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Salavatian S, Robbins EM, Kuwabara Y, Castagnola E, Cui XT, Mahajan A. Real-time in vivo thoracic spinal glutamate sensing during myocardial ischemia. Am J Physiol Heart Circ Physiol 2023; 325:H1304-H1317. [PMID: 37737733 PMCID: PMC10908408 DOI: 10.1152/ajpheart.00299.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 09/18/2023] [Accepted: 09/18/2023] [Indexed: 09/23/2023]
Abstract
In the spinal cord, glutamate serves as the primary excitatory neurotransmitter. Monitoring spinal glutamate concentrations offers valuable insights into spinal neural processing. Consequently, spinal glutamate concentration has the potential to emerge as a useful biomarker for conditions characterized by increased spinal neural network activity, especially when uptake systems become dysfunctional. In this study, we developed a multichannel custom-made flexible glutamate-sensing probe for the large-animal model that is capable of measuring extracellular glutamate concentrations in real time and in vivo. We assessed the probe's sensitivity and specificity through in vitro and ex vivo experiments. Remarkably, this developed probe demonstrates nearly instantaneous glutamate detection and allows continuous monitoring of glutamate concentrations. Furthermore, we evaluated the mechanical and sensing performance of the probe in vivo, within the pig spinal cord. Moreover, we applied the glutamate-sensing method using the flexible probe in the context of myocardial ischemia-reperfusion (I/R) injury. During I/R injury, cardiac sensory neurons in the dorsal root ganglion transmit excitatory signals to the spinal cord, resulting in sympathetic activation that potentially leads to fatal arrhythmias. We have successfully shown that our developed glutamate-sensing method can detect this spinal network excitation during myocardial ischemia. This study illustrates a novel technique for measuring spinal glutamate at different spinal cord levels as a surrogate for the spinal neural network activity during cardiac interventions that engage the cardio-spinal neural pathway.NEW & NOTEWORTHY In this study, we have developed a new flexible sensing probe to perform an in vivo measurement of spinal glutamate signaling in a large animal model. Our initial investigations involved precise testing of this probe in both in vitro and ex vivo environments. We accurately assessed the sensitivity and specificity of our glutamate-sensing probe and demonstrated its performance. We also evaluated the performance of our developed flexible probe during the insertion and compared it with the stiff probe during animal movement. Subsequently, we used this innovative technique to monitor the spinal glutamate signaling during myocardial ischemia and reperfusion that can cause fatal ventricular arrhythmias. We showed that glutamate concentration increases during the myocardial ischemia, persists during the reperfusion, and is associated with sympathoexcitation and increases in myocardial substrate excitability.
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Affiliation(s)
- Siamak Salavatian
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Division of Cardiology, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Elaine Marie Robbins
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Yuki Kuwabara
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Elisa Castagnola
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Xinyan Tracy Cui
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Center for Neural Basis of Cognition, Pittsburgh, Pennsylvania, United States
- McGowan Institute for Regenerative Medicine, Pittsburgh, Pennsylvania, United States
| | - Aman Mahajan
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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Kim YH, Koo H, Kim MS, Jung SD. Fabrication of a photo-crosslinkable fluoropolymer-passivated flexible neural probe and acute recording and stimulation performances in vivo. BIOMATERIALS ADVANCES 2023; 154:213629. [PMID: 37742557 DOI: 10.1016/j.bioadv.2023.213629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 08/25/2023] [Accepted: 09/16/2023] [Indexed: 09/26/2023]
Abstract
Herein, we fabricated fluorine-containing, polymer-based, flexible neural probes with fluorinated ethylene propylene (FEP) films as the substrates and photo-crosslinkable fluoropolymers as the passivation material. For fabrication, metal-free Au layer formation on the FEP film, the simultaneous photo-adhesion and photo-patterning technique, and the pulsed-laser scanning probe shaping technique were combined, followed by Au electrode surface modification. The resultant probes achieved a charge injection limit equal to 5.18 mC cm-2 by implementing iridium oxide-modified nanoporous Au (IrOx/NPG) structures. We performed simultaneous in vivo micro-stimulations of the Schaffer collateral fibres and recorded the evoked field excitatory postsynaptic potentials (fEPSPs) in the stratum radiatum layer of the hippocampal Cornu Ammonis 1 region using a single probe. Inducing the fEPSP at very low charge per pulse settings (3.2-3.6 nC/pulse) indicates the efficient charge injection capability of the IrOx/NPG electrode, thereby enabling safe, prolonged, and thrifty micro-stimulations. Furthermore, the single probe-induced and recorded long-term potentiation persisted for periods longer than 60 min following theta-burst stimulation. The materials used in this study are all biocompatible and chemically robust. The fabricated neural probes can be applied in chronic clinical trials in vivo.
