Polymeric Sensors and Actuators

Chapter 5

Biosensors

The first biosensor device was described in 1962 (1). Glucose was analyzed, using a cuprophane-glucose oxidase (GOD)-cuprophane membrane and a pH electrode. Glucose diffused through such a membrane is oxidized to gluconic acid, causing a drop in pH to which the pH electrode is sensitive. Other related applications for clinical use have been reported in the same paper (1).

Afterwards, the interest of research was directed to enzymatic biosensors in order to detect small molecules such as glucose, cholesterol, lactate, and urea. Affinity biosensors have been developed for the detection of biomolecules in very low concentrations.

The essential elements of an electrochemical biosensor are the sensing element and a signal transducer. Biosensors can be classified according to their method of fabrication (2):

• Entrapment within the polymers during the polymerization,
• Simple adsorption onto electropolymerized films,
• Chemical coupling,
• Affinity interactions between bioreceptors and electropolymerized films, or
• Direct electrochemical polymerization of the receptor itself.

Electrically conjugated polymers (CPs) have been extensively used as transducers in electrochemical biosensors to measure and amplify the signals in question. The recent developments on CPs for use as biosensors have been extensively reviewed (3–5).

Commonly used polymers for electrochemical biosensors are poly(aniline), poly(pyrrole), and poly(thiophene). The immobilization of bioactive molecules ...