WITHDRAWN: A preliminary assessment on spatial prioritization for integrated urban flood management based on source tracking method.

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UiOL@AIEgens-assisted lateral flow immunosensor for the ultrasensitive dual-modal point-of-care detection of aflatoxin B1.

Aflatoxin B1 (AFB1) contamination in food has attracted worldwide attention. The sensitive detection of AFB1 is vital for ensuring food quality and safety. This study developed an ultrasensitive signal-enhanced lateral flow immunosensor (LFIS) based on the functionalized zirconium metal-organic framework (MOF) of a UiO linker enriched with abundant aggregation-induced emission luminogen (UiOL@AIEgens) probes for the rapid dual-modal point-of-care (POC) determination of AFB1. Using UiO MOFs with numerous active sites as the carrier facilitated abundant AIEgens enrichment on the surface. After coupling with enough anti-AFB1 monoclonal antibodies (mAbs), the green-emissive UiOL@AIEgens-mAbs probes with high specificity and remarkably-enhanced fluorescence responses were obtained to competitively capture target AFB1 in the standard or sample solution and AFB1 antigen immobilized on the test (T) line of the POC LFIS. Under optimum conditions, the LFIS was capable of visual qualitative and smartphone-assisted dual-modal determination of target AFB1 within 7 min. Detection occurred in a range of 0.01-5 ng/mL at an ultra-low detection limit of 0.003 ng/mL, which was 300- and 600-fold lower than traditional immunoassays and the maximum limit set by the European Union, respectively. Moreover, the feasibility and robustness of the LFIS platform were assessed by detecting AFB1 in maize and lotus seed samples with average recoveries of 94.3-109.0%. The developed UiOL@AIEgens-based POC LFIS can be used for ultrasensitive, reliable, on-site detection in food. This study provides a new method for the real-time monitoring of AFB1 and other harmful contaminants in food and more complex matrices.

3D nanocake-like Au-MXene/Au pallet structure-based label-free electrochemical aptasensor for paraquat determination.

3D nanocake-like Au-MXene and Au pallet (Au-MXene/AuP) nanocomposite-modified screen-printed carbon electrodes (SPCEs) were utilized to construct an ultrasensitive label-free electrochemical aptasensor through a self-assembly procedure for trace paraquat (PQ) residue detection. Benefiting from the excellent electrochemical (EC) performances (e.g., high conductivity and large surface area) of Au-MXene nanocomposites and AuP substrate, the developed Apt/Au-MXene/AuP/SPCE-based EC aptasensor displayed excellent specificity and anti-interference ability, good repeatability, and stability. A linear relationship between the log value of the change in current intensity [lg (ΔI)] and the log value of the concentration of PQ [lg (CPQ)] was obtained in the range 0.05-1000 ng/mL. The limit of detection was 0.028 ng/mL, and the sensitivity was 255.5 µA/(µM·cm2). Practical applications in malt and mint samples confirmed the accuracy of the EC aptasensor in complex matrices for PQ detection, providing a universal analytical tool for other trace pesticides in different food samples by simply replacing the corresponding aptamers.

Development of a Nafion-MWCNTs and in-situ generated Au nanopopcorns dual-amplification electrochemical aptasensor for ultrasensitive detection of OTA.