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Affiliation(s)
- Yong Hee Kim
- Cybre Brain Research Section, Electronics and Telecommunications Research Institute, 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700, Republic of Korea
| | - Ho Koo
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Min Sun Kim
- Department of Physiology, Wonkwang University School of Medicine, 895 Munwang-ro, Iksan 570-711, Jeollabuk-do, Republic of Korea
| | - Sang-Don Jung
- Cybre Brain Research Section, Electronics and Telecommunications Research Institute, 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700, Republic of Korea.
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Salavatian S, Robbins EM, Kuwabara Y, Castagnola E, Cui XT, Mahajan A. Real-time in vivo thoracic spinal glutamate sensing reveals spinal hyperactivity during myocardial ischemia. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.11.531911. [PMID: 36993301 PMCID: PMC10054946 DOI: 10.1101/2023.03.11.531911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Myocardial ischemia-reperfusion (IR) can cause ventricular arrhythmias and sudden cardiac death via sympathoexcitation. The spinal cord neural network is crucial in triggering these arrhythmias and evaluating its neurotransmitter activity during IR is critical for understanding ventricular excitability control. To assess the real-time in vivo spinal neural activity in a large animal model, we developed a flexible glutamate-sensing multielectrode array. To record the glutamate signaling during IR injury, we inserted the probe into the dorsal horn of the thoracic spinal cord at the T2-T3 where neural signals generated by the cardiac sensory neurons are processed and provide sympathoexcitatory feedback to the heart. Using the glutamate sensing probe, we found that the spinal neural network was excited during IR, especially after 15 mins, and remained elevated during reperfusion. Higher glutamate signaling was correlated with the reduction in the cardiac myocyte activation recovery interval, showing higher sympathoexcitation, as well as dispersion of the repolarization which is a marker for increased risk of arrhythmias. This study illustrates a new technique for measuring the spinal glutamate at different spinal cord levels as a surrogate for the spinal neural network activity during cardiac interventions that engage the cardio-spinal neural pathway. Graphical abstract
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Pence M, Rodríguez O, Lukhanin NG, Schroeder CM, Rodríguez-López J. Automated Measurement of Electrogenerated Redox Species Degradation Using Multiplexed Interdigitated Electrode Arrays. ACS MEASUREMENT SCIENCE AU 2023; 3:62-72. [PMID: 36817007 PMCID: PMC9936799 DOI: 10.1021/acsmeasuresciau.2c00054] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/14/2022] [Accepted: 10/18/2022] [Indexed: 06/18/2023]
Abstract
Characterizing the decomposition of electrogenerated species in solution is essential for applications involving electrosynthesis, homogeneous electrocatalysis, and energy storage with redox flow batteries. In this work, we present an automated, multiplexed, and highly robust platform for determining the rate constant of chemical reaction steps following electron transfer, known as the EC mechanism. We developed a generation-collection methodology based on microfabricated interdigitated electrode arrays (IDAs) with variable gap widths on a single device. Using a combination of finite-element simulations and statistical analysis of experimental data, our results show that the natural logarithm of collection efficiency is linear with respect to gap width, and this quantitative analysis is used to determine the decomposition rate constant of the electrogenerated species (k c). The integrated IDA method is used in a series of experiments to measure k c values between ∼0.01 and 100 s-1 in aqueous and nonaqueous solvents and at concentrations as high as 0.5 M of the redox-active species, conditions that are challenging to address using standard methods based on conventional macroelectrodes. The versatility of our approach allows for characterization of a wide range of reactions including intermolecular cyclization, hydrolysis, and the decomposition of candidate molecules for redox flow batteries at variable concentration and water content. Overall, this new experimental platform presents a straightforward automated method to assess the degradation of redox species in solution with sufficient flexibility to enable high-throughput workflows.
