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Michael Christiansen

Michael Christiansen
ETH Zurich | ETH Zürich · Department of Health Sciences and Technology

About

44
Publications
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1,649
Citations

Publications

Publications (44)
Article
Full-text available
Wireless deep brain stimulation of well-defined neuronal populations could facilitate the study of intact brain circuits and the treatment of neurological disorders. Here we demonstrate minimally-invasive and remote neural excitation through the activation of the heat-sensitive capsaicin receptor TRPV1 by magnetic nanoparticles. When exposed to alt...
Article
Alternating magnetic fields (AMFs) cause magnetic nanoparticles (MNPs) to dissipate heat while leaving surrounding tissue unharmed, a mechanism that serves as the basis for a variety of emerging biomedical technologies. Unfortunately, the challenges and costs of developing experimental setups commonly used to produce AMFs with suitable field amplit...
Article
Full-text available
Magnetic nanoparticles have garnered sustained research interest for their promise in biomedical applications including diagnostic imaging, triggered drug release, cancer hyperthermia, and neural stimulation. Many of these applications make use of heat dissipation by ferrite nanoparticles under alternating magnetic fields, with these fields acting...
Article
Biohybrid bacteria–based microrobots are increasingly recognized as promising externally controllable vehicles for targeted cancer therapy. Magnetic fields in particular have been used as a safe means to transfer energy and direct their motion. Thus far, the magnetic control strategies used in this context rely on poorly scalable magnetic field gra...
Article
Full-text available
The engineering space for magnetically manipulated biomedical microrobots is rapidly expanding. This includes synthetic, bioinspired, and biohybrid designs, some of which may eventually assume clinical roles aiding drug delivery or performing other therapeutic functions. Actuating these microrobots with rotating magnetic fields (RMFs) and the magne...
Article
Full-text available
Proteases, an important class of enzymes that cleave proteins and peptides, carry a wealth of potentially useful information. Devices to enable routine and cost effective measurement of their activity could...
Article
Full-text available
Rotating magnetic fields enable biomedical microrobots to overcome physiological barriers and promote extravasation and accumulation in tumors. Nevertheless, targeting deeply situated tumors requires suppression of off-target actuation in healthy tissue. Here, we investigate a control strategy for applying spatially selective torque density to micr...
Article
Full-text available
Swarms of soft microrobots controlled by minimally invasive magnetic fields show promise as biomedical agents. The collective behaviour of such swarms, governed by magnetic and hydrodynamic interactions, emerges from the properties of their individual constituents. The introduction of both magnetic and structural anisotropy into microrobots expands...
Article
Full-text available
Bacteria‐based agents are emerging as promising tools for cancer therapy due to their ability to actively target tumors, trigger localized inflammation, and induce tumor regression. There has been growing interest in using bacteria that are responsive to external cues, such as magnetic fields, to facilitate the formation of robust colonies in tumor...
Article
Full-text available
Mechanical cues play an important role in the metastatic cascade of cancer. Three-dimensional (3D) tissue matrices with tunable stiffness have been extensively used as model systems of the tumor microenvironment for physiologically relevant studies. Tumor-associated cells actively deform these matrices, providing mechanical cues to other cancer cel...
Conference Paper
In drug delivery, one key challenge is to minimize off- target accumulation in healthy regions, which can lead to toxicity or other associated complications. To address this challenge, drug delivery platforms can be designed either to localize the accumulation of active compounds to the target site or to selectively activate the portion that arrive...
Preprint
Full-text available
The engineering space for magnetically manipulated biomedical microrobots is rapidly expanding. This includes synthetic, bioinspired, and biohybrid designs, some of which may eventually assume clinical roles aiding drug delivery or performing other therapeutic functions. Actuating these microrobots with rotating magnetic fields (RMFs) and the magne...
Preprint
Full-text available
Rotating magnetic fields (RMFs), when used to actuate biomedical microrobots for targeted delivery to tumors, have been shown to enable them to overcome physiological barriers and promote their accumulation and penetration into tissue. Nevertheless, directly applying a RMF to a deeply situated target site also leads to off-target actuation in surro...
Preprint
Full-text available
