Universität Siegen, Organische Chemie I,
Adolf-Reichwein-Str. 2, D-57068 Siegen,
Tel: +49 271 740 4370
e-mail: k.chen@chemie.uni-siegen.de
Selective binding and controllable release of the anticoagulant
heparin by electroactive BFD-SAMs in biological buffer solution
Kun Chen, Rochus Breuer, Michael Schmittel
Introduction
Polyanions with a variety of biological activities are important targets for sensing.1 Herein, we present an electroactive self-assembled monolayer (SAM)
based on biferrocenylene (BFD)2, which recognized the highly sulfated glycosaminoglycan, heparin, among several other biological anions (ATP4-, AMP2-,
phytic acid and hyaluronic acid) in biological buffer solution. The binding process can be controlled by switching the BFD between the neutral and
cationic state.
I Synthesis and general description
II Characterization and stability of the SAM in Tris-NO3
buffer solution (pH = 7.24 ± 0.10)
Fe
AlCl3
Fe
-4
2.0x10
O
CS2 / C2H4Cl2
-4
Current (A)
1.0x10
Fe
Fe
Fe
Fe
t-BuNH2
Decane-1-thiol
C2H5OH
BH3
0.0
-4
-1.0x10
-4
-2.0x10
AlCl3
-4
-3.0x10
CH2Cl2
S
S
-0.2
S S
50 mV/s
100 mV/s
150 mV/s
200 mV/s
250 mV/s
300 mV/s
350 mV/s
400 mV/s
450 mV/s
500 mV/s
600 mV/s
700 mV/s
800 mV/s
900 mV/s
1000 mV/s
1250 mV/s
1500 mV/s
2000 mV/s
2500 mV/s
2500 mV/s
-0.1
Br
SH
11
Fe
100
0
-50
-100
0
0
500
1000
1500
Scan rate (mV/s)
2000
2500
-150
-200
-250
-300
-350
0
0.0
0.1
0.2
Potential vs. SCE
0.3
500
1000
1500
Scan rate (mV/s)
2000
2500
0.4
The cyclic voltammetric curves of the SAM
at different scan rates (50 - 2500 mV/s)
Both the cathodic (top) and anodic (bottom)
peak currents showed a good linear
relationship with the scan rate (R = 0.9992)
NH2
H2N
Fe
150
50
gold substrate
S
R = 0.9992
200
Current (µA)
Fe
Current (µA)
Br(CH2)10COCl
Fe
250
10 Br
OH-
Fe
Fe
11
After immersion into the Tris-NO3 buffer
solution for 3 hours, the CV of the SAM did not
show an obvious difference. (SR = 100 mV/s)
10
BFD-SAM in Tris-NO3 buffer solution
After immersed in Tris-NO3 buffer solution for 3 hrs
8
6
4
Current (µA)
2
0
-2
-4
-6
-8
-10
-12
0.0
Current (µA)
0
-4
-8
-12
-16
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
Cyclic voltammetric curves of the SAM in
Tris-NO3 buffer solution (pH 7.24 ±
0.10) at different concentrations of
heparin are depicted (from 1 nM to 0.4
mM). Upon addition of heparin, the
anodic peak did not show response, but
the cathodic peak gave a relative obvious
change. (SR = 100 mV/s)
10
8
4
2
0
-2
-4
OR
The cathodic SWV intensity of BFD-SAMs
vs. concentration of heparin in Tris-NO3
buffer solution (pH 7.24 ± 0.10) is given.
(1 nM to 0.4 mM - from bottom to top).
Titration curve is shown in the insert.
y = -41.8x-172.9
100
R = 0.9904
80
60
OR
O
OR
R=
P
OR
O
0.0
0.3
2-
15
-4
0.1
0.2
Potential vs. SCE
0.3
0.4
6
5
4
0
-5
NH2
N
-15
-20
In presence of 10 H eparin
A fter titration and w ashing w ith w ater
After titration the BFD-SAMs was washed
with deionized water. The potential of the
cathodic SWV peak is almost the same as
that before titration with a lower intensity.
-40
-80
-120
-160
-200
0.0
0.1
0.2
P otential vs. S C E
0.3
0.4
Conclusions
An electroactive BFD-SAMs was developed to sense selectively and
quantitatively the polyanion heparin in biological buffer solution, thus
furnishing an interesting potential for lab-on-chip use.
-25
-0.3
OH
-2
-4
NH2
N
O
-10
OH
AMP2-
-0.2
-0.1
-12
0.0 0.1 0.2 0.3
Potential vs. SCE
-3
0
-8
N
0.4
0.5
0.4
2
N
O
0.3
At present of ATP anion (10 mol/L)
O
B FD -S A M s in T ris-N O 3 B uffer solution
0.0
0.1
0.2
Potential vs. SCE
-6
N
O
O
-4
∆Current (µA)
P
-0.1
4-
10
O
n
O
BFD-SAM in Tris-NO3 buffer solution)
8
Current (µA)
-5
Current (µA)
-7
-6
lo g [p olym e ric u n it]
NH
Hyaluronic acid
10
-3
O
O
-0.2
At present of AMP anion (10 mol/L)
O
0
HO
OH
0.4
BFD-SAM in Tris-NO3 buffer solution
O
O
-15
0.1
0.2
Potential vs. SCE
-10
40
O
O
HO
20
0.0
OH
OH
-10
O
OR
20
40
-8
-5
OR
-0.1
120
-9
0
-10
140
-150
-200
5
Phytic acid (IP6)
160
∆Current (µA)
∆Current (µA)
-100
10
6
-8
-50
At present of hyaluronic acid (10-3 mol/L)
-3
At present of IP6 anion (10 mol/L)
-6
1E-9
1E-8
5E-8
1E-7
6E-7
1E-6
3E-6
5E-6
1E-5
3E-5
1E-4
0.4
BFD-SAM in Tris-NO3 buffer solution
3
Potential vs. SCE
0
15
BFD-SAM in Tris-NO buffer solution)
Current (µA)
4
Current (µA)
1E-9
1E-8
1E-7
1E-6
3E-6
5E-6
7E-6
1E-5
3E-5
1E-4
0.2
0.3
Potential vs. SCE
IV The BFD-SAM furnished
no response to several other
biological anions
III Quantitative binding
and release of heparin
8
0.1
-0.1
P
O
O
O
P
O
O
O
N
O
P
N
N
O
O
OH
OH
ATP4-
0.0
0.1
0.2
Potential vs. SCE
0.3
0.4
Both the cathodic and anodic peaks of the BFD-SAMs did not respond to
ATP4-, AMP2-, phytic acid, and hyaluronic acid in the Tris-NO3 buffer
solution, even at higher concentration (10-3 mol/L) of these biological anions
than heparin (10-4 mol/L) (SR = 100 mV/s).
Acknowledgments
We are greatly indebted to the Deutsche Forschungsgemeinschaft and the
University of Siegen for financial support.
References:
1 a) A. Wada, S. Tamaru, M. Ikeda, I. Hamachi, J. Am. Chem. Soc. 2009, 131, 5321-5330; b) R. B. C. Jagt, R. F. Gómez-Biagi, M. Nitz, Angew. Chem. Int. Ed. 2009, 48, 19951997.
2 C. LeVanda, et al., J. Am. Chem. Soc. 1976, 98, 3181.