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Perillo ML, Gupta B, Siegenthaler JR, Christensen IE, Kepros B, Mitul A, Han M, Rechenberg R, Becker MF, Li W, Purcell EK. Evaluation of In Vitro Serotonin-Induced Electrochemical Fouling Performance of Boron Doped Diamond Microelectrode Using Fast-Scan Cyclic Voltammetry. BIOSENSORS 2024; 14:352. [PMID: 39056628 PMCID: PMC11274679 DOI: 10.3390/bios14070352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2024] [Revised: 07/16/2024] [Accepted: 07/17/2024] [Indexed: 07/28/2024]
Abstract
Fast-scan cyclic voltammetry (FSCV) is an electrochemical sensing technique that can be used for neurochemical sensing with high spatiotemporal resolution. Carbon fiber microelectrodes (CFMEs) are traditionally used as FSCV sensors. However, CFMEs are prone to electrochemical fouling caused by oxidative byproducts of repeated serotonin (5-HT) exposure, which makes them less suitable as chronic 5-HT sensors. Our team is developing a boron-doped diamond microelectrode (BDDME) that has previously been shown to be relatively resistant to fouling caused by protein adsorption (biofouling). We sought to determine if this BDDME exhibits resistance to electrochemical fouling, which we explored on electrodes fabricated with either femtosecond laser cutting or physical cleaving. We recorded the oxidation current response after 25 repeated injections of 5-HT in a flow-injection cell and compared the current drop from the first with the last injection. The 5-HT responses were compared with dopamine (DA), a neurochemical that is known to produce minimal fouling oxidative byproducts and has a stable repeated response. Physical cleaving of the BDDME yielded a reduction in fouling due to 5-HT compared with the CFME and the femtosecond laser cut BDDME. However, the femtosecond laser cut BDDME exhibited a large increase in sensitivity over the cleaved BDDME. An extended stability analysis was conducted for all device types following 5-HT fouling tests. This analysis demonstrated an improvement in the long-term stability of boron-doped diamond over CFMEs, as well as a diminishing sensitivity of the laser-cut BDDME over time. This work reports the electrochemical fouling performance of the BDDME when it is repeatedly exposed to DA or 5-HT, which informs the development of a chronic, diamond-based electrochemical sensor for long-term neurotransmitter measurements in vivo.
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Affiliation(s)
- Mason L. Perillo
- Department of Biomedical Engineering, Institute for Quantitative Health Science and Engineering, East Lansing, MI 48824, USA; (M.L.P.); (I.E.C.).; (W.L.)
| | - Bhavna Gupta
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA;
| | - James R. Siegenthaler
- Fraunhofer USA Center Midwest, Coatings and Diamond Technologies Division, East Lansing, MI 48824, USA; (J.R.S.); (B.K.); (R.R.); (M.F.B.)
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA; (A.M.); (M.H.)
| | - Isabelle E. Christensen
- Department of Biomedical Engineering, Institute for Quantitative Health Science and Engineering, East Lansing, MI 48824, USA; (M.L.P.); (I.E.C.).; (W.L.)
| | - Brandon Kepros
- Fraunhofer USA Center Midwest, Coatings and Diamond Technologies Division, East Lansing, MI 48824, USA; (J.R.S.); (B.K.); (R.R.); (M.F.B.)
| | - Abu Mitul
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA; (A.M.); (M.H.)
| | - Ming Han
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA; (A.M.); (M.H.)
| | - Robert Rechenberg
- Fraunhofer USA Center Midwest, Coatings and Diamond Technologies Division, East Lansing, MI 48824, USA; (J.R.S.); (B.K.); (R.R.); (M.F.B.)
| | - Michael F. Becker
- Fraunhofer USA Center Midwest, Coatings and Diamond Technologies Division, East Lansing, MI 48824, USA; (J.R.S.); (B.K.); (R.R.); (M.F.B.)
| | - Wen Li
- Department of Biomedical Engineering, Institute for Quantitative Health Science and Engineering, East Lansing, MI 48824, USA; (M.L.P.); (I.E.C.).; (W.L.)
- Fraunhofer USA Center Midwest, Coatings and Diamond Technologies Division, East Lansing, MI 48824, USA; (J.R.S.); (B.K.); (R.R.); (M.F.B.)
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA; (A.M.); (M.H.)
| | - Erin K. Purcell
- Department of Biomedical Engineering, Institute for Quantitative Health Science and Engineering, East Lansing, MI 48824, USA; (M.L.P.); (I.E.C.).; (W.L.)
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA;
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA; (A.M.); (M.H.)
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Yeoman MS, Fidalgo S, Marcelli G, Patel BA. Amperometry approach curve profiling to understand the regulatory mechanisms governing the concentration of intestinal extracellular serotonin. Sci Rep 2024; 14:10479. [PMID: 38714793 PMCID: PMC11076564 DOI: 10.1038/s41598-024-61296-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Accepted: 05/03/2024] [Indexed: 05/10/2024] Open
Abstract
Enterochromaffin (EC) cells located within the intestinal mucosal epithelium release serotonin (5-HT) to regulate motility tones, barrier function and the immune system. Electroanalytical methodologies have been able to monitor steady state basal extracellular 5-HT levels but are unable to provide insight into how these levels are influenced by key regulatory processes such as release and uptake. We established a new measurement approach, amperometry approach curve profiling, which monitors the extracellular 5-HT level at different electrode-tissue (E-T) distances. Analysis of the current profile can provide information on contributions of regulatory components on the observed extracellular 5-HT level. Measurements were conducted from ex vivo murine ileum and colon using a boron-doped diamond (BDD) microelectrode. Amperometry approach curve profiling coupled with classical pharmacology demonstrated that extracellular 5-HT levels were significantly lower in the colon when compared to the ileum. This difference was due to a greater degree of activity of the 5-HT transporter (SERT) and a reduced amount of 5-HT released from colonic EC cells. The presence of an inhibitory 5-HT4 autoreceptor was observed in the colon, where a 40% increase in extracellular 5-HT was the half maximal inhibitory concentration for activation of the autoreceptor. This novel electroanalytical approach allows estimates of release and re-uptake and their contribution to 5-HT extracellular concentration from intestinal tissue be obtained from a single series of measurements.
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Affiliation(s)
- Mark S Yeoman
- School of Applied Sciences, University of Brighton, Huxley Building, Brighton, BN2 4GJ, UK
- Centre for Lifelong Health, University of Brighton, Huxley Building, Brighton, BN2 4GJ, UK
| | - Sara Fidalgo
- School of Applied Sciences, University of Brighton, Huxley Building, Brighton, BN2 4GJ, UK
- Centre for Lifelong Health, University of Brighton, Huxley Building, Brighton, BN2 4GJ, UK
| | - Gianluca Marcelli
- School of Engineering, University of Kent, Jennison Building, Canterbury, CT2 7NZ, UK
| | - Bhavik Anil Patel
- School of Applied Sciences, University of Brighton, Huxley Building, Brighton, BN2 4GJ, UK.
- Centre for Lifelong Health, University of Brighton, Huxley Building, Brighton, BN2 4GJ, UK.
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3
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Zhao Y, Jin KQ, Li JD, Sheng KK, Huang WH, Liu YL. Flexible and Stretchable Electrochemical Sensors for Biological Monitoring. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2305917. [PMID: 37639636 DOI: 10.1002/adma.202305917] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 08/23/2023] [Indexed: 08/31/2023]
Abstract
The rise of flexible and stretchable electronics has revolutionized biosensor techniques for probing biological systems. Particularly, flexible and stretchable electrochemical sensors (FSECSs) enable the in situ quantification of numerous biochemical molecules in different biological entities owing to their exceptional sensitivity, fast response, and easy miniaturization. Over the past decade, the fabrication and application of FSECSs have significantly progressed. This review highlights key developments in electrode fabrication and FSECSs functionalization. It delves into the electrochemical sensing of various biomarkers, including metabolites, electrolytes, signaling molecules, and neurotransmitters from biological systems, encompassing the outer epidermis, tissues/organs in vitro and in vivo, and living cells. Finally, considering electrode preparation and biological applications, current challenges and future opportunities for FSECSs are discussed.
