Radio-wave heating of iron oxide nanoparticles can regulate plasma glucose in mice

Magnetic Measurement and Stimulation of Cellular and Intracellular Structures

From single-pole magnetic tweezers to robotic magnetic-field generation systems, the development of magnetic micromanipulation systems, using electromagnets or permanent magnets, has enabled a multitude of applications for cellular and intracellular measurement and stimulation. Controlled by different configurations of magnetic-field generation systems, magnetic particles have been actuated by an external magnetic field to exert forces/torques and perform mechanical measurements on the cell membrane, cytoplasm, cytoskeleton, nucleus, intracellular motors, etc. The particles have also been controlled to generate aggregations to trigger cell signaling pathways and produce heat to cause cancer cell apoptosis for hyperthermia treatment. Magnetic micromanipulation has become an important tool in the repertoire of toolsets for cell measurement and stimulation and will continue to be used widely for further explorations of cellular/intracellular structures and their functions. Existing review papers in the literature focus on fabrication and position control of magnetic particles/structures (often termed micronanorobots) and the synthesis and functionalization of magnetic particles. Differently, this paper reviews the principles and systems of magnetic micromanipulation specifically for cellular and intracellular measurement and stimulation. Discoveries enabled by magnetic measurement and stimulation of cellular and intracellular structures are also summarized. This paper ends with discussions on future opportunities and challenges of magnetic micromanipulation in the exploration of cellular biophysics, mechanotransduction, and disease therapeutics.

Emerging Nano- and Micro-Technologies Used in the Treatment of Type-1 Diabetes

Type-1 diabetes is characterized by high blood glucose levels due to a failure of insulin secretion from beta cells within pancreatic islets. Current treatment strategies consist of multiple, daily injections of insulin or transplantation of either the whole pancreas or isolated pancreatic islets. While there are different forms of insulin with tunable pharmacokinetics (fast, intermediate, and long-acting), improper dosing continues to be a major limitation often leading to complications resulting from hyper- or hypo-glycemia. Glucose-responsive insulin delivery systems, consisting of a glucose sensor connected to an insulin infusion pump, have improved dosing but they still suffer from inaccurate feedback, biofouling and poor patient compliance. Islet transplantation is a promising strategy but requires multiple donors per patient and post-transplantation islet survival is impaired by inflammation and suboptimal revascularization. This review discusses how nano- and micro-technologies, as well as tissue engineering approaches, can overcome many of these challenges and help contribute to an artificial pancreas-like system.

Bio-Fabrication: Convergence of 3D Bioprinting and Nano-Biomaterials in Tissue Engineering and Regenerative Medicine

3D Bioprinting (3DBP) technologies open many possibilities for the generation of highly complex cellularized constructs. Nano-biomaterials have been largely used in tissue engineering and regenerative medicine (TERM) for different purposes and functions depending on their intrinsic properties and how they have been presented in the biologic environment. Combination of bioprinting and nano-biomaterials paves the way for unexpected opportunities in the biofabrication scenario, by improving critical weakness of these manufacturing processes while enhancing their efficiency by spatially arranging nano-features. 3D organization of cells is fundamental for a successful design and maturation of native tissues. A critical challenge for the production of biological constructs is to support and guide cell growth toward their natural microenvironment, ensuring a harmonious presence of specific biochemical and biophysical cues to direct cell behavior. Also, precise arrays of stimuli need to be designed to induce stem cell differentiation toward specific tissues. Introducing nano-sized bioactive material can direct cell fate, playing a role in the differentiation process and leading to the biofabrication of functional structures. Nano-composite bio-ink can be used to generate cell instructive scaffolds or either directly printed with cells. In addition, the presence of nano-particles within 3D printed constructs can lead to control them through multiple external physical stimuli, representing an additional tool for healthcare applications. Finally, there is an emerging interest to create biological constructs having active properties, such as sensing, motion or shape modification. In this review, we highlight how introducing nano-biomaterials in bioprinting approaches leads to promising strategies for tissue regeneration.

Transgene-free remote magnetothermal regulation of adrenal hormones

The field of bioelectronic medicines seeks to modulate electrical signaling within peripheral organs, providing temporally precise control of physiological functions. This is usually accomplished with implantable devices, which are often unsuitable for interfacing with soft and highly vascularized organs. Here, we demonstrate an alternative strategy for modulating peripheral organ function, which relies on the endogenous expression of a heat-sensitive cation channel, transient receptor potential vanilloid family member 1 (TRPV1), and heat dissipation by magnetic nanoparticles (MNPs) in remotely applied alternating magnetic fields. We use this approach to wirelessly control adrenal hormone secretion in genetically intact rats. TRPV1-dependent calcium influx into the cells of adrenal cortex and medulla is sufficient to drive rapid release of corticosterone and (nor)epinephrine. As altered levels of these hormones have been correlated with mental conditions such as posttraumatic stress disorder and major depression, our approach may facilitate the investigation of physiological and psychological impacts of stress.

Nanoscale Heat Transfer from Magnetic Nanoparticles and Ferritin in an Alternating Magnetic Field

Recent suggestions of nanoscale heat confinement on the surface of synthetic and biogenic magnetic nanoparticles during heating by radio frequency-alternating magnetic fields have generated intense interest because of the potential utility of this phenomenon for noninvasive control of biomolecular and cellular function. However, such confinement would represent a significant departure from the classical heat transfer theory. Here, we report an experimental investigation of nanoscale heat confinement on the surface of several types of iron oxide nanoparticles commonly used in biological research, using an all-optical method devoid of the potential artifacts present in previous studies. By simultaneously measuring the fluorescence of distinct thermochromic dyes attached to the particle surface or dissolved in the surrounding fluid during radio frequency magnetic stimulation, we found no measurable difference between the nanoparticle surface temperature and that of the surrounding fluid for three distinct nanoparticle types. Furthermore, the metalloprotein ferritin produced no temperature increase on the protein surface nor in the surrounding fluid. Experiments mimicking the designs of previous studies revealed potential sources of the artifacts. These findings inform the use of magnetic nanoparticle hyperthermia in engineered cellular and molecular systems.

Probing the Local Nanoscale Heating Mechanism of a Magnetic Core in Mesoporous Silica Drug-Delivery Nanoparticles Using Fluorescence Depolarization

In the presence of an alternating magnetic field (AMF), a superparamagnetic iron oxide nanoparticle (SPION) generates heat. Understanding the local heating mechanism of a SPION in suspension and in a mesoporous silica nanoparticle (MSN) will advance the design of hyperthermia-based nanotheranostics and AMF-stimulated drug delivery in biomedical applications. The AMF-induced heating of single-domain SPION can be explained by the Néel relaxation (reorientation of the magnetization) or the Brownian relaxation (motion of the particle). The latter is investigated using fluorescence depolarization based on detecting the mobility-dependent polarization anisotropy (r) of two luminescence emission bands at different wavelengths corresponded to the europium-doped luminescent SPION (EuSPION) core and the silica-based intrinsically emitting shell of the core-shell MSN. The fluorescence depolarization experiments are carried out with both the free and the silica-encapsulated SPION nanoparticles with and without application of the AMF. The r value of a EuSPION core-mesoporous silica shell in the presence of the AMF does not change, indicating that no additional rotational motion of the core-shell nanoparticles is induced by the AMF, disproving the contribution of Brownian heating and thus supporting Néel relaxation as the dominant heating mechanism.

