DISSERTATION

______________________________________________________________________ Introduction
1.4 Hybridization detection
Compared to the traditional methods for the detection of DNA sequences, such as electrophoresis
or membrane blots, DNA sensors are faster, simpler and less expensive 53 , and
therefore, present a very active research field. Presently, a wide range of DNA sensor
technologies are in development or being commercialized.
DNA sensors are based on the specific detection of a DNA sequence using a so-called probe
DNA immobilized on the surface 49 (Figure 1.12). Therefore, two main parts of a DNA sensor
are 48 :
- biorecognition interface (immobilized specific DNA sequence) that allows the detection
of a target element (complementary DNA sequence)
- transducer that transforms a detected signal into a readable output
Figure 1.12. Principle of a DNA sensor.
The selective binding, followed by conformational and structural changes in the recognition
layer, can be detected by various techniques. Depending on the transduction approach, DNA
biosensors can be optical, piezoelectric and electrochemical.
Optical DNA sensors based on fluorescence are very sensitive and DNA chips with this
detection scheme have already been commercialized 51 . One of the optical readout strategies is
the detection of an intercalating dye (e.g., ethidium bromide) upon hybridization. Furthermore,
the use of molecular beacons was explored extensively (Figure 1.13). The ends of a molecular
1.4 Hybridization detection 21