Contact
Triad Technology Center333 Cassell Drive
Baltimore, MD 21224
Education
B.S. - Chemistry, Moravian College
Ph.D. - Chemistry, Penn State University
Research Interests
Jacqueline D. Keighron received her B.S. in chemistry (2004) from Moravian College. She then obtained her Ph.D. (2010) in chemistry from Penn State University under the guidance of Dr. Christine Keating focusing on the characterizations of biomolecules, such as enzymes, and nanoparticles as part of a larger effort to create a synthetic cell. After receiving her Ph.D., Jacqueline joined the collaborative laboratories of Dr. Andrew Ewing of the University of Gothenburg and Dr. Ann-Sofie Cans of Chalmers University of Technology in Gothenburg, Sweden. Under the guidance of Dr. Ewing, Jacqueline worked to further our understanding of neurotransmitter storage and release in single cells and the Drosophila nervous system. While with Dr. Cans, she helped develop the first enzyme based electrochemical sensor with sub-second time resolution to detect acetylcholine. Jacqueline joined the Medications Development Program in 2015 as an IRTA Fellow. In the laboratory of Dr. Gianluigi Tanda she is conducting neurochemistry and pharmacology research focused on pre-clinical studies of novel compounds for the treatment of drug abuse disorders and deciphering the effects of psychostimulants on the dopamine reward pathway of the brain.
Publications
Selected Publications
2015
Keighron, Jacqueline D; Wigstrom, Joakim; Kurczy, Michael E; Bergman, Jenny; Wang, Yuanmo; Cans, Ann-Sofie
Amperometric detection of single vesicle acetylcholine release events from an artificial cell. Journal Article
In: ACS Chem Neurosci, vol. 6, no. 1, pp. 181–188, 2015, ISSN: 1948-7193 (Electronic); 1948-7193 (Linking).
@article{Keighron2015,
title = {Amperometric detection of single vesicle acetylcholine release events from an artificial cell.},
author = {Jacqueline D Keighron and Joakim Wigstrom and Michael E Kurczy and Jenny Bergman and Yuanmo Wang and Ann-Sofie Cans},
url = {https://www.ncbi.nlm.nih.gov/pubmed/25565357},
doi = {10.1021/cn5002667},
issn = {1948-7193 (Electronic); 1948-7193 (Linking)},
year = {2015},
date = {2015-01-12},
journal = {ACS Chem Neurosci},
volume = {6},
number = {1},
pages = {181--188},
address = {Department of Chemical and Biological Engineering, Chalmers University of Technology , 41296 Gothenburg, Sweden.},
abstract = {Acetylcholine is a highly abundant nonelectroactive neurotransmitter in the mammalian central nervous system. Neurochemical release occurs on the millisecond time scale, requiring a fast, sensitive sensor such as an enzymatic amperometric electrode. Typically, the enzyme used for enzymatic electrochemical sensors is applied in excess to maximize signal. Here, in addition to sensitivity, we have also sought to maximize temporal resolution, by designing a sensor that is sensitive enough to work at near monolayer enzyme coverage. Reducing the enzyme layer thickness increases sensor temporal resolution by decreasing the distance and reducing the diffusion time for the enzyme product to travel to the sensor surface for detection. In this instance, the sensor consists of electrodeposited gold nanoparticle modified carbon fiber microelectrodes (CFMEs). Enzymes often are sensitive to curvature upon surface adsorption; thus, it was important to deposit discrete nanoparticles to maintain enzyme activity while depositing as much gold as possible to maximize enzyme coverage. To further enhance sensitivity, the enzymes acetylcholinesterase (AChE) and choline oxidase (ChO) were immobilized onto the gold nanoparticles at the previously determined optimal ratio (1:10 AChE/ChO) for most efficient sequential enzymatic activity. This optimization approach has enabled the rapid detection to temporally resolve single vesicle acetylcholine release from an artificial cell. The sensor described is a significant advancement in that it allows for the recording of acetylcholine release on the order of the time scale for neurochemical release in secretory cells.