Catalytic hairpin assembly assisted target-dependent DNAzyme nanosystem coupled with AgPt@Thi for the detection of lead ion

A novel and universal dual-channel signal amplification aptasensing platform for ultrasensitive and rapid detection of cardiac biomarkers based on the mutual regulation of bimetallic organic framework and silver nanoclusters

Cardiac troponin I (cTnI) is a key biomarker for diagnosing myocardial infarction caused by myocardial injury. The accurate and rapid monitoring of ultralow levels of cTnI is crucial for early diagnosis and risk warning of myocardial injury. Herein, a novel dual-channel signal amplification aptasensor for cTnI detection was developed utilizing the mutual regulation of bimetallic organic framework (MOFs) and silver nanoclusters (AgNCs) with the assistance of catalytic hairpin assembly (CHA). Rationally designed triple-helix molecular switch (THMS) and two hairpin probes (HP1 and HP2) containing AgNCs and a guanine-rich DNA sequence could be adsorbed onto the surface of bimetallic Cu, Mo-MOFs, enhancing the catalytic activity and reducing the fluorescence signal. The target cTnI specifically binds to the aptamer in the THMS, releasing the signal transduction probe which triggers CHA to desorb HP1-AgNCs and HP2, thereby restoring the fluorescence and decreasing the catalytic activity as well as initiating cycling. This enables dual-channel fluorescence and colorimetric detection of cTnI. The linear fluorescence and colorimetric response ranges were 0.001-20 ng/mL with LOD of 0.48 pg/mL and 0.001-10 ng/mL with LOD of 0.69 pg/mL, respectively. The aptasensor significantly increases the detection sensitivity and reduces the time required for cTnI detection in human serum, with excellent anti-interference capability. Moreover, the aptasensor shows promise for the construction of universal dual-channel aptasensors for multiple targets by altering the aptamer in THMS.

Fluorescent biosensor for lead ion detection based on GR-5 DNAzyme and self-hybridization chain reaction

BACKGROUND

Lead ion (Pb2+) is a typical heavy metal pollutant, and the water and food contaminated by lead may pose a potential threat to the environment and human health. In the natural environment, it can accumulate in soil and water, affecting the entire food chain. For human health, even if the Pb2+ content is very low, it can cause a series of adverse health effects. In order to effectively address the issue of lead pollution, it is particularly important to develop highly sensitive and selective Pb2+ detection technology.

RESULTS

In this study, we designed a single-hairpin based self-hybridization chain reaction (SHCR) system for Pb2+ detection based on GR-5 DNAzyme. Compared with the traditional hybridization chain reaction (HCR) which requires two hairpins, this strategy only needs one hairpin probe, this design not only reduces the experimental cost, but also simplifies the sequence design and experimental operation. Once Pb2+ was added in the system, GR-5 DNAzyme can be actived and then a trigger DNA was released to trigger the SHCR reaction, thereby a signal-amplified fluorescent biosensor for Pb2+ detection was developed, which exhibited a good linear range from 100 to 500 nM with a low detection limit of 24.8 nM, and has been successfully applied to the determination of Pb2+ in environmental water and Chinese Baijiu.

SIGNIFICANCE

This simple, sensitive, and selective Pb2+ detection system demonstrates significant potential for a wide range of practical applications in both environment and food monitoring. In addition to its specific application for Pb2+ detection, by introducing different DNAzymes, this SHCR system can be applied for the detection of other heavy metal ions.

An Electrochemical Sensor for Detection of Lead (II) Ions Using Biochar of Spent Coffee Grounds Modified by TiO2 Nanoparticles

Toxic heavy metal ions, such as lead ions, significantly threaten human health and the environment. This work introduces a novel method for the simple and sensitive detection of lead ions based on biochar-loaded titanium dioxide nanoparticles (BC@TiO2NPs) nanocomposites. Eco-friendly biochar samples were prepared from spent coffee grounds (500 °C, 1 h) that were chemically activated with TiO2 nanoparticles (150 °C, 24 h) to improve their conductivity. Structural characterizations showed that BC@TiO2NPs have a porous structure. The BC@TiO2NPs material was evaluated for lead ion determination by assembling glassy carbon electrodes. Under optimal conditions, the sensor was immersed in a solution containing the analyte (0.1 M NaAc-HAc buffer, pH = 4.5) for the detection of lead ions via differential pulse voltammetry. A linear dynamic range from 1 pM to 10 μMwas achieved, with a detection limit of 0.6268 pM. Additionally, the analyte was determined in tap water samples, and a satisfactory recovery rate was achieved.

A novel dual-mode aptasensor based on a multiple amplification system for ultrasensitive detection of lead ions using fluorescence and surface-enhanced Raman spectroscopy

In this work, we develop a dual recycling amplification aptasensor for sensitive and rapid detection of lead ions (Pb2+) using fluorescence and surface-enhanced Raman scattering (FL-SERS). The aptasensor allows targeted cleavage of substrates through specifically binding with the Pb2+-dependent aptamer (M-PS2.M). Ultrasensitive detection of trace Pb2+ has been achieved using an enzyme-free nonlinear hybridization chain reaction (HCR) and the FL-SERS technique. The lower limit of detection (LOD = 3σ/k) is 0.115 pM in FL mode and 1.261 fM in SERS mode. The aptasensor is characterized by high reliability and specificity, among other things, to distinguish Pb2+ from other metal ions. In addition, the aptasensor can detect Pb2+ in actual water with good recovery. Compared with the single-mode aptasensor, the dual-mode aptasensor is characterized by high reliability, an extensive detection range, and high specificity.

