Recent understanding of structure-function of nucleic acids, specifically RNA, opens new perspective in the development of new analytical and diagnostic methods. The discovery of RNA that combines both informational sequences and catalytic and ligand binding activity in the same molecules together with combinatorial library given the possibility to select by in vitro selection techniques (SELEX), aptamers and aptazymes. In this way, in vitro evolution from random sequence libraries makes it possible to built nucleic acids that specifically recognize and bind to virtually any kind of target, such as ions, metabolites, drugs, toxin, peptides and proteins.

RNA aptamers are RNA sequences with an affinity to bind to a particular drug or molecule, They may serve as the basis for novel biosensor schemesthrough tagging the RNA with a fluorescent marker. The fluorescent signal changes when the free aptamer is bound to the target and this change can be quantified using titration techniques. One of our projects is to utilize this concept to detect the binding of theophylline to its well characterized RNA aptamer.