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Acetylcholine is a highly abundant nonelectroactive neurotransmitter in the mammalian central nervous system. Neurochemical release occurs on the millisecond time scale, requiring a fast, sensitive sensor such as an enzymatic amperometric electrode. Typically, the enzyme used for enzymatic electrochemical sensors is applied in excess to maximize signal. Here, in addition to sensitivity, we have also sought to maximize temporal resolution, by designing a sensor that is sensitive enough to work at near monolayer enzyme coverage. Reducing the enzyme layer thickness increases sensor temporal resolution by decreasing the distance and reducing the diffusion time for the enzyme product to travel to the sensor surface for detection. In this instance, the sensor consists of electrodeposited gold nanoparticle modified carbon fiber microelectrodes (CFMEs). Enzymes often are sensitive to curvature upon surface adsorption; thus, it was important to deposit discrete nanoparticles to maintain enzyme activity while depositing as much gold as possible to maximize enzyme coverage. To further enhance sensitivity, the enzymes acetylcholinesterase (AChE) and choline oxidase (ChO) were immobilized onto the gold nanoparticles at the previously determined optimal ratio (1:10 AChE/ChO) for most efficient sequential enzymatic activity. This optimization approach has enabled the rapid detection to temporally resolve single vesicle acetylcholine release from an artificial cell. The sensor described is a significant advancement in that it allows for the recording of acetylcholine release on the order of the time scale for neurochemical release in secretory cells.
2014
Keighron, Jacqueline D; Akesson, Sebastian; Cans, Ann-Sofie
Coimmobilization of acetylcholinesterase and choline oxidase on gold nanoparticles: stoichiometry, activity, and reaction efficiency. Journal Article
In: Langmuir, vol. 30, no. 38, pp. 11348–11355, 2014, ISSN: 1520-5827 (Electronic); 0743-7463 (Linking).
@article{Keighron2014,
title = {Coimmobilization of acetylcholinesterase and choline oxidase on gold nanoparticles: stoichiometry, activity, and reaction efficiency.},
author = {Jacqueline D Keighron and Sebastian Akesson and Ann-Sofie Cans},
url = {https://www.ncbi.nlm.nih.gov/pubmed/25167196},
doi = {10.1021/la502538h},
issn = {1520-5827 (Electronic); 0743-7463 (Linking)},
year = {2014},
date = {2014-09-22},
journal = {Langmuir},
volume = {30},
number = {38},
pages = {11348--11355},
address = {Department of Chemical and Biological Engineering, Chalmers University of Technology , Gothenburg 41319, Sweden.},
abstract = {Hybrid structures constructed from biomolecules and nanomaterials have been used in catalysis and bioanalytical applications. In the design of many chemically selective biosensors, enzymes conjugated to nanoparticles or carbon nanotubes have been used in functionalization of the sensor surface for enhancement of the biosensor functionality and sensitivity. The conditions for the enzyme:nanomaterial conjugation should be optimized to retain maximal enzyme activity, and biosensor effectiveness. This is important as the tertiary structure of the enzyme is often altered when immobilized and can significantly alter the enzyme catalytic activity. Here we show that characterization of a two-enzyme:gold nanoparticle (AuNP) conjugate stoichiometry and activity can be used to gauge the effectiveness of acetylcholine detection by acetylcholine esterase (AChE) and choline oxidase (ChO). This was done by using an analytical approach to quantify the number of enzymes bound per AuNP and monitor the retained enzyme activity after the enzyme:AuNP synthesis. We found that the amount of immobilized enzymes differs from what would be expected from bulk solution chemistry. This analysis was further used to determine the optimal ratio of AChE:ChO added at synthesis to achieve optimum sequential enzyme activity for the enzyme:AuNP conjugates, and reaction efficiencies of greater than 70%. We here show that the knowledge of the conjugate stoichiometry and retained enzyme activity can lead to more efficient detection of acetylcholine by controlling the AChE:ChO ratio bound to the gold nanoparticle material. This approach of optimizing enzyme gold nanoparticle conjugates should be of great importance in the architecture of enzyme nanoparticle based biosensors to retain optimal sensor sensitivity.