Development of Microelectrochemical Methods for ... tello_presentati… · Miguel Abrego Tello,...

Development of Microelectrochemical Methods for Differentiation of the Catecholamine Neurotransmitters

October 4, 2018

Miguel Abrego, Mengjia Hu, Mahsa Lotfi-Marchoubeh, and Ingrid Fritsch

Department of Chemistry and Biochemistry

University of Arkansas

OUTLINE

▪ Catecholamines as neurotransmitters

▪ CA Mechanism Reaction

▪ Modeling framework

▪ Application of electrochemical redox cycling towards the differentiation of neurotransmitters.

▪ Physics description

▪ Redox cycling of the catecholamines

▪ Results

▪ Conclusions

▪ References

2Miguel Abrego Tello, Ingrid Fritsch, University of Arkansas, 10/04/2018

Catecholamines as Neurotransmitters

▪ Importance:

– Related to neurological disorders including Parkinson’s disease, Huntington’s disease, Tourette’s syndrome and schizophrenia.

▪ Detection

– Desired features:

▪ High spatial and temporal resolution

▪ Minimal tissue damage

– Electroactive

▪ Electrochemical detection

– Similar structure

▪ Difficult to differentiate


Probe

mm scale

CA Mechanism Reaction

4

kf (s-1) at pH=7.4

DA 0.13±0.05

NE 0.98±0.52

C

-2H+-2e-

+2H++2e-Catecholamine

(CA)O-quinone

(OQ)E

kfb

kbb

Fast

Catecholamine

(CA)

Aminochrome

(AC)

kf

Leucoaminochrome

(LAC)

C’Leucoaminochrome

(LAC)

+

O-quinone

(OQ)

O-quinone

(OQ)

+

1 4 2 1 8 2 7

2131 bb fb bb fbkk C C k C

tC C

CD C k C C C

Miguel Abrego Tello, Ingrid Fritsch, University of Arkansas, 10/04/2018

Modeling Framework

5

Initial Conditions:

*( , ,0) 0.01

( , ,0) 0

( , ,0) 0

( , ,0) 0

CA CA

OQ

LAC

AC

C x y C m

C x y

C x y

C x y

1 4 2 3

1 4 2 3

1 4 2 3

1 4 2

211

222

233

244

5

1 8 2 7

1 8 2 7

5 4 6 3

5 4 6 33

2 3

2 3

bb fb

bb fb

bb fb

bb fb

bb fb

bb fb

bb

b

bb f

b

fb

f

b

f

k C C k C C

k C C k C C

k C C k C C

k

CD C

t

CD C

t

CD

k C C k C C

k C C k C C

tC

k

C k C k C C

k C C k C

C

CC

C k C

k C

D Ct

CD

t

C C k C C

k

7

2

6

5 5 8 6

6

7

5 8 6 7

5 8 7

5

7

5 4 6 3

7

7

6 7

8

5

18

4 6 3

1 8 2 7

8 26

266

2

7

2

8

bb fb

bb fb

bb f

bb fb

bb fb

bb fb

bb b

f b

f

fb b b

b b

f

C

CD C

t

CD C

t

k C C k C C

k C C k C C

k C C k C C

k C C

k C C k C C

k C C k C C

k C C k C C

k C C

k

kD k C C

C k C

k C k

t

C

CC

C C

Boundary Conditions:

*( , ,0) 0.01

( , ,0) 0

( , ,0) 0

( , ,0) 0

CA CA

OQ

LAC

AC

C C m

C

C

C

Definitions:

1 5

2 6

3 7

4 8

( , , ) ( , )

( , , ) ( , )

( , , ) ( , )

( , , ) ( , )

CADA CANE

OQDA OQNE

LACDA LACNE

ACDA ACNE

C C x y t C C x t

C C x y t C C x t

C C x y t C C x t

C C x y t C C x t


Previous WorkApplication of Electrochemical Redox Cycling: Toward

Differentiation of DA and NE

6

• DA and NE exhibits

different

concentration

profiles based on gap

width and can be

differentiated using

this technique.