Synthetic immunity by remote control

Cell-based immunotherapies, such as T cells engineered with chimeric antigen receptors (CARs), have the potential to cure patients of disease otherwise refractory to conventional treatments. Early-on-treatment and long-term durability of patient responses depend critically on the ability to control the potency of adoptively transferred T cells, as overactivation can lead to complications like cytokine release syndrome, and immunosuppression can result in ineffective responses to therapy. Drugs or biologics (e.g., cytokines) that modulate immune activity are limited by mass transport barriers that reduce the local effective drug concentration, and lack site or target cell specificity that results in toxicity. Emerging technologies that enable site-targeted, remote control of key T cell functions - including proliferation, antigen-sensing, and target-cell killing - have the potential to increase treatment precision and safety profile. These technologies are broadly applicable to other immune cells to expand immune cell therapies across many cancers and diseases. In this review, we highlight the opportunities, challenges and the current state-of-the-art for remote control of synthetic immunity.

Comprehensive understanding of magnetic hyperthermia for improving antitumor therapeutic efficacy

Magnetic hyperthermia (MH) has been introduced clinically as an alternative approach for the focal treatment of tumors. MH utilizes the heat generated by the magnetic nanoparticles (MNPs) when subjected to an alternating magnetic field (AMF). It has become an important topic in the nanomedical field due to their multitudes of advantages towards effective antitumor therapy such as high biosafety, deep tissue penetration, and targeted selective tumor killing. However, in order for MH to progress and to realize its paramount potential as an alternative choice for cancer treatment, tremendous challenges have to be overcome. Thus, the efficiency of MH therapy needs enhancement. In its recent 60-year of history, the field of MH has focused primarily on heating using MNPs for therapeutic applications. Increasing the thermal conversion efficiency of MNPs is the fundamental strategy for improving therapeutic efficacy. Recently, emerging experimental evidence indicates that MNPs-MH produces nano-scale heat effects without macroscopic temperature rise. A deep understanding of the effect of this localized induction heat for the destruction of subcellular/cellular structures further supports the efficacy of MH in improving therapeutic therapy. In this review, the currently available strategies for improving the antitumor therapeutic efficacy of MNPs-MH will be discussed. Firstly, the recent advancements in engineering MNP size, composition, shape, and surface to significantly improve their energy dissipation rates will be explored. Secondly, the latest studies depicting the effect of local induction heat for selectively disrupting cells/intracellular structures will be examined. Thirdly, strategies to enhance the therapeutics by combining MH therapy with chemotherapy, radiotherapy, immunotherapy, photothermal/photodynamic therapy (PDT), and gene therapy will be reviewed. Lastly, the prospect and significant challenges in MH-based antitumor therapy will be discussed. This review is to provide a comprehensive understanding of MH for improving antitumor therapeutic efficacy, which would be of utmost benefit towards guiding the users and for the future development of MNPs-MH towards successful application in medicine.

New Vision for Visual Prostheses

Developments of new strategies to restore vision and improving on current strategies by harnessing new advancements in material and electrical sciences, and biological and genetic-based technologies are of upmost health priorities around the world. Federal and private entities are spending billions of dollars on visual prosthetics technologies. This review describes the most current and state-of-the-art bioengineering technologies to restore vision. This includes a thorough description of traditional electrode-based visual prosthetics that have improved substantially since early prototypes. Recent advances in molecular and synthetic biology have transformed vision-assisted technologies; For example, optogenetic technologies that introduce light-responsive proteins offer excellent resolution but cortical applications are restricted by fiber implantation and tissue damage. Other stimulation modalities, such as magnetic fields, have been explored to achieve non-invasive neuromodulation. Miniature magnetic coils are currently being developed to activate select groups of neurons. Magnetically-responsive nanoparticles or exogenous proteins can significantly enhance the coupling between external electromagnetic devices and any neurons affiliated with these modifications. The need to minimize cytotoxic effects for nanoparticle-based therapies will likely restrict the number of usable materials. Nevertheless, advances in identifying and utilizing proteins that respond to magnetic fields may lead to non-invasive, cell-specific stimulation and may overcome many of the limitations that currently exist with other methods. Finally, sensory substitution systems also serve as viable visual prostheses by converting visual input to auditory and somatosensory stimuli. This review also discusses major challenges in the field and offers bioengineering strategies to overcome those.

Using magnetic particle imaging systems to localize and guide magnetic hyperthermia treatment: tracers, hardware, and future medical applications

Magnetic fluid hyperthermia (MFH) treatment makes use of a suspension of superparamagnetic iron oxide nanoparticles, administered systemically or locally, in combination with an externally applied alternating magnetic field, to ablate target tissue by generating heat through a process called induction. The heat generated above the mammalian euthermic temperature of 37°C induces apoptotic cell death and/or enhances the susceptibility of the target tissue to other therapies such as radiation and chemotherapy. While most hyperthermia techniques currently in development are targeted towards cancer treatment, hyperthermia is also used to treat restenosis, to remove plaques, to ablate nerves and to alleviate pain by increasing regional blood flow. While RF hyperthermia can be directed invasively towards the site of treatment, non-invasive localization of heat through induction is challenging. In this review, we discuss recent progress in the field of RF magnetic fluid hyperthermia and introduce a new diagnostic imaging modality called magnetic particle imaging that allows for a focused theranostic approach encompassing treatment planning, treatment monitoring and spatially localized inductive heating.

Ferrimagnetic mPEG-b-PHEP copolymer micelles loaded with iron oxide nanocubes and emodin for enhanced magnetic hyperthermia–chemotherapy

As a non-invasive therapeutic method without penetration-depth limitation, magnetic hyperthermia therapy (MHT) under alternating magnetic field (AMF) is a clinically promising thermal therapy. However, the poor heating conversion efficiency and lack of stimulus–response obstruct the clinical application of magnetofluid-mediated MHT. Here, we develop a ferrimagnetic polyethylene glycol-poly(2-hexoxy-2-oxo-1,3,2-dioxaphospholane) (mPEG-b-PHEP) copolymer micelle loaded with hydrophobic iron oxide nanocubes and emodin (denoted as EMM). Besides an enhanced magnetic resonance (MR) contrast ability (r₂ = 271 mM⁻¹ s⁻¹) due to the high magnetization, the specific absorption rate (2518 W/g at 35 kA/m) and intrinsic loss power (6.5 nHm²/kg) of EMM are dozens of times higher than the clinically available iron oxide nanoagents (Feridex and Resovist), indicating the high heating conversion efficiency. Furthermore, this composite micelle with a flowable core exhibits a rapid response to magnetic hyperthermia, leading to an AMF-activated supersensitive drug release. With the high magnetic response, thermal sensitivity and magnetic targeting, this supersensitive ferrimagnetic nanocomposite realizes an above 70% tumor cell killing effect at an extremely low dosage (10 μg Fe/mL), and the tumors on mice are completely eliminated after the combined MHT–chemotherapy.

