A modified exponential amplification reaction (EXPAR) with an improved signal-to-noise ratio for ultrasensitive detection of polynucleotide kinase.

We applied a modified exponential amplification reaction (EXPAR) strategy to design a label-free and "one-pot" biosensor for ultrasensitive detection of polynucleotide kinase (PNK). This method was also successfully applied in the screening of PNK inhibitors and analysis of the endogenous PNK activity at the single-cell level.