Biosensors and Chemical Sensors - American Chemical Society

Chapter 19 Polymeric Matrix Membrane Field-Effect Transistors Sodium Ion Sensors for Medical Applications

Downloaded by UNIV OF PITTSBURGH on May 4, 2015 | http://pubs.acs.org Publication Date: April 23, 1992 | doi: 10.1021/bk-1992-0487.ch019

S. Wakida Material Chemistry Department, Government Industrial Research Institute, Osaka, Midorigaoka 1-8-31, Ikeda, Osaka 563, Japan

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Sodium ion-selectivefield-effecttransistors (Na ISFETs) were prepared by using three different types of polymeric matrix materials, such as polyvinyl chloride, bio-compatible polymer (polyurethane) and Urushi (natural oriental lacquer). Their electrochemical characteristics were discussed in connection with their characteristics of polymeric matrix membranes. Ion-selective field-effect transistors (ISFETs) are ion sensors that combine the electric properties of gate-insulatorfield-effecttransistors and the electrochemical properties of ion-selective electrodes (ISEs). ISFETs have attracted much attention for clinical and biomedical fields because they could contain miniaturized multiple sensors and could be routinely used for continuous in vivo monitoring of biological fluid electrolytes (e.g., N a , K , C a ^ , CI", etc.) during surgical procedures or at the bedside of the patients in clinical care unit (1). Two types of N a ISFET have been reported so far. One was an inorganic sodiumaluminum-silicate (NAS) glass ISFET, which was fabricated by the hydrolysis of a mixed solution of metal alcoholates, followed by thermal treatment (2), or by the ion implantation technique (3,4). The other type of N a ISFET was prepared by coating with so-called solvent polymeric membrane, such as polyvinyl chloride (PVC) mem brane. In the present paper, the electrochemical characteristics of Na ISFETs with P V C , Urushi and bio-compatible polymer (KP-13, polyurethane) are discussed in connection with their characteristics of polymeric matrix membranes. +

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Experimental Preparation of KP-13. A pre-polymer of KP-13, which has isocyanate groups at its both terminal group, was synthesized with polyethylene oxide, polydimethylsiloxane, polyethylene oxide, polytetramethylene glycol and 4,4 -diphenylmethane diisocyanate in the presence of diazobicycloundecene catalyst at 50 °C for 1 hour in the /

0097-6156/92/0487-0246$06.00/0 © 1992 American Chemical Society

In Biosensors and Chemical Sensors; Edelman, P., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1992.

19. WAKIDA

247

Polymeric Matrix Membrane FETs

mixed solvent of dioxane and N N -dimethylacetamide. The KP-13 was obtained by chain-lengthening reaction of the prepolymer with ethylene glycol at 50 °C for 2 hours. The synthesis of KP-13 is outlined in Scheme 1. The synthetic method was reported in detail elsewhere (5). The antithrombogenicity of the KP-13 shows better results with Lee White test and implantation test in canine vein, compared with Cardiothane™ and Biomer™(5). t

ÇH

2

HO-(CH CH 0) -(SiO) -(CH2CH20) -H 2

2

B

a

CH

c

2


HO-(CH2CH2CH2CH20)b-H

> KP-13 HOCH CH OH 2

2

OCN-^.CH ^NCO 2

Scheme 1 Preparation of KP-13; (a+c):b - 68:32.

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Preparation of sodium PVC/ISFET. N a PVC/ISFETs were obtained by dipcoating with the tetrahydrofuran (THF) solution composed of the mixture of 7.1 wt % of Na ionophore (l,14-tris(r-(2 -oxa-4'-oxo-5'-aza-5 -methyl)dodecanyl)ptopane; E T H 227, Fluka AG), 63.9 wt % of 2-nitrophenyloctylether (NPOE; Dojin Research Laboratories Co. Ltd.), 0.4 wt % of sodium tetraphènylborate (NaBPh4, Dojin Research Laboratories Co. Ltd.) and 28.6 wt % of PVC (Dojin Research Laboratories Co. Ltd.) onto the S13N4 gate of the ISFET devices (0.5 mm χ 5.5 mm χ 0.2 mm; catheter type ISFET donated by Shindengen Electric Mfg. Co. Ltd.) at several times to avoid pin-holes. The resulting N a PVC/ISFETs were allowed to dry overnight. The thickness of the membrane was approximately 0.1 mm. /