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Affiliation(s)
- Yi Zhao
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Kai-Qi Jin
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Jing-Du Li
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Kai-Kai Sheng
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Wei-Hua Huang
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Yan-Ling Liu
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
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4
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Mary SM, Ramakrishnan M, Sudalaimani Paulpandian SD, Rajeshkumar S, Pringle J. Application of nanoparticles in Dentistry. Bioinformation 2023; 19:14-18. [PMID: 37720271 PMCID: PMC10504510 DOI: 10.6026/97320630019014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Revised: 01/30/2023] [Accepted: 01/31/2023] [Indexed: 09/19/2023] Open
Abstract
Nanoparticles(NPs) are of particle sizes lesser than 100nm and are insoluble the field which deal with the handling of these particles is coined as "Nanotechnology" as their particle size is smaller, they can penetrate easily therefore they are applied in various medical fields, drug delivery and in dentistry as they have antimicrobial property, reduces friction, anti-inflammatory and antioxidant property. Many studies have been done to evaluate its application and its cytotoxicity by varying its concentration and various studies have been done to evaluate its physical property. Therefore, it is of interest to describe concepts of nanoparticles, mode of action, tissue reaction and its application in orthodontics.
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Affiliation(s)
- Sheloni Missier Mary
- Saveetha Dental College and Hospital, SIMATS, Saveetha University, Chennai, Tamilnadu, India
| | - Mahesh Ramakrishnan
- Saveetha Dental College and Hospital, SIMATS, Saveetha University, Chennai, Tamilnadu, India
| | | | - Shanmugam Rajeshkumar
- Saveetha Dental College and Hospital, SIMATS, Saveetha University, Chennai, Tamilnadu, India
| | - Jebilla Pringle
- Department of Orthodontics, Rajas Dental College and Hospital, Kavalkinaru, Tamilnadu, India
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Liu R, Feng ZY, Li D, Jin B, Yan Lan, Meng LY. Recent trends in carbon-based microelectrodes as electrochemical sensors for neurotransmitter detection: A review. Trends Analyt Chem 2022. [DOI: 10.1016/j.trac.2022.116541] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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6
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France M, Galligan JJ, Swain GM. In vitro electrochemical measurement of serotonin release in the human jejunum mucosa using a diamond microelectrode. Analyst 2022; 147:2523-2532. [PMID: 35543208 PMCID: PMC9599047 DOI: 10.1039/d2an00487a] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report herein on the use of a boron-doped diamond microelectrode (DME) to record oxidation currents in vitro associated with the release of serotonin from enterochromaffin cells in the epithelium of the human intestinal mucosa.
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Affiliation(s)
- Marion France
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - James J. Galligan
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824, USA
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
| | - Greg M. Swain
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
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7
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Liu YL, Chen Y, Fan WT, Cao P, Yan J, Zhao XZ, Dong WG, Huang WH. Mechanical Distension Induces Serotonin Release from Intestine as Revealed by Stretchable Electrochemical Sensing. Angew Chem Int Ed Engl 2020; 59:4075-4081. [PMID: 31829491 DOI: 10.1002/anie.201913953] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 12/04/2019] [Indexed: 12/17/2022]
Abstract
The role of endogenous serotonin (5-HT) in gastrointestinal motility is still highly controversial. Although electrochemical techniques allow for direct and real-time recording of biomolecules, the dynamic monitoring of 5-HT release from elastic and tubular intestine during motor reflexes remains a great challenge because of the specific peristalsis patterns and inevitable passivation of the sensing interface. A stretchable sensor with antifouling and decontamination properties was assembled from gold nanotubes, titanium dioxide nanoparticles, and carbon nanotubes. The sandwich-like structure endowed the sensor with satisfying mechanical stability and electrochemical performance, high resistance against physical adsorption, and superior efficiency in the photodegradation of biofouling molecules. Insertion of the sensor into the lumen of rat ileum (the last section of the small intestine) successfully mimics intestinal peristalsis, and simultaneous real-time monitoring of distension-evoked 5-HT release was possible for the first time. Our results unambiguously reveal that mechanical distension of the intestine induces endogenous 5-HT overflow, and 5-HT level is closely associated with the physiological or pathological states of the intestine.
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Affiliation(s)
- Yan-Ling Liu
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Yan Chen
- Key Laboratory of Hubei Province for Digestive System Disease, Department of Gastroenterology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Wen-Ting Fan
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Pan Cao
- Key Laboratory of Hubei Province for Digestive System Disease, Department of Gastroenterology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Jing Yan
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Xing-Zhong Zhao
- Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, 430072, China
| | - Wei-Guo Dong
- Key Laboratory of Hubei Province for Digestive System Disease, Department of Gastroenterology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Wei-Hua Huang
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
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8
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Liu Y, Chen Y, Fan W, Cao P, Yan J, Zhao X, Dong W, Huang W. Mechanical Distension Induces Serotonin Release from Intestine as Revealed by Stretchable Electrochemical Sensing. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201913953] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Yan‐Ling Liu
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education) College of Chemistry and Molecular Sciences Wuhan University Wuhan 430072 China
| | - Yan Chen
- Key Laboratory of Hubei Province for Digestive System Disease Department of Gastroenterology Renmin Hospital of Wuhan University Wuhan 430060 China
| | - Wen‐Ting Fan
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education) College of Chemistry and Molecular Sciences Wuhan University Wuhan 430072 China
| | - Pan Cao
- Key Laboratory of Hubei Province for Digestive System Disease Department of Gastroenterology Renmin Hospital of Wuhan University Wuhan 430060 China
| | - Jing Yan
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education) College of Chemistry and Molecular Sciences Wuhan University Wuhan 430072 China
| | - Xing‐Zhong Zhao
- Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education School of Physics and Technology Wuhan University Wuhan 430072 China
| | - Wei‐Guo Dong
- Key Laboratory of Hubei Province for Digestive System Disease Department of Gastroenterology Renmin Hospital of Wuhan University Wuhan 430060 China
| | - Wei‐Hua Huang
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education) College of Chemistry and Molecular Sciences Wuhan University Wuhan 430072 China
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9
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Fan B, Rusinek CA, Thompson CH, Setien M, Guo Y, Rechenberg R, Gong Y, Weber AJ, Becker MF, Purcell E, Li W. Flexible, diamond-based microelectrodes fabricated using the diamond growth side for neural sensing. MICROSYSTEMS & NANOENGINEERING 2020; 6:42. [PMID: 32685185 PMCID: PMC7355183 DOI: 10.1038/s41378-020-0155-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 03/06/2020] [Accepted: 03/25/2020] [Indexed: 05/02/2023]
Abstract
Diamond possesses many favorable properties for biochemical sensors, including biocompatibility, chemical inertness, resistance to biofouling, an extremely wide potential window, and low double-layer capacitance. The hardness of diamond, however, has hindered its applications in neural implants due to the mechanical property mismatch between diamond and soft nervous tissues. Here, we present a flexible, diamond-based microelectrode probe consisting of multichannel boron-doped polycrystalline diamond (BDD) microelectrodes on a soft Parylene C substrate. We developed and optimized a wafer-scale fabrication approach that allows the use of the growth side of the BDD thin film as the sensing surface. Compared to the nucleation surface, the BDD growth side exhibited a rougher morphology, a higher sp 3 content, a wider water potential window, and a lower background current. The dopamine (DA) sensing capability of the BDD growth surface electrodes was validated in a 1.0 mM DA solution, which shows better sensitivity and stability than the BDD nucleation surface electrodes. The results of these comparative studies suggest that using the BDD growth surface for making implantable microelectrodes has significant advantages in terms of the sensitivity, selectivity, and stability of a neural implant. Furthermore, we validated the functionality of the BDD growth side electrodes for neural recordings both in vitro and in vivo. The biocompatibility of the microcrystalline diamond film was also assessed in vitro using rat cortical neuron cultures.