Trace detection of ochratoxin A (OTA) in foods is essential to mitigate risks to human health. Herein, a label-free electrochemical (EC) aptasensor based on dual-signal amplification of Nafion dispersed multi-walled carbon nanotubes (Nafion-MWCNTs) and Au nanopopcorns was developed for ultrasensitive detection of OTA. Nafion solution prevented the leaching of MWCNTs, and the Nafion-MWCNTs modified screen-printed carbon electrode (SPCE) acted as the sensing substrate which facilitated the uniform distribution of the electrodeposited Au nanopopcorns. The in-situ generated Au nanopopcorns could not only load a large amount of aptamers for specific identification of OTA, but also promote the electron transfer of the sensing platform. The incorporation of Nafion-MWCNTs and Au nanopopcorns realized dual-amplification of the aptasensor due to the enhanced conductivity and the increased electroactive surface area of the electrode. The modified electrodes were characterized through scanning electron microscopy, X-ray photoelectron spectroscopy and EC evaluation. Under optimal conditions, the electrochemical impedance spectroscopy (EIS) was measured for the determination of OTA. The as-fabricated Au nanopopcorns/Nafion-MWCNTs impedimetric aptasensor displayed excellent sensitivity with a detection limit as low as 1 pg/mL and a wide linear range of 1 pg/mL-10 ng/mL for OTA. Practical application of the aptasensor in the spiked malt samples achieved satisfactory recoveries of 89.82-95.65 %, which was also successfully verified to detect OTA in eleven batches of actual malt samples collected from the local market. The creative aptasensor is simple, cost-effective, sensitive, and accurate, showing great promise for on-site monitoring of other trace contaminants in foods by simply replacing the aptamers.

Human genome-specific real-time PCR method for sensitive detection and reproducible quantitation of human cells in mice.

Xenotransplantation of human cells into immunodeficiency mice has been frequently used to study stem cells in tissue repair and regeneration and cancer cell metastasis. However, a sensitive and reproducible method to quantify cell engraftment lacks. Here, we developed a Real-Time PCR-based method which facilitated consistent detection and quantification of small amounts of human cells distributed in mouse organs after infusion. The principle of the method was to directly detect a humans-specific sequence in the human-murine genomic DNA mixture. In a mouse myocardial infarction model, the Real-Time PCR-based method consistently determined the amounts of human mesenchymal stem cells (hMSCs) engrafted into the heart and other organs 7 days after infusion of as little as 2.5 × 10(5) cells, indicating a high sensitivity, and the amounts of hMSCs detected in mice highly correlated to the numbers of hMSCs transplanted. Importantly, different from previous PCR-based methods, our method produced highly consistent and reproducible results. The reliability of the method was further proven by parallel analyses of DiI-labeled hMSCs in tissue sections and in single cell suspensions of mice. Our data show that the present human genomic DNA-specific primers-based Real-Time PCR method is sensitive and highly reproducible in determining the amount of xenotransplanted human cells in murine tissues.

Epigenetic dysregulation in mesenchymal stem cell aging and spontaneous differentiation.

BACKGROUND: Mesenchymal stem cells (MSCs) hold great promise for the treatment of difficult diseases. As MSCs represent a rare cell population, ex vivo expansion of MSCs is indispensable to obtain sufficient amounts of cells for therapies and tissue engineering. However, spontaneous differentiation and aging of MSCs occur during expansion and the molecular mechanisms involved have been poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: Human MSCs in early and late passages were examined for their expression of genes involved in osteogenesis to determine their spontaneous differentiation towards osteoblasts in vitro, and of genes involved in self-renewal and proliferation for multipotent differentiation potential. In parallel, promoter DNA methylation and hostone H3 acetylation levels were determined. We found that MSCs underwent aging and spontaneous osteogenic differentiation upon regular culture expansion, with progressive downregulation of TERT and upregulation of osteogenic genes such as Runx2 and ALP. Meanwhile, the expression of genes associated with stem cell self-renewal such as Oct4 and Sox2 declined markedly. Notably, the altered expression of these genes were closely associated with epigenetic dysregulation of histone H3 acetylation in K9 and K14, but not with methylation of CpG islands in the promoter regions of most of these genes. bFGF promoted MSC proliferation and suppressed its spontaneous osteogenic differentiation, with corresponding changes in histone H3 acetylation in TERT, Oct4, Sox2, Runx2 and ALP genes. CONCLUSIONS/SIGNIFICANCE: Our results indicate that histone H3 acetylation, which can be modulated by extrinsic signals, plays a key role in regulating MSC aging and differentiation.