Electronic Supplementary Material
Colorimetric and visual determination of DNase I activity using gold nanoparticles as an
indicator
Yue He, Fen Cheng, Dai-Wen Pang and Hong-Wu Tang*
Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College
of Chemistry and Molecular Sciences, State Key Laboratory of Virology, The Institute for Advanced
Studies, and Wuhan Institute of Biotechnology, Wuhan University, Wuhan, 430072, P. R. China
*Corresponding author, Tel: +86 27 68756759, Fax: +86 27 68754067, E-mail: [email protected]
Optimization of the method
A series of experiments were performed to optimize the conditions with acceptable signal
response. Previously, it is necessary to choose an appropriate dsDNA concentration. Fig. S2
shows the effect of dsDNA concentration on the ratio of absorbance at 520 nm to 650 nm
(A520/A650) in the presence and in the absence of DNase I. From Fig. S2, we find that when
dsDNA is 50 nM, the ratio of [A 520/A650]/[A520/A650]0 (where [A520/A650] and [A520/A650]0 are the
ratio of absorbance at 520 nm to 650 nm (A 520/A650) in the presence and in the absence of DNase
I, respectively) reaches the highest value. The absorption spectra of AuNPs in the presence and in
the absence of DNase I with a fixed concentration of dsDNA (50 nM) was shown in Fig. S3. At
this concentration of dsDNA, there is a big difference between the absorption spectra of AuNPs
in the presence and in the absence of DNase I. As a result, 50 nM was used as the optimized
concentration for dsDNA.
Then we optimized the DNase I-catalyzed digestion reaction time. Fig. S4 shows the UV-vis
absorption spectra of AuNPs in the presence of dsDNA and DNase I as a function of incubation
time. With different enzyme reaction time, the maximum absorption peak of AuNPs solution at
520 nm still remained. Besides, the absorption at 520 nm increases with the increasing reaction
1
time. Meanwhile, the absorption at 650 nm decreases with the increasing reaction time. Fig. 3B
shows the effect of the enzyme reaction time on the ratio of absorbance at 520 nm to 650 nm
(A520/A650), which increases rapidly during the first 5 min, and relatively slow from 5 to 10
minutes, and more slowly after 10 min until reaching equilibrium gradually. Here, we chose 10
min as the optimized DNase I-catalyzed digestion reaction time.
(B)
(A)
(C)
Figure S1.TEM images of AuNPs after addition of (A) ssDNA +NaCl, (B) dsDNA + NaCl, and (C) dsDNA +
DNase I + NaCl.
2
[A520nm/A650nm]/[A520nm/A650nm]0
A
6
5
4
3
2
1
0
50
100
150
200
CdsDNA(nM)
Figure S2. (A) The relation between {[A520/A650]/[A520/A650]0} of the AuNP system and the
concentration of dsDNA. (B) [A520/A650] of the AuNP system as a function of enzyme reaction time.
Inset: photograph of AuNP solutions as a function of enzyme reaction time numbered 1 to 8. (1) 0
min; (2) 1 min; (3) 2 min; (4) 3 min; (5) 5 min; (6) 8 min; (7) 10 min; (8) 20 min.
3
1.0
NO DNase I
Add DNase I
Absorbance
0.8
0.6
0.4
0.2
0.0
400
50 nM dsDNA
500
600
700
800
Wavelength(nm)
Figure S3. UV-vis absorption spectra of AuNPs in the presence and in the absence of DNase I with a
fixed concentration of dsDNA (50 nM).
4
1.0
0 min
1 min
2 min
3 min
5 min
8 min
10 min
20 min
Absorbance
0.8
0.6
0.4
0.2
0.0
400
500
600
700
800
Wavelength(nm)
Figure S4. UV-vis absorption spectra of AuNPs in the presence of dsDNA and DNase I as a function
of incubation time.
5
Table S1. An overview on recently reported nanomaterial-based methods for determination of
activity of DNase I.
Material
Gold
nanoparticle
Gold
nanoparticle
Gold
nanoparticle
Gold
nanoparticle
Gold
nanoparticle
Graphene
oxide
Analytical
LOD (U
Speci
Assay
range (U⋅L‾¹)
⋅L‾¹)
ficity
time
Colorimetric
1104-4104
NRa
NR
NR
Thiol modification
Colorimetric
10-1105
10
NR
1 min
Thiol modification
Colorimetric
5102-4104
NR
NR
2 min
Thiol modification
Method
Biotin and
Colorimetric
NR
15 min
NR
NR
20 min
Fluorometric
2103-7104
1000
NR
NR
10-1000
10
NR
30 min
Ferrocenylation
14-280
7.1
Good
35 min
No modification
chemical
Colorimetric
Ref.
Xu
et
al.,
2006[1]
Zhao et al.,
2008[2]
Zhao et al.,
2008[3]
Zhang et al.,
fluorescein
NR
electrode
a
NR
Colorimetric
Electro-
nanoparticle
7.8-125
2015[4]
modification
Gold
Gold
DNA modification
Liu
No modification
et
al.,
2012[5]
TAMRA
Xu
et
modification
2016[6]
al.,
Sato et al.,
2009[7]
This work
NR stands for ‘‘Not reported’’.
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7