Instrument-free visual detection of tetracycline on an autocatalytic DNA machine using a caged G-quadruplex as the signal reporter.

An instrument-free visual biosensor for the amplified detection of tetracycline has been successfully constructed using an autocatalytic DNA machine as the signal amplifier and a caged G-quadruplex as the signal reporter. The assay is ultrasensitive, enabling the visual detection of trace levels of tetracycline as low as 1 pM without instrumentation.