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Affiliation(s)
- Bin Fan
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI USA
| | - Cory A. Rusinek
- Fraunhofer USA Center for Coatings and Diamond Technologies, East Lansing, MI USA
| | - Cort H. Thompson
- Department of Biomedical Engineering, Michigan State University, East Lansing, MI USA
| | - Monica Setien
- Department of Biomedical Engineering, Michigan State University, East Lansing, MI USA
| | - Yue Guo
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI USA
| | - Robert Rechenberg
- Fraunhofer USA Center for Coatings and Diamond Technologies, East Lansing, MI USA
| | - Yan Gong
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI USA
| | - Arthur J. Weber
- Department of Physiology, Michigan State University, East Lansing, MI USA
| | - Michael F. Becker
- Fraunhofer USA Center for Coatings and Diamond Technologies, East Lansing, MI USA
| | - Erin Purcell
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI USA
- Department of Biomedical Engineering, Michigan State University, East Lansing, MI USA
| | - Wen Li
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI USA
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10
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Sangsiri S, Xu H, Fernandes R, Fink GD, Lujan HL, DiCarlo SE, Galligan JJ. Spinal cord injury alters purinergic neurotransmission to mesenteric arteries in rats. Am J Physiol Heart Circ Physiol 2019; 318:H223-H237. [PMID: 31774690 DOI: 10.1152/ajpheart.00525.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Complications associated with spinal cord injury (SCI) result from unregulated reflexes below the lesion level. Understanding neurotransmission distal to the SCI could improve quality of life by mitigating complications. The long-term impact of SCI on neurovascular transmission is poorly understood, but reduced sympathetic activity below the site of SCI enhances arterial neurotransmission (1). We studied sympathetic neurovascular transmission using a rat model of long-term paraplegia (T2-3) and tetraplegia (C6-7). Sixteen weeks after SCI, T2-3 and C6-7 rats had lower blood pressure (BP) than sham rats (103 ± 2 and 97 ± 4 vs. 117 ± 6 mmHg, P < 0.05). T2-3 rats had tachycardia (410 ± 6 beats/min), and C6-7 rats had bradycardia (299 ± 10 beats/min) compared with intact rats (321 ± 4 beats/min, P < 0.05). Purinergic excitatory junction potentials (EJPs) were measured in mesenteric arteries (MA) using microlectrodes, and norepinephrine (NE) release was measured using amperometry. NE release was similar in all groups, while EJP frequency-response curves from T2-3 and C6-7 rats were left-shifted vs. sham rats. EJPs in T2-3 and C6-7 rats showed facilitation followed by run-down during stimulation trains (10 Hz, 50 stimuli). MA reactivity to exogenous NE and ATP was similar in all rats. In T2-3 and C6-7 rats, NE content was increased in left cardiac ventricles compared with intact rats, but was not changed in MA, kidney, or spleen. Our data indicate that peripheral purinergic, but not adrenergic, neurotransmission increases following SCI via enhanced ATP release from periarterial nerves. Sympathetic BP support is reduced after SCI, but improving neurotransmitter release might maintain cardiovascular stability in individuals living with SCI.NEW & NOTEWORTHY This study revealed increased purinergic, but not noradrenergic, neurotransmission to mesenteric arteries in rats with spinal cord injury (SCI). An increased releasable pool of ATP in periarterial sympathetic nerves may contribute to autonomic dysreflexia following SCI, suggesting that purinergic neurotransmission may be a therapeutic target for maintaining stable blood pressure in individuals living with SCI. The selective increase in ATP release suggests that ATP and norepinephrine may be stored in separate synaptic vesicles in periarterial sympathetic varicosities.
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Affiliation(s)
- Sutheera Sangsiri
- Department of Preclinical Science, Thammasat University, Pathumthani, Thailand.,Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - Hui Xu
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan.,Neuroscience Program, Michigan State University, East Lansing, Michigan
| | - Roxanne Fernandes
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - Greg D Fink
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan.,Neuroscience Program, Michigan State University, East Lansing, Michigan
| | - Heidi L Lujan
- Department of Physiology, Michigan State University, East Lansing, Michigan
| | - Stephen E DiCarlo
- Department of Physiology, Michigan State University, East Lansing, Michigan
| | - James J Galligan
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan.,Neuroscience Program, Michigan State University, East Lansing, Michigan
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11
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Asai K, Yamamoto T, Nagashima S, Ogata G, Hibino H, Einaga Y. An electrochemical aptamer-based sensor prepared by utilizing the strong interaction between a DNA aptamer and diamond. Analyst 2019; 145:544-549. [PMID: 31764923 DOI: 10.1039/c9an01976f] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Stable and continuous biosensing of electroactive species in vivo has been achieved by using boron-doped diamond (BDD) electrodes owing to their outstanding electrochemical properties. However, the present problem in biosensing using BDD electrodes is how to specifically measure/detect the target molecules, including electrochemically inactive species. A possible solution is to fabricate an electrochemical aptamer-based (E-AB) sensor using a BDD electrode. In a preliminary investigation, we found that DNA aptamers strongly adsorb on the BDD surface and the aptamer-adsorbed BDD apparently worked as an E-AB sensor. The present study reports the performance of the aptamer-adsorbed BDD electrode as an E-AB sensor. Doxorubicin (DOX), a widely used chemotherapeutic, was chosen as a target molecule. The sensor could be prepared by just dipping BDD in an aptamer solution for only 30 min, and the electrochemical signals were dependent on the DOX concentration. The adsorption of DNA was strong enough for continuous measurements and even a sonication treatment. Such behaviors were not observed when using gold and glassy carbon electrodes. In a kinetic measurement, distortion by a sluggish response was observed for both association and dissociation phases, indicating that the interaction between DOX and the aptamer involves several kinetic processes. By fitting to a Langmuir isotherm, a limit of detection of 49 nM and a maximum detectable concentration of 2.3 μM were obtained. Although the sensitivity was lower than those of the well-established E-AB sensors of gold, the values are within a drug's therapeutic range. Overall, the present work demonstrates that a DNA aptamer and a BDD electrode is an effective combination for an E-AB sensor with stable sensitivity, and a wide variety of DNA aptamers can be applied without any special treatment.