Acoustically responsive polydopamine nanodroplets: A novel theranostic agent

Ultrasound-induced cavitation has been used as a tool of enhancing extravasation and tissue penetration of anticancer agents in tumours. Initiating cavitation in tissue however, requires high acoustic intensities that are neither safe nor easy to achieve with current clinical systems. The use of cavitation nuclei can however lower the acoustic intensities required to initiate cavitation and the resulting bio-effects in situ. Microbubbles, solid gas-trapping nanoparticles, and phase shift nanodroplets are some examples in a growing list of proposed cavitation nuclei. Besides the ability to lower the cavitation threshold, stability, long circulation times, biocompatibility and biodegradability, are some of the desirable characteristics that a clinically applicable cavitation agent should possess. In this study, we present a novel formulation of ultrasound-triggered phase transition sub-micrometer sized nanodroplets (~400 nm) stabilised with a biocompatible polymer, polydopamine (PDA). PDA offers some important benefits: (1) facile fabrication, as dopamine monomers are directly polymerised on the nanodroplets, (2) high polymer biocompatibility, and (3) ease of functionalisation with other molecules such as drugs or targeting species. We demonstrate that the acoustic intensities required to initiate inertial cavitation can all be achieved with existing clinical ultrasound systems. Cell viability and haemolysis studies show that nanodroplets are biocompatible. Our results demonstrate the great potential of PDA nanodroplets as an acoustically active nanodevice, which is highly valuable for biomedical applications including drug delivery and treatment monitoring.

Magnetic Iron Oxide Nanoparticles for Disease Detection and Therapy

Magnetic iron oxide nanoparticles (MIONs) are among the first generation of nanomaterials that have advanced to clinic use. A broad range of biomedical techniques has been developed by combining the versatile nanomagnetism of MIONs with various forms of applied magnetic fields. MIONs can generate imaging contrast and provide mechanical/thermal energy in vivo in response to an external magnetic field, a special feature that distinguishes MIONs from other nanomaterials. These properties offer unique opportunities for nanomaterials engineering in biomedical research and clinical interventions. The past few decades have witnessed the evolution of the applications of MIONs from conventional drug delivery and hyperthermia to the regulation of molecular and cellular processes in the body. Here we review the most recent development in this field, including clinical studies of MIONs and the emerging techniques that may contribute to future innovation in medicine.

Lipid/PLGA Hybrid Microbubbles as a Versatile Platform for Noninvasive Image-Guided Targeted Drug Delivery

Microbubbles (MBs) have recently emerged as promising theranostic carriers for ultrasound contrast imaging and drug delivery. However, conventional lipid-based MBs have a poor drug encapsulation efficiency, and polymer-based MBs show a weak capability in contrast imaging and ultrasound-triggered drug release. Here, we developed a novel type of multiporous lipid/PLGA hybrid MBs (lipid/PLGA MBs) that solved the dilemma of MBs as imaging agents and drug carriers. The lipid/PLGA MBs were designed through regulating the elasticity of the bubble shells using lipids to incorporate into the PLGA shells and ammonium bicarbonate as a gas-generating agent. The softened shells and the porous bubble structure make them be able to generate stronger harmonic signals and be more vulnerable to ultrasound irradiation, leading to their excellent performance in ultrasound contrast imaging and ultrasound-triggered MB destruction in vitro and in vivo. By using doxorubicin (Dox) as a model drug, the Dox-loaded lipid/PLGA MBs (Dox-lipid/PLGA MBs) were prepared and achieved a high drug encapsulation efficiency. The real-time tracking of drug delivery and on-command controlled drug release by ultrasound were successfully realized in the tumor-bearing mice. A significantly enhanced tumor growth inhibition effect could be observed when using Dox-lipid/PLGA MBs combined with ultrasound irradiation, compared with free Dox and Dox-lipid/PLGA MBs without ultrasound. Our study provides an innovative multifunctional platform of MBs for ultrasound contrast imaging and drug delivery applications.

Remote and real time control of an FVIO-enzyme hybrid nanocatalyst using magnetic stimulation

Remote modulation of nanoscale biochemical processes in a living system using magnetic stimulation is appealing but is restricted by the lack of a highly efficient nanomediator which can deliver timely and effective response to biological molecules under an external magnetic field. Herein, we report the development of a novel nanocatalyst based on a ferrimagnetic vortex-domain nanoring (FVIO)-enzyme hybrid that enables real-time modulation of enzymatic catalysis under an alternating magnetic field (AMF). The role of the FVIO is to provide localized heating immediately upon exposure to an AMF, which efficiently and selectively promotes the activity of conjugated enzymes on the surface. The reaction rate of the as-fabricated FVIO-β-Gal hybrid was shown to be boosted up to 180% of its initial value by localized heat generated under an AMF of 550 Oe in less than 2 s and without heating up the bulk solution. Moreover, the degree of activity acceleration was shown to be tunable by increasing the strength of the AMF. The concept of remote magnetic stimulation of enzymatic reactions has been further applied to other enzymes (e.g. FVIO-KPC and FVIO-GOx), demonstrating the general applicability of this strategy. Since almost all metabolic processes in cells rely on enzymatic catalysis to sustain life, the FVIO-enzyme system developed in this work provides a valuable nanoplatform for spatiotemporally manipulating biochemical reactions, which might pave the way for future remote manipulation of living organisms.

Remotely controlled chemomagnetic modulation of targeted neural circuits

Connecting neural circuit output to behaviour can be facilitated by the precise chemical manipulation of specific cell populations^1,2. Engineered receptors exclusively activated by designer small molecules enable manipulation of specific neural pathways^3,4. However, their application to studies of behaviour has thus far been hampered by a trade-off between the low temporal resolution of systemic injection versus the invasiveness of implanted cannulae or infusion pumps². Here, we developed a remotely controlled chemomagnetic modulation-a nanomaterials-based technique that permits the pharmacological interrogation of targeted neural populations in freely moving subjects. The heat dissipated by magnetic nanoparticles (MNPs) in the presence of alternating magnetic fields (AMFs) triggers small-molecule release from thermally sensitive lipid vesicles with a 20 s latency. Coupled with the chemogenetic activation of engineered receptors, this technique permits the control of specific neurons with temporal and spatial precision. The delivery of chemomagnetic particles to the ventral tegmental area (VTA) allows the remote modulation of motivated behaviour in mice. Furthermore, this chemomagnetic approach activates endogenous circuits by enabling the regulated release of receptor ligands. Applied to an endogenous dopamine receptor D1 (DRD1) agonist in the nucleus accumbens (NAc), a brain area involved in mediating social interactions, chemomagnetic modulation increases sociability in mice. By offering a temporally precise control of specified ligand-receptor interactions in neurons, this approach may facilitate molecular neuroscience studies in behaving organisms.

