Enzyme-Free Unlabeled DNA Logic Circuits Based on Toehold-Mediated Strand Displacement and Split G-Quadruplex Enhanced Fluorescence

Adopting fluorescence of PPIX enhanced by a split G-quadruplex and toehold mediated strand displacement reaction, a series of unlabeled fluorescent logic gates is set up and some of them are cascaded into circuits. Controlled release of PPIX, which is also a photosensitizer in photodynamic diagnosis and therapy, is realized by this circuit, making it a wise choice for DNA computing.