Structure-adaptive dual-function poly-T sequences enable a homogeneous label-free colorimetric sensing platform

Compared with the extensive research on G-rich nucleic acids, the catalytic properties of T-rich sequences have received limited attention. Herein, the peroxidase-like activity of poly-T sequences was investigated, and the results demonstrated that the poly-T sequences can display peroxidase-like activity with acetic acid as an activator, and the catalytic efficiency is positively correlated with sequence length. Based on this, we constructed a novel homogeneous colorimetric sensing platform with melamine as the target. The platform utilizes a long-chain poly-T sequence to catalyze the TMB-H₂O₂ chromogenic reaction in acetate buffer. The introduction of melamine induces the formation of the T-melamine-T structure, which causes a conformational change and significantly suppresses its catalytic activity. The dual-function design integrates the catalytic and recognition roles in a single ssDNA sequence, enabling rapid on-site detection via structure-dependent activity modulation.