Design and optimizing gold nanoparticle-cDNA nanoprobes for aptamer-based lateral flow assay: Application to rapid detection of acetamiprid

Nanomaterials-based aptasensors for rapid detection and early warning of key food contaminants: A review

The frequent occurrence of food safety incidents has aroused public concern about food safety and key contaminants. Foodborne pathogen contamination, pesticide residues, heavy metal residues, and other food safety problems will significantly impact human health. Therefore, developing efficient and sensitive detection method to ensure food safety early warning is paramount. The aptamer-based sensor (aptasensor) is a novel analytical tool with strong targeting, high sensitivity, low cost, etc. It has been extensively utilized in the pharmaceutical industry, biomedicine, environmental engineering, food safety detection, and in other diverse fields. This work reviewed the latest research progress of aptasensors for food analysis and detection, mainly introducing their application in detecting various key food contaminants. Subsequently, the sensing mechanism and performance of aptasensors are discussed. Finally, the review will examine the challenges and opportunities related to aptasensors for detecting major contaminants in food, and advance implementation of aptasensors in food safety and detection.

Lateral flow assay for simultaneous detection of multiple mycotoxins using nanozyme to amplify signals

Co-contamination of multiple mycotoxins produces synergistic toxic effects, leading to more serious hazards. Therefore, the simple, rapid and accurate simultaneous detection of multiple mycotoxins is crucial. Herein, a three-channel aptamer-based lateral flow assay (Apt-LFA) was established for the detection of aflatoxin M1 (AFM1), aflatoxin B1 (AFB1) and ochratoxin A (OTA). The multi-channel Apt-LFA utilized gold‑iridium nanozyme to catalyze the chromogenic substrate, which effectively achieved signal amplification. Moreover, the positions and lengths of the complementary sequences were screened by changes in fluorescence intensity. After grayscale analysis, the semi-quantitative results showed that the detection limits of AFM1, AFB1 and OTA were 0.39 ng/mL, 0.36 ng/mL and 0.82 ng/mL. The recoveries of the multiplexed competitive sensors in complex matrices of real samples were 93.33%-97.01%, 95.72%-102.67%, and 106.88%-109.33%, respectively. In conclusion, the assembly principle of the three-channel Apt-LFA is simple, which can provide a new idea for the simultaneous detection of small molecule targets.

Signal amplification strategy based on target-controlled release of mediator for ultrasensitive self-powered biosensing of acetamiprid

Self-powered biosensors with high sensitivity have garnered significant interest for their potential applications in the realm of portable sensing. Herein, a self-powered biosensor with a novel signal amplification strategy was developed by integrating target-controlled release of mediator with an enzyme biofuel cell for the ultrasensitive detection of acetamiprid (ACE). Zeolitic imidazolate framework-67 was utilized as both a nanocontainer for capturing the electron mediator 2,2'-azidobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and a precursor for the synthesis of cobalt nanoparticles/nitrogen, sulfur-codoped carbon nanotubes (Co NPs/NS-CNTs), which were employed as the electrode material for constructing both the glucose oxidase-based bioanode and the laccase-based biocathode. The target analyte ACE can specifically bind to its aptamer, leading to the release of ABTS, which cyclically participates in the catalytic reaction of the biocathode, thereby amplifying the electrochemical signal. By leveraging the benefits of ABTS cyclic catalysis and the effective electrocatalysis of bioelectrodes based on Co NPs/NS-CNTs, the self-powered biosensor has a broad detection range of 0.1-1000 fM and a low detection limit of 25 aM toward ACE. The proposed signal amplification approach presents a promising strategy for enhancing sensitivity and enabling portable analysis in applications of food safety, environmental monitoring, and medical diagnostics.