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Affiliation(s)
- Kai Asai
- Department of Chemistry, Keio University, 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522, Japan.
| | - Takashi Yamamoto
- Department of Chemistry, Keio University, 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522, Japan.
| | - Shinichi Nagashima
- Department of Chemistry, Keio University, 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522, Japan.
| | - Genki Ogata
- Department of Molecular Physiology, Niigata University School of Medicine, Niigata 951-8510, Japan
| | - Hiroshi Hibino
- Department of Molecular Physiology, Niigata University School of Medicine, Niigata 951-8510, Japan
| | - Yasuaki Einaga
- Department of Chemistry, Keio University, 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522, Japan. and ACCEL, Japan Science and Technology Agency, 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522, Japan
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12
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Hamzah HH, Keattch O, Yeoman MS, Covill D, Patel BA. Three-Dimensional-Printed Electrochemical Sensor for Simultaneous Dual Monitoring of Serotonin Overflow and Circular Muscle Contraction. Anal Chem 2019; 91:12014-12020. [DOI: 10.1021/acs.analchem.9b02958] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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13
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Damodhar Ghime, Prabir Ghosh. Removal of Organic Compounds Found in the Wastewater through Electrochemical Advanced Oxidation Processes: A Review. RUSS J ELECTROCHEM+ 2019. [DOI: 10.1134/s1023193519050057] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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14
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Antifouling characteristics of a carbon electrode surface hydrogenated by n-butylsilane reduction. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2019.01.188] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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15
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Simultaneous voltammetric detection of 5-hydroxyindole-3-acetic acid and 5-hydroxytryptamine using a glassy carbon electrode modified with conducting polymer and platinised carbon nanofibers. Mikrochim Acta 2018; 185:412. [PMID: 30105543 DOI: 10.1007/s00604-018-2949-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 08/03/2018] [Indexed: 01/07/2023]
Abstract
The authors describe a method for simultaneous voltammetric determination of 5-hydroxytryptamine (serotonin; 5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA). A glassy carbon electrode was modified with poly(pyrrole-3-carboxylic acid) and with platinised carbon nanofibers to obtain a sensor that can quantify 5-HT and 5-HIAA with detection limits of 10 nM and 20 nM, respectively. The peak currents, best measured at voltages of 170 mV and 500 mV (vs. Ag/AgCl) for 5-HT and 5-HIAA, increase linearly in the 0.01-100 μM concentration range for both analytes. The method was successfully applied to the quantitation of 5-HT and 5-HIAA in spiked artificial urine samples, and the sensor can be used up to 10 days. Graphical abstract A new electroanalytical device was developed for separation and quantitation of 5-hydroxytryptamine (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA), based on stripping square wave voltammetry, exploiting conducting polymer surfaces on platinised carbon nanofiber supports.
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16
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A review on electrochemical detection of serotonin based on surface modified electrodes. Biosens Bioelectron 2018; 107:76-93. [DOI: 10.1016/j.bios.2018.02.013] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 02/02/2018] [Accepted: 02/02/2018] [Indexed: 12/22/2022]
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17
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MacEachern SJ, Keenan CM, Papakonstantinou E, Sharkey KA, Patel BA. Alterations in melatonin and 5-HT signalling in the colonic mucosa of mice with dextran-sodium sulfate-induced colitis. Br J Pharmacol 2018; 175:1535-1547. [PMID: 29447434 DOI: 10.1111/bph.14163] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 01/16/2018] [Accepted: 02/03/2018] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND AND PURPOSE Inflammatory bowel disease (IBD) is characterized by pain, bleeding, cramping and altered gastrointestinal (GI) function. Changes in mucosal 5-HT (serotonin) signalling occur in animal models of colitis and in humans suffering from IBD. Melatonin is co-released with 5-HT from the mucosa and has a wide variety of actions in the GI tract. Here, we examined how melatonin signalling is affected by colitis and determined how this relates to 5-HT signalling. EXPERIMENTAL APPROACH Using electroanalytical approaches, we investigated how 5-HT release, reuptake and availability as well as melatonin availability are altered in dextran sodium sulfate (DSS)-induced colitis in mice. Studies were conducted to explore if melatonin treatment during active colitis could reduce the severity of colitis. KEY RESULTS We observed an increase in 5-HT and a decrease in melatonin availability in DSS-induced colitis. A significant reduction in 5-HT reuptake was observed in DSS-induced colitis animals. A reduction in the content of 5-HT was observed, but no difference in tryptophan levels were observed. A reduction in deoxycholic acid-stimulated 5-HT availability and a significant reduction in mechanically-stimulated 5-HT and melatonin availability were observed in DSS-induced colitis. Orally or rectally administered melatonin once colitis was established did not significantly suppress inflammation. CONCLUSION AND IMPLICATIONS Our data suggest that DSS-induced colitis results in a reduction in melatonin availability and an increase in 5-HT availability, due to a reduction/loss of tryptophan hydroxylase 1 enzyme, 5-HT content and 5-HT transporters. Mechanosensory release was more susceptible to inflammation when compared with chemosensory release.
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Affiliation(s)
- Sarah J MacEachern
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada.,Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Catherine M Keenan
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada.,Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada
| | | | - Keith A Sharkey
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada.,Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada
| | - Bhavik Anil Patel
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Huxley Building, Brighton, UK.,Centre for Stress and Age-related Diseases, University of Brighton, Huxley Building, Brighton, UK
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18
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Moon JM, Thapliyal N, Hussain KK, Goyal RN, Shim YB. Conducting polymer-based electrochemical biosensors for neurotransmitters: A review. Biosens Bioelectron 2017; 102:540-552. [PMID: 29220802 DOI: 10.1016/j.bios.2017.11.069] [Citation(s) in RCA: 174] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/25/2017] [Accepted: 11/29/2017] [Indexed: 02/06/2023]
Abstract
Neurotransmitters are important biochemical molecules that control behavioral and physiological functions in central and peripheral nervous system. Therefore, the analysis of neurotransmitters in biological samples has a great clinical and pharmaceutical importance. To date, various methods have been developed for their assay. Of the various methods, the electrochemical sensors demonstrated the potential of being robust, selective, sensitive, and real time measurements. Recently, conducting polymers (CPs) and their composites have been widely employed in the fabrication of various electrochemical sensors for the determination of neurotransmitters. Hence, this review presents a brief introduction to the electrochemical biosensors, with the detailed discussion on recent trends in the development and applications of electrochemical neurotransmitter sensors based on CPs and their composites. The review covers the sensing principle of prime neurotransmitters, including glutamate, aspartate, tyrosine, epinephrine, norepinephrine, dopamine, serotonin, histamine, choline, acetylcholine, nitrogen monoxide, and hydrogen sulfide. In addition, the combination with other analytical techniques was also highlighted. Detection challenges and future prospective of the neurotransmitter sensors were discussed for the development of biomedical and healthcare applications.
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Affiliation(s)
- Jong-Min Moon
- Department of Chemistry and Institute of BioPhysio Sensor Technology (IBST), Pusan National University, Busan 46241, South Korea
| | - Neeta Thapliyal
- Department of Pharmaceutical Chemistry, College of Health Sciences, University of KwaZulu-Natal, Durban 4000, South Africa
| | - Khalil Khadim Hussain
- Department of Chemistry and Institute of BioPhysio Sensor Technology (IBST), Pusan National University, Busan 46241, South Korea
| | - Rajendra N Goyal
- Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667, India.
| | - Yoon-Bo Shim
- Department of Chemistry and Institute of BioPhysio Sensor Technology (IBST), Pusan National University, Busan 46241, South Korea.
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Carabelli V, Marcantoni A, Picollo F, Battiato A, Bernardi E, Pasquarelli A, Olivero P, Carbone E. Planar Diamond-Based Multiarrays to Monitor Neurotransmitter Release and Action Potential Firing: New Perspectives in Cellular Neuroscience. ACS Chem Neurosci 2017; 8:252-264. [PMID: 28027435 DOI: 10.1021/acschemneuro.6b00328] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
High biocompatibility, outstanding electrochemical responsiveness, inertness, and transparency make diamond-based multiarrays (DBMs) first-rate biosensors for in vitro detection of electrochemical and electrical signals from excitable cells together, with potential for in vivo applications as neural interfaces and prostheses. Here, we will review the electrochemical and physical properties of various DBMs and how these devices have been employed for recording released neurotransmitter molecules and all-or-none action potentials from living cells. Specifically, we will overview how DBMs can resolve localized exocytotic events from subcellular compartments using high-density microelectrode arrays (MEAs), or monitoring oxidizable neurotransmitter release from populations of cells in culture and tissue slices using low-density MEAs. Interfacing DBMs with excitable cells is currently leading to the promising opportunity of recording electrical signals as well as creating neuronal interfaces through the same device. Given the recent increasingly growing development of newly available DBMs of various geometries to monitor electrical activity and neurotransmitter release in a variety of excitable and neuronal tissues, the discussion will be limited to planar DBMs.
