Ultra-sensitive and absolute quantitative detection of Cu²⁺ based on DNAzyme and digital PCR in water and drink...

Here, we developed an ultra-sensitive and absolute quantitative detection method of Cu²⁺ based on DNAzyme and digital PCR. The binding model between DNAzyme and Cu²⁺ and the influence caused by the additional primer sequence were revealed to ensure quantitation independent of standard curves. The binding model of DNAzyme and Cu²⁺ showed that one molecular DNAzyme could bind one Cu²⁺ in the biosensor step. Thus, the final quantitative results, evaluated by three parallels, showed that the limit of quantitation (LOQ) was as low as 0.5pmol, while the sensitivity was evaluated as 50fmol. The specificity evaluation of our methodologies shows that extremely low crossing signal is existed within the non-specific ions. Moreover, the results of practical detection have shown that the quantitative results were stable and accurate among different food substrates. In conclusion, a flexible quantitative detection method with ultra-sensitivity was developed to detect trace amounts Cu²⁺ within different substrates.