Abstract. RNA-based technologies are among the most important tools in biotechnology due to the ability of RNA molecules to specifically recognise nucleic acids and small-molecules. RNA molecules play important roles in post-transcriptional regulation. RNA stability and function depends critically on global interactions, which often prevents the use of a modular design strategy, particularly with allosteric conformations. Computational methods, using standard secondary structure predictions, can produce RNA switches working in E. coli if we incorporate evolutionary computation algorithms. Our aim is to develop a predictive methodology to design synthetic RNA circuits that will measure endogenous RNA levels in living cells. We have engineered and experimentally validated a new type of RNA molecule (“regazyme”) that suffers a conformational change after binding to a trigger RNA, subsequently activating a ribozyme that self-cleaves and releases an sRNA that can activate a reporter gene. We have also engineered an RNA-based tunable antiterminator, a TNA-derived adaptor that acts as a signal converter in the genetic circuit, “converting a translation signal to a transcription signal by closely interfacing the ribosome and the RNA polymerase” We used computational design to engineer higher-order RNA-triggered riboregulators, by programming a hierarchical toehold activation cascade and studying single cell and population level activation in E. coli. These RNA riboregulators can be used for construction of new, complex and portable synthetic gene circuits. We have also engineered an antisense RNA that can be used to suppress or activate a gene at the post-transcriptional level (2). We used biophysical rules to devise the computational design of these RNA regulatory units. In-silco evolution methods have some limitations that we are also using alternate method T7 bacteriophage as a tool for directed evolution. I have engineered a recombinant T7 phage that will be used for directed evolution of novel biomolecules such as RNA, regazyme and proteins. These biomolecules could be used in the future for medically relevant applications such as detection of specific small molecules, proteins and nucleic acids (disease diagnosis), and as antimicrobial agents.