Brain Response to Interferential Current Compared with Alternating Current Stimulation.

Temporal interference (TI) stimulation, which utilizes multiple external electric fields with amplitude modulation for neural modulation, has emerged as a potential noninvasive brain stimulation methodology. However, the clinical application of TI stimulation is inhibited by its uncertain fundamental mechanisms, and research has previously been restricted to numerical simulations and immunohistology without considering the acute in vivo response of the neural circuit. To address the characterization and understanding of the mechanisms underlying the approach, we investigated instantaneous brainwide activation patterns in response to invasive interferential current (IFC) stimulation compared with low-frequency alternative current stimulation (ACS). Results demonstrated that IFC stimulation is capable of inducing regional neural responses and modulating brain networks; however, the activation threshold for significantly recruiting a neural response using IFC was higher (at least twofold) than stimulation via alternating current, and the spatial distribution of the activation signal was restricted. A distinct blood oxygenation level-dependent (BOLD) response pattern was observed, which could be accounted for by the activation of distinct types of cells, such as inhibitory cells, by IFC. These results suggest that IFC stimulation might not be as efficient as conventional brain modulation methods, especially when considering TI stimulation as a potential alternative for stimulating subcortical brain areas. Therefore, we argue that a future transcranial application of TI on human subjects should take these implications into account and consider other stimulation effects using this technique.

Application of Magnetic Nanoparticles for Rapid Detection and In Situ Diagnosis in Clinical Oncology.

Screening, monitoring, and diagnosis are critical in oncology treatment. However, there are limitations with the current clinical methods, notably the time, cost, and special facilities required for radioisotope-based methods. An alternative approach, which uses magnetic beads, offers faster analyses with safer materials over a wide range of oncological applications. Magnetic beads have been used to detect extracellular vesicles (EVs) in the serum of pancreatic cancer patients with statistically different EV levels in preoperative, postoperative, and negative control samples. By incorporating fluorescence, magnetic beads have been used to quantitatively measure prostate-specific antigen (PSA), a prostate cancer biomarker, which is sensitive enough even at levels found in healthy patients. Immunostaining has also been incorporated with magnetic beads and compared with conventional immunohistochemical methods to detect lesions; the results suggest that immunostained magnetic beads could be used for pathological diagnosis during surgery. Furthermore, magnetic nanoparticles, such as superparamagnetic iron oxide nanoparticles (SPIONs), can detect sentinel lymph nodes in breast cancer in a clinical setting, as well as those in gallbladder cancer in animal models, in a surgery-applicable timeframe. Ultimately, recent research into the applications of magnetic beads in oncology suggests that the screening, monitoring, and diagnosis of cancers could be improved and made more accessible through the adoption of this technology.

Sentinel lymph node biopsy with a handheld cordless magnetic probe following preoperative MR lymphography using superparamagnetic iron oxide for clinically N0 early oral cancer: A feasibility study.

PURPOSE: Radioisotope (RI) tracers are generally used for preoperative mapping of sentinel lymph node (SLN) and intraoperative detection with a portable γ probe. However, the use of RI has several limitations. Therefore, a method without RI is required for the widespread application of SLN biopsy. The purpose of this study was to evaluate the feasibility of SLN biopsy with a handheld cordless magnetic probe following magnetic resonance lymphography (MRL) using superparamagnetic iron oxide (SPIO) and for clinically N0 early oral cancer. MATERIALS AND METHODS: MRL using SPIO and SLNB with the handheld cordless magnetic probe were performed for 27 patients with clinically N0 early oral cancer. RESULTS: In all 27 patients (100%), SLNs were detected by MRL, and the total and mean number of SLNs were 73 and 2.7, respectively. All SLNs identified by MRL were detectable using the magnetic probe in all patients. CONCLUSIONS: SLNB with handheld cordless magnetic probe following preoperative SLN mapping by MRL using SPIO is feasible, without RI use, for neck management in cases of clinically N0 early oral cancer.