Development of aptamer-based lateral flow devices for rapid detection of SARS-CoV-2 S protein and uncertainty assessment

The outbreak and spread of COVID-19 have highlighted the urgent need for early diagnosis of SARS-CoV-2. Nucleic acid testing as an authoritative tool, is cumbersome, time-consuming, and easy to cross-infect, while the available antibody self-testing kits are deficient in sensitivity and stability. In this study, we developed competitive aptamer-based lateral flow devices (Apt-LFDs) for the quantitative detection of SARS-CoV-2 spike (S) protein. Molecular docking simulation was used to analyze the active binding sites of the aptamer to S protein, guiding complementary DNA (cDNA) design. Then a highly efficient freezing strategy was applied for the conjugation of gold nanoparticles (AuNPs) and DNA probes. Under optimal conditions, the linear range of the constructed Apt-LFDs was 0.1-1 μg/mL, and the limit of detection (LOD) was 51.81 ng/mL. The cross-reactivity test and stability test of the Apt-LFDs showed good specificity and reliability. The Apt-LFDs had recoveries ranging from 89.45 % to 117.12 % in pharyngeal swabs. Notably, the uncertainty of the analytical result was evaluated using a "bottom-up" approach. At a 95 % confidence level, the uncertainty report of (453.37±54.86) ng/mL with k = 2 was yielded. Overall, this study provides an important reference for the convenient and reliable detection of virus proteins based on LFDs.

Combination of Capture-SELEX and Post-SELEX for procymidone-specific aptamer selection and broad-specificity aptamer discovery, and development of aptamer-based lateral flow assay

BACKGROUND

Due to its wide application, procymidone has become one of the pesticides with high detection rates in supervision and sampling. Therefore, it is necessary to establish a rapid and efficient method for the detection of procymidone. However, an important bottleneck restricting the development of rapid detection methods of procymidone is that its specific recognition elements are rarely reported. In this work, Capture-SELEX and post-SELEX were used in aptamer screening, and the obtained aptamers were used to construct an aptamer-based lateral flow assay (LFA).

RESULTS

Firstly, a specific aptamer Seq15 was obtained for procymidone by Capture-SELEX, and its dissociation constant (Kd) was 24.22 nM. Secondly, post-SELEX was used to analyze and modify Seq15 to improve its performance, and the Kd of the truncated sequence Seq15-2 was 21.28 nM. In addition to this, the broad-specificity aptamer Seq17-1 was obtained via post-SELEX. Seq17-1 could broadly recognize dicarboximide fungicides (procymidone, iprodione, chlozolinate, dimethachlon and vinclozolin) and their metabolic derivative (3,5-dichloroaniline). Finally, the specific aptamer-based LFA of procymidone was constructed, and the limit of detection (LOD) was 0.79 ng/mL. Meanwhile, the LODs of dicarboximide fungicides and their metabolic derivative were 0.62, 0.64, 0.71, 0.69, 0.64 and 0.66 ng/mL, respectively. The above LFAs were highly specific and stable, and had been successfully used for the detection of vegetable samples.

SIGNIFICANCE

Under the combination of Capture-SELEX and Post-SELEX, this study not only provides specific recognition elements for rapid detection of procymidone, but also provides new ideas for the discovery of broad-specificity aptamers. Combining broad-specificity primary detection and single-specificity quantification, a composite aptamer-based LFA detection platform has been developed, which significantly improves detection efficiency.

A comprehensive review of aptamer screening and application for lateral flow strip: Current status and future perspectives

The detection of biomarkers is of great significance for medical diagnosis, food safety, environmental monitoring, and agriculture. However, bio-detection technology at present often necessitates complex instruments, expensive reagents, specialized expertise, and prolonged procedures, making it challenging to fulfill the demand for rapid, sensitive, user-friendly, and economical testing. In contrast, lateral flow strip (LFS) technology offers simple, fast, and visually accessible detection modality, allowing real-time analysis of clinical specimens, thus finding widespread utility across various domains. Within the realm of LFS, the application of aptamers as molecular recognition probes presents distinct advantages over antibodies, including cost-effectiveness, smaller size, ease of synthesis, and chemical stability. In recent years, aptamer-based LFS has found extensive application in qualitative, semi-quantitative, and quantitative detection across food safety, environmental surveillance, clinical diagnostics, and other domains. This review provided a concise overview of different aptamer screening methodologies, selection strategies, underlying principles, and procedural, elucidating their respective advantages, limitations, and applications. Additionally, we summarized recent strategies and mechanisms for aptamer-based LFS, such as the sandwich and competitive methods. Furthermore, we classified LFSs constructed based on aptamers, considering the rapid advancements in this area, and discussed their applications in biological and chemical detection. Finally, we delved into the current challenges and future directions in the development of aptamer and aptamer-based LFS. Although this review was not thoroughly, it would serve as a valuable reference for understanding the research progress of aptamer-based LFS and aid in the development of new types of aptasensors.

