Aptamer/organometallic receptor-based and label-free sensitive electrochemical detection of amino acid via multi-pedal DNA walker/DNAzyme amplifications

Sensitive and accurate monitoring of amino acid concentration variations plays an important role for diagnosis of diseases at early stage. Here, the aptamer/organometallic receptor-based methodology for label-free and amplified electrochemical determination of phenylalanine, an amino acid, through multi-pedal DNA walker and DNAzyme dual signal enhancement is demonstrated. The binding of the phenylalanine/organometallic receptor complex with the aptamer results in the release of active DNAzyme walking strands to trigger the multi-pedal DNA walkers to move on the surface of electrode. The substrate hairpins are then cyclically cleaved by the DNA walkers to liberate a large number of free G-quadruplexes, which interact with and confine hemin on the electrode via the G-quadruplex/hemin structures. Significantly amplified current signals can therefore be generated by electrochemical reduction of hemin for the sensitive measurement of phenylalanine down to 1.03 μM. Such an aptasensor also has a high selectivity and can monitor phenylalanine in diluted serums, making it a promising alternative for the development of versatile and robust aptamer-based platforms for detection of various amino acids.