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Preparation of sodium Urushi/ISFET. A mixture of 5 wt % of E T H 227, 45 wt % of di-2-ethylhexylphthalate (DOP; Kishida Chemical Co. Ltd.) containing 0.5 wt % of potassium tetrakis(4-chlorophenyl)borate (Dojin Research Laboratories Co. Ltd.) and 50 wt % of Urushi (Saito Urushi Co. Ltd.) was coated on the FET devices and then the resulting Na+ Urushi membranes were hardened for 10 days at 30 °C and 90% relative humidity. The thickness of the membrane was approximately 0.1 mm. The surface of the Urushi matrix membrane was lustrous, smooth and adhesive to the gate of the device. The hardening mechanisms were discussed in detail elsewhere (6). +

Preparation of sodium KP-13/ISFET. N a KP-13/ISFETs were obtained by dip-coating with the THF mixture of 4 wt % of ETH 227,36 wt % of NPOE containing 0.5 wt % of NaBPh4 and 60 wt % of KP-13 onto the device in the same manner as PVC/ISFETs. The thickness of the membrane was approximately 0.1 mm. Measurements with sodium ISFETs. After the prepared ISFETs were conditioned in 10"·* M NaCl solution for a few hours to stabilize the potential response, their potential response was measured vs. Ag/AgCl reference electrode with a sourcefollower circuit (ISFET mV/pH meter; Shindengen Electric Mfg. Co. Ltd.) at 25 °C in the dark. The frozen horse serum (Working Certified Reference Serum for ISEs;

American Chemical Society Library 1155 16th N.W . In Biosensors and Chemical St., Sensors; Edelman, P., et al.; ACS Symposium Series; American Chemical Washington. O.C. Society: 20036 Washington, DC, 1992.

BIOSENSORS AND CHEMICAL SENSORS

248 Chemical Inspection and Testing Institute, Tokyo) was used as the standard blood serum. Results and discussion Sensitivity of sodium ISFETs. The N a ISFETs with PVC, Urushi and KP-13 showed almost the same linear response range in the N a activity range from 10"^·^ M to 1()0 M and showed almost the same sensitivity (slope of potential change per decade) of 55, 53 and 50 mV per decade change of N a activity, respectively as shown in Figure 1. +


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Response times of sodium ISFETs. The response times of the three kinds of N a ISFETs are also within seconds of one another. The above-mentioned charac teristics, such as linear response range, sensitivity and response time are almost the same in P V C , Urushi and KP-13 matrix ISFETs. +

Concn. in blood 6

5

3

4

2

1

0

- log (a ) Na

Figure 1. Calibration curves of Na * ISFETs (a) PVC, (b) Urushi, (c) KP-13. +

Selectivity of sodium ISFETs. The selectivity of the N a ISFETs were evaluated with the selectivity coefficients obtained by the mixed solution method. The selectivity coefficients are summarized in Table I. The selectivity of the P V C and Urushi matrix ISFETs are almost the same, however, KP-13 matrix ISFETs have relatively poor selectivity against K , as compared to the PVC and Urushi matrix ISFETs. Since the concentrations of N a and K of the blood are 138-146 m M and 3.7-4.8 m M respectively, it is considered that N a KP-13/ISFETs have some interference of K in measuring blood serum. +

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Table L Interfering ion(M)

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Logarithms of selectivity coefficients of N a ISFETs 2

Af(M)

logK NaM

pot ) logK NaM

Concn. of

1

pot )