Ultrasensitive Paper-Based Photoelectrochemical Biosensor for Acetamiprid Detection Enabled by Spin-State Manipulation and Polarity-Switching

Efficient carrier separation is vitally crucial to improving the detection sensitivity of photoelectrochemical (PEC) biosensors. Here, we developed a facile strategy to efficiently regulate the carrier separation efficiency of the photoactive matrix BiOI and In2S3 signal label functionalized paper chip by manipulation of electrons spin-state and rational design of electron transport pathways. The spin-dependent electronic structures of BiOI and In2S3 were regulated via enhanced electron-spin parallel alignment induced by an external magnetic field, markedly retarding carrier recombination and extending their lifetime. Simultaneously, with the progress of the target-induced catalytic hairpin assembly process, the transfer path of photogenerated carriers was changed, leading to a switch in photocurrent polarity from cathode to anode. This reversed electron transport pathway not only boosted the separation ability of photogenerated electrons but also eliminated false-positive and false-negative signals, thereby further improving the detection sensitivity. As a proof of concept, the well-designed magnetic field-stimulated paper-based PEC biosensor showed highly selectivity and sensitivity for acetamiprid assay with a wide linear range of 1 fM to 20 nM and an ultralow detection limit of 0.73 fM. This work develops a universal strategy for improving the sensitivity of biosensors and exhibits enormous potential in the fields of bioanalysis and clinical diagnosis.

Aptamer-modified paper-based analytical devices for the detection of food hazards: Emerging applications and future perspective

Food analysis plays a critical role in assessing human health risks and monitoring food quality and safety. Currently, there is a pressing need for a reliable, portable, and quick recognition element for point-of-care testing (POCT) to better serve the demands of on-site food analysis. Aptamer-modified paper-based analytical devices (Apt-PADs) have excellent characteristics of high portability, high sensitivity, high specificity, and on-site detection, which have been widely used and concerned in the field of food safety. The article reviews the basic components and working principles of Apt-PADs, and introduces their representative applications detecting food hazards. Finally, the advantages, challenges, and future directions of Apt-PADs-based sensing performance are discussed, to provide new directions and insights for researchers to select appropriate Apt-PADs according to specific applications.

"Four-In-One" Multifunctional Dandelion-Like Gold@platinum Nanoparticles-Driven Multimodal Lateral Flow Immunoassay

The traditional lateral flow immunoassay (LFIA) with a single signal output mode may encounter challenges such as low sensitivity, poor detection range, and susceptibility to external interferences. These limitations hinder its ability to meet the growing demand for advanced LFIA. To address these issues, the rational development of multifunctional labels for multimodal LFIA emerges as a promising strategy. Herein, this study reports a multimodal LFIA using "four-in-one" multifunctional dandelion-like gold@platinum nanoparticles (MDGP). The inherent properties of MDGP, such as the broad absorption spectrum, porous dandelion-like nanostructure, and bimetallic composition with gold and platinum, endow them with capacities in dual spectral-overlapped fluorescence quenching, optical readout, catalytic activity, and photothermal effect. Benefiting from their multifunctional properties, the MDGP-LFIA enables multimodal outputs including fluorescent, colorimetric, and photothermal signals. This multimodal MDGP-LFIA allows for the detection of acetamiprid at a range of 0.01-50 ng mL-1, with the lowest qualitative and quantitative detection results of 0.5 and 0.008 ng mL-1, respectively, significantly better than the traditional gold nanoparticles-based LFIA. The diversity, complementarity, and synergistic effect of integrated output signals in this multimodal MDGP-LFIA improve the flexibility, practicability, and accuracy of detection, holding great promise as a point-of-care testing platform in versatile application scenarios.

Advances in Aptamer-Based Conjugate Recognition Techniques for the Detection of Small Molecules in Food

Small molecules are significant risk factors for causing food safety issues, posing serious threats to human health. Sensitive screening for hazards is beneficial for enhancing public security. However, traditional detection methods are unable to meet the requirements for the field screening of small molecules. Therefore, it is necessary to develop applicable methods with high levels of sensitivity and specificity to identify the small molecules. Aptamers are short-chain nucleic acids that can specifically bind to small molecules. By utilizing aptamers to enhance the performance of recognition technology, it is possible to achieve high selectivity and sensitivity levels when detecting small molecules. There have been several varieties of aptamer target recognition techniques developed to improve the ability to detect small molecules in recent years. This review focuses on the principles of detection platforms, classifies the conjugating methods between small molecules and aptamers, summarizes advancements in aptamer-based conjugate recognition techniques for the detection of small molecules in food, and seeks to provide emerging powerful tools in the field of point-of-care diagnostics.

