Molecularly Imprinted Polymers as Modified Electrodes for Sensing Morphine and Cholesterol
Date Issued
2005
Date
2005
Author(s)
Yeh, Wei-Ming
DOI
zh-TW
Abstract
In this work, molecular imprinted polymers (MIPs) of morphine
(MO) were prepared through precipitation polymerization of methacrylic
acid (MAA) and trimethylolpropane trimethacrylate (TRIM) in the
presence of MO templates. The distributions of particle size,
morphologies, and surface areas were compared with bulk polymerization.
Furthermore, the copolymers of styrene and MAA with different
functional groups were synthesized and the adsorption of MO was
measured. From the Scatchard plot, the dissociation constant and the
maximum amount of adsorption were calculated 0.45 mM and 186
µmole/g, respectively.
Poly(3,4-ethylenedioxythiophene) (PEDOT) was utilized to
immobilize the MIP particles onto the indium tin oxide (ITO) glass as a
MIP/PEDOT-modified electrode. The sensitivity of MIP/PEDOT with
amperometric detection of MO was 41.63 µA/cm2*mM, ranging from 0.1
to 2 mM. The detection limit and imprinting efficiency were 0.3 mM
(S/N=3) and 1.11, respectively. On the other hand, the PEDOT was also
used to prepare the MIP modified electrodes of MO (MIP-PEDOTMO)
and cholesterol (MIP-PEDOTChol) directly. The PEDOT film was capable
of electro-catalyze oxidize of MO and detected MO in MIP-PEDOTMO
modified electrode with the amperometric method. The sensitivity of
MIP-PEDOTMO was 91.86 µA/cm2*mM, ranging from 0.1 to 1 mM MO.
The detection limit was 0.2 mM (S/N=3) and the imprinting efficiency
was 1.32. As for the detection of cholesterol (Chol), Chol was
electro-inactive and the oxidation current of Chol can’t be obtained
directly. Therefore, K3Fe(CN)6 was served as an indicator for the current
response in the solution. As Chol was adsorbed on the MIP-PEDOTChol
IV
modified electrode, the MIP polymer chain shrank and increased the
porosity of MIP. Such an increase in porosity was expected to result in an
increase in the diffusive permeability of the MIP and an enhancement of
Faradic current of the K3Fe(CN)6. The sensitivity of MIP-PEDOT with
indirect amperometric method was 11.768 nA/cm2*µM from 0 to 20 µM.
The imprinting efficiency was 1.81. The capacitive detection of Chol has
been developed using the MIP-PEDOTChol modified electrode. A
capacitance decreased could be obtained as Chol adsorbed on the sites of
MIP film. The sensitivity of capacitance shift was 5.92 µF/cm2*µM from
0 to 10 µM and the imprinting efficiency was 2.21.
Finally, the MIP-PEDOT was prepared on the commercial
interdigital array (IDA). The Ag/AgCl reference electrode (RE) was
prepared with silver glue and FeCl3 solution. The variation of RE
potential was less than 0.4 mV (vs. Ag/AgCl’sat KCl) in 200s. The
sensitivity was 0.0894 A/cm2*mM from 0.01 to 0.10 mM and the
imprinting efficiency was 4.71. The detection limit was 0.02 mM (S/N=3).
With micro-fabrication process, we were able to fabricate the
MIP-PEDOT electrode in a three-electrode system for sensing MO. The
sensitivity on the microelectrode was 171.47 µA/cm2*mM from 0.01 to
0.2 mM MO. The imprinting efficiency and detection limit were 1.19 and
0.2 µM (S/N=3), respectively.
Subjects
嗎啡
膽固醇
分子模版
定電位電流感測
電容感測
微電極
Morphine
cholesterol
molecular imprinted polymer (MIP)
amperometric detection
capacitive detection
micro- electrode
Type
thesis
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