Single-particle
electrochemical collision has gained great achievements
in fundamental research, but it is challenging to use in practice
on account of its low collision frequency and the interference of
the complex matrix in actual samples. Here, magnetic separation and
DNA walker amplification were integrated to build a robust and sensitive
single-particle electrochemical biosensor. Magnetic nanobeads (MBs)
can specifically capture and separate targets from complex samples,
which not only ensures the anti-interference capability of this method
but also avoids the aggregation of platinum nanoparticles (Pt NPs)
caused by numerous coexisting substances. A low amount of targets
can lead to the release of more Pt NPs and the generation of more
collision current transients, realizing cyclic amplification. Compared
with simple hybridization, a DNA walker can improve the collision
frequency by about 3-fold, greatly enhancing detection sensitivity,
and a relationship between collision frequency and target concentration
is used to realize quantification. The biosensor realized an ultrasensitive
detection of 4.86 fM human immunodeficiency virus DNA (HIV-DNA), which
is 1–4 orders of magnitude lower than that of traditional methods.
The successful HIV-DNA detection in complex systems (serum and urine)
demonstrated a great promising application in real samples and in
the development of new single-entity biosensors.
Sensitive detection
of human immunodeficiency virus DNA (HIV-DNA)
is essential for timely diagnosis and cure of the illness. Herein,
a novel “enrichment–stowage–cycle” strategy
was proposed to fabricate a multiple amplified electrochemiluminecence
(ECL) biosensor for HIV-DNA detection. On the basis of the enrichment
role of magnetic nanobeads, assembly role of copolymer nanospheres
and strand displacement amplification (SDA), the processes were named
as “enrichment”, “stowage”, and “cycle”,
respectively. The method employed electrochemiluminescent nanospheres
(ENs) as signal labels by assembling three layers of CdSe/ZnS quantum
dots (QDs) onto the surface of copolymer nanospheres. Compared to
QDs, the same concentration of ENs can the enhance the ECL intensity
by about 11.3-fold. SDA could further amplify the signals by about
3.77-fold, possessing high sensitivity for low-abundant biomarkers
detection. The integration of magnetic separation improved detection
specificity and stability, making the method possible for practical
application. On the basis of magnetic separation, ENs and SDA, the
ECL biosensor realized ultrasensitive detection of 39.81 fM HIV-DNA,
which was more sensitive than other HIV-DNA analytical methods, with
a wide dynamic range of 0.05 pM to 50 nM. The successful detection
of HIV-DNA in complex samples with good sensitivity and accuracy indicated
its potential utilization in early judgment of diseases and fabrication
of signal amplification platforms.
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