Stepwise Au decoration-assisted double signal amplified lateral flow strip for ultrasensitive detection of morphine in fingerprint sweat

Point-of-care testing (POCT) of morphine (MOP) without invasion of privacy is of critical importance for law-enforcement departments to realize on-site rapid screening. In this study, ultrasensitive and non-invasive screening of MOP residues in the fingerprint sweat was easily realized by stepwise Au decoration-assisted double signal amplification and antibody-saving strategies on lateral flow strip (LFS). The construction of LFS was not intrinsically changed compared with traditional LFS except the labeling material on conjugation pad for enhanced signal reporting. The gold nanoparticle-seeded SiO2 was adopted as the labeling materials in place of traditional gold nanoparticles, which acted as the first-round signal amplification and ready for second-round gold deposition-assisted amplification. And the second-round amplification could be completed in just 10 s, which did not alter the intrinsic simplicity of LFS for rapid and on-site screening. With the designed signal amplification principle of LFS, target MOP in the fingerprint sweat can be effectively transferred to the LFS for analysis without invasion of privacy. As low as 0.5 pg MOP in fingerprint sweat can be visually judged with this double signal amplified LFS, the sensitivity of which has been improved at least 10-fold compared with traditional Au-labeled LFS, guaranteeing accurate screening of trace MOP in the fingerprint sweat. Of great importance, the consumption of valuable antibody can be reduced to just 1/20, which greatly reduces the cost of high-throughput screening. This stepwise Au decoration-assisted double signal amplified LFS holds great potential in the ultrasensitive screening of trace analytes in various fields and further widens the application scope of lateral flow strips.

CRISPR/Cas9-based point-of-care lateral flow biosensor with improved performance for rapid and robust detection of Mycoplasma pneumonia

Screening of acute respiratory infections causes serious challenges in urgent point-of-care scenarios where conventional methods are impractical and alternative techniques suffer from low accuracy, poor robustness, and reliance on sophisticated instruments. As an improvement to this paradigm, we report a point-of-care lateral flow biosensor (LFB) based on the recognition property of clustered regularly interspaced short palindromic repeats (CRISPR)/associated protein 9 (Cas9) and apply it to the detection of Mycoplasma pneumoniae (M. pneumoniae). The designed biosensor employs CRISPR/Cas9 for secondary recognition after preamplification of target gene using specific primer set, avoiding false positives caused by nontarget factors. The high amplification efficiency and low applicable temperatures of recombinase polymerase amplification brings the detection limit of the biosensor to 3 copies even at a preamplification temperature of 25 °C. Its practical application is further demonstrated with 100% accuracy by testing with 43 M. pneumoniae-infected specimens and 80 uninfected specimens. Additionally, the entire detection, including pretreatment, preamplification, CRISPR/Cas9 recognition, and visual analysis, can be completed in 30 min. Featured with the combination of CRISPR/Cas9 and LFB, the biosensor we developed herein ensures excellent convenience, accuracy, and robustness, which endows promising point-of-care screening potential for infectious pathogens.

In silico selection of an aptamer for the design of aptamer-modified magnetic beads bearing ferrocene co-immobilized label for capacitive detection of acetamiprid

In silico evaluation of aptamer/target interactions can facilitate the development of efficient biosensor with high specificity and affinity. In this work, we present in silico, i.e. structural similarity, molecular docking and molecular dynamics selection of the aptamer with sufficient binding properties for acetamiprid (ACE), a nicotine-like pesticide, and its use to design aptamer-modified magnetic beads bearing ferrocene co-immobilized label for capacitive detection of ACE. Taking advantages of the aptamer higher stability and binding affinity, the specific properties of magnetic beads and the redox properties of ferrocene moiety, the developed aptasensor showed promising analytical performances for ACE detection, using electrochemical capacitance spectroscopy, with a linear response ranging from 1 fM to 100 pM and a limit of detection of 0.94 fM (S/N = 3). Furthermore, it was successfully applied to detect ACE in fortified tomatoes samples, proving a promising approach for routine detection of pesticide in real agricultural samples.

