-
Matter, Volume 2
Supplemental Information
Investigation of Cortisol Dynamics
in Human Sweat Using
a Graphene-Based Wireless mHealth System
Rebeca M. Torrente-Rodríguez, Jiaobing Tu, Yiran Yang, Jihong
Min, Minqiang Wang, YuSong, You Yu, Changhao Xu, Cui Ye, Waguih
William IsHak, and Wei Gao
-
Matter, Volume 2
Supplemental Information
Investigation of Cortisol Dynamics
in Human Sweat Using
a Graphene-Based Wireless mHealth System
Rebeca M. Torrente-Rodríguez, Jiaobing Tu, Yiran Yang, Jihong
Min, Minqiang Wang, YuSong, You Yu, Changhao Xu, Cui Ye, Waguih
William IsHak, and Wei Gao
-
Figure S1. Schematic of modification procedure of the graphene
electrode for cortisol sensing.
LGE
PPAPolymerization
BSA blocking
Cortisol recognition
EDC/Sulfo-NHSactivation
Ab immobilization
-
Figure S2. Characterization of the graphene sensor. Differential
pulse voltammetry (DPV) in
2.0 mM of K4Fe(CN)6/K3Fe(CN)6 (1:1) after each modification
step.
0
10
20
30
40
50
60
-0.2 0 0.2 0.4
-I (µ
A)
E (V)
Bare
pPPA
CAb
BSA
Cortisol-HRP
-
Figure S3. Electrochemical cortisol sensor optimization. Effect
of cortisol-HRP dilution factor
on amperometric signals. Data are represented as mean ± SD (n =
3).
0.0
1.0
2.0
3.0
4.0
0
100
200
300
400
500
1/300 1/200 1/100
I 0.0/
I 10.0
-I (n
A)
Cortisol-HRP dilution
Blank 10 ng mL-110.0 ng/mL0.0
-
Figure S4. Performance characterization of the graphene-based
electrochemical sensors.
Effect of various pHs (A), ionic strengths (B), and presence of
interferential molecules (5.0 ng/mL)
(C). PBST, phosphate buffered saline with Tween® 20.Data are
represented as mean ± SD (n = 3).
A B C
0.0
0.5
1.0
1.5
2.0
2.5
0
100
200
300
400
0.1X 1X 5X 10X
I 0.0/
I 5.0
-I (n
A)
PBST concentration
Blank 5.0 ng mL-15.0 ng/mL0.0
0.0
0.5
1.0
1.5
2.0
2.5
0
100
200
300
400
7.4 5.5 4.1
I 0.0/
I 5.0
-I (n
A)
pH
Blank 5.0 ng mL-15.0 ng/mL0.0
0.0
0.5
1.0
1.5
2.0
2.5
0
100
200
300
400
I 0.0/
I 5.0
-I (n
A)
Blank 5.0 ng mL-15.0 ng/mL0.0
-
Figure S5. Stability test of the graphene-based electrochemical
sensors. Variation of
amperometric responses for 0.0 and 5.0 ng/mL cortisol with time.
Data are represented as mean ±
SD (n = 3).
0.0
0.5
1.0
1.5
2.0
2.5
0
100
200
300
400
day 0 day 1 day 2 day 4 day 5 day 7 day 10 day 26 day 35
I 0.0/
I 5.0
-I (n
A)
Blank 55.0 ng/mL0.0
-
Figure S6. Optimization of platform design. 3-channel
amperometric signals obtained with two
platform designs in 1,000,000X diluted HRP-cortisol, 2.0 mM HQ
and 1.0 mM H2O2 in 50 mM
phosphate buffer (pH 6.0). The platform with asymmetric
working-to-reference design (A)
displays larger variations in signals obtained as compared with
a symmetric design (B).
0
250
500
750
1000
1250
0 50 100 150
E (m
V)
Time (s)
WE1
WE2
WE312
3
0
250
500
750
1000
1250
0 50 100 150
E (m
V)
Time (s)
WE1WE2WE3
A B
12
3
-
Figure S7. Proportional error evaluated for the GS4 based on
real sample recovery studies.
0.0
2.0
4.0
6.0
8.0
10.0
0.0 2.0 4.0 6.0 8.0 10.0
Rec
over
ed c
ortis
ol (n
g/m
L)
Actual cortisol (ng/mL)
Measured value
-
Figure S8. Thermal image of the sensor patch on human
forearm.
-
Figure S9. Influence of temperature on sensor performance.
Amperometric responses for 0.0,
1.0 and 5.0 ng/mL cortisol incubated at room temperature (25
°C), 31 °C and 37 °C. Data are
represented as mean ± SD (n = 3).
0
100
200
300
400
25 37
-I (n
A)
31Temperature (oC)
Blank
1.0
5.0
ng/mL
ng/mL
0.0
-
Figure S10. Iontophoresis based sweat sampling. Illustration of
iontophoresis-assisted sweat
stimulation on a subject’s forearm, and principles of sweat
stimulation and cortisol excretion in
sweat.
-
Figure S11. Influence of time of exercise in cortisol variation.
Cortisol level evaluated in sweat
and its relative percentage change of two healthy subjects
before and after physical exercise
conducted in the morning (AM) and in the afternoon (PM).
0
20
40
60
80
100
0.0
2.0
4.0
6.0
8.0
AM PM
% C
hang
e
Cor
tisol
(ng/
mL)
Time of exercise
10 min 50 minSubject 1
0
50
100
150
200
250
0.0
1.0
2.0
3.0
AM PM
% C
hang
e
Cor
tisol
(ng/
mL)
Time of exercise
10 min 50 minSubject 2
A B
-
Figure S12. Salivary cortisol at several time points across the
cold pressor test for four subjects
(C1-C4) from the human study presented in Figure 5.
0.0
2.5
5.0
7.5
10.0
Sal
ivar
y co
rtiso
l (ng
/mL)
C1
C2
C3
C4
CPT +
8 min
CPT +
16 mi
n
CPT +
24 mi
n
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