Palindromic Molecular Beacon Based Z-Scheme BiOCl-Au-CdS Photoelectrochemical Biodetection

Abstract

This work presented an innovative and rationally engineered palindromic molecular beacon (PMB) based "Z-scheme" photoelectrochemical (PEC) biosensing protocol for the selective screening of kanamycin (Kana) through DNA hybridization-induced conformational conversion. Interestingly, the ingeniously designed PMB integrated the multifunctional elements including recognition region, primer-like palindromic fragment, and polymerization-nicking template. The cosensitized structures consisted of CdS quantum dot functionalized hairpin DNA2 (QD-HP2) and region-selectively deposited gold nanoparticles onto {001} facets of bismuth oxychloride (BiOCl-Au). Compared with BiOCl-Au alone, the attachment of CdS QDs onto BiOCl-Au (i.e., BiOCl-Au-CdS QDs) exhibited evidently enhanced photocurrent intensity thanks to the synergistic effect of Z-scheme BiOCl-Au-CdS QDs. After incubation with target Kana, Kana−aptamer binding could induce the exposure of PMB region for hairpin DNA1 (HP1). The exposed palindromic tails hybridized with each other (like a molecular machine) to consume the substrates (dNTPs) and fuels (enzyme) for the releasing of numerous nick fragments (Nick). The asgenerated nick fragments could specifically hybridize with the complementary region of QD-HP2, thus resulting in decreasing photocurrent because of the increasing spatial distance for electron transfer between two-type photosensitizers. Under optimum conditions, the PMB-based sensing system exhibited satisfying photocurrent responses toward target Kana within the working range from 50 to 5000 fM at a low detection limit of 29 fM. Impressively, the concept of a palindromic fragment-mediated primer-free biosensing strategy offers a new avenue for advanced development of efficient and convenient biodetection systems.

Applications of Catalytic Hairpin Assembly Reaction in Biosensing

“…The aptamer domain is released along with the conjugation between aptamer and target. With varied signal output platforms, the system signal can be delivered through indicators or coupled with another signal amplification method recovering DNAzyme, NPs, and HCR‐analogous isothermal amplification . Li et al extended the probe containing aptamers and metal ion‐dependent DNAzyme for small molecules .…”

An electrochemical aptasensor for lead ion detection based on catalytic hairpin assembly and porous carbon supported platinum as signal amplification

“…14, 15 Based on these unique properties, many electrochemical sensors based on aptamers have been fabricated for ultrasensitive detection of Pb 2+ . 16,17 In order to further amplify response signal and enhance the sensitivity, different signal amplication techniques including palindromic molecular beacon (PMB), 18 rolling circle amplication (RCA), 19 DNA walker, 20 hybridization chain reaction (HCR) 21 and catalytic hairpin assembly (CHA) 22 have attracted increasing attention. Among them, as isothermal nucleic acid amplication strategy, with the simple reaction conditions, high sensitivity and the low costs, CHA is powerful for amplifying and transducing signals at the terminus of nucleic acid amplication reactions, 23,24 and has been broadly applied in electrochemical sensing platforms.…”

An Electrochemical Sensor for the Detection of Cu2+ Based on Gold Nanoflowers‐modifed Electrode and DNAzyme Functionalized Au@MIL‐101 (Fe)

“…To ensure the sensitivity of the electrochemical sensor, various functional nanomaterials are usually employed for signal amplification [13][14][15]. As one of the research hotspots in recent years, metal-organic frameworks (MOFs) have been used in many fields, such as catalysis [16], supercapacitors [17], adsorption and separation [18], and sensing [19][20][21].…”