3

pot ) logK NaM

10-1

-1.9

-1.5

0.1

+

10-1

-1.6

-1.6

-0.5

Ca Mg +

10-1

0.1

0.0

-0.7

10-1

-1.8

-2.4

-2.3

K

+

NH

4

2 +

2

1)PVC/ISFET; 2) Urushi/ISFET; 3) KP-13/ISFET


19. WAKIDA

249



It has been reported that the polypropylene glycol (PPG) membrane responds to alkali metals (7). Since KP-13 (a kind of polyurethane) has die same polyether parts as PPG, it is considered that the reason of the different selectivity may be the direct interaction of the polyether part of the KP-13 matrix material. Matrix mechanisms of sodium Urushi and PVC/ISFETs. The electro chemical characteristics, such as linear response range, sensitivity, selectivity and response time of the Urushi matrix ISFETs are similar to those of the P V C matrix ISFETs. The reason of the same characteristics is discussed from the standpoint of matrix mechanisms as follows. The obtained results indicate that these characteristics are mainly determined not by polymeric matrix materials but by sodium-sensing materials, including the membrane solvent (NPOE etc.). Therefore, it is considered that the polymeric matrix materials, such as PVC and Urushi only act as a hydrophobic support polymer and that the major part of surface of the matrix membrane should be covered with the membrane solvent containing the Na ionophore. In the Urushi matrix membrane, it is supposed that the solvent at the surface would be supplied from the porous bulk phase of the mechanically hard Urushi matrix membrane by capillary action, which was discussed in detail elsewhere ( 1 month because of the strong adhesion of the N a sensing membrane to the ISFET device. Johnson et al. reported adhesion studies of some polymeric matrix membrane by using P V C , Urushi and copolymer (vinylcMoride/vinyl alcohol copolymer matrix membrane with treatment of tetrachlorosilane) by using an ultrasonic bath (10). They also reported the use of Urushi gives improved adhesion lasting over 5 hours and that in some cases the membrane lasted for over 20 hours. The stability of the Urushi matrix ISFETs was discussed in detail elsewhere (6). +

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Application to standard blood serum. The potential responses of the N a ISFETs in standard blood serum are shown in Figure 2. In the PVC/ISFETs, the potential value decreased vigorously with time. It is supposed that this behavior is caused by coating with components, such as protein etc., in blood serum over the P V C matrix membrane. The KP-13 and Urushi matrix ISFETs gave a stable response corresponding to the N a activity, though the response time is about 1 minute respectively. The slow response may be due to the adsorption of serum protein. The fairly stable response of the Urushi matrix ISFETs compared with the P V C matrix ISFETs might be brought about by the difference of the solvent supply mechanism. Since the Urushi matrix ISFETs have some drift problems with regard to long term stability of the continuous measurements of blood serum, the studies on the improved bio-compatibility of the Urushi matrix ISFETs are now under way. +


250

BIOSENSORS AND CHEMICAL SENSORS

-

(a) PVC


> Ε

/

'

ί

- χ

w

/

131.4 mM

143.2 mM

.II ο Q_

153.9 mM

1

0

5

,

.

'

...

10

15

Time, min

(b) Urushi -

1

IO 1

h ~

1

1

143.2 mM

1

5

3

9

m

M

131.4 mM ι -

I

ι

ι

ι

ι

ι

ι

ι

5

1

10

15

Time, min

(c) KP-13 - _±ιο

1

y 156.0 mM 140.1 mM 124.5 mM

5

10

15

Time, min

Figure 2. Potential vs. time responses of Na ISFETs in standard blood serum; (a) PVC, (b) Urushi, (c) KP-13. +


19. WAKIDA


251

Acknowledgments The author wishes to thank Dr. Higashi, Dr. Ujihira and Dr. Hiiro for valuable comments and discussions.

Literature Cited


1

Analytical and Biomedical Applications ofIon-SelectiveField-Effect Transistors; Bergveld, P.; Sibbald, Α., Eds.; Comprehensive Analytical Chemistry 23, Elsevier, Amsterdam, 1988. 2 Abe, H.; Esashi, M.; Matsuo, T., IEEE Trans. Electron Devices, 1979, ED-26, pp.1939. 3 Sanada, Y.; Akiyama, T.; Ujihira, Y.; Niki, E., Fresenius' Z.Anal.Chem., 1982, 312, pp.526. 4 Ito, T.; Inagaki, H.; Igarashi, I., IEEE Trans. Electron Devices, 1988, ED-35, pp.56. 5 Kira, K.; Minokami, T.; Yamamoto, N.; Hayashi, K.: Yamashita, I., Seitai Zairyo, 1983, 1, pp.646. 6 Wakida, S.; Yamane, M.; Higashi, K.; Hiiro, K.; Ujihira, Y., Sens. and Actuators, 1990, B1, pp.412. 7 Jaber, Α. M. Y.; Moody, G. J.; Thomas, J. D. R., Analyst, 1977, 102, pp.943. 8 Harrison, D. J.; Cunningham, L. L.; Li, X.; Teclemariam, Α.; Permann, D., J. Electrochem. Soc., 1988, 135, pp.2473. 9 Janata, J., Chem. Rev., 1990, 90, pp.691. 10 Johnson, S.; Moody, G. J.; Thomas, J. D. R., Anal. Proc.,1990, 27, pp.79. RECEIVED October 23, 1991


Biosensors and Chemical Sensors - American Chemical Society

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