Mechanical cues play an important role in the metastatic cascade of cancer. Three-dimensional (3D) tissue matrices with tunable stiffness have been extensively used as model systems of the tumor microenvironment for physiologically relevant studies. Tumor-associated cells actively deform these matrices, providing mechanical cues to other cancer cel...
Preprint
Full-text available
Swarms of soft microrobots controlled by minimally invasive magnetic fields show promise as potential biomedical agents. The collective behaviour of such swarms, governed by magnetic and hydrodynamic interactions, emerges from the properties of their individual constituents. The introduction of anisotropy into microrobots, including both magnetic a...
Article
Full-text available
Single domain magnetic nanoparticles are increasingly investigated as actuators of biological and chemical processes that respond to externally applied magnetic fields. Although their localized effects have often been attributed to nanoscale heating, recent experimental evidence suggests the need to consider alternative hypotheses. Here, using the...
Article
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...
Article
Fruit flies injected with magnetic nanoparticles and genetically modified to sensitize neural circuits to the rate of change in temperature have enabled subsecond behavioural responses to magnetic stimuli and multi-channel magnetic control.
Article
Enzymes are appealing diagnostic targets because of their centrality in human health and disease. Continuous efforts spanning several decades have yielded methods for magnetically detecting the interactions of enzymes with exogenous molecular substrates. Nevertheless, measuring enzymatic activity in vivo remains challenging due to background noise,...
Article
Full-text available
Ultrasound imaging with contrast agents, especially with lipid‐shelled microbubbles, has become a vital tool in clinical diagnostics. Efforts to adapt these agents for molecular imaging have typically focused on targeted binding. More recently, crosslinking the lipid shell to alter its mechanical properties, followed by decrosslinking upon exposure...
Preprint
Full-text available
Bacterial microrobots combining self-propulsion and magnetic guidance are increasingly recognized as promising drug delivery vehicles for targeted cancer therapy. Thus far, control strategies have either relied on poorly scalable magnetic field gradients or employed directing magnetic fields with propulsive forces limited by the bacterial motor. He...
Article
Full-text available
Deep brain stimulation (DBS) has long been used to alleviate symptoms in patients suffering from psychiatric and neurological disorders through stereotactically implanted electrodes that deliver current to subcortical structures via wired pacemakers. The application of DBS to modulate neural circuits is, however, hampered by its mechanical invasive...
Article
Full-text available
Cells continuously sense and react to mechanical cues from their surrounding matrix, which consists of a fibrous network of biopolymers that influences their fate and behavior. Several powerful methods employing magnetic control have been developed to assess the micromechanical properties within extracellular matrix (ECM) models hosting cells. Howe...
Article
Full-text available
Medication adherence is a medical and societal issue worldwide, with approximately half of patients failing to adhere to prescribed treatments. The goal of this Minireview is to examine how recent work on microfluidics for point‐of‐care diagnostics may be used to enhance adherence to medication. It specifically focuses on capillary microfluidics si...
Article
Full-text available
In recent decades, dysregulation of proteases and atypical proteolysis have become increasingly recognized as important hallmarks of cancer, driving community-wide efforts to explore the proteolytic landscape of oncologic disease. With more than 100 proteases currently associated with different aspects of cancer development and progression, there i...
Article
Medication adherence is a medical and societal issue worldwide, with approximately half of patients failing to adhere to prescribed treatments. This Minireview examines how recent work on capillary microfluidics for point‐of‐care diagnostics may be used to enhance adherence to medication. Abstract Medication adherence is a medical and societal iss...
Article
Neuroscience research has grown rapidly in recent years, driven at least in part by the emergence of tools and techniques that enable scientists to pose experimental questions that not long ago would have been unanswerable. Methods for triggering activity in the nervous systems of living animal models have proven particularly useful for mapping net...
Article
Full-text available
In article number 2003912, Simone Schuerle, Nima Mirkhani, and Michael G. Christiansen highlight the promise of magnetotactic bacteria as flow mediators under time‐varying magnetic fields. Selective drug delivery is a potential application made feasible by their unique magnetic and hydrodynamic properties. Superimposing a magnetostatic selection fi...
