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Plasmonic AuNP/g‑C3N4 Nanohybrid-based Photoelectrochemical Sensing Platform for Ultrasensitive Monitoring of Polynucleotide Kinase Activity Accompanying DNAzyme-Catalyzed Precipitation Amplification

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journal contribution
posted on 22.04.2015, 00:00 by Junyang Zhuang, Wenqiang Lai, Mingdi Xu, Qian Zhou, Dianping Tang
A convenient and feasible photoelectrochemical (PEC) sensing platform based on gold nanoparticles-decorated g-C3N4 nanosheets (AuNP/g-C3N4) 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-C3N4 nanohybrid was initially synthesized through in situ reduction of Au­(III) on the g-C3N4 nanosheets, which was utilized for the immobilization of hairpin DNA1 (HP1) on the sensing interface. Thereafter, a target-induced isothermal amplification was automatically carried out on hairpin DNA2 (HP2) 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 DNA1. Subsequently, the DNAzyme could catalyze the 4-chloro-1-naphthol (4-CN) oxidation to produce an insoluble precipitation on the AuNP/g-C3N4 surface, thereby resulting in the local alternation of the photocurrent. Experimental results revealed that introduction of AuNP on the g-C3N4 could cause a ∼100% increase in the photocurrent because of surface plasmon resonance-enhanced light harvesting and separation of photogenerated e/h+ pairs. Under the optimal conditions, the percentage of photocurrent decrement (ΔI/I0, relative to background signal) increased with the increasing PNK activity in a dynamic working range from 2 to 100 mU mL–1 with a low detection limit (LOD) of 1.0 mU mL–1. 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.