TABLE OF CONTENTS The most important application of biochips is biorecognition, and biorecognition is based on key-lock type of reactions. To this regard, we have investigated the physics of biochemical reactions and determined the kinetics of the most important reactions, like DNA hybridization and enzymatic reactions for proteins. These kinetics, however, can be modified by the concentration of reacting species (analytes or targets), and the coupling between biochemical reactions and advection-diffusion of reagents in the biochip is essential. Finally, we have distinguished between two types of reactions, the sandwich reaction, which derives directly from the key-lock approach, and the displacement reactions that are more complex and require the use of an analog to the target.
At this point, it is essential to point out that detection is an important part of the conception of any biochip. It is not sufficient to have a very efficient capture by hybridization or immunorecognition if there is no sensitive detection associated with it. The reading of the biochip reactive surface should be at least as sensitive as the reaction itself. Detection is not the subject of this book; let us just mention that the research on detection for biochip recognition is the topic of abundant literature, and is a field that is constantly improving. Developments are aimed in two directions: first, improvements in the detection method itself, like improving the fluorescence by using new fluorophores (e.g., quantum dots) or developing enzymatic amplification for detection; second, improvements of the design and materials, like improved waveguides in the case...
