Minah Suh

Sungkyunkwan University, Sŏul, Seoul, South Korea

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Publications (61)

  • Jungmi Moon · Yejin Ha · Misun Kim · [...] · Minah Suh
    [Show abstract] [Hide abstract] ABSTRACT: In this work, we developed a dual amperometric/potentiometric microsensor for sensing nitric oxide (NO) and potassium ion (K(+)). The dual NO/K(+) sensor was prepared based on a dual recessed electrode possessing Pt (diameter, 50 μm) and Ag (diameter, 76.2 μm) microdisks. The Pt disk surface (WE1) was modified with electroplatinization and the following coating with fluorinated xerogel; and the Ag disk surface (WE2) was oxidized to AgCl on which K(+) ion selective membrane was loaded subsequent to the silanization. WE1 and WE2 of a dual microsensor were used for amperometric sensing of NO (106 ± 28 pA µM(-1), n = 10, at +0.85 V applied vs. Ag/AgCl) and for potentiometric sensing of K(+) (51.6 ± 1.9 mV pK(-1), n = 10), respectively, with high sensitivity. In addition, the sensor showed good selectivity over common biological interferents, sufficiently fast response time and relevant stability (within 6 h in-vivo experiment). The sensor had a small dimension (end plane diameter, 428 ± 97 μm, n = 20) and needle-like sharp geometry which allowed the sensor to be inserted in biological tissues. Taking advantage of this insertability, the sensor was applied for the simultaneous monitoring of NO and K(+) changes in living rat brain cortex at a depth of 1.19 ± 0.039 mm and near the spontaneous epileptic seizure focus. The seizures were induced with 4-aminopyridine injection onto the rat brain cortex. NO and K(+) levels were dynamically changed in clear correlation with the electrophysiological recording of seizures. This indicates that the dual NO/K(+) sensor's measurements well reflect membrane potential changes of neurons and associated cellular components of neurovascular coupling. The newly developed NO/K(+) dual microsensor showed the feasibility of real-time fast monitoring of dynamic changes of closely linked NO and K(+) in vivo.
    Article · Aug 2016 · Analytical Chemistry
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    Chaejeong Heo · Hyejin Park · Yong-Tae Kim · [...] · Minah Suh
    [Show abstract] [Hide abstract] ABSTRACT: Chronic in vivo imaging and electrophysiology are important for better understanding of neural functions and circuits. We introduce the new cranial window using soft, penetrable, elastic, and transparent, silicone-based polydimethylsiloxane (PDMS) as a substitute for the skull and dura in both rats and mice. The PDMS can be readily tailored to any size and shape to cover large brain area. Clear and healthy cortical vasculatures were observed up to 15 weeks post-implantation. Real-time hemodynamic responses were successfully monitored during sensory stimulation. Furthermore, the PDMS window allowed for easy insertion of microelectrodes and micropipettes into the cortical tissue for electrophysiological recording and chemical injection at any location without causing any fluid leakage. Longitudinal two-photon microscopic imaging of Cx3Cr1+/− GFP transgenic mice was comparable with imaging via a conventional glass-type cranial window, even immediately following direct intracortical injection. This cranial window will facilitate direct probing and mapping for long-term brain studies.
    Full-text Article · Jun 2016 · Scientific Reports
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    Chaejeong Heo · Hyejin Park · Yong-Tae Kim · [...] · Minah Suh
    Full-text Dataset · Jun 2016
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    Chaejeong Heo · Hyejin Park · Yong-Tae Kim · [...] · Minah Suh
    Full-text Dataset · Jun 2016
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    Chaejeong Heo · Hyejin Park · Yong-Tae Kim · [...] · Minah Suh
    Full-text Dataset · Jun 2016
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    Chaejeong Heo · Hyejin Park · Yong-Tae Kim · [...] · Minah Suh
    Full-text Dataset · Jun 2016
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    Chaejeong Heo · Hyejin Park · Yong-Tae Kim · [...] · Minah Suh
    Full-text Dataset · Jun 2016
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    Chaejeong Heo · Hyejin Park · Yong-Tae Kim · [...] · Minah Suh
    Full-text Dataset · Jun 2016
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    Jeongeun Sim · Areum Jo · Bok-Man Kang · [...] · Minah Suh
    [Show abstract] [Hide abstract] ABSTRACT: Ischemia can cause decreased cerebral neurovascular coupling, leading to a failure in the autoregulation of cerebral blood flow. This study aims to investigate the effect of varying degrees of ischemia on cerebral hemodynamic reactivity using in vivo real-time optical imaging. We utilized direct cortical stimulation to elicit hyper-excitable neuronal activation, which leads to induced hemodynamic changes in both the normal and middle cerebral artery occlusion (MCAO) ischemic stroke groups. Hemodynamic measurements from optical imaging accurately predict the severity of occlusion in mild and severe MCAO animals. There is neither an increase in cerebral blood volume nor in vessel reactivity in the ipsilateral hemisphere (I.H) of animals with severe MCAO. The pial artery in the contralateral hemisphere (C.H) of the severe MCAO group reacted more slowly than both hemispheres in the normal and mild MCAO groups. In addition, the arterial reactivity of the I.H in the mild MCAO animals was faster than the normal animals. Furthermore, artery reactivity is tightly correlated with histological and behavioral results in the MCAO ischemic group. Thus, in vivo optical imaging may offer a simple and useful tool to assess the degree of ischemia and to understand how cerebral hemodynamics and vascular reactivity are affected by ischemia.
