Development of an electrochemical sensor based on the catalysis of ferrocene actuated hemin/G-quadruplex enzyme for the detection of potassium ions. 
Sensitive and selective sensors need to be explored to detect the physiological potassium level due to its important role in the living organisms.  In the present system, a novel electron transfer mediator actuated electrocatalytical biosensor was demonstrated to assay K(+) based on the conformational change of DNA.  With the hybridization between the complementary bases and the self-folding of guanine-rich nucleic acid sequence, the horseradish peroxidase-mimicking enzyme (HRP-DNAzyme) was formed and brought to approach the ferrocene (Fc) unit on Au nanoparticles (AuNPs).  Thus, in the system, Fc unit acted as the relay, stimulating the electrical contact of HRP-DNAzyme with the electrode to obtain the bioelectrocatalyze reduction signal.  Under the Fc actuated catalysis of HRP-DNAzyme and amplification of Au nanoparticles, the obtained biosensor exhibited a sensitive detection for K(+).  A satisfying result of a wide linear range and low detection limit were obtained with the novel electrocatalytical biosensor which was then applied in real samples.