A highly sensitive fluorescence biosensor for aflatoxins B1 detection based on polydiacetylene liposomes combined with exonuclease III-assisted recycling amplification.

A fluorescence biosensor for determination of aflatoxin B1 (AFB1) based on polydiacetylene (PDA) liposomes and exonuclease III (EXO III)-assisted recycling amplification was developed. The AFB1 aptamer partially hybridizes with complementary DNA (cDNA), which is released upon recognition of AFB1 by the aptamer. Subsequently, the cDNA hybridizes with hairpin H to form double-stranded DNA that undergoes digestion by EXO III, resulting in the cyclic release of cDNA and generation of capture DNA for further reaction. The capture DNA then hybridizes with probe modified on PDA liposomes, leading to aggregation of liposomes and subsequent fluorescence production. This strategy exhibited a limit of detection of 0.18 ng/mL within the linear range 1-100 ng/mL with a determination coefficient > 0.99. The recovery ranged from 92.81 to 106.45%, with relative standard deviations (RSD) between 1.73 and 4.26%, for corn, brown rice, peanut butter, and wheat samples. The stability, accuracy, and specificity of the method demonstrated the applicability for real sample analysis.

An integrated liposome-based microfluidic strategy for rapid colorimetric analysis: A case study of microRNA-21 detection.

In this study, a novel integrated liposome-based microfluidic platform combined with a smartphone was designed for the rapid colorimetric detection of microRNA-21 (miRNA-21) in real samples. The flowing surface-functionalized liposomes were first captured by nucleic acid-functionalized Au nanoparticles in the microfluidic chip. In the presence of miRNA-21, the DNA strand modified on the surface of Au nanoparticles hybridized with the target to form double-stranded products and was cleaved by duplex-specific nuclease (DSN) enzyme, causing the liposomes to be re-released. Then, as the liposomes in the colorimetric module were lysed and the "cellular" contents were released, a step-by-step "glucose-glucose oxidase-3,3',5,5'-tetramethylbenzidine (TMB)" colorimetric reaction process catalyzed by the G-quadruplex/hemin was triggered. The grayscale values were recorded and recognized by the smartphone camera for miRNA-21 analysis. The advantages of the present strategy included the portability of smartphone-based colorimetric assay, the encapsulation and transport of reactants by liposomes and the low solvent usage of microfluidic chip. Under optimal conditions, this assay exhibited a wide linear range from 1 pM to 1 nM (r2 = 0.9981), and the limit of detection of miRNA-21 was as low as 0.27 pM. Moreover, the high specificity of this strategy allowed its successful application to the rapid analysis of miRNA-21 in real blood serum samples of people with type 2 diabetes.

Sensitive fluorescence detection based on dimeric G-quadruplex combined with enzyme-assisted solid-phase microextraction of streptomycin in honey.

Streptomycin (STR), an aminoglycoside antibiotic with the potential to persist in honey and other food products, may induce allergy, toxicity and antibiotic resistance in humans. In this study, we developed a solid-phase microextraction (SPME) biosensor based on a quartz rod that was modified with double-stranded DNA structures consisting of partially complementary G-rich base DNA strand and STR aptamer. The STR isolated by SPME initially bound to the aptamer. Then the remaining double-stranded DNA structures were cleaved by the Nt.BstNBI enzyme, resulting in release of G-quadruplex dimers. The latter formed a complex with thioflain T fluorescent dye, resulting in an amplified fluorescence response. The method exhibited high sensitivity (a limit of detection of 10.84 pM), wide linear range (0.05 nM âˆ¼ 500 nM (with determination coefficient > 0.99)), and simple operation, making it suitable and convenient for STR detection. Successful STR determination in genuine honey samples was demonstrated.

Simultaneous detection of AFB1 and aflD gene by "Y" shaped aptamer fluorescent biosensor based on double quantum dots.