• NE has a greater

dependence on gap

width than DA.Modified figure, reprinted with permission from Hu, M.; Fritsch, I. “Application of

Electrochemical Redox Cycling: Toward Differentiation of Dopamine and

Norepinephrine”, Anal. Chem., 2016, 88 (11), pp 5574–5578. Copyright 2016

American Chemical Society. Figure has been modified from original


Physical Description

7

Electrode Dimensions

• Width = 4 µm

• Length = 100 µm

• Height= 100 nm

1000 µ

m

2000 µm

OQCA

CA

OQ

OQ

CACA

CA

CA

CACA

CA

CA

CAOQOQ

OQ

OQ

CA CA

CA

CA

CA

CA

CA

OQ

OQ

CA: Catecholamine (DA and NE)

OQ: Catecholamine-quinone

Electrochemically reversible

CA⇌ OQ+ 2e-

OQ

wide elctrodes

wide elctrodes

5 4 4 36

5 4 4 100

d m Gap m

d m Gap m


Redox Cycling of Catecholamines

8

E

t

CA

CAOQ

OQ CA

t

E

CAOQLAC

Diffusion

CALACOQ

OQ

CA

AC

C

Reaction

C’

Reaction

E CA ⇌ OQ + 2e- + 2H+

C OQ LAC

C’ LAC + OQ CA + AC

Generator

Electrode

Collector

Electrode


ResultsE mechanism

9

E Mechanism at 4mm

Generator Potential/mV vs Ag/AgCl Saturated KCl

0 200 400 600 800 1000

To

tal C

urr

en

t/n

A

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

Generator CurrentCollector CurrentMixture Current

E Mechanism at 20mm


0 200 400 600 800 1000

To

tal C

urr

en

t/n

A

-0.40

-0.20

0.00

0.20

0.40

0.60


• The collector efficiency of NE has a greater dependence on the gap width than DA. The different shape in the collector electrode response is due to the longer distances allowing the solution to diffuse away from the electrodes.

• DA and NE present a peak shape in the generator electrode due to mass transfer restrictions.

DA/NE

DA and NE

DA/NE

DA and NE

-2H+-2e-


(CA)

O-quinone

(OQ)

DA and NE

DA/NE

DA/NE

DA and NE


ResultsEC mechanism

10

-2H+-2e-


(CA)

O-quinone

(OQ)

EC Mechanism at 4mm


0 200 400 600 800 1000

To

tal C

urr

en

t/n

A

-0.40

-0.20

0.00

0.20

0.40


EC Mechanism at 20mm


0 200 400 600 800 1000

To

tal C

urr

en

t/n

A

-0.40

-0.20

0.00

0.20

0.40


DA and NE

NE

NE

DA

DA

DA and NE

DA and NE

DA and NE

NE

DA

DANE

kf

Leucoaminochrome

(LAC)

O-quinone

(OQ)

• DA and NE rate constant differ by a factor of 7.5. This provides the opportunity to differentiate them because NE is almost silent.

• Hysteresis appears. Phenomenon that occurs when OQ diffuses away from the electrode to the solution resulting in no OQ at the surface to be reduced allowing OQ to be converted into LAC


ResultsECC’ mechanism

11

-2H+-2e-


(CA)

O-quinone

(OQ)

kf

Leucoaminochrome

(LAC)

O-quinone

(OQ)

Complete Mechanism at 20mm


0 200 400 600 800 1000

To

tal C

urr

en

t/n

A

-0.40

-0.20

0.00

0.20

0.40

Generator Current

Collector Current

Mixture Current

Complete Mechanism at 4mm


0 200 400 600 800 1000

To

tal C

urr

en

t/n

A

-0.40

-0.20

0.00

0.20

0.40Generator CurrentCollector CurrentMixture Current

DA and NE

DA and NE

NEDA

DA

NE

DA and NE

DA and NE

DANE

NEDA

Fast

Leucoaminochrome

(LAC)

kfb

kbb

Catecholamine

(CA)Aminochrome

(AC)

+ +O-quinone

(OQ)

• kfb and kbb were estimated using an equilibrium constant.• Based on the estimated Keq, C mechanism shows no effect to the overall reaction.