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hybrid structures constructed from biomolecules and nanomaterials have been used in catalysis and bioanalytical applications. In the design of many chemically selective biosensors, enzymes conjugated to nanoparticles or carbon nanotubes have been used in functionalization of the sensor surface for enhancement of the biosensor functionality and sensitivity. The conditions for the enzyme:nanomaterial conjugation should be optimized to retain maximal enzyme activity, and biosensor effectiveness. This is important as the tertiary structure of the enzyme is often altered when immobilized and can significantly alter the enzyme catalytic activity. Here we show that characterization of a two-enzyme:gold nanoparticle (AuNP) conjugate stoichiometry and activity can be used to gauge the effectiveness of acetylcholine detection by acetylcholine esterase (AChE) and choline oxidase (ChO). This was done by using an analytical approach to quantify the number of enzymes bound per AuNP and monitor the retained enzyme activity after the enzyme:AuNP synthesis. We found that the amount of immobilized enzymes differs from what would be expected from bulk solution chemistry. This analysis was further used to determine the optimal ratio of AChE:ChO added at synthesis to achieve optimum sequential enzyme activity for the enzyme:AuNP conjugates, and reaction efficiencies of greater than 70%. We here show that the knowledge of the conjugate stoichiometry and retained enzyme activity can lead to more efficient detection of acetylcholine by controlling the AChE:ChO ratio bound to the gold nanoparticle material. This approach of optimizing enzyme gold nanoparticle conjugates should be of great importance in the architecture of enzyme nanoparticle based biosensors to retain optimal sensor sensitivity.
2013
Trouillon, Raphael; Lin, Yuqing; Mellander, Lisa J; Keighron, Jacqueline D; Ewing, Andrew G
Evaluating the diffusion coefficient of dopamine at the cell surface during amperometric detection: disk vs ring microelectrodes. Journal Article
In: Anal Chem, vol. 85, no. 13, pp. 6421–6428, 2013, ISSN: 1520-6882 (Electronic); 0003-2700 (Linking).
@article{Trouillon2013,
title = {Evaluating the diffusion coefficient of dopamine at the cell surface during amperometric detection: disk vs ring microelectrodes.},
author = {Raphael Trouillon and Yuqing Lin and Lisa J Mellander and Jacqueline D Keighron and Andrew G Ewing},
url = {https://www.ncbi.nlm.nih.gov/pubmed/23706095},
doi = {10.1021/ac400965d},
issn = {1520-6882 (Electronic); 0003-2700 (Linking)},
year = {2013},
date = {2013-06-12},
journal = {Anal Chem},
volume = {85},
number = {13},
pages = {6421--6428},
address = {Department of Chemistry and Molecular Biology, University of Gothenburg, S-41296, Gothenburg, Sweden.},
abstract = {During exocytosis, small quantities of neurotransmitters are released by the cell. These neurotransmitters can be detected quantitatively using electrochemical methods, principally with disk carbon fiber microelectrode amperometry. An exocytotic event then results in the recording of a current peak whose characteristic features are directly related to the mechanisms of exocytosis. We have compared two exocytotic peak populations obtained from PC12 cells with a disk carbon fiber microelectrode and with a pyrolyzed carbon ring microelectrode array, with a 500 nm ring thickness. The specific shape of the ring electrode allows for precise analysis of diffusion processes at the vicinity of the cell membrane. Peaks obtained with a ring microelectrode array show a distorted average shape, owing to increased diffusion pathways. This result has been used to evaluate the diffusion coefficient of dopamine at the surface of a cell, which is up to an order of magnitude smaller than that measured in free buffer. The lower rate of diffusion is discussed as resulting from interactions with the glycocalyx.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
During exocytosis, small quantities of neurotransmitters are released by the cell. These neurotransmitters can be detected quantitatively using electrochemical methods, principally with disk carbon fiber microelectrode amperometry. An exocytotic event then results in the recording of a current peak whose characteristic features are directly related to the mechanisms of exocytosis. We have compared two exocytotic peak populations obtained from PC12 cells with a disk carbon fiber microelectrode and with a pyrolyzed carbon ring microelectrode array, with a 500 nm ring thickness. The specific shape of the ring electrode allows for precise analysis of diffusion processes at the vicinity of the cell membrane. Peaks obtained with a ring microelectrode array show a distorted average shape, owing to increased diffusion pathways. This result has been used to evaluate the diffusion coefficient of dopamine at the surface of a cell, which is up to an order of magnitude smaller than that measured in free buffer. The lower rate of diffusion is discussed as resulting from interactions with the glycocalyx.