Synthetic biology-based cellular biomedical tattoo for detection of hypercalcemia associated with cancer

Diagnosis marks the beginning of any successful therapy. Because many medical conditions progress asymptomatically over extended periods of time, their timely diagnosis remains difficult, and this adversely affects patient prognosis. Focusing on hypercalcemia associated with cancer, we aimed to develop a synthetic biology-inspired biomedical tattoo using engineered cells that would (i) monitor long-term blood calcium concentration, (ii) detect onset of mild hypercalcemia, and (iii) respond via subcutaneous accumulation of the black pigment melanin to form a visible tattoo. For this purpose, we designed cells containing an ectopically expressed calcium-sensing receptor rewired to a synthetic signaling cascade that activates expression of transgenic tyrosinase, which produces melanin in response to persistently increased blood Ca²⁺ We confirmed that the melanin-generated color change produced by this biomedical tattoo could be detected with the naked eye and optically quantified. The system was validated in wild-type mice bearing subcutaneously implanted encapsulated engineered cells. All animals inoculated with hypercalcemic breast and colon adenocarcinoma cells developed tattoos, whereas no tattoos were seen in animals inoculated with normocalcemic tumor cells. All tumor-bearing animals remained asymptomatic throughout the 38-day experimental period. Although hypercalcemia is also associated with other pathologies, our findings demonstrate that it is possible to detect hypercalcemia associated with cancer in murine models using this cell-based diagnostic strategy.

Nanostructure Endows Neurotherapeutic Potential in Optogenetics: Current Development and Future Prospects

Optogenetics have evolved as a promising tool to control the processes at a cellular level via photons. Specially, it confers a specific control over cellular function through real-time cytomodulation even in freely moving animals. Neuronal stimulation is prerequisite for deep tissue light penetration or insertion of optrode for light illumination to the neurons that have been proven to be compromised due to poor light penetration and invasiveness of the procedure, respectively. In this review, the application of nanotechnology is being elaborated by the use of metal nanoparticles (AuNPs), upconversion nanocrystals (UCNPs), and quantum dots (CdSe) for targeting particular organs or tissues, and their potential to emit a specific light on excitation to overcome the limitations associated with earlier methods has been elucidated. The optothermal and magnetothermal properties, photoluminescence, and higher photostability of nanomaterials are explored in context of therapeutic applicability of optogenetics. The nanostructure characteristics and specific ion channel targeting have shown promising therapeutic potential against neurodegenerative disorders (Alzheimer's, Parkinson's, Huntington's), epilepsy, and blindness. This review compiles mechanical and optical characteristics of nanomaterials that endow superior optogenetic therapeutic potentials to cure immedicable infirmities.

Possible magneto-mechanical and magneto-thermal mechanisms of ion channel activation in magnetogenetics

The palette of tools for perturbation of neural activity is continually expanding. On the forefront of this expansion is magnetogenetics, where ion channels are genetically engineered to be closely coupled to the iron-storage protein ferritin. Initial reports on magnetogenetics have sparked a vigorous debate on the plausibility of physical mechanisms of ion channel activation by means of external magnetic fields. The criticism leveled against magnetogenetics as being physically implausible is based on the specific assumptions about the magnetic spin configurations of iron in ferritin. I consider here a wider range of possible spin configurations of iron in ferritin and the consequences these might have in magnetogenetics. I propose several new magneto-mechanical and magneto-thermal mechanisms of ion channel activation that may clarify some of the mysteries that presently challenge our understanding of the reported biological experiments. Finally, I present some additional puzzles that will require further theoretical and experimental investigation.

Nanotransducers for Near-Infrared Photoregulation in Biomedicine

Photoregulation, which utilizes light to remotely control biological events, provides a precise way to decipher biology and innovate in medicine; however, its potential is limited by the shallow tissue penetration and/or phototoxicity of ultraviolet (UV)/visible light that are required to match the optical responses of endogenous photosensitive substances. Thereby, biologically friendly near-infrared (NIR) light with improved tissue penetration is desired for photoregulation. Since there are a few endogenous biomolecules absorbing or emitting light in the NIR region, the development of molecular transducers is essential to convert NIR light into the cues for regulation of biological events. In this regard, optical nanomaterials able to convert NIR light into UV/visible light, heat, or free radicals are suitable for this task. Here, the recent developments of optical nanotransducers for NIR-light-mediated photoregulation in medicine are summarized. The emerging applications, including photoregulation of neural activity, gene expression, and visual systems, as well as photochemical tissue bonding, are highlighted, along with the design principles of nanotransducers. Moreover, the current challenges and perspectives in this field are discussed.

A synthetic free fatty acid-regulated transgene switch in mammalian cells and mice

Trigger-inducible transgene expression systems are utilized in biopharmaceutical manufacturing and also to enable controlled release of therapeutic agents in vivo. We considered that free fatty acids (FFAs), which are dietary components, signaling molecules and important biomarkers, would be attractive candidates as triggers for novel transgene switches with many potential applications, e.g. in future gene- and cell-based therapies. To develop such a switch, we rewired the signal pathway of human G-protein coupled receptor 40 to a chimeric promoter triggering gene expression through an increase of intracellular calcium concentration. This synthetic gene switch is responsive to physiologically relevant FFA concentrations in different mammalian cell types grown in culture or in a bioreactor, or implanted into mice. Animal recipients of microencapsulated sensor cells containing this switch exhibited significant transgene induction following consumption of dietary fat (such as Swiss cheese) or under hyperlipidaemic conditions, including obesity, diabetes and lipodystrophy.

Vagal mechanisms as neuromodulatory targets for the treatment of metabolic disease

With few effective treatments available, the global rise of metabolic diseases, including obesity, type 2 diabetes mellitus, and cardiovascular disease, seems unstoppable. Likely caused by an obesogenic environment interacting with genetic susceptibility, the pathophysiology of obesity and metabolic diseases is highly complex and involves crosstalk between many organs and systems, including the brain. The vagus nerve is in a key position to bidirectionally link several peripheral metabolic organs with the brain and is increasingly targeted for neuromodulation therapy to treat metabolic disease. Here, we review the basics of vagal functional anatomy and its implications for vagal neuromodulation therapies. We find that most existing vagal neuromodulation techniques either ignore or misinterpret the rich functional specificity of both vagal efferents and afferents as demonstrated by a large body of literature. This lack of specificity of manipulating vagal fibers is likely the reason for the relatively poor beneficial long‐term effects of such therapies. For these therapies to become more effective, rigorous validation of all physiological endpoints and optimization of stimulation parameters as well as electrode placements will be necessary. However, given the large number of function‐specific fibers in any vagal branch, genetically guided neuromodulation techniques are more likely to succeed.