Nanomaterials-based aptasensors: An efficient detection tool for heavy-metal and metalloid ions in environmental and biological samples

In light of potential risks of heavy metal exposure, diverse aptasensors have been developed through the combination of aptamers with nanomaterials for the timely and efficient detection of metals in environmental and biological matrices. Aptamer-based sensors can benefit from multiple merits such as heightened sensitivity, facile production, uncomplicated operation, exceptional specificity, enhanced stability, low immunogenicity, and cost-effectiveness. This review highlights the detection capabilities of nanomaterial-based aptasensors for heavy-metal and metalloid ions based on their performance in terms of the basic quality assurance parameters (e.g., limit of detection, linear dynamic range, and response time). Out of covered studies, dendrimer/CdTe@CdS QDs-based ECL aptasensor was found as the most sensitive option with an LOD of 2.0 aM (atto-molar: 10-18 M) detection for Hg2+. The existing challenges in the nanomaterial-based aptasensors and their scientific solutions are also discussed.

Concatenated dynamic DNA network modulated SERS aptasensor based on gold-magnetic nanochains and Au@Ag nanoparticles for enzyme-free amplification analysis of tetracycline

Tetracycline (TC) poses a great threat to food and environmental safety due to its misuse in animal husbandry and aquaculture. Therefore, an efficient analytical method is needed for the detection of TC to prevent possible hazards. Herein, a cascade amplification SERS aptasensor for sensitive determination of TC was constructed based on aptamer, enzyme-free DNA circuits, and SERS technology. The capture probe and signal probe were obtained by binding DNA hairpins H1 and H2 to the prepared Fe₃O₄@hollow-TiO₂/Au nanochains (Fe₃O₄@h-TiO₂/Au NCs) and Au@4-MBA@Ag nanoparticles, respectively. The dual amplification of EDC-CHA circuits significantly facilitated the sensitivity of the aptasensor. Additionally, the introduction of Fe₃O₄ simplified the operation of the sensing platform due to its superb magnetic capability. Under optimal conditions, the developed aptasensor exhibited a distinct linear response to TC with a low limit of detection of 15.91 pg mL^-1. Furthermore, the proposed cascaded amplification sensing strategy exhibited excellent specificity and storage stability, and its practicability and reliability were verified by TC detection of real samples. This study provides a promising idea for the development of specific and sensitive signal amplification analysis platforms in the field of food safety.

A colloidal gold test strip based on catalytic hairpin assembly for the clinical detection of influenza a virus nucleic acid

Influenza A epidemics, which occur annually in varying degrees worldwide, is a global challenge to healthcare facilities owing to several limitations of the current detection methods. Therefore, the development of a rapid, convenient, and economical method for the early diagnosis of influenza A will aid clinical treatment and epidemic control. Currently, most of the commonly used clinical rapid tests utilize colloidal gold test strips that detect specific influenza virus antigens but are limited by low sensitivity. Therefore, this study combined catalytic hairpin assembly (CHA) with colloidal gold immunochromatographic assay (GICA) to develop a highly sensitive and visual CHA-GICA test strip. Clinical sample analysis revealed that the sensitivity of the assay was 81.8% and 74% under optimal (35 °C) and room temperature (25 °C) conditions, respectively. In conclusion, this study developed a rapid nucleic acid assay for detecting influenza A virus with high sensitivity and specificity, which can improve the clinical detection of influenza A.

Biosensors based on functional nucleic acids and isothermal amplification techniques

In the past few years, with the in-depth research of functional nucleic acids and isothermal amplification techniques, their applications in the field of biosensing have attracted great interest. Since functional nucleic acids have excellent flexibility and convenience in their structural design, they have significant advantages as recognition elements in biosensing. At the same time, isothermal amplification techniques have higher amplification efficiency, so the combination of functional nucleic acids and isothermal amplification techniques can greatly promote the widespread application of biosensors. For the purpose of further improving the performance of biosensors, this review introduces several widely used functional nucleic acids and isothermal amplification techniques, as well as their classification, basic principles, application characteristics, and summarizes their important applications in the field of biosensing. We hope to provide some references for the design and construction of new tactics to enhance the detection sensitivity and detection range of biosensing.

Detection of Hepatitis C virus RNA using a novel hybridization chain reaction method that competitively dampens cascade amplification

The hybridization chain reaction (HCR) is widely used for biosensing. However, HCR does not provide the required sensitivity. In this study, we reported a method to improve the sensitivity of HCR by dampening the cascade amplification. First, we designed a biosensor based on HCR, and an initiator DNA was used to trigger the cascade amplification. Optimization of the reaction was then performed, and the results showed that the limit of detection (LOD) for the initiator DNA was about 2.5 nM. Second, we designed a series of inhibitory DNAs to dampen the HCR cascade amplification, and DNA dampeners (50 nM) were applied in the presence of the DNA initiator (50 nM). One of the DNA dampeners (D5) showed the best inhibitory efficiency of greater than 80%. This was further applied at concentrations ranging from 0 nM to 10 nM to prohibit the HCR amplification caused by a 2.5 nM initiator DNA (the limit of detection for this initiator DNA). The results showed that 0.156 nM of D5 could significantly inhibit the signal amplification (p<0.05). Additionally, the limit of detection for the dampener D5 was 16 times lower than that for the initiator DNA. Based on this detection method, we achieved a detection limit as low as 0.625 nM for HCV-RNAs. In summary, we developed a novel method with improved sensitivity to detect the target designed to prohibit the HCR cascade. Overall, this method could be used to qualitatively detect the presence of single-stranded DNA/RNA.