Article
Full-text available
Magnetic actuation offers a means to wirelessly control flow in ferrofluids for applications including microfluidic pumping and targeted drug delivery. Despite the promise of these concepts, practical use of synthetic ferrofluids as actuators of flow frequently requires high concentrations and is hindered by low ferrohydrodynamic coupling efficienc...
Preprint
Full-text available
Single domain magnetic nanoparticles are increasingly investigated as actuators of biological and chemical processes that respond to externally applied magnetic fields. Although their localized effects are frequently attributed to nanoscale heating, recent experimental evidence casts doubt on the existence of nanoscale temperature gradients in thes...
Article
Full-text available
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 strateg...
Article
Full-text available
Connecting neural circuit output to behaviour can be facilitated by the precise chemical manipulation of specific cell populations1,2. Engineered receptors exclusively activated by designer small molecules enable manipulation of specific neural pathways3,4. However, their application to studies of behaviour has thus far been hampered by a trade-off...
Article
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...
Thesis
Full-text available
Research on biomedical applications of magnetic nanoparticles (MNPs) has increasingly sought to demonstrate noninvasive actuation of cellular processes and material responses using heat dissipated in the presence of an alternating magnetic field (AMF). By modeling the dependence of hysteresis losses on AMF amplitude and constraining AMF conditions...
Article
Targeted cancer therapies require a precise determination of the underlying biological processes driving tumorigenesis within the complex tumor microenvironment. Therefore, new diagnostic tools that capture the molecular activity at the disease site in vivo are needed to better understand tumor behavior and ultimately maximize therapeutic responses...
Article
Hysteretic heat dissipation by magnetic nanoparticles (MNPs) in alternating magnetic fields (AMFs) allows these materials to act as local transducers of external stimuli. Commonly employed in cancer research, MNPs have recently found applications in remote control of heat-dependent cellular pathways. Here, a thermally labile linker chemistry is ada...
Article
From magnetic resonance imaging to cancer hyperthermia and wireless control of cell signaling, ferrite nanoparticles produced by thermal decomposition methods are ubiquitous across biomedical applications. While well-established synthetic protocols allow for precise control over the size and shape of the magnetic nanoparticles, structural defects w...
Article
On p. 2100, P. Anikeeva and co-workers demonstrate a technique using remotely triggered local heating to disaggregate deposits of the protein Aβ(1–42), which plays an important role in Alzheimer's Disease pathogenesis. The cover image shows neural network (green) overlayed with amyloid beta plaques (red) that are decorated with magnetic nanoparticl...
Article
Remotely triggered hysteretic heat dissipation by magnetic nanoparticles (MNPs) selectively attached to targeted proteins can be used to break up self-assembled aggregates. This magnetothermal approach is applied to the amyloid-β (Aβ) protein, which forms dense, insoluble plaques characteristic of Alzheimer's disease. Specific targeting of dilute M...
Article
Full-text available
Selective hysteretic heating of multiple collocated types of single domain magnetic nanoparticles (SDMNPs) by alternating magnetic fields (AMFs) may offer a useful tool for biomedical applications. The possibility of “magnetothermal multiplexing” has not yet been realized, in part due to prevalent use of linear response theory to model SDMNP heatin...
Article
Full-text available
Selective hysteretic heating of multiple collocated sets of single domain magnetic nanoparticles (SDMNPs) by alternating magnetic fields (AMFs) may offer a useful tool for biomedical applications. The possibility of magnetothermal multiplexing has not yet been realized, in part due to prevalent use of linear response theory to model SDMNP heating i...
Article
This article develops a set of design guidelines for maximizing heat dissipation characteristics of magnetic ferrite MFe2O4 (M = Mn, Fe, Co) nanoparticles in alternating magnetic fields. Using magnetic and structural nanoparticle characterization, we identify key synthetic parameters in the thermal decomposition of organometallic precursors that yi...
Article
Uncertainty about future energy and water supplies suggests a pressing need to develop efficient technologies for water desalination. Capacitive deionization (CDI), a method that captures ions in the electrical double layer (EDL) of an electrochemical capacitor, is a promising technology that can potentially fulfill those requirements. Similar to s...

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