Nanoparticle-based local translation reveals mRNA as a translation-coupled scaffold with anchoring function

The spatial regulation of messenger RNA (mRNA) translation is central to cellular functions and relies on numerous complex processes. Biomimetic approaches could bypass these endogenous complex processes, improve our comprehension of the regulation, and allow for controlling local translation regulations and functions. However, the causality between local translation and nascent protein function remains elusive. Here, we developed a nanoparticle (NP)-based strategy to magnetically control mRNA spatial patterns in mammalian cell extracts and investigate how local translation impacts nascent protein localization and function. By monitoring the translation of the magnetically localized mRNAs, we show that mRNA-NP complexes operate as a source for the continuous production of proteins from defined positions. By applying this approach to actin-binding proteins, we triggered the local formation of actin cytoskeletons and identified the minimal requirements for spatial control of the actin filament network. In addition, our bottom-up approach identified a role for mRNA as a translation-coupled scaffold for the function of nascent N-terminal protein domains. Our approach will serve as a platform for regulating mRNA localization and investigating the function of nascent protein domains during translation.

Near-Infrared Light Activated Thermosensitive Ion Channel to Remotely Control Transgene System for Thrombolysis Therapy

Current antithrombotic therapeutic strategies often suffer from severe post-thrombotic syndromes (PTS), inconvenient daily subcutaneous injections for a long time and short circulation times accompanied by a dose-dependent risk of intracranial hemorrhage. Aiming at noninvasive, on-demand, and sustained antithrombotic therapy, a new thrombolysis approach based on the transgene system has been developed to remotely and precisely control the expression of urokinase plasminogen activator (uPA) by bioengineered cells for antithrombotic therapy both in vitro and in vivo. In this design, the near-infrared (NIR) light could activate the expression of the thermosensitive TRPV1 channel in response to photothermal responsive nanotransducers to trigger the synthetic signaling pathway to secret uPA. By encapsulating bioengineered cells in injectable hydrogel to ensure long-term survival and convenience for injection, the engineered cells could noninvasively and precisely control the production of uPA protein in situ via an NIR laser to significantly enhance the thrombolysis therapeutic effects by spatiotemporally controlling the local temperature, in both the microfluidic blood circulation mimic and the murine tail thrombus model. This novel thrombolysis approach could overcome some key limitations that are associated with conventional antithrombotic therapy, thus opening a new direction for developing remotely and precisely controllable continuous thrombolysis through artificially designed signaling.

Theoretical Analysis for Wireless Magnetothermal Deep Brain Stimulation Using Commercial Nanoparticles

A wireless magnetothermal stimulation (WMS) is suggested as a fast, tetherless, and implanted device-free stimulation method using low-radio frequency (100 kHz to 1 MHz) alternating magnetic fields (AMF). As magnetic nanoparticles (MNPs) can transduce alternating magnetic fields into heat, they are targeted to a region of the brain expressing the temperature-sensitive ion channel (TRPV1). The local temperature of the targeted area is increased up to 44 °C to open the TRPV1 channels and cause an influx of Ca²⁺ sensitive promoter, which can activate individual neurons inside the brain. The WMS has initially succeeded in showing the potential of thermomagnetics for the remote control of neural cell activity with MNPs that are internally targeted to the brain. In this paper, by using the steady-state temperature rise defined by Fourier’s law, the bio-heat equation, and COMSOL Multiphysics software, we investigate most of the basic parameters such as the specific loss power (SLP) of MNPs, the injection volume of magnetic fluid, stimulation and cooling times, and cytotoxic effects at high temperatures (43–44 °C) to provide a realizable design guideline for WMS.

Nanoparticle Activation Methods in Cancer Treatment

In this review, we intend to highlight the progress which has been made in recent years around different types of smart activation nanosystems for cancer treatment. Conventional treatment methods, such as chemotherapy or radiotherapy, suffer from a lack of specific targeting and consequent off-target effects. This has led to the development of smart nanosystems which can effect specific regional and temporal activation. In this review, we will discuss the different methodologies which have been designed to permit activation at the tumour site. These can be divided into mechanisms which take advantage of the differences between healthy cells and cancer cells to trigger activation, and those which activate by a mechanism extrinsic to the cell or tumour environment.

Subcellular distributions of iron oxide nanoparticles in rat brains affected by different surface modifications

The impact of the surface modification on the subcellular distribution of nanoparticles in the brain remains elusive. The nanoparticles prepared by conjugating polyethylene glycol and maleic anhydride-coated superparamagnetic iron oxide nanoparticles (Mal-SPIONs) with bovine serum albumin (BSA/Mal-SPIONs) and with Arg-Gly-Asp peptide (RGD/Mal-SPIONs) were injected into the rat substantia nigra. Observation of transmission electron microscopy (TEM) samples obtained 24 h after perfusion showed that abundant RGD/Mal-SPIONs accumulated in the myelin sheath, dendrites, axon terminals and mitochondria, and on cell membranes in the brain tissue near the injection site. For rats injected with BSA/Mal-SPIONs, a few nanoparticles accumulated in the myelin sheath, axon terminals, endoplasmic reticulum, mitochondria, Golgi, and lysosomes of neurons and glial cells while least SPIONs in rats injected with Mal-SPIONs were found. TEM pictures showed some Mal-SPIONs were expelled out of the brain. RGD/Mal-SPIONs diffused extensively to the thalamus, frontal cortex, temporal lobe, olfactory bulb, and brain stem after injection. Only a few BSA/Mal-SPIONs diffused to the afore-mentioned brain areas. This work reveals different surface modifications on the iron oxide nanoparticles play crucial roles in their distribution and diffusion in the rat brains.

Precise cell behaviors manipulation through light-responsive nano-regulators: recent advance and perspective

Nanotechnology-assisted spatiotemporal manipulation of biological events holds great promise in advancing the practice of precision medicine in healthcare systems. The progress in internal and/or external stimuli-responsive nanoplatforms for highly specific cellular regulations and theranostic controls offer potential clinical translations of the revolutionized nanomedicine. To successfully implement this new paradigm, the emerging light-responsive nanoregulators with unparalleled precise cell functions manipulation have gained intensive attention, providing UV-Vis light-triggered photocleavage or photoisomerization studies, as well as near-infrared (NIR) light-mediated deep-tissue applications for stimulating cellular signal cascades and treatment of mortal diseases. This review discusses current developments of light-activatable nanoplatforms for modulations of various cellular events including neuromodulations, stem cell monitoring, immunomanipulation, cancer therapy, and other biological target intervention. In summary, the propagation of light-controlled nanomedicine would place a bright prospect for future medicine.