    Full-text Article · Jun 2016
  • Yejin Ha · Jeongeun Sim · Youngmi Lee · Minah Suh
    [Show abstract] [Hide abstract] ABSTRACT: This paper reports the fabrication of an insertable amperometric dual microsensor and its application for the simultaneous and fast sensing of NO and CO during acutely induced seizures of living rat brain cortex. NO and CO are important signaling mediators, controlling cerebrovascular tone. The dual NO/CO sensor is prepared based on a dual microelectrode having Au-deposited Pt microdisk (WE1, 76-μm diameter) and Pt black-deposited Pt disk (WE2, 50-μm diameter). The different deposited metals for WE1 and WE2 allow the selective anodic detection of CO at WE1 (+0.2 V vs. Ag/AgCl) and that of NO at WE2 (+0.75 V vs. Ag/AgCl) with sufficient sensitivity. Fluorinated xerogel coating on this dual electrode provides exclusive selectivity over common biological interferents, along with fast response time. The miniaturized size (end plane diameter < 300 μm), and tapered needle-like sensor geometry make the sensor become insertable into biological tissues. The sensor is applied to simultaneously monitor dynamic changes of NO and CO levels in a living rat brain under acute seizure condition induced by 4-aminopyridine in cortical tissue near the area of seizure induction. In-tissue measurement shows clearly defined patterns of NO/CO changes, directly correlated with observed LFP signal. Current study verifies the feasibility of a newly developed NO/CO dual sensor for real-time fast monitoring of intimately connected NO and CO dynamics.
    Article · Feb 2016 · Analytical Chemistry
  • Dataset: c5an01804h1
    Dataset · Feb 2016
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    Sohee Lee · Bok-Man Kang · Min-Kyoo Shin · [...] · Minah Suh
    Full-text Dataset · Dec 2015
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    Sohee Lee · Bok-Man Kang · Min-Kyoo Shin · [...] · Minah Suh
    [Show abstract] [Hide abstract] ABSTRACT: Repeated stress is one of the major risk factors for cerebrovascular disease, including stroke and vascular dementia. However, the functional alterations in the cerebral hemodynamic response induced by chronic stress have not been clarified. Here, we investigated the in vivo cerebral hemodynamic changes and accompanying cellular and molecular changes in chronically stressed rats. After three weeks of restraint stress, the elicitation of stress was verified by behavioral despair in the forced swimming test and by physical indicators of stress. The evoked changes in the cerebral blood volume and pial artery responses following hindpaw electrical stimulation were measured using optical intrinsic signal imaging. We observed that, compared to the control group, animals under chronic restraint stress exhibited a decreased hemodynamic response, with a smaller pial arterial dilation in the somatosensory cortex during hindpaw electrical stimulation. The effect of chronic restraint stress on vasomodulator enzymes, including neuronal nitric oxide synthase (nNOS) and heme oxygenase-2 (HO-2), was assessed in the somatosensory cortex. Chronic restraint stress downregulated nNOS and HO-2 compared to the control group. In addition, we examined the subtypes of cells that can explain the environmental changes due to the decreased vasomodulators. The expression of parvalbumin in GABAergic interneurons and glutamate receptor-1 in neurons were decreased, whereas the microglial activation was increased. Our results suggest that the chronic stress-induced alterations in cerebral vascular function and the modulations of the cellular expression in the neuro-vasomodulatory system may be crucial contributing factors in the development of various vascular-induced conditions in the brain.
    Full-text Article · Dec 2015 · Frontiers in Neuroscience
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    [Show abstract] [Hide abstract] ABSTRACT: In this paper, we report the fabrication of a dual microsensor for sensing nitric oxide (NO) and calcium ions (Ca(2+)) and its application for simultaneous NO/Ca(2+) measurements in living rat kidney tissue. NO and Ca(2+) have very important physiological functions and are both intricately involved in many biological processes. The dual NO/Ca(2+) sensor is prepared based on a dual recessed electrode possessing Pt (diameter, 25 μm) and Ag (diameter, 76 μm) microdisks. The Pt disk surface (WE1) is electrodeposited with porous Pt black and then coated with fluorinated xerogel; and used for amperometric sensing of NO. The Ag disk surface (WE2) is chloridated to AgCl, followed by silanization and then Ca(2+) selective membrane loading; and used for potentiometric sensing