The developed method for simultaneous detection of aflatoxin B1 (AFB1) and aflD genes can effectively monitor from the source and reduce the safety problems and economic losses caused by the production of aflatoxin, which can be of great significance for food safety regulations. In this paper, we constructed a sensitive and convenient fluorescent biosensor to detect AFB1 and aflD genes simultaneously based on fluorescence resonance energy transfer (FRET) between quantum dots (QDs) and a black hole quenching agent. A stable "Y" shaped aptasensor was employed as the detection platform and a double quantum dot labeled DNA fragment was utilized to be the sensing element in this work. When the targets of AFB1 and aflD genes were presented in the solution, the aptamer in the "Y" shaped probe is specifically recognized by the target. At this time, both Si-carbon quantum dots (Si-CDs) and CdTe QDs are far away from the BHQ1 and BHQ3 to recover the fluorescence. The linear range of the prepared fluorescence simultaneous detection method was as wide as 0.5-500 ng·mL-1 with detection lines of 0.64 ng·mL-1 for AFB1 and 0.5-500 nM with detection lines of 0.75 nM for aflD genes (3σ/k). This fabricated fluorescent biosensor was further validated in real rice flour and corn flour samples, which also achieved good results. The recoveries were calculated by comparing the known and found amounts of AFB1 which ranged from 88.4 to approximately 115.32% in the rice flour samples and 90.7 ~ 102.58% in the corn flour samples. The recoveries of aflD genes ranged from 84.32 to approximately 109.3% in the rice flour samples and 89.48 ~ 100.99% in the corn flour samples. Therefore, the proposed biosensor can significantly improve food safety and quality control through a simple, fast, and sensitive agricultural product monitoring and detection system.

Concentrations, Number of Doses, and Formulations of Aluminium Adjuvants in Vaccines: A Systematic Review with Meta-Analysis and Trial Sequential Analysis of Randomized Clinical Trials.

Aluminium adjuvants are commonly used in vaccines to boost the effects of vaccination. Here, we assessed the benefits and harms of different aluminium adjuvants vs. other aluminium adjuvants or vs. the same aluminium adjuvant at other concentrations, administered a different number of doses, or at different particle sizes used in vaccines or vaccine excipients. We conducted a systematic review with meta-analysis and Trial Sequential Analysis to assess the certainty of evidence with Grading of Recommendations Assessment, Development and Evaluation (GRADE). We obtained data from major medical databases until 20 January 2023 and included 10 randomized clinical trials of healthy volunteers. The comparisons assessed higher vs. lower aluminium adjuvant concentrations; higher vs. lower number of doses of aluminium adjuvant; and aluminium phosphate adjuvant vs. aluminium hydroxide adjuvant. For all three comparisons, meta-analyses showed no evidence of a difference on all-cause mortality, serious adverse events, and adverse events considered non-serious. The certainty of evidence was low to very low. None of the included trials reported on quality of life or proportion of participants who developed the disease being vaccinated against. The benefits and harms of different types of aluminium adjuvants, different aluminium concentrations, different number of doses, or different particle sizes, therefore, remain uncertain.

Three-dimensional ordered DNA network constructed by a biomarker pair for accurate monitoring of colorectal cancer.

Precise and early screening of colorectal cancer (CRC) is one crucial yet challenging task for its treatment, and the analysis of multi-targets of CRC in a single assay with high accuracy is essential for pathological research and clinical diagnosis. Here, a CRC-related biomarker pair, microRNA-211 (miRNA-211) and H2S, was detected by constructing a three-dimensional (3D) ordered DNA network. First, trace amount of miRNA-211 could initiate a hybridization chain reaction-based amplification process. A highly ordered 3D DNA network was formed based on the organized assembly of DNA-cube frameworks that were constructed by DNA origamis and Ag nanoparticles (NPs) encapsulated inside. In the presence of the H2S, Ag NPs within the network can be etched to generate Ag2S quantum dots, which could be better visualized in fluorescence in situ cell imaging. Using the 3D DNA ordered network as the sensing platform, it can acquire dual analysis of biomolecule (miRNA-211) and inorganic gas (H2S) in vitro, overcoming the limitations of single type of biomarker detection in a single assay. This assay achieved a wide linearity range of H2S from 0.05 to 10 µM, and exhibited a low limit of detection of 4.78 nM. This strategy allows us to acquire the spatial distributions of H2S and miRNA expression levels in living CRC cells simultaneously, providing a highly sensitive and selective tool for early screening and monitoring of CRC.

Magnetic three-phase single-drop microextraction for highly sensitive detection of aflatoxin B1 in agricultural product samples based on peroxidase-like spatial network structure.

