Researchers now have more tools to enable synthetic biologic solutions.

Scientists from Harvard’s Wyss Institute for Biologically Inspired Engineering; Arizona State University (ASU), Tempe; Northwestern University, Evanston, Illinois; and the Technical University of Munich have developed new tools for use in the development of diagnostic and other devices based on synthetic biology.

Previously, the researchers from Harvard and Arizona State had created “riboccomputing devices” that act as “molecular logic boards,” sensing multiple RNA signals simultaneously and producing specific proteins if the right combination of signals are present.

In the latest effort, they worked with colleagues at Northwestern and the Technical University of Munich to develop two types of repressor elements that can switch off protein production in response to nucleotide sequences.

These tools are useful for developing the artificial networks of genes and modular regulatory elements required to make devices based on synthetic biology that can sense biological signals and respond by producing other signals, therapeutics proteins, or even enzymes that can mediate other transformations.

To design synthetic biologic networks, it is equally important to have tools that can switch protein production on and off. In this case, the researchers constructed a library of more than 100 repressors, which consist of reversed “Toehold Switches.” The de novo-designed RNA strands, rather than result in protein production when trigger RNAs are detected, undergo a structural change that hides the necessary binding site and therefore halts protein translation.

Up to 4 different repressor elements were combined in NAND (NOT AND) and NOR (NOT OR) gates to stop the production of specific proteins. The scientists believe the new tools will be useful in the development of next-generation diagnostics and environmental reporting devices, as well as in bioprocessing.

This illustration shows how a complex synthetic RNA containing multiple programmable Riborepressors (long teal blue strand) is bound by incoming trigger RNAs (shorter red and green RNA strands) that change the Riborepressors’ secondary structures to block the protein-synthesizing ribosome from accessing its binding sites (purple and light blue structure in the center).