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Methods in Enzymology 2020Various approaches to magneto-controlled biocatalytic enzyme reactions are discussed with specific example systems. Magnetic nano- and micro-size particles... (Review)
Review
Various approaches to magneto-controlled biocatalytic enzyme reactions are discussed with specific example systems. Magnetic nano- and micro-size particles functionalized with enzymes or cofactors/electron transfer mediators have been used to translocate the components of the biocatalytic processes and to activate/inhibit their reactions. Magneto-induced deposition of the functionalized particles on an electrode surface resulted in activation of bioelectrocatalytic reactions. On the other hand, magneto-induced removal of the particles from the electrode surface resulted in the inhibition of the electrochemical reactions. Aggregation/disaggregation of enzyme-modified magnetic nanoparticles resulted in different mechanisms of biocatalytic cascades, changing them reversibly between substrate diffusion and substrate channeling processes. Magnetohydrodynamic activation of bioelectrocatalytic processes allowed enhancement of a biofuel cell operation. Overall, a large variety of possible magneto-controlled enzyme reactions is briefly discussed, particularly emphasizing their applications in different bioelectronic systems.
Topics: Animals; Biocatalysis; Bioelectric Energy Sources; Biosensing Techniques; Electric Conductivity; Electrodes; Enzymes, Immobilized; Humans; Hydrodynamics; Magnetic Fields; Magnetics; Magnetite Nanoparticles; Magnets; Models, Molecular; Nanowires
PubMed: 31931981
DOI: 10.1016/bs.mie.2019.09.002 -
Journal of Controlled Release :... May 2019Magnetic drug targeting is a method by which magnetic drug carriers in the body are manipulated by external magnetic fields to reach the target area. This method is... (Review)
Review
Magnetic drug targeting is a method by which magnetic drug carriers in the body are manipulated by external magnetic fields to reach the target area. This method is potentially promising in applications for treatment of diseases like cancers, nervous system diseases, sudden sensorineural hearing loss, and so on, due to the advantages in that it can improve efficacy, reduce drug dosage and side effects. Therefore, it has received extensive attention in recent years. Successful magnetic drug targeting requires a good magnet system to guide the drug carriers to the target site. Up to date there have been many efforts to design the magnet systems for targeted drug delivery. However, there are few comprehensive reviews on these systems. Here we review the progresses made in this field. We summarized the systems already developed or proposed, and categorized them into two groups: static field magnet systems and varying field magnet systems. Based on the requirements for more powerful targeting performance, the prospects and the future research directions in this field are anticipated.
Topics: Animals; Delayed-Action Preparations; Drug Carriers; Drug Liberation; Hearing Loss; Humans; Magnetic Fields; Magnets; Nanoparticles; Neoplasms; Nervous System Diseases; Superconductivity
PubMed: 30946854
DOI: 10.1016/j.jconrel.2019.03.031 -
ACS Nano Apr 2020From single-pole magnetic tweezers to robotic magnetic-field generation systems, the development of magnetic micromanipulation systems, using electromagnets or permanent... (Review)
Review
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, 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.
Topics: Magnetic Fields; Magnetics; Magnets; Mechanotransduction, Cellular; Micromanipulation
PubMed: 32223274
DOI: 10.1021/acsnano.0c00959 -
Journal of Pediatric Gastroenterology... Sep 2022To review the clinical management and outcomes of magnet ingestions at a large tertiary children's hospital. To determine the association of frequency of high-powered...
OBJECTIVES
To review the clinical management and outcomes of magnet ingestions at a large tertiary children's hospital. To determine the association of frequency of high-powered magnet ingestion with the regulation of these magnets.
METHODS
Children <18 years who presented to the emergency room and were admitted to the Children's Hospital of Philadelphia for ingestion of single or multiple magnets from January 2008 to December 2020 were included. Demographics, symptoms, management, and outcomes were analyzed. The frequency of magnet ingestion was compared over 3 eras: (1) pre-ban (2008-2012), (2) intra-ban (2013-2016), and (3) post-ban (2017-2020).
RESULTS
There were 167 magnet ingestions, including 99 with multiple magnets. Most patients (59%) were male and median age was 6 (interquartile range, 3-9) years. Most single magnet ingestions (86%) were discharged with outpatient monitoring, and none experienced severe outcomes. Multiple magnet ingestions led to significant morbidity including hospitalizations (68%), endoscopic procedures (48%), surgical procedures (14%), and severe outcomes (12%). Most patients (75%) were asymptomatic, however, there was a higher risk of surgery and severe complications based on the presence of symptoms ( P = 0.003). The rate of surgical intervention was higher with ≥3 magnets (31.7%) compared to 2 magnets (2.4%) ( P < 0.003). Additionally, we found an 160% increase in children with magnet ingestions in the post-ban period ( P = 0.021).