A combined UV-visible with fluorescence detection method based on an unlabeled aptamer and AuNPs for the sensitive detection of acetamiprid

A simple spectral method with a wider detection range is proposed for the detection of acetamiprid.

A simple mesoporous silica Nanoparticle-based aptamers SERS sensor for the detection of acetamiprid

In this study, we developed a novel, rapid, simple, and sensitive nano sensor based on the controlled release of 4-Aminothiophenol (4-ATP) signal molecules from aptamers (Apts) modified aminated mesoporous silica nanoparticles (MSNs-NH₂) for the quantitative detection of acetamiprid (ACE). Firstly, we synthesized the positively charged MSNs-NH₂ by one-pot method, then loaded 4-ATP signal molecules into the pore, and finally electrostatically adsorbed the Apts onto the MSNs-NH₂, which acts as a gate to control the release of signal molecules. When ACE is added to the system, ACE preferentially and specifically binds to Apts, so the gate opens and 4-ATP signal molecules are released from the pore. Meanwhile, the silver-loaded mesoporous silica nanoparticles (Ag@SiO₂) were prepared by one-pot method as surface-enhanced Raman spectroscopy (SERS) substrate to amplify the signal. The intensity of 4-ATP signal molecules at 1433 cm^-1 position was observed to has a linear relationship with the concentration of ACE by SERS detection. Under the optimized detection conditions, a linear correlation was observed in the range of 5-60 ng/mL (R² = 0.99749), and the limit of detection (LOD) was 2.66 ng/mL. The method has high sensitivity, good selectivity and reproducibility, and can be used for actual sample analysis with the recovery rate of 96.24-103.6 %. This study provides a reference for the rapid and convenient detection of ACE in agricultural products.

Fluorescent aptamer-modified mesoporous silica nanoparticles for quantitative acetamiprid detection

Acetamiprid (ACE) is widely used to control aphids, brown planthoppers, and other pests in agricultural production. However, ACE is difficult to degrade in the environment, resulting in excessive residue, which causes acute and chronic toxicity to human beings and non-target organisms. Therefore, the development of a rapid, convenient, and highly sensitive method to quantify ACE is essential. In this study, aminated mesoporous silica nanoparticles (MSNs-NH₂) were synthesized by one-pot method, and 6-carboxyl fluorescein modified aptamers (FAM-Apt) of ACE were adsorbed on the surface of MSNs-NH₂ by electrostatic interaction. Finally, a simple and sensitive fluorescence analysis method for the rapid detection of ACE was established. In the absence of ACE, the negatively charged FAM-Apt was electrostatically bound to the positively charged MSNs-NH₂, followed by centrifugation to precipitate MSNs-NH₂@FAM-Apt, and no fluorescent signal was detected in the supernatant. In the presence of ACE, the specific combination of FAM-Apt with ACE was greater than its electrostatic interaction with MSNs-NH₂, so that FAM-Apt was separated from MSNs-NH₂, and the supernatant had strong fluorescence signal after centrifugation. For ACE detection, the linear concentration range was 50-1100 ng/mL, and the detection limit (LOD) was 30.26 ng/mL. The method exhibited high sensitivity, selectivity and reproducibility, which is suitable for practical sample analysis and provides guidance for rapid detection of pesticide residues.

Nucleic Acid Aptamers for Pesticides, Toxins, and Biomarkers in Agriculture

Nucleic acid aptamers are short single-stranded DNA/RNA (ssDNA/RNA) oligonucleotides that can selectively bind to the targets. They are widely used in medicine, biosensing, and diagnostic assay. They have also been identified and extensively used for various targets in agriculture. In this review we summarize the progress of nucleic acid aptamers on pesticides (herbicides, insecticides, and fungicides), toxins, specific biomarkers of crops, and plant growth regulators in agricultural field in recent years. The basic process of aptamer selection, the already identified DNA/RNA aptamers and the aptasensors are discussed. We also discuss the future perspectives and the challenges for aptamer development in agriculture.

