Low background catalytic redox recycling coupled with hybridization chain reaction amplification for highly sensitive electrochemical aptamer luteinizing hormone assay

The concentration variation of luteinizing hormone (LH) regulates the cell cycle of oocyte meiosis and significantly affect the whole reproductive cycle. Sensitively quantifying the LH biomarker therefore plays an important role for reproductive disease diagnosis. By coupling a new low background catalytic redox recycling strategy with hybridization chain reaction (HCR), we propose a highly sensitive bio-electrochemical aptamer LH sensing method. LH analyte molecules bind aptamer strands in duplex DNAs to liberate ssDNAs, which trigger HCR generation of [Ru(NH 3 ) 6 ]Cl 3 (RuHex)-modified dsDNA polymers on sensor electrode. Subsequent electrochemical redox recycling of RuHex mediated by K 3 [Fe(CN) 6 ] thus exhibits greatly magnified currents for ultrasensitive LH assay. The synergistic integration of HCR signal amplification with low background redox recycling leads to highly enhanced signal-to-noise ratio and sensitivity for detecting LH down to 6.03 pM. In addition, LH sensing in diluted human serums has been tested and verified, making such sensor a robust detection platform for monitoring diverse biomarkers at low levels for early diagnosing diseases.