Renewable Electrochemiluminescence
Biosensor Based
on Eu-MOGs as a Highly Efficient Emitter and a DNAzyme-Mediated Dual-drive
DNA Walker as a Signal Amplifier for Ultrasensitive Detection of miRNA-222
Herein, novel europium metal–organic gels (Eu-MOGs)
with
excellent cathode electrochemiluminescence (ECL) emission are first
used to construct biosensors for the ultrasensitive detection of miRNA-222.
Impressively, N and O elements of organic ligand 2,2′:6,2″-terpyridine
4,4′,4″-tricarboxylic acid (H3-tctpy) can perfectly
coordinate with Eu3+ to form Eu-MOGs, which not only reduce
nonradiative transition caused by the intramolecular free rotation
of phenyl rings in other MOGs to enhance the ECL signal with extraordinary
ECL efficiency as high as 37.2% (vs the [Ru(bpy)3]2+/S2O82– ECL system)
but also reinforce ligand-to-metal charge transfer (LMCT) by the strong
affinity between Eu3+ and N and O elements to greatly improve
the stability of ECL signals. Besides, an improved nucleic acid cascade
amplification reaction is developed to greatly raise the conversion
efficiency from target miRNA-222 to a DNAzyme-mediated dual-drive
DNA walker as output DNA, which can simultaneously shear the specific
recognition sites from two directions. In that way, the proposed biosensor
can further enhance the detection sensitivity of miRNA-222 with a
linear range of 10 aM–1 nM and a detection limit (LOD) of 8.5
aM, which can also achieve an accurate response in cancer cell lysates
of MHCC-97L and HeLa. Additionally, the biosensor can be self-regenerated
by the folding/unfolding of related triplets with pH changes to simplify
experimental operations and reduce the cost. Hence, this work proposed
novel MOGs with stable and intense ECL signals for the construction
of a renewable ECL biosensor, supplying a reliable detection method
in biomarker analysis and disease diagnosis.