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Affiliation(s)
- Valentina Carabelli
- Consorzio Nazionale Interuniversitario per le Scienze fisiche della Materia (CNISM), 10125 Torino Unit, Italy
| | - Andrea Marcantoni
- Consorzio Nazionale Interuniversitario per le Scienze fisiche della Materia (CNISM), 10125 Torino Unit, Italy
| | - Federico Picollo
- Consorzio Nazionale Interuniversitario per le Scienze fisiche della Materia (CNISM), 10125 Torino Unit, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), 10125 sez. Torino, Italy
| | - Alfio Battiato
- Consorzio Nazionale Interuniversitario per le Scienze fisiche della Materia (CNISM), 10125 Torino Unit, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), 10125 sez. Torino, Italy
| | - Ettore Bernardi
- Consorzio Nazionale Interuniversitario per le Scienze fisiche della Materia (CNISM), 10125 Torino Unit, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), 10125 sez. Torino, Italy
| | - Alberto Pasquarelli
- Institute
of Electron Devices and Circuits, Ulm University, 89081 Ulm, Germany
| | - Paolo Olivero
- Consorzio Nazionale Interuniversitario per le Scienze fisiche della Materia (CNISM), 10125 Torino Unit, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), 10125 sez. Torino, Italy
| | - Emilio Carbone
- Consorzio Nazionale Interuniversitario per le Scienze fisiche della Materia (CNISM), 10125 Torino Unit, Italy
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20
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Harreither W, Trouillon R, Poulin P, Neri W, Ewing AG, Safina G. Cysteine residues reduce the severity of dopamine electrochemical fouling. Electrochim Acta 2016. [DOI: 10.1016/j.electacta.2016.05.124] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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21
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Patel BA. Mucosal serotonin overflow is associated with colonic stretch rather than phasic contractions. Neurogastroenterol Motil 2016; 28:914-23. [PMID: 26891254 DOI: 10.1111/nmo.12791] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 01/08/2016] [Indexed: 12/22/2022]
Abstract
BACKGROUND Many studies have shown that mucosal serotonin (5-HT) is associated with motility, however, recently there have been some questions to the precise role of this transmitter. The majority of studies have focused on understanding the role of mucosal 5-HT on colonic migratory motor complexes, but very few studies have been carried out to understand how 5-HT release may be associated with other motility patterns. METHODS Using distal colon segments from C57BL/6J mice, mucosal 5-HT overflow was monitored using amperometry while applying tension in longitudinal or circular directions to stretch the tissue. KEY RESULTS Phasic and basal 5-HT levels were not associated with the strength of phasic contractions, while being altered using scopolamine and L-NNA. There was a significant increase in mucosal 5-HT with longitudinal and circular muscle stretch. A greater applied force was needed to activate 5-HT release in the circular muscle. In the longitudinal muscle, 5-HT levels increased with stretch until 3 mN, after which the levels returned back to baseline. This stretch-evoked 5-HT overflow was inhibited by transient receptor potential A1 (TRPA1) agonist, 30 μM ruthenium red in both circular and longitudinal muscle preparations. The decreased 5-HT overflow after 3 mN of tension was reversed using a 5-HT4 antagonist 100 nM GR113808. CONCLUSIONS & INFERENCES Our findings show a relationship between colonic stretch and mucosal 5-HT overflow, while no relationship is observed with phasic colonic contractions. Such findings provide more insight into the role of mucosal 5-HT in influencing the pattern of colonic motility to diversify fecal propulsion.
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Affiliation(s)
- B A Patel
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, UK
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22
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Bennet KE, Tomshine JR, Min HK, Manciu FS, Marsh MP, Paek SB, Settell ML, Nicolai EN, Blaha CD, Kouzani AZ, Chang SY, Lee KH. A Diamond-Based Electrode for Detection of Neurochemicals in the Human Brain. Front Hum Neurosci 2016; 10:102. [PMID: 27014033 PMCID: PMC4791376 DOI: 10.3389/fnhum.2016.00102] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 02/25/2016] [Indexed: 11/13/2022] Open
Abstract
Deep brain stimulation (DBS), a surgical technique to treat certain neurologic and psychiatric conditions, relies on pre-determined stimulation parameters in an open-loop configuration. The major advancement in DBS devices is a closed-loop system that uses neurophysiologic feedback to dynamically adjust stimulation frequency and amplitude. Stimulation-driven neurochemical release can be measured by fast-scan cyclic voltammetry (FSCV), but existing FSCV electrodes rely on carbon fiber, which degrades quickly during use and is therefore unsuitable for chronic neurochemical recording. To address this issue, we developed durable, synthetic boron-doped diamond-based electrodes capable of measuring neurochemical release in humans. Compared to carbon fiber electrodes, they were more than two orders-of-magnitude more physically-robust and demonstrated longevity in vitro without deterioration. Applied for the first time in humans, diamond electrode recordings from thalamic targets in patients (n = 4) undergoing DBS for tremor produced signals consistent with adenosine release at a sensitivity comparable to carbon fiber electrodes. (Clinical trials # NCT01705301).
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Affiliation(s)
- Kevin E Bennet
- Division of Engineering, Mayo ClinicRochester, MN, USA; Neurologic Surgery, Mayo ClinicRochester, MN, USA; School of Engineering, Deakin UniversityMelbourne, VIC, Australia
| | - Jonathan R Tomshine
- Division of Engineering, Mayo ClinicRochester, MN, USA; Neurologic Surgery, Mayo ClinicRochester, MN, USA
| | - Hoon-Ki Min
- Neurologic Surgery, Mayo Clinic Rochester, MN, USA
| | | | | | | | | | | | | | - Abbas Z Kouzani
- School of Engineering, Deakin University Melbourne, VIC, Australia
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23
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Peteu SF, Whitman BW, Galligan JJ, Swain GM. Electrochemical detection of peroxynitrite using hemin-PEDOT functionalized boron-doped diamond microelectrode. Analyst 2016; 141:1796-806. [PMID: 26862713 PMCID: PMC4777311 DOI: 10.1039/c5an02587g] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Peroxynitrite is a potent nitroxidation agent and highly reactive metabolite, clinically correlated with a rich pathophysiology. Its sensitive and selective detection is challenging due to its high reactivity and short sub-second lifetime. Boron-doped diamond (BDD) microelectrodes have attracted interest because of their outstanding electroanalytical properties that include a wide working potential window and enhanced signal-to-noise ratio. Herein, we report on the modification of a BDD microelectrode with an electro-polymerized film of hemin and polyethylenedioxythiophene (PEDOT) for the purpose of selectively quantifying peroxynitrite. The nanostructured modified polymer layer was characterized by Raman spectroscopy and scanning electron microscopy (SEM). The electrochemical response to peroxynitrite was studied by voltammetry and time-based amperometry. The measured detection limit was 10 ± 0.5 nM (S/N = 3), the sensitivity was 4.5 ± 0.5 nA nM(-1) and the response time was 3.5 ± 1 s. The hemin-PEDOT BDD sensors exhibited a response variability of 5% or less (RSD). The stability of the sensors after a 20-day storage in 0.1 M PB (pH 7.4) at 4 °C was excellent as at least 93% of the initial response to 50 nM PON was maintained. The presence of PEDOT was correlated with a sensitivity increase.