Magnetically Induced Temporal Interference for Focal and Deep-Brain Stimulation.

Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique that has been clinically applied for neural modulation. Conventional TMS systems are restricted by the trade-off between depth penetration and the focality of the induced electric field. In this study, we integrated the concept of temporal interference (TI) stimulation, which has been demonstrated as a non-invasive deep-brain stimulation method, with magnetic stimulation in a four-coil configuration. The attenuation depth and spread of the electric field were obtained by performing numerical simulation. Consequently, the proposed temporally interfered magnetic stimulation scheme was demonstrated to be capable of stimulating deeper regions of the brain model while maintaining a relatively narrow spread of the electric field, in comparison to conventional TMS systems. These results demonstrate that TI magnetic stimulation could be a potential candidate to recruit brain regions underneath the cortex. Additionally, by controlling the geometry of the coil array, an analogous relationship between the field depth and focality was observed, in the case of the newly proposed method. The major limitations of the methods, however, would be the considerable intensity and frequency of the input current, followed by the frustration in the thermal management of the hardware.

All-Optical Wide-Field Selective Imaging of Fluorescent Nanodiamonds in Cells, In Vivo and Ex Vivo.

Fluorescence imaging is a critical tool to understand the spatial distribution of biomacromolecules in cells and in vivo, providing information on molecular dynamics and interactions. Numerous valuable insights into biological systems have been provided by the specific detection of various molecular species. However, molecule-selective detection is often hampered by background fluorescence, such as cell autofluorescence and fluorescence leakage from molecules stained by other dyes. Here we describe a method for all-optical selective imaging of fluorescent nanodiamonds containing nitrogen-vacancy centers (NVCs) for wide-field fluorescence bioimaging. The method is based on the fact that the fluorescence intensity of NVCs strictly depends on the configuration of ground-state electron spins, which can be controlled by changing the pulse recurrence intervals of microsecond excitation laser pulses. Therefore, by using regulated laser pulses, we can oscillate the fluorescence from NVCs in a nanodiamond, while oscillating other optical signals in the opposite phase to NVCs. As a result, we can reconstruct a selective image of a nanodiamond by using a series of oscillated fluorescence images. We demonstrate application of the method to the selective imaging of nanodiamonds in live cells, in microanimals, and on a hippocampal slice culture obtained from a rat. Our approach potentially enables us to achieve high-contrast images of nanodiamond-labeled biomolecules with a signal-to-background ratio improved by up to 100-fold over the standard fluorescence image, thereby providing a more powerful tool for the investigation of molecular dynamics in cells and in vivo.

Magnetically Guided Localization Using a Guiding-Marker System® and a Handheld Magnetic Probe for Nonpalpable Breast Lesions: A Multicenter Feasibility Study in Japan.

Accurate pre-operative localization of nonpalpable lesions plays a pivotal role in guiding breast-conserving surgery (BCS). In this multicenter feasibility study, nonpalpable breast lesions were localized using a handheld magnetic probe (TAKUMI) and a magnetic marker (Guiding-Marker System®). The magnetic marker was preoperatively placed within the target lesion under ultrasound or stereo-guidance. Additionally, a dye was injected subcutaneously to indicate the extent of the tumor excision. Surgeons checked for the marker within the lesion using a magnetic probe. The magnetic probe could detect the guiding marker and accurately localize the target lesion intraoperatively. All patients with breast cancer underwent wide excision with a safety margin of ≥5 mm. The presence of the guiding-marker within the resected specimen was the primary outcome and the pathological margin status and re-excision rate were the secondary outcomes. Eighty-seven patients with nonpalpable lesions who underwent BCS, from January to March of 2019 and from January to July of 2020, were recruited. The magnetic marker was detected in all resected specimens. The surgical margin was positive only in 5/82 (6.1%) patients; these patients underwent re-excision. This feasibility study demonstrated that the magnetic guiding localization system is useful for the detection and excision of nonpalpable breast lesions.