In this work, a highly sensitive method for aflatoxin B1 (AFB1) detection was developed based on a peroxidase-like spatial network structure. The specific antibody and antigen of AFB1 were coated on a histidine-modified Fe3O4 nanozyme to form the capture/detection probes. Based on the competition/affinity effect, the spatial network structure was constructed by the probes, which could be rapidly (8 s) separated by a magnetic three-phase single-drop microextraction process. In this single-drop microreactor, the network structure was applied to catalyze a colorimetric 3,3',5,5'-tetramethylbenzidine oxidation reaction for AFB1 detection. The signal was amplified significantly due to the strong peroxidase-like ability of the spatial network structure and the enrichment effect of the microextraction. Thus, a low detection limit (0.034 pg/mL) was achieved. The matrix effect of real sample can be eliminated by the extraction approach, and the practicability of this method was proved by agricultural product samples analysis.

[Detection of four biogenic amines by liquid chromatography based on aptamer signal replacement combined with cyclic amplification].

Biogenic amines (BAs) represent a class of potentially harmful substances in foods and medicines. Their content is thus an important indicator of proper hygiene in food preparation, and purity of medicines. It is of great practical significance to establish accurate and sensitive detection of BAs in food and drugs. In this study, a high performance liquid chromatography (HPLC) method was developed for the simultaneous detection of multiple BAs in fish, pork and antibiotics based on aptamer signal replacement and cyclic amplification strategy. First, non-fluorescent targets were converted into fluorescent nucleic acid probes using a two-step replacement process. Subsequently, a large number of nucleic acid probes with different lengths and base sequences were generated using a double-stranded specific nuclease-assisted signal amplification strategy. Finally, various BAs in real samples were accurately identified using an HPLC platform. The influence of base sequence and nucleic acid probe length on separation via HPLC was studied to improve discrimination among fluorescent signals. Four different sequences were selected as tails to the DNA probe, and their retention times increased in turn. Experimental conditions, including column temperature, flow rate, gradient elution process, reaction temperature, and incubation time, were optimized by orthogonal experiments to further improve signal separation efficiency. Specifically, the methanol gradient was changed from 10% to 20% during 0-20 min, 35 ℃ of column temperature and 1.0 mL/min of flow rate were chosen as the HPLC conditions. The final resolution of chromatographic peaks was 3.44, 3.59 and 2.37, indicating complete separation between peaks. Optimal incubation time for BA capture by aptamer was 120 min, and optimal dosage of duplex specific nuclease (DSN) and Mg2+were 0.9 U and 30 mmol/L. The optimal pH, incubation temperature, and DSN incubation time were 7.0, 40 ℃ and 210 min, respectively. The proposed method exhibited high sensitivity towards BAs, with a linear range of 1 pmol/L-1 µmol/L, and the limits of detection of tyramine, histamine, spermine, and tryptamine were 0.25, 0.21, 0.27 and 0.19 pmol/L, respectively. The feasibility of this method was verified, and contrast experiments indicated that it could achieve highly selective detection of four BAs in one run. The applicability of this integrated method was also investigated for the detection of real samples (gentamycin sulfate, fish and pork). To assess the matrix effect, each BA with different concentrations were spiked into real fish and pork samples. Relative recoveries and relative standard deviations (RSDs) ranged from 101.2% to 104.5% and from 1.5% to 4.3%, respectively. The above detection results for real samples showed that this method could accurately capture, separate, and identify BAs in complex matrix samples. This strategy can effectively improve analyte selectivity and reduce the matrix effect. This assay is thus expected to provide a new approach for food and drug analyses.

Multiply-amplified strategy for the ultrasensitive detection of kanamycin via aptamer-triggered three-dimensional G-quadruplex/Ni-Fe layered double oxide frame networks.

