Fuente J, Fratila RM, Grazú V, Gutiérrez L. Iron Speciation in Animal Tissues Using AC Magnetic Susceptibility Measurements: Quantification of Magnetic Nanoparticles, Ferritin, and Other Iron-Containing Species

The simultaneous detection and quantification of several iron-containing species in biological matrices is a challenging issue. Especially in the frame of studies using magnetic nanoparticles for biomedical applications, no gold-standard technique has been described yet and combinations of different techniques are generally used. In this work, AC magnetic susceptibility measurements are used to analyze different organs from an animal model that received a single intratumor administration of magnetic nanoparticles. The protocol used for the quantification of iron associated with the magnetic nanoparticles is carefully described, including the description of the preparation of several calibration standard samples of nanoparticle suspensions with different degrees of dipolar interactions. The details for the quantitative analysis of other endogenous iron-containing species such as ferritin or hemoglobin are also described. Among the advantages of this technique are that tissue sample preparation is minimal and that large amounts of tissue can be characterized each time (up to hundreds of milligrams). In addition, the very high specificity of the magnetic measurements allows for tracking of the nanoparticle transformations. Furthermore, the high sensitivity of the instrumentation results in very low limits of detection for some of the iron-containing species. Therefore, the presented technique is an extremely valuable tool to track iron oxide magnetic nanoparticles in samples of biological origin.