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Affiliation(s)
- Serban F Peteu
- Department of Chemistry and the Neuroscience Program, 578 S. Shaw Lane. and Michigan State University, East Lansing, Michigan 48824-1322, USA. and Department of Chemical Engineering and Materials Science, 428 S. Shaw Lane and Michigan State University, East Lansing, Michigan 48824-1226, USA
| | - Brandon W Whitman
- Department of Chemistry and the Neuroscience Program, 578 S. Shaw Lane. and Michigan State University, East Lansing, Michigan 48824-1322, USA.
| | - James J Galligan
- Department of Pharmacology and Toxicology, and the Neuroscience Program, B440 Life Sciences Building and Michigan State University, East Lansing, MI 48824-1317, USA
| | - Greg M Swain
- Department of Chemistry and the Neuroscience Program, 578 S. Shaw Lane. and Michigan State University, East Lansing, Michigan 48824-1322, USA.
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24
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France M, Skorich E, Kadrofske M, Swain GM, Galligan JJ. Sex-related differences in small intestinal transit and serotonin dynamics in high-fat-diet-induced obesity in mice. Exp Physiol 2015; 101:81-99. [PMID: 26381722 DOI: 10.1113/ep085427] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Accepted: 09/15/2015] [Indexed: 12/17/2022]
Abstract
Obesity alters gastrointestinal (GI) motility and 5-HT signalling. Altered 5-HT signalling disrupts control of GI motility. Levels of extracellular 5-HT depend on enterochromaffin (EC) cell release and serotonin transporter (SERT) uptake. We assessed GI transit and 5-HT signalling in the jejunum of normal and obese mice. Male and female mice were fed a control diet (CD; 10% of kilocalories as fat) or a high-fat diet (HFD; 60% of kilocalories as fat). Gastrointestinal transit was increased in male HFD-fed and female CD-fed compared with male CD-fed mice. The 5-HT3 receptor blocker, alosetron, increased gastric emptying in male CD-fed mice, but decreased transit in female CD-fed mice. The 5-HT-induced jejunal longitudinal muscle contractions in vitro were similar in all mice. In contrast to male CD-fed mice, 5-HT uptake (measured using continuous amperometry in vitro) in male HFD-fed mice was fluoxetine insensitive, yet sensitive to cocaine and the dopamine transporter (DAT) blocker GBR 12909. Immunoreactivity for DAT was present in the mucosa, and protein levels were greater in male HFD-fed compared with CD-fed mice. Extracellular 5-HT and mucosal 5-hydroxyindolacetic acid (5-HT metabolite) were similar in male HFD-fed compared with CD-fed mice. 5-Hydroxytryptamine uptake was fluoxetine sensitive in all females. Greater SERT protein, decreased extracellular 5-HT and greater mucosal 5-hydroxyindolacetic acid were observed in female HFD-fed compared with CD-fed mice. Mucosal 5-HT and EC cell numbers were similar in CD-fed and HFD-fed mice of both sexes; female 5-HT and EC cell numbers were increased compared with males. The HFD did not alter plasma sex hormone levels in any mice. Overall, obesity alters GI transit and 5-HT signalling in a sex-dependent manner.
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Affiliation(s)
- Marion France
- Neuroscience Program, Michigan State University, East Lansing, MI, USA
| | - Emmalee Skorich
- Neuroscience Program, Michigan State University, East Lansing, MI, USA
| | - Mark Kadrofske
- Department of Pediatrics and Human Development, Michigan State University, East Lansing, MI, USA
| | - Greg M Swain
- Neuroscience Program, Michigan State University, East Lansing, MI, USA.,Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - James J Galligan
- Neuroscience Program, Michigan State University, East Lansing, MI, USA.,Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI, USA
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25
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Eifert A, Mizaikoff B, Kranz C. Advanced fabrication process for combined atomic force-scanning electrochemical microscopy (AFM-SECM) probes. Micron 2015; 68:27-35. [DOI: 10.1016/j.micron.2014.08.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 08/22/2014] [Accepted: 08/22/2014] [Indexed: 10/24/2022]
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Trouillon R, Einaga Y, Gijs MA. Cathodic pretreatment improves the resistance of boron-doped diamond electrodes to dopamine fouling. Electrochem commun 2014. [DOI: 10.1016/j.elecom.2014.07.028] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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27
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Fagan-Murphy A, Patel BA. Compressed multiwall carbon nanotube composite electrodes provide enhanced electroanalytical performance for determination of serotonin. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2014.06.050] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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28
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Bunyakul N, Promptmas C, Baeumner AJ. Microfluidic biosensor for cholera toxin detection in fecal samples. Anal Bioanal Chem 2014; 407:727-36. [DOI: 10.1007/s00216-014-7947-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2014] [Revised: 05/28/2014] [Accepted: 06/04/2014] [Indexed: 02/05/2023]
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Duran B, Brocenschi RF, France M, Galligan JJ, Swain GM. Electrochemical activation of diamond microelectrodes: implications for the in vitro measurement of serotonin in the bowel. Analyst 2014; 139:3160-6. [PMID: 24802953 PMCID: PMC4266237 DOI: 10.1039/c4an00506f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The electrochemical pretreatment of diamond microelectrodes was investigated for the purpose of learning how an anodic, cathodic or a combined anodic + cathodic polarization affects the charge-transfer kinetics for two surface-sensitive redox systems: ferri/ferrocyanide and serotonin (5-hydroxytryptamine, 5-HT). The pretreatments were performed in 0.5 mol L(-1) H2SO4. The anodic pretreatment was performed galvanically for 30 s at 250 mA cm(-2). The cathodic pretreatment was performed for 180 s at -250 mA cm(-2). The combined pretreatment involved application of the anodic step first followed by the cathodic step. The results clearly demonstrate that the best performance for both redox systems is obtained after the cathodic polarization, which presumably activates the electrode by cleaning the surface and removing site-blocking surface carbon-oxygen functionalities. The cathodic pretreatment was found to be effective at activating a fouled microelectrode in situ. This observation has important implication for the measurement of 5-HT in the bowel.
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Affiliation(s)
- Boris Duran
- Facultad de Química, Departamento de Farmacia, Pontificia Universidad Católica de Chile, C.P. 7820436, Santiago, Chile.
| | - Ricardo F. Brocenschi
- Departamento de Química, Universidade Federal de São 35 Carlos, C.P. 676, 13560-970 São Carlos – SP, Brazil.
| | - Marion France
- Neuroscience Program, Michigan State University, East Lansing, MI 48824-1101
| | - James J. Galligan
- Neuroscience Program, Michigan State University, East Lansing, MI 48824-1101
- Department of Pharmacology and Toxicology, Michigan 40 State University, East Lansing, MI 48824-1317.
| | - Greg M. Swain
- Neuroscience Program, Michigan State University, East Lansing, MI 48824-1101
- Department of Chemistry, Michigan State University, East Lansing, MI USA 48824-1322.