Accelerated CRISPR/Cas12a-based small molecule detection using bivalent aptamer

CRISPR/Cas holds great promise for biosensing applications, however, restricted to nucleic acid targets. Here, we broaden the sensing target of CRISPR/Cas to small molecules via integrating a bivalent aptamer as a recognition component. Using adenosine 5'-triphosphate (ATP) as a model molecule, we found that a bivalent aptamer we selected could shorten the binding time between the aptamer and ATP from 30 min to 3 min, thus dramatically accelerating the detection of ATP. The accelerated bivalent aptamer binding to ATP was mainly ascribed to the extended conformation of the aptamer, which was stabilized through linking with a 5 T bases connector on specific loops of the monovalent aptamer. To facilitate on-site detection, we integrated lateral flow assay (LFA) with the CRISPR/Cas sensing strategy (termed BA-CASLFA) to serve as a visual readout of the presence of ATP. In addition, in the CASLFA platform, due to the unique characteristics of LFA, the thermal step of Cas12a inactivation can be omitted. The BA-CASLFA could output a colorimetric "TURN ON" signal for ATP within 26 min, which could be easily discriminated by the naked eye and sensitively quantified by the portable reader. Furthermore, we showed the versatility of BA-CASLFA for detecting kanamycin using a kanamycin bivalent aptamer obtained through the same design as the ATP bivalent aptamer. Therefore, this strategy is amenable to serve as a general sensing strategy for small molecular targets. The above work opened a new way in developing CRISPR-based on-site sensors for clinic diagnosis, food safety, and environmental analysis.

Determination of Acetamiprid Residues in Vegetables by Indirect Competitive Chemiluminescence Enzyme Immunoassay

Acetamiprid (ACE) is widely used in various vegetables to control pests, resulting in residues and posing a threat to human health. For the rapid detection of ACE residues in vegetables, an indirect competitive chemiluminescence enzyme immunoassay (ic-CLEIA) was established. The optimized experimental parameters were as follows: the concentrations of coating antigen (ACE-BSA) and anti-ACE monoclonal antibody were 0.4 and 0.6 µg/mL, respectively; the pre-incubation time of anti-ACE monoclonal antibody and ACE (sample) solution was 30 min; the dilution ratio of goat anti-mouse-HRP antibody was 1:2500; and the reaction time of chemiluminescence was 20 min. The half-maximum inhibition concentration (IC₅₀), the detection range (IC₁₀–IC₉₀), and the detection limit (LOD, IC₁₀) of the ic-CLEIA were 10.24, 0.70–96.31, and 0.70 ng/mL, respectively. The cross-reactivity rates of four neonicotinoid structural analogues (nitenpyram, thiacloprid, thiamethoxam, and clothianidin) were all less than 10%, showing good specificity. The average recovery rates in Chinese cabbage and cucumber were 82.7–112.2%, with the coefficient of variation (CV) lower than 9.19%, which was highly correlated with the results of high-performance liquid chromatography (HPLC). The established ic-CLEIA has the advantages of simple pretreatment and detection process, good sensitivity and accuracy, and can meet the needs of rapid screening of ACE residues in vegetables.

Non-thiolated nucleic acid functionalized gold nanoparticle-based aptamer lateral flow assay for rapid detection of kanamycin

A novel Apt-LFA has been established for kanamycin based on non-thiolated nucleic acid-modified colloidal gold nanoprobe (AuNPs@polyA-DNA). The improvement in nucleic acid hybridization speed and efficiency was verified by modifying AuNPs with polyA-DNA strands instead of thiolated oligonucleotides (SH-DNA) strands. Moreover, the AuNPs@polyA-DNA was explored to apply in an Apt-LFA. The experimental factors including the concentration of the aptamer, the concentration of SA-DNA_T conjugate, the incubation time, and temperature were carefully investigated. In addition, the kanamycin aptamer was modified by extending several bases at its end to modulate the hybridization complementary strand, which was found to significantly improve the performance of Apt-LFA. Under optimal experimental conditions, the Apt-LFA can detect kanamycin in honey with a LOD of 250 ng mL^-1 by the naked eyes. A linear range of 50-1250 ng mL^-1 was obtained with a LOD of 15 ng mL^-1 in honey by a portable reader. The Apt-LFA was successfully applied to the detection of kanamycin in honey with recoveries of 95.1-105.2%.