enzyme-free, colorimetric dna detection system powered by autocatalytic assembly circuits and g-quadruplex dnazymes

Objectives: to develop an enzyme-free colorimetric dna detection system combining autocatalytic assembly circuits with g-quadruplex dnazymes for highly sensitive and visual dna identification.methods: the platform utilized toehold-mediated strand displacement (tmsd) integrated with autocatalytic hairpin circuits and a g-quadruplex dnazyme. buffer conditions, hemin concentration, temperature, and reaction time were optimized. spectrophotometric detection at 416 nm was employed, and nupack software was used for oligonucleotide design validation.results: the optimized system exhibited a detection limit as low as 31 pm. clear electrophoretic band patterns confirmed correct structure formation. the system showed high reproducibility, sensitivity, and a visible signal without enzymatic components.conclusions: this detection method is simple, cost-effective, and highly sensitive, with potential for point-of-care diagnostics, food safety testing, and environmental monitoring. the enzyme-free nature, label-free operation, and modular design make it adaptable to other nucleic acid targets.