of Ca(2+). The dual sensor exhibits high sensitivity of WE1 to NO (40.8 ± 6.5 pA μM(-1), n = 10) and reliable Nerntian response of WE2 to Ca(2+) changes (25.7 ± 0.5 mV pCa(-1), n = 10) with excellent selectivity to only NO and Ca(2+) over common interferents and reliable stability (up to ∼4 h tissue experiment). The prepared sensor is employed for real-time monitoring of the dynamic changes of NO and Ca(2+) levels of a rat kidney, which is induced by the administration of 10 mM l-N(G)-nitroarginine methyl ester (l-NAME, a NO synthase inhibitor). Due to the small sensor dimension, location-dependent analyses of NO and Ca(2+) are carried out at two different regions of a kidney (renal medulla and cortex). Higher NO and Ca(2+) levels are observed at the medulla than at the cortex. This study verifies the feasibility for real-time monitoring of intimately connected Ca(2+) and endogenous NO production; and also for localized concentration assessments of both NO and Ca(2+).
    Full-text Article · Nov 2015 · The Analyst
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    [Show abstract] [Hide abstract] ABSTRACT: Central nervous system (CNS)-infiltrating effector T cells play critical roles in the development and progression of multiple sclerosis (MS). However, current drugs for MS are very limited due to the difficulty of delivering drugs into the CNS. Here we identify a cell-permeable peptide, dNP2, which efficiently delivers proteins into mouse and human T cells, as well as various tissues. Moreover, it enters the brain tissue and resident cells through blood vessels by penetrating the tightly organized blood-brain barrier. The dNP2-conjugated cytoplasmic domain of cytotoxic T-lymphocyte antigen 4 (dNP2-ctCTLA-4) negatively regulates activated T cells and shows inhibitory effects on experimental autoimmune encephalomyelitis in both preventive and therapeutic mouse models, resulting in the reduction of demyelination and CNS-infiltrating T helper 1 and T helper 17 cells. Thus, this study demonstrates that dNP2 is a blood-brain barrier-permeable peptide and dNP2-ctCTLA-4 could be an effective agent for treating CNS inflammatory diseases such as MS.
    Full-text Article · Sep 2015 · Nature Communications
  • [Show abstract] [Hide abstract] ABSTRACT: To describe a toolkit of components for mathematical models of the relationship between cortical neural activity and space-resolved and time-resolved flows and volumes of oxygenated and deoxygenated hemoglobin motivated by optical intrinsic signal imaging (OISI). Both blood flow and blood volume and both oxygenated and deoxygenated hemoglobin and their interconversion are accounted for. Flow and volume are described by including analogies to both resistive and capacitive electrical circuit elements. Oxygenated and deoxygenated hemoglobin and their interconversion are described by generalization of Kirchhoff's laws based on well-mixed compartments. Mathematical models built from this toolkit are able to reproduce experimental single-stimulus OISI results that are described in papers from other research groups and are able to describe the response to multiple-stimuli experiments as a sublinear superposition of responses to the individual stimuli. The same assembly of tools from the toolkit but with different parameter values is able to describe effects that are considered distinctive, such as the presence or absence of an initial decrease in oxygenated hemoglobin concentration, indicating that the differences might be due to unique parameter values in a subject rather than different fundamental mechanisms.
    Article · Jun 2015 · Journal of Neural Engineering
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    Sarah S Park · Minyoung Hong · Yejin Ha · [...] · Minah Suh
    [Show abstract] [Hide abstract] ABSTRACT: This study reports real-time, in vivo functional measurement of nitric oxide (NO) and carbon monoxide (CO), two gaseous mediators in controlling cerebral blood flow. A dual electrochemical NO/CO microsensor enables us to probe the complex relationship between NO and CO in regulating cerebrovascular tone. Utilizing this dual sensor, we monitor in vivo change of NO and CO simultaneously during direct epidural electrical stimulation of a living rat brain cortex. Both NO and CO respond quickly to meet physiological needs. The neural system instantaneously increases the released amounts of NO and CO to compensate the abrupt, yet transient hypoxia that results from epidural electrical stimulation. Intrinsic-signal optical imaging confirms that direct electrical stimulation elicits robust, dynamic changes in cerebral blood flow, which must accompany NO and CO signaling. The addition of l-arginine (a substrate for NO synthase, NOS) results in increased NO generation and decreased CO production compared to control stimulation. On the other hand, application of the NOS inhibitor, l-N(G)-nitroarginine methyl ester (l-NAME), results in decreased NO release but increased CO production of greater magnitude. This observation suggests that the interaction between NO and CO release is likely not linear and yet, they are tightly linked vasodilators.
    Full-text Article · Mar 2015 · The Analyst
