Ultrasensitive
Detection of Amyloid β Oligomers
Based on the “DD–A” FRET Binary Probes and Quadrivalent
Cruciform DNA Nanostructure-Mediated Cascaded Amplifier
The reported donor donor–acceptor
(“DD–A”)
fluorescence resonance energy transfer (FRET) was typically achieved
through random collisions and interactions of DNA molecules in the
bulk solution, which has inevitable defects, including weak biological
stability, slow reaction kinetics, and low hybridization efficiency.
In order to overcome these deficiencies, this work developed a quadrivalent
cruciform DNA nanostructure (qCDN)-mediated cascaded catalyzed hairpin
assembly (CHA) amplifier for the fluorescence detection of amyloid β
oligomer species (AβOs). First, four H1 and four H2 hairpins
were assembled on one qCDN to obtain qCDNH1 and qCDNH2, respectively.
In the presence of AβOs, strand C was released from the P1–C
hybrid hairpin and then alternately opened qCDNH1 and qCDNH2 to trigger
the qCDN-mediated CHA. As a result, double donors in H1 and one acceptor
in H2 were mutually closed, and the porous DNA nanonet with a high
loading of “DD–A” FRET binary probes was formed.
The FRET efficiency was approximately 78%, and the initial reaction
rate was 25-fold faster than the conventional CHA. The detection limit
of AβOs was as low as 0.69 pM. The combination of the “DD–A”
FRET binary probes and qCDN-mediated cascaded amplifier exhibited
great promise for detecting biomarkers with trace levels.