Biomedical Engineering Reference
In-Depth Information
14.2.3 Nanomaterials ........................................................................................................
433
14.2.3.1 One-Dimensional Nanomaterials in Biosensor .....................................
434
14.2.3.2 Nanoparticles in Biosensors...................................................................
435
14.2.3.3 Nanoporous Materials in Biosensors .....................................................
437
14.2.4 Functionalized Monolayers....................................................................................
438
14.2.4.1 Langmuir-Blodgett Membranes ............................................................
438
14.2.4.2 Self-Assembled Monolayers ..................................................................
439
14.2.5 Diamond.................................................................................................................
439
References ......................................................................................................................................
440
Biosensors play an important role in clinical detection, environment monitoring, food analysis,
and also in some other fi elds. The advancement of biomaterials has profound direct impacts on the
development of biosensors. On one hand, the application of biorecognition materials determines
the function and use of biosensors based on their biological nature. On the other hand, the intro-
duction of intermedia biomaterials impacts on properties and effi ciencies of biosensors because
of their effects on biorecognition material immobilization and signal transferring. In this chapter,
we have summarized most of the biorecognition materials such as enzymes, microbes, DNA, and
antigens-antibodies that have been used in biosensors, and some special biomaterials mentioned as
intermedia materials in biosensors have been listed. We described processing techniques to prepare
biorecognition materials and intermedia materials and assemble them as functional biosensors.
14.1 BIORECOGNITION MATERIALS
14.1.1 E
NZYMES
Enzymes have been used as analytical reagents for selective detection of special materials since
1940s because of their special catalysis to substrates and selective recognition of coenzymes and
inhibitors correspondingly. Enzymes are the preferred sensitive materials for the preparation of
biosensors. Clark [1] fi rst put forward the principle of the measurement of substrates of enzymes by
combining the specifi city of enzymes with electrodes.
Enzyme biosensors use enzymes as molecular recognition elements immobilized on signal
transducers such as electrochemical electrode, optical fi ber, and fi eld-effect transistor (FET) facility.
Being reagentless, speedy, precise, and even inexpensive, enzyme biosensors are now widely used
in the fi elds of clinical detection, environment monitoring, process controlling, and also in pharma-
ceutical biochemical research [2].
Most of the enzymes belong to the family of proteins, so they possess some basic properties of
proteins such as low active temperature, narrow effective pH range, denaturation or devitalization
in strong acids, alkalies, and heavy metallic salts (physicochemical properties of some enzymes
are listed in Table 14.1). These properties severely limit the application of enzymes in biosensors.
It is one of the most important tasks to overcome these restrictions in the development of enzyme
biosensors.
Up to now, many enzymes such as glucose oxidase (GOD), cholesterol oxidase (COD),
acetylcholinesterase (AChE), horseradish peroxidase (HRP) that have been used in relatively mild
condition in the area of biosensors are described in the following sections.
14.1.1.1 Glucose Oxidase
GOD (β-d-glucose: oxygen 1-oxidoreductase, E.C. 1.1.3.4) is the fi rst enzyme used by Updike and
Hicks in 1967 to prepare biosensors [3]. Due to the broad pH range, high catalytic activity, and rela-
tively wide action temperature, GOD is the most widely used enzyme in biosensor construction.