Berglund, Carina E; Makos, Monique A; Keighron, Jacqueline D; Phan, Nhu; Heien, Michael L; Ewing, Andrew G
Oral administration of methylphenidate blocks the effect of cocaine on uptake at the Drosophila dopamine transporter. Journal Article
In: ACS Chem Neurosci, vol. 4, no. 4, pp. 566–574, 2013, ISSN: 1948-7193 (Electronic); 1948-7193 (Linking).
@article{Berglund2013,
title = {Oral administration of methylphenidate blocks the effect of cocaine on uptake at the Drosophila dopamine transporter.},
author = {Carina E Berglund and Monique A Makos and Jacqueline D Keighron and Nhu Phan and Michael L Heien and Andrew G Ewing},
url = {https://www.ncbi.nlm.nih.gov/pubmed/23402315},
doi = {10.1021/cn3002009},
issn = {1948-7193 (Electronic); 1948-7193 (Linking)},
year = {2013},
date = {2013-02-25},
journal = {ACS Chem Neurosci},
volume = {4},
number = {4},
pages = {566--574},
address = {Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivagen 10, SE-412 96, Goteborg, Sweden.},
abstract = {Although our understanding of the actions of cocaine in the brain has improved, an effective drug treatment for cocaine addiction has yet to be found. Methylphenidate binds the dopamine transporter and increases extracellular dopamine levels in mammalian central nervous systems similar to cocaine, but it is thought to elicit fewer addictive and reinforcing effects owing to slower pharmacokinetics for different routes of administration between the drugs. This study utilizes the fruit fly model system to quantify the effects of oral methylphenidate on dopamine uptake during direct cocaine exposure to the fly CNS. The effect of methylphenidate on the dopamine transporter has been explored by measuring the uptake of exogenously applied dopamine. The data suggest that oral consumption of methylphenidate inhibits the Drosophila dopamine transporter and the inhibition is concentration dependent. The peak height increased to 150% of control when cocaine was used to block the dopamine transporter for untreated flies but only to 110% for methylphenidate-treated flies. Thus, the dopamine transporter is mostly inhibited for the methylphenidate-fed flies before the addition of cocaine. The same is true for the rate of the clearance of dopamine measured by amperometry. For untreated flies the rate of clearance changes 40% when the dopamine transporter is inhibited with cocaine, and for treated flies the rate changes only 10%. The results were correlated to the in vivo concentration of methylphenidate determined by CE-MS. Our data suggest that oral consumption of methylphenidate inhibits the Drosophila dopamine transporter for cocaine uptake, and the inhibition is concentration dependent.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Although our understanding of the actions of cocaine in the brain has improved, an effective drug treatment for cocaine addiction has yet to be found. Methylphenidate binds the dopamine transporter and increases extracellular dopamine levels in mammalian central nervous systems similar to cocaine, but it is thought to elicit fewer addictive and reinforcing effects owing to slower pharmacokinetics for different routes of administration between the drugs. This study utilizes the fruit fly model system to quantify the effects of oral methylphenidate on dopamine uptake during direct cocaine exposure to the fly CNS. The effect of methylphenidate on the dopamine transporter has been explored by measuring the uptake of exogenously applied dopamine. The data suggest that oral consumption of methylphenidate inhibits the Drosophila dopamine transporter and the inhibition is concentration dependent. The peak height increased to 150% of control when cocaine was used to block the dopamine transporter for untreated flies but only to 110% for methylphenidate-treated flies. Thus, the dopamine transporter is mostly inhibited for the methylphenidate-fed flies before the addition of cocaine. The same is true for the rate of the clearance of dopamine measured by amperometry. For untreated flies the rate of clearance changes 40% when the dopamine transporter is inhibited with cocaine, and for treated flies the rate changes only 10%. The results were correlated to the in vivo concentration of methylphenidate determined by CE-MS. Our data suggest that oral consumption of methylphenidate inhibits the Drosophila dopamine transporter for cocaine uptake, and the inhibition is concentration dependent.