In this work, a multiply-amplified peroxidase-like colorimetric strategy was proposed for the high-specific recognition and ultrasensitive detection of kanamycin (Kana). Based on two Kana-aptamer triggered sequential reactions, G-quadruplex (G4) and DNA (hairpins) modified Ni-Fe layered double oxides (LDOs) could be obtained simultaneously. Later, a three-dimensional G4/LDO frame networks, as a novel DNAzyme, with enhanced peroxidase-like catalytic activity was assembled through electrostatic interaction. This DNAzyme catalyzed 3,3',5,5'-tetramethylbenzidine oxidation for the colorimetric detection of Kana. The enhancement principle was discussed and the charge transfer process during the catalytic reaction was investigated. Under the optimal experiment conditions, the proposed method exhibited high sensitivity, where the linear range is from 10 fM to 10 nM (r2 = 0.992), and the limit of detection is 3 fM (S/N = 3). The practicability of this assay was demonstrated by successfully application of residual Kana detection in genuine milk and urine samples.

Logarithmic Data Processing Can Be Used Justifiably in the Plotting of a Calibration Curve.

The article is a response to a recent opinion piece that log concentration values should not be applied in analytical chemistry. An essential aim in the development of analytical chemistry methods is to obtain more sensitive and accurate detection values. For the application of chemical analysis methods, the obtained experiment data need to fit with the mathematical functions in the first place. As influenced by different detection principles and analytical methods, data can be displayed in a coordinate system with two linear axes for linear function fitting, or the data can first be taken through a logarithmic transformation and then for function fitting. Using raw data or data after logarithmic transformation primarily depends on analytical principles, without special rules of data formats. For example, ultraviolet-visible spectrophotometric data are more suitable for direct linear fitting. However, enzyme-catalyzed reaction or electrochemical data in logarithmic form are more appropriate for function fitting. This transformation of data form will not affect the soundness of fit statistics; rather, it simplifies the complexity of function analysis and calculation, which are the essence of analytical chemistry. In this brief article, we provide justification and legitimacy of the application of logarithmic processing in various fields of quantitative analytical chemistry.

Gold nanoprism/Tollens' reagent complex as plasmonic sensor in headspace single-drop microextraction for colorimetric detection of formaldehyde in food samples using smartphone readout.

In this work, an assay with high sensitivity and selectivity for the detection of formaldehyde (FA) is presented. The assay applied a gold nanoprism/Tollens' reagent (Au-np/TR) complex as the sensor used in headspace single-drop microextraction (HS-SDME). A surface plasmon resonance signal enhancement as well as color change was caused by the formation of Au@Ag-np after a redox reaction between FA and TR during the HS-SDME process. With the utilization of smartphone nanocolorimetry (SNC), the FA could be detected and quantified. For HS-SDME-SNC, a linearity calibration curve ranging from 0.1 to 100 µM was obtained, and the limit of detection was determined to be 30 nM. Successful attempts to determine FA were demonstrated by analysis of the analyte in (adulterated) raw food samples (octopus and chicken flesh). Matrix effects from real samples were avoided by using HS-SDME, and only a 3-µL droplet of solvent was needed in the assay.

Magnetic Three-Phase Single-Drop Microextraction for Rapid Amplification of the Signals of DNA and MicroRNA Analysis.

The detection of nucleic acids usually suffers from a lengthy amplification process. To obtain an enhanced signal within several seconds, a magnetic three-phase single-drop microextraction (MTP-SDME) approach was developed for the quantification of nucleic acids. First, a target-triggered recycling amplification strategy was used to constitute magnetic branched DNA/Fe3O4 networks, which displayed peroxidase-like catalytic activity toward the 3,3',5,5'-tetramethylbenzidine colorimetric reaction. The networks were separated and enriched by rapid (6 s) MTP-SDME (with only 6 µL of solvent required), thereby producing highly sensitive signals for the quantification of nucleic acids. The signals were significantly amplified by the triple strategy (network formation, MTP-SDME, and catalytic reaction). The application of magnetic extraction minimized the background signal, avoided sample matrix effects, and enhanced the analyte signals. This assay achieved linear calibration curves of between 0.5 aM and 1 pM for microRNA-122 (miRNA-122) and between 1 aM and 1 pM for HBV-T (a DNA fragment from hepatitis B virus). Limits of detection of 0.15 aM for miRNA-122 and 0.34 aM for HBV-T were attained, with relative standard deviations of <5.0% (n = 3). Furthermore, the procedure was applied to determine miRNA-122 and HBV-T in genuine serum samples from hepatocellular carcinoma patients.

Direct immersion single-drop microextraction of semi-volatile organic compounds in environmental samples: A review.