Intraoperative laparoscopic detection of sentinel lymph nodes with indocyanine green and superparamagnetic iron oxide in a swine gallbladder cancer model.

Mapping of sentinel lymph nodes (SLNs) can enable less invasive surgery. However, mapping is challenging for cancers of difficult-to-access visceral organs, such as the gallbladder, because the standard method using radioisotopes (RIs) requires preoperative tracer injection. Indocyanine green (ICG) and superparamagnetic iron oxide (SPIO) have also been used as alternative tracers. In this study, we modified a previously reported magnetic probe for laparoscopic use and evaluated the feasibility of detecting SLNs of the gallbladder using a laparoscopic dual tracer method by injecting ICG and SPIO into five swine and one cancer-bearing swine. The laparoscopic probe identified SPIO nanoparticles in the nodes of 4/5 swine in situ, the magnetic field counts were 2.5-15.9 µT, and fluorescence was detected in SLNs in all five swine. ICG showed a visual lymph flow map, and SPIO more accurately identified each SLN with a measurable magnetic field quite similar to the RI. We then developed an advanced gallbladder cancer model with lymph node metastasis using recombination activating gene 2-knockout swine. We identified an SLN in the laparoscopic investigation, and the magnetic field count was 3.5 µT. The SLN was histologically determined to be one of the two metastatic lymph nodes. In conclusion, detecting the SLNs of gallbladder cancer in situ using a dual tracer laparoscopic technique with ICG and SPIO was feasible in a swine model.

Identification of Metal-Binding Peptides and Their Conjugation onto Nanoparticles of Superparamagnetic Iron Oxides and Liposomes.

Metallic materials are used for clinical medical devices such as vascular stents and coils to treat both ischemic and hemorrhagic vascular diseases. An antiplatelet drug is required to avoid thromboembolic complication until metallic surface is covered with a neo-endothelial cell layer. It is important to identify endothelial cell coverage on the metallic surface. However, it is difficult since there are no selective ligands. Here, we used the phage display method to identify peptide ligands that had high affinity for the metallic surface of Ni-Ti stents, Pt-W coils, and Co-Cr stents. The binding assay using fluorescence labeling revealed that several synthetic peptides could bind onto those surfaces. We also chose some oligopeptides for the conjugation onto superparamagnetic iron oxide (SPIO) nanoparticles and liposome-encapsulating SPIO nanoparticles and studied their ability to bind to the stent and coils. By SEM and fluorophotometry, we found that those modified SPIOs and liposomes were selectively bound onto those surfaces. In addition, both treated stents and coils could be detected by magnetic resonance imaging due to the magnetic artifact through the SPIOs and liposomes that were immobilized onto the surface. Thus, we identified metal-binding peptides which may enable to stop antiplatelet therapy after vascular stenting or coiling.

Moving a neodymium magnet promotes the migration of a magnetic tracer and increases the monitoring counts on the skin surface of sentinel lymph nodes in breast cancer.