2012
Lin, Yuqing; Trouillon, Raphael; Svensson, Maria I; Keighron, Jacqueline D; Cans, Ann-Sofie; Ewing, Andrew G
Carbon-ring microelectrode arrays for electrochemical imaging of single cell exocytosis: fabrication and characterization. Journal Article
In: Anal Chem, vol. 84, no. 6, pp. 2949–2954, 2012, ISSN: 1520-6882 (Electronic); 0003-2700 (Linking).
@article{Lin2012,
title = {Carbon-ring microelectrode arrays for electrochemical imaging of single cell exocytosis: fabrication and characterization.},
author = {Yuqing Lin and Raphael Trouillon and Maria I Svensson and Jacqueline D Keighron and Ann-Sofie Cans and Andrew G Ewing},
url = {https://www.ncbi.nlm.nih.gov/pubmed/22339586},
doi = {10.1021/ac3000368},
issn = {1520-6882 (Electronic); 0003-2700 (Linking)},
year = {2012},
date = {2012-03-06},
journal = {Anal Chem},
volume = {84},
number = {6},
pages = {2949--2954},
address = {Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.},
abstract = {Fabrication of carbon microelectrode arrays, with up to 15 electrodes in total tips as small as 10-50 mum, is presented. The support structures of microelectrodes were obtained by pulling multiple quartz capillaries together to form hollow capillary arrays before carbon deposition. Carbon ring microelectrodes were deposited by pyrolysis of acetylene in the lumen of these quartz capillary arrays. Each carbon deposited array tip was filled with epoxy, followed by beveling of the tip of the array to form a deposited carbon-ring microelectrode array (CRMA). Both the number of the microelectrodes in the array and the tip size are independently tunable. These CRMAs have been characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, and electrogenerated chemiluminescence. Additionally, the electrochemical properties were investigated with steady-state voltammetry. In order to demonstrate the utility of these fabricated microelectrodes in neurochemistry, CRMAs containing eight microring electrodes were used for electrochemical monitoring of exocytotic events from single PC12 cells. Subcellular temporal heterogeneities in exocytosis (i.e. cold spots vs hot spots) were successfully detected with the CRMAs.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Fabrication of carbon microelectrode arrays, with up to 15 electrodes in total tips as small as 10-50 mum, is presented. The support structures of microelectrodes were obtained by pulling multiple quartz capillaries together to form hollow capillary arrays before carbon deposition. Carbon ring microelectrodes were deposited by pyrolysis of acetylene in the lumen of these quartz capillary arrays. Each carbon deposited array tip was filled with epoxy, followed by beveling of the tip of the array to form a deposited carbon-ring microelectrode array (CRMA). Both the number of the microelectrodes in the array and the tip size are independently tunable. These CRMAs have been characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, and electrogenerated chemiluminescence. Additionally, the electrochemical properties were investigated with steady-state voltammetry. In order to demonstrate the utility of these fabricated microelectrodes in neurochemistry, CRMAs containing eight microring electrodes were used for electrochemical monitoring of exocytotic events from single PC12 cells. Subcellular temporal heterogeneities in exocytosis (i.e. cold spots vs hot spots) were successfully detected with the CRMAs.
