Label-free picomolar detection of Pb2+ using atypical icosahedra gold nanoparticles and rolling circle amplification

A novel electrochemical sensing system for Pb(2+) has been developed based on atypical icosahedral gold nanoparticle (AI-AuNPs) modification and the improved rolling circle amplification (RCA). The newly synthesized AI-AuNPs which were applied to modify the gold electrode surface greatly enhanced the sensitivity and expanded the detection range due to its large specific surface area and a large density of irrational kinks and step atoms on the particle surface. Additionally, the improved RCA introduced a manipulated circular template DNA which can be hybridized with the primer obtained from the DNAzymes catalysis reaction in the presence of Pb(2+) as a cofactor to simplify the RCA procedure, and the largely elongated RCA products at the same time efficiently blocked the electron transfer at the electrode surface, thus significantly increased the electrochemical signal. The design of the label free electrochemical impendence sensing strategy was evidenced to be a highly sensitive and selective method for the lead ions monitoring compared with the previous reports and the detection range was 1 pM-1 μΜ with a detection limit of 290 fM (3δ rule). Furthermore, the proposed detection system was also environmental-friendly and inexpensive, which can be successfully used in real serum sample detection.