Single-drop microextraction (SDME) techniques are efficient approaches to pretreatment of aqueous samples. The main advantage of SDME lies in the miniaturization of the solvent extraction process, minimizing the hazards associated with the use of toxic organic solvents. Thus, SDME techniques are cost-effective, and represent less harm to the environment, subscribing to green analytical chemistry principles. In practice, two main approaches can be used to perform SDME - direct immersion (DI)-SDME and headspace (HS)-SDME. Even though the DI-SDME has been shown to be quite effective for extraction and enrichment of various organic compounds, applications of DI-SDME are normally more suitable for moderately polar and non-polar semi-volatile organic compounds (SVOCs) using organic solvents which are immiscible with water. In this review, we present a historical overview and current advances in DI-SDME, including the common analytical tools which are usually coupled with DI-SDME. The review also focuses on applications concerning SVOCs in environmental samples. Currents trends in DI-SDME and possible future direction of the procedure are discussed.

Highly Sensitive Detection of Multiple MicroRNAs by High-Performance Liquid Chromatography Coupled with Long and Short Probe-Based Recycling Amplification.

This report demonstrated the utility of high-performance liquid chromatography (HPLC)-fluorescence detection for selective separation and sensitive quantification of multiple microRNAs (miRNAs). A duplex specific nuclease (DSN)-assisted target recycling amplification strategy was developed to enhance the signals of miRNAs, which alleviates the low sensitivity of conventional HPLC to nucleic acids. To separate the signals of different miRNAs, DNA probes with different lengths and base sequences were immobilized on magnetic beads. The application of an effective magnetic separation minimized the background signal and extended the dynamic range. This assay achieved a limit of detection of 0.39 fM for miRNA-122, 0.30 fM for miRNA-155, and 0.26 fM for miRNA-21, respectively. The proposed assay was successfully applied to detect simultaneously miRNA-122, miRNA-155, and miRNA-21 in serum samples from healthy persons and cervical cancer patients, and the results were then compared with those of quantitative real-time-polymerase chain reaction amplification.

Recent advances in the application of layered double hydroxides in analytical chemistry: A review.

In recent years, layered double hydroxides (LDHs) have garnered a lot of attention in analytical chemistry, due to their advantages such as relatively simple synthesis, low cost, possession of large specific surface area and high catalytic activity, and biocompatibility. The most common applications of LDH in analytical chemistry such as sorbents in sample extraction, electrode materials in electrochemical sensing and color indicators in colorimetric detection have been well reported. Generally, the LDHs are prepared as composites with nanomaterials, or constructed with specific three-dimensional structures, befitting the applications desired for them. However, the applications of LDHs (as extraction sorbents, color indicators and in electrochemical sensing) are usually limited in these scenarios. To help address these challenges, future trends and developmental prospects of LDHs materials in analytical chemistry are discussed in this article. Besides, the strategies associated with the design of LDHs, including the structural aspects, for potential analytical applications are presented and reviewed.

Error Matrix Tool to Overview the Validity of Evidence on Radix Sophorae flavescentis for Chronic Hepatitis B.

Objectives: To introduce a conceptualized visual error matrix tool to overview the validity of evidence by taking Radix Sophorae flavescentis for chronic hepatitis B as an example and to propose recommendations for improving clinical trial design and evidence quality. Methods: The randomized clinical trials and reviews were collected during the conduct of a Cochrane systematic review. The authors used a visual error matrix tool to overview the evidence validity by looking at systematic, random, and design error risks. Systematic errors were measured by the type of evidence. Random errors were expressed by the standard error (SE). Design errors were assessed on the priority of outcome measures and the adequacy of nine design components. Three-dimensional error matrix on benefits and harms were then constructed. Results: The authors included 6 meta-analyses and 28 randomized clinical trials. In terms of systematic errors, all reviews were at critically low quality, and all included randomized trials were assessed at high risk of bias. On this systematic error level, they found that there was substantial risk of random errors regarding all-cause mortality (SE 0.36), moderate risk regarding serious adverse events (SE 0.22), substantial risk regarding nonserious adverse events (SE 0.35), and small to moderate risk regarding surrogate outcomes such as detectable hepatitis B e-antigen (HBeAg) and detectable hepatitis B virus (HBV)-DNA (SE 0.16 and 0.21). No study reported results on quality of life, hepatitis B-related mortality, and morbidity. The design error risks were mainly misuse of outcomes (14/34), inadequate selection of participants (5/34), inadequate description of intervention (11/34) and control (9/34), single-center setting (33/34), and unclear study objective regarding superiority, equivalence, or noninferiority. Conclusion: The current evidence on Radix S. flavescentis for chronic hepatitis B showed high risks of systematic errors, moderate or high risks of random errors, and high risks of design errors. These findings suggest that more randomized trials at minimum risks of all three errors are needed to assess the benefits and harms of Radix S. flavescentis for chronic hepatitis B. The visual error matrix tool provides an overview of the reliability of evidence and may assist in design and conduct of future randomized trials.