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30
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Eifert A, Langenwalter P, Higl J, Lindén M, Nebel CE, Mizaikoff B, Kranz C. Focused ion beam (FIB)-induced changes in the electrochemical behavior of boron-doped diamond (BDD) electrodes. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2014.03.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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31
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Purinergic autocrine regulation of mechanosensitivity and serotonin release in a human EC model: ATP-gated P2X3 channels in EC are downregulated in ulcerative colitis. Inflamm Bowel Dis 2013; 19:2366-79. [PMID: 23917247 PMCID: PMC4037929 DOI: 10.1097/mib.0b013e31829ecf4d] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Alterations in 5-hydroxytryptamine (HT) signaling in inflamed gut may contribute to pathogenesis of inflammatory bowel diseases. Adenosine 5'-triphosphate (ATP) regulates mucosal-mechanosensory reflexes and ATP receptors are sensitive to mucosal inflammation. Yet, it remains unknown whether ATP can modulate 5-HT signaling in enterochromaffin cells (EC). We tested the novel purinergic hypothesis that ATP is a critical autocrine regulator of EC mechanosensitivity and whether EC expression of ATP-gated P2X3-ion channels is altered in inflammatory bowel diseases. METHODS Laser confocal (fluo-4) Ca imaging was performed in 1947 BON cells. Chemical stimulation or mechanical stimulation (MS) was used to study 5-HT or ATP release in human BON or surgical mucosal specimens, and purine receptors by reverse transcription-polymerase chain reaction, Western Blot, or P2X3-immunoreactivity in BON or 5-HT human EC (hEC) in 11 control and 10 severely inflamed ulcerative colitis (UC) cases. RESULTS ATP or MS triggered Ca-transients or 5-HT release in BON. ATP or adenosine diphosphate increased 5-HT release 5-fold. MS caused ATP release, detected after 5'ecto-ATPase inhibition by ARL67156. ARL67156 augmented and apyrase blocked Ca/5-HT mechanosensitive responses. 2-Methyl-thio-adenosine diphosphate 5'-monophosphate-evoked (P2Y1,12) or mechanically-evoked responses were blocked or augmented by a P2Y1,12 antagonist, MRS2179, in different cells or inhibited by U73122. A P2Y12 antagonist, 2MeSAMP, augmented responses. A P2X1,3 agonist, α,β-MeATP, triggered Ca responses, whereas a P2X1,2/3,3 antagonist, 2',3'-O-(2,4,6-trinitrophenyl)-ATP, blocked mechanical responses or cell-surface 5'ATP- labeling. In hEC, α,β-MeATP stimulated 5-HT release. In UC, P2X3-immunoreactivity decreased from 15% to 0.2% of 5-HThECs. Human mucosa and BON expressed P2X1, P2X3, P2X4, P2X5, P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, and P2Y12R-messenger RNA transcripts. CONCLUSIONS ATP is a critical determinant of mechanosensation and 5-HT release via autocrine activation of slow P2Y1-phospholipase C/inositol-1,4,5-triphosphate-Ca or inhibitory P2Y12-purinergic pathways, and fast ATP-gated P2X3-channels. UC downregulation of P2X3-channels (or A2B) is postulated to mediate abnormal 5-HT signaling.
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Birbeck JA, Mathews TA. Simultaneous Detection of Monoamine and Purine Molecules Using High-Performance Liquid Chromatography with a Boron-Doped Diamond Electrode. Anal Chem 2013; 85:7398-404. [DOI: 10.1021/ac4013144] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Johnna A. Birbeck
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit,
Michigan 48202, United States
| | - Tiffany A. Mathews
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit,
Michigan 48202, United States
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Arumugam PU, Zeng H, Siddiqui S, Covey DP, Carlisle JA, Garris PA. Characterization of ultrananocrystalline diamond microsensors for in vivo dopamine detection. APPLIED PHYSICS LETTERS 2013; 102:253107. [PMID: 23918991 PMCID: PMC3710216 DOI: 10.1063/1.4811785] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Accepted: 06/01/2013] [Indexed: 05/18/2023]
Abstract
We show the technical feasibility of coating and micro patterning boron-doped ultrananocrystalline diamond (UNCD®) on metal microwires and of applying them as microsensors for the detection of dopamine in vivo using fast-scan cyclic voltammetry. UNCD electrode surface consistently generated electrochemical signals with high signal-to-noise ratio of >800 using potassium ferrocyanide-ferricyanide redox couple. Parylene patterned UNCD microelectrodes were effectively applied to detect dopamine reliably in vitro using flow injection analysis with a detection limit of 27 nM and in the striatum of the anesthetized rat during electrical stimulation of dopamine neurons.
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Affiliation(s)
- Prabhu U Arumugam
- Advanced Diamond Technologies, Inc., 48 E Belmont Drive, Romeoville, Illinois 60446, USA
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Patel AN, Unwin PR, Macpherson JV. Investigation of film formation properties during electrochemical oxidation of serotonin (5-HT) at polycrystalline boron doped diamond. Phys Chem Chem Phys 2013; 15:18085-92. [DOI: 10.1039/c3cp53513d] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Parmar L, Fidalgo S, Yeoman MS, Patel BA. Chromatographic analysis of age-related changes in mucosal serotonin transmission in the murine distal ileum. Chem Cent J 2012; 6:31. [PMID: 22494644 PMCID: PMC3483693 DOI: 10.1186/1752-153x-6-31] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 02/27/2012] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND In the upper bowel, alterations in motility and absorption of key nutrients have been observed as part of the normal ageing process. Serotonin (5-HT) is a key signalling molecule in the gastrointestinal tract and is known to influence motility, however little is known of how the ageing process alters 5-HT signalling processes in the bowel. RESULTS An isocratic chromatographic method was able to detect all 5-HT precursors and metabolites. Using extracellular and intracellular sampling approaches, we were able to monitor all key parameters associated with the transmission process. There was no alteration in the levels of tryptophan and 5-HTP between 3 and 18 month old animals. There was a significant increase in the ratio of 5-HT:5-HTP and an increase in intracellular 5-HT between 3 and 18 month old animals suggesting an increase in 5-HT synthesis. There was also a significant increase in extracellular 5-HT with age, suggesting increased 5-HT release. There was an age-related decrease in the ratio of intracellular 5-HIAA:extracellular 5-HT, whilst the amount of 5-HIAA did not change with age. In the presence of an increase in extracellular 5-HT, the lack of an age-related change in 5-HIAA is suggestive of a decrease in re-uptake via the serotonin transporter (SERT). CONCLUSIONS We have used intracellular and extracellular sampling to provide more insight into alterations in the neurotransmission process of 5-HT during normal ageing. We observed elevated 5-HT synthesis and release and a possible decrease in the activity of SERT. Taken together these changes lead to increased 5-HT availability and may alter motility function and could lead to the changes in adsorption observed in the elderly.
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Affiliation(s)
- Leena Parmar
- Centre for Biomedical and Health Sciences Research, University of Brighton, Brighton, BN2 4GJ, UK.
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Patel BA. Electroanalytical approaches to study signaling mechanisms in the gastrointestinal tract. Neurogastroenterol Motil 2011; 23:595-605. [PMID: 21481101 DOI: 10.1111/j.1365-2982.2011.01708.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Electroanalytical techniques over the past few years have been applied to study real-time release of various signaling molecules in the GI tract. These approaches have become highly attractive as they provide dynamic spatial information on the amount of signaling molecules released. Although these approaches are relatively new to the field, the studies to date have provided useful insights into the alterations in signaling mechanisms during maturation, obesity and in a model of colitis. New methods and techniques have also allowed the possibility to obtain information on the signaling process and future developments will provide a wide diverse array of information that will be of benefit to all researchers in the field of gastroenterology. This review focuses on the types of techniques utilized, the information they can provide, their potential advantages and disadvantages in monitoring signaling processes in the gastrointestinal tract, the existing scientific studies that have utilized electroanalytical methods to date and the future potential impact of such approaches.
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Affiliation(s)
- B A Patel
- Centre for Biomedical and Health Sciences Research, University of Brighton, Brighton, UK.
