Simple, fast, label-free, and nanoquencher-free system for operating multivalued DNA logic gates using polythymine templated CuNPs as signal reporters

Abstract

Boolean logic devices play a key role in both traditional and nontraditional molecular logic circuits. This kind of binary logic, in which each bit is coded by (0, 1), has only two output states—on or off (or high/low). Because of the finite computing capacity and variation, it is facing challenges from multivalued logic gates while processing high-density or uncertain/imprecise information. However, a low-cost, simple, and universal system that can perform different multivalued logic computations has not yet been developed, and remains a concept for further study. Herein, taking the ternary OR and INHIBIT logic gates as model devices, we present the fabrication of a novel simple, fast, label-free, and nanoquencher-free system for multivalued DNA logic gates using poly-thymine (T) templated copper nanoparticles (CuNPs) as signal reporters. The mixture of Cu2+ and ascorbic acid (AA) is taken as a universal platform for all ternary logic gates. Different kinds of poly-T strands and delicately designed complementary poly-adenine (A) strands are alternatively applied as ternary inputs to exhibit the ternary output states (low/0, medium/1, high/2). Notably, there are no nanoquenchers in this platform as poly-A strands can function as not only inputs but also efficient inhibitors of poly-T templated CuNPs. Moreover, all DNA are unlabeled single-strand DNA that do not need sophisticated labeling procedures or sequence design. The above design greatly reduces the operating time, costs, and complexity. More importantly, the ternary logic computations can be completed within 20 min because of the fast formation of CuNPs, and all of them share the same threshold values.