  • [Show abstract] [Hide abstract] ABSTRACT: Myocardial ischemia (MI) induces many changes in the body, including pH decrease and electrolyte imbalance. No obvious symptoms of MI appear until irreversible cellular injuries occur. Since early treatment is critical for recovery from ischemia, the development of reliable diagnostic tool is demanded to detect the early ischemic status. Ischemia modified albumin (IMA), formed by cleavage of the last two amino acids of the human serum albumin (HSA) N-terminus, has been considered so far as the most trustworthy and accurate marker for the investigation of ischemia. IMA levels are elevated in plasma within a few minutes of ischemic onset, and may last for up to 6 h. In the present study, we developed a novel assay for the examination of IMA levels to ameliorate the known albumin cobalt binding (ACB) test established previously. We observed a stronger copper ion bound to the HSA N-terminal peptide than cobalt ion by HPLC and ESI-TOF mass spectrometric analyses. The copper ion was employed with lucifer yellow (LY), a copper-specific reagent to develop a new albumin copper binding (ACuB) assay. The parameters capable of affecting the assay results were optimized, and the finally-optimized ACuB assay was validated. The result of the IMA level measurement in normal versus stroke rat serum suggests that the ACuB assay is likely to be a reliable and sensitive method for the detection of ischemic states.
    Article · Oct 2014 · Analytical Sciences
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    [Show abstract] [Hide abstract] ABSTRACT: Parkinson's disease (PD) is characterized by progressive dopaminergic cell loss in the substantia nigra (SN) and elevated iron levels demonstrated by autopsy. Direct visualization of iron with live imaging techniques has not yet been successful. The aim of this study is to visualize and quantify the distribution of cellular iron using an intrinsic iron hyperspectral fluorescence signal. The 1-methyl-4-phenylpyridinium (MPP+)-induced cellular model of PD was established in SHSY5Y cells exposed to iron with ferric ammonium citrate (FAC, 100 μM). The hyperspectral fluorescence signal of iron was examined using a high-resolution dark-field optical microscope system with signal absorption for the visible/near infrared spectral range. The 6-h group showed heavy cellular iron deposition compared with the 1-h group. The cellular iron was dispersed in a small particulate form, whereas the extracellular iron was aggregated. In addition, iron particles were found to be concentrated on the cell membrane/edge of shrunken cells. The iron accumulation readily occurred in MPP+-induced cells, which is consistent with previous studies demonstrating elevated iron levels in the SN. This direct iron imaging could be applied to analyze the physiological role of iron, and its application might be expanded to various neurological disorders involving metals, such as copper, manganese, or zinc.
    Full-text Article · May 2014 · Journal of Biomedical Optics
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    [Show abstract] [Hide abstract] ABSTRACT: We studied the electrophysiological, hemodynamic, and cytomorphological consequences of microhemorrhagic brain injury induced by a nanoscale iron injection. Of particular interest were the etiology, development, and treatment of epilepsy associated with this injury. We developed an animal model of chronic epilepsy using nanoscale injection into the adult mouse cortex. Although injection of nanoamounts of iron did not cause clear cell death or damage in the cortex, it elicited varying degrees of spontaneous epileptiform events that could be recorded under anesthesia 3 months postinjection. The influence of these chronic epileptiform events on neurovascular coupling was probed by directly stimulating the cortex ipsilateral to the epileptic focus and by measuring cerebral blood volume simultaneously in both hemispheres using intrinsic signal optical imaging. The ipsilateral hemodynamic response was dramatically lower in animals that exhibited longer, more frequent epileptiform events, but it was unchanged in animals displaying infrequent, short events. In contrast, the contralateral hemodynamic response was augmented in all iron-injected animals compared with the control group. These abnormal hemodynamic responses in chronically epileptic animals were correlated with the degree of reduction in the number of GABAergic interneurons. Therefore, nanoscale iron injection, which mimics some aspects of microhemorrhagic brain injury, generated chronic, yet varying, degrees of spontaneous epileptiform events. Moreover, the severity of the epileptiform events corresponded to the degree of reduction in GABAergic interneurons in the iron-injected hemisphere and the level of autoregulatory dysfunction of cerebral blood flow. © 2013 Wiley Periodicals, Inc.
    Full-text Article · Mar 2014 · Journal of Neuroscience Research

Publication Stats

682 Citations

Institutions

  • 2015
    • Sungkyunkwan University
      • Department of Biological Science
      Sŏul, Seoul, South Korea
  • 2007
    • New York Presbyterian Hospital
      • Department of Neurological Surgery
      New York City, New York, United States
  • 2005
    • Cornell University
      Итак, New York, United States