Four-stage signal amplification for trace ATP detection using allosteric probe-conjugated strand displacement and CRISPR/Cpf1 trans-cleavage (ASD-Cpf1)

Abstract

High-performance detection of adenosine triphosphate (ATP) is of great importance due to its irreplaceable roles in various physiological processes. In this work, a four-stage signal amplification was established for ATP detection based on an allosteric probe-conjugated strand displacement amplification (SDA) integrated with CRISPR/Cpf1 system (ASD-Cpf1). An allosteric probe (AH) with a hairpin structure was designed to reduce background interference from self-extension and non-specific amplification during the SDA reaction. ATP bound with the aptamer segment at 5′-terminal of AH probe and subsequently opened the AH probe to activate the SDA reaction. The amplification products were recognized by CRISPR/Cpf1 system and triggered the ssDNase activity of Cpf1, resulting in robust cleavage of surrounding DNA FQ-reporter (fluorophore-quencher labeled short single-stranded DNA sequence). With the four-step amplification, ATP was measured with high sensitivity and low background interference. Under the optimal conditions, a linear relationship was obtained between the fluorescence response and ATP concentrations ranging from 2 pM to 10 μM with a limit of detection (LOD) as low as 1.8 pM. Successful detection of ATP in diluted human serum samples further indicated that ASD-Cpf1 system provided a potential platform for detection of small molecules.