26

34

10

2 10

fb

bb

kK

k

cmkfb

s mol


ResultsExperimental vs Computational Data

12

NE becomes “near silent” at 20 µm gap

Experimental vs Computational Data at 4mm Gap

Potential/mV vs Ag/AgCl Saturated KCl

-200 0 200 400 600 800

To

tal C

urr

en

t/n

A

-2.00

-1.50

-1.00

-0.50

0.00

DA Collector Current

NE Collector Current

Mixture Collector Current

Experimental vs Computational Data at 20mm Gap

Voltage/mA

-200 0 200 400 600 800T

ota

l C

urr

en

t/n

A

-2.00

-1.50

-1.00

-0.50

0.00

NE Collector CurrentDA Collector CurrentMixture Collector Current


Conclusions

The catecholamines can be distinguished based on their different cyclization rates by redox cycling methods.

C mechanism can be considered the most predominant mechanism, allowing the differentiation between the catecholamines.

Additional studies are being developed to further minimize the probe dimensions to achieve lower detection limits.

Adaptable for analysis in small spaces–probes for in vivo applications

Electrochemical generation-collection at arrays: Investigation of chemistry through the relationship of space and time resulting from mass transfer and reaction kinetics

Experimental verification of equilibrium constant is needed to refine simulations further


Acknowledgments

Fritsch Research Group

Research was supported partially through the National Science Foundation (Grant CHE-1808286), the University of Arkansas Women’s Giving Circle, and the Arkansas Biosciences Institute, the major research component of the Arkansas Tobacco Settlement Proceeds Act of 2000.


References

EDA=0.65 V at pH 7.4 vs. Ag/AgCl(saturated KCl):

Song, Yuanzhi, et al. "The electrochemical behavior of dopamine at glassy carbon electrode modified by Nafion multiwalled carbon nanotubes." Russian journal of physical chemistry 80.9 (2006): 1467-1474.

ENE=0.66 V at pH 7.4 vs. Ag/AgCl(saturated KCl):

Song, Yuanzhi. "Theoretical study on the electrochemical behavior of norepinephrine at Nafion multi-walled carbon nanotubes modified pyrolytic graphite electrode." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 67.5 (2007): 1169-1177.

kDA=0.13; kNE=0.98; kEP=87 (s-1)

Ciolkowski, E.; Cooper, B.; Jankowski, J.; Jorgenson, J.; Wightman, R., Direct Observation of Epinephrine and norepinephrine Cosecretion from Individual Adrenal-Medullary Chromaffin Cells. Journal of the American Chemical Society 1992, 114 (8), 2815-2821.

Arnsten, A. F. T.; Pliszka, S. R. Pharmacology, biochemistry, and behavior 2011, 99(2), 211-216.


References

Arnsten, A. F. T.; Pliszka, S. R. Pharmacology, biochemistry, and behavior 2011,99 (2), 211-216.

D=5.40×10-6 cm2/s, k0=0.0034cm/s-1

Corona-Avendaño S., Alarcón-Angeles G., Ramírez-Silva M. T., Rosquete-Pina G, Romero-Romo M., Palomar-Pardavé M.; Journal of Electroanalytical Chemistry, 2007,609(1), 17-26.


Development of Microelectrochemical Methods for ... tello_presentati… · Miguel Abrego Tello,...

Documents

Transcript of Development of Microelectrochemical Methods for ... tello_presentati… · Miguel Abrego Tello,...