2010
Keighron, Jacqueline D; Keating, Christine D
In: Langmuir, vol. 26, no. 24, pp. 18992–19000, 2010, ISSN: 1520-5827 (Electronic); 0743-7463 (Linking).
@article{Keighron2010,
title = {Enzyme:nanoparticle bioconjugates with two sequential enzymes: stoichiometry and activity of malate dehydrogenase and citrate synthase on Au nanoparticles.},
author = {Jacqueline D Keighron and Christine D Keating},
url = {https://www.ncbi.nlm.nih.gov/pubmed/21114258},
doi = {10.1021/la1040882},
issn = {1520-5827 (Electronic); 0743-7463 (Linking)},
year = {2010},
date = {2010-11-29},
journal = {Langmuir},
volume = {26},
number = {24},
pages = {18992--19000},
address = {Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.},
abstract = {We report the synthesis and characterization of bioconjugates in which the enzymes malate dehydrogenase (MDH) and/or citrate synthase (CS) were adsorbed to 30 nm diameter Au nanoparticles. Enzyme:Au stoichiometry and kinetic parameters (specific activity, k(cat), K(M), and activity per particle) were determined for MDH:Au, CS:Au, and three types of dual-activity MDH/CS:Au bioconjugates. For single-activity bioconjugates (MDH:Au and CS:Au), the number of enzyme molecules adsorbed per particle was dependent upon the enzyme concentration in solution, with multilayers forming at high enzyme:Au solution ratios. The specific activity of adsorbed enzyme increased with increasing number adsorbed per particle for CS:Au, but was less sensitive to stoichiometry for MDH:Au. Dual activity bioconjugates were prepared in three ways: (1) by adsorption of MDH followed by CS, (2) by adsorption of CS followed by MDH, and (3) by coadsorption of both enzymes from the same solution. The resulting bioconjugates differed substantially in the number of enzyme molecules adsorbed per particle, the specific activity of the adsorbed enzymes, and also the enzymatic activity per particle. Bioconjugates formed by adding CS to the Au nanoparticles before MDH was added exhibited higher specific activities for both enzymes than those formed by adding the enzymes in the reverse order. These bioconjugates also had 3-fold higher per-particle sequential activity for conversion of malate to citrate, despite substantially fewer copies of both enzymes present.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report the synthesis and characterization of bioconjugates in which the enzymes malate dehydrogenase (MDH) and/or citrate synthase (CS) were adsorbed to 30 nm diameter Au nanoparticles. Enzyme:Au stoichiometry and kinetic parameters (specific activity, k(cat), K(M), and activity per particle) were determined for MDH:Au, CS:Au, and three types of dual-activity MDH/CS:Au bioconjugates. For single-activity bioconjugates (MDH:Au and CS:Au), the number of enzyme molecules adsorbed per particle was dependent upon the enzyme concentration in solution, with multilayers forming at high enzyme:Au solution ratios. The specific activity of adsorbed enzyme increased with increasing number adsorbed per particle for CS:Au, but was less sensitive to stoichiometry for MDH:Au. Dual activity bioconjugates were prepared in three ways: (1) by adsorption of MDH followed by CS, (2) by adsorption of CS followed by MDH, and (3) by coadsorption of both enzymes from the same solution. The resulting bioconjugates differed substantially in the number of enzyme molecules adsorbed per particle, the specific activity of the adsorbed enzymes, and also the enzymatic activity per particle. Bioconjugates formed by adding CS to the Au nanoparticles before MDH was added exhibited higher specific activities for both enzymes than those formed by adding the enzymes in the reverse order. These bioconjugates also had 3-fold higher per-particle sequential activity for conversion of malate to citrate, despite substantially fewer copies of both enzymes present.
