A label–free GR–5DNAzyme sensor for lead ions detection based on nanoporous gold and anionic intercalator

DNAzyme-based cascade signal amplification strategy for highly sensitive detection of lead ions in the environment

Lead ions are one of many common environmental pollutants, that can cause posing a serious threat to people's health, thus, their efficient and sensitive detection is important. We propose a cascade signal amplification sensor using a DNAzyme-based strand displacement amplification (SDA) and hybridization chain reaction (HCR) for the high-sensitivity detection of Pb²⁺. In the demonstrated sensor system, the target metal ion can activate DNAzyme to cause a strand displacement reaction. Under the synergistic action of polymerase and nickase, large numbers of DNA strands are generated that can initiate HCR. The subsequent HCR can restore the fluorescence intensity of the FAM quenched for the fluorescence resonance energy transfer effect, which exhibits a strong fluorescence signal. The DNAzyme-based sensor allowed the detection of Pb²⁺ down to 16.8 pM and resulted in a good dynamic line relationship ranging from 50 pM to 500 nM, and the biosensor also showed good selectivity. Furthermore, we confirmed that the proposed sensor can still detect lead ions in complex environments such as lake water, milk, and serum. We believe these findings will provide new ideas for the detection of toxic elements ions in the environment and food.

Biosensing with DNAzymes

This article provides a comprehensive review of biosensing with DNAzymes, providing an overview of different sensing applications while highlighting major progress and seminal contributions to the field of portable biosensor devices and point-of-care diagnostics. Specifically, the field of functional nucleic acids is introduced, with a specific focus on DNAzymes. The incorporation of DNAzymes into bioassays is then described, followed by a detailed overview of recent advances in the development of in vivo sensing platforms and portable sensors incorporating DNAzymes for molecular recognition. Finally, a critical perspective on the field, and a summary of where DNAzyme-based devices may make the biggest impact are provided.

Bifunctional cyclomatrix polyphosphazene-based hybrid with abundant decorating groups: Synthesis and application as efficient electrochemical Pb(II) probe and methylene blue absorbent

HYPOTHESIS

The construction of novel functional cyclomatrix polyphosphazenes (CPPs) hybrid, which with diverse decorating groups, is a challenging task due to the structural limitation of available reaction substrates (phenols and amines).

EXPERIMENTS

Herein, a phenolic hydroxyl (OH) modified ployamide derivative (P2) was successfully prepared via novel benzoxazine-isocyanide chemistry (BIC). A kind of CPP hybrid (P3), which with abundant functional groups (amide, tertiary amine, benzoxazine and phenolic hydroxyl) was prepared subsequently by the condensation between P2 and hexachlorocyclotriphosphazene (HCCP). Chemical structure, elemental composition, morphology, porous properties and crystallinity of P3 were systematically analyzed here. The electrochemical detection of lead ion (Pb²⁺) was realized by using P3-modified glassy carbon electrode (GCE/Nafion/P3) as the working electrode. Besides this, given the unique chemical structure and morphology of P3, the selective adsorption of methylene blue (MB) by P3 was also studied here.

FINDINGS

Experimental results indicated that that P3 can act as bifunctional hybrid material to solve environmental issues.

The synthesis and application of (E)-N′-(benzo[d]dioxol-5-ylmethylene)-4-methyl-benzenesulfonohydrazide for the detection of carcinogenic lead

A sensitive cationic sensor was developed by BDMMBSH onto GCE with 5% Nafion using electrochemical method, which was validated with the selective determination of Pb²⁺ in spiked samples and found satisfactory results.

A "turn-off" SERS aptasensor based DNAzyme-gold nanorod for ultrasensitive lead ion detection

It is great significance to precisely monitor lead (II) ions (Pb²⁺) for environment protection and human health monitoring. We designed a sensitive detection strategy for sensitive and selective determination of Pb²⁺, based on a Pb²⁺-specific DNAzyme as the catalytic unit, Cy3-labeled DNA modified gold nanorods (AuNRs) as SERS reporter. Firstly, AuNRs surface were employed as a platform for the immobilization of thiolated probe DNA, and then hybridized with DNAzyme catalytic beacons. By taking advantage of DNAzyme digest, a molecular beacon, causes a "turn-off" SERS signal by disrupting the labeled probes. Under the optical conditions, the DNAzyme-AuNRs sensor system exhibited high sensitivity, acceptable stability and reproducibility with a wide linear range from 0.5 to 100 nM (R² = 0.9973), and an ultra-low detection limit of 0.01 nM. The proposed strategy has additional advantages of being less time-consuming, low-cost and remote query, and avoids the interference of some metals such as Fe³⁺, Cd²⁺, Ba²⁺, Cu²⁺, Zn²⁺. The SERS biosensor system has been successfully applied for detecting Pb²⁺ in real samples with a satisfactory result. The result indicated that the proposed sensing strategy not only enriches SERS platform of monitoring Pb²⁺ but also exhibits potential for the point-of-care diagnostic application of the clinical screening in complicated biological samples.

A review of the advanced developments of electrochemical sensors for the detection of toxic and bioactive molecules

The recent developments made regarding the novel, cost-effective, and environmentally friendly nanocatalysts for the electrochemical sensing of biomolecules, pesticides, nitro compounds and heavy metal ions are discussed in this review article.

A label-free aptasensor for ultrasensitive Pb2+ detection based on electrochemiluminescence resonance energy transfer between carbon nitride nanofibers and Ru(phen)32

A label-free aptasensor was developed for ultrasensitive detection of Pb²⁺ based on electrochemiluminescence resonance energy transfer (ECL-RET) from graphitic carbon nitride nanofibers (CNNFs) to Ru(phen)₃²⁺. The CNNFs synthesized via a facile two-step hydrolysis-electrolysis strategy showed intense and stable ECL signal by taking advantages of amplifying and stabilizing effect of carbon nanotubes and Au nanoparticles. After the specific hybridation between capture DNA and Pb²⁺ specific aptamer, Ru(phen)₃²⁺ could be captured onto CNNFs modified electrode by effectively intercalating into the grooves of double-strand DNA, thus triggering the ECL-RET and leading to highly enhanced ECL intensity. The presence of Pb²⁺ would result in the detachment of Ru(phen)₃²⁺ and then the inhibition of ECL-RET. Then Pb²⁺ concentration could be quantified based on ECL change before and after introduction of Pb²⁺. The target recycling based on exonuclease I (Exo I) mediated digestion of Pb²⁺-aptamer complex was implemented to further improve the sensitivity. These synergistic amplification strategies enabled the aptasensor to be ultrasensitive for Pb²⁺ determination with a detection limit of 0.04 pM. The proposed probe was utilized to analyze environmental samples with satisfactory results.