DNA Colorimetric Logic Gates Based on Triplex–Helix Molecular Switch

A horseradish peroxidase (HRP)-mimicking DNAzyme sequence is first blocked by the triplex-based molecular beacon (tMB). Upon hybridization with single-stranded DNA inputs, triplex–helix molecular switch occurs, and the released product strand self-assembles into the hemin/G-quadruplex-HRP-mimicking DNAzyme that biocatalyzes the formation of a colored product and provides an output signal for the different logic gates. On the basis of this principle, a series of logic gates (OR, XOR, INHIBIT, and AND) have been developed. Moreover, a multilevel circuit (MC) that enforces an overall OR Boolean behavior is developed by connecting the AND and XOR logic gates. The logic output signals can be recognized by naked eyes, thus providing a flexible, secure, economic, and simple method for designing a complex DNA-based logic device.