Electromagnetic Regulation of Cell Activity

The ability to observe the effects of rapidly and reversibly regulating cell activity in targeted cell populations has provided numerous physiologic insights. Over the last decade, a wide range of technologies have emerged for regulating cellular activity using optical, chemical, and, more recently, electromagnetic modalities. Electromagnetic fields can freely penetrate cells and tissue and their energy can be absorbed by metal particles. When released, the absorbed energy can in turn gate endogenous or engineered receptors and ion channels to regulate cell activity. In this manner, electromagnetic fields acting on external nanoparticles have been used to exert mechanical forces on cell membranes and organelles to generate heat and interact with thermally activated proteins or to induce receptor aggregation and intracellular signaling. More recently, technologies using genetically encoded nanoparticles composed of the iron storage protein, ferritin, have been used for targeted, temporal control of cell activity in vitro and in vivo. These tools provide a means for noninvasively modulating gene expression, intracellular organelles, such as endosomes, and whole-cell activity both in vitro and in freely moving animals. The use of magnetic fields interacting with external or genetically encoded nanoparticles thus provides a rapid noninvasive means for regulating cell activity.

Magnetically triggered transgene expression in mammalian cells by localized cellular heating of magnetic nanoparticles

To develop a remote control system of transgene expression through localized cellular heating of magnetic nanoparticles, a heat-inducible transgene expression system was introduced into mammalian cells. Cells were labeled with magnetic nanoparticles and exposed to an alternating magnetic field. The magnetically labeled cells expressed the transgene in a monolayer and multilayered cell sheets in which cells were heated around the magnetic nanoparticles without an apparent temperature increase in the culture medium. Magnetic cells were also generated by genetically engineering with a ferritin gene, and transgene expression could be induced by exposure to an alternating magnetic field. This approach may be applicable to the development of novel gene therapies in cell-based medicine.

Magnetic Strategies for Nervous System Control

Magnetic fields pass through tissue undiminished and without producing harmful effects, motivating their use as a wireless, minimally invasive means to control neural activity. Here, we review mechanisms and techniques coupling magnetic fields to changes in electrochemical potentials across neuronal membranes. Biological magnetoreception, although incompletely understood, is discussed as a potential source of inspiration. The emergence of magnetic properties in materials is reviewed to clarify the distinction between biomolecules containing transition metals and ferrite nanoparticles that exhibit significant net moments. We describe recent developments in the use of magnetic nanomaterials as transducers converting magnetic stimuli to forms readily perceived by neurons and discuss opportunities for multiplexed and bidirectional control as well as the challenges posed by delivery to the brain. The variety of magnetic field conditions and mechanisms by which they can be coupled to neuronal signaling cascades highlights the desirability of continued interchange between magnetism physics and neurobiology.

Progress in neuromodulation of the brain: A role for magnetic nanoparticles?

The field of neuromodulation is developing rapidly. Current techniques, however, are still limited as they i) either depend on permanent implants, ii) require invasive procedures, iii) are not cell-type specific, iv) involve slow pharmacokinetics or v) have a restricted penetration depth making it difficult to stimulate regions deep within the brain. Refinements into the different fields of neuromodulation are thus needed. In this review, we will provide background information on the different techniques of neuromodulation discussing their latest refinements and future potentials including the implementation of nanoparticles (NPs). In particular we will highlight the usage of magnetic nanoparticles (MNPs) as transducers in advanced neuromodulation. When exposed to an alternating magnetic field (AMF), certain MNPs can generate heat through hysteresis. This MNP heating has been promising in the field of cancer therapy and has recently been introduced as a method for remote and wireless neuromodulation. This indicates that MNPs may aid in the exploration of brain functions via neuromodulation and may eventually be applied for treatment of neuropsychiatric disorders. We will address the materials chemistry of MNPs, their biomedical applications, their delivery into the brain, their mechanisms of stimulation with emphasis on MNP heating and their remote control in living tissue. The final section compares and discusses the parameters used for MNP heating in brain cancer treatment and neuromodulation. Concluding, using MNPs for nanomaterial-mediated neuromodulation seem promising in a variety of techniques and could be applied for different neuropsychiatric disorders when more extensively investigated.

Synthetic Switches and Regulatory Circuits in Plants

Synthetic biology is an established but ever-growing interdisciplinary field of research currently revolutionizing biomedicine studies and the biotech industry. The engineering of synthetic circuitry in bacterial, yeast, and animal systems prompted considerable advances for the understanding and manipulation of genetic and metabolic networks; however, their implementation in the plant field lags behind. Here, we review theoretical-experimental approaches to the engineering of synthetic chemical- and light-regulated (optogenetic) switches for the targeted interrogation and control of cellular processes, including existing applications in the plant field. We highlight the strategies for the modular assembly of genetic parts into synthetic circuits of different complexity, ranging from Boolean logic gates and oscillatory devices up to semi- and fully synthetic open- and closed-loop molecular and cellular circuits. Finally, we explore potential applications of these approaches for the engineering of novel functionalities in plants, including understanding complex signaling networks, improving crop productivity, and the production of biopharmaceuticals.

Chemiluminometric fingerprints for identification of plasmonic nanoparticles

Development of a convenient and inexpensive method for identification and detection of nanoparticles (NPs) is of great interest. In this work, we have developed a novel and simple chemiluminescence based sensor array, with its sensing mechanism mimicking that of olfactory and gustatory systems for discriminating a set of NPs. The proposed method is based on the enhancement effect of NPs on luminol-oxidant CL intensity by their catalytic effect. Three kinds of oxidant including H₂O₂, AgNO₃, and K₃Fe(CN)₆ were used as sensor elements and NPs exhibited diverse enhancing responses to different oxidant-luminol CL systems producing unique response patterns that were identified through heat map and chemometric methods, including linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA). Five NPs have been well distinguished at various concentrations. In addition, this method clearly revealed a linear relationship between CL signal values and the concentrations of NPs for the quantitative detection of NPs. We believe that this type of CL sensor array can open a new way for facile discrimination and detection of different kinds of NPs.

