Lead ions (Pb 2+ ) are a well-known toxic heavy metal that poses a significant threat to human health. Therefore, the development of a simple and ultrasensitive technique for detecting Pb 2+ is essential. With their trans -cleavage properties, the newly discovered CRISPR-V effectors have become a potential high-precision biometric tool. In this regard, a CRISPR/Cas12a-based electrochemical biosensor (E-CRISPR) has been developed, which is combined with the GR-5 DNAzyme that can specifically recognize Pb 2+ . In this strategy, the GR-5 DNAzyme acts as a signal-mediated intermediary, which can convert Pb 2+ into nucleic acid signals, thereby becoming single-stranded DNA that triggers strand displacement amplification (SDA) reaction. This is coupled with following activated CRISPR/Cas12a cleavage of the electrochemical signal probe, enabling cooperative signal amplification for ultrasensitive Pb 2+ detection. The proposed method has a detection limit as low as 0.02 pM. Therefore, we have developed an E-CRISPR detection platform with GR-5 DNAzyme as a signal medium (called SM-E-CRISPR biosensor). This provides a method for the CRISPR system to specifically detect non-nucleic substances by converting the signal using a medium.
Lead ions are deleterious pollutants that often reach drinking water, and can cause significant harm to humans (particularly children). An ultra-sensitive lead ion detection method using a whispering gallery mode (WGM) optofluidic microbubble resonator and the classic GR-5 DNAzyme is proposed in this paper. With the auxiliary piranha and Ploy- l -lysine solution, GR-5 DNAzyme was successfully modified on the inner wall of a microbubble. The mode field distribution of the microbubble was analysed, and the optofluidic sensor with thin wall exhibited a maximum bulk refractive index sensitivity of 265.2 nm/RIU. Lead ions at concentrations ranging from 0.1 pM to 100 pM were tested using the proposed WGM optofluidic sensor. The noise was decreased to 2.43 fM using the self-referenced differential method. Thus, a limit of approximately 15 fM was obtained for the detection of lead ions using the WGM optofluidic biosensor. Eight competing metal ions were also used to evaluate the selectivity of the proposed sensor, with results indicating that it has high selectivity for lead ions. Finally, the sensor performance is verified using real samples.
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