Ultra-sensitive label-free electrochemical detection of the acute leukaemia gene Pax-5a based on enzyme-assisted cycle amplification.

Accurate and sensitive detection of the Pax-5a gene is of great importance in the early diagnosis and prognosis of acute leukaemia. Herein, a label-free electrochemical sensing system was proposed for the detection of the acute leukaemia Pax-5a gene based on enzyme-assisted signal amplification to generate abundant G-quadruplex/hemin DNAzyme. The presence of Pax-5a can open the hairpin probe (HP), which acts as a template. Under the action of the restriction enzymes Nt.BbvCI and Klenow fragment polymerase, the target gene Pax-5a is cycled to open the HP; On the other hand, a large number of G-quadruplex sequences are produced. The resulting G-quadruplex sequence is capable of forming the G-quadruplex/hemin complex on the surface of the electrode in the presence of hemin. The ultrasensitive label-free electrochemical detection of Pax-5a can be realized via the G-quadruplex/hemin complex-catalysed reduction of H2O2, and the detection limit was estimated to be as low as 4.6 fM. In addition, the biosensor has good specificity and stability, and also has excellent detection capabilities in a complex substrate environment. Therefore, the sensor shows great potential in bioanalysis and clinical diagnosis.