An Asymmetric Input Precondition-Gated AND DNA Circuit for Dual-Mutation Analysis

Abstract DNA molecular logic gates typically treat multiple inputs as equal-status Boolean variables, making it difficult to handle the inherent temporal priorities and weight disparities of signals in real biological networks. Here we report a precondition-gated asymmetric AND molecular circuit that achieves logic discrimination of two unequal-weight inputs within a dual-DNAzyme cascade framework. A prerequisite input undergoes signal accumulation through autocatalytic positive feedback, and the resulting gating molecule grants detection access to the secondary input pathway via a de-inhibition mechanism, ensuring that the system responds to the secondary input only after the prerequisite condition is satisfied. A dissipative cycle embedded in the secondary pathway further endows the circuit with chemical renewability after a single response. This design extends conventional AND logic from a condition of spatial co-existence to one governed by priority. Using this circuit for the combined detection of low-prevalence amoxicillin resistance-associated mutations and high-prevalence clarithromycin resistance-associated mutations in Helicobacter pylori infection, as demonstrated in simulated clinical specimens, the system produces a positive output only when both resistance-associated mutations are present, mirroring the decision logic for dual resistance status. This precondition-gated asymmetric AND circuit provides an expandable molecular platform for advancing DNA molecular computation from static combinational logic toward dynamic logic.