Plasmonic
AuNP/g‑C<sub>3</sub>N<sub>4</sub> Nanohybrid-based Photoelectrochemical
Sensing Platform for Ultrasensitive
Monitoring of Polynucleotide Kinase Activity Accompanying DNAzyme-Catalyzed
Precipitation Amplification
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Abstract
A convenient and feasible photoelectrochemical
(PEC) sensing platform
based on gold nanoparticles-decorated g-C<sub>3</sub>N<sub>4</sub> nanosheets (AuNP/g-C<sub>3</sub>N<sub>4</sub>) was designed for
highly sensitive monitoring of T4 polynucleotide kinase (PNK) activity,
using DNAzyme-mediated catalytic precipitation amplification. To realize
our design, the AuNP/g-C<sub>3</sub>N<sub>4</sub> nanohybrid was initially
synthesized through in situ reduction of Au(III) on the g-C<sub>3</sub>N<sub>4</sub> nanosheets, which was utilized for the immobilization
of hairpin DNA<sub>1</sub> (HP<sub>1</sub>) on the sensing interface.
Thereafter, a target-induced isothermal amplification was automatically
carried out on hairpin DNA<sub>2</sub> (HP<sub>2</sub>) in the solution
phase through PNK-catalyzed 5′-phosphorylation accompanying
formation of numerous trigger DNA fragments, which could induce generation
of hemin/G-quadruplex-based DNAzyme on hairpin DNA<sub>1</sub>. Subsequently,
the DNAzyme could catalyze the 4-chloro-1-naphthol (4-CN) oxidation
to produce an insoluble precipitation on the AuNP/g-C<sub>3</sub>N<sub>4</sub> surface, thereby resulting in the local alternation of the
photocurrent. Experimental results revealed that introduction of AuNP
on the g-C<sub>3</sub>N<sub>4</sub> could cause a ∼100% increase
in the photocurrent because of surface plasmon resonance-enhanced
light harvesting and separation of photogenerated e<sup>–</sup>/h<sup>+</sup> pairs. Under the optimal conditions, the percentage
of photocurrent decrement (Δ<i>I</i>/<i>I</i><sub>0</sub>, relative to background signal) increased with the increasing
PNK activity in a dynamic working range from 2 to 100 mU mL<sup>–1</sup> with a low detection limit (LOD) of 1.0 mU mL<sup>–1</sup>. The inhibition effect of adenosine diphosphate also received a
good performance in PNK inhibitor screening research, thereby providing
a useful scheme for practical use in quantitative PNK activity assay
for life science and biological research