Enzyme‐Free Nucleic Acid Circuits for Fold‐Change Detection

The procedure for constructing DNA-only dynamical systems and the implementation of a fold-change detection circuit. The circuit based on the incoherent feed-forward loop is realized using the DNA strand displacement: strand U served as input X, signal A and annihilator D served as output Y and intermediate species Z, respectively.

Abstract

Fold-change detection is widespread in sensory systems of various organisms. Dynamic DNA nanotechnology provides an important toolbox for reproducing structures and responses of cellular circuits. In this work, we construct an enzyme-free nucleic acid circuit based on the incoherent feed-forward loop using toehold-mediated DNA strand displacement reactions and explore its dynamic behaviors. The mathematical model based on ordinary differential equations is used to evaluate the parameter regime required for fold-change detection. After selecting appropriate parameters, the constructed synthetic circuit exhibits approximate fold-change detection for multiple rounds of inputs with different initial concentrations. This work is anticipated to shed new light on the design of DNA dynamic circuits in the enzyme-free environment.