CONCLUSIONS
Multiple magnet ingestion is associated with high morbidity and rate of severe outcomes. There is a relationship between public policy of magnet sale and frequency of magnet ingestion.
Topics: Child; Child, Preschool; Eating; Female; Foreign Bodies; Hospitals, Pediatric; Humans; Magnets; Male; Retrospective Studies; Tertiary Healthcare
PubMed: 35653435
DOI: 10.1097/MPG.0000000000003502 -
Ear and Hearing 2021Dislocation of the magnet inside the implanted component of a cochlear implant (CI) can be a serious risk for patients undergoing a magnetic resonance imaging (MRI)...
OBJECTIVES
Dislocation of the magnet inside the implanted component of a cochlear implant (CI) can be a serious risk for patients undergoing a magnetic resonance imaging (MRI) exam. CI manufacturers aim to reduce this risk either via the design of the implant magnet or magnet housing, or by advising a compression bandage and cover over the magnet. The aim of this study is to measure forces and torque on the magnet for different CI models and assess the effectiveness of the design and preventative measures on the probability of magnet dislocation.
DESIGN
Six CI models from four manufacturers covering all the current CI brands were included. Each model was positioned on a polystyrene head with compression bandage and magnet cover according to the recommendations of the manufacturer and tested for dislocation in a 1.5T whole-body MRI system. In addition, measurements of the displacement force in front of the MRI scanner and torque at the MRI scanner isocenter were obtained.
RESULTS
Chance of CI magnet dislocation was observed for two CI models. The design of the magnet or magnet housing of the other models proved sufficient to prevent displacement of the magnet. The main cause for magnet dislocation was found to be the rotational force resulting from the torque experienced inside the magnet bore, which ranges from 2.4 to 16.2 N between the models, with the displacement force being lower, ranging from 1.0 to 1.8 N.
CONCLUSIONS
In vitro testing shows that two CI models are prone to the risk of magnet dislocation. In these CI models, preparation before MRI with special compression bandage and a stiff cover are of importance. But these do not eliminate the risk of pain and dislocation requiring patient consulting before an MRI exam. Newer models show a better design resulting in a significantly reduced risk of magnet dislocation.
Topics: Cochlear Implantation; Cochlear Implants; Humans; Magnetic Resonance Imaging; Magnets; Torque
PubMed: 33657576
DOI: 10.1097/AUD.0000000000001013 -
Journal of Pediatric Gastroenterology... Apr 2023Magnet ingestion is a special category of foreign body ingestion associated with high levels of morbidity and mortality worldwide, particularly if it is associated with... (Review)
Review
Magnet ingestion is a special category of foreign body ingestion associated with high levels of morbidity and mortality worldwide, particularly if it is associated with staggered ingestion of multiple magnets or with simultaneous ingestion of other metallic foreign bodies, especially button batteries. A special category of magnet ingestion is the ingestion of earth magnets, which have higher levels of magnetism and therefore, potentially, carries a worse outcome. Legislative bodies, scientific Societies and community-led initiatives have been implemented worldwide with the aim of mitigating the effects of this growing, yet avoidable potential medical emergency. A scoping literature review summarized epidemiology, diagnosis, management, and prevention, including an algorithm for the diagnosis and management of magnet ingestion is presented and compared to previously published reviews and position papers (North American Society of Pediatric Gastroenterology, Hepatology and Nutrition, National Poison Center, Royal College of Emergency Medicine). The main emphasis of the algorithm is on identification of staggered/multiple magnet ingestion, and early joint gastroenterology and surgical consultation and management.
Topics: Child; Humans; Eating; Foreign Bodies; Gastroenterology; Gastrointestinal Tract; Magnets; Societies, Scientific
PubMed: 36947000
DOI: 10.1097/MPG.0000000000003702 -
Lab on a Chip Mar 2017A digital microfluidic platform manipulates droplets on an open surface. Magnetic digital microfluidics utilizes magnetic forces for actuation and offers unique... (Review)
Review
A digital microfluidic platform manipulates droplets on an open surface. Magnetic digital microfluidics utilizes magnetic forces for actuation and offers unique advantages compared to other digital microfluidic platforms. First, the magnetic particles used in magnetic digital microfluidics have multiple functions. In addition to serving as actuators, they also provide a functional solid substrate for molecule binding, which enables a wide range of applications in molecular diagnostics and immunodiagnostics. Second, magnetic digital microfluidics can be manually operated in a "power-free" manner, which allows for operation in low-resource environments for point-of-care diagnostics where even batteries are considered a luxury item. This review covers research areas related to magnetic digital microfluidics. This paper first summarizes the current development of magnetic digital microfluidics. Various methods of droplet manipulation using magnetic forces are discussed, ranging from conventional magnetic particle-based actuation to the recent development of ferrofluids and magnetic liquid marbles. This paper also discusses several new approaches that use magnetically controlled flexible substrates for droplet manipulation. In addition, we emphasize applications of magnetic digital microfluidics in biosensing and medical diagnostics, and identify the current limitations of magnetic digital microfluidics. We provide a perspective on possible solutions to close these gaps. Finally, the paper discusses the future improvement of magnetic digital microfluidics to explore potential new research directions.