BACKGROUND: We suspected that moving a small neodymium magnet would promote migration of the magnetic tracer to the sentinel lymph node (SLN). Higher monitoring counts on the skin surface before making an incision help us detect SLNs easily and successfully. The present study evaluated the enhancement of the monitoring count on the skin surface in SLN detection based on the magnet movement in a sentinel lymph node biopsy (SNB) using superparamagnetic iron oxide (SPIO) nanoparticles. METHODS: After induction of general anesthesia, superparamagnetic iron oxide nanoparticles were injected sub-dermally into the subareolar area or peritumorally. The neodymium magnet was moved over the skin from the injection site to the axilla to promote migration of the magnetic tracer without massage. A total of 62 patients were enrolled from February 2018 to November 2018: 13 cases were subjected to magnet movement 20 times (Group A), 8 were subjected to 1-min magnet movement (Group B), 26 were given a short (about 5 min) interval from injection to 1-min magnet movement (Group C), and 15 were given a long (about 25 min) interval before 1-min magnet movement using the magnetometer's head (Group D). In all cases, an SNB was conducted using both the radioisotope (RI) and SPIO methods. The monitoring counts on the skin surface were measured by a handheld magnetometer and compared among the four groups. Changes in the monitoring count by the interval and magnet movement were evaluated. RESULTS: The identification rates of the SPIO and RI methods were 100 and 95.2%, respectively. The mean monitoring counts of Group A, B, C, and D were 2.39 µT, 2.73 µT, 3.15 µT, and 3.92 µT, respectively (p < 0.0001; Kruskal-Wallis test). The monitoring counts were higher with longer magnet movement and with the insertion of an interval. Although there were no relationships between the monitoring count on the skin surface and clinicopathologic factors, magnet movement strongly influenced the monitoring count on the skin surface. CONCLUSION: Moving a small neodymium magnet is effective for promoting migration of a magnetic tracer and increasing monitoring counts on the skin surface. TRIAL REGISTRATION: UMIN, UMIN000029475. Registered 9 October 2017.

Magnetometer with nitrogen-vacancy center in a bulk diamond for detecting magnetic nanoparticles in biomedical applications.

We developed a novel magnetometer that employs negatively charged nitrogen-vacancy (NV-) centers in diamond, to detect the magnetic field generated by magnetic nanoparticles (MNPs) for biomedical applications. The compact probe system is integrated into a fiber-optics platform allowing for a compact design. To detect signals from the MNPs effectively, we demonstrated, for the first time, the application of an alternating current (AC) magnetic field generated by the excitation coil of several hundred microteslas for the magnetization of MNPs in diamond quantum sensing. In the lock-in detection system, the minimum detectable AC magnetic field (at a frequency of 1.025 kHz) was approximately 57.6 nT for one second measurement time. We were able to detect the micromolar concentration of MNPs at distances of a few millimeters. These results indicate that the magnetometer with the NV- centers can detect the tiny amounts of MNPs, thereby offering potential for future biomedical applications.

Development of Magnetic Probe for Sentinel Lymph Node Detection in Laparoscopic Navigation for Gastric Cancer Patients.

New laparoscopic sentinel lymph node navigation using a dedicated magnetic probe and magnetic nanoparticle tracer for gastric cancer patients allows minimally invasive surgeries. By identifying the sentinel lymph nodes containing magnetic nanoparticles, patients can avoid excessive lymph node extraction without nuclear facilities and radiation exposure. This paper describes the development of the laparoscopic magnetic probe, ACDC-probe, for laparoscopic sentinel lymph node identification utilizing the nonlinear response of the magnetic nanoparticles magnetized by an alternating magnetic field with a static magnetic field. For highly sensitive detection, the ratio of static to alternating magnetic fields was optimized to approximately 5. The longitudinal detection length was approximately 10 mm for 140 µg of iron, and the detectable amount of iron was approximately 280 ng at a distance of 1 mm. To demonstrate the feasibility of laparoscopic detection using the ACDC-probe and magnetic tracers, an experiment was performed on a wild swine. The gastric sentinel lymph node was clearly identified during laparoscopic navigation. These results suggest that the newly developed ACDC-probe is useful for laparoscopic sentinel lymph node detection and this magnetic technique appears to be a promising method for future sentinel lymph node navigation of gastric cancer patients.

Magnetically Promoted Rapid Immunofluorescence Staining for Frozen Tissue Sections.

