Using G-Quadruplex/Hemin To “Switch-On” the Cathodic Photocurrent of p-Type PbS Quantum Dots: Toward a Versatile Platform for Photoelectrochemical Aptasensing

Abstract

We present a novel photoelectrochemical (PEC) biosensing platform by taking advantage of the phenomenon that hemin intercalated in G-quadruplex "switched-on" the cathode photocurrent of p-type PbS quantum dots (QDs). Photoinduced electron transfer between PbS QDs and G-quadruplex/hemin(III) complexes with the subsequent catalytic oxygen reduction by the reduced G-quadruplex/hemin(II) led to an obvious enhancement in the cathodic photocurrent of the PbS QDs. For the detection process, in the presence of hemin, the specific recognition of the targets with the sensing sequence would trigger the formation of a stable G-quadruplex/hemin complex, which will result in reduced charge recombination and hence amplified photocurrent intensity of the PbS QDs. By using different target sequences, the developed system made possible a novel, label-free "switch-on" PEC aptasensor toward versatile biomolecular targets such as DNA and thrombin. Especially, with ambient oxygen to regenerate G-quadruplex/hemin(II) to G-quadruplex/hemin(III), this substrate-free strategy not only promoted the photoelectric effect and thus the enhanced sensitivity of the system, but also avoided the addition of supplementary substrates of G-quadruplex/hemin such as H2O2 and organic substances.

Recent Advances in Electrochemical Monitoring of Chromium

“…Such an advantageous sensor has provided high mobility of electrons and holes, conduction bands and mirror-imaged valence of the Pb 5 S 2 I 6 high dielectric constant and its energy band matches that of TiO 2 [ 130 ]. Furthermore, the Pb 5 S 2 I 6 has a low rate of recombination of charge carriers which could be produced after light excitation (absorption of photons), conducting to a higher photo-to-electron out-put [ 131 ]. Moreover, the developed sensor provides an ease signal amplification for the sensitive bioassay of Cr(VI).…”

Photoelectrochemical aptasensing

“…Based on p-type PbS QDs, Wang et. al proposed a label-free "switch-on" PEC aptasensing toward versatile biomolecular targets such as DNA and thrombin [66]. More recently, CdSeTe alloyed QDs were also utilized for enhanced PEC aptasensing [74].…”

“…Using the affinity between specific ions and aptamer sequences, in situ-generated labels upon those adsorbed ions have also been reported for the PEC aptasensing of specific ions [58,62]. G-quadruplex/hemin equipped with p-type PbS labels were, recently, implemented for developing a versatile platform for PEC aptasensing [66]. Still using G-quadruplex/hemin, these authors further proposed a self-operating photocathode for PEC aptasensing, in which the lead ion would induce the allosteric transition of K + -stabilized Gquadruple/hemin to releases hemin to sensitize the p-type NiO electrode [75].…”

Novel photoelectrochemical hydrogen peroxide sensor based on hemin sensitized nanoporous NiO based photocathode

“…[10][11][12][13]. The sensing principles of PEC detection mainly depend on the analytes induced photocurrent change of the photoelectrochemically active species modified electrode.…”