Ultrasensitive and eco-friendly immunoassays based monoclonal antibody for detection of deoxynivalenol in cereal and feed samples.

Ultrasensitive immunoassays, including an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and a lateral-flow immunochromatographic assay (ICA), were developed based on a monoclonal antibody for the analysis of deoxynivalenol in food and feed samples. With 0.01 M PBS, 20% ethanol-PBS, and 60% ethanol-PBS extraction, which are environmentally safe, the 50% inhibitory concentration (IC50) and limit of detection (LOD) values were 1.83-4.68 µg/kg and 0.241-0.664 µg/kg, respectively, with recovery rates of 87.7%-137% and coefficient variation values of 3.99-9.88% (intra-assay) and 4.17-9.81% (inter-assay) for the ic-ELISA relative to the results obtained by liquid chromatography-tandem mass spectrometry (LC-MS). For the ICA strip, the visual LODs were 10-150 µg/kg, the cut-off values were 50-750 µg/kg, and the calculated LODs were 1.97-46.8 µg/kg, with different sample extraction solutions, and the recovery rates were 66.7%-127%. These methods are sensitive, simple and safe, providing an auxiliary analytical tool for screening the massive samples in markets.

Phase retrieval for attacking fractional Fourier transform encryption.

An advanced iterative phase retrieval algorithm is applied to perform a ciphertext-only attack on the fractional Fourier transform-based double random phase encryption system. With the given complex amplitude of ciphertext and definite support of the object image, the original object image can be recovered by estimating the energy of support area in the recovered image. The encryption system can be attacked by analyzing the sensibility of fractional Fourier transform order keys and evaluating the energy of the object image support area. The proposed algorithm can obtain encrypted fractional order and retrieve two random phase keys. Numerical results demonstrate the efficacy of the proposed attacking method.

High-sensitivity immunochromatographic assay for fumonisin B1 based on indirect antibody labeling.

OBJECTIVE: To develop a high-sensitivity immunochromatographic test for fumonisin B1 in plant extracts. RESULTS: Unlike conventional immunochromatographic tests, this assay is performed in two stages: competitive reaction with free specific antibodies and identifying immune complexes by their interaction with the anti-species antibody-conjugated gold nanoparticles. The use of a new geometry for the test strip membranes and a novel reagent application method ensures the proper order of these stages without additional manipulations. The contact of the ready-to-use test strip with the liquid sample suffices in initiating all stages of the assay and obtaining test results. The developed test was used on corn extracts; its instrumental limit of fumonisin B1 detection was 0.6 ng ml-1 at 15 min of assay duration. CONCLUSIONS: The proposed approach is flexible and can be used for a wide range of low molecular compounds. The use of anti-species antibody-conjugated gold nanoparticles in immunochromatography significantly facilitates the development of test systems by eliminating the need to synthesize and characterize the conjugates with specific antibodies for each new compound to be detected.

Three-dimensional scene encryption and display based on computer-generated holograms.

An optical encryption and display method for a three-dimensional (3D) scene is proposed based on computer-generated holograms (CGHs) using a single phase-only spatial light modulator. The 3D scene is encoded as one complex Fourier CGH. The Fourier CGH is then decomposed into two phase-only CGHs with random distributions by the vector stochastic decomposition algorithm. Two CGHs are interleaved as one final phase-only CGH for optical encryption and reconstruction. The proposed method can support high-level nonlinear optical 3D scene security and complex amplitude modulation of the optical field. The exclusive phase key offers strong resistances of decryption attacks. Experimental results demonstrate the validity of the novel method.