Enzyme-Free Photoelectrochemical Biosensor Based on the Co-Sensitization Effect Coupled with Dual Cascade Toehold-Mediated Strand Displacement Amplification for the Sensitive Detection of MicroRNA-21

Abstract

An ultrasensitive photoelectrochemical (PEC) biosensor was developed based on cosensitization of biocompatible CuInS 2 /ZnS quantum dots (ZCIS QDs) and N-doped carbon dots (N-CDs) coupled with dual cascade toehold-mediated strand displacement amplification (dual cascade TSDA) for microRNA-21 (miRNA-21) detection. On the one hand, the TiO 2 /Au hybrid structure was used to immobilize double stranded DNA (thiolated capture strand and carboxylated signal strand), which could capture glutathione stabilized ZCIS QDs and N-CDs. The original TiO 2 /Au/ZCIS/N-CDs structure formed a cascade band gap arrangement, which provided a good band position for effective charge carrier separation, thus improving PEC performance and resulting in an evident decrease in photocurrent signal after the release of signal strands (SIG). On the other hand, the sensitivity of the biosensor was further enhanced by enzyme-free dual cascade TSDA, which was initiated by the target miRNA-21, like a molecular machine, and consumed the substrates and fuels, repeatedly used the target miRNA-21, and released a large number of reporter strands (RS). Subsequently, the released RS replaced SIG to prevent ZCIS QDs and N-CDs from sensitizing the electrode, which remarkably suppressed the photocurrent signal. The introduction of TSDA could produce high amplification capacity and specificity for the target miRNA-21 with advantages of simple primer design and mild reaction conditions. Impressively, with the cascade band gap arrangement for enhanced PEC performance and enzyme-free dual cascade TSDA for amplification capacity and specificity, the PEC biosensor exhibited excellent application in miRNA-21 analysis with a linear range from 1 pM to 100 nM and a low detection limit of 0.31 pM. This PEC biosensor retained good specificity, stability, and reproducibility and provided an effective method for PEC biosensor construction for microRNA. Moreover, the designed PEC biosensor was environmentally friendly, green manufactured, and self-powered and therefore compatible with the purpose of sustainable chemistry.

Affinity-Based Detection of Biomolecules Using Photo-Electrochemical Readout

“…The NPC-ZnO is also photoactive and thereby generated a signal-on response under visible light excitation. This creative design strategy enabled ultrasensitive miRNA detection with a limit-of-detection of 49 aM (linear range of 0.1 fM−10 nM), which is much lower than the previously reported photoelectrochemical miRNA detection bioassays (Wen and Ju, 2016; Chu et al, 2018).…”

“…When the DNA TET-CdTe QDs-MB complex was used as a signal probe, the PEC response (0.82 μA) was ~2.5-fold higher as compared to the PEC response based on the DNA TET-CdTe QDs complex alone (Figure 4A). In contrast to the previously discussed assays, the introduction of photoactive materials can also occur in the absence of the target analyte (Chu et al, 2018). In an assay of this type, the dsDNA capture probe contains a carboxyl-terminated ssDNA building block that is removed, through strand displacement, from the electrode upon target introduction.…”

“…Introduction of QDs as Photoactive species: (A) Schematic Diagrams of PEC Biosensor for miRNA-141 detection using DSN enzyme-assisted target cycling amplification strategy and DNA TET-CdTe QDs-MB complex [Reprinted from Li et al (2018a) with permission from American Chemical Society]. (B) Schematic illustration of the PEC detection of miRNA-21 by bringing photoactive N-doped carbon dots following hybridization of the target RNA [Reprinted from Chu et al (2018) with permission from American Chemical Society]. (C) Schematic representation of ultrasensitive insulin detection based on CdTe QD labels brought into proximity of CdS/TiO 2 /ITO electrode upon affinity-based binding of CdTe QD labeled insulin target [Reprinted from Wen and Ju (2016) with permission from American Chemical Society].…”

Enhancing the Sensitivity of Photoelectrochemical DNA Biosensing Using Plasmonic DNA Barcodes and Differential Signal Readout

“…Similarly, the addition of MEA as a surface blocker further decreased the charge transfer resistance by 43 %. Upon the hybridization of target DNA, the R ct increased by 110 %, which is attributed to increased steric hindrance between the redox species in the solution and the surface of the photoelectrode [48] . Introduction of the SAB resulted in a 33 % decrease in R ct , which is attributed to improved charge transfer kinetics due to the addition of Au NPs into the electrode film [49, 50] …”

Recent Applications of Carbon Nanomaterials for microRNA Electrochemical Sensing

“…[113,114] For instance, a PEC biosensor for miRNA-21 detection based on cosensitization of biocompatible CuInS 2 / ZnS QDs (ZCIS QDs) and N-doped CDs (N-CDs) coupled with dual cascade toehold-mediated strand displacement amplification (dual cascade TSDA) was developed by Chu et al (Figure 8). [115] In this sensor, TiO 2 /Au hybrid structure was utilized to immobilize double stranded DNA, which could capture glutathione stabilized ZCIS QDs and N-CDs. The original TiO 2 /Au/ ZCIS/N-CDs structure could form a cascade band gap arrangement, which improved PEC performance vividly.…”