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Affiliation(s)
- Michael
A. Pence
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois61801, United States
- Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana—Champaign, Urbana, Illinois61801, United States
- Joint
Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois60439, United States
| | - Oliver Rodríguez
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois61801, United States
- Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana—Champaign, Urbana, Illinois61801, United States
- Joint
Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois60439, United States
| | - Nikita G. Lukhanin
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois61801, United States
- Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana—Champaign, Urbana, Illinois61801, United States
- Joint
Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois60439, United States
| | - Charles M. Schroeder
- Department
of Chemical and Biomolecular Engineering, University of Illinois at Urbana—Champaign, Urbana, Illinois61801, United States
- Department
of Materials Science and Engineering, University
of Illinois at Urbana—Champaign, Urbana, Illinois61801, United States
- Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana—Champaign, Urbana, Illinois61801, United States
- Joint
Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois60439, United States
| | - Joaquín Rodríguez-López
- Department
of Chemistry, University of Illinois at
Urbana—Champaign, Urbana, Illinois61801, United States
- Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana—Champaign, Urbana, Illinois61801, United States
- Joint
Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois60439, United States
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Fabrication of Planar Microelectrode Array Using Laser-Patterned ITO and SU-8. MICROMACHINES 2021; 12:mi12111347. [PMID: 34832760 PMCID: PMC8621540 DOI: 10.3390/mi12111347] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 10/27/2021] [Accepted: 10/28/2021] [Indexed: 01/09/2023]
Abstract
For several decades, microelectrode array (MEA) has been a powerful tool for in vitro neural electrophysiology because it provides a unique approach for monitoring the activity of a number of neurons over time. Due to the various applications of MEAs with different types of cells and tissues, there is an increasing need to customize the electrode designs. However, the fabrication of conventional MEAs requires several microfabrication procedures of deposition, etching, and photolithography. In this study, we proposed a simple fabrication method with a laser-patterned indium tin oxide (ITO) conductor and SU-8 photoresist insulation. Unlike in a conventional metal patterning process, only the outlines of ITO conductors are ablated by laser without removing background ITO. Insulation is achieved simply via SU-8 photolithography. The electrode sites are electroplated with iridium oxide (IrOX) to improve the electrochemical properties. The fabricated MEAs are electrochemically characterized and the stability of insulation is also confirmed by impedance monitoring for three weeks. Dissociated neurons of rat hippocampi are cultured on MEAs to verify the biocompatibility and the capacity for extracellular neural recording. The electrochemical and electrophysiological results with the fabricated MEAs are similar to those from conventional SiNX-insulated MEAs. Therefore, the proposed MEA with laser-patterned ITO and SU-8 is cost-effective and equivalently feasible compared with the conventional MEAs fabricated using thin-film microfabrication techniques.
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Biocompatibility of SU-8 and Its Biomedical Device Applications. MICROMACHINES 2021; 12:mi12070794. [PMID: 34357204 PMCID: PMC8304786 DOI: 10.3390/mi12070794] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 07/01/2021] [Accepted: 07/02/2021] [Indexed: 11/16/2022]
Abstract
SU-8 is an epoxy-based, negative-tone photoresist that has been extensively utilized to fabricate myriads of devices including biomedical devices in the recent years. This paper first reviews the biocompatibility of SU-8 for in vitro and in vivo applications. Surface modification techniques as well as various biomedical applications based on SU-8 are also discussed. Although SU-8 might not be completely biocompatible, existing surface modification techniques, such as O2 plasma treatment or grafting of biocompatible polymers, might be sufficient to minimize biofouling caused by SU-8. As a result, a great deal of effort has been directed to the development of SU-8-based functional devices for biomedical applications. This review includes biomedical applications such as platforms for cell culture and cell encapsulation, immunosensing, neural probes, and implantable pressure sensors. Proper treatments of SU-8 and slight modification of surfaces have enabled the SU-8 as one of the unique choices of materials in the fabrication of biomedical devices. Due to the versatility of SU-8 and comparative advantages in terms of improved Young’s modulus and yield strength, we believe that SU-8-based biomedical devices would gain wider proliferation among the biomedical community in the future.
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