Abstract
A DNA electrochemical sensor was fabricated using the modification of a glassy carbon electrode (GCE) with ordered mesoporous carbon nitride (MCN), electrodeposited gold nanoparticles (EAu) and methylene blue (MB)/nanoAu/MCN as the signal amplifier, in which MB was inserted into the nanoAu/MCN composites for Pb2+ detection. The secondary structure of the trans-cleaving 8-17 DNAzyme, composed of the substrate strand (S1) and the enzyme strand (S2), was utilized for the sensor fabrication. S1 immobilized on the signal amplifier could hybridize with S2 and form a DNA double helix structure on account of the principle of complementary base pairing. With the activation of Pb2+, S2 was able to cleave the single RNA linkage with S1 by hydrolysis reaction to break S1 into two fragments. One of the fragments NS1' that was immobilized on the MB/nanoAu/MCN signal amplifier (S1'/MB/nanoAu/MCN) could hybridize with the DNA probe S3 immobilized on the modified electrode. With the help of the MCN's large specific surface area and the gold nanoparticles' good charge-transport capacity, the sensor exhibited excellent sensitivity and selectivity. The proposed sensing strategy represented a wide linear response in the range from 1.0 x 10(-3) to 1.0 x 10(-14) M. The sensor was also tested with real samples and represented a promising method for detecting Pb2+.