Sensitive Electrochemiluminescence Biosensor Based on the TargetTrigger Difference of the Electrostatic Interaction between an ECLReporter and the Electrode Surface

The discrepancy of the electrostatic interaction of negatively chargedsignal molecules to long and short DNA strands of the modified electrode surface hasbeen used for thefirst time to the develop an electrochemiluminescence (ECL)biosensor for human papillomavirus 16 (HPV 16) DNA detection. The short single-stranded capture probe (CP) was modifiedfirst on the surface of the gold electrode,which only has a small amount of negative charge. The electrostatic interactionbetween the negatively charged tris(2,2 '-bipyridyl) ruthenium(II) chloride hexahy-drate-doped SiO2nanoparticles (Ru@SiO2NPs) and CP is weak, hence Ru@SiO2NPs easily diffuse to the surface of the electrode to generate a strong ECL signal.Hybrid chain reaction (HCR) amplification products (long strand dsDNA) wereprepared in homogeneous solution in advance. When the target was present, the dsDNA can be connected on the electrode surfaceand cause the enhancement of the negative charge on the electrode surface. Owing to electrostatic interaction and steric hindrance,Ru@SiO2NPs are difficult to diffuse to the electrode surface, resulting in a significantly reduced ECL signal. The decrease of ECLsignal is linearly correlated with the logarithm of the HPV concentration under optimal conditions, with the detection range being0.1 fM-5 pM with a limit of 1.41 aM. This innovative methodology expands the application of electrostatic interaction in ECLsensing, but can also easily develop biosensors for detecting other targets by changing the DNA sequence used in this strategy.