Current immunohistochemistry methods for diagnosing abnormal cells, such as cancer cells, require multiple steps and can be relatively slow compared with intraoperative frozen hematoxylin and eosin staining, and are therefore rarely used for intraoperative examination. Thus, there is a need for novel rapid detection methods. We previously demonstrated that functionalized fluorescent ferrite beads (FF beads) magnetically promoted rapid immunoreactions. The aim of this study was to improve the magnetically promoted rapid immunoreaction method using antibody-coated FF beads and a magnet subjected to a magnetic field. Using frozen sections of xenograft samples of A431 human epidermoid cancer cells that express high levels of epidermal growth factor receptor (EGFR) and anti-EGFR antibody-coated FF beads, we reduced the magnetically promoted immunohistochemistry procedure to a 1-min reaction and 1-min wash. We also determined the optimum magnetic force for the antibody reaction (from 7.79 × 10-15 N to 3.35 × 10-15 N) and washing (4.78 × 10-16 N), which are important steps in this technique. Furthermore, we stained paraffin-embedded tissue arrays and frozen sections of metastatic breast cancer lymph nodes with anti-pan-cytokeratin antibody-coated FF beads to validate the utility of this system in clinical specimens. Under optimal conditions, this ultra-rapid immunostaining method may provide an ancillary method for pathological diagnosis during surgery. (J Histochem Cytochem 58:XXX-XXX, 2010).

Combined use of fluorescence with a magnetic tracer and dilution effect upon sentinel node localization in a murine model.

BACKGROUND: Sentinel node biopsy using radioisotope and blue dye remains a gold standard for axillary staging in breast cancer patients with low axillary burden. However, limitations in the use of radioisotopes have resulted in emergence of novel techniques. This is the first in vivo study to assess the feasibility of combining the two most common novel techniques of using a magnetic tracer and indocyanine green (ICG) fluorescence. MATERIALS AND METHODS: A total of 48 mice were divided into eight groups. Groups 1 and 2, the co-localization groups, received an injection of magnetic tracers (Resovist® and Sienna+®, respectively) and ICG fluorescence; distilled water was used as the solvent of ICG. Groups 3 and 4, the diluted injection groups, received an injection of magnetic tracers (Resovist and Sienna+, respectively) and saline for dilution. Groups 5, 6, and 7, the control groups, received magnetic tracer (Resovist, Sienna+) and ICG alone, respectively. Fluorescent intensity assessment and iron quantification of excised popliteal lymph nodes were performed. Group 1', a co-localization group, received an injection of magnetic tracers (Resovist) and ICG' fluorescence: saline was used as the solvent for ICG. RESULTS: Lymphatic uptake of all tracers was confined to the popliteal nodes only, with co-localization confirmed in all cases and no significant difference in fluorescent intensity or iron content of ex vivo nodes between the groups (except for Group 1'). There was no impact of dilution on the iron content in the diluted Sienna+ group, but it significantly enhanced Resovist uptake (P=0.005). In addition, there was a significant difference in iron content (P=0.003) in Group 1'. CONCLUSION: The combination of a magnetic tracer (Resovist or Sienna+) and ICG fluorescence is feasible for sentinel node biopsy and will potentially allow for precise transcutaneous node identification, in addition to accurate intraoperative assessment. This radioisotope-free "combined technique" warrants further assessment within a clinical trial.

Handheld magnetic probe with permanent magnet and Hall sensor for identifying sentinel lymph nodes in breast cancer patients.

The newly developed radioisotope-free technique based on magnetic nanoparticle detection using a magnetic probe is a promising method for sentinel lymph node biopsy. In this study, a novel handheld magnetic probe with a permanent magnet and magnetic sensor is developed to detect the sentinel lymph nodes in breast cancer patients. An outstanding feature of the probe is the precise positioning of the sensor at the magnetic null point of the magnet, leading to highly sensitive measurements unaffected by the strong ambient magnetic fields of the magnet. Numerical and experimental results show that the longitudinal detection length is approximately 10 mm, for 140 µg of iron. Clinical tests were performed, for the first time, using magnetic and blue dye tracers-without radioisotopes-in breast cancer patients to demonstrate the performance of the probe. The nodes were identified through transcutaneous and ex-vivo measurements, and the iron accumulation in the nodes was quantitatively revealed. These results show that the handheld magnetic probe is useful in sentinel lymph node biopsy and that magnetic techniques are widely being accepted as future standard methods in medical institutions lacking nuclear medicine facilities.