The ABC Guide to Fluorescent Toolsets for the Development of Future Biomaterials

In recent decades, diversified approaches using nanoparticles or nano-structured scaffolds have been applied to drug delivery and tissue engineering. Thanks to recent interdisciplinary studies, the materials developed have been intensively evaluated at animal level. Despite these efforts, less attention has been paid to what is really going on at the subcellular level during the interaction between a nanomaterial and a cell. As the proposed concept becomes more complex, the need for investigation of the dynamics of these materials at the cellular level becomes more prominent. For a deeper understanding of cellular events, fluorescent imaging techniques have been a powerful means whereby spatiotemporal information related to cellular events can be visualized as detectable fluorescent signals. To date, several excellent review papers have summarized the use of fluorescent imaging toolsets in cellular biology. However, applying these toolsets becomes a laborious process for those who are not familiar with imaging studies to engage with owing to the skills gap between them and cell biologists. This review aims to highlight the valuable essentials of fluorescent imaging as a tool for the development of effective biomaterials by introducing some cases including photothermal and photodynamic therapies. This distilled information will be a convenient short-cut for those who are keen to fabricate next generation biomaterials.

Magnetic Entropy as a Proposed Gating Mechanism for Magnetogenetic Ion Channels

Magnetically sensitive ion channels would allow researchers to better study how specific brain cells affect behavior in freely moving animals; however, recent reports of "magnetogenetic" ion channels based on biogenic ferritin nanoparticles have been questioned because known biophysical mechanisms cannot explain experimental observations. Here, we reproduce a weak magnetically mediated calcium response in HEK cells expressing a previously published TRPV4-ferritin fusion protein. We find that this magnetic sensitivity is attenuated when we reduce the temperature sensitivity of the channel but not when we reduce the mechanical sensitivity of the channel, suggesting that the magnetic sensitivity of this channel is thermally mediated. As a potential mechanism for this thermally mediated magnetic response, we propose that changes in the magnetic entropy of the ferritin particle can generate heat via the magnetocaloric effect and consequently gate the associated temperature-sensitive ion channel. Unlike other forms of magnetic heating, the magnetocaloric mechanism can cool magnetic particles during demagnetization. To test this prediction, we constructed a magnetogenetic channel based on the cold-sensitive TRPM8 channel. Our observation of a magnetic response in cold-gated channels is consistent with the magnetocaloric hypothesis. Together, these new data and our proposed mechanism of action provide additional resources for understanding how ion channels could be activated by low-frequency magnetic fields.

Light-Controlled Mammalian Cells and Their Therapeutic Applications in Synthetic Biology

The ability to remote control the expression of therapeutic genes in mammalian cells in order to treat disease is a central goal of synthetic biology-inspired therapeutic strategies. Furthermore, optogenetics, a combination of light and genetic sciences, provides an unprecedented ability to use light for precise control of various cellular activities with high spatiotemporal resolution. Recent work to combine optogenetics and therapeutic synthetic biology has led to the engineering of light-controllable designer cells, whose behavior can be regulated precisely and noninvasively. This Review focuses mainly on non-neural optogenetic systems, which are often used in synthetic biology, and their applications in genetic programing of mammalian cells. Here, a brief overview of the optogenetic tool kit that is available to build light-sensitive mammalian cells is provided. Then, recently developed strategies for the control of designer cells with specific biological functions are summarized. Recent translational applications of optogenetically engineered cells are also highlighted, ranging from in vitro basic research to in vivo light-controlled gene therapy. Finally, current bottlenecks, possible solutions, and future prospects for optogenetics in synthetic biology are discussed.

The synthesis and characterization of glutathione-modified superparamagnetic iron oxide nanoparticles and their distribution in rat brains after injection in substantia nigra

Glutathione-modified superparamagnetic iron oxide nanoparticles (GSH-SPIONs) were prepared by conjugating glutathione (GSH) on the surface of the PEG (Polyethylene glycol)/PEI (polyethyleneimine)-SPIONs which were synthesized by thermal decomposition method. Thermogravimetric analysis showed that the mass fraction of GSH on the surface of SPIONs was 30.64 wt%. GSH-SPIONs in PBS were injected into the substantia nigra of rat brains. The subcellular distributions of the nanoparticles in the brains was examined by the transmission electron microscope (TEM). A remarkable amount of GSH-SPIONs were found in vesicles inside cell bodies and axons, and in mitochondria. TEM pictures show that GSH-SPIONs enter the neuronal cells by endocytosis and travel through axoplasmic transport. GSH-SPIONs have great potential as drug delivery agents in the brain to treat diseases or study brain function via mitochondria-targeting way or axoplasmic transport way.

Perspectives of RAS and RHEB GTPase Signaling Pathways in Regenerating Brain Neurons

Cellular activation of RAS GTPases into the GTP-binding “ON” state is a key switch for regulating brain functions. Molecular protein structural elements of rat sarcoma (RAS) and RAS homolog protein enriched in brain (RHEB) GTPases involved in this switch are discussed including their subcellular membrane localization for triggering specific signaling pathways resulting in regulation of synaptic connectivity, axonal growth, differentiation, migration, cytoskeletal dynamics, neural protection, and apoptosis. A beneficial role of neuronal H-RAS activity is suggested from cellular and animal models of neurodegenerative diseases. Recent experiments on optogenetic regulation offer insights into the spatiotemporal aspects controlling RAS/mitogen activated protein kinase (MAPK) or phosphoinositide-3 kinase (PI3K) pathways. As optogenetic manipulation of cellular signaling in deep brain regions critically requires penetration of light through large distances of absorbing tissue, we discuss magnetic guidance of re-growing axons as a complementary approach. In Parkinson’s disease, dopaminergic neuronal cell bodies degenerate in the substantia nigra. Current human trials of stem cell-derived dopaminergic neurons must take into account the inability of neuronal axons navigating over a large distance from the grafted site into striatal target regions. Grafting dopaminergic precursor neurons directly into the degenerating substantia nigra is discussed as a novel concept aiming to guide axonal growth by activating GTPase signaling through protein-functionalized intracellular magnetic nanoparticles responding to external magnets.

Gold nanoparticles-enhanced ion-transmission mass spectrometry for highly sensitive detection of chemical warfare agent simulants

Gold nanoparticles (AuNPs)-embedded paper was coupled with ion-transmission mass spectrometry (MS) to enable the highly sensitive detection of chemical warfare agent (CWA) simulants in solutions. With the assistance of a low-temperature plasma (LTP) probe, we found that AuNPs were capable to enhance the ionization efficiencies of target analytes, with MS signal intensities surprisingly undergone an 800-fold increase under optimized conditions. The interaction between AuNPs and the radiofrequency electromagnetic field was believed to promote the desorption/ionization process, resulting in the unusual signal enhancement phenomenon. Based on this finding, we established a method for the rapid analysis of two simulants of nerve agents, dimethyl methylphosphonate (DMMP) and diisopropyl methylphosphonate (DIMP), with a dynamic range from 0.5 ng/mL to 100 ng/mL and detection limits of 0.1 ng/mL and 0.3 ng/mL, respectively. As sample pretreatments have been eliminated, the developed strategy is particularly promising for the on-site detection of CWAs considering its simple and rapid analytical workflow.