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Abbaspour A, Noori A. A cyclodextrin host-guest recognition approach to an electrochemical sensor for simultaneous quantification of serotonin and dopamine. Biosens Bioelectron 2011; 26:4674-80. [PMID: 21715153 DOI: 10.1016/j.bios.2011.04.061] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 04/22/2011] [Accepted: 04/25/2011] [Indexed: 02/05/2023]
Abstract
An electrochemical sensor for simultaneous quantification of serotonin (5-hydroxytryptamine, 5-HT) and dopamine (DA) using a β-cyclodextrin/poly(N-acetylaniline)/carbon nanotube composite modified carbon paste electrode has been developed. Synergistic effect of multi-walled carbon nanotube (MWCNT) in addition to the pre-concentrating effect of β-cyclodextrin (β-CD) as well as its different inclusion complex stability with 5-HT and DA was used to construct an electrochemical sensor for quantification of these important neurotransmitters. The overlapping anodic peaks of 5-HT and DA at 428 mV on bare electrode resolved in two well-defined voltammetric peaks at 202 and 363 mV vs. Ag/AgCl respectively. The oxidation mechanism of 5-HT and DA on the surface of the electrode was investigated by cyclic voltammetry and it was found that the electrode processes are pH dependent and electrochemical oxidation of 5-HT is totally irreversible while the electrode gave a more reversible process to DA. Under optimized conditions, linear calibration curves were obtained in the range of about 4-200 μM with a detection limits down to sub-μM levels (S/N=3) after 20-s accumulation, for both. The proposed sensor was shown to be remarkably selective for 5-HT and DA in matrices containing different species including ascorbic acid and uric acid. The suitability of the developed method was tested for the determination of 5-HT and DA in the Randox Synthetic Plasma samples and acceptable recoveries were obtained for a set of spiked samples.
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Affiliation(s)
- Abdolkarim Abbaspour
- Chemistry Department, College of Sciences, Shiraz University, Shiraz 7145685464, Iran.
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Zhao H, Sovadinova I, Swope VM, Swain GM, Kadrofske MM, Bian X. Postnatal development of the serotonin signaling system in the mucosa of the guinea pig ileum. Neurogastroenterol Motil 2011; 23:161-8, e40. [PMID: 21226885 PMCID: PMC3071257 DOI: 10.1111/j.1365-2982.2010.01645.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND Serotonin is an important neurohumoral molecule in the gut but its signaling system is not fully developed in the neonatal gastrointestinal (GI) tract. This study aimed to evaluate the postnatal maturation of serotonin signaling in the small intestine. METHODS In vitro amperometry for real-time measurement of serotonin at the mucosal surface, immunoblot, immunohistochemistry and high-performance liquid chromatography (HPLC) were used to examine serotonin handling in ileal segments from guinea pigs of different ages. KEY RESULTS Extracellular serotonin levels significantly declined over the first three postnatal weeks, after which the levels increased and reached their maximum at 9 weeks postnatally. Serotonin levels were insensitive to the inhibition of the serotonin transporter (SERT) until the animals reached 3 weeks old. Measurement of serotonin and its metabolite 5-hydroxyindole acetic acid (5-HIAA) in the mucosa revealed that the serotonin turnover was significantly lower in neonates. Immunoblot and immunohistochemistry showed that SERT expression was extremely low in the neonatal period. Serotonin staining in cross-section showed that enterochromaffin (EC) cells were preferentially localized in the crypt region in neonates and the number of EC cells was significantly higher in 9-week-old animals. CONCLUSIONS & INFERENCES SERT expression is low in the neonatal intestine and serotonin signaling matures postnatally. Extracellular serotonin levels decrease during the first three neonatal weeks as SERT expression increases. Extracellular serotonin levels increase after 3 weeks (weaning) possibly due to an increase in EC cell numbers. Postnatal maturation of serotonin signaling coincides with dietary changes in the developing guinea pig.
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Affiliation(s)
- Hong Zhao
- Department of Chemistry, Michigan State University, East Lansing, MI 48824 USA
| | - Iva Sovadinova
- Department of Pediatrics and Human Development, Michigan State University, East Lansing, MI 48824 USA
| | - Vernon M. Swope
- Department of Chemistry, Michigan State University, East Lansing, MI 48824 USA
| | - Greg M. Swain
- Department of Chemistry, Michigan State University, East Lansing, MI 48824 USA
| | - Mark M. Kadrofske
- Department of Pediatrics and Human Development, Michigan State University, East Lansing, MI 48824 USA
| | - Xiaochun Bian
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI 48824 USA
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Dong H, Wang S, Galligan JJ, Swain GM. Boron-doped diamond nano/microelectrodes for biosensing and in vitro measurements. Front Biosci (Schol Ed) 2011; 3:518-40. [PMID: 21196394 PMCID: PMC4331346 DOI: 10.2741/s169] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Since the fabrication of the first diamond electrode in the mid 1980s, repid progress has been made on the development and application of this new type of electrode material. Boron-doped diamond (BDD) electrodes exhibit outstanding properties compared to oxygen-containing sp2 carbon electrodes. These properties make BDD electrodes an ideal choice for use in complex samples. In recent years, BDD microelectrodes have been applied to in vitro measurements of biological molecules in tissues and cells. This review will summarize recent progress in the development and applications of BDD electrodes in bio-sensing and in vitro measurements of biomolecules. In the first section, the methods for BDD diamond film deposition and BDD microelectrodes preparation are described. This is followed by a description and discussion of several approaches for characterization of the BDD electrode surface structure, morphology, and electrochemical activity. Further, application of BDD microelectrodes for use in the in vitro analysis of norepinephrine (NE), serotonin (5-HT), nitric oxide (NO), histamine, and adenosine from tissues are summarized and finally some of the remaining challenges are discussed.
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Affiliation(s)
- Hua Dong
- Department of Entomology and Cancer Research Center, University of California, Davis, CA 95616, USA.
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Marcelli G, Patel BA. Understanding changes in uptake and release of serotonin from gastrointestinal tissue using a novel electroanalytical approach. Analyst 2010; 135:2340-7. [PMID: 20596571 DOI: 10.1039/c0an00260g] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Serotonin (5-HT) is well known to be a key neurotransmitter within the gastrointestinal (GI) tract, where it is responsible for influencing motility. Obtaining dynamic information about the neurotransmission process (specifically the release and reuptake of 5-HT) requires the development of new approaches to measure the extracellular 5-HT concentration profile. In this work constant-potential amperometry has been utilised at +650 mV vs. Ag|AgCl to measure in vitro the overflow of 5-HT. Steady-state levels of 5-HT have been observed, due to continuous mechanical stimulation of the tissue from the experimental protocol. Measurements are conducted at varying tissue-electrode distances in the range of 5 to 1100 microm. The difference in the current from the bulk media and that from each tissue-electrode distance is obtained, and the natural log of this current is plotted versus the tissue-electrode distance. The linear fit to the log of the current is derived, and its intercept, I(0), with the vertical axis and its slope are calculated. The reciprocal of the slope, indicated as slope(-1), is used as a marker of reuptake. The ratio between intercept, I(0), and the reciprocal of the slope, I(0)/slope(-1), is a measure of the flux at the tissue surface and it can be used as a marker for the 5-HT release rate. Current measurements for ileum and colon tissue indicated a significantly higher reuptake rate in the colon, showed by a lower slope(-1). In addition, the ratio, I(0)/slope(-1), indicated that the colon has a higher 5-HT flux compared to the ileum. Following the application of the serotonin selective reuptake inhibitor (SSRI), fluoxetine, both tissues showed a higher value of slope(-1), as the reuptake process is blocked preventing clearance of 5-HT. No differences were observed in the ratio, I(0)/slope(-1), in the ileum, but a decrease was observed in the colon. These results indicate that ileum and colon are characterised by different reuptake and release processes. The new approach we propose provides pivotal information on the variations in the signalling mechanism, where steady state levels are observed and can be a vital tool to study differences between normal and diseased tissue and also the efficacy of pharmacological agents.
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Affiliation(s)
- Gianluca Marcelli
- Biomedical Engineering Group, Division of Engineering, King's College London, Strand, London, WC2R 2LS, UK
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