Biochemically Modified Electronic Devices

The latter direction was initiated by Danielsson et al. (1979), who combined immobilized hydrogenase with a hydrogen gas-sensing MOSFET. Since the MOSFET requires a high operational temperature it was separated from the enzyme layer. Caras and Janata (1980) directly integrated the microelectronic sensor and the immobilized 

For glucose determination the part of the Teflon membrane covering the Au cathode was covered by a cellulose membrane containing GOD immobilized by glutaraldehyde crosslinking. The response time for glucose was 5-10 min and a linear concentration dependence was obtained between 0.1 and 1 mmol/1. 

A glucose microsensor based on difference measurement between two gold microelectrodes, one covered by native and one by denatured GOD, has been described by Takatsu and Morizuma (1987). This combination permits the elimination of electrochemical interferences without resorting the use of permselective membranes. The gold electrodes were 

A planar glucose sensor using an ISFET in place of the reference electrode has been introduced by the Japanese NEC Corporation (Mura- 

Foulds and Lowe (1986) combined mass production of the base sensor and enzyme immobilization as follows. Using gold or platinum ink, a working and counter electrode were deposited on a ceramic substrate. After thermal treatment of the electrode material a solution containing GOD and a pyrrole derivative of ferrocene was electrochemically polymerized at the electrode. The pyrrole component forms a conducting polymer and the immobilized ferrocene acts as electron acceptor for GOD. The structured immobilization permits this technique to be used for successive enzyme fixation to multiparameter sensors. 

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The results obtained so far with biosensors based on biochemically modified small scale electronic devices demonstrate the possibility of producing multianalyte sensors by Si-chip technology. Although these... 

It will be apparent that the analytical use of bioelectrochemical methods depends on many factors including the use of the novel design of electrodes and the employment of the direct electrochemistry of enzymes, whether modified or not. Probably the defect of all the present methods is the modest sensitivity of bioelectrochemical methods. This is obviously important if these techniques are going to give rise to devices capable of sensing components of the immune system, to say nothing of DNA and RNA analyses. Obviously it is possible to provide considerable amplification from the electronic apparatus associated with the biochemical materials employed but the latter will have to be made more sensitive, perhaps, for example, by a series of coupled enzymatic reactions, before the full advantages of these techniques can be exploited. 

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