Remote control of glucose-sensing neurons to analyze glucose metabolism

The central nervous system relies on a continual supply of glucose, and must be able to detect glucose levels and regulate peripheral organ functions to ensure that its energy requirements are met. Specialized glucose-sensing neurons, first described half a century ago, use glucose as a signal and modulate their firing rates as glucose levels change. Glucose-excited neurons are activated by increasing glucose concentrations, while glucose-inhibited neurons increase their firing rate as glucose concentrations fall and decrease their firing rate as glucose concentrations rise. Glucose-sensing neurons are present in multiple brain regions and are highly expressed in hypothalamic regions, where they are involved in functions related to glucose homeostasis. However, the roles of glucose-sensing neurons in healthy and disease states remain poorly understood. Technologies that can rapidly and reversibly activate or inhibit defined neural populations provide invaluable tools to investigate how specific neural populations regulate metabolism and other physiological roles. Optogenetics has high temporal and spatial resolutions, requires implants for neural stimulation, and is suitable for modulating local neural populations. Chemogenetics, which requires injection of a synthetic ligand, can target both local and widespread populations. Radio- and magnetogenetics offer rapid neural activation in localized or widespread neural populations without the need for implants or injections. These tools will allow us to better understand glucose-sensing neurons and their metabolism-regulating circuits.

Photocatalytic Activity of Polymer Nanoparticles Modulates Intracellular Calcium Dynamics and Reactive Oxygen Species in HEK-293 Cells

Optical modulation of living cells activity by light-absorbing exogenous materials is gaining increasing interest, due to the possibility both to achieve high spatial and temporal resolution with a minimally invasive and reversible technique and to avoid the need of viral transfection with light-sensitive proteins. In this context, conjugated polymers represent ideal candidates for photo-transduction, due to their excellent optoelectronic and biocompatibility properties. In this work, we demonstrate that organic polymer nanoparticles, based on poly(3-hexylthiophene) conjugated polymer, establish a functional interaction with an in vitro cell model (Human Embryonic Kidney cells, HEK-293). They display photocatalytic activity in aqueous environment and, once internalized within the cell cytosol, efficiently generate reactive oxygen species (ROS) upon visible light excitation, without affecting cell viability. Interestingly, light-activated ROS generation deterministically triggers modulation of intracellular calcium ion flux, successfully controlled at the single cell level. In perspective, the capability of polymer NPs to produce ROS and to modulate Ca2+ dynamics by illumination on-demand, at non-toxic levels, may open the path to the study of biological processes with a gene-less approach and unprecedented spatio-temporal resolution, as well as to the development of new biotechnology tools for cell optical modulation.

Maximizing Specific Loss Power for Magnetic Hyperthermia by Hard-Soft Mixed Ferrites

Maximized specific loss power and intrinsic loss power approaching theoretical limits for alternating-current (AC) magnetic-field heating of nanoparticles are reported. This is achieved by engineering the effective magnetic anisotropy barrier of nanoparticles via alloying of hard and soft ferrites. 22 nm Co0.03 Mn0.28 Fe2.7 O4 /SiO2 nanoparticles reach a specific loss power value of 3417 W g-1metal at a field of 33 kA m-1 and 380 kHz. Biocompatible Zn0.3 Fe2.7 O4 /SiO2 nanoparticles achieve specific loss power of 500 W g-1metal and intrinsic loss power of 26.8 nHm2 kg-1 at field parameters of 7 kA m-1 and 380 kHz, below the clinical safety limit. Magnetic bone cement achieves heating adequate for bone tumor hyperthermia, incorporating an ultralow dosage of just 1 wt% of nanoparticles. In cellular hyperthermia experiments, these nanoparticles demonstrate high cell death rate at low field parameters. Zn0.3 Fe2.7 O4 /SiO2 nanoparticles show cell viabilities above 97% at concentrations up to 500 µg mL-1 within 48 h, suggesting toxicity lower than that of magnetite.

Wireless control of cellular function by activation of a novel protein responsive to electromagnetic fields

The Kryptopterus bicirrhis (glass catfish) is known to respond to electromagnetic fields (EMF). Here we tested its avoidance behavior in response to static and alternating magnetic fields stimulation. Using expression cloning we identified an electromagnetic perceptive gene (EPG) from the K. bicirrhis encoding a protein that responds to EMF. This EPG gene was cloned and expressed in mammalian cells, neuronal cultures and in rat’s brain. Immunohistochemistry showed that the expression of EPG is confined to the mammalian cell membrane. Calcium imaging in mammalian cells and cultured neurons expressing EPG demonstrated that remote activation by EMF significantly increases intracellular calcium concentrations, indicative of cellular excitability. Moreover, wireless magnetic activation of EPG in rat motor cortex induced motor evoked responses of the contralateral forelimb in vivo. Here we report on the development of a new technology for remote, non-invasive modulation of cell function.

Biomimetic Approaches Toward Smart Bio-hybrid Systems

Bio-integrated materials and devices can blur the interfaces between living and artificial systems. Microfluidics, bioelectronics and engineered nanostructures, with close interactions with biology at the cellular or tissue levels, have already yielded a spectrum of new applications. Many new designs emerge, including those of organ-on-a-chip systems, biodegradable implants, electroceutical devices, minimally invasive neuro-prosthetic tools, and soft robotics. In this review, we highlight a few recent advances on the fabrication and application of the smart bio-hybrid systems, with a particular emphasis on the three-dimensional (3D) bio-integrated devices that mimick the 3D feature of tissue scaffolds. Moreover, neurons integrated with engineered nanostructures for wireless neuromodulation and dynamic neural output will be briefly discussed. We will also go over the progress in the construction of cell-enabled soft robotics, where a tight coupling of the synthetic and biological parts is crucial for efficient functions. Finally, we summarize the approaches for enhancing bio-integration with biomimetic micro- and nanostructures.

Chemically Treated 3D Printed Polymer Scaffolds for Biomineral Formation

We present the synthesis of nylon-12 scaffolds by 3D printing and demonstrate their versatility as matrices for cell growth, differentiation, and biomineral formation. We demonstrate that the porous nature of the printed parts makes them ideal for the direct incorporation of preformed nanomaterials or material precursors, leading to nanocomposites with very different properties and environments for cell growth. Additives such as those derived from sources such as tetraethyl orthosilicate applied at a low temperature promote successful cell growth, due partly to the high surface area of the porous matrix. The incorporation of presynthesized iron oxide nanoparticles led to a material that showed rapid heating in response to an applied ac magnetic field, an excellent property for use in gene expression and, with further improvement, chemical-free sterilization. These methods also avoid changing polymer feedstocks and contaminating or even damaging commonly used selective laser sintering printers. The chemically treated 3D printed matrices presented herein have great potential for use in addressing current issues surrounding bone grafting, implants, and skeletal repair, and a wide variety of possible incorporated material combinations could impact many other areas.