Topics: Equipment Design; Magnetite Nanoparticles; Magnets; Microfluidic Analytical Techniques; Surface Properties
PubMed: 28220916
DOI: 10.1039/c7lc00025a -
Otology & Neurotology : Official... Jan 2022This study looks to examine how the development of diametric magnet cochlear implant devices (CIDs) has affected observed magnetic resonance imaging (MRI)-related... (Review)
Review
OBJECTIVES
This study looks to examine how the development of diametric magnet cochlear implant devices (CIDs) has affected observed magnetic resonance imaging (MRI)-related adverse events and MRI safety measures.
METHODS
A search of the Food and Drug Administration (FDA) Manufacturer and User Facility Device Experience (MAUDE) database was conducted using the product code "MCM" for "Cochlear implants." Reports were included for analysis if they involved MRI in recipients of cochlear implantation. Included reports were stratified into two cohorts by year: 2010 to 2014 and 2015 to 2020, reflecting the FDA approval of diametric magnet cochlear implants in 2015. Extracted event variables included implant manufacturer, adherence to MRI protocol, patient injuries, and device malfunctions.
RESULTS
The product code search query yielded a total of 27,305 reports, from which 584 reports were included for analysis. From 2010 to 2014, there were 109 adverse events and 30 pre-MRI explantations. Implant displacement was the most common device malfunction (n = 69, 87.3%), and pain was the most common patient injury (n = 16, 53.3%). From 2015 to 2020, there were 566 adverse events and 62 pre-MRI explantations. The most common device malfunction was implant displacement (n = 365, 94.6%) and pain was the most common patient injury (n = 114, 63.3%). Only 64/114 (56.1%) reports after 2015 reported adherence to the recommended MRI protocol. No adverse events occurred in patients with synchrony diametric-magnet CIDs.
CONCLUSION
Despite the advent of FDA-approved MRI-safe diametric magnet devices, implanted patients are still experiencing injury, explantation, and device malfunction, and providers are reporting poor compliance with MRI safety protocols.
Topics: Cochlear Implantation; Cochlear Implants; Databases, Factual; Humans; Magnetic Resonance Imaging; Magnets; Pain
PubMed: 34510115
DOI: 10.1097/MAO.0000000000003339 -
Cochlear Implants International Mar 2021The new CI600 series cochlear implants (Nucleus Profile™ Plus Series; CI) are more MRI (magnetic resonance imaging) compatible. The magnet's attraction force is...
The new CI600 series cochlear implants (Nucleus Profile™ Plus Series; CI) are more MRI (magnetic resonance imaging) compatible. The magnet's attraction force is lower, possibly posing a problem in patients needing a higher strength magnet due to increased skin thickness. This study aims to investigate the relationship between skin thickness and magnet strength in patients undergoing cochlear implantation. This cross-sectional study used data from 46 patients with cochlear implants. Data collected included age, body mass index, magnet strength used, pre-operative and post-operative imaging and skin thickness. There was a weak, positive correlation between magnet strength and skin thickness, which was not statistically significant ((46) = 0.149, = 0.324). There was a weak, positive correlation between magnet strength and body mass index, which was not statistically significant ((46) = 0.113, = 0.456). There was a moderate, positive correlation between body mass index and skin thickness, which was statistically significant ((46) = 0.362, = 0.012). The increased skin thickness in patients with higher body mass indexes, might mean that these patients will require a stronger magnet. There are concerns that the lower attraction force in the CI600 (Nucleus Profile™ Plus Series) may pose a retention problem for these patients. This might mean that discussions about skin flap reduction surgery are needed.
Topics: Cochlear Implantation; Cochlear Implants; Cross-Sectional Studies; Humans; Magnetic Resonance Imaging; Magnets; Surgical Flaps
PubMed: 32993474
DOI: 10.1080/14670100.2020.1824640 -
Zhongguo Yi Liao Qi Xie Za Zhi =... Nov 2021Ramping-up is the magnet current injection procedure which is under the control of resistance, voltage, current lead temperature, magnet pressure, temperature and so on....
Ramping-up is the magnet current injection procedure which is under the control of resistance, voltage, current lead temperature, magnet pressure, temperature and so on. In this procedure, the factors related to the stability of the magnet such as, magnet temperature, pressure and currents are constantly changing. This procedure is the main step which the magnet-quench occurs in. This study uses the data collected during 7 years and SIMENS MRI ramping-up theory, in order to help engineers understand the key factors to reduce the magnet quench during the ramping up procedure.
Topics: Magnets; Temperature
PubMed: 34862788
DOI: 10.3969/j.issn.1671-7104.2021.06.022