Biomedical Engineering Reference
In-Depth Information
Fig. 12.3.
Building blocks of an integrated diagnostic-therapeutic biochip
LOC can analyze minute sample volumes measured in femtoliters (equivalent
to
m
3
). In 1990, researchers at Ciba-Geigy (Basel, Switzerland) coined the
alternate name Micro Total Analysis System (
µ
-TAS) for an LOC [8].
Since biochips are disposable items, many LOCs operate with external
light sources, imaging optics, and 1D or 2D photosensor arrays (solid-state
cameras). However, first LOCs have been realized making use of integrated
light sources and/or photosensors, as, for example, in the OSAILS (optical
sensor array and integrated light source) principle [9].
µ
Diagnostic-Therapeutic Microsystems
The ultimate biochip consists not only of a complete LOC to perform a com-
prehensive analysis of biological, chemical, and physical parameters, it also
includes a therapeutic BioMEMS (Micro-Electro-Mechanical System), such
as a drug delivery or an electro-stimulation sub-system [10] (Fig. 12.3). Before
such a vision of an integral biochip becomes reality, many practical problems
have to be solved, such as the regeneration of biochemical sensing surfaces,
bio-fouling resistance, robustness in the chemically aggressive environment of
the body of animals and human beings, long-term power-supply using bio-
fuel harvesting or inductive coupling, as well as reliable communications with
other implanted systems or the outside world [11].
12.2 Analyte Classes for Optical Biochips
The analytes in our optical biochips were simply illustrated as generic mole-
cules in Fig. 12.2. Depending on the actual biochemical function of the type
of molecule, different classes of analytes are distinguished [4].
12.2.1 DNA (DNA Fragments, mRNA, cDNA)
To map or sequence the genetic information of a cell, DNA chips contain a
large number (up to one million) of different single-stranded DNA fragments
